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Main
Date: 02 Sep 2007 12:24:38
From: Just A User
Subject: Yet another broken spoke
|
It happened again! I broke ANOTHER spoke on my road bike. This makes the
second break in a month maybe a month and a half. Now I know I don't
have the lightest riding style compared to some riders. And I am not the
lightest of all riders. But then again I am riding on 32 triple cross
wheels. What I don't understand is why am I breaking them on the front
wheel only? I thought the back wheel carried more weight. So I have a
few extra spokes I bought when I had the wheel at the lbs for the last
spoke replacement. But now I am thinking that a new / better machine
built wheel, or cough, a handbuilt wheels might be a more reliable way
to go. When I say handbuilt, I mean with my hands, that have no
experience building wheels. All opinions welcome.
J.A.U.
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Date: 12 Sep 2007 10:40:22
From:
Subject: Re: Yet another broken spoke
|
On Sep 12, 7:29 pm, jobst.bra...@stanfordalumni.org wrote:
> Hjulcompaniet? writes:
> >>>>> The spokes lose huge amounts of pre-tension as they roll under
> >>>>> the wheel. The individual the spokes all the way around the
> >>>>> wheel show an increase of only up to 10% in tension, compared to
> >>>>> the spoke directly under the axle's loss of tension.
> >>>> Right. Under what criteria is a 10% increase in tension
> >>>> insignificant, as it was described by Brandt? And in your
> >>>> testing, as well as everyone else's, the greatest loss of tension
> >>>> was in the spokes perpendicular to the spokes that lost tension.
> >>>> The loss of tension caused by the local flexing of the rim cannot
> >>>> be balanced by a rise in tension by the rest of the spokes; OTOH,
> >>>> the flexing of the rim caused by the ovalization of the hoop
> >>>> _must_ be offset by a rise in tension by the rest of the spokes.
> >>> The hoop does not "ovalize" in normal use, the use for which it is
> >>> intended; to wit: transmitting a compressive load between the
> >>> contact patch and the axle. The shape of the distortion of a rim
> >>> under load is lumpy.
> >>> On a thirty six spoke wheel the greatest change in spoke length is
> >>> at the contact patch where it is -0.153 mm. The next local
> >>> maximum of absolute spoke length change is four spokes from the
> >>> contact patch, or one ninth of the circumference where the change
> >>> is 0.014 mm. After that all the spokes are extended by 0.007 mm.
> >>> The rim remains circular, except for an indentation at the contact
> >>> patch and a couple lumps adjacent to the contact patch.
> >> To put it a different way, the rim is flattened at the road contact
> >> area and this flattening increases the radius of the remaining
> >> circular part of the rim (the previous arc having a shorter linear
> >> length than when flattened. Of course you can read about this in
> >> "the Bicycle Wheel" which is what inspired Ian and Henry Gavin to
> >> publish the same material in their own fora.
>
> http://www.avocet.com/wheelbook/wheelbook.html
>
>
>
>
>
> >>>> The latter effect is where the wheel gets its strength; it is
> >>>> ridiculous to suggest that the rise in tension of the other
> >>>> spokes is insignificant because without that rise in tension you
> >>>> might as well be riding a wheel with all the spokes detensioned
> >>>> to the point that all the wheel strength derives completely from
> >>>> the strength of the rim alone. To say that the rise in tension
> >>>> of the other spokes is insignificant is just utterly ridiculous.
> >> If you research the many times this subject has appeared in this
> >> forum, you'll find that the vertical component of tension
> >> increases, caused by spreading the wheel circumference, sum to
> >> zero, leaving only the reduction in downward force of the spokes in
> >> the "load affected zone" as the sole support of axle loads. The
> >> reason this is so, is that at either end of the load affected zone,
> >> a bulge caused by rim stiffness in the transition from the
> >> flattened area to the circular part does not allow a sudden
> >> transition. This may slightly differ depending on the bending
> >> stiffness of the rim cross section used as a model. The ones in
> >> the book are MA-2's.
> > Does this sentance make more sence?
> > "In the situation of a wheel with spokes of even tension being
> > statically loaded, spokes under the the horizontal centerline of the
> > hub come under relatively less tension than those on or above the
> > centerline of the hub, with the spokes experiencing the greatest
> > amount of change being those closest to the vertical plane, with a
> > load spread relative to rim stiffness number of spokes, and spoke
> > type"
>
> If you read the above, you can deduce that the quote does not make
> sense. If still in doubt, get a copy of the book and read more about
> it.
>
> Jobst Brandt- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -
I think you've muddled together two posters there..
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Date: 12 Sep 2007 10:24:53
From:
Subject: Re: Yet another broken spoke
|
On Sep 12, 5:46 pm, Ted Bennett <tedbenn...@earthlink.net > wrote:
> hjulcompan...@gmail.com wrote:
> > Does this sentance make more sence?
>
> No, that sentence does not make more sense.
>
> --
> Ted Bennett
My sentance strucutre is not great, and I can't quite find the right
words, but I feel Im pretty close.
I think Brant and others have made a mistake in pin pointing the lower
2 or 3 spokes as bearing the load on bicycle wheels. This is simply
not the case. It may be the case in some wheels, due to material
properties. Rim stiffness now plays a major role in how the load is
spread in a wheel. The subjective example that all this is based on is
just not good enough to come to a broad sweeping conclusion for all
spoked bicycle wheels.
Does that make any sence?
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Date: 12 Sep 2007 04:36:50
From:
Subject: Re: Yet another broken spoke
|
On Sep 7, 9:13 pm, jobst.bra...@stanfordalumni.org wrote:
> Michael Press writes:
> >>> The spokes lose huge amounts of pre-tension as they roll under the
> >>> wheel. The individual the spokes all the way around the wheel show
> >>> an increase of only up to 10% in tension, compared to the spoke
> >>> directly under the axle's loss of tension.
> >> Right. Under what criteria is a 10% increase in tension
> >> insignificant, as it was described by Brandt? And in your testing,
> >> as well as everyone else's, the greatest loss of tension was in the
> >> spokes perpendicular to the spokes that lost tension.
> >> The loss of tension caused by the local flexing of the rim cannot
> >> be balanced by a rise in tension by the rest of the spokes; OTOH,
> >> the flexing of the rim caused by the ovalization of the hoop _must_
> >> be offset by a rise in tension by the rest of the spokes.
> > The hoop does not "ovalize" in normal use, the use for which it is
> > intended; to wit: transmitting a compressive load between the
> > contact patch and the axle. The shape of the distortion of a rim
> > under load is lumpy.
> > On a thirty six spoke wheel the greatest change in spoke length is
> > at the contact patch where it is -0.153 mm. The next local maximum
> > of absolute spoke length change is four spokes from the contact
> > patch, or one ninth of the circumference where the change is 0.014
> > mm. After that all the spokes are extended by 0.007 mm. The rim
> > remains circular, except for an indentation at the contact patch and
> > a couple lumps adjacent to the contact patch.
>
> To put it a different way, the rim is flattened at the road contact
> area and this flattening increases the radius of the remaining
> circular part of the rim (the previous arc having a shorter linear
> length than when flattened. Of course you can read about this in "the
> Bicycle Wheel" which is what inspired Ian and Henry Gavin to publish
> the same material in their own fora.
>
> http://www.avocet.com/wheelbook/wheelbook.html
>
> >> The latter effect is where the wheel gets its strength; it is
> >> ridiculous to suggest that the rise in tension of the other spokes
> >> is insignificant because without that rise in tension you might as
> >> well be riding a wheel with all the spokes detensioned to the point
> >> that all the wheel strength derives completely from the strength of
> >> the rim alone. To say that the rise in tension of the other spokes
> >> is insignificant is just utterly ridiculous.
>
> If you research the many times this subject has appeared in this
> forum, you'll find that the vertical component of tension increases,
> caused by spreading the wheel circumference, sum to zero, leaving only
> the reduction in downward force of the spokes in the "load affected
> zone" as the sole support of axle loads. The reason this is so, is
> that at either end of the load affected zone, a bulge caused by rim
> stiffness in the transition from the flattened area to the circular
> part does not allow a sudden transition. This may slightly differ
> depending on the bending stiffness of the rim cross section used as a
> model. The ones in the book are MA-2's.
>
> Jobst Brandt- Hide quoted text -
>
> - Show quoted text -
Does this sentance make more sence?
"In the situation of a wheel with spokes of even tension being
statically loaded, spokes under the the horizontal centerline of the
hub come under relatively less tension than those on or above the
centerline of the hub, with the spokes experiencing the greatest
amount of change being those closest to the vertical plane, with a
load spread relative to rim stiffness number of spokes, and spoke
type"
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| | |
Date: 12 Sep 2007 17:29:24
From:
Subject: Re: Yet another broken spoke
|
Hjulcompaniet? writes:
>>>>> The spokes lose huge amounts of pre-tension as they roll under
>>>>> the wheel. The individual the spokes all the way around the
>>>>> wheel show an increase of only up to 10% in tension, compared to
>>>>> the spoke directly under the axle's loss of tension.
>>>> Right. Under what criteria is a 10% increase in tension
>>>> insignificant, as it was described by Brandt? And in your
>>>> testing, as well as everyone else's, the greatest loss of tension
>>>> was in the spokes perpendicular to the spokes that lost tension.
>>>> The loss of tension caused by the local flexing of the rim cannot
>>>> be balanced by a rise in tension by the rest of the spokes; OTOH,
>>>> the flexing of the rim caused by the ovalization of the hoop
>>>> _must_ be offset by a rise in tension by the rest of the spokes.
>>> The hoop does not "ovalize" in normal use, the use for which it is
>>> intended; to wit: transmitting a compressive load between the
>>> contact patch and the axle. The shape of the distortion of a rim
>>> under load is lumpy.
>>> On a thirty six spoke wheel the greatest change in spoke length is
>>> at the contact patch where it is -0.153 mm. The next local
>>> maximum of absolute spoke length change is four spokes from the
>>> contact patch, or one ninth of the circumference where the change
>>> is 0.014 mm. After that all the spokes are extended by 0.007 mm.
>>> The rim remains circular, except for an indentation at the contact
>>> patch and a couple lumps adjacent to the contact patch.
>> To put it a different way, the rim is flattened at the road contact
>> area and this flattening increases the radius of the remaining
>> circular part of the rim (the previous arc having a shorter linear
>> length than when flattened. Of course you can read about this in
>> "the Bicycle Wheel" which is what inspired Ian and Henry Gavin to
>> publish the same material in their own fora.
http://www.avocet.com/wheelbook/wheelbook.html
>>>> The latter effect is where the wheel gets its strength; it is
>>>> ridiculous to suggest that the rise in tension of the other
>>>> spokes is insignificant because without that rise in tension you
>>>> might as well be riding a wheel with all the spokes detensioned
>>>> to the point that all the wheel strength derives completely from
>>>> the strength of the rim alone. To say that the rise in tension
>>>> of the other spokes is insignificant is just utterly ridiculous.
>> If you research the many times this subject has appeared in this
>> forum, you'll find that the vertical component of tension
>> increases, caused by spreading the wheel circumference, sum to
>> zero, leaving only the reduction in downward force of the spokes in
>> the "load affected zone" as the sole support of axle loads. The
>> reason this is so, is that at either end of the load affected zone,
>> a bulge caused by rim stiffness in the transition from the
>> flattened area to the circular part does not allow a sudden
>> transition. This may slightly differ depending on the bending
>> stiffness of the rim cross section used as a model. The ones in
>> the book are MA-2's.
> Does this sentance make more sence?
> "In the situation of a wheel with spokes of even tension being
> statically loaded, spokes under the the horizontal centerline of the
> hub come under relatively less tension than those on or above the
> centerline of the hub, with the spokes experiencing the greatest
> amount of change being those closest to the vertical plane, with a
> load spread relative to rim stiffness number of spokes, and spoke
> type"
If you read the above, you can deduce that the quote does not make
sense. If still in doubt, get a copy of the book and read more about
it.
Jobst Brandt
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Date: 12 Sep 2007 08:46:23
From: Ted Bennett
Subject: Re: Yet another broken spoke
|
hjulcompaniet@gmail.com wrote:
> Does this sentance make more sence?
No, that sentence does not make more sense.
--
Ted Bennett
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Date: 11 Sep 2007 08:03:37
From: dgk
Subject: Re: Yet another broken spoke
|
On Sun, 02 Sep 2007 12:24:38 -0400, Just A User
<ken@up-yours-spammer.net > wrote:
>It happened again! I broke ANOTHER spoke on my road bike. This makes the
>second break in a month maybe a month and a half. Now I know I don't
>have the lightest riding style compared to some riders. And I am not the
>lightest of all riders. But then again I am riding on 32 triple cross
>wheels. What I don't understand is why am I breaking them on the front
>wheel only? I thought the back wheel carried more weight. So I have a
>few extra spokes I bought when I had the wheel at the lbs for the last
>spoke replacement. But now I am thinking that a new / better machine
>built wheel, or cough, a handbuilt wheels might be a more reliable way
>to go. When I say handbuilt, I mean with my hands, that have no
>experience building wheels. All opinions welcome.
>
>J.A.U.
Boy, this thread is really getting carried away. Anyhow, I was
breaking spokes pretty regularly on my fairly cheapo Trek 7100 (low
end hybrid). I tried tension relief by squeezing the spokes a bit.
Maybe not the right way to do it, but since I know squat about wheels,
that was how I interpreted various advice.
Mine were breaking on the rear wheel. So I called Nashbar or
Performance (I forget which) and spoke to the guy about my
bike/wheel, and I ordered a wheel for around $100 that came with
double or triple butted spokes (they thicken near the rim and axle.
That was maybe a year ago and I haven't broken a spoke since.
I still try to stress relieve them once in a while, but I sure am
happy not to be breaking spokes.
|
| | |
Date: 11 Sep 2007 10:00:19
From: Peter Cole
Subject: Re: Yet another broken spoke
|
dgk wrote:
>
> Boy, this thread is really getting carried away. Anyhow, I was
> breaking spokes pretty regularly on my fairly cheapo Trek 7100 (low
> end hybrid). I tried tension relief by squeezing the spokes a bit.
> Maybe not the right way to do it, but since I know squat about wheels,
> that was how I interpreted various advice.
Good online writeup at Sheldon Brown's site.
>
> Mine were breaking on the rear wheel. So I called Nashbar or
> Performance (I forget which) and spoke to the guy about my
> bike/wheel, and I ordered a wheel for around $100 that came with
> double or triple butted spokes (they thicken near the rim and axle.
> That was maybe a year ago and I haven't broken a spoke since.
>
> I still try to stress relieve them once in a while, but I sure am
> happy not to be breaking spokes.
You only have to do it once.
|
| | | |
Date: 12 Sep 2007 14:01:40
From: dgk
Subject: Re: Yet another broken spoke
|
On Tue, 11 Sep 2007 10:00:19 -0400, Peter Cole
<peter_cole@comcast.net > wrote:
>dgk wrote:
>
>>
>> Boy, this thread is really getting carried away. Anyhow, I was
>> breaking spokes pretty regularly on my fairly cheapo Trek 7100 (low
>> end hybrid). I tried tension relief by squeezing the spokes a bit.
>> Maybe not the right way to do it, but since I know squat about wheels,
>> that was how I interpreted various advice.
>
>Good online writeup at Sheldon Brown's site.
>
>>
>> Mine were breaking on the rear wheel. So I called Nashbar or
>> Performance (I forget which) and spoke to the guy about my
>> bike/wheel, and I ordered a wheel for around $100 that came with
>> double or triple butted spokes (they thicken near the rim and axle.
>> That was maybe a year ago and I haven't broken a spoke since.
>>
>> I still try to stress relieve them once in a while, but I sure am
>> happy not to be breaking spokes.
>
>You only have to do it once.
It's really a drag. Usually the rear wheel, so I undo the brake so it
doesn't rub and just limp along slowly.
I was getting ready to buy one of those temporary spokes, but figured
that a better wheel was a better solution. I also got slime tubes. I
know that they weigh a bit more and increase rolling resistance, but
it isn't noticable - my bike already weighs a ton with all the lights
and batteries and pack on it. I haven't had a flat since I did that,
which is certainly several months. No flats, no broken spokes. Life
doesn't get much better.
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Date: 08 Sep 2007 07:38:04
From: TomP
Subject: Re: Yet another broken spoke
|
I don't know that in your case "knowing" the reason why the spokes are
breaking is important.
They are breaking for what ever.
My philosophy is:
When the second spoke breaks in a wheel; it's time for new spokes. In other
words rebuild the wheel.
Just A User wrote:
> It happened again! I broke ANOTHER spoke on my road bike. This makes the
> second break in a month maybe a month and a half. Now I know I don't
> have the lightest riding style compared to some riders. And I am not the
> lightest of all riders. But then again I am riding on 32 triple cross
> wheels. What I don't understand is why am I breaking them on the front
> wheel only? I thought the back wheel carried more weight. So I have a
> few extra spokes I bought when I had the wheel at the lbs for the last
> spoke replacement. But now I am thinking that a new / better machine
> built wheel, or cough, a handbuilt wheels might be a more reliable way
> to go. When I say handbuilt, I mean with my hands, that have no
> experience building wheels. All opinions welcome.
>
> J.A.U.
--
Tp,
-------- __o
----- -\<. -------- __o
--- ( )/ ( ) ---- -\<.
-------------------- ( )/ ( )
-----------------------------------------
No Lawsuit Ever Fixed A Moron...
|
| |
Date: 06 Sep 2007 18:15:00
From:
Subject: Re: Yet another broken spoke
|
On Sep 4, 8:24 pm, carlfo...@comcast.net wrote:
> The spokes lose huge amounts of pre-tension as they roll under the
> wheel. The individual the spokes all the way around the wheel show an
> increase of only up to 10% in tension, compared to the spoke directly
> under the axle's loss of tension.
Right. Under what criteria is a 10% increase in tension insignificant,
as it was described by Brandt? And in your testing, as well as
everyone else's, the greatest loss of tension was in the spokes
perpendicular to the spokes that lost tension.
The loss of tension caused by the local flexing of the rim cannot be
balanced by a rise in tension by the rest of the spokes; OTOH, the
flexing of the rim caused by the ovalization of the hoop _must_ be
offset by a rise in tension by the rest of the spokes. The latter
effect is where the wheel gets its strength; it is ridiculous to
suggest that the rise in tension of the other spokes is insignificant
because without that rise in tension you might as well be riding a
wheel with all the spokes detensioned to the point that all the wheel
strength derives completely from the strength of the rim alone. To say
that the rise in tension of the other spokes is insignificant is just
utterly ridiculous.
|
| | |
Date: 07 Sep 2007 10:48:03
From: Michael Press
Subject: Re: Yet another broken spoke
|
In article
<1189127700.139968.248200@r29g2000hsg.googlegroups.com >
,
SocSecTrainWreck@earthlink.net wrote:
> On Sep 4, 8:24 pm, carlfo...@comcast.net wrote:
>
> > The spokes lose huge amounts of pre-tension as they roll under the
> > wheel. The individual the spokes all the way around the wheel show an
> > increase of only up to 10% in tension, compared to the spoke directly
> > under the axle's loss of tension.
>
> Right. Under what criteria is a 10% increase in tension insignificant,
> as it was described by Brandt? And in your testing, as well as
> everyone else's, the greatest loss of tension was in the spokes
> perpendicular to the spokes that lost tension.
>
> The loss of tension caused by the local flexing of the rim cannot be
> balanced by a rise in tension by the rest of the spokes; OTOH, the
> flexing of the rim caused by the ovalization of the hoop _must_ be
> offset by a rise in tension by the rest of the spokes.
The hoop does not "ovalize" in normal use, the use for
which it is intended; to wit: transmitting a
compressive load between the contact patch and the
axle. The shape of the distortion of a rim under load
is lumpy.
On a thirty six spoke wheel the greatest change in
spoke length is at the contact patch where it is
-0.153 mm. The next local maximum of absolute spoke
length change is four spokes from the contact patch, or
one ninth of the circumference where the change is
0.014 mm. After that all the spokes are extended by
0.007 mm. The rim remains circular, except for an
indentation at the contact patch and a couple lumps
adjacent to the contact patch.
> The latter
> effect is where the wheel gets its strength; it is ridiculous to
> suggest that the rise in tension of the other spokes is insignificant
> because without that rise in tension you might as well be riding a
> wheel with all the spokes detensioned to the point that all the wheel
> strength derives completely from the strength of the rim alone. To say
> that the rise in tension of the other spokes is insignificant is just
> utterly ridiculous.
--
Michael Press
|
| | | |
Date: 07 Sep 2007 19:13:42
From:
Subject: Re: Yet another broken spoke
|
Michael Press writes:
>>> The spokes lose huge amounts of pre-tension as they roll under the
>>> wheel. The individual the spokes all the way around the wheel show
>>> an increase of only up to 10% in tension, compared to the spoke
>>> directly under the axle's loss of tension.
>> Right. Under what criteria is a 10% increase in tension
>> insignificant, as it was described by Brandt? And in your testing,
>> as well as everyone else's, the greatest loss of tension was in the
>> spokes perpendicular to the spokes that lost tension.
>> The loss of tension caused by the local flexing of the rim cannot
>> be balanced by a rise in tension by the rest of the spokes; OTOH,
>> the flexing of the rim caused by the ovalization of the hoop _must_
>> be offset by a rise in tension by the rest of the spokes.
> The hoop does not "ovalize" in normal use, the use for which it is
> intended; to wit: transmitting a compressive load between the
> contact patch and the axle. The shape of the distortion of a rim
> under load is lumpy.
> On a thirty six spoke wheel the greatest change in spoke length is
> at the contact patch where it is -0.153 mm. The next local maximum
> of absolute spoke length change is four spokes from the contact
> patch, or one ninth of the circumference where the change is 0.014
> mm. After that all the spokes are extended by 0.007 mm. The rim
> remains circular, except for an indentation at the contact patch and
> a couple lumps adjacent to the contact patch.
To put it a different way, the rim is flattened at the road contact
area and this flattening increases the radius of the remaining
circular part of the rim (the previous arc having a shorter linear
length than when flattened. Of course you can read about this in "the
Bicycle Wheel" which is what inspired Ian and Henry Gavin to publish
the same material in their own fora.
http://www.avocet.com/wheelbook/wheelbook.html
>> The latter effect is where the wheel gets its strength; it is
>> ridiculous to suggest that the rise in tension of the other spokes
>> is insignificant because without that rise in tension you might as
>> well be riding a wheel with all the spokes detensioned to the point
>> that all the wheel strength derives completely from the strength of
>> the rim alone. To say that the rise in tension of the other spokes
>> is insignificant is just utterly ridiculous.
If you research the many times this subject has appeared in this
forum, you'll find that the vertical component of tension increases,
caused by spreading the wheel circumference, sum to zero, leaving only
the reduction in downward force of the spokes in the "load affected
zone" as the sole support of axle loads. The reason this is so, is
that at either end of the load affected zone, a bulge caused by rim
stiffness in the transition from the flattened area to the circular
part does not allow a sudden transition. This may slightly differ
depending on the bending stiffness of the rim cross section used as a
model. The ones in the book are MA-2's.
Jobst Brandt
|
| | | | |
Date: 07 Sep 2007 18:19:47
From: jim beam
Subject: Re: Yet another broken spoke
|
jobst.brandt@stanfordalumni.org wrote:
> Michael Press writes:
>
>>>> The spokes lose huge amounts of pre-tension as they roll under the
>>>> wheel. The individual the spokes all the way around the wheel show
>>>> an increase of only up to 10% in tension, compared to the spoke
>>>> directly under the axle's loss of tension.
>
>>> Right. Under what criteria is a 10% increase in tension
>>> insignificant, as it was described by Brandt? And in your testing,
>>> as well as everyone else's, the greatest loss of tension was in the
>>> spokes perpendicular to the spokes that lost tension.
>
>>> The loss of tension caused by the local flexing of the rim cannot
>>> be balanced by a rise in tension by the rest of the spokes; OTOH,
>>> the flexing of the rim caused by the ovalization of the hoop _must_
>>> be offset by a rise in tension by the rest of the spokes.
>
>> The hoop does not "ovalize" in normal use, the use for which it is
>> intended; to wit: transmitting a compressive load between the
>> contact patch and the axle. The shape of the distortion of a rim
>> under load is lumpy.
>
>> On a thirty six spoke wheel the greatest change in spoke length is
>> at the contact patch where it is -0.153 mm. The next local maximum
>> of absolute spoke length change is four spokes from the contact
>> patch, or one ninth of the circumference where the change is 0.014
>> mm. After that all the spokes are extended by 0.007 mm. The rim
>> remains circular, except for an indentation at the contact patch and
>> a couple lumps adjacent to the contact patch.
>
> To put it a different way, the rim is flattened at the road contact
> area and this flattening increases the radius of the remaining
> circular part of the rim (the previous arc having a shorter linear
> length than when flattened. Of course you can read about this in "the
> Bicycle Wheel" which is what inspired Ian and Henry Gavin to publish
> the same material in their own fora.
>
> http://www.avocet.com/wheelbook/wheelbook.html
>
>>> The latter effect is where the wheel gets its strength; it is
>>> ridiculous to suggest that the rise in tension of the other spokes
>>> is insignificant because without that rise in tension you might as
>>> well be riding a wheel with all the spokes detensioned to the point
>>> that all the wheel strength derives completely from the strength of
>>> the rim alone. To say that the rise in tension of the other spokes
>>> is insignificant is just utterly ridiculous.
>
> If you research the many times this subject has appeared in this
> forum, you'll find that the vertical component of tension increases,
> caused by spreading the wheel circumference, sum to zero, leaving only
> the reduction in downward force of the spokes in the "load affected
> zone" as the sole support of axle loads. The reason this is so, is
> that at either end of the load affected zone, a bulge caused by rim
> stiffness in the transition from the flattened area to the circular
> part does not allow a sudden transition. This may slightly differ
> depending on the bending stiffness of the rim cross section used as a
> model. The ones in the book are MA-2's.
>
and yet interestingly, wheels still manage to support load with no
bottom spokes at all...
http://www.flickr.com/photos/38636024@N00/417157612/
but that picture must be photoshop - there's no way your theory could
/possibly/ be incomplete.
|
| | |
Date: 06 Sep 2007 20:23:29
From:
Subject: Re: Yet another broken spoke
|
On Thu, 06 Sep 2007 18:15:00 -0700, SocSecTrainWreck@earthlink.net
wrote:
>On Sep 4, 8:24 pm, carlfo...@comcast.net wrote:
>
>> The spokes lose huge amounts of pre-tension as they roll under the
>> wheel. The individual the spokes all the way around the wheel show an
>> increase of only up to 10% in tension, compared to the spoke directly
>> under the axle's loss of tension.
>
>And in your testing, as well as
>everyone else's, the greatest loss of tension was in the spokes
>perpendicular to the spokes that lost tension.
[snip]
Dear SSTW,
I have never posted any test of tension loss as spokes roll under the
wheel.
Apart from that, the sentence is incoherent, possibly due to some
typo.
You still seem to be confused.
Please try again.
Cheers,
Carl Fogel
|
| | | |
Date: 06 Sep 2007 21:25:55
From:
Subject: Re: Yet another broken spoke
|
On Thu, 06 Sep 2007 20:23:29 -0600, carlfogel@comcast.net wrote:
>On Thu, 06 Sep 2007 18:15:00 -0700, SocSecTrainWreck@earthlink.net
>wrote:
>
>>On Sep 4, 8:24 pm, carlfo...@comcast.net wrote:
>>
>>> The spokes lose huge amounts of pre-tension as they roll under the
>>> wheel. The individual the spokes all the way around the wheel show an
>>> increase of only up to 10% in tension, compared to the spoke directly
>>> under the axle's loss of tension.
>>
>>And in your testing, as well as
>>everyone else's, the greatest loss of tension was in the spokes
>>perpendicular to the spokes that lost tension.
>
>[snip]
>
>Dear SSTW,
>
>I have never posted any test of tension loss as spokes roll under the
>wheel.
>
>Apart from that, the sentence is incoherent, possibly due to some
>typo.
>
>You still seem to be confused.
>
>Please try again.
>
>Cheers,
>
>Carl Fogel
I haven't checked yet, but I now remember a rig (but not the test) for
putting weights on the handlebar.
The only purpose that I can think of would been for testing either
tire contact patch or for testing spoke tension.
If it was for spoke tension, then my memory was bad and I was wrong.
I'll try to find that test.
Cheers,
Carl Fogel
|
| | | | |
Date: 07 Sep 2007 03:33:35
From:
Subject: Re: Yet another broken spoke
|
On Sep 6, 11:28 pm, jobst.bra...@stanfordalumni.org wrote:
> Carl Fogel writes:
> > Although true, its spoke tension varied from 52 to 85 kgf, which
> > made me to wonder if the irregular tension led to misleading results
> > because the higher tension spokes lost tension when theory and other
> > tests predicted that they would lose it.
> > The three spokes at 80, 80, and 85 kgf were the two at the top and
> > one at about 10 o'clock, and all three unexpectedly lost tension.
> > No other spokes were over 72 kgf.
>
> This is a front wheel (I assume, if you are weighting the handlebars).
> With that large a tension difference, your results will be misleading.
> Try to balance tension before using this wheel as an example of which
> spokes are affected by axle loading.
>
> Although the highest tension appears to be above what might cause
> misalignment, a loosely tensioned wheel with helter-skelter tension can
> be straight because the rim was straight to begin with and tension is
> insufficient to distort it. On the other hand, if widely varying
> tension is fairly high, tight and loose spokes can be balanced against
> one another but the wheel might reveal that in not being round.
>
> Let's start with a good wheel.
Just do the test you originally suggested: push down on a wheel while
you are plucking the horizontal spokes: the tone will rise
significantly. I suspect that the effect will become smaller on a more
highly tensioned wheel.
This is why Beam was able to show a wheel with the more vertical
spokes removed supporting a lot of weight- the more horizontal spokes
support the load on the wheel.
|
| | | | | |
Date: 07 Sep 2007 05:38:10
From: jim beam
Subject: Re: Yet another broken spoke
|
SocSecTrainWreck@earthlink.net wrote:
> On Sep 6, 11:28 pm, jobst.bra...@stanfordalumni.org wrote:
>> Carl Fogel writes:
>>> Although true, its spoke tension varied from 52 to 85 kgf, which
>>> made me to wonder if the irregular tension led to misleading results
>>> because the higher tension spokes lost tension when theory and other
>>> tests predicted that they would lose it.
>>> The three spokes at 80, 80, and 85 kgf were the two at the top and
>>> one at about 10 o'clock, and all three unexpectedly lost tension.
>>> No other spokes were over 72 kgf.
>> This is a front wheel (I assume, if you are weighting the handlebars).
>> With that large a tension difference, your results will be misleading.
>> Try to balance tension before using this wheel as an example of which
>> spokes are affected by axle loading.
>>
>> Although the highest tension appears to be above what might cause
>> misalignment, a loosely tensioned wheel with helter-skelter tension can
>> be straight because the rim was straight to begin with and tension is
>> insufficient to distort it. On the other hand, if widely varying
>> tension is fairly high, tight and loose spokes can be balanced against
>> one another but the wheel might reveal that in not being round.
>>
>> Let's start with a good wheel.
>
> Just do the test you originally suggested: push down on a wheel while
> you are plucking the horizontal spokes: the tone will rise
> significantly. I suspect that the effect will become smaller on a more
> highly tensioned wheel.
it can't - materials do not become stiffer as tension is increased. the
tone will be different as a function of tension, but that's an harmonic
thing, not a strength of structures thing.
>
> This is why Beam was able to show a wheel with the more vertical
> spokes removed supporting a lot of weight- the more horizontal spokes
> support the load on the wheel.
>
|
| | | | |
Date: 06 Sep 2007 22:05:22
From:
Subject: Re: Yet another broken spoke
|
Dear SSTW,
Aaargh! My memory is unreliable and I was wrong!
I apologize.
And I hope that I'll remember this embarrassing lesson not to trust my
memory.
I _did_ do test measurements of a 32-spoke front wheel, checking
tension with a Park gauge with the wheel in the air and then again
with it on the ground and an 8-pound load on the handlebar.
Here's the post:
http://groups.google.com/group/rec.bicycles.tech/msg/369d5902e39c7562
Assuming that my measurements were accurate, I found 5 roughly bottom
spokes losing tension, with spokes 32-01 at about 6'o'clock, the
bottom of the wheel:
bottom
tension
spoke change
kgf
32 -6
01 -18
02 -13
03 -12
04 -13
Six top spokes at about 12 'o'clock also lost tension (or showed 0
change), not expected:
top
tension
spoke change
kgf
17 -15
18 -13
19 -11
20 0
21 0
22 -15
Indeed, the lack of tension change continues around:
23 0
24 0
25 0 this spoke is roughly horizontal
I may try to repeat this test, since the results seem to be quite
different than everyone expects, since I flat forgot it, and since I
made a senile ass of myself insisting that I didn't even do it.
This particular wheel was a nicely true machine-made ma3 that I never
used.
Although true, its spoke tension varied from 52 to 85 kgf, which made
me to wonder if the irregular tension led to misleading results
because the higher tension spokes lost tension when theory and other
tests predicted that they would lose it.
The three spokes at 80, 80, and 85 kgf were the two at the top and one
at about 10 o'clock, and all three unexpectedly lost tension. No other
spokes were over 72 kgf.
Aaaargh!
Carl Fogel
|
| | | | | |
Date: 07 Sep 2007 01:59:32
From:
Subject: Re: Yet another broken spoke
|
On Thu, 06 Sep 2007 22:05:22 -0600, carlfogel@comcast.net wrote:
>Dear SSTW,
>
>Aaargh! My memory is unreliable and I was wrong!
>
>I apologize.
>
>And I hope that I'll remember this embarrassing lesson not to trust my
>memory.
>
>I _did_ do test measurements of a 32-spoke front wheel, checking
>tension with a Park gauge with the wheel in the air and then again
>with it on the ground and an 8-pound load on the handlebar.
>
>Here's the post:
>
>http://groups.google.com/group/rec.bicycles.tech/msg/369d5902e39c7562
>
>Assuming that my measurements were accurate, I found 5 roughly bottom
>spokes losing tension, with spokes 32-01 at about 6'o'clock, the
>bottom of the wheel:
>
>bottom
> tension
>spoke change
> kgf
>32 -6
>01 -18
>02 -13
>03 -12
>04 -13
>
>Six top spokes at about 12 'o'clock also lost tension (or showed 0
>change), not expected:
>
>top
> tension
>spoke change
> kgf
>
>17 -15
>18 -13
>19 -11
>20 0
>21 0
>22 -15
>
>Indeed, the lack of tension change continues around:
>
>23 0
>24 0
>25 0 this spoke is roughly horizontal
>
>I may try to repeat this test, since the results seem to be quite
>different than everyone expects, since I flat forgot it, and since I
>made a senile ass of myself insisting that I didn't even do it.
>
>This particular wheel was a nicely true machine-made ma3 that I never
>used.
>
>Although true, its spoke tension varied from 52 to 85 kgf, which made
>me to wonder if the irregular tension led to misleading results
>because the higher tension spokes lost tension when theory and other
>tests predicted that they would lose it.
>
>The three spokes at 80, 80, and 85 kgf were the two at the top and one
>at about 10 o'clock, and all three unexpectedly lost tension. No other
>spokes were over 72 kgf.
>
>Aaaargh!
>
>Carl Fogel
Aaargh!
Tension varied from _59_ to 85 kgf, not 52--another careless error on
my part.
CF
|
| | | | | |
Date: 07 Sep 2007 04:28:10
From:
Subject: Re: Yet another broken spoke
|
Carl Fogel writes:
> Although true, its spoke tension varied from 52 to 85 kgf, which
> made me to wonder if the irregular tension led to misleading results
> because the higher tension spokes lost tension when theory and other
> tests predicted that they would lose it.
> The three spokes at 80, 80, and 85 kgf were the two at the top and
> one at about 10 o'clock, and all three unexpectedly lost tension.
> No other spokes were over 72 kgf.
This is a front wheel (I assume, if you are weighting the handlebars).
With that large a tension difference, your results will be misleading.
Try to balance tension before using this wheel as an example of which
spokes are affected by axle loading.
Although the highest tension appears to be above what might cause
misalignment, a loosely tensioned wheel with helter-skelter tension can
be straight because the rim was straight to begin with and tension is
insufficient to distort it. On the other hand, if widely varying
tension is fairly high, tight and loose spokes can be balanced against
one another but the wheel might reveal that in not being round.
Let's start with a good wheel.
Jobst Brandt
|
| | | | | | |
Date: 06 Sep 2007 21:50:22
From: jim beam
Subject: Re: Yet another broken spoke
|
jobst.brandt@stanfordalumni.org wrote:
> Carl Fogel writes:
>
>> Although true, its spoke tension varied from 52 to 85 kgf, which
>> made me to wonder if the irregular tension led to misleading results
>> because the higher tension spokes lost tension when theory and other
>> tests predicted that they would lose it.
>
>> The three spokes at 80, 80, and 85 kgf were the two at the top and
>> one at about 10 o'clock, and all three unexpectedly lost tension.
>> No other spokes were over 72 kgf.
>
> This is a front wheel (I assume, if you are weighting the handlebars).
> With that large a tension difference, your results will be misleading.
> Try to balance tension before using this wheel as an example of which
> spokes are affected by axle loading.
>
> Although the highest tension appears to be above what might cause
> misalignment, a loosely tensioned wheel with helter-skelter tension can
> be straight because the rim was straight to begin with and tension is
> insufficient to distort it. On the other hand, if widely varying
> tension is fairly high, tight and loose spokes can be balanced against
> one another but the wheel might reveal that in not being round.
>
> Let's start with a good wheel.
>
since tension does not affect elasticity, why would you expect a
different tension delta if the static tensions were different?
|
| |
Date: 05 Sep 2007 22:19:47
From: Joe Riel
Subject: Re: Yet another broken spoke
|
jim beam <spamvortex@bad.example.net > writes:
> Joe Riel wrote:
>> jim beam <spamvortex@bad.example.net> writes:
>>
>>> Peter Cole wrote:
>>>> I think the burden is on you to explain how the spoke elbow is
>>>> unsupported (or how it can bend if it isn't).
>>> er, the light gap between the hub and the spoke [...]
>>
>> I don't see any light gap on my wheels. The outbound spokes
>> are fully bedded into the flange. The inbound spokes less so,
>> but still no visible gap.
>>
>
>
> http://www.flickr.com/photos/38636024@N00/1313347532/
>
> xtr hub, d.t. spokes. gaps on heads in and heads out spokes. not an
> atypical build i think you'll agree.
>
Here's a picture of my front hub. Hard to see the inbound spokes;
lighting wasn't ideal.
http://www.flickr.com/photos/12733237@N05/
--
Joe Riel
|
| | |
Date: 06 Sep 2007 05:44:27
From: jim beam
Subject: Re: Yet another broken spoke
|
Joe Riel wrote:
> jim beam <spamvortex@bad.example.net> writes:
>
>> Joe Riel wrote:
>>> jim beam <spamvortex@bad.example.net> writes:
>>>
>>>> Peter Cole wrote:
>>>>> I think the burden is on you to explain how the spoke elbow is
>>>>> unsupported (or how it can bend if it isn't).
>>>> er, the light gap between the hub and the spoke [...]
>>> I don't see any light gap on my wheels. The outbound spokes
>>> are fully bedded into the flange. The inbound spokes less so,
>>> but still no visible gap.
>>>
>>
>> http://www.flickr.com/photos/38636024@N00/1313347532/
>>
>> xtr hub, d.t. spokes. gaps on heads in and heads out spokes. not an
>> atypical build i think you'll agree.
>>
>
> Here's a picture of my front hub. Hard to see the inbound spokes;
> lighting wasn't ideal.
>
> http://www.flickr.com/photos/12733237@N05/
>
heads in touch and heads out don't? can't see clearly in that pic.
|
| |
Date: 05 Sep 2007 21:24:59
From: Joe Riel
Subject: Re: Yet another broken spoke
|
jim beam <spamvortex@bad.example.net > writes:
> Peter Cole wrote:
>> I think the burden is on you to explain how the spoke elbow is
>> unsupported (or how it can bend if it isn't).
>
> er, the light gap between the hub and the spoke [...]
I don't see any light gap on my wheels. The outbound spokes
are fully bedded into the flange. The inbound spokes less so,
but still no visible gap.
--
Joe Riel
|
| | |
Date: 05 Sep 2007 21:36:17
From: jim beam
Subject: Re: Yet another broken spoke
|
Joe Riel wrote:
> jim beam <spamvortex@bad.example.net> writes:
>
>> Peter Cole wrote:
>>> I think the burden is on you to explain how the spoke elbow is
>>> unsupported (or how it can bend if it isn't).
>> er, the light gap between the hub and the spoke [...]
>
> I don't see any light gap on my wheels. The outbound spokes
> are fully bedded into the flange. The inbound spokes less so,
> but still no visible gap.
>
http://www.flickr.com/photos/38636024@N00/1313347532/
xtr hub, d.t. spokes. gaps on heads in and heads out spokes. not an
atypical build i think you'll agree.
|
| |
Date: 05 Sep 2007 23:14:00
From: Gary Young
Subject: Re: Yet another broken spoke
|
On Wed, 05 Sep 2007 20:56:58 -0700, jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>>> Ben C wrote:
>>>>> On 2007-09-04, carlfogel@comcast.net <carlfogel@comcast.net> wrote:
>>>>
>>>>>> But the other spoke can only drop from 100 pounds of pre-tension down
>>>>>> to 0. After it loses only 100 pounds of tension, it just rattles.
>>>>>
>>>>> I get it! Thanks.
>>>>>
>>>>> Of course whether it does rattle harmlessly or flex horribly, rapidly
>>>>> fatiguing itself to death, is another matter.
>>>>
>>>> It could only "flex horribly" (or at all) if the spoke was bowed.
>>>> Even in that case, you'd have to consider where the flex occurred vs
>>>> where the spokes broke. The "flexing horribly" speculation also needs
>>>> to consider the actual amount of rim deflection which bounds the
>>>> degree of "horribleness".
>>>>
>>>> A worst case scenario would be where the spoke elbow angle did not
>>>> match the angle of the spoke hole to flange. In that case,
>>>> fluctuations in tension could cause elbow bending when the overall
>>>> tension wasn't high enough to keep the spoke fully supported. To have
>>>> that happen the angular mismatch would have had to survived the
>>>> initial wheel tensioning and stress relief. If a wheel was built with
>>>> low tension and not stress relieved, and a spoke subsequently became
>>>> loose enough to lose support at the elbow, it might bend enough to
>>>> fatigue rapidly, but I would consider this to be the consequence of a
>>>> bad initial build rather than a loose spoke per se.
>>>
>>> wow! how to admit something you've previously denied, while phrasing
>>> it as further denial!!! quite masterful.
>>
>> Only in your world. In the first paragraph, I was referring to the spoke
>> bending along its whole length, the second only at the elbow -- in case
>> that wasn't clear.
>>
>> I think the burden is on you to explain how the spoke elbow is
>> unsupported (or how it can bend if it isn't).
>
> er, the light gap between the hub and the spoke ought to be proof to
> anyone whose intent is not to bullshit and deceive...
One can greatly reduce that gap by correcting the spoke line, something
you've previously said was unnecessary and even harmful. Has your position
changed?
|
| |
Date: 04 Sep 2007 17:38:54
From:
Subject: Re: Yet another broken spoke
|
On Sep 3, 8:08 pm, tkeats2...@hotmail.com (Tom Keats) wrote:
> In article <46dc88ba$0$14092$742ec...@news.sonic.net>,
> jobst.bra...@stanfordalumni.org writes:
>
>
>
> > Waving the long term fatigue flag does not answer the question of how
> > low spoke tension causes spoke failure; a claim that appears in this
> > newsgroup often. I believe the example of rim deflection under riding
> > loads (which is the amount by which spoke preload is reduced) is the
> > appropriate parameter for stress change and it shows that compression
> > buckling is not possible in that respect as I pointed out.
>
> So, would a newly-installed, brand-new spoke that's too loose,
> immediately break due to rim deflection, or break before its
> adjacent brethren (that have hitherto held-up so well) do?
>
> What exactly /is/ rim deflection, and how does it happen?
> What makes it happen? Are we talking about the momentary
> bottom of the rim tending to squash flat on the surface it
> runs on and thereby compressing spokes, (I guess not, since
> you above rule-out compression buckling,) or are we talking
> about putting lateral 'S' curves in the rim, and thereby
> bending spokes? Or maybe it's about torque in a hard-driven
> wheel, between the rim and hub, where the hub tends to rotate
> faster than the rim can keep up with, and the spokes in-between
> bear the brunt, and the rim is deflected from the POV of
> the hub (and the connecting spokes?)
>
> I don't know about these things, but I am curious,
> and I'd truly like to understand.
It seems obvious to me that there are two types of rim deflection. One
is the deflection of the rim in the immediate area of where force is
applied and where the rim is closest to the pavement; it is a function
of how pliable the rim material is. This deflection is essentially
independent of spoke tension. The other type of deflection is a
function of spoke tension and the force applied to the wheel- how much
the spoke tension allows the wheel hoop to deform from its shape as a
circle. I happen to believe that it is this latter deflection that is
important to understanding the forces at work in a bicycle wheel, but
my views are very controversial because they are at variance with the
"FEAs" if not the experimental evidence.
I don't have time to argue the discussion that is probably
forthcoming, but do the experiment that Brandt suggests, and decide
for yourself how to integrate the results with Brandt's claims. It's
kinda hard.
|
| |
Date: 04 Sep 2007 17:19:47
From:
Subject: Re: Yet another broken spoke
|
On Sep 4, 12:17 pm, jobst.bra...@stanfordalumni.org wrote:
> Tom Keats writes:
> >> Waving the long term fatigue flag does not answer the question of
> >> how low spoke tension causes spoke failure; a claim that appears in
> >> this newsgroup often. I believe the example of rim deflection
> >> under riding loads (which is the amount by which spoke preload is
> >> reduced) is the appropriate parameter for stress change and it
> >> shows that compression buckling is not possible in that respect as
> >> I pointed out.
> > So, would a newly-installed, brand-new spoke that's too loose,
> > immediately break due to rim deflection, or break before its
> > adjacent brethren (that have hitherto held-up so well) do?
>
> If the spoke was initially not loose, as spokes are on a new wheel, It
> would only be deemed too loose if load deflection of the rim at the
> load affected zone (where the tire meets the road) is greater than
> elastic elongation of spokes from tensioning. That is the problem
> with many wheels these days where rims crack if tightened to a
> reliable tension that will mot slacken under load. That is
> exacerbated by using fewer spokes so that the preload of one or two
> spokes alone support the load.
>
> > What exactly /is/ rim deflection, and how does it happen? What
> > makes it happen? Are we talking about the momentary bottom of the
> > rim tending to squash flat on the surface it runs on and thereby
> > compressing spokes, (I guess not, since you above rule-out
> > compression buckling,) or are we talking about putting lateral 'S'
> > curves in the rim, and thereby bending spokes? Or maybe it's about
> > torque in a hard-driven wheel, between the rim and hub, where the
> > hub tends to rotate faster than the rim can keep up with, and the
> > spokes in-between bear the brunt, and the rim is deflected from the
> > POV of the hub (and the connecting spokes?)
>
> When a wheel bears a load applied to its axle, that force is
> transmitted to the road n=by compressing the spokes in roughly the
> tire contact patch so that they lose preload equivalent to the axle
> load. All other spokes remain essentially unchanged in tension
> (especially the top ones that have been believed to get tighter).
>
> You can check this by plucking spokes with and without loading the
> wheel and not the tone. A lower tone indicates lower tension, a
> higher tone indicated higher tension then initially when the wheel was
> not loaded.
I did this test and the other spokes did not by any stretch of my
aural imagination "remain essentially unchanged in tension", nor did
they when Fogel attempted to measure the change. I suggest that
everyone who reads this follow Brandt's advice and then report back
here. If you are not tone deaf you will note that the spokes
horizontal to the ground rise in tension enough that the change in
tone (going higher) is easily discerned.
|
| | |
Date: 04 Sep 2007 19:24:39
From:
Subject: Re: Yet another broken spoke
|
On Tue, 04 Sep 2007 17:19:47 -0700, SocSecTrainWreck@earthlink.net
wrote:
>On Sep 4, 12:17 pm, jobst.bra...@stanfordalumni.org wrote:
>> Tom Keats writes:
>> >> Waving the long term fatigue flag does not answer the question of
>> >> how low spoke tension causes spoke failure; a claim that appears in
>> >> this newsgroup often. I believe the example of rim deflection
>> >> under riding loads (which is the amount by which spoke preload is
>> >> reduced) is the appropriate parameter for stress change and it
>> >> shows that compression buckling is not possible in that respect as
>> >> I pointed out.
>> > So, would a newly-installed, brand-new spoke that's too loose,
>> > immediately break due to rim deflection, or break before its
>> > adjacent brethren (that have hitherto held-up so well) do?
>>
>> If the spoke was initially not loose, as spokes are on a new wheel, It
>> would only be deemed too loose if load deflection of the rim at the
>> load affected zone (where the tire meets the road) is greater than
>> elastic elongation of spokes from tensioning. That is the problem
>> with many wheels these days where rims crack if tightened to a
>> reliable tension that will mot slacken under load. That is
>> exacerbated by using fewer spokes so that the preload of one or two
>> spokes alone support the load.
>>
>> > What exactly /is/ rim deflection, and how does it happen? What
>> > makes it happen? Are we talking about the momentary bottom of the
>> > rim tending to squash flat on the surface it runs on and thereby
>> > compressing spokes, (I guess not, since you above rule-out
>> > compression buckling,) or are we talking about putting lateral 'S'
>> > curves in the rim, and thereby bending spokes? Or maybe it's about
>> > torque in a hard-driven wheel, between the rim and hub, where the
>> > hub tends to rotate faster than the rim can keep up with, and the
>> > spokes in-between bear the brunt, and the rim is deflected from the
>> > POV of the hub (and the connecting spokes?)
>>
>> When a wheel bears a load applied to its axle, that force is
>> transmitted to the road n=by compressing the spokes in roughly the
>> tire contact patch so that they lose preload equivalent to the axle
>> load. All other spokes remain essentially unchanged in tension
>> (especially the top ones that have been believed to get tighter).
>>
>> You can check this by plucking spokes with and without loading the
>> wheel and not the tone. A lower tone indicates lower tension, a
>> higher tone indicated higher tension then initially when the wheel was
>> not loaded.
>
>I did this test and the other spokes did not by any stretch of my
>aural imagination "remain essentially unchanged in tension", nor did
>they when Fogel attempted to measure the change. I suggest that
>everyone who reads this follow Brandt's advice and then report back
>here. If you are not tone deaf you will note that the spokes
>horizontal to the ground rise in tension enough that the change in
>tone (going higher) is easily discerned.
Dear SSTW,
I am unaware that I made any such conclusions.
My experience agrees with Jobst's experience, with Professor Gavin's
strain gauge measurements, and with Ian's theoretical calculations.
The spokes lose huge amounts of pre-tension as they roll under the
wheel. The individual the spokes all the way around the wheel show an
increase of only up to 10% in tension, compared to the spoke directly
under the axle's loss of tension.
Here are Ian's calculations:
http://www.astounding.org.uk/ian/wheel/index.html
Note that the greatest increase in tension in Ian's example is the
_lower_ spoke at roughly 5 'o'clock, which gains 40 newtons, about 10%
of the compression lost by the spoke under the axle, 350 newtons.
Here are Professor Gavin's measurements of an actual spoke while the
bicycle was being ridden in figures 10 & 11:
http://www.duke.edu/~hpgavin/papers/HPGavin-Wheel-Paper.pdf
The massive loss of tension in the lowermost spokes is obvious.
Possibly you're confusing the results of my tests of spoke tension
change when two spokes are squeezed together on an unloaded wheel,
which is an entirely different situation.
Cheers,
Carl Fogel
|
| | | |
Date: 05 Sep 2007 03:02:33
From: Mike Kruger
Subject: Re: Yet another broken spoke
|
carlfogel@comcast.net wrote:
>
> My experience agrees with Jobst's experience, with Professor Gavin's
> strain gauge measurements, and with Ian's theoretical calculations.
>
> The spokes lose huge amounts of pre-tension as they roll under the
> wheel. The individual the spokes all the way around the wheel show an
> increase of only up to 10% in tension, compared to the spoke directly
> under the axle's loss of tension.
>
So, this means those Kevlar "emergency" spokes I've carried with me on tours
are basicallly useless?
You can't "pull" them because the cord is strong, but you can "push" them
like cooked spaghetti.
Here's the product I'm referring to:
http://www.yellowjersey.org/fiberfix.html
|
| | | | |
Date: 04 Sep 2007 21:49:01
From:
Subject: Re: Yet another broken spoke
|
On Wed, 05 Sep 2007 03:02:33 GMT, "Mike Kruger"
<MikeKr@mouse-potato.com > wrote:
>carlfogel@comcast.net wrote:
>>
>> My experience agrees with Jobst's experience, with Professor Gavin's
>> strain gauge measurements, and with Ian's theoretical calculations.
>>
>> The spokes lose huge amounts of pre-tension as they roll under the
>> wheel. The individual the spokes all the way around the wheel show an
>> increase of only up to 10% in tension, compared to the spoke directly
>> under the axle's loss of tension.
>>
>So, this means those Kevlar "emergency" spokes I've carried with me on tours
>are basicallly useless?
>
>You can't "pull" them because the cord is strong, but you can "push" them
>like cooked spaghetti.
>
>Here's the product I'm referring to:
>http://www.yellowjersey.org/fiberfix.html
Dear Mark,
Sorry, but you're still misunderstanding how pre-tension works. (Don't
feel bad--it's a common mistake.)
The Kevlar spokes work just like wire spokes.
You pre-tension the Kevlar spoke to 200 pounds.
As it rolls under the wheel, it loses considerable tension.
You can see how this works with a brick, a hefty weight, and a
bathroom scale.
Put the weight on the scale and note what the scale says, say 10
pounds.
Now tie the rubber band to the weight and pull up, putting tension on
the rubber "spoke" as if it were a wire or kevlar spoke. Rubber
stretches much more visibly than steel or kevlar, so you can see that
tension means elongation.
Note that the scale now reads less, say 5 pounds.
To push down with the pre-tensioned rubber "spoke", just relax your
hand a little. The rubber "spoke" visibly shortens (compression) and
the scale gains what the pre-tensioned rubber band loses.
Once you lose _all_ the pre-tension, the spoke becomes literally loose
and rattles or flops uselessly, whether it's steel wire, kevlar cord,
or rubber band.
Until you work your way through how pre-tension actually works, it
will seem absolutely ridiculous.
And yes, I carry a spare Kevlar spoke, whose pre-tensioned physics
have been repeatedly discussed on RBT. Again, don't feel bad about the
misunderstanding--I've been in your position, and so have most people
who glance at a wheel and mistakenly assume that the load must hang
from the upper spokes because it seems so damned obvious and logical.
The trouble is, engineering theory predicts and strain gauge
measurements confirm that the stupid wheel works almost exactly the
opposite of what we expect. Work your way through those links,
remember that Kevlar stretches and pre-tensions much like steel (an
amount invisible to the naked eye), and you'll see why the tension
drops dramatically for the spokes _under_ the axle, but scarcely rises
at all for _all_ the other spokes, including the ones pulling sideways
and downward.
Cheers,
Carl Fogel
|
| | | | | |
Date: 04 Sep 2007 22:43:37
From:
Subject: Re: Yet another broken spoke
|
On Tue, 04 Sep 2007 21:49:01 -0600, carlfogel@comcast.net wrote:
>On Wed, 05 Sep 2007 03:02:33 GMT, "Mike Kruger"
><MikeKr@mouse-potato.com> wrote:
>
>>carlfogel@comcast.net wrote:
>>>
>>> My experience agrees with Jobst's experience, with Professor Gavin's
>>> strain gauge measurements, and with Ian's theoretical calculations.
>>>
>>> The spokes lose huge amounts of pre-tension as they roll under the
>>> wheel. The individual the spokes all the way around the wheel show an
>>> increase of only up to 10% in tension, compared to the spoke directly
>>> under the axle's loss of tension.
>>>
>>So, this means those Kevlar "emergency" spokes I've carried with me on tours
>>are basicallly useless?
>>
>>You can't "pull" them because the cord is strong, but you can "push" them
>>like cooked spaghetti.
>>
>>Here's the product I'm referring to:
>>http://www.yellowjersey.org/fiberfix.html
>
>Dear Mark,
>
>Sorry, but you're still misunderstanding how pre-tension works. (Don't
>feel bad--it's a common mistake.)
>
>The Kevlar spokes work just like wire spokes.
>
>You pre-tension the Kevlar spoke to 200 pounds.
>
>As it rolls under the wheel, it loses considerable tension.
>
>You can see how this works with a brick, a hefty weight, and a
>bathroom scale.
>
>Put the weight on the scale and note what the scale says, say 10
>pounds.
>
>Now tie the rubber band to the weight and pull up, putting tension on
>the rubber "spoke" as if it were a wire or kevlar spoke. Rubber
>stretches much more visibly than steel or kevlar, so you can see that
>tension means elongation.
>
>Note that the scale now reads less, say 5 pounds.
>
>To push down with the pre-tensioned rubber "spoke", just relax your
>hand a little. The rubber "spoke" visibly shortens (compression) and
>the scale gains what the pre-tensioned rubber band loses.
>
>Once you lose _all_ the pre-tension, the spoke becomes literally loose
>and rattles or flops uselessly, whether it's steel wire, kevlar cord,
>or rubber band.
>
>Until you work your way through how pre-tension actually works, it
>will seem absolutely ridiculous.
>
>And yes, I carry a spare Kevlar spoke, whose pre-tensioned physics
>have been repeatedly discussed on RBT. Again, don't feel bad about the
>misunderstanding--I've been in your position, and so have most people
>who glance at a wheel and mistakenly assume that the load must hang
>from the upper spokes because it seems so damned obvious and logical.
>
>The trouble is, engineering theory predicts and strain gauge
>measurements confirm that the stupid wheel works almost exactly the
>opposite of what we expect. Work your way through those links,
>remember that Kevlar stretches and pre-tensions much like steel (an
>amount invisible to the naked eye), and you'll see why the tension
>drops dramatically for the spokes _under_ the axle, but scarcely rises
>at all for _all_ the other spokes, including the ones pulling sideways
>and downward.
>
>Cheers,
>
>Carl Fogel
Dear Mike,
Aaaargh!
Sorry about getting your name wrong!
Sadly, you're not my first innocent victim.
Cheers,
Charles Vogel
|
| |
Date: 03 Sep 2007 18:08:13
From: Tom Keats
Subject: Re: Yet another broken spoke
|
In article <46dc88ba$0$14092$742ec2ed@news.sonic.net >,
jobst.brandt@stanfordalumni.org writes:
>
> Waving the long term fatigue flag does not answer the question of how
> low spoke tension causes spoke failure; a claim that appears in this
> newsgroup often. I believe the example of rim deflection under riding
> loads (which is the amount by which spoke preload is reduced) is the
> appropriate parameter for stress change and it shows that compression
> buckling is not possible in that respect as I pointed out.
So, would a newly-installed, brand-new spoke that's too loose,
immediately break due to rim deflection, or break before its
adjacent brethren (that have hitherto held-up so well) do?
What exactly /is/ rim deflection, and how does it happen?
What makes it happen? Are we talking about the momentary
bottom of the rim tending to squash flat on the surface it
runs on and thereby compressing spokes, (I guess not, since
you above rule-out compression buckling,) or are we talking
about putting lateral 'S' curves in the rim, and thereby
bending spokes? Or maybe it's about torque in a hard-driven
wheel, between the rim and hub, where the hub tends to rotate
faster than the rim can keep up with, and the spokes in-between
bear the brunt, and the rim is deflected from the POV of
the hub (and the connecting spokes?)
I don't know about these things, but I am curious,
and I'd truly like to understand.
cheers,
Tom
--
Nothing is safe from me.
I'm really at:
tkeats curlicue vcn dot bc dot ca
|
| | |
Date: 04 Sep 2007 17:36:15
From:
Subject: Re: Yet another broken spoke
|
Tom Keats writes:
>> Waving the long term fatigue flag does not answer the question of
>> how low spoke tension causes spoke failure; a claim that appears in
>> this newsgroup often. I believe the example of rim deflection
>> under riding loads (which is the amount by which spoke preload is
>> reduced) is the appropriate parameter for stress change and it
>> shows that compression buckling is not possible in that respect as
>> I pointed out.
> So, would a newly-installed, brand-new spoke that's too loose,
> immediately break due to rim deflection, or break before its
> adjacent brethren (that have hitherto held-up so well) do?
If the spoke was initially not loose, as spokes are on a new wheel, It
would only be deemed too loose if load deflection of the rim at the
load affected zone (where the tire meets the road) is greater than
elastic elongation of spokes from tensioning. That is the problem
with many wheels these days where rims crack if tightened to a
reliable tension that will mot slacken under load. That is
exacerbated by using fewer spokes so that the preload of one or two
spokes alone support the load.
> What exactly /is/ rim deflection, and how does it happen? What
> makes it happen? Are we talking about the momentary bottom of the
> rim tending to squash flat on the surface it runs on and thereby
> compressing spokes, (I guess not, since you above rule-out
> compression buckling,) or are we talking about putting lateral 'S'
> curves in the rim, and thereby bending spokes? Or maybe it's about
> torque in a hard-driven wheel, between the rim and hub, where the
> hub tends to rotate faster than the rim can keep up with, and the
> spokes in-between bear the brunt, and the rim is deflected from the
> POV of the hub (and the connecting spokes?)
When a wheel bears a load applied to its axle, that force is
transmitted to the road by compressing the spokes in roughly the tire
contact patch so that they lose preload equivalent to the axle load.
All other spokes remain essentially unchanged in tension (especially
the top ones that have been believed to get tighter).
You can check this by plucking spokes with and without loading the
wheel and note the tone. A lower tone indicates lower tension, a
higher tone indicated higher tension then initially when the wheel was
not loaded.
> I don't know about these things, but I am curious, and I'd truly
> like to understand.
You can get a better picture of this in "the Bicycle Wheel" in which
this is described in detail with computed graphs of wheel deformation.
This subject comes up often enough that this book on the shelves of
most bicycle shops. It is also available from Amazon and ABE, among
others.
http://sheldonbrown.com/harris/books.html#brandt
http://www.amazon.com/exec/obidos/ISBN=0960723668/1361-7743389-379578
http://tinyurl.com/3d7a49
Jobst Brandt
|
| | |
Date: 04 Sep 2007 17:17:36
From:
Subject: Re: Yet another broken spoke
|
Tom Keats writes:
>> Waving the long term fatigue flag does not answer the question of
>> how low spoke tension causes spoke failure; a claim that appears in
>> this newsgroup often. I believe the example of rim deflection
>> under riding loads (which is the amount by which spoke preload is
>> reduced) is the appropriate parameter for stress change and it
>> shows that compression buckling is not possible in that respect as
>> I pointed out.
> So, would a newly-installed, brand-new spoke that's too loose,
> immediately break due to rim deflection, or break before its
> adjacent brethren (that have hitherto held-up so well) do?
If the spoke was initially not loose, as spokes are on a new wheel, It
would only be deemed too loose if load deflection of the rim at the
load affected zone (where the tire meets the road) is greater than
elastic elongation of spokes from tensioning. That is the problem
with many wheels these days where rims crack if tightened to a
reliable tension that will mot slacken under load. That is
exacerbated by using fewer spokes so that the preload of one or two
spokes alone support the load.
> What exactly /is/ rim deflection, and how does it happen? What
> makes it happen? Are we talking about the momentary bottom of the
> rim tending to squash flat on the surface it runs on and thereby
> compressing spokes, (I guess not, since you above rule-out
> compression buckling,) or are we talking about putting lateral 'S'
> curves in the rim, and thereby bending spokes? Or maybe it's about
> torque in a hard-driven wheel, between the rim and hub, where the
> hub tends to rotate faster than the rim can keep up with, and the
> spokes in-between bear the brunt, and the rim is deflected from the
> POV of the hub (and the connecting spokes?)
When a wheel bears a load applied to its axle, that force is
transmitted to the road n=by compressing the spokes in roughly the
tire contact patch so that they lose preload equivalent to the axle
load. All other spokes remain essentially unchanged in tension
(especially the top ones that have been believed to get tighter).
You can check this by plucking spokes with and without loading the
wheel and not the tone. A lower tone indicates lower tension, a
higher tone indicated higher tension then initially when the wheel was
not loaded.
> I don't know about these things, but I am curious, and I'd truly
> like to understand.
You can get a better picture of this in "the Bicycle Wheel" in which
this is described in detail with computed graphs of wheel deformation.
This subject comes up often enough that this book on the shelves of
most bicycle shops. It is also available from Amazon and ABE, among
others.
http://sheldonbrown.com/harris/books.html#brandt
http://www.amazon.com/exec/obidos/ISBN=0960723668/1361-7743389-379578
http://tinyurl.com/3d7a49
Jobst Brandt
|
| |
Date: 03 Sep 2007 06:43:21
From: jim beam
Subject: Re: Yet another broken spoke
|
Just A User wrote:
> It happened again! I broke ANOTHER spoke on my road bike. This makes the
> second break in a month maybe a month and a half. Now I know I don't
> have the lightest riding style compared to some riders. And I am not the
> lightest of all riders. But then again I am riding on 32 triple cross
> wheels. What I don't understand is why am I breaking them on the front
> wheel only? I thought the back wheel carried more weight. So I have a
> few extra spokes I bought when I had the wheel at the lbs for the last
> spoke replacement. But now I am thinking that a new / better machine
> built wheel, or cough, a handbuilt wheels might be a more reliable way
> to go. When I say handbuilt, I mean with my hands, that have no
> experience building wheels. All opinions welcome.
>
> J.A.U.
has anybody yet bothered to ask the most important question? "what
brand are the spokes"???
this is the most important issue. you need to have good quality spokes
to resist fatigue - they're made from fatigue resistant material. if
your current spokes are some cheap no-name brand, i would re-spoke to
ensure reliability, especially as front wheels don't see as extreme
stress cycles as dished rears.
|
| | |
Date: 03 Sep 2007 09:53:30
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-03, jim beam <spamvortex@bad.example.net > wrote:
> Just A User wrote:
>> It happened again! I broke ANOTHER spoke on my road bike. This makes the
>> second break in a month maybe a month and a half. Now I know I don't
>> have the lightest riding style compared to some riders. And I am not the
>> lightest of all riders. But then again I am riding on 32 triple cross
>> wheels. What I don't understand is why am I breaking them on the front
>> wheel only? I thought the back wheel carried more weight. So I have a
>> few extra spokes I bought when I had the wheel at the lbs for the last
>> spoke replacement. But now I am thinking that a new / better machine
>> built wheel, or cough, a handbuilt wheels might be a more reliable way
>> to go. When I say handbuilt, I mean with my hands, that have no
>> experience building wheels. All opinions welcome.
>>
>> J.A.U.
>
> has anybody yet bothered to ask the most important question? "what
> brand are the spokes"???
Actually I did suggest cheap and nasty spokes might be the problem.
|
| | | |
Date: 03 Sep 2007 08:12:20
From: Bill Sornson
Subject: Re: Yet another broken spoke
|
Ben C wrote:
{jim beam asked}
>> has anybody yet bothered to ask the most important question? "what
>> brand are the spokes"???
> Actually I did suggest cheap and nasty spokes might be the problem.
Good date material, however.
Bill "slow morning" S.
|
| | |
Date: 03 Sep 2007 10:01:16
From: Just A User
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Just A User wrote:
>> It happened again! I broke ANOTHER spoke on my road bike. This makes
>> the second break in a month maybe a month and a half. Now I know I
>> don't have the lightest riding style compared to some riders. And I am
>> not the lightest of all riders. But then again I am riding on 32
>> triple cross wheels. What I don't understand is why am I breaking them
>> on the front wheel only? I thought the back wheel carried more weight.
>> So I have a few extra spokes I bought when I had the wheel at the lbs
>> for the last spoke replacement. But now I am thinking that a new /
>> better machine built wheel, or cough, a handbuilt wheels might be a
>> more reliable way to go. When I say handbuilt, I mean with my hands,
>> that have no experience building wheels. All opinions welcome.
>>
>> J.A.U.
>
> has anybody yet bothered to ask the most important question? "what
> brand are the spokes"???
>
> this is the most important issue. you need to have good quality spokes
> to resist fatigue - they're made from fatigue resistant material. if
> your current spokes are some cheap no-name brand, i would re-spoke to
> ensure reliability, especially as front wheels don't see as extreme
> stress cycles as dished rears.
No I don't recall anyone asking the brand of the breaking spokes. I
assume they are no-name cheapos. They are in a set of Alex R500 rims
which seem to be the low end for that brand. They came on a entry level
Fuji Ace.
|
| | | |
Date: 03 Sep 2007 07:06:16
From: jim beam
Subject: Re: Yet another broken spoke
|
Just A User wrote:
> jim beam wrote:
>> Just A User wrote:
>>> It happened again! I broke ANOTHER spoke on my road bike. This makes
>>> the second break in a month maybe a month and a half. Now I know I
>>> don't have the lightest riding style compared to some riders. And I
>>> am not the lightest of all riders. But then again I am riding on 32
>>> triple cross wheels. What I don't understand is why am I breaking
>>> them on the front wheel only? I thought the back wheel carried more
>>> weight. So I have a few extra spokes I bought when I had the wheel at
>>> the lbs for the last spoke replacement. But now I am thinking that a
>>> new / better machine built wheel, or cough, a handbuilt wheels might
>>> be a more reliable way to go. When I say handbuilt, I mean with my
>>> hands, that have no experience building wheels. All opinions welcome.
>>>
>>> J.A.U.
>>
>> has anybody yet bothered to ask the most important question? "what
>> brand are the spokes"???
>>
>> this is the most important issue. you need to have good quality spokes
>> to resist fatigue - they're made from fatigue resistant material. if
>> your current spokes are some cheap no-name brand, i would re-spoke to
>> ensure reliability, especially as front wheels don't see as extreme
>> stress cycles as dished rears.
> No I don't recall anyone asking the brand of the breaking spokes. I
> assume they are no-name cheapos. They are in a set of Alex R500 rims
> which seem to be the low end for that brand. They came on a entry level
> Fuji Ace.
so there's your problem - and no amount of "stress relief" can fix that.
if you're interested in the idea of wheel building, now is your
opportunity to re-spoke with a quality brand and take care of it.
|
| |
Date: 03 Sep 2007 00:29:49
From: Tom Keats
Subject: Re: Yet another broken spoke
|
In article <46db6f43$0$14067$742ec2ed@news.sonic.net >,
jobst.brandt@stanfordalumni.org writes:
> Clare who? writes:
>
>> And be SURE the spokes are tensioned adequately. Loose spokes break.
>> Tight spokes don't (as a general rule of thumb)
>
> I keep seeing this admonition yet no one seems to be able to describe
> the mechanism that causes such spoke failures. Loosely spoked wheels
> can allow the nipples to unscrew and cause wheel misalignment, but
> spoke failure is caused by metal fatigue that arises from tension
> change, caused once with every wheel rotation as spokes pass through
> the zone of tire contact with the road. This must occur with stress
> near the yield stress, something that does not readily occur in loose
> spokes.
>
> Please explain.
I can't.
But I /do/ know from empirical experience that once one
spoke breaks, its fellows are soon to follow.
I'm dealing with that right now, on my drive-side
rear wheel. Except once that first spoke broke, I
took the wheel out and swapped-in a less desirable
one, just to have some transportation, to keep my
favourite bike going. I've gotta buy 18 short spokes
pretty soon, because I want that wheel back. Hell, I
might as well respoke the whole kit-'n-kaboodle. Actually
I should buy a whole new wheel, as the rim is getting worn.
And I'm talking about a stress-relieved wheel that's put in
a lot of service, and has just ... had it.
Spokes are not immortal. Not even with featherweight riders.
Especially if they've got strong legs and lots of
vertical terrain to ride over.
Spokes get old, and just plain die.
cheers,
Tom
--
Nothing is safe from me.
I'm really at:
tkeats curlicue vcn dot bc dot ca
|
| |
Date: 03 Sep 2007 00:10:49
From: landotter
Subject: Re: Yet another broken spoke
|
On Sep 2, 3:11 pm, Peter Cole <peter_c...@comcast.net > wrote:
> Just A User wrote:
> > It happened again! I broke ANOTHER spoke on my road bike. This makes the
> > second break in a month maybe a month and a half. Now I know I don't
> > have the lightest riding style compared to some riders. And I am not the
> > lightest of all riders. But then again I am riding on 32 triple cross
> > wheels. What I don't understand is why am I breaking them on the front
> > wheel only? I thought the back wheel carried more weight. So I have a
> > few extra spokes I bought when I had the wheel at the lbs for the last
> > spoke replacement. But now I am thinking that a new / better machine
> > built wheel, or cough, a handbuilt wheels might be a more reliable way
> > to go. When I say handbuilt, I mean with my hands, that have no
> > experience building wheels. All opinions welcome.
>
> > J.A.U.
>
> I would just bring the wheel up to (even) tension & stress relieve it
> well. If it still breaks spokes, you could respoke.
>
> I prefer to buy machine made wheels, simply because they're cheaper than
> the parts and save some time lacing. I just tension & stress relieve.
> I've done that on many sets of wheels with no breakage problems.
I've done that many times as well, before I took time to learn to
lace. I'd still do it for something common and good like Ultegra/OP/
DB, which is available for under $250 a pair online. Ten minutes with
a spoke wrench, and those wheels are good for years.
|
| |
Date: 02 Sep 2007 14:42:30
From: Smokey
Subject: Re: Yet another broken spoke
|
On Sep 2, 11:24 am, Just A User <k...@up-yours-spammer.net > wrote:
> It happened again! I broke ANOTHER spoke on my road bike. This makes the
> second break in a month maybe a month and a half. Now I know I don't
> have the lightest riding style compared to some riders. And I am not the
> lightest of all riders. But then again I am riding on 32 triple cross
> wheels. What I don't understand is why am I breaking them on the front
> wheel only? I thought the back wheel carried more weight. So I have a
> few extra spokes I bought when I had the wheel at the lbs for the last
> spoke replacement. But now I am thinking that a new / better machine
> built wheel, or cough, a handbuilt wheels might be a more reliable way
> to go. When I say handbuilt, I mean with my hands, that have no
> experience building wheels. All opinions welcome.
>
> J.A.U.
Just another opinion, but I cured all my spoke breakage problems by
getting a hand-built set of wheels four years ago. I've never broken a
spoke and haven't even had to re-true them once. They cost around $225
if memory serves me correctly. They were built on Ultegra hubs with
Mavic CXP-33 rims and a 36 spoke 3X pattern. I ride on rough
washboarded gravel roads and a lot of rough chip seal road. There are
lots of good builders around, including our own Pete Chisholm, Peter
White, and several others. A good set of hand-built wheels will give
you many years of service.
Smokey
|
| |
Date: 02 Sep 2007 20:22:50
From: landotter
Subject: Re: Yet another broken spoke
|
On Sep 2, 3:16 pm, Just A User <k...@up-yours-spammer.net > wrote:
> landotter wrote:
> > On Sep 2, 12:33 pm, clare at snyder.on.ca wrote:
> >> On Sun, 02 Sep 2007 17:09:07 -0000, landotter <landot...@gmail.com>
> >> wrote:
>
> >>> On Sep 2, 11:24 am, Just A User <k...@up-yours-spammer.net> wrote:
> >>>> It happened again! I broke ANOTHER spoke on my road bike. This makes the
> >>>> second break in a month maybe a month and a half. Now I know I don't
> >>>> have the lightest riding style compared to some riders. And I am not the
> >>>> lightest of all riders. But then again I am riding on 32 triple cross
> >>>> wheels. What I don't understand is why am I breaking them on the front
> >>>> wheel only? I thought the back wheel carried more weight. So I have a
> >>>> few extra spokes I bought when I had the wheel at the lbs for the last
> >>>> spoke replacement. But now I am thinking that a new / better machine
> >>>> built wheel, or cough, a handbuilt wheels might be a more reliable way
> >>>> to go. When I say handbuilt, I mean with my hands, that have no
> >>>> experience building wheels. All opinions welcome.
> >>> A front is good to learn on. Sheldon Brown's site has good
> >>> instruction. The lacing seems hard till you do it three times, then
> >>> you can do it in yer sleep.
> >>> I like to stress relieve, AKA bed the spokes into the flange, after
> >>> I've tensioned the wheel up, by putting the axle on a block of wood
> >>> and working my way around the rim, giving it a pretty hefty push. Then
> >>> retrue. Should last you a lifetime.
> >>> Take your time building up tension, and do lace it up with an electric
> >>> driver from the back side so you don't get carpal tunnel issues.
> >> And be SURE the spokes are tensioned adequately. Loose spokes break.
> >> Tight spokes don't (as a general rule of thumb)
>
> > Ja--an alternative is simply to bring the current wheel up to tension.
> > Same goes for factory wheels--I dialed in my current set 3K ago and
> > have been over hill and dale with them and still they're bang on.
> > However, the current wheels' spokes have been stressed if they are
> > currently loose, undergoing the mysterious "coat hanger" effect, so
> > still a liability. If on a budget, it's worth a shot, though.
>
> Well I think I am going to invest in a truing stand and then I will true
> it out and see how it works out for me. In the mean time I just popped
> another spoke in there and trued it out by eye. It's not perfect but
> it's good enough to ride on for a bit.
Truing stand? You don't need no steenkin' stand for a touch up--rubber
band a pencil to the stays, or use the brake pads. Now, I gotta run
and JB Weld something...
|
| |
Date: 02 Sep 2007 16:11:58
From: Peter Cole
Subject: Re: Yet another broken spoke
|
Just A User wrote:
> It happened again! I broke ANOTHER spoke on my road bike. This makes the
> second break in a month maybe a month and a half. Now I know I don't
> have the lightest riding style compared to some riders. And I am not the
> lightest of all riders. But then again I am riding on 32 triple cross
> wheels. What I don't understand is why am I breaking them on the front
> wheel only? I thought the back wheel carried more weight. So I have a
> few extra spokes I bought when I had the wheel at the lbs for the last
> spoke replacement. But now I am thinking that a new / better machine
> built wheel, or cough, a handbuilt wheels might be a more reliable way
> to go. When I say handbuilt, I mean with my hands, that have no
> experience building wheels. All opinions welcome.
>
> J.A.U.
I would just bring the wheel up to (even) tension & stress relieve it
well. If it still breaks spokes, you could respoke.
I prefer to buy machine made wheels, simply because they're cheaper than
the parts and save some time lacing. I just tension & stress relieve.
I've done that on many sets of wheels with no breakage problems.
|
| |
Date: 02 Sep 2007 18:25:00
From: landotter
Subject: Re: Yet another broken spoke
|
On Sep 2, 12:33 pm, clare at snyder.on.ca wrote:
> On Sun, 02 Sep 2007 17:09:07 -0000, landotter <landot...@gmail.com>
> wrote:
>
>
>
> >On Sep 2, 11:24 am, Just A User <k...@up-yours-spammer.net> wrote:
> >> It happened again! I broke ANOTHER spoke on my road bike. This makes the
> >> second break in a month maybe a month and a half. Now I know I don't
> >> have the lightest riding style compared to some riders. And I am not the
> >> lightest of all riders. But then again I am riding on 32 triple cross
> >> wheels. What I don't understand is why am I breaking them on the front
> >> wheel only? I thought the back wheel carried more weight. So I have a
> >> few extra spokes I bought when I had the wheel at the lbs for the last
> >> spoke replacement. But now I am thinking that a new / better machine
> >> built wheel, or cough, a handbuilt wheels might be a more reliable way
> >> to go. When I say handbuilt, I mean with my hands, that have no
> >> experience building wheels. All opinions welcome.
>
> >A front is good to learn on. Sheldon Brown's site has good
> >instruction. The lacing seems hard till you do it three times, then
> >you can do it in yer sleep.
>
> >I like to stress relieve, AKA bed the spokes into the flange, after
> >I've tensioned the wheel up, by putting the axle on a block of wood
> >and working my way around the rim, giving it a pretty hefty push. Then
> >retrue. Should last you a lifetime.
>
> >Take your time building up tension, and do lace it up with an electric
> >driver from the back side so you don't get carpal tunnel issues.
>
> And be SURE the spokes are tensioned adequately. Loose spokes break.
> Tight spokes don't (as a general rule of thumb)
Ja--an alternative is simply to bring the current wheel up to tension.
Same goes for factory wheels--I dialed in my current set 3K ago and
have been over hill and dale with them and still they're bang on.
However, the current wheels' spokes have been stressed if they are
currently loose, undergoing the mysterious "coat hanger" effect, so
still a liability. If on a budget, it's worth a shot, though.
|
| | |
Date: 02 Sep 2007 16:16:11
From: Just A User
Subject: Re: Yet another broken spoke
|
landotter wrote:
> On Sep 2, 12:33 pm, clare at snyder.on.ca wrote:
>> On Sun, 02 Sep 2007 17:09:07 -0000, landotter <landot...@gmail.com>
>> wrote:
>>
>>
>>
>>> On Sep 2, 11:24 am, Just A User <k...@up-yours-spammer.net> wrote:
>>>> It happened again! I broke ANOTHER spoke on my road bike. This makes the
>>>> second break in a month maybe a month and a half. Now I know I don't
>>>> have the lightest riding style compared to some riders. And I am not the
>>>> lightest of all riders. But then again I am riding on 32 triple cross
>>>> wheels. What I don't understand is why am I breaking them on the front
>>>> wheel only? I thought the back wheel carried more weight. So I have a
>>>> few extra spokes I bought when I had the wheel at the lbs for the last
>>>> spoke replacement. But now I am thinking that a new / better machine
>>>> built wheel, or cough, a handbuilt wheels might be a more reliable way
>>>> to go. When I say handbuilt, I mean with my hands, that have no
>>>> experience building wheels. All opinions welcome.
>>> A front is good to learn on. Sheldon Brown's site has good
>>> instruction. The lacing seems hard till you do it three times, then
>>> you can do it in yer sleep.
>>> I like to stress relieve, AKA bed the spokes into the flange, after
>>> I've tensioned the wheel up, by putting the axle on a block of wood
>>> and working my way around the rim, giving it a pretty hefty push. Then
>>> retrue. Should last you a lifetime.
>>> Take your time building up tension, and do lace it up with an electric
>>> driver from the back side so you don't get carpal tunnel issues.
>> And be SURE the spokes are tensioned adequately. Loose spokes break.
>> Tight spokes don't (as a general rule of thumb)
>
> Ja--an alternative is simply to bring the current wheel up to tension.
> Same goes for factory wheels--I dialed in my current set 3K ago and
> have been over hill and dale with them and still they're bang on.
> However, the current wheels' spokes have been stressed if they are
> currently loose, undergoing the mysterious "coat hanger" effect, so
> still a liability. If on a budget, it's worth a shot, though.
>
Well I think I am going to invest in a truing stand and then I will true
it out and see how it works out for me. In the mean time I just popped
another spoke in there and trued it out by eye. It's not perfect but
it's good enough to ride on for a bit.
|
| |
Date: 02 Sep 2007 10:46:33
From: Qui si parla Campagnolo-www.vecchios.com
Subject: Re: Yet another broken spoke
|
On Sep 2, 11:32 am, "Roger Zoul" <rogerzo...@hotmail.com > wrote:
> Just A User wrote:
>
> :: All opinions welcome.
>
> http://www.spinlitecycling.com/index.htm
They state-The Chris King is the best hub on the market and their 5
year warranty backs this claim.
Righto sparky...not even close...if shimano, the best is shimano, if
Campag, the best is Campagnolo..close second is DT..
|
| |
Date: 02 Sep 2007 10:39:46
From: Qui si parla Campagnolo-www.vecchios.com
Subject: Re: Yet another broken spoke
|
On Sep 2, 10:24 am, Just A User <k...@up-yours-spammer.net > wrote:
> It happened again! I broke ANOTHER spoke on my road bike. This makes the
> second break in a month maybe a month and a half. Now I know I don't
> have the lightest riding style compared to some riders. And I am not the
> lightest of all riders. But then again I am riding on 32 triple cross
> wheels. What I don't understand is why am I breaking them on the front
> wheel only? I thought the back wheel carried more weight. So I have a
> few extra spokes I bought when I had the wheel at the lbs for the last
> spoke replacement. But now I am thinking that a new / better machine
> built wheel, or cough, a handbuilt wheels might be a more reliable way
> to go. When I say handbuilt, I mean with my hands, that have no
> experience building wheels. All opinions welcome.
>
> J.A.U.
Can you reuse the front hub? If ya can, get some spokes and a rim and
a coupla books and build the wheel..not rocket surgery. Or take or
send the hub to somebody and have them build ya a wheel...we do this
sort of thing all the time.
|
| | |
Date: 02 Sep 2007 16:16:18
From: Just A User
Subject: Re: Yet another broken spoke
|
Qui si parla Campagnolo-www.vecchios.com wrote:
> On Sep 2, 10:24 am, Just A User <k...@up-yours-spammer.net> wrote:
>> It happened again! I broke ANOTHER spoke on my road bike. This makes the
>> second break in a month maybe a month and a half. Now I know I don't
>> have the lightest riding style compared to some riders. And I am not the
>> lightest of all riders. But then again I am riding on 32 triple cross
>> wheels. What I don't understand is why am I breaking them on the front
>> wheel only? I thought the back wheel carried more weight. So I have a
>> few extra spokes I bought when I had the wheel at the lbs for the last
>> spoke replacement. But now I am thinking that a new / better machine
>> built wheel, or cough, a handbuilt wheels might be a more reliable way
>> to go. When I say handbuilt, I mean with my hands, that have no
>> experience building wheels. All opinions welcome.
>>
>> J.A.U.
>
> Can you reuse the front hub? If ya can, get some spokes and a rim and
> a coupla books and build the wheel..not rocket surgery. Or take or
> send the hub to somebody and have them build ya a wheel...we do this
> sort of thing all the time.
>
>
Yeah the front hub looks okay, it's a cheap hub anyway. The wheel
doesn't even look that bad. I just put another spoke in it and trued it
by eye, should be good enough until I can order a truing stand and give
it a proper job.
|
| |
Date: 02 Sep 2007 12:36:00
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-02, Just A User <ken@up-yours-spammer.net > wrote:
> It happened again! I broke ANOTHER spoke on my road bike. This makes the
> second break in a month maybe a month and a half. Now I know I don't
> have the lightest riding style compared to some riders. And I am not the
> lightest of all riders. But then again I am riding on 32 triple cross
> wheels. What I don't understand is why am I breaking them on the front
> wheel only? I thought the back wheel carried more weight.
It does, which increases the evidence that your front wheel is suffering
from a poor build. All other factors seem to be equal or in its favour
(assuming same components front and rear).
> So I have a few extra spokes I bought when I had the wheel at the lbs
> for the last spoke replacement.
In a recent post, perhaps in this thread, Peter (Qui si parla) suggested
a flat spot on the rim giving the spokes around the flat spot a hard
time.
Is it the new spokes you're putting in that keep breaking again or
different ones?
If it's different ones each time, a theoretical possibility is retained
stress at the elbow from a poor original build. This would lead them to
premature fatigue failure, which is they're all now starting to fail at
around the same time.
Or it could be the wrong sort of spokes (shanks too long, or just too
cheap and nasty).
> But now I am thinking that a new / better machine built wheel, or
> cough, a handbuilt wheels might be a more reliable way to go. When I
> say handbuilt, I mean with my hands, that have no experience building
> wheels. All opinions welcome.
Why not, give it a go. The Sheldon Brown page is all you need
(http://www.sheldonbrown.com/wheelbuild.html), but Jobst's book (The
Bicycle Wheel) is also highly regarded.
Or, if the rim seems OK (i.e. not got a big flat spot or other
deformity), get a whole new set of spokes and rebuild with those but the
same hub and rim.
|
| | |
Date: 02 Sep 2007 16:16:29
From: Just A User
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-02, Just A User <ken@up-yours-spammer.net> wrote:
>> It happened again! I broke ANOTHER spoke on my road bike. This makes the
>> second break in a month maybe a month and a half. Now I know I don't
>> have the lightest riding style compared to some riders. And I am not the
>> lightest of all riders. But then again I am riding on 32 triple cross
>> wheels. What I don't understand is why am I breaking them on the front
>> wheel only? I thought the back wheel carried more weight.
>
> It does, which increases the evidence that your front wheel is suffering
> from a poor build. All other factors seem to be equal or in its favour
> (assuming same components front and rear).
>
>> So I have a few extra spokes I bought when I had the wheel at the lbs
>> for the last spoke replacement.
>
> In a recent post, perhaps in this thread, Peter (Qui si parla) suggested
> a flat spot on the rim giving the spokes around the flat spot a hard
> time.
>
> Is it the new spokes you're putting in that keep breaking again or
> different ones?
>
> If it's different ones each time, a theoretical possibility is retained
> stress at the elbow from a poor original build. This would lead them to
> premature fatigue failure, which is they're all now starting to fail at
> around the same time.
>
> Or it could be the wrong sort of spokes (shanks too long, or just too
> cheap and nasty).
>
>> But now I am thinking that a new / better machine built wheel, or
>> cough, a handbuilt wheels might be a more reliable way to go. When I
>> say handbuilt, I mean with my hands, that have no experience building
>> wheels. All opinions welcome.
>
> Why not, give it a go. The Sheldon Brown page is all you need
> (http://www.sheldonbrown.com/wheelbuild.html), but Jobst's book (The
> Bicycle Wheel) is also highly regarded.
>
> Or, if the rim seems OK (i.e. not got a big flat spot or other
> deformity), get a whole new set of spokes and rebuild with those but the
> same hub and rim.
I just took the wheel apart and looked at it, the wheel looks okay but a
flat spot might be kind of hard to see. So I just popped another spoke
in it and trued it by eye. Should be good enough for now until I can
order a truing stand and give it a proper work over.
|
| |
Date: 03 Sep 2007 03:23:47
From: daveornee
Subject: Re: Yet another broken spoke
|
Just A User Wrote:
> It happened again! I broke ANOTHER spoke on my road bike. This make
> the
> second break in a month maybe a month and a half. Now I know I don't
> have the lightest riding style compared to some riders. And I am no
> the
> lightest of all riders. But then again I am riding on 32 triple cross
> wheels. What I don't understand is why am I breaking them on the front
> wheel only? I thought the back wheel carried more weight. So I have a
> few extra spokes I bought when I had the wheel at the lbs for the last
> spoke replacement. But now I am thinking that a new / better machine
> built wheel, or cough, a handbuilt wheels might be a more reliable way
> to go. When I say handbuilt, I mean with my hands, that have no
> experience building wheels. All opinions welcome.
>
> J.A.U.
Quality spokes and a quality build will help lengthen the life of th
spokes.
The time it takes for an experienced builder may be a good investment.
It depends on you inclination, mechanical aptitude, budget, and how yo
would like to spend your time.
Barnetts (the bicycle mechanic school) has dedicated a chapter to th
subject, and Jobst Brandt has a whole book "The Bicycle Wheel".
I like to build wheels, but many people think it is a waste of time an
effort when you can just buy the finished product. You can often buy
completely built wheel for less than you can buy the same parts tha
make up the wheel
--
daveornee
|
| | |
Date: 03 Sep 2007 14:00:53
From: Michael Press
Subject: Re: Yet another broken spoke
|
In article
<daveornee.2wan50@no-mx.forums.cyclingforums.com >,
daveornee
<daveornee.2wan50@no-mx.forums.cyclingforums.com >
wrote:
> Just A User Wrote:
> > It happened again! I broke ANOTHER spoke on my road bike. This makes
> > the
> > second break in a month maybe a month and a half. Now I know I don't
> > have the lightest riding style compared to some riders. And I am not
> > the
> > lightest of all riders. But then again I am riding on 32 triple cross
> > wheels. What I don't understand is why am I breaking them on the front
> > wheel only? I thought the back wheel carried more weight. So I have a
> > few extra spokes I bought when I had the wheel at the lbs for the last
> > spoke replacement. But now I am thinking that a new / better machine
> > built wheel, or cough, a handbuilt wheels might be a more reliable way
> > to go. When I say handbuilt, I mean with my hands, that have no
> > experience building wheels. All opinions welcome.
> >
> > J.A.U.
> Quality spokes and a quality build will help lengthen the life of the
> spokes.
> The time it takes for an experienced builder may be a good investment.
> It depends on you inclination, mechanical aptitude, budget, and how you
> would like to spend your time.
> Barnetts (the bicycle mechanic school) has dedicated a chapter to the
> subject, and Jobst Brandt has a whole book "The Bicycle Wheel".
> I like to build wheels, but many people think it is a waste of time and
> effort when you can just buy the finished product. You can often buy a
> completely built wheel for less than you can buy the same parts that
> make up the wheel.
Then if you buy the wheels with good parts, you can
lubricate the threads, retension, stress relieve, and
true. Also repack the bearings.
--
Michael Press
|
| | |
Date: 02 Sep 2007 16:16:23
From: Just A User
Subject: Re: Yet another broken spoke
|
daveornee wrote:
> Just A User Wrote:
>> It happened again! I broke ANOTHER spoke on my road bike. This makes
>> the
>> second break in a month maybe a month and a half. Now I know I don't
>> have the lightest riding style compared to some riders. And I am not
>> the
>> lightest of all riders. But then again I am riding on 32 triple cross
>> wheels. What I don't understand is why am I breaking them on the front
>> wheel only? I thought the back wheel carried more weight. So I have a
>> few extra spokes I bought when I had the wheel at the lbs for the last
>> spoke replacement. But now I am thinking that a new / better machine
>> built wheel, or cough, a handbuilt wheels might be a more reliable way
>> to go. When I say handbuilt, I mean with my hands, that have no
>> experience building wheels. All opinions welcome.
>>
>> J.A.U.
> Quality spokes and a quality build will help lengthen the life of the
> spokes.
> The time it takes for an experienced builder may be a good investment.
> It depends on you inclination, mechanical aptitude, budget, and how you
> would like to spend your time.
> Barnetts (the bicycle mechanic school) has dedicated a chapter to the
> subject, and Jobst Brandt has a whole book "The Bicycle Wheel".
> I like to build wheels, but many people think it is a waste of time and
> effort when you can just buy the finished product. You can often buy a
> completely built wheel for less than you can buy the same parts that
> make up the wheel.
>
>
Well I think I am going to invest in a truing stand, it seems like I am
always having issues with spokes and wheels. So it would probably be a
good investment for me. I have read that handbuilt wheels are generally
more reliable than machine built wheels.
|
| |
Date: 02 Sep 2007 13:32:23
From: Roger Zoul
Subject: Re: Yet another broken spoke
|
Just A User wrote:
:: All opinions welcome.
http://www.spinlitecycling.com/index.htm
|
| |
Date: 02 Sep 2007 10:18:43
From: Chocobot
Subject: Re: Yet another broken spoke
|
On Sep 2, 12:24 pm, Just A User <k...@up-yours-spammer.net > wrote:
> built wheel, or cough, a handbuilt wheels might be a more reliable way
> to go. When I say handbuilt, I mean with my hands, that have no
> experience building wheels. All opinions welcome.
>
> J.A.U.
Handbuilding your own wheels is always a good idea, and if you do them
yourself and something goes wrong, it may give you some insight as to
what is happening, such as, oh, that spoke was twisted too much when
building the wheel up, or it had a very awkward tension compared to
the other spokes. I am heavier than most avid cyclist, but have never
broken a spoke. I ride 32 3x and don't even have a spoke preference,
but usually use dt swiss double butted.
|
| |
Date: 02 Sep 2007 17:09:07
From: landotter
Subject: Re: Yet another broken spoke
|
On Sep 2, 11:24 am, Just A User <k...@up-yours-spammer.net > wrote:
> It happened again! I broke ANOTHER spoke on my road bike. This makes the
> second break in a month maybe a month and a half. Now I know I don't
> have the lightest riding style compared to some riders. And I am not the
> lightest of all riders. But then again I am riding on 32 triple cross
> wheels. What I don't understand is why am I breaking them on the front
> wheel only? I thought the back wheel carried more weight. So I have a
> few extra spokes I bought when I had the wheel at the lbs for the last
> spoke replacement. But now I am thinking that a new / better machine
> built wheel, or cough, a handbuilt wheels might be a more reliable way
> to go. When I say handbuilt, I mean with my hands, that have no
> experience building wheels. All opinions welcome.
A front is good to learn on. Sheldon Brown's site has good
instruction. The lacing seems hard till you do it three times, then
you can do it in yer sleep.
I like to stress relieve, AKA bed the spokes into the flange, after
I've tensioned the wheel up, by putting the axle on a block of wood
and working my way around the rim, giving it a pretty hefty push. Then
retrue. Should last you a lifetime.
Take your time building up tension, and do lace it up with an electric
driver from the back side so you don't get carpal tunnel issues.
|
| | |
Date: 02 Sep 2007 13:33:18
From:
Subject: Re: Yet another broken spoke
|
On Sun, 02 Sep 2007 17:09:07 -0000, landotter <landotter@gmail.com >
wrote:
>On Sep 2, 11:24 am, Just A User <k...@up-yours-spammer.net> wrote:
>> It happened again! I broke ANOTHER spoke on my road bike. This makes the
>> second break in a month maybe a month and a half. Now I know I don't
>> have the lightest riding style compared to some riders. And I am not the
>> lightest of all riders. But then again I am riding on 32 triple cross
>> wheels. What I don't understand is why am I breaking them on the front
>> wheel only? I thought the back wheel carried more weight. So I have a
>> few extra spokes I bought when I had the wheel at the lbs for the last
>> spoke replacement. But now I am thinking that a new / better machine
>> built wheel, or cough, a handbuilt wheels might be a more reliable way
>> to go. When I say handbuilt, I mean with my hands, that have no
>> experience building wheels. All opinions welcome.
>
>A front is good to learn on. Sheldon Brown's site has good
>instruction. The lacing seems hard till you do it three times, then
>you can do it in yer sleep.
>
>I like to stress relieve, AKA bed the spokes into the flange, after
>I've tensioned the wheel up, by putting the axle on a block of wood
>and working my way around the rim, giving it a pretty hefty push. Then
>retrue. Should last you a lifetime.
>
>Take your time building up tension, and do lace it up with an electric
>driver from the back side so you don't get carpal tunnel issues.
>
And be SURE the spokes are tensioned adequately. Loose spokes break.
Tight spokes don't (as a general rule of thumb)
--
Posted via a free Usenet account from http://www.teranews.com
|
| | | |
Date: 07 Sep 2007 03:19:53
From:
Subject: Re: Yet another broken spoke
|
On Sep 6, 9:23 pm, carlfo...@comcast.net wrote:
> On Thu, 06 Sep 2007 18:15:00 -0700, SocSecTrainWr...@earthlink.net
> wrote:
>
> >On Sep 4, 8:24 pm, carlfo...@comcast.net wrote:
>
> >> The spokes lose huge amounts of pre-tension as they xxrollxx ROTATE under the
> >> xxwheelxx HUB. The individual the spokes all the way around the wheel show an
> >> increase of only up to 10% in tension, compared to the spoke directly
> >> under the axle's loss of tension.
>
> >And in your testing, as well as
> >everyone else's, the greatest xxlossxx GAIN of tension was in the spokes
> >perpendicular to the spokes that lost tension.
>
> I have never posted any test of tension loss as spokes roll under the
> wheel.
Thanks for proofreading my post.
|
| | | |
Date: 03 Sep 2007 02:19:47
From:
Subject: Re: Yet another broken spoke
|
Clare who? writes:
> And be SURE the spokes are tensioned adequately. Loose spokes break.
> Tight spokes don't (as a general rule of thumb)
I keep seeing this admonition yet no one seems to be able to describe
the mechanism that causes such spoke failures. Loosely spoked wheels
can allow the nipples to unscrew and cause wheel misalignment, but
spoke failure is caused by metal fatigue that arises from tension
change, caused once with every wheel rotation as spokes pass through
the zone of tire contact with the road. This must occur with stress
near the yield stress, something that does not readily occur in loose
spokes.
Please explain.
Jobst Brandt
|
| | | | |
Date: 03 Sep 2007 00:18:14
From:
Subject: Re: Yet another broken spoke
|
On 03 Sep 2007 02:19:47 GMT, jobst.brandt@stanfordalumni.org wrote:
>Clare who? writes:
>
>> And be SURE the spokes are tensioned adequately. Loose spokes break.
>> Tight spokes don't (as a general rule of thumb)
>
>I keep seeing this admonition yet no one seems to be able to describe
>the mechanism that causes such spoke failures. Loosely spoked wheels
>can allow the nipples to unscrew and cause wheel misalignment, but
>spoke failure is caused by metal fatigue that arises from tension
>change, caused once with every wheel rotation as spokes pass through
>the zone of tire contact with the road. This must occur with stress
>near the yield stress, something that does not readily occur in loose
>spokes.
>
>Please explain.
>
>Jobst Brandt
A properly tensioned spoke is "pre stretched" and does not flex or
stretch in operation. A loose spoke bends at leat twice every
revolution, and stretches repeatedly. This is what fatigues a spoke
and breaks it.
--
Posted via a free Usenet account from http://www.teranews.com
|
| | | | | |
Date: 03 Sep 2007 05:36:32
From:
Subject: Re: Yet another broken spoke
|
Clare who? writes:
>>> And be SURE the spokes are tensioned adequately. Loose spokes break.
>>> Tight spokes don't (as a general rule of thumb)
>> I keep seeing this admonition yet no one seems to be able to describe
>> the mechanism that causes such spoke failures. Loosely spoked wheels
>> can allow the nipples to unscrew and cause wheel misalignment, but
>> spoke failure is caused by metal fatigue that arises from tension
>> change, caused once with every wheel rotation as spokes pass through
>> the zone of tire contact with the road. This must occur with stress
>> near the yield stress, something that does not readily occur in loose
>> spokes.
>> Please explain.
> A properly tensioned spoke is "pre stretched" and does not flex or
> stretch in operation. A loose spoke bends at least twice every
> revolution, and stretches repeatedly. This is what fatigues a spoke
> and breaks it.
Please explain what bends the spokes. Rim deflection is a few
thousandths of an inch, the spoke holes in the flange have 10 to 20
thousandths clearance and spoke nipples much more. Where is this
fatiguing compression force arising? Spokes do not go into column
buckling when slack.
I have a feeling the concept requires some exaggerated model of a
spoke that is less than properly tight. The bending of which you
speak cannot occur and cause fatiguing stress. To do that the bend
would need to approach yield (permanent deformation). To see what
that is, try how much of a bend it takes to put a bend in a spoke by
manually using it as a walking cane.
Jobst Brandt
|
| | | | | | |
Date: 03 Sep 2007 22:57:00
From:
Subject: Re: Yet another broken spoke
|
On 03 Sep 2007 05:36:32 GMT, jobst.brandt@stanfordalumni.org wrote:
>Clare who? writes:
>
>>>> And be SURE the spokes are tensioned adequately. Loose spokes break.
>>>> Tight spokes don't (as a general rule of thumb)
>
>>> I keep seeing this admonition yet no one seems to be able to describe
>>> the mechanism that causes such spoke failures. Loosely spoked wheels
>>> can allow the nipples to unscrew and cause wheel misalignment, but
>>> spoke failure is caused by metal fatigue that arises from tension
>>> change, caused once with every wheel rotation as spokes pass through
>>> the zone of tire contact with the road. This must occur with stress
>>> near the yield stress, something that does not readily occur in loose
>>> spokes.
>
>>> Please explain.
>
>> A properly tensioned spoke is "pre stretched" and does not flex or
>> stretch in operation. A loose spoke bends at least twice every
>> revolution, and stretches repeatedly. This is what fatigues a spoke
>> and breaks it.
>
>Please explain what bends the spokes. Rim deflection is a few
>thousandths of an inch, the spoke holes in the flange have 10 to 20
>thousandths clearance and spoke nipples much more. Where is this
>fatiguing compression force arising? Spokes do not go into column
>buckling when slack.
>
I used the wrong terminology - they do not so much bend as flex or
"stretch" but that stretch DOES allow the bend where the spoke goes
through the hub to actually fles, or bend - and THAT is where the
spoke usually breaks, isn't it????
>I have a feeling the concept requires some exaggerated model of a
>spoke that is less than properly tight. The bending of which you
>speak cannot occur and cause fatiguing stress. To do that the bend
>would need to approach yield (permanent deformation). To see what
>that is, try how much of a bend it takes to put a bend in a spoke by
>manually using it as a walking cane.
>
>Jobst Brandt
Does happen.
--
Posted via a free Usenet account from http://www.teranews.com
|
| | | | | | | |
Date: 05 Sep 2007 23:10:30
From: Gary Young
Subject: Re: Yet another broken spoke
|
On Wed, 05 Sep 2007 20:59:17 -0700, jim beam wrote:
> jobst.brandt@stanfordalumni.org wrote:
>> clare who? writes:
>>
>>>>>> Loose spokes also wear the holes in the hubs - and wear the
>>>>>> spokes where they go through the hub.
>>
>>>>> I hadn't thought of that. That would explain the phenomenon
>>>>> (loose spokes breaking) in a way that's consistent with my
>>>>> understanding of Jobst's earlier suggestion that there is a bit of
>>>>> clearance down there.
>>
>>>> You'll have to show some evidence of loose spokes wearing thin at
>>>> the elbow. That has not been observed by anyone building wheels
>>>> around here and I've been watching this sort of thing for more
>>>> years than most. Spoke failures are from residual stress and
>>>> stress concentrations, not loose spokes or flexing from
>>>> interleaving.
>>
>>> I just threw out a couple spokes I pulled from a 1970 CCM that were
>>> worn noticeably - and ONE of them was broken.Same on a 1963 Schwinn
>>> American that had sat for about 15 years. Replaced 6 spokes on that
>>> one.Only one was initially broken.
>>
>> You say "noticeably". What did you notice other than a clean area
>> where the spokes contacted the flange?
>>
>>> All the spokes were loose on all 4 wheels.
>>
>> Your experience being different from the norm, how about some pictures
>> of these worn spokes? How much wear did they have? How much was the
>> spoke cross section reduced from the original? As I said, no one I
>> know in the wheel building business has observed such wear, so it
>> makes your findings unusual enough to be questioned. Something that
>> could be resolved with some photos of the worn spokes.
>>
>
> but you have admitted to existence of this phenomenon in other writings
> - why bullshit and deny now?
>
> http://groups.google.com/group/rec.bicycles.tech/msg/d7dd514160221d16
>
> "These are typically a fretting notch where they cross,
> such that if you slide them apart with the fingers, they pop out of
> engagement and readily snap back in"
The discussion is about fretting at spoke elbows.
|
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Date: 06 Sep 2007 02:29:51
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-06, Gary Young <garyyoung3@gmail.com > wrote:
> On Wed, 05 Sep 2007 20:59:17 -0700, jim beam wrote:
[...]
>> but you have admitted to existence of this phenomenon in other writings
>> - why bullshit and deny now?
>>
>> http://groups.google.com/group/rec.bicycles.tech/msg/d7dd514160221d16
>>
>> "These are typically a fretting notch where they cross,
>> such that if you slide them apart with the fingers, they pop out of
>> engagement and readily snap back in"
>
> The discussion is about fretting at spoke elbows.
Indeed, but why not? If they fret at the crossing why not at the elbow
(if they're too loose)?
|
| | | | | | | |
Date: 04 Sep 2007 17:28:33
From:
Subject: Re: Yet another broken spoke
|
Clare who? writes:
>>>>> And be SURE the spokes are tensioned adequately. Loose spokes
>>>>> break. Tight spokes don't (as a general rule of thumb)
>>>> I keep seeing this admonition yet no one seems to be able to
>>>> describe the mechanism that causes such spoke failures. Loosely
>>>> spoked wheels can allow the nipples to unscrew and cause wheel
>>>> misalignment, but spoke failure is caused by metal fatigue that
>>>> arises from tension change, caused once with every wheel rotation
>>>> as spokes pass through the zone of tire contact with the road.
>>>> This must occur with stress near the yield stress, something that
>>>> does not readily occur in loose spokes.
>>>> Please explain.
>>> A properly tensioned spoke is "pre stretched" and does not flex or
>>> stretch in operation. A loose spoke bends at least twice every
>>> revolution, and stretches repeatedly. This is what fatigues a
>>> spoke and breaks it.
>> Please explain what bends the spokes. Rim deflection is a few
>> thousandths of an inch, the spoke holes in the flange have 10 to 20
>> thousandths clearance and spoke nipples much more. Where is this
>> fatiguing compression force arising? Spokes do not go into column
>> buckling when slack.
> I used the wrong terminology - they do not so much bend as flex or
> "stretch" but that stretch DOES allow the bend where the spoke goes
> through the hub to actually flex, or bend - and THAT is where the
> spoke usually breaks, isn't it????
What you haven't explained is where force makes loose spokes break
more readily than properly tensioned ones. That the elbow is a place
of residual stress from manufacture and installation has been
discussed here often. The stress in the elbow of a looser spoke is
lower than in one that has more tension and this stress can only go to
zero if the spoke becomes slack. With a tighter spoke the stress
variation can have a larger excursion than that of a looser spoke. It
is cyclic stress changes that causes failure.
>> I have a feeling the concept requires some exaggerated model of a
>> spoke that is less than properly tight. The bending of which you
>> speak cannot occur and cause fatiguing stress. To do that the bend
>> would need to approach yield (permanent deformation). To see what
>> that is, try how much of a bend it takes to put a bend in a spoke
>> by manually using it as a walking cane.
Spoke failure in fewer than 10,000 miles, for instance is short term
fatigue and is caused by residual stress in stress concentration
locations such as threads and spoke elbows. These tresses must be
relieved after the wheel is tensioned.
Jobst Brandt
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Date: 04 Sep 2007 15:35:56
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-04, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org > wrote:
[...]
> With a tighter spoke the stress variation can have a larger excursion
> than that of a looser spoke.
Why?
Just to clarify: suppose I plot a graph of stress against time for a
spoke on a wheel on a bicycle that's being ridden down the road. I
expect the graph would be some kind of wave, going up and down as the
spoke passes over the contact patch.
By "larger excursion" do you mean that this wave would have a greater
amplitude?
Perhaps I'm being stupid but I don't see why you would get a larger
amplitude for a tighter spoke.
|
| | | | | | | | | |
Date: 05 Sep 2007 01:49:40
From:
Subject: Re: Yet another broken spoke
|
Ben C? writes surreptitiously:
>> With a tighter spoke the stress variation can have a larger excursion
>> than that of a looser spoke.
> Why?
Because the loose spoke can only go from its insufficient tension to
zero while the more highly tensioned one can vary from its full
tension to the reduction caused by the load. This is greater than the
loose spoke stress cycle and at a higher average stress.
> Just to clarify: suppose I plot a graph of stress against time for a
> spoke on a wheel on a bicycle that's being ridden down the road. I
> expect the graph would be some kind of wave, going up and down as
> the spoke passes over the contact patch.
It is not a wave. It is a straight line with a once-around dip in it
for a short duration while the spoke is pointing (straight down) into
the tire-to-road contact patch and a bit more.
> By "larger excursion" do you mean that this wave would have a
> greater amplitude?
> Perhaps I'm being stupid but I don't see why you would get a larger
> amplitude for a tighter spoke.
Jobst Brandt
|
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Date: 05 Sep 2007 02:29:16
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-05, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org > wrote:
> Ben C? writes surreptitiously:
>
>>> With a tighter spoke the stress variation can have a larger excursion
>>> than that of a looser spoke.
>
>> Why?
>
> Because the loose spoke can only go from its insufficient tension to
> zero while the more highly tensioned one can vary from its full
> tension to the reduction caused by the load. This is greater than the
> loose spoke stress cycle and at a higher average stress.
Thanks. That is also how Carl explained it.
|
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Date: 05 Sep 2007 05:45:12
From: jim beam
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-05, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org> wrote:
>> Ben C? writes surreptitiously:
>>
>>>> With a tighter spoke the stress variation can have a larger excursion
>>>> than that of a looser spoke.
>>> Why?
>> Because the loose spoke can only go from its insufficient tension to
>> zero while the more highly tensioned one can vary from its full
>> tension to the reduction caused by the load. This is greater than the
>> loose spoke stress cycle and at a higher average stress.
>
> Thanks. That is also how Carl explained it.
shame that doesn't account for the full bending cycle though...
|
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Date: 04 Sep 2007 17:33:52
From:
Subject: Re: Yet another broken spoke
|
On Tue, 04 Sep 2007 15:35:56 -0500, Ben C <spamspam@spam.eggs > wrote:
>On 2007-09-04, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org> wrote:
>[...]
>> With a tighter spoke the stress variation can have a larger excursion
>> than that of a looser spoke.
>
>Why?
>
>Just to clarify: suppose I plot a graph of stress against time for a
>spoke on a wheel on a bicycle that's being ridden down the road. I
>expect the graph would be some kind of wave, going up and down as the
>spoke passes over the contact patch.
>
>By "larger excursion" do you mean that this wave would have a greater
>amplitude?
>
>Perhaps I'm being stupid but I don't see why you would get a larger
>amplitude for a tighter spoke.
Dear Ben,
A spoke cannot lose more than its pre-tension, so the pre-tension is
the limit of how much its tension can vary. The higher the initial
tension, the greater the possible range of tension change.
First, consider two spokes, one tensioned to 200 pounds, one to only
100 pounds, on a bicycle where rolling under the axle causes a maxium
loss of 50 pounds of tension.
The excursion, or tension loss, will be the same, with one varying
from 200 down to 150 pounds, the other from 100 down to 50 pounds.
Technically, neither spoke is ever loose--both spokes are always under
tension, so both experience the same 50 pound tension change.
But now let the bike hit some bumps at speed, hard enough to cause a
maximum 120 pound loss of tension.
The first spoke, pre-tensioned to 200 pounds, can still lose 120
pounds of pre-tension, dropping from 200 down to 80.
But the other spoke can only drop from 100 pounds of pre-tension down
to 0. After it loses only 100 pounds of tension, it just rattles.
Cheers,
Carl Fogel
|
| | | | | | | | | | |
Date: 05 Sep 2007 02:19:47
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-04, carlfogel@comcast.net <carlfogel@comcast.net > wrote:
> On Tue, 04 Sep 2007 15:35:56 -0500, Ben C <spamspam@spam.eggs> wrote:
>
>>On 2007-09-04, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org> wrote:
>>[...]
>>> With a tighter spoke the stress variation can have a larger excursion
>>> than that of a looser spoke.
>>
>>Why?
>>
>>Just to clarify: suppose I plot a graph of stress against time for a
>>spoke on a wheel on a bicycle that's being ridden down the road. I
>>expect the graph would be some kind of wave, going up and down as the
>>spoke passes over the contact patch.
>>
>>By "larger excursion" do you mean that this wave would have a greater
>>amplitude?
>>
>>Perhaps I'm being stupid but I don't see why you would get a larger
>>amplitude for a tighter spoke.
>
> Dear Ben,
>
> A spoke cannot lose more than its pre-tension, so the pre-tension is
> the limit of how much its tension can vary. The higher the initial
> tension, the greater the possible range of tension change.
>
> First, consider two spokes, one tensioned to 200 pounds, one to only
> 100 pounds, on a bicycle where rolling under the axle causes a maxium
> loss of 50 pounds of tension.
>
> The excursion, or tension loss, will be the same, with one varying
> from 200 down to 150 pounds, the other from 100 down to 50 pounds.
>
> Technically, neither spoke is ever loose--both spokes are always under
> tension, so both experience the same 50 pound tension change.
>
> But now let the bike hit some bumps at speed, hard enough to cause a
> maximum 120 pound loss of tension.
>
> The first spoke, pre-tensioned to 200 pounds, can still lose 120
> pounds of pre-tension, dropping from 200 down to 80.
>
> But the other spoke can only drop from 100 pounds of pre-tension down
> to 0. After it loses only 100 pounds of tension, it just rattles.
I get it! Thanks.
Of course whether it does rattle harmlessly or flex horribly, rapidly
fatiguing itself to death, is another matter.
|
| | | | | | | | | | | |
Date: 05 Sep 2007 09:22:13
From: Peter Cole
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-04, carlfogel@comcast.net <carlfogel@comcast.net> wrote:
>> But the other spoke can only drop from 100 pounds of pre-tension down
>> to 0. After it loses only 100 pounds of tension, it just rattles.
>
> I get it! Thanks.
>
> Of course whether it does rattle harmlessly or flex horribly, rapidly
> fatiguing itself to death, is another matter.
It could only "flex horribly" (or at all) if the spoke was bowed. Even
in that case, you'd have to consider where the flex occurred vs where
the spokes broke. The "flexing horribly" speculation also needs to
consider the actual amount of rim deflection which bounds the degree of
"horribleness".
A worst case scenario would be where the spoke elbow angle did not match
the angle of the spoke hole to flange. In that case, fluctuations in
tension could cause elbow bending when the overall tension wasn't high
enough to keep the spoke fully supported. To have that happen the
angular mismatch would have had to survived the initial wheel tensioning
and stress relief. If a wheel was built with low tension and not stress
relieved, and a spoke subsequently became loose enough to lose support
at the elbow, it might bend enough to fatigue rapidly, but I would
consider this to be the consequence of a bad initial build rather than a
loose spoke per se.
|
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Date: 05 Sep 2007 06:29:32
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> Ben C wrote:
>> On 2007-09-04, carlfogel@comcast.net <carlfogel@comcast.net> wrote:
>
>>> But the other spoke can only drop from 100 pounds of pre-tension down
>>> to 0. After it loses only 100 pounds of tension, it just rattles.
>>
>> I get it! Thanks.
>>
>> Of course whether it does rattle harmlessly or flex horribly, rapidly
>> fatiguing itself to death, is another matter.
>
> It could only "flex horribly" (or at all) if the spoke was bowed. Even
> in that case, you'd have to consider where the flex occurred vs where
> the spokes broke. The "flexing horribly" speculation also needs to
> consider the actual amount of rim deflection which bounds the degree of
> "horribleness".
>
> A worst case scenario would be where the spoke elbow angle did not match
> the angle of the spoke hole to flange. In that case, fluctuations in
> tension could cause elbow bending when the overall tension wasn't high
> enough to keep the spoke fully supported. To have that happen the
> angular mismatch would have had to survived the initial wheel tensioning
> and stress relief. If a wheel was built with low tension and not stress
> relieved, and a spoke subsequently became loose enough to lose support
> at the elbow, it might bend enough to fatigue rapidly, but I would
> consider this to be the consequence of a bad initial build rather than a
> loose spoke per se.
wow! how to admit something you've previously denied, while phrasing it
as further denial!!! quite masterful.
|
| | | | | | | | | | | | | |
Date: 05 Sep 2007 10:41:50
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> Ben C wrote:
>>> On 2007-09-04, carlfogel@comcast.net <carlfogel@comcast.net> wrote:
>>
>>>> But the other spoke can only drop from 100 pounds of pre-tension down
>>>> to 0. After it loses only 100 pounds of tension, it just rattles.
>>>
>>> I get it! Thanks.
>>>
>>> Of course whether it does rattle harmlessly or flex horribly, rapidly
>>> fatiguing itself to death, is another matter.
>>
>> It could only "flex horribly" (or at all) if the spoke was bowed. Even
>> in that case, you'd have to consider where the flex occurred vs where
>> the spokes broke. The "flexing horribly" speculation also needs to
>> consider the actual amount of rim deflection which bounds the degree
>> of "horribleness".
>>
>> A worst case scenario would be where the spoke elbow angle did not
>> match the angle of the spoke hole to flange. In that case,
>> fluctuations in tension could cause elbow bending when the overall
>> tension wasn't high enough to keep the spoke fully supported. To have
>> that happen the angular mismatch would have had to survived the
>> initial wheel tensioning and stress relief. If a wheel was built with
>> low tension and not stress relieved, and a spoke subsequently became
>> loose enough to lose support at the elbow, it might bend enough to
>> fatigue rapidly, but I would consider this to be the consequence of a
>> bad initial build rather than a loose spoke per se.
>
> wow! how to admit something you've previously denied, while phrasing it
> as further denial!!! quite masterful.
Only in your world. In the first paragraph, I was referring to the spoke
bending along its whole length, the second only at the elbow -- in case
that wasn't clear.
I think the burden is on you to explain how the spoke elbow is
unsupported (or how it can bend if it isn't).
|
| | | | | | | | | | | | | | |
Date: 05 Sep 2007 20:56:58
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> Ben C wrote:
>>>> On 2007-09-04, carlfogel@comcast.net <carlfogel@comcast.net> wrote:
>>>
>>>>> But the other spoke can only drop from 100 pounds of pre-tension down
>>>>> to 0. After it loses only 100 pounds of tension, it just rattles.
>>>>
>>>> I get it! Thanks.
>>>>
>>>> Of course whether it does rattle harmlessly or flex horribly, rapidly
>>>> fatiguing itself to death, is another matter.
>>>
>>> It could only "flex horribly" (or at all) if the spoke was bowed.
>>> Even in that case, you'd have to consider where the flex occurred vs
>>> where the spokes broke. The "flexing horribly" speculation also needs
>>> to consider the actual amount of rim deflection which bounds the
>>> degree of "horribleness".
>>>
>>> A worst case scenario would be where the spoke elbow angle did not
>>> match the angle of the spoke hole to flange. In that case,
>>> fluctuations in tension could cause elbow bending when the overall
>>> tension wasn't high enough to keep the spoke fully supported. To have
>>> that happen the angular mismatch would have had to survived the
>>> initial wheel tensioning and stress relief. If a wheel was built with
>>> low tension and not stress relieved, and a spoke subsequently became
>>> loose enough to lose support at the elbow, it might bend enough to
>>> fatigue rapidly, but I would consider this to be the consequence of a
>>> bad initial build rather than a loose spoke per se.
>>
>> wow! how to admit something you've previously denied, while phrasing
>> it as further denial!!! quite masterful.
>
> Only in your world. In the first paragraph, I was referring to the spoke
> bending along its whole length, the second only at the elbow -- in case
> that wasn't clear.
>
> I think the burden is on you to explain how the spoke elbow is
> unsupported (or how it can bend if it isn't).
er, the light gap between the hub and the spoke ought to be proof to
anyone whose intent is not to bullshit and deceive...
|
| | | | | | | | | | | | | | | |
Date: 06 Sep 2007 16:05:30
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>>> Ben C wrote:
>>>>> On 2007-09-04, carlfogel@comcast.net <carlfogel@comcast.net> wrote:
>>>>
>>>>>> But the other spoke can only drop from 100 pounds of pre-tension down
>>>>>> to 0. After it loses only 100 pounds of tension, it just rattles.
>>>>>
>>>>> I get it! Thanks.
>>>>>
>>>>> Of course whether it does rattle harmlessly or flex horribly, rapidly
>>>>> fatiguing itself to death, is another matter.
>>>>
>>>> It could only "flex horribly" (or at all) if the spoke was bowed.
>>>> Even in that case, you'd have to consider where the flex occurred vs
>>>> where the spokes broke. The "flexing horribly" speculation also
>>>> needs to consider the actual amount of rim deflection which bounds
>>>> the degree of "horribleness".
>>>>
>>>> A worst case scenario would be where the spoke elbow angle did not
>>>> match the angle of the spoke hole to flange. In that case,
>>>> fluctuations in tension could cause elbow bending when the overall
>>>> tension wasn't high enough to keep the spoke fully supported. To
>>>> have that happen the angular mismatch would have had to survived the
>>>> initial wheel tensioning and stress relief. If a wheel was built
>>>> with low tension and not stress relieved, and a spoke subsequently
>>>> became loose enough to lose support at the elbow, it might bend
>>>> enough to fatigue rapidly, but I would consider this to be the
>>>> consequence of a bad initial build rather than a loose spoke per se.
>>>
>>> wow! how to admit something you've previously denied, while phrasing
>>> it as further denial!!! quite masterful.
>>
>> Only in your world. In the first paragraph, I was referring to the
>> spoke bending along its whole length, the second only at the elbow --
>> in case that wasn't clear.
>>
>> I think the burden is on you to explain how the spoke elbow is
>> unsupported (or how it can bend if it isn't).
>
> er, the light gap between the hub and the spoke ought to be proof to
> anyone whose intent is not to bullshit and deceive...
Why don't you compute the bending moment for that distance and compare
its contribution to skin stress to that of the static and dynamic spoke
tension and get back to us?
|
| | | | | | | | | | | | | | | | |
Date: 06 Sep 2007 21:04:29
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>> Peter Cole wrote:
>>>>> Ben C wrote:
>>>>>> On 2007-09-04, carlfogel@comcast.net <carlfogel@comcast.net> wrote:
>>>>>
>>>>>>> But the other spoke can only drop from 100 pounds of pre-tension
>>>>>>> down
>>>>>>> to 0. After it loses only 100 pounds of tension, it just rattles.
>>>>>>
>>>>>> I get it! Thanks.
>>>>>>
>>>>>> Of course whether it does rattle harmlessly or flex horribly, rapidly
>>>>>> fatiguing itself to death, is another matter.
>>>>>
>>>>> It could only "flex horribly" (or at all) if the spoke was bowed.
>>>>> Even in that case, you'd have to consider where the flex occurred
>>>>> vs where the spokes broke. The "flexing horribly" speculation also
>>>>> needs to consider the actual amount of rim deflection which bounds
>>>>> the degree of "horribleness".
>>>>>
>>>>> A worst case scenario would be where the spoke elbow angle did not
>>>>> match the angle of the spoke hole to flange. In that case,
>>>>> fluctuations in tension could cause elbow bending when the overall
>>>>> tension wasn't high enough to keep the spoke fully supported. To
>>>>> have that happen the angular mismatch would have had to survived
>>>>> the initial wheel tensioning and stress relief. If a wheel was
>>>>> built with low tension and not stress relieved, and a spoke
>>>>> subsequently became loose enough to lose support at the elbow, it
>>>>> might bend enough to fatigue rapidly, but I would consider this to
>>>>> be the consequence of a bad initial build rather than a loose spoke
>>>>> per se.
>>>>
>>>> wow! how to admit something you've previously denied, while
>>>> phrasing it as further denial!!! quite masterful.
>>>
>>> Only in your world. In the first paragraph, I was referring to the
>>> spoke bending along its whole length, the second only at the elbow --
>>> in case that wasn't clear.
>>>
>>> I think the burden is on you to explain how the spoke elbow is
>>> unsupported (or how it can bend if it isn't).
>>
>> er, the light gap between the hub and the spoke ought to be proof to
>> anyone whose intent is not to bullshit and deceive...
>
> Why don't you compute the bending moment for that distance and compare
> its contribution to skin stress to that of the static and dynamic spoke
> tension and get back to us?
why don't /you/? but i forget, you don't contribute. maybe that's a
guilt thing since you're playing this game on your employer's time, not
your own.
|
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Date: 07 Sep 2007 14:22:51
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> why don't /you/? but i forget, you don't contribute. maybe that's a
> guilt thing since you're playing this game on your employer's time, not
> your own.
That's none of your business.
|
| | | | | | | | | | | | | | | | | | |
Date: 07 Sep 2007 18:30:15
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>
>> why don't /you/? but i forget, you don't contribute. maybe that's a
>> guilt thing since you're playing this game on your employer's time,
>> not your own.
>
> That's none of your business.
it's a damned good indicator of your fundamental dishonesty though.
|
| | | | | | | | | | | | | | | | | | | |
Date: 08 Sep 2007 10:11:16
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>
>>> why don't /you/? but i forget, you don't contribute. maybe that's a
>>> guilt thing since you're playing this game on your employer's time,
>>> not your own.
>>
>> That's none of your business.
>
> it's a damned good indicator of your fundamental dishonesty though.
That the best you got?
|
| | | | | | | | | | | | | | | | | | | | |
Date: 08 Sep 2007 07:55:41
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>
>>>> why don't /you/? but i forget, you don't contribute. maybe that's
>>>> a guilt thing since you're playing this game on your employer's
>>>> time, not your own.
>>>
>>> That's none of your business.
>>
>> it's a damned good indicator of your fundamental dishonesty though.
>
> That the best you got?
there's more. but let's just focus on the facts.
|
| | | | | | | | | | | | | | | | | | | | | |
Date: 08 Sep 2007 14:33:09
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>>> jim beam wrote:
>>>>
>>>>> why don't /you/? but i forget, you don't contribute. maybe that's
>>>>> a guilt thing since you're playing this game on your employer's
>>>>> time, not your own.
>>>>
>>>> That's none of your business.
>>>
>>> it's a damned good indicator of your fundamental dishonesty though.
>>
>> That the best you got?
>
> there's more. but let's just focus on the facts.
Then why introduce (ad hominem, no less) inventions?
|
| | | | | | | | | | | | | | | | | | | | | | |
Date: 09 Sep 2007 08:20:42
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>> Peter Cole wrote:
>>>>> jim beam wrote:
>>>>>
>>>>>> why don't /you/? but i forget, you don't contribute. maybe
>>>>>> that's a guilt thing since you're playing this game on your
>>>>>> employer's time, not your own.
>>>>>
>>>>> That's none of your business.
>>>>
>>>> it's a damned good indicator of your fundamental dishonesty though.
>>>
>>> That the best you got?
>>
>> there's more. but let's just focus on the facts.
>
> Then why introduce (ad hominem, no less) inventions?
invention? you post on your employer's time. that's no invention.
|
| | | | | | | | | | | | | | | | | | | | | | | |
Date: 09 Sep 2007 13:41:24
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>>> jim beam wrote:
>>>>> Peter Cole wrote:
>>>>>> jim beam wrote:
>>>>>>
>>>>>>> why don't /you/? but i forget, you don't contribute. maybe
>>>>>>> that's a guilt thing since you're playing this game on your
>>>>>>> employer's time, not your own.
>>>>>>
>>>>>> That's none of your business.
>>>>>
>>>>> it's a damned good indicator of your fundamental dishonesty though.
>>>>
>>>> That the best you got?
>>>
>>> there's more. but let's just focus on the facts.
>>
>> Then why introduce (ad hominem, no less) inventions?
>
> invention? you post on your employer's time. that's no invention.
I'm sure if you think *real hard* you can come up with another
explanation. Or maybe not.
|
| | | | | | | | | | | | | | | | | | | | | | | | |
Date: 09 Sep 2007 21:12:35
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>> Peter Cole wrote:
>>>>> jim beam wrote:
>>>>>> Peter Cole wrote:
>>>>>>> jim beam wrote:
>>>>>>>
>>>>>>>> why don't /you/? but i forget, you don't contribute. maybe
>>>>>>>> that's a guilt thing since you're playing this game on your
>>>>>>>> employer's time, not your own.
>>>>>>>
>>>>>>> That's none of your business.
>>>>>>
>>>>>> it's a damned good indicator of your fundamental dishonesty though.
>>>>>
>>>>> That the best you got?
>>>>
>>>> there's more. but let's just focus on the facts.
>>>
>>> Then why introduce (ad hominem, no less) inventions?
>>
>> invention? you post on your employer's time. that's no invention.
>
> I'm sure if you think *real hard* you can come up with another
> explanation. Or maybe not.
you're unemployed? got competency issues?
|
| | | | | | | | | |
Date: 04 Sep 2007 17:10:49
From:
Subject: Re: Yet another broken spoke
|
On Tue, 04 Sep 2007 15:35:56 -0500, Ben C <spamspam@spam.eggs > wrote:
>On 2007-09-04, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org> wrote:
>[...]
>> With a tighter spoke the stress variation can have a larger excursion
>> than that of a looser spoke.
>
>Why?
>
>Just to clarify: suppose I plot a graph of stress against time for a
>spoke on a wheel on a bicycle that's being ridden down the road. I
>expect the graph would be some kind of wave, going up and down as the
>spoke passes over the contact patch.
>
>By "larger excursion" do you mean that this wave would have a greater
>amplitude?
>
>Perhaps I'm being stupid but I don't see why you would get a larger
>amplitude for a tighter spoke.
Because you would not. If tensioned to, say 200 lbs, and 200 lbs is
suspended from roughly8 of the 28 spokes, you might end up with
something like 250 lbs tension on any one spoke. That tension would
only change something like 60 lbs in use, and at all times the spoke
would be under a minimum of something like 140 lbs. With a 15 or 14
guage spoke,that tension would keep the spoke from fatigue.
Think of the spoke as a bolt, and read the following from
Writetool.com:
Tension Joints
The shear joint does not rely on tension in the bolt to hold parts
together. The tension joint, however, relies on the tension of the
bolt to hold two joined parts together. The greater the tension on the
bolt, the more force holding them together. Steel and most metals have
a property known as fatigue, which means that they lose strength upon
repeated loads. For example, a bolt with an ultimate strength of 1,000
lbs. will carry a load of 1,000 lbs. once. It will carry a load of 500
lbs. millions of times. It will carry a load between 500 lbs. and
1,000 lbs. for a limited number of times between 1 and 1 million,
depending on whether the load is closer to the 1,000-lbs.-value or the
500-lbs.-value. It doesn't matter how long the heavy load is carried;
it can carry 1,000 lbs. forever, as long as it is only one cycle. Most
joints are subject to variations in load that either adds or decreases
the tension in the bolt.
How can we get all of the strength we pay for, or do we assume the
bolt strength is only 500 lbs. and use twice as many bolts in the
joint? If the joint has been properly designed, the clamping surfaces
around the bolt will take almost all of the variation if the bolt is
properly tightened. In this scenario, a load of close to 1,000 lbs.
can be used because the load will not fluctuate very much. But if the
joint is not properly tightened, the joined parts will separate and
the full increase on the load will be on the fastener, which will
overload it. Or, the load could go to zero, which means it is in a
fatigue condition and the bolt will fail because of the repeated
application of a load that it could have easily carried except for the
fatigue factor. Therefore, a bolt in a tension joint will fail from
fatigue if it is not tightened enough, and it will fail from fatigue
and overload, if it is tightened beyond its ultimate strength.
In our example the bolt's ultimate strength is 1,000 lbs.; in actual
practice there is a safety factor that extends the range beyond the
1,000 lbs., before the bolt actually breaks from simple overload.
Therefore, it is extremely important that we achieve the proper
tension on the bolt-not too much and not too little.
--
Posted via a free Usenet account from http://www.teranews.com
|
| | | | | | | | | | |
Date: 05 Sep 2007 02:10:31
From:
Subject: Re: Yet another broken spoke
|
Clare who? writes:
>>> With a tighter spoke the stress variation can have a larger excursion
>>> than that of a looser spoke.
>> Why?
>> Just to clarify: suppose I plot a graph of stress against time for
>> a spoke on a wheel on a bicycle that's being ridden down the
>> road. I expect the graph would be some kind of wave, going up and
>> down as the spoke passes over the contact patch.
>> By "larger excursion" do you mean that this wave would have a
>> greater amplitude?
>> Perhaps I'm being stupid but I don't see why you would get a larger
>> amplitude for a tighter spoke.
> Because you would not. If tensioned to, say 200 lbs, and 200 lbs is
> suspended from roughly8 of the 28 spokes, you might end up with
> something like 250 lbs tension on any one spoke. That tension would
> only change something like 60 lbs in use, and at all times the spoke
> would be under a minimum of something like 140 lbs. With a 15 or 14
> guage spoke,that tension would keep the spoke from fatigue.
I think you misunderstand how loads are supported by spoked wheels.
Such wheels support loads through the spoke(s) between hub and road.
In a wooden wagon wheel, that seems obvious to most observers, but
that a tensioned wire wheel does the same is less apparent. I think
you should read about this in "the Bicycle Wheel" where the statics
and effects of supporting loads, transmitting torque and rim brake
forces, are explained in extensive detail.
Basically, spokes in a bicycle wheel do not experience an increase in
tension when a rider loads the wheel with his weight, but in contrast,
lose tension when spokes pass through the tire-to-road contact patch.
> Think of the spoke as a bolt, and read the following from
> Writetool.com:
The following has nothing to do with load distribution in spoked
wheels and is wholly inappropriate with respect to bicycle wheels.
---------------------------------------------------------------------
> Tension Joints
> The shear joint does not rely on tension in the bolt to hold parts
> together. The tension joint, however, relies on the tension of the
> bolt to hold two joined parts together. The greater the tension on
> the bolt, the more force holding them together. Steel and most
> metals have a property known as fatigue, which means that they lose
> strength upon repeated loads. For example, a bolt with an ultimate
> strength of 1,000 lbs. will carry a load of 1,000 lbs. once. It
> will carry a load of 500 lbs. millions of times. It will carry a
> load between 500 lbs. and 1,000 lbs. for a limited number of times
> between 1 and 1 million, depending on whether the load is closer to
> the 1,000-lbs.-value or the 500-lbs.-value. It doesn't matter how
> long the heavy load is carried; it can carry 1,000 lbs. forever, as
> long as it is only one cycle. Most joints are subject to variations
> in load that either adds or decreases the tension in the bolt.
> How can we get all of the strength we pay for, or do we assume the
> bolt strength is only 500 lbs. and use twice as many bolts in the
> joint? If the joint has been properly designed, the clamping
> surfaces around the bolt will take almost all of the variation if
> the bolt is properly tightened. In this scenario, a load of close
> to 1,000 lbs. can be used because the load will not fluctuate very
> much. But if the joint is not properly tightened, the joined parts
> will separate and the full increase on the load will be on the
> fastener, which will overload it. Or, the load could go to zero,
> which means it is in a fatigue condition and the bolt will fail
> because of the repeated application of a load that it could have
> easily carried except for the fatigue factor. Therefore, a bolt in
> a tension joint will fail from fatigue if it is not tightened
> enough, and it will fail from fatigue and overload, if it is
> tightened beyond its ultimate strength.
> In our example the bolt's ultimate strength is 1,000 lbs.; in actual
> practice there is a safety factor that extends the range beyond the
> 1,000 lbs., before the bolt actually breaks from simple overload.
> Therefore, it is extremely important that we achieve the proper
> tension on the bolt-not too much and not too little.
Jobst Brandt
|
| | | | | | | | | | | |
Date: 04 Sep 2007 20:28:17
From: jim beam
Subject: Re: Yet another broken spoke
|
jobst.brandt@stanfordalumni.org wrote:
> Clare who? writes:
>
>>>> With a tighter spoke the stress variation can have a larger excursion
>>>> than that of a looser spoke.
>
>>> Why?
>
>>> Just to clarify: suppose I plot a graph of stress against time for
>>> a spoke on a wheel on a bicycle that's being ridden down the
>>> road. I expect the graph would be some kind of wave, going up and
>>> down as the spoke passes over the contact patch.
>
>>> By "larger excursion" do you mean that this wave would have a
>>> greater amplitude?
>
>>> Perhaps I'm being stupid but I don't see why you would get a larger
>>> amplitude for a tighter spoke.
>
>> Because you would not. If tensioned to, say 200 lbs, and 200 lbs is
>> suspended from roughly8 of the 28 spokes, you might end up with
>> something like 250 lbs tension on any one spoke. That tension would
>> only change something like 60 lbs in use, and at all times the spoke
>> would be under a minimum of something like 140 lbs. With a 15 or 14
>> guage spoke,that tension would keep the spoke from fatigue.
>
> I think you misunderstand how loads are supported by spoked wheels.
[here we go...]
> Such wheels support loads through the spoke(s) between hub and road.
> In a wooden wagon wheel, that seems obvious to most observers, but
> that a tensioned wire wheel does the same is less apparent. I think
> you should read about this in "the Bicycle Wheel" where the statics
> and effects of supporting loads, transmitting torque and rim brake
> forces, are explained in extensive detail.
and "the bicycle wheel" fails to address the fundamental issue of metal
fatigue and how it originates. spokes elbows, by definition and due to
the fact that they are not loaded axial to the rest of the spoke,
experience a bending moment on loading. hence they fatigue. end of
story. how an "engineer" can make such an enormous oversight is pretty
surprising. how one can /keep on/ making it after all this time and
exposure is truly spectacular.
>
> Basically, spokes in a bicycle wheel do not experience an increase in
> tension when a rider loads the wheel with his weight, but in contrast,
> lose tension when spokes pass through the tire-to-road contact patch.
>
>> Think of the spoke as a bolt, and read the following from
>> Writetool.com:
>
> The following has nothing to do with load distribution in spoked
> wheels and is wholly inappropriate with respect to bicycle wheels.
>
> ---------------------------------------------------------------------
>> Tension Joints
>
>> The shear joint does not rely on tension in the bolt to hold parts
>> together. The tension joint, however, relies on the tension of the
>> bolt to hold two joined parts together. The greater the tension on
>> the bolt, the more force holding them together. Steel and most
>> metals have a property known as fatigue, which means that they lose
>> strength upon repeated loads. For example, a bolt with an ultimate
>> strength of 1,000 lbs. will carry a load of 1,000 lbs. once. It
>> will carry a load of 500 lbs. millions of times. It will carry a
>> load between 500 lbs. and 1,000 lbs. for a limited number of times
>> between 1 and 1 million, depending on whether the load is closer to
>> the 1,000-lbs.-value or the 500-lbs.-value. It doesn't matter how
>> long the heavy load is carried; it can carry 1,000 lbs. forever, as
>> long as it is only one cycle. Most joints are subject to variations
>> in load that either adds or decreases the tension in the bolt.
>
>> How can we get all of the strength we pay for, or do we assume the
>> bolt strength is only 500 lbs. and use twice as many bolts in the
>> joint? If the joint has been properly designed, the clamping
>> surfaces around the bolt will take almost all of the variation if
>> the bolt is properly tightened. In this scenario, a load of close
>> to 1,000 lbs. can be used because the load will not fluctuate very
>> much. But if the joint is not properly tightened, the joined parts
>> will separate and the full increase on the load will be on the
>> fastener, which will overload it. Or, the load could go to zero,
>> which means it is in a fatigue condition and the bolt will fail
>> because of the repeated application of a load that it could have
>> easily carried except for the fatigue factor. Therefore, a bolt in
>> a tension joint will fail from fatigue if it is not tightened
>> enough, and it will fail from fatigue and overload, if it is
>> tightened beyond its ultimate strength.
>
>> In our example the bolt's ultimate strength is 1,000 lbs.; in actual
>> practice there is a safety factor that extends the range beyond the
>> 1,000 lbs., before the bolt actually breaks from simple overload.
>> Therefore, it is extremely important that we achieve the proper
>> tension on the bolt-not too much and not too little.
>
> Jobst Brandt
|
| | | | | | | | | | |
Date: 04 Sep 2007 18:12:52
From:
Subject: Re: Yet another broken spoke
|
On Tue, 04 Sep 2007 17:10:49 -0400, clare at snyder.on.ca wrote:
[snip]
>Because you would not. If tensioned to, say 200 lbs, and 200 lbs is
>suspended from roughly 8 of the 28 spokes, you might end up with
>something like 250 lbs tension on any one spoke.
[snip]
Dear Clare,
This may explain some of the misunderstanding. Like just about any
sensible person, you've made the mistake of thinking that the load on
an axle will cause a large increase in tension in the uppermost
spokes.
But despite what you'd think (and I thought until it was explained to
me), pre-tensioned bicycle wheels do not act as if they hang from the
upper spokes.
It's extremely annoying and counter-intuitive, but both theory and
measurement show that the tension does _not_ increase to any
significant degree on the spokes when we load the axle by sitting on
the bicycle.
Almost all the action consists of _losing_ pre-tension in the spokes
under the axle as the rim flattens ever-so-slightly.
Here's a page devoted to the theoretical side of things, with all the
tension changes considered as vectors that sum to zero:
http://www.astounding.org.uk/ian/wheel/index.html
A really annoying point made on that page is that yes, all the other
spokes show a slight tension increase, but because of their angle,
many of them are actually pulling the damned axle _downward_ or
sideways, instead of upward as almost everyone expects. (Think which
way a spoke at 4 or 8 o'clock moves the axle if you increase its
tension.)
That's why you want to look at the last three columns of the table in
the middle of the page. After calculating the tension _change_ for
each spoke, Ian then uses the _angle_ of each spoke to calculate the
vertical force that will be produced.
The five spokes that lose tension under the theoretical 1000 newton
load account for 955 newtons of support.
The other 31 spokes all increase in tension. But due to their angle,
14 of the spokes that gain tension are actually pulling the axle
downward. When their forces are calculated, the 31 spokes that gain
tension account for only 45 newtons of support, about 5% as much as
the handful of spokes under the axle.
A really, really annoying point is that the greatest tension increase
isn't even in the uppermost spokes. The greatest tension increase is
in the spokes at roughly 5 and 7 o'clock, on either side of the five
spokes under the axle that lose tension.
Jobst made similar calculations in "The Bicycle Wheel."
By attaching an electronic strain gauge to a single spoke, Professor
Gavin demonstrated the huge loss of pre-tension as spokes roll under
the axle. The massive downward spikes in figures 10 and 11, like
icicles hanging from a roof, shows how the spoke loses tension under
load:
http://www.duke.edu/~hpgavin/papers/HPGavin-Wheel-Paper.pdf
Jobst points out that you can test this yourself, with a little help,
by listening to the tone as you pluck spokes before and after someone
sits on a bicycle. The huge loss of tension in the spokes under the
axle will be revealed by the tone dropping.
To summarize, a few spokes under the axle lose impressive amounts of
tension when we load the axle. The other spokes do gain a little
tension, but none of them gain more than 10% of the amount of tension
lost by the spoke directly under the axle--and almost half of them
pull the axle _downward_ because they're angled downward.
As for the loose spoke question, a spoke with more initial tension can
lose more tension before it goes slack. A spoke pre-tensioned to 200
pounds can lose up to 200 pounds of tension as it rolls under the axle
before it rattles loose, but a spoke tensioned to only 100 pounds can
lose only 100 pounds of tension as the rim squashes flat under the
axle.
Again, don't feel bad for making the mistake that everyone makes when
they look at a bicycle wheel. It seems ridiculous that the loading the
axle doesn't put the load on the uppermost spokes, but it doesn't. You
have to work through things and understand that the loss of tension is
the same as a gain in compression.
As Jobst points out in "The Bicycle Wheel," it doesn't matter whether
a wheel has solid wooden spokes with no pre-tension or thin wire
spokes with lots of pre-tension--measurements will show that action
takes place in the spokes under the axle.
The solid wooden spokes under the axle will show a straightforward
gain in compression, which makes sense.
The thin wire pre-tensioned spokes under the axle will show a loss of
tension, which is the same thing, but confusing at first.
In both cases, the spokes under the axle shorten. A gain in
compression is the same as a loss of tension.
Cheers,
Carl Fogel
|
| | | | | | | | | | | |
Date: 04 Sep 2007 23:20:12
From:
Subject: Re: Yet another broken spoke
|
On Tue, 04 Sep 2007 18:12:52 -0600, carlfogel@comcast.net wrote:
Snipped.
>
>As Jobst points out in "The Bicycle Wheel," it doesn't matter whether
>a wheel has solid wooden spokes with no pre-tension or thin wire
>spokes with lots of pre-tension--measurements will show that action
>takes place in the spokes under the axle.
>
>The solid wooden spokes under the axle will show a straightforward
>gain in compression, which makes sense.
>
>The thin wire pre-tensioned spokes under the axle will show a loss of
>tension, which is the same thing, but confusing at first.
>
>In both cases, the spokes under the axle shorten. A gain in
>compression is the same as a loss of tension.
>
>Cheers,
>
>Carl Fogel
OK, Carl - I understand - it DOES make sense.
However, the fact that the LOWER spokes loose tension has the same
effect as the upper spokes gaining tension - if the spoke is too loose
to star with, when it looses tension then regains it's tension it
flexes at the elbow. An adequately tensioned spoke will reduce
tension, but will not loose tension - and the flex at the elbow will
be reduced - perhaps to the point where fatique does not occur in an
appreciable amount (like a spring operated within it's design limits)
Loose spokes still break faster than properly tensioned spokes (and
perhaps even faster than "overtensioned" spokes, as the yeild strength
of the spoke is virtually never exceded)
--
Posted via a free Usenet account from http://www.teranews.com
|
| | | | | | | | | | | | |
Date: 05 Sep 2007 03:46:32
From:
Subject: Re: Yet another broken spoke
|
Clare who? writes:
> Snipped.
>> As Jobst points out in "The Bicycle Wheel," it doesn't matter
>> whether a wheel has solid wooden spokes with no pre-tension or thin
>> wire spokes with lots of pre-tension--measurements will show that
>> action takes place in the spokes under the axle.
>> The solid wooden spokes under the axle will show a straightforward
>> gain in compression, which makes sense.
>> The thin wire pre-tensioned spokes under the axle will show a loss
>> of tension, which is the same thing, but confusing at first.
>> In both cases, the spokes under the axle shorten. A gain in
>> compression is the same as a loss of tension.
> OK, Carl - I understand - it DOES make sense.
> However, the fact that the LOWER spokes loose tension has the same
> effect as the upper spokes gaining tension - if the spoke is too
> loose to star with, when it looses tension then regains it's tension
> it flexes at the elbow. An adequately tensioned spoke will reduce
> tension, but will not loose tension - and the flex at the elbow will
> be reduced - perhaps to the point where fatigue does not occur in an
> appreciable amount (like a spring operated within it's design
> limits)
What is bending the elbow in your perception? If it is carrying less
force and losing less tension, then the stress must be lower. Stress
is what causes spoke failure and the higher and the greater the
variation, the more fatigue damage it causes. The lower tensioned
spoke cannot cause greater bending, there being less force and force
change.
> Loose spokes still break faster than properly tensioned spokes (and
> perhaps even faster than "overtensioned" spokes, as the yeild
> strength of the spoke is virtually never exceded)
I don't know where you derive that statement but it is incorrect.
You'll need to explain the mechanism by which you believe this occurs
before it becomes credible because it goes against conventional
engineering principles.
Jobst Brandt
|
| | | | | | | | | | | | | |
Date: 04 Sep 2007 21:04:10
From: jim beam
Subject: Re: Yet another broken spoke
|
jobst.brandt@stanfordalumni.org wrote:
> Clare who? writes:
>
>> Snipped.
>
>>> As Jobst points out in "The Bicycle Wheel," it doesn't matter
>>> whether a wheel has solid wooden spokes with no pre-tension or thin
>>> wire spokes with lots of pre-tension--measurements will show that
>>> action takes place in the spokes under the axle.
>
>>> The solid wooden spokes under the axle will show a straightforward
>>> gain in compression, which makes sense.
>
>>> The thin wire pre-tensioned spokes under the axle will show a loss
>>> of tension, which is the same thing, but confusing at first.
>
>>> In both cases, the spokes under the axle shorten. A gain in
>>> compression is the same as a loss of tension.
>
>> OK, Carl - I understand - it DOES make sense.
>
>> However, the fact that the LOWER spokes loose tension has the same
>> effect as the upper spokes gaining tension - if the spoke is too
>> loose to star with, when it looses tension then regains it's tension
>> it flexes at the elbow. An adequately tensioned spoke will reduce
>> tension, but will not loose tension - and the flex at the elbow will
>> be reduced - perhaps to the point where fatigue does not occur in an
>> appreciable amount (like a spring operated within it's design
>> limits)
>
> What is bending the elbow in your perception?
simple loading!!! the spoke elbow is offset from the spoke axis, thus
is it subject to bending - by definition!!!
> If it is carrying less
> force and losing less tension, then the stress must be lower. Stress
> is what causes spoke failure and the higher and the greater the
> variation, the more fatigue damage it causes. The lower tensioned
> spoke cannot cause greater bending, there being less force and force
> change.
except that it /is/ being bent back and forth more, simply because it's
interleaved.
>
>> Loose spokes still break faster than properly tensioned spokes (and
>> perhaps even faster than "overtensioned" spokes, as the yeild
>> strength of the spoke is virtually never exceded)
>
> I don't know where you derive that statement but it is incorrect.
er, even /you/ say that loose spokes break...
> You'll need to explain the mechanism by which you believe this occurs
> before it becomes credible because it goes against conventional
> engineering principles.
it's already been discussed. the only one here having problems
recognizing it appears to be you.
|
| | | | | | | | | | | | | | |
Date: 05 Sep 2007 09:04:04
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> jobst.brandt@stanfordalumni.org wrote:
>> What is bending the elbow in your perception?
>
> simple loading!!! the spoke elbow is offset from the spoke axis, thus
> is it subject to bending - by definition!!!
If the spoke elbow is fully supported on its inside radius it can't
bend. By definition!!!!!!!!
> except that it /is/ being bent back and forth more, simply because it's
> interleaved.
Do the math. How much force (tension) does it take to fully straighten a
clothesline with a 5lb weight in the center?
|
| | | | | | | | | | | | | | | |
Date: 05 Sep 2007 06:23:51
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> jobst.brandt@stanfordalumni.org wrote:
>
>>> What is bending the elbow in your perception?
>>
>> simple loading!!! the spoke elbow is offset from the spoke axis, thus
>> is it subject to bending - by definition!!!
>
> If
"if"??
> the spoke elbow is fully supported on its inside radius it can't
> bend. By definition!!!!!!!!
but it's not. so you're bullshitting.
>
>
>> except that it /is/ being bent back and forth more, simply because
>> it's interleaved.
>
> Do the math. How much force (tension) does it take to fully straighten a
> clothesline with a 5lb weight in the center?
>
false example - the usual peter cole deceit.
|
| | | | | | | | | | | | | | | | |
Date: 05 Sep 2007 10:38:03
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> jobst.brandt@stanfordalumni.org wrote:
>>
>>>> What is bending the elbow in your perception?
>>>
>>> simple loading!!! the spoke elbow is offset from the spoke axis,
>>> thus is it subject to bending - by definition!!!
>>
>> If
>
> "if"??
>
>> the spoke elbow is fully supported on its inside radius it can't bend.
>> By definition!!!!!!!!
>
> but it's not. so you're bullshitting.
It is if you've built your wheel right.
>>> except that it /is/ being bent back and forth more, simply because
>>> it's interleaved.
>>
>> Do the math. How much force (tension) does it take to fully straighten
>> a clothesline with a 5lb weight in the center?
>>
>
> false example - the usual peter cole deceit.
No, the interleaving force is in the middle of the spoke, like the
clothesline. Consider the vectors.
|
| | | | | | | | | | | | | | | | | |
Date: 05 Sep 2007 20:58:54
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>> jobst.brandt@stanfordalumni.org wrote:
>>>
>>>>> What is bending the elbow in your perception?
>>>>
>>>> simple loading!!! the spoke elbow is offset from the spoke axis,
>>>> thus is it subject to bending - by definition!!!
>>>
>>> If
>>
>> "if"??
>>
>>> the spoke elbow is fully supported on its inside radius it can't
>>> bend. By definition!!!!!!!!
>>
>> but it's not. so you're bullshitting.
>
> It is if you've built your wheel right.
>
>
>>>> except that it /is/ being bent back and forth more, simply because
>>>> it's interleaved.
>>>
>>> Do the math. How much force (tension) does it take to fully
>>> straighten a clothesline with a 5lb weight in the center?
>>>
>>
>> false example - the usual peter cole deceit.
>
> No, the interleaving force is in the middle of the spoke, like the
> clothesline. Consider the vectors.
and we're discussing loosening and /angle/ increase. /you/ are trying
to deceive with /tension/ increase and straightening which can never be
achieved - as you well know.
|
| | | | | | | | | | | | | | | | | | |
Date: 06 Sep 2007 16:07:43
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>>> jim beam wrote:
>>>>> jobst.brandt@stanfordalumni.org wrote:
>>>>
>>>>>> What is bending the elbow in your perception?
>>>>>
>>>>> simple loading!!! the spoke elbow is offset from the spoke axis,
>>>>> thus is it subject to bending - by definition!!!
>>>>
>>>> If
>>>
>>> "if"??
>>>
>>>> the spoke elbow is fully supported on its inside radius it can't
>>>> bend. By definition!!!!!!!!
>>>
>>> but it's not. so you're bullshitting.
>>
>> It is if you've built your wheel right.
>>
>>
>>>>> except that it /is/ being bent back and forth more, simply because
>>>>> it's interleaved.
>>>>
>>>> Do the math. How much force (tension) does it take to fully
>>>> straighten a clothesline with a 5lb weight in the center?
>>>>
>>>
>>> false example - the usual peter cole deceit.
>>
>> No, the interleaving force is in the middle of the spoke, like the
>> clothesline. Consider the vectors.
>
> and we're discussing loosening and /angle/ increase. /you/ are trying
> to deceive with /tension/ increase and straightening which can never be
> achieved - as you well know.
I don't know what you are discussing, I was discussing the change in
angle with the change in tension -- it's immaterial which direction you
want to reference.
|
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Date: 06 Sep 2007 21:02:01
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>> Peter Cole wrote:
>>>>> jim beam wrote:
>>>>>> jobst.brandt@stanfordalumni.org wrote:
>>>>>
>>>>>>> What is bending the elbow in your perception?
>>>>>>
>>>>>> simple loading!!! the spoke elbow is offset from the spoke axis,
>>>>>> thus is it subject to bending - by definition!!!
>>>>>
>>>>> If
>>>>
>>>> "if"??
>>>>
>>>>> the spoke elbow is fully supported on its inside radius it can't
>>>>> bend. By definition!!!!!!!!
>>>>
>>>> but it's not. so you're bullshitting.
>>>
>>> It is if you've built your wheel right.
>>>
>>>
>>>>>> except that it /is/ being bent back and forth more, simply because
>>>>>> it's interleaved.
>>>>>
>>>>> Do the math. How much force (tension) does it take to fully
>>>>> straighten a clothesline with a 5lb weight in the center?
>>>>>
>>>>
>>>> false example - the usual peter cole deceit.
>>>
>>> No, the interleaving force is in the middle of the spoke, like the
>>> clothesline. Consider the vectors.
>>
>> and we're discussing loosening and /angle/ increase. /you/ are trying
>> to deceive with /tension/ increase and straightening which can never
>> be achieved - as you well know.
>
> I don't know what you are discussing, I was discussing the change in
> angle with the change in tension -- it's immaterial which direction you
> want to reference.
wriggle. squirm. you cite a false example in a deliberate attempt to
mislead. you get called on it. now you start bleating. just address
the freakin' point originally asked and stop playing games.
|
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Date: 05 Sep 2007 00:01:13
From:
Subject: Re: Yet another broken spoke
|
On 05 Sep 2007 03:46:32 GMT, jobst.brandt@stanfordalumni.org wrote:
>Clare who? writes:
>
>> Snipped.
>
>>> As Jobst points out in "The Bicycle Wheel," it doesn't matter
>>> whether a wheel has solid wooden spokes with no pre-tension or thin
>>> wire spokes with lots of pre-tension--measurements will show that
>>> action takes place in the spokes under the axle.
>
>>> The solid wooden spokes under the axle will show a straightforward
>>> gain in compression, which makes sense.
>
>>> The thin wire pre-tensioned spokes under the axle will show a loss
>>> of tension, which is the same thing, but confusing at first.
>
>>> In both cases, the spokes under the axle shorten. A gain in
>>> compression is the same as a loss of tension.
>
>> OK, Carl - I understand - it DOES make sense.
>
>> However, the fact that the LOWER spokes loose tension has the same
>> effect as the upper spokes gaining tension - if the spoke is too
>> loose to star with, when it looses tension then regains it's tension
>> it flexes at the elbow. An adequately tensioned spoke will reduce
>> tension, but will not loose tension - and the flex at the elbow will
>> be reduced - perhaps to the point where fatigue does not occur in an
>> appreciable amount (like a spring operated within it's design
>> limits)
>
>What is bending the elbow in your perception? If it is carrying less
>force and losing less tension, then the stress must be lower. Stress
>is what causes spoke failure and the higher and the greater the
>variation, the more fatigue damage it causes. The lower tensioned
>spoke cannot cause greater bending, there being less force and force
>change.
>
>> Loose spokes still break faster than properly tensioned spokes (and
>> perhaps even faster than "overtensioned" spokes, as the yeild
>> strength of the spoke is virtually never exceded)
>
>I don't know where you derive that statement but it is incorrect.
>You'll need to explain the mechanism by which you believe this occurs
>before it becomes credible because it goes against conventional
>engineering principles.
>
>Jobst Brandt
I've explained it. You do not understand it or dissagree. Your
peroggotive, either way.
The simple fact of the matter remains. Loose spokes break (at the
elbow). Tight spokes (properly tensioned) do NOT. When metal is pre
stretched or pre tensioned, a change in tension does NOT cause
appreciable fatigue. It is when the metal is taken through the initial
ternsioning and when that tension is lost that the fatigue happens.
The fatigue does NOT happen when the tension changes within a
perscribed range. A properly tensioned spoke never gets out of that
safe tension range, where a loose spoke goes through that transition
at least once (I think even twice or more)) every turn of the wheel.
Over tensioned spokes generally snap the nipples when they fail, but
can also snap at the elbow.(or pull out of the rim)
Loose spokes also wear the holes in the hubs - and wear the spokes
where they go through the hub. I've replaced numerous spokes that were
worn half way through before breaking (and some that had not yet
broken)
--
Posted via a free Usenet account from http://www.teranews.com
|
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Date: 05 Sep 2007 02:28:29
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-05, clare at snyder.on.ca < > wrote:
[...]
> Loose spokes also wear the holes in the hubs - and wear the spokes
> where they go through the hub.
I hadn't thought of that. That would explain the phenomenon (loose
spokes breaking) in a way that's consistent with my understanding of
Jobst's earlier suggestion that there is a bit of clearance down there.
I thought the reasoning was: the spoke can't easily be bent since it
isn't firmly held in the hub hole but free to wobble a bit. But if it's
wobbling up and down it can wear and that can initiate fatigue.
> I've replaced numerous spokes that were worn half way through before
> breaking (and some that had not yet broken)
Maybe this is something datakoll's practice of putting Teflon wax in the
hub holes before you put the spokes in could help with.
|
| | | | | | | | | | | | | | | |
Date: 05 Sep 2007 21:13:42
From:
Subject: Re: Yet another broken spoke
|
Ben C? writes:
>> [...]
>> Loose spokes also wear the holes in the hubs - and wear the spokes
>> where they go through the hub.
> I hadn't thought of that. That would explain the phenomenon (loose
> spokes breaking) in a way that's consistent with my understanding of
> Jobst's earlier suggestion that there is a bit of clearance down
> there.
You'll have to show some evidence of loose spokes wearing thin at the
elbow. That has not been observed by anyone building wheels around
here and I've been watching this sort of thing for more years than
most. Spoke failures are from residual stress and stress
concentrations, not loose spokes or flexing from interleaving.
Flexing from interleaving (assuming the wheel was reasonably true) is
no greater with loose spokes than with tight ones, and probably less,
there being less force involved. Besides, if that were the source of
failure, then non-interleaved or radial spokes would be more durable,
as would tangential spoking, where spoke crossings are father from the
flange and have a minuscule angle.
> I thought the reasoning was: the spoke can't easily be bent since it
> isn't firmly held in the hub hole but free to wobble a bit. But if
> it's wobbling up and down it can wear and that can initiate fatigue.
But it doesn't because even becoming slack does not cause the contact
area to wear, there being no contact.
>> I've replaced numerous spokes that were worn half way through before
>> breaking (and some that had not yet broken)
That is pure imagination to put it mildly. Where are the readers
who detest exaggeration now?
> Maybe this is something datakoll's practice of putting Teflon wax in the
> hub holes before you put the spokes in could help with.
Bicycling is full of snake oil. Remember how a while back it was the
stem jam nut that caused stem separations from inner tubes? Well that
manufacturing run is gone now and we don't hear of it any more, but
there were many who believed the jam nut fable religiously in spite of
proof to the contrary (a manually tightened jam nut becomes loose when
the tire is inflated, showing that separation force is inflation
pressure, not the nut.) Now its spoke wear that causes loose spokes
to fail!
Jobst Brandt
|
| | | | | | | | | | | | | | | | |
Date: 05 Sep 2007 21:54:03
From:
Subject: Re: Yet another broken spoke
|
On 05 Sep 2007 21:13:42 GMT, jobst.brandt@stanfordalumni.org wrote:
>Ben C? writes:
>
>>> [...]
>>> Loose spokes also wear the holes in the hubs - and wear the spokes
>>> where they go through the hub.
>
>> I hadn't thought of that. That would explain the phenomenon (loose
>> spokes breaking) in a way that's consistent with my understanding of
>> Jobst's earlier suggestion that there is a bit of clearance down
>> there.
>
>You'll have to show some evidence of loose spokes wearing thin at the
>elbow. That has not been observed by anyone building wheels around
>here and I've been watching this sort of thing for more years than
>most. Spoke failures are from residual stress and stress
>concentrations, not loose spokes or flexing from interleaving.
I just threw out a couple spokes I pulled from a 1970 CCM that were
worn noticeably - and ONE of them was broken.Same on a 1963 Schwinn
American that had sat for about 15 years. Replaced 6 spokes on that
one.Only one was initially broken.
All the spokes were loose on all 4 wheels.
--
Posted via a free Usenet account from http://www.teranews.com
|
| | | | | | | | | | | | | | | | | |
Date: 06 Sep 2007 02:32:56
From:
Subject: Re: Yet another broken spoke
|
clare who? writes:
>>>> Loose spokes also wear the holes in the hubs - and wear the
>>>> spokes where they go through the hub.
>>> I hadn't thought of that. That would explain the phenomenon
>>> (loose spokes breaking) in a way that's consistent with my
>>> understanding of Jobst's earlier suggestion that there is a bit of
>>> clearance down there.
>> You'll have to show some evidence of loose spokes wearing thin at
>> the elbow. That has not been observed by anyone building wheels
>> around here and I've been watching this sort of thing for more
>> years than most. Spoke failures are from residual stress and
>> stress concentrations, not loose spokes or flexing from
>> interleaving.
> I just threw out a couple spokes I pulled from a 1970 CCM that were
> worn noticeably - and ONE of them was broken.Same on a 1963 Schwinn
> American that had sat for about 15 years. Replaced 6 spokes on that
> one.Only one was initially broken.
You say "noticeably". What did you notice other than a clean area
where the spokes contacted the flange?
> All the spokes were loose on all 4 wheels.
Your experience being different from the norm, how about some pictures
of these worn spokes? How much wear did they have? How much was the
spoke cross section reduced from the original? As I said, no one I
know in the wheel building business has observed such wear, so it
makes your findings unusual enough to be questioned. Something that
could be resolved with some photos of the worn spokes.
Jobst Brandt
|
| | | | | | | | | | | | | | | | | | |
Date: 06 Sep 2007 11:16:00
From: _
Subject: Re: Yet another broken spoke
|
On 06 Sep 2007 02:32:56 GMT, jobst.brandt@stanfordalumni.org wrote:
> clare who? writes:
>
>>>>> Loose spokes also wear the holes in the hubs - and wear the
>>>>> spokes where they go through the hub.
>
>>>> I hadn't thought of that. That would explain the phenomenon
>>>> (loose spokes breaking) in a way that's consistent with my
>>>> understanding of Jobst's earlier suggestion that there is a bit of
>>>> clearance down there.
>
>>> You'll have to show some evidence of loose spokes wearing thin at
>>> the elbow. That has not been observed by anyone building wheels
>>> around here and I've been watching this sort of thing for more
>>> years than most. Spoke failures are from residual stress and
>>> stress concentrations, not loose spokes or flexing from
>>> interleaving.
>
>> I just threw out a couple spokes I pulled from a 1970 CCM that were
>> worn noticeably - and ONE of them was broken.Same on a 1963 Schwinn
>> American that had sat for about 15 years. Replaced 6 spokes on that
>> one.Only one was initially broken.
>
> You say "noticeably". What did you notice other than a clean area
> where the spokes contacted the flange?
>
>> All the spokes were loose on all 4 wheels.
>
> Your experience being different from the norm, how about some pictures
> of these worn spokes? How much wear did they have? How much was the
> spoke cross section reduced from the original? As I said, no one I
> know in the wheel building business has observed such wear, so it
> makes your findings unusual enough to be questioned. Something that
> could be resolved with some photos of the worn spokes.
>
> Jobst Brandt
Jobst, that bike-shaped-object (the CCM) may well have had steel hubs; and
as I recall, those had no countersinking on the spoke holes.
Wear at the inside of the spoke elbow (especially if the wheel was built a
la jim beam) would be more likely in such a combination...
|
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Date: 06 Sep 2007 11:38:06
From:
Subject: Re: Yet another broken spoke
|
On Thu, 06 Sep 2007 11:16:00 GMT, _
<jtayNOSPAMlor@hfDONTSENDMESPAMx.andara.com > wrote:
>On 06 Sep 2007 02:32:56 GMT, jobst.brandt@stanfordalumni.org wrote:
>
>> clare who? writes:
>>
>>>>>> Loose spokes also wear the holes in the hubs - and wear the
>>>>>> spokes where they go through the hub.
>>
>>>>> I hadn't thought of that. That would explain the phenomenon
>>>>> (loose spokes breaking) in a way that's consistent with my
>>>>> understanding of Jobst's earlier suggestion that there is a bit of
>>>>> clearance down there.
>>
>>>> You'll have to show some evidence of loose spokes wearing thin at
>>>> the elbow. That has not been observed by anyone building wheels
>>>> around here and I've been watching this sort of thing for more
>>>> years than most. Spoke failures are from residual stress and
>>>> stress concentrations, not loose spokes or flexing from
>>>> interleaving.
>>
>>> I just threw out a couple spokes I pulled from a 1970 CCM that were
>>> worn noticeably - and ONE of them was broken.Same on a 1963 Schwinn
>>> American that had sat for about 15 years. Replaced 6 spokes on that
>>> one.Only one was initially broken.
>>
>> You say "noticeably". What did you notice other than a clean area
>> where the spokes contacted the flange?
>>
>>> All the spokes were loose on all 4 wheels.
>>
>> Your experience being different from the norm, how about some pictures
>> of these worn spokes? How much wear did they have? How much was the
>> spoke cross section reduced from the original? As I said, no one I
>> know in the wheel building business has observed such wear, so it
>> makes your findings unusual enough to be questioned. Something that
>> could be resolved with some photos of the worn spokes.
>>
>> Jobst Brandt
>
>Jobst, that bike-shaped-object (the CCM) may well have had steel hubs; and
>as I recall, those had no countersinking on the spoke holes.
>
>Wear at the inside of the spoke elbow (especially if the wheel was built a
>la jim beam) would be more likely in such a combination...
Definitely steel hubs. Alloy hubs on lowcost bikes in the seventies?
Didn't happen.
--
Posted via a free Usenet account from http://www.teranews.com
|
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Date: 05 Sep 2007 20:59:17
From: jim beam
Subject: Re: Yet another broken spoke
|
jobst.brandt@stanfordalumni.org wrote:
> clare who? writes:
>
>>>>> Loose spokes also wear the holes in the hubs - and wear the
>>>>> spokes where they go through the hub.
>
>>>> I hadn't thought of that. That would explain the phenomenon
>>>> (loose spokes breaking) in a way that's consistent with my
>>>> understanding of Jobst's earlier suggestion that there is a bit of
>>>> clearance down there.
>
>>> You'll have to show some evidence of loose spokes wearing thin at
>>> the elbow. That has not been observed by anyone building wheels
>>> around here and I've been watching this sort of thing for more
>>> years than most. Spoke failures are from residual stress and
>>> stress concentrations, not loose spokes or flexing from
>>> interleaving.
>
>> I just threw out a couple spokes I pulled from a 1970 CCM that were
>> worn noticeably - and ONE of them was broken.Same on a 1963 Schwinn
>> American that had sat for about 15 years. Replaced 6 spokes on that
>> one.Only one was initially broken.
>
> You say "noticeably". What did you notice other than a clean area
> where the spokes contacted the flange?
>
>> All the spokes were loose on all 4 wheels.
>
> Your experience being different from the norm, how about some pictures
> of these worn spokes? How much wear did they have? How much was the
> spoke cross section reduced from the original? As I said, no one I
> know in the wheel building business has observed such wear, so it
> makes your findings unusual enough to be questioned. Something that
> could be resolved with some photos of the worn spokes.
>
but you have admitted to existence of this phenomenon in other writings
- why bullshit and deny now?
http://groups.google.com/group/rec.bicycles.tech/msg/d7dd514160221d16
"These are typically a fretting notch where they cross,
such that if you slide them apart with the fingers, they pop out of
engagement and readily snap back in"
|
| | | | | | | | | | | | | | | | | | |
Date: 05 Sep 2007 23:33:27
From:
Subject: Re: Yet another broken spoke
|
On 06 Sep 2007 02:32:56 GMT, jobst.brandt@stanfordalumni.org wrote:
>clare who? writes:
>
>>>>> Loose spokes also wear the holes in the hubs - and wear the
>>>>> spokes where they go through the hub.
>
>>>> I hadn't thought of that. That would explain the phenomenon
>>>> (loose spokes breaking) in a way that's consistent with my
>>>> understanding of Jobst's earlier suggestion that there is a bit of
>>>> clearance down there.
>
>>> You'll have to show some evidence of loose spokes wearing thin at
>>> the elbow. That has not been observed by anyone building wheels
>>> around here and I've been watching this sort of thing for more
>>> years than most. Spoke failures are from residual stress and
>>> stress concentrations, not loose spokes or flexing from
>>> interleaving.
>
>> I just threw out a couple spokes I pulled from a 1970 CCM that were
>> worn noticeably - and ONE of them was broken.Same on a 1963 Schwinn
>> American that had sat for about 15 years. Replaced 6 spokes on that
>> one.Only one was initially broken.
>
>You say "noticeably". What did you notice other than a clean area
>where the spokes contacted the flange?
The elbow was worn on the inside -had a sharp edge showing. Was also
showing rust at the wear point while the rest of the spokes still had
zinc/tin/whatever preventing rust.
>
>> All the spokes were loose on all 4 wheels.
>
>Your experience being different from the norm, how about some pictures
>of these worn spokes? How much wear did they have? How much was the
>spoke cross section reduced from the original? As I said, no one I
>know in the wheel building business has observed such wear, so it
>makes your findings unusual enough to be questioned. Something that
>could be resolved with some photos of the worn spokes.
>
>Jobst Brandt
I threw them out -the garbage went at about 07:30 last thursday so I
can't get THOSE back - but I'll definitely shoot the next ones I find
(which could be a while - I've got all the "old stuff" fixed up for
now. I'd say they were worn better than 10% and less than 25%, but had
a sharp edge to the wear, which would act as a stress rizer - allowing
even minor stress reversals to break the spokes. I will check my
"stash" to see if I have any worn ones left floating around.
--
Posted via a free Usenet account from http://www.teranews.com
|
| | | | | | | | | | | | | | | | |
Date: 05 Sep 2007 17:21:13
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-05, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org > wrote:
> Ben C? writes:
>
>>> [...]
>>> Loose spokes also wear the holes in the hubs - and wear the spokes
>>> where they go through the hub.
>
>> I hadn't thought of that. That would explain the phenomenon (loose
>> spokes breaking) in a way that's consistent with my understanding of
>> Jobst's earlier suggestion that there is a bit of clearance down
>> there.
>
> You'll have to show some evidence of loose spokes wearing thin at the
> elbow. That has not been observed by anyone building wheels around
> here
Do people build with the spokes too loose around there?
> and I've been watching this sort of thing for more years than most.
> Spoke failures are from residual stress and stress concentrations, not
> loose spokes or flexing from interleaving.
I believe those are possible causes. But I am not as sure as you that
they are the main or only causes.
> Flexing from interleaving (assuming the wheel was reasonably true) is
> no greater with loose spokes than with tight ones, and probably less,
> there being less force involved. Besides, if that were the source of
> failure, then non-interleaved or radial spokes would be more durable,
> as would tangential spoking, where spoke crossings are father from the
> flange and have a minuscule angle.
>
>> I thought the reasoning was: the spoke can't easily be bent since it
>> isn't firmly held in the hub hole but free to wobble a bit. But if
>> it's wobbling up and down it can wear and that can initiate fatigue.
>
> But it doesn't because even becoming slack does not cause the contact
> area to wear, there being no contact.
>
>>> I've replaced numerous spokes that were worn half way through before
>>> breaking (and some that had not yet broken)
>
> That is pure imagination to put it mildly.
How are you so sure that what Clare is describing cannot possibly have
occurred? I see no particular reason to doubt the report.
> Where are the readers who detest exaggeration now?
>
>> Maybe this is something datakoll's practice of putting Teflon wax in the
>> hub holes before you put the spokes in could help with.
>
> Bicycling is full of snake oil.
Ain't that the truth.
> Remember how a while back it was the stem jam nut that caused stem
> separations from inner tubes? Well that manufacturing run is gone now
> and we don't hear of it any more, but there were many who believed the
> jam nut fable religiously in spite of proof to the contrary (a
> manually tightened jam nut becomes loose when the tire is inflated,
> showing that separation force is inflation pressure, not the nut.)
> Now its spoke wear that causes loose spokes to fail!
There's no law that says all spokes have to fail for the same reason.
Here are a variety of possible reasons I can remember from RBT, in no
particular order, any accumulation of which any individual spoke might
suffer from:
1. Residual stress from manufacture
2. Retained stress in elbow from the build
3. Shank too long/bad spoke line
4. Surface finish of spokes poor (crap spokes)
5. Corrosion
6. Stress corrosion
7. Not enough tension, so spokes go slack
8. Rim flat spot causing slack spokes at the flat spot
9. Riding with too much weight on the bike so spokes go slack
10. Wear at the elbow
They all have varying degrees of supporting evidence, mostly indirect,
and of theoretical plausibility.
I have not seen anyone provide any convincing evidence that (1) and (2)
are the dominant factors to the total exclusion of all the others.
Personally I suspect (4), (7) and (9) are also quite a big part of the
picture.
|
| | | | | | | | | | | | | | | | | |
Date: 05 Sep 2007 22:47:29
From:
Subject: Re: Yet another broken spoke
|
Ben C? writes:
>>>> Loose spokes also wear the holes in the hubs - and wear the
>>>> spokes where they go through the hub.
>>> I hadn't thought of that. That would explain the phenomenon
>>> (loose spokes breaking) in a way that's consistent with my
>>> understanding of Jobst's earlier suggestion that there is a bit of
>>> clearance down there.
>> You'll have to show some evidence of loose spokes wearing thin at
>> the elbow. That has not been observed by anyone building wheels
>> around here
> Do people build with the spokes too loose around there?
Wheelsmith was the first, when they started using their Holland
Mechanics robot to build wheels. It was their bad experience with
wheels losing alignment that introduced SpokePrep, a glue to hide
loose spoking and imitated world wide by machine builders because the
machines could not distinguish spoke twist from spoke nipple rotating
(adjustment) causing an infinite loop of (non) corrections when wheels
got reasonably tight. Holland Mechanics said last year that they were
addressing this issue, one that is easily solved by a radial pneumatic
piston that unloads the spoke to be adjusted.
>> and I've been watching this sort of thing for more years than most.
>> Spoke failures are from residual stress and stress concentrations, not
>> loose spokes or flexing from interleaving.
> I believe those are possible causes. But I am not as sure as you that
> they are the main or only causes.
Yes, lets hear what you believe are the main causes.
>> Flexing from interleaving (assuming the wheel was reasonably true)
>> is no greater with loose spokes than with tight ones, and probably
>> less, there being less force involved. Besides, if that were the
>> source of failure, then non-interleaved or radial spokes would be
>> more durable, as would tangential spoking, where spoke crossings
>> are father from the flange and have a minuscule angle.
>>> I thought the reasoning was: the spoke can't easily be bent since
>>> it isn't firmly held in the hub hole but free to wobble a bit.
>>> But if it's wobbling up and down it can wear and that can initiate
>>> fatigue.
Only if you believe it is making solid contact, has grit between it
and the flange hole and doesn't slacken that force when wobbling,
wobbling caused by slackening. This scenario doesn't make sense.
>> But it doesn't because even becoming slack does not cause the
>> contact area to wear, there being no contact.
>>>> I've replaced numerous spokes that were worn half way through before
>>>> breaking (and some that had not yet broken)
>> That is pure imagination to put it mildly.
> How are you so sure that what Clare is describing cannot possibly have
> occurred? I see no particular reason to doubt the report.
As I mentioned, in theory it is not possible and in practice I have
never seen wear inside the spoke elbow in all the years I have been
involved with bicycles. I think if you read "the Bicycle Wheel" you
should be aware how thoroughly I have considered these effects.
>> Where are the readers who detest exaggeration now?
>>> Maybe this is something datakoll's practice of putting Teflon wax in the
>>> hub holes before you put the spokes in could help with.
>> Bicycling is full of snake oil.
> Ain't that the truth.
>> Remember how a while back it was the stem jam nut that caused stem
>> separations from inner tubes? Well that manufacturing run is gone now
>> and we don't hear of it any more, but there were many who believed the
>> jam nut fable religiously in spite of proof to the contrary (a
>> manually tightened jam nut becomes loose when the tire is inflated,
>> showing that separation force is inflation pressure, not the nut.)
>> Now its spoke wear that causes loose spokes to fail!
> There's no law that says all spokes have to fail for the same reason.
Oh, so what is the reason? I'll stick with residual stress as cause,
the explanation for which is explained in "the Bicycle Wheel".
> Here are a variety of possible reasons I can remember from RBT, in no
> particular order, any accumulation of which any individual spoke might
> suffer from:
> 1. Residual stress from manufacture
> 2. Retained stress in elbow from the build
> 3. Shank too long/bad spoke line
> 4. Surface finish of spokes poor (crap spokes)
> 5. Corrosion
> 6. Stress corrosion
> 8. Rim flat spot causing slack spokes at the flat spot
> 9. Riding with too much weight on the bike so spokes go slack
> 10. Wear at the elbow
> 7. Not enough tension, so spokes go slack
These are all the same issue and you slipped them in with valid
causes. However, that is what we are pursuing in this thread. How
does low tension cause spoke failure?
> They all have varying degrees of supporting evidence, mostly indirect,
> and of theoretical plausibility.
The first three have direct theoretical and practical evidence and
were resolved with the solutions I proposed. You can skip 4 through 5
for the spokes most of us use. As I have often mentioned, I have
wheels that went 300,000 miles with the same spokes (replacing rims)
when they wore out and no failures on the front wheel and outbound
right side spokes that got damaged by the chain.
> I have not seen anyone provide any convincing evidence that (1) and (2)
> are the dominant factors to the total exclusion of all the others.
> Personally I suspect (4), (7) and (9) are also quite a big part of the
> picture.
Basic material science spends great effort to make them credible,
through theory and lab testing. I think we have discussed this at
great length with only a "former metallurgist" claiming that new
materials resolved those causes rather than going back to short elbows
(that DT did) and to properly shape spokes and stress relieve after
building
Jobst Brandt
|
| | | | | | | | | | | | | | | | | | |
Date: 05 Sep 2007 20:59:46
From: jim beam
Subject: Re: Yet another broken spoke
|
>jobst.brandt@stanfordalumni.org wrote:
>> Ben C? writes:
>
<snip for clarity >
>> 1. Residual stress from manufacture
>> 2. Retained stress in elbow from the build
>> 3. Shank too long/bad spoke line
>> 4. Surface finish of spokes poor (crap spokes)
>> 5. Corrosion
>> 6. Stress corrosion
>
>> 8. Rim flat spot causing slack spokes at the flat spot
>> 9. Riding with too much weight on the bike so spokes go slack
>> 10. Wear at the elbow
>> 7. Not enough tension, so spokes go slack
>
> These are all the same issue
eh? no they're not. to pick just one, there's no way stress corrosion
can be confused with low cycle fatigue.
> and you slipped them in with valid
> causes. However, that is what we are pursuing in this thread. How
> does low tension cause spoke failure?
how about getting facts straight first?
>
>> They all have varying degrees of supporting evidence, mostly indirect,
>> and of theoretical plausibility.
>
> The first three have direct theoretical and practical evidence and
> were resolved with the solutions I proposed.
no they don't because "residual stress" is a red herring. the fatigue
initiation point is /not/ that of a high residual stress point - as
you'd know if you'd properly examined the fatigue fracture surfaces.
> You can skip 4 through 5
> for the spokes most of us use.
why? too inconvenient to discuss anything that can't be misconstrued in
the context of "residual stress".
> As I have often mentioned, I have
> wheels that went 300,000 miles with the same spokes
except for the spokes that you've replaced because they've failed...
> (replacing rims)
> when they wore out and no failures on the front wheel and outbound
> right side spokes that got damaged by the chain.
what happened to the excuse about having a stick in the spokes? any
other excuses or omissions?
>
>> I have not seen anyone provide any convincing evidence that (1) and (2)
>> are the dominant factors to the total exclusion of all the others.
>> Personally I suspect (4), (7) and (9) are also quite a big part of the
>> picture.
>
> Basic material science spends great effort to make them credible,
> through theory and lab testing.
indeed it does. and then it gets ignored by "engineers" that didn't
bother to research beyond the presumption that would allow them to claim
credit for the work of others.
> I think we have discussed this at
> great length with only a "former metallurgist" claiming that new
> materials resolved those causes rather than going back to short elbows
> (that DT did) and to properly shape spokes and stress relieve after
> building
truth is jobst, if you ever properly addressed the points i have had to
repeatedly raise with you, or ever bothered to read the cites i've given
you, went to the library and did your own homework, or even bought a
decent magnifier and bothered to examine fracture surfaces from actual
failures, you might, just might, be able to finally start to understand
a little about fatigue. instead, you continue to write suppositional
bullshit based on a shamefully poor grasp of the facts. if you even
understood the difference between materials that strain age and those
that don't, you might evidence some potential for understanding. but as
things stand, you continue to confirm the truth of the saying,
"ignorance can be cured, stupid is forever".
|
| | | | | | | | | | | | | | | | | | | |
Date: 07 Sep 2007 14:22:20
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> >jobst.brandt@stanfordalumni.org wrote:
>> I think we have discussed this at
>> great length with only a "former metallurgist" claiming that new
>> materials resolved those causes rather than going back to short elbows
>> (that DT did) and to properly shape spokes and stress relieve after
>> building
>
> truth is jobst, if you ever properly addressed the points i have had to
> repeatedly raise with you, or ever bothered to read the cites i've given
> you, went to the library and did your own homework, or even bought a
> decent magnifier and bothered to examine fracture surfaces from actual
> failures, you might, just might, be able to finally start to understand
> a little about fatigue. instead, you continue to write suppositional
> bullshit based on a shamefully poor grasp of the facts. if you even
> understood the difference between materials that strain age and those
> that don't, you might evidence some potential for understanding. but as
> things stand, you continue to confirm the truth of the saying,
> "ignorance can be cured, stupid is forever".
Just out of curiosity, I Googled to see where this was originally
explained to you.
It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
good job. Apparently it didn't stick. I can see why Jobst no longer
bothers to respond.
http://tinyurl.com/29v4u2
|
| | | | | | | | | | | | | | | | | | | | |
Date: 07 Sep 2007 18:28:32
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> >jobst.brandt@stanfordalumni.org wrote:
>
>>> I think we have discussed this at
>>> great length with only a "former metallurgist" claiming that new
>>> materials resolved those causes rather than going back to short elbows
>>> (that DT did) and to properly shape spokes and stress relieve after
>>> building
>>
>> truth is jobst, if you ever properly addressed the points i have had
>> to repeatedly raise with you, or ever bothered to read the cites i've
>> given you, went to the library and did your own homework, or even
>> bought a decent magnifier and bothered to examine fracture surfaces
>> from actual failures, you might, just might, be able to finally start
>> to understand a little about fatigue. instead, you continue to write
>> suppositional bullshit based on a shamefully poor grasp of the facts.
>> if you even understood the difference between materials that strain
>> age and those that don't, you might evidence some potential for
>> understanding. but as things stand, you continue to confirm the truth
>> of the saying, "ignorance can be cured, stupid is forever".
>
> Just out of curiosity, I Googled to see where this was originally
> explained to you.
>
> It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
> good job. Apparently it didn't stick. I can see why Jobst no longer
> bothers to respond.
>
> http://tinyurl.com/29v4u2
you had to dig back /four years/ to find something that predated luns
tee reminding us all of residual stress profiles? ok, so having done
that, can you now explain how fatigue still nucleates at points with no
residual stress but subject to bending stress? [hint: i included a clue
about the answer - see if you can spot it.]
|
| | | | | | | | | | | | | | | | | | | | | |
Date: 08 Sep 2007 10:08:41
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> truth of the saying, "ignorance can be cured, stupid is forever".
>>
>> Just out of curiosity, I Googled to see where this was originally
>> explained to you.
>>
>> It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
>> good job. Apparently it didn't stick. I can see why Jobst no longer
>> bothers to respond.
>>
>> http://tinyurl.com/29v4u2
>
> you had to dig back /four years/ to find something that predated luns
> tee reminding us all of residual stress profiles?
I did a quick review of Luns' posts, I might have missed what you were
referring to. Do any of these ring a bell (all responses to your posts)?
" Quit your squirming. You change your tune every time I point
out how something in what you've said is impossible. This has nothing to
do with net stress across the spoke, this is about the net effect of
all applied forces at the inner surface of the spoke where you seem to
believe a neutral axis exists. Besides, what you point out here also
contradicts your claim of the neutral axis being at the surface: zero
tensile/compressive stress (definition of neutral axis) at the
surface, and tension through the whole spoke outside of that, is not a
net of zero across the spoke."
-Luns
" I see. You can't support your own arguments against a reasoned
analysis, so you hide behind an arbitrary stack of books instead."
-Luns
" What a load of hooey. The unyielded layer of the spoke would
happily return to being straight if not for forces applied to it by the
yielded material it's sandwiched between. The residual stresses found
within a spoke have a neutral plane in them.
I'll call your bluff: show me the way. If what you purport is so
readily found in a library, then you will have no problems citing a
text or journal paper that supports your fantasy of a neutral axis at
the surface of material being bent. If you aren't willing to come up
with a citation, then you _are_ hiding behind the only convenient
cover you have left.
The only argument you've offered for a neutral plane on the
surface of the material aside from flatly saying it just is, is your
example of the close-wound extension spring. This example proves nothing
either, these springs not being formed in the manner you seem to
believe. There is more than one way to form such a spring, and in fact,
if your own argument is to be believed, the scenario you describe is not
one of them either."
-Luns
" Translation: you're pulling stuff out of thin air, and now that
you can't support it any more, you pretend it's common knowledge and try
to make me do your homework for you. You're the one who needs to look up
bending mechanics. What you've purported is implausible and I've
explained - now past the point of repeating myself - exactly why, and
it's exactly why what you've been claiming will not be found in a
library. You're welcome to prove me wrong with a citation, but to tell
me to go the library to prove _your_ argument - one which I've already
explained to be fallacious and would not be found there - is as absurd
as demanding a certain regime surrender its non-existant weapons. "
" I knew this would be your next dodge. First you were arguing
that there is a neutral plane at the surface of the spoke and only
material on the outside of the bend yields. Now you're arguing the
entire spoke is in yield and there is no neutral plane. You keep
changing your story every time you get cornered without admitting what
you'd been claiming before is wrong, instead saying your new story is
what you meant all along. "
Seems like he had a typical "jim beam" experience.
More relevant to this thread:
" While we're at it.. please explain how insufficient spoke
tension causes spoke breakage. Inadequate tension produces an inferior
wheel, certainly, but the failure of low spoke tension is that spokes
go slack under load, allowing spoke nipples to rattle loose and the
wheel to then go out of true. Spoke breakage is not part of this, even
if it was more common at the time. But so were bell bottom pants.
Bell bottom pants cause spoke breakage!"
-Luns
In article <u6ydndG0Dvmxei3fRVn...@speakeasy.net >,
jim beam <nos...@example.net > wrote:
>slack spokes are not intrinsically less strong, and as you point out,
>their biggest problem is tendency to loosen, but there /is/ a
>reliability problem with them. it's caused by exaggerated bending as a
>result of their interaction with their crossing partner. spokes
>typically fatigue at the elbow as a result of bending - they are not
>axially loaded. if the motion they experience is exaggerated because of
>excessive [slack] spoke movement, and even further exaggerated by their
>[still taught] crossing partner creating even more lateral movement, the
>[bending] strain they experience at the elbow increases and their
>fatigue life correspondingly decreases.
If there were any truth to this, then left side spokes on rear
wheels would universally fatigue more than right side spokes do. My
experience with fatigued spokes has been consistently the opposite. My
experience with fatigued spokes also ended with stress releiving the
surviving spokes on the wheels that had failures, something which
should have made no effect according to your movement theory.
-Luns
I could go on, it gets worse...
|
| | | | | | | | | | | | | | | | | | | | | | |
Date: 09 Sep 2007 11:31:26
From: Michael Press
Subject: Re: Yet another broken spoke
|
In article
<tbydnQwnt-l3MX_bnZ2dnUVZ_jqdnZ2d@comcast.com >,
Peter Cole <peter_cole@comcast.net > wrote:
> jim beam wrote:
> > Peter Cole wrote:
> >> jim beam wrote:
>
> >>> truth of the saying, "ignorance can be cured, stupid is forever".
> >>
> >> Just out of curiosity, I Googled to see where this was originally
> >> explained to you.
> >>
> >> It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
> >> good job. Apparently it didn't stick. I can see why Jobst no longer
> >> bothers to respond.
> >>
> >> http://tinyurl.com/29v4u2
> >
> > you had to dig back /four years/ to find something that predated luns
> > tee reminding us all of residual stress profiles?
>
> I did a quick review of Luns' posts, I might have missed what you were
> referring to. Do any of these ring a bell (all responses to your posts)?
>
> " Quit your squirming. You change your tune every time I point
> out how something in what you've said is impossible. This has nothing to
> do with net stress across the spoke, this is about the net effect of
> all applied forces at the inner surface of the spoke where you seem to
> believe a neutral axis exists. Besides, what you point out here also
> contradicts your claim of the neutral axis being at the surface: zero
> tensile/compressive stress (definition of neutral axis) at the
> surface, and tension through the whole spoke outside of that, is not a
> net of zero across the spoke."
>
> -Luns
So, jb thinks that a spoke elbow with residual stresses
can have a neutral axis at the surface. Priceless.
--
Michael Press
|
| | | | | | | | | | | | | | | | | | | | | | | |
Date: 09 Sep 2007 21:09:29
From: jim beam
Subject: Re: Yet another broken spoke
|
Michael Press wrote:
> In article
> <tbydnQwnt-l3MX_bnZ2dnUVZ_jqdnZ2d@comcast.com>,
> Peter Cole <peter_cole@comcast.net> wrote:
>
>> jim beam wrote:
>>> Peter Cole wrote:
>>>> jim beam wrote:
>>>>> truth of the saying, "ignorance can be cured, stupid is forever".
>>>> Just out of curiosity, I Googled to see where this was originally
>>>> explained to you.
>>>>
>>>> It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
>>>> good job. Apparently it didn't stick. I can see why Jobst no longer
>>>> bothers to respond.
>>>>
>>>> http://tinyurl.com/29v4u2
>>> you had to dig back /four years/ to find something that predated luns
>>> tee reminding us all of residual stress profiles?
>> I did a quick review of Luns' posts, I might have missed what you were
>> referring to. Do any of these ring a bell (all responses to your posts)?
>>
>> " Quit your squirming. You change your tune every time I point
>> out how something in what you've said is impossible. This has nothing to
>> do with net stress across the spoke, this is about the net effect of
>> all applied forces at the inner surface of the spoke where you seem to
>> believe a neutral axis exists. Besides, what you point out here also
>> contradicts your claim of the neutral axis being at the surface: zero
>> tensile/compressive stress (definition of neutral axis) at the
>> surface, and tension through the whole spoke outside of that, is not a
>> net of zero across the spoke."
>>
>> -Luns
>
> So, jb thinks that a spoke elbow with residual stresses
> can have a neutral axis at the surface. Priceless.
>
don't put those [untrue] words in my mouth.
and you might benefit from re-reading what i actually /did/ say.
|
| | | | | | | | | | | | | | | | | | | | | | | | |
Date: 10 Sep 2007 21:00:44
From: Jambo
Subject: Re: Yet another broken spoke
|
"jim beam" <spamvortex@bad.example.net > wrote in message
news:Z_ednRZDG8XkXnnbnZ2dnUVZ_jqdnZ2d@speakeasy.net...
> Michael Press wrote:
>> So, jb thinks that a spoke elbow with residual stresses can have a
>> neutral axis at the surface. Priceless.
>>
>
> don't put those [untrue] words in my mouth.
>
> and you might benefit from re-reading what i actually /did/ say.
Er, that's what you DID say, fucktard!
|
| | | | | | | | | | | | | | | | | | | | | | | | | |
Date: 10 Sep 2007 18:21:59
From: Bill Sornson
Subject: Re: Yet another broken spoke
|
Jambo wrote:
> "jim beam" <spamvortex@bad.example.net> wrote in message
> news:Z_ednRZDG8XkXnnbnZ2dnUVZ_jqdnZ2d@speakeasy.net...
>> Michael Press wrote:
>
>>> So, jb thinks that a spoke elbow with residual stresses can have a
>>> neutral axis at the surface. Priceless.
>>>
>>
>> don't put those [untrue] words in my mouth.
>>
>> and you might benefit from re-reading what i actually /did/ say.
>
> Er, that's what you DID say, fucktard!
ENOUGH! PLONK!
|
| | | | | | | | | | | | | | | | | | | | | | | | | | |
Date: 11 Sep 2007 13:01:38
From: Jambo
Subject: Re: Yet another broken spoke
|
"Bill Sornson" <askme@ask.me > wrote in message
news:46e5edbc$0$15331$4c368faf@roadrunner.com...
> Jambo wrote:
>> Er, that's what you DID say, fucktard!
>
> ENOUGH! PLONK!
How upsetting to me, Paris. Can I call you Paris? As in Bill "Paris Hilton
of r.b.t." Sornson?
|
| | | | | | | | | | | | | | | | | | | | | | |
Date: 08 Sep 2007 07:55:03
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>
>>>> truth of the saying, "ignorance can be cured, stupid is forever".
>>>
>>> Just out of curiosity, I Googled to see where this was originally
>>> explained to you.
>>>
>>> It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
>>> good job. Apparently it didn't stick. I can see why Jobst no longer
>>> bothers to respond.
>>>
>>> http://tinyurl.com/29v4u2
>>
>> you had to dig back /four years/ to find something that predated luns
>> tee reminding us all of residual stress profiles?
>
> I did a quick review of Luns' posts, I might have missed what you were
> referring to. Do any of these ring a bell (all responses to your posts)?
>
> " Quit your squirming. You change your tune every time I point
> out how something in what you've said is impossible. This has nothing to
> do with net stress across the spoke, this is about the net effect of
> all applied forces at the inner surface of the spoke where you seem to
> believe a neutral axis exists. Besides, what you point out here also
> contradicts your claim of the neutral axis being at the surface: zero
> tensile/compressive stress (definition of neutral axis) at the
> surface, and tension through the whole spoke outside of that, is not a
> net of zero across the spoke."
>
> -Luns
>
>
> " I see. You can't support your own arguments against a reasoned
> analysis, so you hide behind an arbitrary stack of books instead."
>
> -Luns
>
> " What a load of hooey. The unyielded layer of the spoke would
> happily return to being straight if not for forces applied to it by the
> yielded material it's sandwiched between. The residual stresses found
> within a spoke have a neutral plane in them.
>
> I'll call your bluff: show me the way. If what you purport is so
> readily found in a library, then you will have no problems citing a
> text or journal paper that supports your fantasy of a neutral axis at
> the surface of material being bent. If you aren't willing to come up
> with a citation, then you _are_ hiding behind the only convenient
> cover you have left.
>
> The only argument you've offered for a neutral plane on the
> surface of the material aside from flatly saying it just is, is your
> example of the close-wound extension spring. This example proves nothing
> either, these springs not being formed in the manner you seem to
> believe. There is more than one way to form such a spring, and in fact,
> if your own argument is to be believed, the scenario you describe is not
> one of them either."
>
> -Luns
>
>
> " Translation: you're pulling stuff out of thin air, and now that
> you can't support it any more, you pretend it's common knowledge and try
> to make me do your homework for you. You're the one who needs to look up
> bending mechanics. What you've purported is implausible and I've
> explained - now past the point of repeating myself - exactly why, and
> it's exactly why what you've been claiming will not be found in a
> library. You're welcome to prove me wrong with a citation, but to tell
> me to go the library to prove _your_ argument - one which I've already
> explained to be fallacious and would not be found there - is as absurd
> as demanding a certain regime surrender its non-existant weapons. "
>
> " I knew this would be your next dodge. First you were arguing
> that there is a neutral plane at the surface of the spoke and only
> material on the outside of the bend yields. Now you're arguing the
> entire spoke is in yield and there is no neutral plane. You keep
> changing your story every time you get cornered without admitting what
> you'd been claiming before is wrong, instead saying your new story is
> what you meant all along. "
>
>
> Seems like he had a typical "jim beam" experience.
>
> More relevant to this thread:
>
>
> " While we're at it.. please explain how insufficient spoke
> tension causes spoke breakage. Inadequate tension produces an inferior
> wheel, certainly, but the failure of low spoke tension is that spokes
> go slack under load, allowing spoke nipples to rattle loose and the
> wheel to then go out of true. Spoke breakage is not part of this, even
> if it was more common at the time. But so were bell bottom pants.
>
> Bell bottom pants cause spoke breakage!"
>
> -Luns
>
> In article <u6ydndG0Dvmxei3fRVn...@speakeasy.net>,
> jim beam <nos...@example.net> wrote:
>
> >slack spokes are not intrinsically less strong, and as you point out,
> >their biggest problem is tendency to loosen, but there /is/ a
> >reliability problem with them. it's caused by exaggerated bending as a
> >result of their interaction with their crossing partner. spokes
> >typically fatigue at the elbow as a result of bending - they are not
> >axially loaded. if the motion they experience is exaggerated because of
> >excessive [slack] spoke movement, and even further exaggerated by their
> >[still taught] crossing partner creating even more lateral movement, the
> >[bending] strain they experience at the elbow increases and their
> >fatigue life correspondingly decreases.
>
> If there were any truth to this, then left side spokes on rear
> wheels would universally fatigue more than right side spokes do. My
> experience with fatigued spokes has been consistently the opposite. My
> experience with fatigued spokes also ended with stress releiving the
> surviving spokes on the wheels that had failures, something which
> should have made no effect according to your movement theory.
>
> -Luns
>
> I could go on, it gets worse...
why don't you post from the jobstian library instead? his is much more
lengthy. you should try quoting that idiot krygowski some time too.
he's an engineering professor you know. or at least, it picks up an
engineering professor's paycheck.
as for luns, he's made some valuable contributions. but he's made some
mistakes too, most notably on the subject of strain aging materials. he
holds back a lot of stuff too - spoke tensiometer math for example. but
you don't quote that. why not? too intent on being a prick to bother?
|
| | | | | | | | | | | | | | | | | | | | | | | |
Date: 08 Sep 2007 15:22:30
From: Jambo
Subject: Re: Yet another broken spoke
|
"jim beam" <spamvortex@bad.example.net > wrote in message
news:xeGdnSimKdlVKn_bnZ2dnUVZ_qqgnZ2d@speakeasy.net...
> as for luns, he's made some valuable contributions. but he's made some
> mistakes too, most notably on the subject of strain aging materials. he
> holds back a lot of stuff too - spoke tensiometer math for example. but
> you don't quote that. why not? too intent on being a prick to bother?
Here's a quote on maths:
"for a 6061 with E = 69GPa, and 275MPa yield, that gives an elastic
deformation limit of 0.275/69 x 100% = 0.04%."
Then you go on to base a whole bullshit argument on that embarrasingly
erroneous calculation.
HAHAHAHAHAHA! And you have the gall to talk about tensiometer math from an
expert? When you can't even do simple math?
Fucktard.
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Date: 09 Sep 2007 08:19:57
From: jim beam
Subject: Re: Yet another broken spoke
|
Jambo wrote:
> "jim beam" <spamvortex@bad.example.net> wrote in message
> news:xeGdnSimKdlVKn_bnZ2dnUVZ_qqgnZ2d@speakeasy.net...
>> as for luns, he's made some valuable contributions. but he's made some
>> mistakes too, most notably on the subject of strain aging materials. he
>> holds back a lot of stuff too - spoke tensiometer math for example. but
>> you don't quote that. why not? too intent on being a prick to bother?
>
> Here's a quote on maths:
>
> "for a 6061 with E = 69GPa, and 275MPa yield, that gives an elastic
> deformation limit of 0.275/69 x 100% = 0.04%."
>
> Then you go on to base a whole bullshit argument on that embarrasingly
> erroneous calculation.
>
> HAHAHAHAHAHA! And you have the gall to talk about tensiometer math from an
> expert? When you can't even do simple math?
>
> Fucktard.
>
>
all that for a typo? funny! if i'd gotten a fundamental principle
wrong, oh, let's just pick one at random, like definition of modulus! -
now /that/ would be fucking moronic. oh, wait, that's you.
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Date: 09 Sep 2007 12:11:33
From: Jambo
Subject: Re: Yet another broken spoke
|
"jim beam" <spamvortex@bad.example.net > wrote in message
news:udSdnczHnd2DknnbnZ2dnUVZ_uqvnZ2d@speakeasy.net...
> Jambo wrote:
>> "jim beam" <spamvortex@bad.example.net> wrote in message
>> news:xeGdnSimKdlVKn_bnZ2dnUVZ_qqgnZ2d@speakeasy.net...
>>> as for luns, he's made some valuable contributions. but he's made some
>>> mistakes too, most notably on the subject of strain aging materials. he
>>> holds back a lot of stuff too - spoke tensiometer math for example. but
>>> you don't quote that. why not? too intent on being a prick to bother?
>>
>> Here's a quote on maths:
>>
>> "for a 6061 with E = 69GPa, and 275MPa yield, that gives an elastic
>> deformation limit of 0.275/69 x 100% = 0.04%."
>>
>> Then you go on to base a whole bullshit argument on that embarrasingly
>> erroneous calculation.
>>
>> HAHAHAHAHAHA! And you have the gall to talk about tensiometer math from
>> an expert? When you can't even do simple math?
>>
>> Fucktard.
>
> all that for a typo? funny! if i'd gotten a fundamental principle wrong,
> oh, let's just pick one at random, like definition of modulus! - now
> /that/ would be fucking moronic. oh, wait, that's you.
A typo? Let me give you a definition - a typo is a mis-type. Implicit in
this is that you had your fact correct, but mis-typed it. That's a typo.
When you based you whole bullshit argument on this "typo", it's not a typo
at all, but a MISTAKE in fact!
You're a lying fucktard!
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Date: 08 Sep 2007 14:27:08
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> you had to dig back /four years/ to find something that predated luns
>>> tee reminding us all of residual stress profiles?
>>
>> I did a quick review of Luns' posts, I might have missed what you were
>> referring to. Do any of these ring a bell (all responses to your posts)?
>>
>> " Quit your squirming."
>> " What a load of hooey. "
>> " Translation: you're pulling stuff out of thin air,"
>> " I knew this would be your next dodge."
>> Seems like he had a typical "jim beam" experience.
>
>
> why don't you post from the jobstian library instead? his is much more
> lengthy. you should try quoting that idiot krygowski some time too.
> he's an engineering professor you know. or at least, it picks up an
> engineering professor's paycheck.
Your reference to Luns, not mine.
>
> as for luns, he's made some valuable contributions. but he's made some
> mistakes too, most notably on the subject of strain aging materials. he
> holds back a lot of stuff too - spoke tensiometer math for example. but
> you don't quote that.
Not relevant to the current thread. How do I quote something he "holds
back" anyway? (just curious).
why not? too intent on being a prick to bother?
Uh oh, nasty name time. Everybody knows what this means.
|
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Date: 09 Sep 2007 08:12:47
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>
>>>> you had to dig back /four years/ to find something that predated
>>>> luns tee reminding us all of residual stress profiles?
>>>
>>> I did a quick review of Luns' posts, I might have missed what you
>>> were referring to. Do any of these ring a bell (all responses to your
>>> posts)?
>>>
>>> " Quit your squirming." " What a load of hooey. "
>>> " Translation: you're pulling stuff out of thin air,"
>>> " I knew this would be your next dodge."
>
>>> Seems like he had a typical "jim beam" experience.
>>
>>
>> why don't you post from the jobstian library instead? his is much
>> more lengthy. you should try quoting that idiot krygowski some time
>> too. he's an engineering professor you know. or at least, it picks up
>> an engineering professor's paycheck.
>
> Your reference to Luns, not mine.
>
>>
>> as for luns, he's made some valuable contributions. but he's made
>> some mistakes too, most notably on the subject of strain aging
>> materials. he holds back a lot of stuff too - spoke tensiometer math
>> for example. but you don't quote that.
>
> Not relevant to the current thread.
whoops, not convenient!!! /so/ sorry.
> How do I quote something he "holds
> back" anyway? (just curious).
>
>
> why not? too intent on being a prick to bother?
>
> Uh oh, nasty name time. Everybody knows what this means.
yes, it means that you're trying to wriggle, squirm and deceive and that
i'm calling you for what you are!
|
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Date: 09 Sep 2007 13:39:53
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>>> jim beam wrote:
>>
>>>>> you had to dig back /four years/ to find something that predated
>>>>> luns tee reminding us all of residual stress profiles?
>>>>
>>>> I did a quick review of Luns' posts, I might have missed what you
>>>> were referring to. Do any of these ring a bell (all responses to
>>>> your posts)?
>>>>
>>>> " Quit your squirming." " What a load of hooey. "
>>>> " Translation: you're pulling stuff out of thin air,"
>>>> " I knew this would be your next dodge."
>>
>>>> Seems like he had a typical "jim beam" experience.
>>>
>>>
>>> why don't you post from the jobstian library instead? his is much
>>> more lengthy. you should try quoting that idiot krygowski some time
>>> too. he's an engineering professor you know. or at least, it picks
>>> up an engineering professor's paycheck.
>>
>> Your reference to Luns, not mine.
>>
>>>
>>> as for luns, he's made some valuable contributions. but he's made
>>> some mistakes too, most notably on the subject of strain aging
>>> materials. he holds back a lot of stuff too - spoke tensiometer math
>>> for example. but you don't quote that.
>>
>> Not relevant to the current thread.
>
> whoops, not convenient!!! /so/ sorry.
OT, in other words (your specialty).
>
>
>> How do I quote something he "holds back" anyway? (just curious).
>>
>>
>> why not? too intent on being a prick to bother?
>>
>> Uh oh, nasty name time. Everybody knows what this means.
>
> yes, it means that you're trying to wriggle, squirm and deceive and that
> i'm calling you for what you are!
No, it means you've run out of argument. You're nothing if not predictable.
|
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Date: 07 Sep 2007 15:30:08
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-07, Peter Cole <peter_cole@comcast.net > wrote:
[...]
> It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
> good job. Apparently it didn't stick. I can see why Jobst no longer
> bothers to respond.
>
> http://tinyurl.com/29v4u2
OK I have a question.
jim beam > i have ignored residual stress as a factor in these failures
jim beam > because the majority of the fractures i've examined initiate
jim beam > on the /inside/ of the spoke elbow bend, not the outside
jim beam > [although i have examples of each]. residual stress in this
jim beam > location is compressive so i'm just looking at the external
jim beam > [+cyclic] load.
Mike Prime > The inside of the spoke elbow will have TENSILE residual
Mike Prime > stress, not compressive, because of the elastic springback
Mike Prime > after bending. See below. That 0.5 Sy number is for a beam;
Mike Prime > I'm too lazy to derive the number for a circular cross
Mike Prime > section right now.
Mike Prime > Since that location has tensile residual stress, tensile
Mike Prime > applied mean stress from the spoke tension and bending,
^^^^^^^
Is the _applied_ stress on the inside of the elbow from spoke tension
and bending really tensile?
I don't understand that. I thought when you bent a wire you got tensile
stress on the outside of the bend and compressive on the inside?
I know that the residual stress, after it springs back, is tensile on
the inside.
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Date: 07 Sep 2007 19:13:09
From: Peter Cole
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
> [...]
>> It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
>> good job. Apparently it didn't stick. I can see why Jobst no longer
>> bothers to respond.
>>
>> http://tinyurl.com/29v4u2
>
> OK I have a question.
>
> jim beam> i have ignored residual stress as a factor in these failures
> jim beam> because the majority of the fractures i've examined initiate
> jim beam> on the /inside/ of the spoke elbow bend, not the outside
> jim beam> [although i have examples of each]. residual stress in this
> jim beam> location is compressive so i'm just looking at the external
> jim beam> [+cyclic] load.
>
> Mike Prime> The inside of the spoke elbow will have TENSILE residual
> Mike Prime> stress, not compressive, because of the elastic springback
> Mike Prime> after bending. See below. That 0.5 Sy number is for a beam;
> Mike Prime> I'm too lazy to derive the number for a circular cross
> Mike Prime> section right now.
>
> Mike Prime> Since that location has tensile residual stress, tensile
> Mike Prime> applied mean stress from the spoke tension and bending,
> ^^^^^^^
>
> Is the _applied_ stress on the inside of the elbow from spoke tension
> and bending really tensile?
>
> I don't understand that. I thought when you bent a wire you got tensile
> stress on the outside of the bend and compressive on the inside?
>
> I know that the residual stress, after it springs back, is tensile on
> the inside.
If the spoke has no bending moment (perfectly supported, perfect path),
the applied stress from spoke tension will be tensile (uniform) across
the cross section. Whatever bending force that is also present will add
to that. The bending force can be either way depending on angular
mismatch. If the spoke elbow is too long, another bending force will act
to open the spoke angle further, adding to the residual (mfg) stress.
The worst case would be an (initial spoke) angle too acute with elbow
too long. Both of those factors plus residual stress would all put
tension on the inside of the elbow.
If the spoke elbows are the right length, and the spoke angle is
corrected, the only significant stresses should be spoke tension and
residual. By stress relieving, the residual is reduced to non-fatiguing
levels. But, if the spoke has (tensile) stress levels near yield in
parts of the cross section, those will be reduced as they are forced to
yield by the momentary overload -- whatever the source. It's a "can't
lose" proposition.
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Date: 08 Sep 2007 04:43:39
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-07, Peter Cole <peter_cole@comcast.net > wrote:
[...]
> If the spoke has no bending moment (perfectly supported, perfect path),
> the applied stress from spoke tension will be tensile (uniform) across
> the cross section.
I think I basically agree with this, though not absolutely. If the spoke
is perfectly supported, but being pulled around a corner, there will
surely still be a bending moment on parts of the spoke, but the distance
component of that moment will never be greater than half the diameter of
the spoke.
Moments that small (assuming the force is in the range of normal spoke
tensions) are low enough not to worry about-- they're not bringing
anything anywhere near dangerously high stress levels for fatigue.
> Whatever bending force that is also present will add
> to that. The bending force can be either way depending on angular
> mismatch. If the spoke elbow is too long, another bending force will act
> to open the spoke angle further, adding to the residual (mfg) stress.
>
> The worst case would be an (initial spoke) angle too acute with elbow
> too long. Both of those factors plus residual stress would all put
> tension on the inside of the elbow.
Yes, in that case residual stress from forming would be the same way
around as applied bending from spoke tension-- i.e. compressive outside
the bend, tensile inside.
> If the spoke elbows are the right length, and the spoke angle is
> corrected, the only significant stresses should be spoke tension and
> residual.
But if you correct the spoke angle, you're changing things right? It was
bent in the factory by a little piston or whatever, and wants to spring
back, leaving it with residual stresses. Then you go and bend it again
to make the elbow a bit bigger or smaller. What happens to the residual
stresses from the factory?
I imagine they reduce greatly in magnitude and move around a bit. I
imagine you'd have to hunt around quite a bit with the X-ray diffractor
to find them and distinguish them from the new applied stresses you've
just put in.
> By stress relieving, the residual is reduced to non-fatiguing levels.
> But, if the spoke has (tensile) stress levels near yield in parts of
> the cross section, those will be reduced as they are forced to yield
> by the momentary overload -- whatever the source. It's a "can't lose"
> proposition.
I would have thought so, yes, unless you really overdo it.
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Date: 08 Sep 2007 11:19:18
From: Peter Cole
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
> [...]
>> If the spoke has no bending moment (perfectly supported, perfect path),
>> the applied stress from spoke tension will be tensile (uniform) across
>> the cross section.
>
> I think I basically agree with this, though not absolutely. If the spoke
> is perfectly supported, but being pulled around a corner, there will
> surely still be a bending moment on parts of the spoke, but the distance
> component of that moment will never be greater than half the diameter of
> the spoke.
>
It's theoretically possible to have the elbow perfectly supported such
that there would be no moment. In practice, there must be a little slop
to lace with.
> Moments that small (assuming the force is in the range of normal spoke
> tensions) are low enough not to worry about-- they're not bringing
> anything anywhere near dangerously high stress levels for fatigue.
>
>> Whatever bending force that is also present will add
>> to that. The bending force can be either way depending on angular
>> mismatch. If the spoke elbow is too long, another bending force will act
>> to open the spoke angle further, adding to the residual (mfg) stress.
>>
>> The worst case would be an (initial spoke) angle too acute with elbow
>> too long. Both of those factors plus residual stress would all put
>> tension on the inside of the elbow.
>
> Yes, in that case residual stress from forming would be the same way
> around as applied bending from spoke tension-- i.e. compressive outside
> the bend, tensile inside.
>
>> If the spoke elbows are the right length, and the spoke angle is
>> corrected, the only significant stresses should be spoke tension and
>> residual.
>
> But if you correct the spoke angle, you're changing things right? It was
> bent in the factory by a little piston or whatever, and wants to spring
> back, leaving it with residual stresses. Then you go and bend it again
> to make the elbow a bit bigger or smaller. What happens to the residual
> stresses from the factory?
Typically, you're correcting the spoke angle on the outbound spokes,
closing the angle slightly. I doubt that this reduces residual
manufacturing stresses.
> I imagine they reduce greatly in magnitude and move around a bit. I
> imagine you'd have to hunt around quite a bit with the X-ray diffractor
> to find them and distinguish them from the new applied stresses you've
> just put in.
Reversing the bend direction and lowering the magnitude cyclically to
zero is a way of straightening wire. I would imagine that this would
reduce residuals, but I don't know for sure.
>
>> By stress relieving, the residual is reduced to non-fatiguing levels.
>> But, if the spoke has (tensile) stress levels near yield in parts of
>> the cross section, those will be reduced as they are forced to yield
>> by the momentary overload -- whatever the source. It's a "can't lose"
>> proposition.
>
> I would have thought so, yes, unless you really overdo it.
It's pretty impossible to overdo it, your hands aren't strong enough.
|
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Date: 08 Sep 2007 12:03:27
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-08, Peter Cole <peter_cole@comcast.net > wrote:
> Ben C wrote:
>> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>> [...]
>>> If the spoke has no bending moment (perfectly supported, perfect path),
>>> the applied stress from spoke tension will be tensile (uniform) across
>>> the cross section.
>>
>> I think I basically agree with this, though not absolutely. If the spoke
>> is perfectly supported, but being pulled around a corner, there will
>> surely still be a bending moment on parts of the spoke, but the distance
>> component of that moment will never be greater than half the diameter of
>> the spoke.
>>
>
> It's theoretically possible to have the elbow perfectly supported such
> that there would be no moment.
If the spoke goes round a corner and you pull on it, then the corner
will resist the pull and you will have (I think) compression on that
side-- the inside of the bend-- and tension on the outside. So that is a
sort of moment, depending on where you measure things from.
If you have a bad surface covered uniformly with defects, but a well
supported spoke you still might see fatigue starting on the outside of
the bend where the tensile stress in use is the highest. I think this is
what jim beam was saying in another post.
> In practice, there must be a little slop to lace with.
Yes, and in practice nothing's ever perfect anyway.
[...]
>> But if you correct the spoke angle, you're changing things right? It was
>> bent in the factory by a little piston or whatever, and wants to spring
>> back, leaving it with residual stresses. Then you go and bend it again
>> to make the elbow a bit bigger or smaller. What happens to the residual
>> stresses from the factory?
>
> Typically, you're correcting the spoke angle on the outbound spokes,
> closing the angle slightly. I doubt that this reduces residual
> manufacturing stresses.
But isn't the residual manufacturing stress on the skin of the spoke
on the outside of the elbow compressive? So tightening the angle will
put a tensile stress there, overcoming the residual compressive stress
and then yielding the material in a tensile way?
[...]
>>> By stress relieving, the residual is reduced to non-fatiguing levels.
>>> But, if the spoke has (tensile) stress levels near yield in parts of
>>> the cross section, those will be reduced as they are forced to yield
>>> by the momentary overload -- whatever the source. It's a "can't lose"
>>> proposition.
>>
>> I would have thought so, yes, unless you really overdo it.
>
> It's pretty impossible to overdo it, your hands aren't strong enough.
Yes I think so, as you're only going to yield the portions that are
close to yield already. To yield a well supported spoke takes much more
force.
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Date: 08 Sep 2007 15:05:17
From: Peter Cole
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-08, Peter Cole <peter_cole@comcast.net> wrote:
>> Ben C wrote:
>>> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>>> [...]
>>>> If the spoke has no bending moment (perfectly supported, perfect path),
>>>> the applied stress from spoke tension will be tensile (uniform) across
>>>> the cross section.
>>> I think I basically agree with this, though not absolutely. If the spoke
>>> is perfectly supported, but being pulled around a corner, there will
>>> surely still be a bending moment on parts of the spoke, but the distance
>>> component of that moment will never be greater than half the diameter of
>>> the spoke.
>>>
>> It's theoretically possible to have the elbow perfectly supported such
>> that there would be no moment.
>
> If the spoke goes round a corner and you pull on it, then the corner
> will resist the pull and you will have (I think) compression on that
> side-- the inside of the bend-- and tension on the outside. So that is a
> sort of moment, depending on where you measure things from.
Think of it as a bundle of fibers, give the corner a radius.
>
> If you have a bad surface covered uniformly with defects, but a well
> supported spoke you still might see fatigue starting on the outside of
> the bend where the tensile stress in use is the highest. I think this is
> what jim beam was saying in another post.
Sure, stress + defect = failure, see it all the time with nicked spokes.
>
>> In practice, there must be a little slop to lace with.
>
> Yes, and in practice nothing's ever perfect anyway.
>
> [...]
>>> But if you correct the spoke angle, you're changing things right? It was
>>> bent in the factory by a little piston or whatever, and wants to spring
>>> back, leaving it with residual stresses. Then you go and bend it again
>>> to make the elbow a bit bigger or smaller. What happens to the residual
>>> stresses from the factory?
>> Typically, you're correcting the spoke angle on the outbound spokes,
>> closing the angle slightly. I doubt that this reduces residual
>> manufacturing stresses.
>
> But isn't the residual manufacturing stress on the skin of the spoke
> on the outside of the elbow compressive? So tightening the angle will
> put a tensile stress there, overcoming the residual compressive stress
> and then yielding the material in a tensile way?
You correct the angle before you tension. In that case, it's just like
the mfr. bending, just a little more.
>
> [...]
>>>> By stress relieving, the residual is reduced to non-fatiguing levels.
>>>> But, if the spoke has (tensile) stress levels near yield in parts of
>>>> the cross section, those will be reduced as they are forced to yield
>>>> by the momentary overload -- whatever the source. It's a "can't lose"
>>>> proposition.
>>> I would have thought so, yes, unless you really overdo it.
>> It's pretty impossible to overdo it, your hands aren't strong enough.
>
> Yes I think so, as you're only going to yield the portions that are
> close to yield already. To yield a well supported spoke takes much more
> force.
|
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Date: 08 Sep 2007 18:01:01
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-08, Peter Cole <peter_cole@comcast.net > wrote:
> Ben C wrote:
[...]
>> But isn't the residual manufacturing stress on the skin of the spoke
>> on the outside of the elbow compressive? So tightening the angle will
>> put a tensile stress there, overcoming the residual compressive stress
>> and then yielding the material in a tensile way?
>
> You correct the angle before you tension. In that case, it's just like
> the mfr. bending, just a little more.
Not according to my understanding of Jobst's earlier explanation. His
point was that the spoke line correction bend doesn't get a chance to
spring back because the spoke is installed in the wheel and the elbow
can't be overbent because the flange is in the way. So its stress will
remain tensile on the outside of the bend (outbound spoke).
Mfr bending on the other hand does get to spring back, which is why
you'd get compressive outside the bend and tensile inside.
|
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Date: 09 Sep 2007 00:39:51
From:
Subject: Re: Yet another broken spoke
|
Ben C? writes:
>>> But isn't the residual manufacturing stress on the skin of the
>>> spoke on the outside of the elbow compressive? So tightening the
>>> angle will put a tensile stress there, overcoming the residual
>>> compressive stress and then yielding the material in a tensile
>>> way?
>> You correct the angle before you tension. In that case, it's just
>> like the mfr. bending, just a little more.
> Not according to my understanding of Jobst's earlier explanation.
> His point was that the spoke line correction bend doesn't get a
> chance to spring back because the spoke is installed in the wheel
> and the elbow can't be overbent because the flange is in the way.
> So its stress will remain tensile on the outside of the bend
> (outbound spoke).
> Mfr bending on the other hand does get to spring back, which is why
> you'd get compressive outside the bend and tensile inside.
By pressing outbound spokes against the flange the space between the
elbow bend and the flange is reduced to a small gap that is closed by
tension. There is no cyclic motion any more as there is with a
stand-off spoke and the stress is lowered by stress relief.
Jobst Brandt
|
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Date: 09 Sep 2007 06:54:12
From: jim beam
Subject: Re: Yet another broken spoke
|
jobst.brandt@stanfordalumni.org wrote:
> Ben C? writes:
>
>>>> But isn't the residual manufacturing stress on the skin of the
>>>> spoke on the outside of the elbow compressive? So tightening the
>>>> angle will put a tensile stress there, overcoming the residual
>>>> compressive stress and then yielding the material in a tensile
>>>> way?
>
>>> You correct the angle before you tension. In that case, it's just
>>> like the mfr. bending, just a little more.
>
>> Not according to my understanding of Jobst's earlier explanation.
>> His point was that the spoke line correction bend doesn't get a
>> chance to spring back because the spoke is installed in the wheel
>> and the elbow can't be overbent because the flange is in the way.
>> So its stress will remain tensile on the outside of the bend
>> (outbound spoke).
>
>> Mfr bending on the other hand does get to spring back, which is why
>> you'd get compressive outside the bend and tensile inside.
>
> By pressing outbound spokes against the flange the space between the
> elbow bend and the flange is reduced to a small gap that is closed by
> tension.
only on heads-in spokes, and only if the spoke/flange geometry permits.
heads-out spokes have no such gap closing.
> There is no cyclic motion any more as there is with a
> stand-off spoke and the stress is lowered by stress relief.
yes there is - by definition. the spoke elbow is offset from its axis
and the spoke shaft is not rigidly attached to the hub flange, even if
it touches. the elasticity that you happily cite in other situations as
causing fretting is still at work here - and elastic distortion means
stress cycling at the bend - by definition. stress cycling at the bend
means fatigue. and examination of the fracture surface tells you the
whole story. you should try it some time.
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Date: 08 Sep 2007 08:51:37
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> Ben C wrote:
<snip for clarity >
>> I would have thought so, yes, unless you really overdo it.
>
> It's pretty impossible to overdo it, your hands aren't strong enough.
eh? translation: "it yields to cause 'stress relief' but it doesn't
yield if that interferes with my ability to argue."
what a crock of shit.
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Date: 08 Sep 2007 14:32:34
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> Ben C wrote:
> <snip for clarity>
>
>>> I would have thought so, yes, unless you really overdo it.
>>
>> It's pretty impossible to overdo it, your hands aren't strong enough.
>
> eh? translation: "it yields to cause 'stress relief' but it doesn't
> yield if that interferes with my ability to argue."
>
> what a crock of shit.
Mechanical stress relief is a well known technique. Go back to the Luns
post where he explains it, or to any of the cites I have provided over
the *years* -- or just keep hurling vulgarities, whatever.
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Date: 08 Sep 2007 12:07:09
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-08, jim beam <spamvortex@bad.example.net > wrote:
> Peter Cole wrote:
>> Ben C wrote:
><snip for clarity>
>
>>> I would have thought so, yes, unless you really overdo it.
>>
>> It's pretty impossible to overdo it, your hands aren't strong enough.
>
> eh? translation: "it yields to cause 'stress relief' but it doesn't
> yield if that interferes with my ability to argue."
Isn't the point that if part of the spoke is close to yield, because
it's just been bent while you were building the wheel, then you can
bring that part up to yield with a relatively small amount more force?
Of course the only reason you can ever yield a spoke with your hands is
by bending it. As you yield it some more, the configuration changes and
the moment is reduced. So it's difficult to over-yield it. It's not like
bending a coathanger backwards and forwards.
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Date: 08 Sep 2007 10:54:03
From: jim beam
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-08, jim beam <spamvortex@bad.example.net> wrote:
>> Peter Cole wrote:
>>> Ben C wrote:
>> <snip for clarity>
>>
>>>> I would have thought so, yes, unless you really overdo it.
>>> It's pretty impossible to overdo it, your hands aren't strong enough.
>> eh? translation: "it yields to cause 'stress relief' but it doesn't
>> yield if that interferes with my ability to argue."
>
> Isn't the point that if part of the spoke is close to yield, because
> it's just been bent while you were building the wheel, then you can
> bring that part up to yield with a relatively small amount more force?
but you can do that just by tensioning the spokes in the first place.
and you'll never eliminate residual stress unless you do so thermally.
that's not acceptable because it destroys the materials strength. and
it makes no practical difference since the fatigue is not initiating
from a region of high residual stress.
>
> Of course the only reason you can ever yield a spoke with your hands is
> by bending it. As you yield it some more, the configuration changes and
> the moment is reduced. So it's difficult to over-yield it.
but yield /introduces/ residual stress!!!
> It's not like
> bending a coathanger backwards and forwards.
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Date: 08 Sep 2007 13:17:16
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-08, jim beam <spamvortex@bad.example.net > wrote:
> Ben C wrote:
[...]
>> Of course the only reason you can ever yield a spoke with your hands is
>> by bending it. As you yield it some more, the configuration changes and
>> the moment is reduced. So it's difficult to over-yield it.
>
> but yield /introduces/ residual stress!!!
If you (a) bend a wire round a bolt the way Carl did for his heating
experiments, and then, having bent it, you (b) give it a further good
hard pull on both ends, and then relax that to (c) just enough pull to
hold the wire in place, won't you end up with fewer regions of high
stress than if you did (a) and (c) without (b)?
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Date: 09 Sep 2007 06:57:03
From: jim beam
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-08, jim beam <spamvortex@bad.example.net> wrote:
>> Ben C wrote:
> [...]
>>> Of course the only reason you can ever yield a spoke with your hands is
>>> by bending it. As you yield it some more, the configuration changes and
>>> the moment is reduced. So it's difficult to over-yield it.
>> but yield /introduces/ residual stress!!!
>
> If you (a) bend a wire round a bolt the way Carl did for his heating
> experiments, and then, having bent it, you (b) give it a further good
> hard pull on both ends, and then relax that to (c) just enough pull to
> hold the wire in place, won't you end up with fewer regions of high
> stress than if you did (a) and (c) without (b)?
maybe, maybe not. it's easy to introduce _more_ residual stress. and
if "stress relief" is not precise and controlled, what hope does the
average joe wheelbuilder have of getting it right? absent data [which
of course will never be provided because it poses a risk of destroying
the legend], we'll never know.
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Date: 08 Sep 2007 07:21:04
From: jim beam
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
> [...]
>> If the spoke has no bending moment (perfectly supported, perfect path),
>> the applied stress from spoke tension will be tensile (uniform) across
>> the cross section.
>
> I think I basically agree with this, though not absolutely. If the spoke
> is perfectly supported, but being pulled around a corner, there will
> surely still be a bending moment on parts of the spoke, but the distance
> component of that moment will never be greater than half the diameter of
> the spoke.
>
> Moments that small (assuming the force is in the range of normal spoke
> tensions) are low enough not to worry about-- they're not bringing
> anything anywhere near dangerously high stress levels for fatigue.
don't forget, virtually every fatigue failure there's ever been is
because of "unanticipated" factors. just because stress levels aren't
/thought/ to be high, *observed failures* tell us that there /is/
bending sufficient to cause fatigue!!!
>
>> Whatever bending force that is also present will add
>> to that. The bending force can be either way depending on angular
>> mismatch. If the spoke elbow is too long, another bending force will act
>> to open the spoke angle further, adding to the residual (mfg) stress.
>>
>> The worst case would be an (initial spoke) angle too acute with elbow
>> too long. Both of those factors plus residual stress would all put
>> tension on the inside of the elbow.
>
> Yes, in that case residual stress from forming would be the same way
> around as applied bending from spoke tension-- i.e. compressive outside
> the bend, tensile inside.
see other post about profiles.
>
>> If the spoke elbows are the right length, and the spoke angle is
>> corrected, the only significant stresses should be spoke tension and
>> residual.
>
> But if you correct the spoke angle, you're changing things right? It was
> bent in the factory by a little piston or whatever, and wants to spring
> back, leaving it with residual stresses. Then you go and bend it again
> to make the elbow a bit bigger or smaller. What happens to the residual
> stresses from the factory?
>
> I imagine they reduce greatly in magnitude and move around a bit. I
> imagine you'd have to hunt around quite a bit with the X-ray diffractor
> to find them and distinguish them from the new applied stresses you've
> just put in.
see other post on profiles. since residual stress profiles are observed
/not/ to be a factor in fatigue, further discussion is pointless -
unless applied stresses are discussed also.
>
>> By stress relieving, the residual is reduced to non-fatiguing levels.
>> But, if the spoke has (tensile) stress levels near yield in parts of
>> the cross section, those will be reduced as they are forced to yield
>> by the momentary overload -- whatever the source. It's a "can't lose"
>> proposition.
>
> I would have thought so, yes, unless you really overdo it.
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Date: 08 Sep 2007 13:56:41
From: Jambo
Subject: Re: Yet another broken spoke
|
"jim beam" <spamvortex@bad.example.net > wrote in message
news:J5ydnZLRCbRMMn_bnZ2dnUVZ_hCdnZ2d@speakeasy.net...
> don't forget, virtually every fatigue failure there's ever been is because
> of "unanticipated" factors.
Just like "almost every bike uses CF forks"?
> just because stress levels aren't /thought/ to be high, *observed
> failures* tell us that there /is/ bending sufficient to cause fatigue!!!
Then in that case stress levels are INDEED high, that's the only reason to
cause fatigue, dumbass.
> see other post on profiles. since residual stress profiles are observed
> /not/ to be a factor in fatigue, further discussion is pointless - unless
> applied stresses are discussed also.
Bullshit again. Residual stresses figure prominently in fatigue, especially
if the stress levels are high. Ever hear of shot peening?
>> I would have thought so, yes, unless you really overdo it.
Well we all know what your thoughts are worth (clue: it ain't above zilch).
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Date: 08 Sep 2007 11:20:32
From: jim beam
Subject: Re: Yet another broken spoke
|
Jambo wrote:
> "jim beam" <spamvortex@bad.example.net> wrote in message
> news:J5ydnZLRCbRMMn_bnZ2dnUVZ_hCdnZ2d@speakeasy.net...
>
>> don't forget, virtually every fatigue failure there's ever been is because
>> of "unanticipated" factors.
>
> Just like "almost every bike uses CF forks"?
go ahead and show me some cfrp that's suffered metal fatigue, mr. modulus.
>
>> just because stress levels aren't /thought/ to be high, *observed
>> failures* tell us that there /is/ bending sufficient to cause fatigue!!!
>
> Then in that case stress levels are INDEED high, that's the only reason to
> cause fatigue, dumbass.
but that's what i said! jeepers!
>
>> see other post on profiles. since residual stress profiles are observed
>> /not/ to be a factor in fatigue, further discussion is pointless - unless
>> applied stresses are discussed also.
>
> Bullshit again. Residual stresses figure prominently in fatigue, especially
> if the stress levels are high.
oh dear. how to explain the difference between analysis of observed
failure vs. the ravings of un unmedicated lunatic that doesn't know what
modulus is...
> Ever hear of shot peening?
yeah, it's used to impart compressive residual stress into poor quality
materials. that's why we use high quality materials.
>
>>> I would have thought so, yes, unless you really overdo it.
>
> Well we all know what your thoughts are worth (clue: it ain't above zilch).
says the guy that doesn't even know basic grade school science experiments!
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Date: 09 Sep 2007 12:07:57
From: Jambo
Subject: Re: Yet another broken spoke
|
"jim beam" <spamvortex@bad.example.net > wrote in message
news:5_ednaBZb55sen_bnZ2dnUVZ_vCknZ2d@speakeasy.net...
> Jambo wrote:
>> "jim beam" <spamvortex@bad.example.net> wrote in message
>> news:J5ydnZLRCbRMMn_bnZ2dnUVZ_hCdnZ2d@speakeasy.net...
>>
>>> don't forget, virtually every fatigue failure there's ever been is
>>> because of "unanticipated" factors.
>>
>> Just like "almost every bike uses CF forks"?
>
> go ahead and show me some cfrp that's suffered metal fatigue, mr. modulus.
Just like "almost every bike uses CF forks"?
>>> just because stress levels aren't /thought/ to be high, *observed
>>> failures* tell us that there /is/ bending sufficient to cause fatigue!!!
>>
>> Then in that case stress levels are INDEED high, that's the only reason
>> to cause fatigue, dumbass.
>
> but that's what i said! jeepers!
Nope, it's not and you can see it up there, turdball!
>>> see other post on profiles. since residual stress profiles are observed
>>> /not/ to be a factor in fatigue, further discussion is pointless -
>>> unless applied stresses are discussed also.
>>
>> Bullshit again. Residual stresses figure prominently in fatigue,
>> especially if the stress levels are high.
>
> oh dear. how to explain the difference between analysis of observed
> failure vs. the ravings of un unmedicated lunatic that doesn't know what
> modulus is...
HAHAHAHAHA! As if you've observed failures at all....
>> Ever hear of shot peening?
>
> yeah, it's used to impart compressive residual stress into poor quality
> materials. that's why we use high quality materials.
Wow, so you are able to read wikipedia. And dumbass, poor of good
materials, residual stresses figure prominently in fatigue, especially if
the stress levels are high!
>>
>>>> I would have thought so, yes, unless you really overdo it.
>>
>> Well we all know what your thoughts are worth (clue: it ain't above
>> zilch).
>
> says the guy that doesn't even know basic grade school science
> experiments!
HAHAHAHA! Since when did you finish high school, moron?
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Date: 08 Sep 2007 11:47:12
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-08, jim beam <spamvortex@bad.example.net > wrote:
> Ben C wrote:
>> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>> [...]
>>> If the spoke has no bending moment (perfectly supported, perfect path),
>>> the applied stress from spoke tension will be tensile (uniform) across
>>> the cross section.
>>
>> I think I basically agree with this, though not absolutely. If the spoke
>> is perfectly supported, but being pulled around a corner, there will
>> surely still be a bending moment on parts of the spoke, but the distance
>> component of that moment will never be greater than half the diameter of
>> the spoke.
>>
>> Moments that small (assuming the force is in the range of normal spoke
>> tensions) are low enough not to worry about-- they're not bringing
>> anything anywhere near dangerously high stress levels for fatigue.
>
> don't forget, virtually every fatigue failure there's ever been is
> because of "unanticipated" factors. just because stress levels aren't
> /thought/ to be high, *observed failures* tell us that there /is/
> bending sufficient to cause fatigue!!!
Yes, although doesn't it depend what you mean by "cause"? There is
always some bending unless you have a straight pull spoke. If the mean
stress in that bending cycle is low then you should get a long life
unless you've got very bad surface defects.
On the other hand if the mean stress is high (e.g. because you have a
big bending moment), but the surface is much better, you might also get
a short life.
It's quite believable to me that wear resulting in corrosion that
nucleated fatigue was a big factor in Clare's failed galvanized spokes,
even if the stress cycle on them wasn't too big. But if someone's nice
new stainless DT spokes in an Al hub fail after a few 100km then
retained stress from the build or a big moment at the elbow look more to
blame.
In both cases there's bending and in both cases presumably the fatigue
starts somewhere. So the same basic mechanism, but it's reasonable to
blame or suspect the surface quality in the first case and the high
stresses in the second.
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Date: 08 Sep 2007 20:31:24
From:
Subject: Re: Yet another broken spoke
|
Ben C? writes:
>>>> If the spoke has no bending moment (perfectly supported, perfect
>>>> path), the applied stress from spoke tension will be tensile
>>>> (uniform) across the cross section.
>>> I think I basically agree with this, though not absolutely. If the
>>> spoke is perfectly supported, but being pulled around a corner,
>>> there will surely still be a bending moment on parts of the spoke,
>>> but the distance component of that moment will never be greater
>>> than half the diameter of the spoke.
>>> Moments that small (assuming the force is in the range of normal
>>> spoke tensions) are low enough not to worry about-- they're not
>>> bringing anything anywhere near dangerously high stress levels for
>>> fatigue.
>> don't forget, virtually every fatigue failure there's ever been is
>> because of "unanticipated" factors. just because stress levels
>> aren't /thought/ to be high, *observed failures* tell us that there
>> /is/ bending sufficient to cause fatigue!!!
> Yes, although doesn't it depend what you mean by "cause"? There is
> always some bending unless you have a straight pull spoke. If the
> mean stress in that bending cycle is low then you should get a long
> life unless you've got very bad surface defects.
> On the other hand if the mean stress is high (e.g. because you have
> a big bending moment), but the surface is much better, you might
> also get a short life.
> It's quite believable to me that wear resulting in corrosion that
> nucleated fatigue was a big factor in Clare's failed galvanized
> spokes, even if the stress cycle on them wasn't too big. But if
> someone's nice new stainless DT spokes in an Al hub fail after a few
> 100km then retained stress from the build or a big moment at the
> elbow look more to blame.
> In both cases there's bending and in both cases presumably the
> fatigue starts somewhere. So the same basic mechanism, but it's
> reasonable to blame or suspect the surface quality in the first case
> and the high stresses in the second.
You may recall that this thread started with someone who had a fairly
new wheel with stainless spokes (of unknown brand) that got early
spoke failures. The suggestion was that loose spokes cause failure
and that this causes higher stress. Since then, the focus has drifted
through argumentative dodges to what stresses cause failure and the
nature of stress in spoke elbows.
How low tension causes spoke failure and whether the wheel in question
was loosely spoked is still unclear, as is the brand of spokes. Just
the same, the drifting subject allowed some spoke lore to re-emerge,
such as if more than one spoke breaks, replace all of them, and this
matter of low spoke tension causing failure. The cause of either of
these has not been reasonably explained. The galvanized spokes were
not shown so the substantial wear that causes failure was visible.
As often, this thread buried logical discourse in insults and chaff.
Jobst Brandt
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Date: 08 Sep 2007 17:30:27
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-08, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org > wrote:
> Ben C? writes:
[...]
>> It's quite believable to me that wear resulting in corrosion that
>> nucleated fatigue was a big factor in Clare's failed galvanized
>> spokes, even if the stress cycle on them wasn't too big. But if
>> someone's nice new stainless DT spokes in an Al hub fail after a few
>> 100km then retained stress from the build or a big moment at the
>> elbow look more to blame.
>
>> In both cases there's bending and in both cases presumably the
>> fatigue starts somewhere. So the same basic mechanism, but it's
>> reasonable to blame or suspect the surface quality in the first case
>> and the high stresses in the second.
>
> You may recall that this thread started with someone who had a fairly
> new wheel with stainless spokes (of unknown brand) that got early
> spoke failures. The suggestion was that loose spokes cause failure
> and that this causes higher stress.
>
> Since then, the focus has drifted through argumentative dodges to what
> stresses cause failure and the nature of stress in spoke elbows.
We can never flog that one enough.
> How low tension causes spoke failure and whether the wheel in question
> was loosely spoked is still unclear, as is the brand of spokes. Just
> the same, the drifting subject allowed some spoke lore to re-emerge,
> such as if more than one spoke breaks, replace all of them,
Is that bad lore? If a few spokes break because of lack of stress relief
(which according to you I think is the most likely reason) then isn't it
reasonable to suspect the wheel wasn't stress-relieved properly and so
other spokes will soon fail too?
> and this matter of low spoke tension causing failure. The cause of
> either of these has not been reasonably explained. The galvanized
> spokes were not shown so the substantial wear that causes failure was
> visible.
Two reasons were given why loose spokes might lead to failure: wear and
bending.
And yes, fair point, we haven't actually seen the worn galvanized spokes
but Clare provided a convincing description of them. I think Gene may
have reported similar problems in the past and has also described
movement in the spoke holes of loose spokes leading to wear.
The bending theory remains a theory.
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Date: 09 Sep 2007 00:15:27
From:
Subject: Re: Yet another broken spoke
|
Ben C? writes:
>>> It's quite believable to me that wear resulting in corrosion that
>>> nucleated fatigue was a big factor in Clare's failed galvanized
>>> spokes, even if the stress cycle on them wasn't too big. But if
>>> someone's nice new stainless DT spokes in an Al hub fail after a
>>> few 100km then retained stress from the build or a big moment at
>>> the elbow look more to blame.
>>> In both cases there's bending and in both cases presumably the
>>> fatigue starts somewhere. So the same basic mechanism, but it's
>>> reasonable to blame or suspect the surface quality in the first
>>> case and the high stresses in the second.
>> You may recall that this thread started with someone who had a
>> fairly new wheel with stainless spokes (of unknown brand) that got
>> early spoke failures. The suggestion was that loose spokes cause
>> failure and that this causes higher stress.
>> Since then, the focus has drifted through argumentative dodges to
>> what stresses cause failure and the nature of stress in spoke
>> elbows.
> We can never flog that one enough.
>> How low tension causes spoke failure and whether the wheel in
>> question was loosely spoked is still unclear, as is the brand of
>> spokes. Just the same, the drifting subject allowed some spoke
>> lore to re-emerge, such as if more than one spoke breaks, replace
>> all of them,
> Is that bad lore? If a few spokes break because of lack of stress
> relief (which according to you I think is the most likely reason)
> then isn't it reasonable to suspect the wheel wasn't stress-relieved
> properly and so other spokes will soon fail too?
From my experience it is without merit. I stumbled onto stress relief
when after a crash on a tour, I had to switch to a set of wheels that
broke spokes often, having large flange 36-spoke Campagnolo record
hubs. They promptly broke two spokes and having spare spokes in my
touring bag, I disassembled the Regina freewheel at a gas station that
lent me a hammer and punch to remove the outer cone to give access
to the spokes. (lots of loose bearing balls and two ratchet pawls)
After replacing the broken spokes and fearing that others would soon
fail, I "stress relieved" the wheels, breaking two more spokes that I
then replaced before repeating the spoke breaking exercise. It
occurred to me weeks later that no more spokes had broken and that the
wheels were performing reliably.
It was this experience that got me to thinking about stress relief and
to perform this operation on all wheels that I built. After that,
spoke failures were rare even though we were using Robergel and Stella
brand spokes, both having a poor finish and known to fail readily.
I did not replace all the spokes and got good service from the wheels.
>> and this matter of low spoke tension causing failure. The cause of
>> either of these has not been reasonably explained. The galvanized
>> spokes were not shown so the substantial wear that causes failure
>> was visible.
> Two reasons were given why loose spokes might lead to failure: wear
> and bending.
From the evidence reported, I do not understand the bending theory of
loose spokes. Bending under essentially no load is like holding a
spoke by one end and waving it back and forth manually.
> And yes, fair point, we haven't actually seen the worn galvanized
> spokes but Clare provided a convincing description of them. I think
> Gene may have reported similar problems in the past and has also
> described movement in the spoke holes of loose spokes leading to
> wear.
I don't believe that they were worn half way through or even more than
polishing the plating.
> The bending theory remains a theory.
Jobst Brandt
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Date: 09 Sep 2007 02:55:50
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-09, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org > wrote:
> Ben C? writes:
[...]
> After replacing the broken spokes and fearing that others would soon
> fail, I "stress relieved" the wheels, breaking two more spokes that I
> then replaced before repeating the spoke breaking exercise. It
> occurred to me weeks later that no more spokes had broken and that the
> wheels were performing reliably.
If a spoke isn't stress relieved, and run at a high mean stress stress
cycle for some time, and then stress-relieved just in the nick of time
before it actually breaks, what is its life time from that point
expected to be? In theory?
Not rhetorical question.
[...]
>> Two reasons were given why loose spokes might lead to failure: wear
>> and bending.
>
> From the evidence reported, I do not understand the bending theory of
> loose spokes. Bending under essentially no load is like holding a
> spoke by one end and waving it back and forth manually.
The rim is pushing the spoke towards the hub. First it (a) wobbles a
bit, and then, (b) not being a stiff rod, it may flex one way or
another. (c) It's supported at the elbow so it might bend there.
jim beam has also suggested the spoke crossings may be involved although
I'm less clear on the details so won't try to explain that.
(b) may not happen depending on the magnitude of (a)-- I believe that's
what you said. So I don't know if (b) or (c) happens.
That's all there is to it. That's all the reasoning I know of. There's
no evidence.
>> And yes, fair point, we haven't actually seen the worn galvanized
>> spokes but Clare provided a convincing description of them. I think
>> Gene may have reported similar problems in the past and has also
>> described movement in the spoke holes of loose spokes leading to
>> wear.
>
> I don't believe that they were worn half way through or even more than
> polishing the plating.
Isn't a galvanized spoke coated with a kind of zinc stuff to stop it
rusting? If that wears away the steel underneath starts to rust a
bit. A small rust spot is enough to nucleate fatigue. So the spoke
doesn't wear all the way through, or rust all the way through, but a bit
of wear is enough to make it fatigue quickly.
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Date: 10 Sep 2007 02:53:17
From:
Subject: Re: Yet another broken spoke
|
Ben C? writes:
>> After replacing the broken spokes and fearing that others would
>> soon fail, I "stress relieved" the wheels, breaking two more spokes
>> that I then replaced before repeating the spoke breaking exercise.
>> It occurred to me weeks later that no more spokes had broken and
>> that the wheels were performing reliably.
> If a spoke isn't stress relieved, and run at a high mean stress
> stress cycle for some time, and then stress-relieved just in the
> nick of time before it actually breaks, what is its life time from
> that point expected to be? In theory?
Your assumption is that other spokes in the wheel all have high stress
somewhere and that they are all progressing to failure uniformly.
This is especially untrue for wheels that have relatively early
failures. My experience is that even with onset of fatigue cracking,
stress relieving and replacement of failed spokes is worth the effort.
>>> Two reasons were given why loose spokes might lead to failure:
>>> wear and bending.
>> From the evidence reported, I do not understand the bending theory
>> of loose spokes. Bending under essentially no load is like holding
>> a spoke by one end and waving it back and forth manually.
> The rim is pushing the spoke toward the hub. First it (a) wobbles
> a bit, and then, (b) not being a stiff rod, it may flex one way or
> another. (c) It's supported at the elbow so it might bend there.
> jim beam has also suggested the spoke crossings may be involved
> although I'm less clear on the details so won't try to explain that.
Having not seen a spoke fail at a spoke crossing, this does not ring
true. If you believe the spoke crossings bend spokes at the elbows,
this runs into a counter claim by that author that flexing is not
affected by spoke preload.
> (b) may not happen depending on the magnitude of (a)-- I believe
> that's what you said. So I don't know if (b) or (c) happens.
> That's all there is to it. That's all the reasoning I know of.
> There's no evidence.
In that event, I see no reason to give that credibility in light of my
experience with riders who had loose spokes in the rear wheel to the
extent that they rattled when standing, without failure and that when
subsequently re-trued and tightened served well... in the days of poor
quality spokes.
>>> And yes, fair point, we haven't actually seen the worn galvanized
>>> spokes but Clare provided a convincing description of them. I
>>> think Gene may have reported similar problems in the past and has
>>> also described movement in the spoke holes of loose spokes leading
>>> to wear.
>> I don't believe that they were worn half way through or even more
>> than polishing the plating.
> Isn't a galvanized spoke coated with a kind of zinc stuff to stop it
> rusting? If that wears away the steel underneath starts to rust a
> bit. A small rust spot is enough to nucleate fatigue. So the spoke
> doesn't wear all the way through, or rust all the way through, but a
> bit of wear is enough to make it fatigue quickly.
Usually zinc plating (spokes are not galvanized in molten zinc as
sheet metal often is) zinc usually has a matte finish and becomes
polished under contact loads with an aluminum flange. Steel hubs
present different problems, but I don't believe we are discussing
steel hubs in this thread.
Jobst Brandt
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Date: 10 Sep 2007 02:22:22
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-10, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org > wrote:
> Ben C? writes:
[...]
>>> From the evidence reported, I do not understand the bending theory
>>> of loose spokes. Bending under essentially no load is like holding
>>> a spoke by one end and waving it back and forth manually.
>
>> The rim is pushing the spoke toward the hub. First it (a) wobbles
>> a bit, and then, (b) not being a stiff rod, it may flex one way or
>> another. (c) It's supported at the elbow so it might bend there.
>
>> jim beam has also suggested the spoke crossings may be involved
>> although I'm less clear on the details so won't try to explain that.
>
> Having not seen a spoke fail at a spoke crossing, this does not ring
> true. If you believe the spoke crossings bend spokes at the elbows,
> this runs into a counter claim by that author that flexing is not
> affected by spoke preload.
I don't think the suggestion is that they fail at the crossings, but
that the way the crossings move allow them to flex at the elbows.
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Date: 09 Sep 2007 22:16:29
From: jim beam
Subject: Re: Yet another broken spoke
|
jobst.brandt@stanfordalumni.org wrote:
> Ben C? writes:
>
>>> After replacing the broken spokes and fearing that others would
>>> soon fail, I "stress relieved" the wheels, breaking two more spokes
>>> that I then replaced before repeating the spoke breaking exercise.
>>> It occurred to me weeks later that no more spokes had broken and
>>> that the wheels were performing reliably.
>
>> If a spoke isn't stress relieved, and run at a high mean stress
>> stress cycle for some time, and then stress-relieved just in the
>> nick of time before it actually breaks, what is its life time from
>> that point expected to be? In theory?
>
> Your assumption is that other spokes in the wheel all have high stress
> somewhere and that they are all progressing to failure uniformly.
> This is especially untrue for wheels that have relatively early
> failures. My experience is that even with onset of fatigue cracking,
> stress relieving and replacement of failed spokes is worth the effort.
quantifiably, right? you have numbers?
>
>>>> Two reasons were given why loose spokes might lead to failure:
>>>> wear and bending.
>
>>> From the evidence reported, I do not understand the bending theory
>>> of loose spokes. Bending under essentially no load is like holding
>>> a spoke by one end and waving it back and forth manually.
>
>> The rim is pushing the spoke toward the hub. First it (a) wobbles
>> a bit, and then, (b) not being a stiff rod, it may flex one way or
>> another. (c) It's supported at the elbow so it might bend there.
>
>> jim beam has also suggested the spoke crossings may be involved
>> although I'm less clear on the details so won't try to explain that.
>
> Having not seen a spoke fail at a spoke crossing, this does not ring
> true. If you believe the spoke crossings bend spokes at the elbows,
> this runs into a counter claim by that author that flexing is not
> affected by spoke preload.
that's not what i'm saying at all. what i /am/ saying is that if a
spoke is interleaved, if it goes slack, the tension from its partner
will cause considerably more bending excursion than if it had not been
interleaved.
>
>> (b) may not happen depending on the magnitude of (a)-- I believe
>> that's what you said. So I don't know if (b) or (c) happens.
>
>> That's all there is to it. That's all the reasoning I know of.
>> There's no evidence.
>
> In that event, I see no reason to give that credibility in light of my
> experience with riders who had loose spokes in the rear wheel to the
> extent that they rattled when standing, without failure and that when
> subsequently re-trued and tightened served well... in the days of poor
> quality spokes.
number please...
>
>>>> And yes, fair point, we haven't actually seen the worn galvanized
>>>> spokes but Clare provided a convincing description of them. I
>>>> think Gene may have reported similar problems in the past and has
>>>> also described movement in the spoke holes of loose spokes leading
>>>> to wear.
>
>>> I don't believe that they were worn half way through or even more
>>> than polishing the plating.
>
>> Isn't a galvanized spoke coated with a kind of zinc stuff to stop it
>> rusting? If that wears away the steel underneath starts to rust a
>> bit. A small rust spot is enough to nucleate fatigue. So the spoke
>> doesn't wear all the way through, or rust all the way through, but a
>> bit of wear is enough to make it fatigue quickly.
>
> Usually zinc plating (spokes are not galvanized in molten zinc as
> sheet metal often is)
the process is called "sherardizing"
> zinc usually has a matte finish and becomes
> polished under contact loads with an aluminum flange.
which implies relative movement. which you say is impossible if the
spoke is supported by the flange!
oh, and zinc protects steel by preferential corrosion. that means it
more aggressively corrodes relative to its substrate - it doesn't stay
polished. hence the surface will become rougher, and more fatigue
prone. less so than plain steel obviously, but more so than stainless.
> Steel hubs
> present different problems, but I don't believe we are discussing
> steel hubs in this thread.
red herring.
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Date: 10 Sep 2007 20:59:09
From: Jambo
Subject: Re: Yet another broken spoke
|
"jim beam" <spamvortex@bad.example.net > wrote in message
news:KridnYKBkoSzTnnbnZ2dnUVZ_vmlnZ2d@speakeasy.net...
> quantifiably, right? you have numbers?
Why, you able to do basic arithmetic?
> that's not what i'm saying at all. what i /am/ saying is that if a spoke
> is interleaved, if it goes slack, the tension from its partner will cause
> considerably more bending excursion than if it had not been interleaved.
Shift the goalposts, quick, before anyone notices... oops, too late....
>> In that event, I see no reason to give that credibility in light of my
>> experience with riders who had loose spokes in the rear wheel to the
>> extent that they rattled when standing, without failure and that when
>> subsequently re-trued and tightened served well... in the days of poor
>> quality spokes.
>
> number please...
What are you going to do with it though?
>
> the process is called "sherardizing"
Wow, so if I define "inclusion", I too can make up stories from my youth,
bleat bullshit and pretend to be a "former metallurgist"?
Wow.
> oh, and zinc protects steel by preferential corrosion. that means it more
> aggressively corrodes relative to its substrate - it doesn't stay
> polished. hence the surface will become rougher, and more fatigue prone.
> less so than plain steel obviously, but more so than stainless.
Stays polished if it keeps getting polished, moron! Man, this sometimes
gets tiresome.
>> Steel hubs
>> present different problems, but I don't believe we are discussing
>> steel hubs in this thread.
>
> red herring.
Red cock.
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Date: 10 Sep 2007 10:22:11
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> quantifiably, right? you have numbers?
> that's not what i'm saying at all. what i /am/ saying is that if a
> spoke is interleaved, if it goes slack, the tension from its partner
> will cause considerably more bending excursion than if it had not been
> interleaved.
You have numbers?
My numbers say that 2mm spokes crossed 2cm from the ends will produce a
maximum skin stress from bending of about 30MPa. Of course the slack
spoke won't bend that much during the wheel cycle, in fact it will bend
hardly at all, since, because it is slack, there is no longer much if
any force at the crossing.
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Date: 10 Sep 2007 22:31:36
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>
>> quantifiably, right? you have numbers?
>
>> that's not what i'm saying at all. what i /am/ saying is that if a
>> spoke is interleaved, if it goes slack, the tension from its partner
>> will cause considerably more bending excursion than if it had not been
>> interleaved.
>
> You have numbers?
>
> My numbers say that 2mm spokes crossed 2cm from the ends will produce a
> maximum skin stress from bending of about 30MPa. Of course the slack
> spoke won't bend that much during the wheel cycle, in fact it will bend
> hardly at all, since, because it is slack, there is no longer much if
> any force at the crossing.
again, i'm /NOT/ talking about the bend at the crossing - spokes don't
break there. i'm talking about the effect the interleaving has on the
/elbow/. it causes considerable deviation from the straight line, and
this /has/ to be accommodated by an increased bending moment at the elbow.
http://www.flickr.com/photos/38636024@N00/1313347532/
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Date: 11 Sep 2007 06:41:40
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>
>>> quantifiably, right? you have numbers?
>>
>>> that's not what i'm saying at all. what i /am/ saying is that if a
>>> spoke is interleaved, if it goes slack, the tension from its partner
>>> will cause considerably more bending excursion than if it had not
>>> been interleaved.
>>
>> You have numbers?
>>
>> My numbers say that 2mm spokes crossed 2cm from the ends will produce
>> a maximum skin stress from bending of about 30MPa. Of course the slack
>> spoke won't bend that much during the wheel cycle, in fact it will
>> bend hardly at all, since, because it is slack, there is no longer
>> much if any force at the crossing.
>
> again, i'm /NOT/ talking about the bend at the crossing - spokes don't
> break there. i'm talking about the effect the interleaving has on the
> /elbow/. it causes considerable deviation from the straight line, and
> this /has/ to be accommodated by an increased bending moment at the elbow.
>
> http://www.flickr.com/photos/38636024@N00/1313347532/
You misunderstand. I *am* describing the change on skin stress *at the
elbow* caused by the deflection of a spoke at the crossing. Worst case
(both spokes fully tensioned), it's small; in your scenario, it's much
smaller yet -- in other words, miniscule -- it can't possibly contribute
to fatigue.
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Date: 09 Sep 2007 12:46:14
From:
Subject: Re: Yet another broken spoke
|
On Sun, 09 Sep 2007 02:55:50 -0500, Ben C <spamspam@spam.eggs > wrote:
[snip]
>If a spoke isn't stress relieved, and run at a high mean stress stress
>cycle for some time, and then stress-relieved just in the nick of time
>before it actually breaks, what is its life time from that point
>expected to be? In theory?
>
>Not rhetorical question.
[snip]
Dear Ben,
Unfortunately, only theoretical answers are available.
The enormous fuss in these threads is due to the fact that we know of
no spoke fatigue tests except for the one done in 1985 for Wheelsmith
at Stanford, which did not address the various theories frequently
offered here.
Everything else is based on anecdotes.
For the curious:
"In 1984 and 1985, fatigue tests on stainless steel bicycle spokes
were carried out for Wheelsmith, Inc. at Stanford University. Constant
cycle tests were conducted with pre-tensioning stresses of 174 MPa,
250 MPa, 343 MPa, 347 MPa, 424 MPa, and 501 MPa. Any correlation
between the cycles to failure, N, and the pre-tensioning stress was
obscured by random variations in N. The parameters a and b were
determined from a least squares fit of fatigue data from 76 stainless
steel bicycle spokes, shown in Figure 13 (using N as the dependent
variable (Rice 1985)). Variations in the (dependent) variable N due to
stress cycles of a constant amplitude, S, are modeled by the normally
distributed random variable b, with average b, and coefficient of
variation Vb. For the data shown in Figure 13, a=-0.30
log(MPa)/log(cycle), b =4.12 log(MPa), Vb=0.017. Using this
data, the coefficient of variation of N is 0.74, for any constant
value of S. This data is unique to the spoke material, the spoke
geometry, and the spoke’s particular stress concentrations. In 68
spokes the failure occurred at the cold-worked elbow; in the remaining
8 spokes the failure occurred at the threads."
"The smallest stress cycle in the fatigue tests was 174 MPa, whereas
the stress range from the road test data was 20 MPa to 150 MPa. Hence,
the fatigue data was extrapolated to the low stress range. (To have
tested a single sample at 40 MPa would have required over a year of
continuous testing at 10 cycles per second, and an unwarranted use of
facilities.)"
http://www.duke.edu/~hpgavin/papers/HPGavin-Wheel-Paper.pdf
Cheers,
Carl Fogel
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Date: 08 Sep 2007 10:34:40
From: jim beam
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-08, jim beam <spamvortex@bad.example.net> wrote:
>> Ben C wrote:
>>> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>>> [...]
>>>> If the spoke has no bending moment (perfectly supported, perfect path),
>>>> the applied stress from spoke tension will be tensile (uniform) across
>>>> the cross section.
>>> I think I basically agree with this, though not absolutely. If the spoke
>>> is perfectly supported, but being pulled around a corner, there will
>>> surely still be a bending moment on parts of the spoke, but the distance
>>> component of that moment will never be greater than half the diameter of
>>> the spoke.
>>>
>>> Moments that small (assuming the force is in the range of normal spoke
>>> tensions) are low enough not to worry about-- they're not bringing
>>> anything anywhere near dangerously high stress levels for fatigue.
>> don't forget, virtually every fatigue failure there's ever been is
>> because of "unanticipated" factors. just because stress levels aren't
>> /thought/ to be high, *observed failures* tell us that there /is/
>> bending sufficient to cause fatigue!!!
>
> Yes, although doesn't it depend what you mean by "cause"? There is
> always some bending unless you have a straight pull spoke. If the mean
> stress in that bending cycle is low then you should get a long life
> unless you've got very bad surface defects.
>
> On the other hand if the mean stress is high (e.g. because you have a
> big bending moment), but the surface is much better, you might also get
> a short life.
>
> It's quite believable to me that wear resulting in corrosion that
> nucleated fatigue was a big factor in Clare's failed galvanized spokes,
> even if the stress cycle on them wasn't too big. But if someone's nice
> new stainless DT spokes in an Al hub fail after a few 100km then
> retained stress from the build or a big moment at the elbow look more to
> blame.
but this is not a matter of faith.
1. all traditional spokes of all qualities, of all materials, regardless
of manufacturer, are all have the elbow bent in a way that has the same
metallurgical result regarding residual stress. yet they all have
dramatically different fatigue lives that correspond with the other
variables such as material, surface finish, etc.
2. stress necessary to provide mechanical stress relief is achieved
simply from wheel pre-tension. carl fogel illustrated this well some
time ago.
3. regardless of 1. & 2., fatigue initiation is always from a region of
low/zero residual stress but high load stress.
>
> In both cases there's bending and in both cases presumably the fatigue
> starts somewhere. So the same basic mechanism, but it's reasonable to
> blame or suspect the surface quality in the first case and the high
> stresses in the second.
yes there's bending, yes there's stress, and residual stress doesn't
explain observed failures.
http://www.flickr.com/photos/38636024@N00/1346747861/
i regret that my magnification equipment doesn't allow me to take actual
pics.
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Date: 08 Sep 2007 13:11:27
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-08, jim beam <spamvortex@bad.example.net > wrote:
> Ben C wrote:
>> On 2007-09-08, jim beam <spamvortex@bad.example.net> wrote:
>>> Ben C wrote:
>>>> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>>>> [...]
>>>>> If the spoke has no bending moment (perfectly supported, perfect path),
>>>>> the applied stress from spoke tension will be tensile (uniform) across
>>>>> the cross section.
>>>> I think I basically agree with this, though not absolutely. If the spoke
>>>> is perfectly supported, but being pulled around a corner, there will
>>>> surely still be a bending moment on parts of the spoke, but the distance
>>>> component of that moment will never be greater than half the diameter of
>>>> the spoke.
>>>>
>>>> Moments that small (assuming the force is in the range of normal spoke
>>>> tensions) are low enough not to worry about-- they're not bringing
>>>> anything anywhere near dangerously high stress levels for fatigue.
>>> don't forget, virtually every fatigue failure there's ever been is
>>> because of "unanticipated" factors. just because stress levels aren't
>>> /thought/ to be high, *observed failures* tell us that there /is/
>>> bending sufficient to cause fatigue!!!
>>
>> Yes, although doesn't it depend what you mean by "cause"? There is
>> always some bending unless you have a straight pull spoke. If the mean
>> stress in that bending cycle is low then you should get a long life
>> unless you've got very bad surface defects.
>>
>> On the other hand if the mean stress is high (e.g. because you have a
>> big bending moment), but the surface is much better, you might also get
>> a short life.
>>
>> It's quite believable to me that wear resulting in corrosion that
>> nucleated fatigue was a big factor in Clare's failed galvanized spokes,
>> even if the stress cycle on them wasn't too big. But if someone's nice
>> new stainless DT spokes in an Al hub fail after a few 100km then
>> retained stress from the build or a big moment at the elbow look more to
>> blame.
>
> but this is not a matter of faith.
>
> 1. all traditional spokes of all qualities, of all materials, regardless
> of manufacturer, are all have the elbow bent in a way that has the same
> metallurgical result regarding residual stress. yet they all have
> dramatically different fatigue lives that correspond with the other
> variables such as material, surface finish, etc.
Good point. I was careful though to say "retained stress from the
build", not "residual stress" [from manufacture].
The latter I have mostly put in the red herring bucket so far but keep
an open mind as I am not an expert on these things.
Retained stress from the build, which really I would lump together with
poor spoke line (i.e. bending moment at the elbow) is what I suspect may
be a significant factor in some failures where good quality spokes are
used.
If there is high stress in the elbow after the build it follows that
there's enough moment present for spoke tension to maintain that stress.
I'd be inclined to say that the moment is the real problem: it will
allow a high-stress bending cycle in use, even if you stress-relieve, if
stress relief doesn't also have the effect of also reducing that moment.
But I think stress-relief probably _does_ reduce the moment by bending
the elbow a bit more and by conforming it to the hub (_pace_ Peter
Cole's and Jobst's well-reasoned arguments why hub conformance is not
likely to happen much after tensioning).
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Date: 09 Sep 2007 07:06:11
From: jim beam
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-08, jim beam <spamvortex@bad.example.net> wrote:
>> Ben C wrote:
>>> On 2007-09-08, jim beam <spamvortex@bad.example.net> wrote:
>>>> Ben C wrote:
>>>>> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>>>>> [...]
>>>>>> If the spoke has no bending moment (perfectly supported, perfect path),
>>>>>> the applied stress from spoke tension will be tensile (uniform) across
>>>>>> the cross section.
>>>>> I think I basically agree with this, though not absolutely. If the spoke
>>>>> is perfectly supported, but being pulled around a corner, there will
>>>>> surely still be a bending moment on parts of the spoke, but the distance
>>>>> component of that moment will never be greater than half the diameter of
>>>>> the spoke.
>>>>>
>>>>> Moments that small (assuming the force is in the range of normal spoke
>>>>> tensions) are low enough not to worry about-- they're not bringing
>>>>> anything anywhere near dangerously high stress levels for fatigue.
>>>> don't forget, virtually every fatigue failure there's ever been is
>>>> because of "unanticipated" factors. just because stress levels aren't
>>>> /thought/ to be high, *observed failures* tell us that there /is/
>>>> bending sufficient to cause fatigue!!!
>>> Yes, although doesn't it depend what you mean by "cause"? There is
>>> always some bending unless you have a straight pull spoke. If the mean
>>> stress in that bending cycle is low then you should get a long life
>>> unless you've got very bad surface defects.
>>>
>>> On the other hand if the mean stress is high (e.g. because you have a
>>> big bending moment), but the surface is much better, you might also get
>>> a short life.
>>>
>>> It's quite believable to me that wear resulting in corrosion that
>>> nucleated fatigue was a big factor in Clare's failed galvanized spokes,
>>> even if the stress cycle on them wasn't too big. But if someone's nice
>>> new stainless DT spokes in an Al hub fail after a few 100km then
>>> retained stress from the build or a big moment at the elbow look more to
>>> blame.
>> but this is not a matter of faith.
>>
>> 1. all traditional spokes of all qualities, of all materials, regardless
>> of manufacturer, are all have the elbow bent in a way that has the same
>> metallurgical result regarding residual stress. yet they all have
>> dramatically different fatigue lives that correspond with the other
>> variables such as material, surface finish, etc.
>
> Good point. I was careful though to say "retained stress from the
> build", not "residual stress" [from manufacture].
>
> The latter I have mostly put in the red herring bucket so far but keep
> an open mind as I am not an expert on these things.
>
> Retained stress from the build, which really I would lump together with
> poor spoke line (i.e. bending moment at the elbow) is what I suspect may
> be a significant factor in some failures where good quality spokes are
> used.
>
> If there is high stress in the elbow after the build it follows that
> there's enough moment present for spoke tension to maintain that stress.
> I'd be inclined to say that the moment is the real problem: it will
> allow a high-stress bending cycle in use, even if you stress-relieve, if
> stress relief doesn't also have the effect of also reducing that moment.
>
> But I think stress-relief probably _does_ reduce the moment by bending
> the elbow a bit more and by conforming it to the hub (_pace_ Peter
> Cole's and Jobst's well-reasoned arguments why hub conformance is not
> likely to happen much after tensioning).\
right, and that's distinct from "stress relief" in the metallurgical sense.
and yes, you /do/ get additional conformance beyond initial tensioning
by using overload - only if you don't understand point force deformation
you think otherwise.
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Date: 08 Sep 2007 20:53:58
From:
Subject: Re: Yet another broken spoke
|
Ben C? writes:
> Good point. I was careful though to say "retained stress from the
> build", not "residual stress" [from manufacture].
> The latter I have mostly put in the red herring bucket so far but
> keep an open mind as I am not an expert on these things.
I think you should review that opinion and how you came to that
conclusion. A permanent bend in a wire causes residual stress and the
one in a spoke is increased in as many as half the spokes when
building a wheel, as the elbow angle becomes acute from on obtuse
angle.
> Retained stress from the build, which really I would lump together
> with poor spoke line (i.e. bending moment at the elbow) is what I
> suspect may be a significant factor in some failures where good
> quality spokes are used.
That cannot be readily improved by stress relief, there bing
insufficient overload manually to improve the spoke line.
> If there is high stress in the elbow after the build it follows that
> there's enough moment present for spoke tension to maintain that
> stress. I'd be inclined to say that the moment is the real problem:
> it will allow a high-stress bending cycle in use, even if you
> stress-relieve, if stress relief doesn't also have the effect of
> also reducing that moment.
That's why you improve the spoke line and then stress relieve, so that
peak stress is far enough below yield, that fatigue failures do not
occur for a long time if ever. As I said, I have wheels that went
300,000 miles with spoke failures at chain gouges (not in the elbow)
of a few outbound spokes.
> But I think stress-relief probably _does_ reduce the moment by
> bending the elbow a bit more and by conforming it to the hub (_pace_
> Peter Cole's and Jobst's well-reasoned arguments why hub conformance
> is not likely to happen much after tensioning).
Forget about the moment, just tensile changes from load bearing are
enough to cause fatigue failure if the spoke is near yield, which it
is, because the elbow angle was yielded to an acute angle in spoke
lacing, and held there by subsequent tensioning.
Jobst Brandt
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Date: 08 Sep 2007 17:56:36
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-08, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org > wrote:
> Ben C? writes:
>
>> Good point. I was careful though to say "retained stress from the
>> build", not "residual stress" [from manufacture].
>
>> The latter I have mostly put in the red herring bucket so far but
>> keep an open mind as I am not an expert on these things.
>
> I think you should review that opinion and how you came to that
> conclusion. A permanent bend in a wire causes residual stress and the
> one in a spoke is increased in as many as half the spokes when
> building a wheel, as the elbow angle becomes acute from on obtuse
> angle.
Isn't it the other way round? The residual stresses are compressive on
the exterior on outside of the bend (I thought) and tensile on the
exterior of the inside. So it's the elbows that become more obtuse for
which the building-bend adds to the manufacturing residual stress?
>> Retained stress from the build, which really I would lump together
>> with poor spoke line (i.e. bending moment at the elbow) is what I
>> suspect may be a significant factor in some failures where good
>> quality spokes are used.
>
> That cannot be readily improved by stress relief, there bing
> insufficient overload manually to improve the spoke line.
>
>> If there is high stress in the elbow after the build it follows that
>> there's enough moment present for spoke tension to maintain that
>> stress. I'd be inclined to say that the moment is the real problem:
>> it will allow a high-stress bending cycle in use, even if you
>> stress-relieve, if stress relief doesn't also have the effect of
>> also reducing that moment.
>
> That's why you improve the spoke line and then stress relieve, so that
> peak stress is far enough below yield, that fatigue failures do not
> occur for a long time if ever. As I said, I have wheels that went
> 300,000 miles with spoke failures at chain gouges (not in the elbow)
> of a few outbound spokes.
300K miles without the brake track wearing out? That is outstanding.
I don't think I've had anything last as long as 300K miles in my whole
life.
>> But I think stress-relief probably _does_ reduce the moment by
>> bending the elbow a bit more and by conforming it to the hub (_pace_
>> Peter Cole's and Jobst's well-reasoned arguments why hub conformance
>> is not likely to happen much after tensioning).
>
> Forget about the moment, just tensile changes from load bearing are
> enough to cause fatigue failure if the spoke is near yield, which it
> is, because the elbow angle was yielded to an acute angle in spoke
> lacing, and held there by subsequent tensioning.
Yes, but as I said before, if the spoke is near yield under normal spoke
tension _there must be a moment_. I don't see how you can have one
without the other.
That's why I think the moment is key: it's where big stresses at the
elbow, on the exterior, come from.
I'm not denying that residual stresses from manufacture will add to
those stresses in places.
|
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Date: 09 Sep 2007 07:04:18
From: jim beam
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-08, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org> wrote:
>> Ben C? writes:
>>
>>> Good point. I was careful though to say "retained stress from the
>>> build", not "residual stress" [from manufacture].
>>> The latter I have mostly put in the red herring bucket so far but
>>> keep an open mind as I am not an expert on these things.
>> I think you should review that opinion and how you came to that
>> conclusion. A permanent bend in a wire causes residual stress and the
>> one in a spoke is increased in as many as half the spokes when
>> building a wheel, as the elbow angle becomes acute from on obtuse
>> angle.
>
> Isn't it the other way round? The residual stresses are compressive on
> the exterior on outside of the bend (I thought) and tensile on the
> exterior of the inside. So it's the elbows that become more obtuse for
> which the building-bend adds to the manufacturing residual stress?
>
>>> Retained stress from the build, which really I would lump together
>>> with poor spoke line (i.e. bending moment at the elbow) is what I
>>> suspect may be a significant factor in some failures where good
>>> quality spokes are used.
>> That cannot be readily improved by stress relief, there bing
>> insufficient overload manually to improve the spoke line.
>>
>>> If there is high stress in the elbow after the build it follows that
>>> there's enough moment present for spoke tension to maintain that
>>> stress. I'd be inclined to say that the moment is the real problem:
>>> it will allow a high-stress bending cycle in use, even if you
>>> stress-relieve, if stress relief doesn't also have the effect of
>>> also reducing that moment.
>> That's why you improve the spoke line and then stress relieve, so that
>> peak stress is far enough below yield, that fatigue failures do not
>> occur for a long time if ever. As I said, I have wheels that went
>> 300,000 miles with spoke failures at chain gouges (not in the elbow)
>> of a few outbound spokes.
>
> 300K miles without the brake track wearing out? That is outstanding.
>
> I don't think I've had anything last as long as 300K miles in my whole
> life.
nor has jobst. archive searching reveals his occasional slip-ups where
he admits that hubs, wheels and spokes have /all/ been replaced. but
the legend exists in his own mind, so that's all he needs to tell you a
story.
>
>>> But I think stress-relief probably _does_ reduce the moment by
>>> bending the elbow a bit more and by conforming it to the hub (_pace_
>>> Peter Cole's and Jobst's well-reasoned arguments why hub conformance
>>> is not likely to happen much after tensioning).
>> Forget about the moment, just tensile changes from load bearing are
>> enough to cause fatigue failure if the spoke is near yield, which it
>> is, because the elbow angle was yielded to an acute angle in spoke
>> lacing, and held there by subsequent tensioning.
>
> Yes, but as I said before, if the spoke is near yield under normal spoke
> tension _there must be a moment_. I don't see how you can have one
> without the other.
because /that/ wouldn't suit the legend!
>
> That's why I think the moment is key: it's where big stresses at the
> elbow, on the exterior, come from.
>
> I'm not denying that residual stresses from manufacture will add to
> those stresses in places.
but they're not observed to be where fatigue initiates!
|
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Date: 09 Sep 2007 12:46:18
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-09, jim beam <spamvortex@bad.example.net > wrote:
> Ben C wrote:
[...]
>> I'm not denying that residual stresses from manufacture will add to
>> those stresses in places.
>
> but they're not observed to be where fatigue initiates!
I gather from discussions that the regions of highest residual stress
are on the interior of the material, where fatigue doesn't initiate
usually for spokes.
But there is some residual stress on the exterior as well right?
Some of that might be expected to actually mitigate fatigue. But we do
have some tensile residual stress on the exterior of the inside of the
inbound spokes?
"Yes but it's a herring" or "No but it's a herring" are both acceptable
answers :)
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Date: 09 Sep 2007 21:13:52
From: jim beam
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-09, jim beam <spamvortex@bad.example.net> wrote:
>> Ben C wrote:
> [...]
>>> I'm not denying that residual stresses from manufacture will add to
>>> those stresses in places.
>> but they're not observed to be where fatigue initiates!
>
> I gather from discussions that the regions of highest residual stress
> are on the interior of the material, where fatigue doesn't initiate
> usually for spokes.
>
> But there is some residual stress on the exterior as well right?
>
> Some of that might be expected to actually mitigate fatigue. But we do
> have some tensile residual stress on the exterior of the inside of the
> inbound spokes?
>
> "Yes but it's a herring" or "No but it's a herring" are both acceptable
> answers :)
yes, there can be a small residual stress at the initiation point, but
if we _observe_ fatigue initiating at a point where there is supposed to
be /compressive/ residual stress, and we sometimes do, then clearly
residual stress is a great big red herring.
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Date: 10 Sep 2007 21:00:09
From: Jambo
Subject: Re: Yet another broken spoke
|
"jim beam" <spamvortex@bad.example.net > wrote in message
news:Z_ednQxDG8UdWXnbnZ2dnUVZ_jqdnZ2d@speakeasy.net...
> yes, there can be a small residual stress at the initiation point, but
> if we _observe_ fatigue initiating at a point where there is supposed to
> be /compressive/ residual stress, and we sometimes do, then clearly
> residual stress is a great big red herring.
Typical fucktard retro-stepping - "yeah, I didn't mean that, but yes, I did
mean that"
|
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Date: 10 Sep 2007 08:26:12
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Ben C wrote:
>> On 2007-09-09, jim beam <spamvortex@bad.example.net> wrote:
>>> Ben C wrote:
>> [...]
>>>> I'm not denying that residual stresses from manufacture will add to
>>>> those stresses in places.
>>> but they're not observed to be where fatigue initiates!
>>
>> I gather from discussions that the regions of highest residual stress
>> are on the interior of the material, where fatigue doesn't initiate
>> usually for spokes.
>>
>> But there is some residual stress on the exterior as well right?
>>
>> Some of that might be expected to actually mitigate fatigue. But we do
>> have some tensile residual stress on the exterior of the inside of the
>> inbound spokes?
>>
>> "Yes but it's a herring" or "No but it's a herring" are both acceptable
>> answers :)
>
> yes, there can be a small residual stress at the initiation point, but
> if we _observe_ fatigue initiating at a point where there is supposed to
> be /compressive/ residual stress, and we sometimes do, then clearly
> residual stress is a great big red herring.
The "we" above is actually *you*. You are the one who claims to have
seen elbow breakage on the outside over inside by a 4:1 margin. You also
claim that your spokes loosen after a short ride on a newly built wheel.
Both are symptoms of the spoke line not being corrected -- something you
also admit to not doing. The causality should be obvious.
A thread where this was beaten to death:
http://tinyurl.com/2xvaq9
Also contains the bizarre sub-thread where you display a total lack of
understanding of vectors and wheel mechanics.
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Date: 10 Sep 2007 02:55:25
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-10, jim beam <spamvortex@bad.example.net > wrote:
[...]
> yes, there can be a small residual stress at the initiation point, but
> if we _observe_ fatigue initiating at a point where there is supposed to
> be /compressive/ residual stress, and we sometimes do, then clearly
> residual stress is a great big red herring.
Yes, and this is a good argument.
I have one more question, which I've already asked but am still not
completely sure of the answer to.
If the elbow _is_ bent again during the build (which many people do do,
and can just happen) what happens to those manufacturing residual
stresses?
I would have thought they would be little more than a ghost or an echo.
We've bent the wire again-- everything's moved, the outer skin has been
stretched and compressed all over again.
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Date: 09 Sep 2007 12:03:51
From: Jambo
Subject: Re: Yet another broken spoke
|
"jim beam" <spamvortex@bad.example.net > wrote in message
news:L5SdnS6G2oL_YH7bnZ2dnUVZ_qrinZ2d@speakeasy.net...
> nor has jobst. archive searching reveals his occasional slip-ups where
> he admits that hubs, wheels and spokes have /all/ been replaced. but the
> legend exists in his own mind, so that's all he needs to tell you a story.
You know all about this, don't you fucktard? Inventing stories of
Vietnam-era composite rotors, tall tales of your "experiences" of bike
failures, your "former metallurgist" background... and who can forget the
faked Al particle seeded Koolstop brake pads you photographed just so you
can contradict JB - that was really funny.
|
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Date: 09 Sep 2007 00:35:23
From:
Subject: Re: Yet another broken spoke
|
Ben C? writes:
>>> Good point. I was careful though to say "retained stress from the
>>> build", not "residual stress" [from manufacture].
>>> The latter I have mostly put in the red herring bucket so far but
>>> keep an open mind as I am not an expert on these things.
>> I think you should review that opinion and how you came to that
>> conclusion. A permanent bend in a wire causes residual stress and
>> the one in a spoke is increased in as many as half the spokes when
>> building a wheel, as the elbow angle becomes acute from on obtuse
>> angle.
> Isn't it the other way round? The residual stresses are compressive
> on the exterior on outside of the bend (I thought) and tensile on
> the exterior of the inside. So it's the elbows that become more
> obtuse for which the building-bend adds to the manufacturing
> residual stress?
When the bend is made, the main stress is tension on the outside of
the bend and that bend is increased when the outbound spokes get their
spoke line corrected, either by spoke tension or manually. In any
event, the outside of the spoke elbows are in tensile stress on those
spokes.
>>> Retained stress from the build, which really I would lump together
>>> with poor spoke line (i.e. bending moment at the elbow) is what I
>>> suspect may be a significant factor in some failures where good
>>> quality spokes are used.
>> That cannot be readily improved by stress relief, there bing
>> insufficient overload manually to improve the spoke line.
>>> If there is high stress in the elbow after the build it follows
>>> that there's enough moment present for spoke tension to maintain
>>> that stress. I'd be inclined to say that the moment is the real
>>> problem: it will allow a high-stress bending cycle in use, even if
>>> you stress-relieve, if stress relief doesn't also have the effect
>>> of also reducing that moment.
>> That's why you improve the spoke line and then stress relieve, so
>> that peak stress is far enough below yield, that fatigue failures
>> do not occur for a long time if ever. As I said, I have wheels
>> that went 300,000 miles with spoke failures at chain gouges (not in
>> the elbow) of a few outbound spokes.
> 300K miles without the brake track wearing out? That is
> outstanding.
I didn't say with the same rims. I replaced those several times and
at least once because the rim was damaged. I did not remove the
spokes from the hub in these rim changes. Not doing so is an
important feature so that the spokes remain in the places to which
they have come to fit.
> I don't think I've had anything last as long as 300K miles in my
> whole life.
That's 30 years of at least 10,000 miles per year. As I said, I
retired that rear wheel in good condition after I broke a right rear
dropout for the second time. Old 4-speed Campagnolo Record hubs have
a lot of axle overhang and break axles. In doing so, the dropout gets
flexed and finally breaks. I'm using a Shimano 7-speed hub now with
bearings at the outer ends.
>>> But I think stress-relief probably _does_ reduce the moment by
>>> bending the elbow a bit more and by conforming it to the hub
>>> (_pace_ Peter Cole's and Jobst's well-reasoned arguments why hub
>>> conformance is not likely to happen much after tensioning).
>> Forget about the moment, just tensile changes from load bearing are
>> enough to cause fatigue failure if the spoke is near yield, which
>> it is, because the elbow angle was yielded to an acute angle in
>> spoke lacing, and held there by subsequent tensioning.
> Yes, but as I said before, if the spoke is near yield under normal
> spoke tension _there must be a moment_. I don't see how you can
> have one without the other.
A spoke that is fully supported in the aluminum flange is loaded
purely in tension as it wraps around a curved bore that matches its
inner radius. The spoke head should rest solidly on the entrance to
the flange and the spoke pulled around the corner. Such a spoke will
last a long time. The straight pull spoke came along because people
were not seeing the effect of reasonable flange bores with reasonable
flange thickness and stress relieving.
> That's why I think the moment is key: it's where big stresses at the
> elbow, on the exterior, come from.
There is no moment in a fully supported elbow and if you look at a
flange bore after removing the spoke you should see a smooth curve
that matches the spoke elbow shape.
> I'm not denying that residual stresses from manufacture will add to
> those stresses in places.
Spoke elbows should not be operating in bending mode but rather
tensile mode.
Jobst Brandt
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Date: 09 Sep 2007 03:28:23
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-09, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org > wrote:
> Ben C? writes:
[...]
>> Isn't it the other way round? The residual stresses are compressive
>> on the exterior on outside of the bend (I thought) and tensile on
>> the exterior of the inside. So it's the elbows that become more
>> obtuse for which the building-bend adds to the manufacturing
>> residual stress?
>
> When the bend is made, the main stress is tension on the outside of
> the bend
Yes but that bend springs back, leaving residual compressive stress on
the exterior on the outside?
> and that bend is increased when the outbound spokes get their
> spoke line corrected, either by spoke tension or manually. In any
> event, the outside of the spoke elbows are in tensile stress on those
> spokes.
Yes, the applied stress is on the outside of the bend on the exterior on
the outbound spokes.
[...]
>> Yes, but as I said before, if the spoke is near yield under normal
>> spoke tension _there must be a moment_. I don't see how you can
>> have one without the other.
>
> A spoke that is fully supported in the aluminum flange is loaded
> purely in tension as it wraps around a curved bore that matches its
> inner radius. The spoke head should rest solidly on the entrance to
> the flange and the spoke pulled around the corner. Such a spoke will
> last a long time. The straight pull spoke came along because people
> were not seeing the effect of reasonable flange bores with reasonable
> flange thickness and stress relieving.
>
>> That's why I think the moment is key: it's where big stresses at the
>> elbow, on the exterior, come from.
>
> There is no moment in a fully supported elbow and if you look at a
> flange bore after removing the spoke you should see a smooth curve
> that matches the spoke elbow shape.
That's what one would hope for in a good wheel, certainly.
But if there's no moment there's no stress there from the spoke line
correction bend. Because there's nothing there to hold that bend in
place.
The last time we went through this it went slightly differently.
Outbound spoke
--------------
1. You said we bend the elbow to correct the line, it can't spring back,
so the bend is held there, and so the stress remains high on the
outside. I call this "retained build stress" to avoid confusion with
manufacturing residual stress.
2. I said for spoke tension to hold the bend in place needs sufficient
moment. If the spoke is flush to the flange you don't have that
moment.
3. We repeated (1) and (2) to each other approximately 300 times.
4. Eventually you said yes but what do you mean by "flush"? It's never
100% completely totally and utterly flush. We get a little
question-mark shaped hook, the details of which are complicated.
5. I said OK so there might be a moment, retained stress might be there,
and stress-relief might get rid of it.
But now you're saying "there's no moment". In that case there is no
retained build stress on the outside of the bend. 100kgf or so _with no
moment_ is not enough to hold a bend in a spoke.
Really they're the same thing. Residual stress (the kind that remains
inside a wire after it's been bent and sprung back) requires knowledge
of history. But retained build stress is just applied stress. It doesn't
matter how it got there: if spoke tension is 100kgf and there's a
too-big radius, you have a moment, and too-high stress on the elbow
outside. No moment, nothing to worry about. If you stress-relieve and it
makes the stress go away then it necessarily also made the moment go
away.
So saying stress-relief is a process of helping things gain intimate
conformity of some kind (as jim beam has said) and saying that it yields
the bits of the cross section that are still close to yield from spoke
line correction (as you have said) pretty much amount to the same thing.
As for residual manufacturing stress-- it sounds like that might add a
bit to the tensile skin stress on the inside of the bend of the inbound
spokes. So it may have a contribution to failures of inbound spokes that
begin on the inside. But there's no reason to believe it's significant:
Even if we accept the evidence that stress-relief practice reduces
failures we don't know how much of that is to do with reducing retained
build stress as opposed to reducing manufacturing residual stress.
Since we're bending the elbow again anyway I'm inclined to think
manufacturing residual stress is basically ancient history by the the
time we've finished the wheel.
|
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Date: 10 Sep 2007 03:13:40
From:
Subject: Re: Yet another broken spoke
|
Ben C? writes:
>>> Isn't it the other way round? The residual stresses are
>>> compressive on the exterior on outside of the bend (I thought) and
>>> tensile on the exterior of the inside. So it's the elbows that
>>> become more obtuse for which the building-bend adds to the
>>> manufacturing residual stress?
>> When the bend is made, the main stress is tension on the outside of
>> the bend
> Yes but that bend springs back, leaving residual compressive stress
> on the exterior on the outside?
>> and that bend is increased when the outbound spokes get their spoke
>> line corrected, either by spoke tension or manually. In any event,
>> the outside of the spoke elbows are in tensile stress on those
>> spokes.
Increasing the bend brings it back to the prior condition where it had
tensile stress on the outside of the bend and increases that bend. If
it is a slight bend, then it may leave the outside of the elbow
neutral, but don't bet on it. If you unspoke a used wheel, you'll
note that the outbound spokes have a greater permanent bend than new
spokes, showing that they were brought to yield in the process.
> Yes, the applied stress is on the outside of the bend on the
> exterior on the outbound spokes.
>>> Yes, but as I said before, if the spoke is near yield under normal
>>> spoke tension _there must be a moment_. I don't see how you can
>>> have one without the other.
>> A spoke that is fully supported in the aluminum flange is loaded
>> purely in tension as it wraps around a curved bore that matches its
>> inner radius. The spoke head should rest solidly on the entrance
>> to the flange and the spoke pulled around the corner. Such a spoke
>> will last a long time. The straight pull spoke came along because
>> people were not seeing the effect of reasonable flange bores with
>> reasonable flange thickness and stress relieving.
>>> That's why I think the moment is key: it's where big stresses at the
>>> elbow, on the exterior, come from.
>> There is no moment in a fully supported elbow and if you look at a
>> flange bore after removing the spoke you should see a smooth curve
>> that matches the spoke elbow shape.
> That's what one would hope for in a good wheel, certainly.
Even in a less than perfect wheel build, tensile loads on a freshly
built wheel that has been stress relieved has higher stress on the
outside of the bend than on the inside, just by geometry.
> But if there's no moment there's no stress there from the spoke line
> correction bend. Because there's nothing there to hold that bend in
> place.
> The last time we went through this it went slightly differently.
Moment implied that the spoke is loaded in bending at that point, but
even a spoke that has not been stress relieved, the spoke is generally
fully supported in the aluminum of a flange as the aluminum yields.
Your "moment" seems to me to be undefined. I don't see a moment
unless the elbow is excessively long as they were for a while from DT
causing many to break.
> Outbound spoke
> --------------
> 1. You said we bend the elbow to correct the line, it can't spring
> back, so the bend is held there, and so the stress remains high
> on the outside. I call this "retained build stress" to avoid
> confusion with manufacturing residual stress.
> 2. I said for spoke tension to hold the bend in place needs
> sufficient moment. If the spoke is flush to the flange you don't
> have that moment.
> 3. We repeated (1) and (2) to each other approximately 300 times.
> 4. Eventually you said yes but what do you mean by "flush"? It's
> never 100% completely totally and utterly flush. We get a little
> question-mark shaped hook, the details of which are complicated.
> 5. I said OK so there might be a moment, retained stress might be
> there, and stress-relief might get rid of it.
> But now you're saying "there's no moment". In that case there is no
> retained build stress on the outside of the bend. 100kgf or so
> _with no moment_ is not enough to hold a bend in a spoke.
If you insist and referring to the stress in the elbow as a moment
then you are dodging the stress at that point which is the operating
effect that causes failure. If that stress can be reduced through
temporary overtightening (stress relief) than I don't see how calling
it a moment properly defines the condition.
> Really they're the same thing. Residual stress (the kind that
> remains inside a wire after it's been bent and sprung back) requires
> knowledge of history. But retained build stress is just applied
> stress. It doesn't matter how it got there: if spoke tension is
> 100kgf and there's a too-big radius, you have a moment, and too-high
> stress on the elbow outside. No moment, nothing to worry about. If
> you stress-relieve and it makes the stress go away then it
> necessarily also made the moment go away.
As I said, you'll find that spokes generally are supported throughout
the elbow bend by a yielded aluminum flange. The moment is not the
\operator here but the stress that remains in the elbow from
manufacture and build.
> So saying stress-relief is a process of helping things gain intimate
> conformity of some kind (as jim beam has said) and saying that it
> yields the bits of the cross section that are still close to yield
> from spoke line correction (as you have said) pretty much amount to
> the same thing.
I didn't say that. That is the claim by the former metallurgist who
calls it bedding-in or setting.
> As for residual manufacturing stress-- it sounds like that might add
> a bit to the tensile skin stress on the inside of the bend of the
> inbound spokes. So it may have a contribution to failures of
> inbound spokes that begin on the inside. But there's no reason to
> believe it's significant: Even if we accept the evidence that
> stress-relief practice reduces failures we don't know how much of
> that is to do with reducing retained build stress as opposed to
> reducing manufacturing residual stress.
I think I covered that and it is not as you say.
> Since we're bending the elbow again anyway I'm inclined to think
> manufacturing residual stress is basically ancient history by the
> the time we've finished the wheel.
It assures tensile stress on the outside of the elbow and in the
threads.
Jobst Brandt
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Date: 10 Sep 2007 02:48:19
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-10, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org > wrote:
[...]
>> But now you're saying "there's no moment". In that case there is no
>> retained build stress on the outside of the bend. 100kgf or so
>> _with no moment_ is not enough to hold a bend in a spoke.
>
> If you insist and referring to the stress in the elbow as a moment
> then you are dodging the stress at that point which is the operating
> effect that causes failure. If that stress can be reduced through
> temporary overtightening (stress relief) than I don't see how calling
> it a moment properly defines the condition.
Well, I've explained it as clearly as I can and I don't believe it's
that difficult to understand.
[...]
>> Really they're the same thing. Residual stress (the kind that
>> remains inside a wire after it's been bent and sprung back) requires
>> knowledge of history. But retained build stress is just applied
>> stress. It doesn't matter how it got there: if spoke tension is
>> 100kgf and there's a too-big radius, you have a moment, and too-high
>> stress on the elbow outside. No moment, nothing to worry about. If
>> you stress-relieve and it makes the stress go away then it
>> necessarily also made the moment go away.
>
> As I said, you'll find that spokes generally are supported throughout
> the elbow bend by a yielded aluminum flange. The moment is not the
> \operator here but the stress that remains in the elbow from
> manufacture and build.
Well obviously.
>> So saying stress-relief is a process of helping things gain intimate
>> conformity of some kind (as jim beam has said) and saying that it
>> yields the bits of the cross section that are still close to yield
>> from spoke line correction (as you have said) pretty much amount to
>> the same thing.
>
> I didn't say that. That is the claim by the former metallurgist who
> calls it bedding-in or setting.
I did write that rather obliquely. What I meant to say is that the fact
that parts of the cross-section are yielded by spoke line correction
belongs to your account of what happens. jim beam doesn't
spoke-line-correct manually and doesn't think they bend much when you
tighten them either.
My own small experience is closer to yours on this matter, which is not
to say that I disbelieve jim beam.
[...]
>> Since we're bending the elbow again anyway I'm inclined to think
>> manufacturing residual stress is basically ancient history by the
>> the time we've finished the wheel.
>
> It assures tensile stress on the outside of the elbow and in the
> threads.
Indeed.
|
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Date: 09 Sep 2007 22:06:24
From: jim beam
Subject: Re: Yet another broken spoke
|
jobst.brandt@stanfordalumni.org wrote:
> Ben C? writes:
>
>>>> Isn't it the other way round? The residual stresses are
>>>> compressive on the exterior on outside of the bend (I thought) and
>>>> tensile on the exterior of the inside. So it's the elbows that
>>>> become more obtuse for which the building-bend adds to the
>>>> manufacturing residual stress?
>
>>> When the bend is made, the main stress is tension on the outside of
>>> the bend
>
>> Yes but that bend springs back, leaving residual compressive stress
>> on the exterior on the outside?
>
>>> and that bend is increased when the outbound spokes get their spoke
>>> line corrected, either by spoke tension or manually. In any event,
>>> the outside of the spoke elbows are in tensile stress on those
>>> spokes.
>
> Increasing the bend brings it back to the prior condition where it had
> tensile stress on the outside of the bend and increases that bend. If
> it is a slight bend, then it may leave the outside of the elbow
> neutral, but don't bet on it. If you unspoke a used wheel, you'll
> note that the outbound spokes have a greater permanent bend than new
> spokes, showing that they were brought to yield in the process.
what? like these spokes?
http://flickr.com/photos/38636024@N00/331112190/
>
>> Yes, the applied stress is on the outside of the bend on the
>> exterior on the outbound spokes.
>
>>>> Yes, but as I said before, if the spoke is near yield under normal
>>>> spoke tension _there must be a moment_. I don't see how you can
>>>> have one without the other.
>
>>> A spoke that is fully supported in the aluminum flange is loaded
>>> purely in tension as it wraps around a curved bore that matches its
>>> inner radius. The spoke head should rest solidly on the entrance
>>> to the flange and the spoke pulled around the corner. Such a spoke
>>> will last a long time. The straight pull spoke came along because
>>> people were not seeing the effect of reasonable flange bores with
>>> reasonable flange thickness and stress relieving.
>
>>>> That's why I think the moment is key: it's where big stresses at the
>>>> elbow, on the exterior, come from.
>
>>> There is no moment in a fully supported elbow and if you look at a
>>> flange bore after removing the spoke you should see a smooth curve
>>> that matches the spoke elbow shape.
>
>> That's what one would hope for in a good wheel, certainly.
>
> Even in a less than perfect wheel build, tensile loads on a freshly
> built wheel that has been stress relieved has higher stress on the
> outside of the bend than on the inside, just by geometry.
unless the hub flange is canted. which most are these days.
>
>> But if there's no moment there's no stress there from the spoke line
>> correction bend. Because there's nothing there to hold that bend in
>> place.
>
>> The last time we went through this it went slightly differently.
>
> Moment implied that the spoke is loaded in bending at that point, but
> even a spoke that has not been stress relieved, the spoke is generally
> fully supported in the aluminum of a flange as the aluminum yields.
not against axial loading its not. and that's what we need to worry about!
> Your "moment" seems to me to be undefined. I don't see a moment
> unless the elbow is excessively long as they were for a while from DT
> causing many to break.
see above.
>
>> Outbound spoke
>> --------------
>
>> 1. You said we bend the elbow to correct the line, it can't spring
>> back, so the bend is held there, and so the stress remains high
>> on the outside. I call this "retained build stress" to avoid
>> confusion with manufacturing residual stress.
>
>> 2. I said for spoke tension to hold the bend in place needs
>> sufficient moment. If the spoke is flush to the flange you don't
>> have that moment.
>
>> 3. We repeated (1) and (2) to each other approximately 300 times.
>
>> 4. Eventually you said yes but what do you mean by "flush"? It's
>> never 100% completely totally and utterly flush. We get a little
>> question-mark shaped hook, the details of which are complicated.
>
>> 5. I said OK so there might be a moment, retained stress might be
>> there, and stress-relief might get rid of it.
>
>> But now you're saying "there's no moment". In that case there is no
>> retained build stress on the outside of the bend. 100kgf or so
>> _with no moment_ is not enough to hold a bend in a spoke.
>
> If you insist and referring to the stress in the elbow as a moment
> then you are dodging the stress at that point which is the operating
> effect that causes failure. If that stress can be reduced through
> temporary overtightening (stress relief) than I don't see how calling
> it a moment properly defines the condition.
>
>> Really they're the same thing. Residual stress (the kind that
>> remains inside a wire after it's been bent and sprung back) requires
>> knowledge of history. But retained build stress is just applied
>> stress. It doesn't matter how it got there: if spoke tension is
>> 100kgf and there's a too-big radius, you have a moment, and too-high
>> stress on the elbow outside. No moment, nothing to worry about. If
>> you stress-relieve and it makes the stress go away then it
>> necessarily also made the moment go away.
>
> As I said, you'll find that spokes generally are supported throughout
> the elbow bend by a yielded aluminum flange. The moment is not the
> \operator here but the stress that remains in the elbow from
> manufacture and build.
against one direction of lateral loading, but not axial loading or the
other direction of lateral which may be caused by an interleaving partner.
>
>> So saying stress-relief is a process of helping things gain intimate
>> conformity of some kind (as jim beam has said) and saying that it
>> yields the bits of the cross section that are still close to yield
>> from spoke line correction (as you have said) pretty much amount to
>> the same thing.
>
> I didn't say that. That is the claim by the former metallurgist who
> calls it bedding-in or setting.
er, /you/ are the spoke line "correction" guy, not me.
>
>> As for residual manufacturing stress-- it sounds like that might add
>> a bit to the tensile skin stress on the inside of the bend of the
>> inbound spokes. So it may have a contribution to failures of
>> inbound spokes that begin on the inside. But there's no reason to
>> believe it's significant: Even if we accept the evidence that
>> stress-relief practice reduces failures we don't know how much of
>> that is to do with reducing retained build stress as opposed to
>> reducing manufacturing residual stress.
>
> I think I covered that and it is not as you say.
so post some numbers then! if your assertion is true, quantify it
scientifically and publish!!!
in the mean time, the rest of us will examine actual fatigue failures
and note the inconsistency between your theory and reality - on many levels.
>
>> Since we're bending the elbow again anyway I'm inclined to think
>> manufacturing residual stress is basically ancient history by the
>> the time we've finished the wheel.
>
> It assures tensile stress on the outside of the elbow and in the
> threads.
manufacturing residual stress is supposed to be tensile on the outside
of the bend? please clarify your position on this one. same for
threads - the thread root particularly.
|
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Date: 09 Sep 2007 08:08:13
From: jim beam
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-09, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org> wrote:
>> Ben C? writes:
> [...]
>>> Isn't it the other way round? The residual stresses are compressive
>>> on the exterior on outside of the bend (I thought) and tensile on
>>> the exterior of the inside. So it's the elbows that become more
>>> obtuse for which the building-bend adds to the manufacturing
>>> residual stress?
>> When the bend is made, the main stress is tension on the outside of
>> the bend
>
> Yes but that bend springs back, leaving residual compressive stress on
> the exterior on the outside?
yes indeed.
>
>> and that bend is increased when the outbound spokes get their
>> spoke line corrected, either by spoke tension or manually. In any
>> event, the outside of the spoke elbows are in tensile stress on those
>> spokes.
>
> Yes, the applied stress is on the outside of the bend on the exterior on
> the outbound spokes.
for heads-in spokes, yes indeed.
> [...]
>>> Yes, but as I said before, if the spoke is near yield under normal
>>> spoke tension _there must be a moment_. I don't see how you can
>>> have one without the other.
>> A spoke that is fully supported in the aluminum flange is loaded
>> purely in tension as it wraps around a curved bore that matches its
>> inner radius. The spoke head should rest solidly on the entrance to
>> the flange and the spoke pulled around the corner. Such a spoke will
>> last a long time. The straight pull spoke came along because people
>> were not seeing the effect of reasonable flange bores with reasonable
>> flange thickness and stress relieving.
>>
>>> That's why I think the moment is key: it's where big stresses at the
>>> elbow, on the exterior, come from.
>> There is no moment in a fully supported elbow and if you look at a
>> flange bore after removing the spoke you should see a smooth curve
>> that matches the spoke elbow shape.
>
> That's what one would hope for in a good wheel, certainly.
>
> But if there's no moment there's no stress there from the spoke line
> correction bend. Because there's nothing there to hold that bend in
> place.
>
> The last time we went through this it went slightly differently.
>
> Outbound spoke
> --------------
>
> 1. You said we bend the elbow to correct the line, it can't spring back,
> so the bend is held there, and so the stress remains high on the
> outside. I call this "retained build stress" to avoid confusion with
> manufacturing residual stress.
> 2. I said for spoke tension to hold the bend in place needs sufficient
> moment. If the spoke is flush to the flange you don't have that
> moment.
> 3. We repeated (1) and (2) to each other approximately 300 times.
> 4. Eventually you said yes but what do you mean by "flush"? It's never
> 100% completely totally and utterly flush. We get a little
> question-mark shaped hook, the details of which are complicated.
> 5. I said OK so there might be a moment, retained stress might be there,
> and stress-relief might get rid of it.
>
> But now you're saying "there's no moment". In that case there is no
> retained build stress on the outside of the bend. 100kgf or so _with no
> moment_ is not enough to hold a bend in a spoke.
yes indeed!
>
> Really they're the same thing. Residual stress (the kind that remains
> inside a wire after it's been bent and sprung back) requires knowledge
> of history. But retained build stress is just applied stress. It doesn't
> matter how it got there: if spoke tension is 100kgf and there's a
> too-big radius, you have a moment, and too-high stress on the elbow
> outside. No moment, nothing to worry about. If you stress-relieve and it
> makes the stress go away then it necessarily also made the moment go
> away.
how can it do that if the spoke is not a straight-pull spoke?
>
> So saying stress-relief is a process of helping things gain intimate
> conformity of some kind (as jim beam has said) and saying that it yields
> the bits of the cross section that are still close to yield from spoke
> line correction (as you have said) pretty much amount to the same thing.
the conformity to which /i/ refer is that of the hub hole. the spoke
hardly changes at all if it's not bent by the builder and the hub has
canted flanges.
http://www.flickr.com/photos/38636024@N00/331112190/
>
> As for residual manufacturing stress-- it sounds like that might add a
> bit to the tensile skin stress on the inside of the bend of the inbound
> spokes. So it may have a contribution to failures of inbound spokes that
> begin on the inside. But there's no reason to believe it's significant:
> Even if we accept the evidence that stress-relief practice reduces
> failures we don't know how much of that is to do with reducing retained
> build stress as opposed to reducing manufacturing residual stress.
>
> Since we're bending the elbow again anyway I'm inclined to think
> manufacturing residual stress is basically ancient history by the the
> time we've finished the wheel.
but jobst /invented/ the practice of "stress relief" and wants to sell
books based on it!!! [p.s., just overlook chronology issues with that
invention claim, ok?]
|
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Date: 09 Sep 2007 12:52:35
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-09, jim beam <spamvortex@bad.example.net > wrote:
> Ben C wrote:
[...]
>> Really they're the same thing. Residual stress (the kind that remains
>> inside a wire after it's been bent and sprung back) requires knowledge
>> of history. But retained build stress is just applied stress. It doesn't
>> matter how it got there: if spoke tension is 100kgf and there's a
>> too-big radius, you have a moment, and too-high stress on the elbow
>> outside. No moment, nothing to worry about. If you stress-relieve and it
>> makes the stress go away then it necessarily also made the moment go
>> away.
>
> how can it do that if the spoke is not a straight-pull spoke?
Correct, it can't. The moment never goes away completely, but if it's
small enough, stresses in use are low enough that fatigue life should be
long.
>> So saying stress-relief is a process of helping things gain intimate
>> conformity of some kind (as jim beam has said) and saying that it yields
>> the bits of the cross section that are still close to yield from spoke
>> line correction (as you have said) pretty much amount to the same thing.
>
> the conformity to which /i/ refer is that of the hub hole. the spoke
> hardly changes at all if it's not bent by the builder and the hub has
> canted flanges.
A bit of both I think. When the moment is small I think the hub may
yield more as it gets harder and harder to bend the spoke.
I know it gets harder to sink wire into aluminium the deeper you go, but
I also think things are moving around and the spoke may therefore be
ploughing into some previously unvisited areas of aluminium during
"stress-relief".
But I honestly don't know.
> http://www.flickr.com/photos/38636024@N00/331112190/
But depends on the components, who's building it, etc. Spokes _can_ get
more bent than that even if you don't thumb them.
|
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Date: 08 Sep 2007 13:59:49
From: Jambo
Subject: Re: Yet another broken spoke
|
"jim beam" <spamvortex@bad.example.net > wrote in message
news:5qednYpaOMasQH_bnZ2dnUVZ_rqlnZ2d@speakeasy.net...
> but this is not a matter of faith.
With you, it's all a matter of bullshit baffles brains.
> 1. all traditional spokes of all qualities, of all materials, regardless
> of manufacturer, are all have the elbow bent in a way that has the same
> metallurgical result regarding residual stress. yet they all have
> dramatically different fatigue lives that correspond with the other
> variables such as material, surface finish, etc.
And of course, how they're used don't figure in the equation, do they?
Dumbass.
> 2. stress necessary to provide mechanical stress relief is achieved simply
> from wheel pre-tension. carl fogel illustrated this well some time ago.
Yeah, bandy about a term picked up from someone else. What does that even
mean, do you know?
> 3. regardless of 1. & 2., fatigue initiation is always from a region of
> low/zero residual stress but high load stress.
Bullshit again.
> yes there's bending, yes there's stress, and residual stress doesn't
> explain observed failures.
>
> http://www.flickr.com/photos/38636024@N00/1346747861/
>
> i regret that my magnification equipment doesn't allow me to take actual
> pics.
Because you'll be open to scrutiny, and your bullshit will show!
|
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Date: 07 Sep 2007 18:41:17
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> Ben C wrote:
>> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>> [...]
>>> It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
>>> good job. Apparently it didn't stick. I can see why Jobst no longer
>>> bothers to respond.
>>>
>>> http://tinyurl.com/29v4u2
>>
>> OK I have a question.
>>
>> jim beam> i have ignored residual stress as a factor in these failures
>> jim beam> because the majority of the fractures i've examined initiate
>> jim beam> on the /inside/ of the spoke elbow bend, not the outside
>> jim beam> [although i have examples of each]. residual stress in this
>> jim beam> location is compressive so i'm just looking at the external
>> jim beam> [+cyclic] load.
>> Mike Prime> The inside of the spoke elbow will have TENSILE residual
>> Mike Prime> stress, not compressive, because of the elastic springback
>> Mike Prime> after bending. See below. That 0.5 Sy number is for a beam;
>> Mike Prime> I'm too lazy to derive the number for a circular cross
>> Mike Prime> section right now.
>>
>> Mike Prime> Since that location has tensile residual stress, tensile
>> Mike Prime> applied mean stress from the spoke tension and bending,
>> ^^^^^^^
>>
>> Is the _applied_ stress on the inside of the elbow from spoke tension
>> and bending really tensile?
>>
>> I don't understand that. I thought when you bent a wire you got tensile
>> stress on the outside of the bend and compressive on the inside?
>>
>> I know that the residual stress, after it springs back, is tensile on
>> the inside.
>
> If the spoke has no bending moment (perfectly supported, perfect path),
> the applied stress from spoke tension will be tensile (uniform) across
> the cross section. Whatever bending force that is also present will add
> to that. The bending force can be either way depending on angular
> mismatch. If the spoke elbow is too long, another bending force will act
> to open the spoke angle further, adding to the residual (mfg) stress.
but you're ignoring the actual residual stress profile. just alluding
to residual stress being possible doesn't mean it's actually nucleating
fatigue!
>
> The worst case would be an (initial spoke) angle too acute with elbow
> too long. Both of those factors plus residual stress would all put
> tension on the inside of the elbow.
no, just having a spoke elbow offset from the spoke's longitudinal axis
will create tension on the inside of the elbow.
>
> If the spoke elbows are the right length, and the spoke angle is
> corrected, the only significant stresses should be spoke tension and
> residual.
you're omitting bending. even if the spoke is resting against the hub
flange, it can't protect against tensile stress on the inside of the
elbow, only tensile stress on the /outside/, a place which, while
fatigue does nucleate there from time to time, is not the commonest point.
> By stress relieving, the residual is reduced to non-fatiguing
> levels.
presumptive straw clutching. plastic deformation subsequent to initial
forming operations can /increase/ residual stress.
> But, if the spoke has (tensile) stress levels near yield in
> parts of the cross section, those will be reduced as they are forced to
> yield by the momentary overload
and the regions of highest residual stress are on the /inside/ of the
wire, not the inside or outside of the bend where fatigue nucleates.
> -- whatever the source. It's a "can't
> lose" proposition.
eh? you need to read this:
http://en.wikipedia.org/wiki/Fatigue_(material)#Miner.27s_rule
particularly this:
"In some circumstances, cycles of high stress followed by low stress
cause more damage than would be predicted by the rule."
sounds like our much-advocated "stress relief" scenario to me.
|
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Date: 08 Sep 2007 11:01:27
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> Ben C wrote:
>>> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>>> [...]
>>>> It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
>>>> good job. Apparently it didn't stick. I can see why Jobst no longer
>>>> bothers to respond.
>>>>
>>>> http://tinyurl.com/29v4u2
>>>
>>> OK I have a question.
>>>
>>> jim beam> i have ignored residual stress as a factor in these failures
>>> jim beam> because the majority of the fractures i've examined initiate
>>> jim beam> on the /inside/ of the spoke elbow bend, not the outside
>>> jim beam> [although i have examples of each]. residual stress in this
>>> jim beam> location is compressive so i'm just looking at the external
>>> jim beam> [+cyclic] load. Mike Prime> The inside of the spoke elbow
>>> will have TENSILE residual
>>> Mike Prime> stress, not compressive, because of the elastic springback
>>> Mike Prime> after bending. See below. That 0.5 Sy number is for a beam;
>>> Mike Prime> I'm too lazy to derive the number for a circular cross
>>> Mike Prime> section right now.
>>>
>>> Mike Prime> Since that location has tensile residual stress, tensile
>>> Mike Prime> applied mean stress from the spoke tension and bending,
>>> ^^^^^^^
>>>
>>> Is the _applied_ stress on the inside of the elbow from spoke tension
>>> and bending really tensile?
>>>
>>> I don't understand that. I thought when you bent a wire you got tensile
>>> stress on the outside of the bend and compressive on the inside?
>>>
>>> I know that the residual stress, after it springs back, is tensile on
>>> the inside.
>>
>> If the spoke has no bending moment (perfectly supported, perfect
>> path), the applied stress from spoke tension will be tensile (uniform)
>> across the cross section. Whatever bending force that is also present
>> will add to that. The bending force can be either way depending on
>> angular mismatch. If the spoke elbow is too long, another bending
>> force will act to open the spoke angle further, adding to the residual
>> (mfg) stress.
>
> but you're ignoring the actual residual stress profile. just alluding
> to residual stress being possible doesn't mean it's actually nucleating
> fatigue!
No, I'm not. You cited Luns in the context of stress profile, as far as
I could see he only confirmed Jobst's explanation and rejected yours.
I'm the only one on this NG (as far as I know) who actually tried to
measure residual stress, and found my results agreed with predictions:
http://tinyurl.com/356ru7
>
>>
>> The worst case would be an (initial spoke) angle too acute with elbow
>> too long. Both of those factors plus residual stress would all put
>> tension on the inside of the elbow.
>> If the spoke elbows are the right length, and the spoke angle is
>> corrected, the only significant stresses should be spoke tension and
>> residual.
>
> you're omitting bending. even if the spoke is resting against the hub
> flange, it can't protect against tensile stress on the inside of the
> elbow, only tensile stress on the /outside/, a place which, while
> fatigue does nucleate there from time to time, is not the commonest point.
I am not. You snipped it.
>
>> By stress relieving, the residual is reduced to non-fatiguing levels.
>
> presumptive straw clutching. plastic deformation subsequent to initial
> forming operations can /increase/ residual stress.
Of course, but stress relief doesn't cause bulk deformation. If wheel
building did, stress relief mitigates those residuals same as those from
manufacture.
>
>> But, if the spoke has (tensile) stress levels near yield in parts of
>> the cross section, those will be reduced as they are forced to yield
>> by the momentary overload
>
> and the regions of highest residual stress are on the /inside/ of the
> wire, not the inside or outside of the bend where fatigue nucleates.
See Luns Tee (again).
>> -- whatever the source. It's a "can't lose" proposition.
>
> eh? you need to read this:
> http://en.wikipedia.org/wiki/Fatigue_(material)#Miner.27s_rule
>
> particularly this:
> "In some circumstances, cycles of high stress followed by low stress
> cause more damage than would be predicted by the rule."
>
> sounds like our much-advocated "stress relief" scenario to me.
Sounds like you have no real understanding of Miner's rule.
Take the nominal -20% cyclical change in tension, add *1 cycle* of +50%
for stress relief and plug it into the formula.
|
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Date: 08 Sep 2007 08:48:01
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> Ben C wrote:
>>>> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>>>> [...]
>>>>> It was over 4 years ago. I thought Mike Prime (a metallurgist) did
>>>>> a good job. Apparently it didn't stick. I can see why Jobst no
>>>>> longer bothers to respond.
>>>>>
>>>>> http://tinyurl.com/29v4u2
>>>>
>>>> OK I have a question.
>>>>
>>>> jim beam> i have ignored residual stress as a factor in these failures
>>>> jim beam> because the majority of the fractures i've examined initiate
>>>> jim beam> on the /inside/ of the spoke elbow bend, not the outside
>>>> jim beam> [although i have examples of each]. residual stress in this
>>>> jim beam> location is compressive so i'm just looking at the external
>>>> jim beam> [+cyclic] load. Mike Prime> The inside of the spoke elbow
>>>> will have TENSILE residual
>>>> Mike Prime> stress, not compressive, because of the elastic springback
>>>> Mike Prime> after bending. See below. That 0.5 Sy number is for a beam;
>>>> Mike Prime> I'm too lazy to derive the number for a circular cross
>>>> Mike Prime> section right now.
>>>>
>>>> Mike Prime> Since that location has tensile residual stress, tensile
>>>> Mike Prime> applied mean stress from the spoke tension and bending,
>>>> ^^^^^^^
>>>>
>>>> Is the _applied_ stress on the inside of the elbow from spoke tension
>>>> and bending really tensile?
>>>>
>>>> I don't understand that. I thought when you bent a wire you got tensile
>>>> stress on the outside of the bend and compressive on the inside?
>>>>
>>>> I know that the residual stress, after it springs back, is tensile on
>>>> the inside.
>>>
>>> If the spoke has no bending moment (perfectly supported, perfect
>>> path), the applied stress from spoke tension will be tensile
>>> (uniform) across the cross section. Whatever bending force that is
>>> also present will add to that. The bending force can be either way
>>> depending on angular mismatch. If the spoke elbow is too long,
>>> another bending force will act to open the spoke angle further,
>>> adding to the residual (mfg) stress.
>>
>> but you're ignoring the actual residual stress profile. just alluding
>> to residual stress being possible doesn't mean it's actually
>> nucleating fatigue!
>
> No, I'm not. You cited Luns in the context of stress profile, as far as
> I could see he only confirmed Jobst's explanation and rejected yours.
> I'm the only one on this NG (as far as I know) who actually tried to
> measure residual stress, and found my results agreed with predictions:
>
> http://tinyurl.com/356ru7
<snip remaining crap >
eh? are you stupid? if you think that fatigue cracking that initiates
in locations where there is little or no residual stress, either
positive or negative, is /caused/ by that residual stress, you have a
profound lack of understanding. but why am i wasting my time - you
don't understand the difference between plasticity and elasticity -
fatigue is well beyond you.
|
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Date: 08 Sep 2007 13:11:21
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> but why am i wasting my time - you
> don't understand the difference between plasticity and elasticity -
> fatigue is well beyond you.
Don't go away mad....
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Date: 08 Sep 2007 10:56:17
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> but why am i wasting my time - you don't understand the difference
>> between plasticity and elasticity - fatigue is well beyond you.
>
>
> Don't go away mad....
i'm not. but you're apparently leaving still ignorant.
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Date: 07 Sep 2007 23:01:56
From:
Subject: Re: Yet another broken spoke
|
All this talk about "stress relieving" spokes - I thought "stress
relieving" was a heat treatment. Dig out the Bernzo-Matic and heat 'em
up cherry red. Quench. Heat to (straw or whatever temper temperature)
and let air cool. NOW the spokes are stress relieved.
But better de-bur the holes (on both sides) and polish all the tooling
marks out of the spokes to elininate "stress rizers" too.
All standard aircraft building technique.
Na- easier to just make sure the spokes are tensined propery and the
wheel is overdesigned and underengineered like a German car.
(ducking and running for shelter)
--
Posted via a free Usenet account from http://www.teranews.com
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Date: 07 Sep 2007 21:07:51
From: jim beam
Subject: Re: Yet another broken spoke
|
clare at snyder.on.ca wrote:
> All this talk about "stress relieving" spokes - I thought "stress
> relieving" was a heat treatment. Dig out the Bernzo-Matic and heat 'em
> up cherry red. Quench. Heat to (straw or whatever temper temperature)
> and let air cool. NOW the spokes are stress relieved.
they are, but they're also now softer and weaker - not strong enough for
their application. that's why manufacturers don't do this.
> But better de-bur the holes (on both sides) and polish all the tooling
> marks out of the spokes to elininate "stress rizers" too.
you could, but we're talking bikes - economics prevail. better to just
take reasonable steps on initial formation rather than rely on refinishing.
> All standard aircraft building technique.
indeed.
>
> Na- easier to just make sure the spokes are tensined propery and the
> wheel is overdesigned and underengineered like a German car.
>
> (ducking and running for shelter)
no need - the stupidity contestants will bleat themselves into a stupor
eventually. they're harmless.
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Date: 09 Sep 2007 13:43:08
From:
Subject: Re: Yet another broken spoke
|
On Fri, 07 Sep 2007 21:07:51 -0700, jim beam
<spamvortex@bad.example.net > wrote:
>clare at snyder.on.ca wrote:
>> All this talk about "stress relieving" spokes - I thought "stress
>> relieving" was a heat treatment. Dig out the Bernzo-Matic and heat 'em
>> up cherry red. Quench. Heat to (straw or whatever temper temperature)
>> and let air cool. NOW the spokes are stress relieved.
>
>they are, but they're also now softer and weaker - not strong enough for
>their application. that's why manufacturers don't do this.
No, properly done the spokes would be hard and stronger. (if the right
steel was used to start with)
--
Posted via a free Usenet account from http://www.teranews.com
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Date: 09 Sep 2007 21:14:07
From: jim beam
Subject: Re: Yet another broken spoke
|
clare at snyder.on.ca wrote:
> On Fri, 07 Sep 2007 21:07:51 -0700, jim beam
> <spamvortex@bad.example.net> wrote:
>
>> clare at snyder.on.ca wrote:
>>> All this talk about "stress relieving" spokes - I thought "stress
>>> relieving" was a heat treatment. Dig out the Bernzo-Matic and heat 'em
>>> up cherry red. Quench. Heat to (straw or whatever temper temperature)
>>> and let air cool. NOW the spokes are stress relieved.
>> they are, but they're also now softer and weaker - not strong enough for
>> their application. that's why manufacturers don't do this.
>
>
> No, properly done the spokes would be hard and stronger. (if the right
> steel was used to start with)
>
there are no heat treated spokes that i know of - all strengthening is
the result of cold work, and thermal stress relief would reduce that.
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Date: 08 Sep 2007 13:48:53
From: Jambo
Subject: Re: Yet another broken spoke
|
"jim beam" <spamvortex@bad.example.net > wrote in message
news:qY-dnZHxZdGEvX_bnZ2dnUVZ_i2dnZ2d@speakeasy.net...
> clare at snyder.on.ca wrote:
>> All this talk about "stress relieving" spokes - I thought "stress
>> relieving" was a heat treatment. Dig out the Bernzo-Matic and heat 'em
>> up cherry red. Quench. Heat to (straw or whatever temper temperature)
>> and let air cool. NOW the spokes are stress relieved.
>
> they are, but they're also now softer and weaker - not strong enough for
> their application. that's why manufacturers don't do this.
Hey dumbass, do you really think this sounds anywhere at all credible?
"softer and weaker" indeed, just like AL alloys having young's modulus a
magnitude less than CFRP, eh?
>> But better de-bur the holes (on both sides) and polish all the tooling
>> marks out of the spokes to elininate "stress rizers" too.
>
> you could, but we're talking bikes - economics prevail. better to just
> take reasonable steps on initial formation rather than rely on
> refinishing.
What utter nonsense.
>
>> All standard aircraft building technique.
>
> indeed.
As if you know.
>>
>> Na- easier to just make sure the spokes are tensined propery and the
>> wheel is overdesigned and underengineered like a German car.
>>
>> (ducking and running for shelter)
>
> no need - the stupidity contestants will bleat themselves into a stupor
> eventually. they're harmless.
Yah, you prove that all the time.
Just stay quiet, little turd.
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Date: 08 Sep 2007 11:12:47
From: jim beam
Subject: Re: Yet another broken spoke
|
Jambo wrote:
> "jim beam" <spamvortex@bad.example.net> wrote in message
> news:qY-dnZHxZdGEvX_bnZ2dnUVZ_i2dnZ2d@speakeasy.net...
>> clare at snyder.on.ca wrote:
>>> All this talk about "stress relieving" spokes - I thought "stress
>>> relieving" was a heat treatment. Dig out the Bernzo-Matic and heat 'em
>>> up cherry red. Quench. Heat to (straw or whatever temper temperature)
>>> and let air cool. NOW the spokes are stress relieved.
>> they are, but they're also now softer and weaker - not strong enough for
>> their application. that's why manufacturers don't do this.
>
> Hey dumbass, do you really think this sounds anywhere at all credible?
> "softer and weaker" indeed, just like AL alloys having young's modulus a
> magnitude less than CFRP, eh?
er, look into cold work some time and learn what effect it has on
hardness and strength. you /do/ know how to define "hardness" and
"strength" don't you mr. modulus?
>
>>> But better de-bur the holes (on both sides) and polish all the tooling
>>> marks out of the spokes to elininate "stress rizers" too.
>> you could, but we're talking bikes - economics prevail. better to just
>> take reasonable steps on initial formation rather than rely on
>> refinishing.
>
> What utter nonsense.
>>> All standard aircraft building technique.
>> indeed.
>
> As if you know.
>
>>> Na- easier to just make sure the spokes are tensined propery and the
>>> wheel is overdesigned and underengineered like a German car.
>>>
>>> (ducking and running for shelter)
>> no need - the stupidity contestants will bleat themselves into a stupor
>> eventually. they're harmless.
>
> Yah, you prove that all the time.
>
> Just stay quiet, little turd.
learn to use a killfile!
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Date: 09 Sep 2007 12:05:18
From: Jambo
Subject: Re: Yet another broken spoke
|
"jim beam" <spamvortex@bad.example.net > wrote in message
news:Z_udnaYG_Iu9e3_bnZ2dnUVZ_tninZ2d@speakeasy.net...
> Jambo wrote:
>>
>> Hey dumbass, do you really think this sounds anywhere at all credible?
>> "softer and weaker" indeed, just like AL alloys having young's modulus a
>> magnitude less than CFRP, eh?
>
> er, look into cold work some time and learn what effect it has on hardness
> and strength. you /do/ know how to define "hardness" and "strength" don't
> you mr. modulus?
Hardness is your thick skull being impenetrable to real knowledge. Strength
is what's lacking in all your arguments. How's that?
> learn to use a killfile!
Just stay quiet, turdball.
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Date: 07 Sep 2007 22:47:43
From:
Subject: Re: Yet another broken spoke
|
Ben C? writes:
>> It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
>> good job. Apparently it didn't stick. I can see why Jobst no longer
>> bothers to respond.
http://tinyurl.com/29v4u2
> OK I have a question.
> jb i have ignored residual stress as a factor in these failures
> jb because the majority of the fractures i've examined initiate on
> jb the /inside/ of the spoke elbow bend, not the outside [although i
> jb have examples of each]. residual stress in this location is
> jb compressive so i'm just looking at the external [+cyclic] load.
> MP The inside of the spoke elbow will have TENSILE residual stress,
> MP not compressive, because of the elastic springback after
> MP bending. See below. That 0.5 Sy number is for a beam; I'm too
> MP lazy to derive the number for a circular cross section right now.
> MP Since that location has tensile residual stress, tensile applied
> MP mean stress from the spoke tension and bending,
> Is the _applied_ stress on the inside of the elbow from spoke
> tension and bending really tensile?
As I mentioned, don't fly your kite on every breeze that comes along,
especially those sent aloft by jb. The elbow of a spoke is the last
operation in spoke manufacture and it is accomplished by extending the
head end of the spoke an appropriate length from a collet as a blunt
piston goes by to bend it just enough to make an obtuse angle.
> I don't understand that. I thought when you bent a wire you got tensile
> stress on the outside of the bend and compressive on the inside?
These loads tend to open the elbow angle so that causes tensile
stress. As Mike mentioned above, springback makes the stress reverse
from that during forming. I spent a few exchanges on that issue at
the time. You could also find them. When you bend a spoke it takes a
set only after you exceed yield stress in the extreme "fibers" of the
skin of the spoke. The farther you bend, the deeper the yield stress
reaches.
For instance, a thin wire will not easily take a bend because it must
be bent severely to go beyond yield. That's why we use braided cables
made of fine strands that do not reach yield in the bends encountered
in curves to reach the derailleur or brake to which it is attached.
In addition, there is no length change in these being helically wound
cables, all of whose strands pass through the inside and outside of
each curve (equal path length).
Thus, the core "fibers" of a spoke never go to yield (being thin
wires) and want to spring back while the outer "fibers" yields and
wants to stay bent. This causes springback when bending a wire. The
reason it doesn't spring all the way back to straight is that the
outer "fibers" resist, having taken a new shape. This resistance is
residual stress which appears as tension on the inside of the bend and
compression on the outside.
You'll find that jb learned about this on this forum just as he
learned about fretting damage to bearings while fighting it all the
way, denouncing every explanation with ridicule.
> I know that the residual stress, after it springs back, is tensile
> on the inside.
That's the one that counts and adds to the tensile and working load
stress of a spoke. That is why spokes need stress relieving after the
wheel is tensioned.
Jobst Brandt
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Date: 08 Sep 2007 04:16:43
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-07, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org > wrote:
> Ben C? writes:
[...]
>> MP Since that location has tensile residual stress, tensile applied
>> MP mean stress from the spoke tension and bending,
>
>> Is the _applied_ stress on the inside of the elbow from spoke
>> tension and bending really tensile?
[...]
>> I don't understand that. I thought when you bent a wire you got tensile
>> stress on the outside of the bend and compressive on the inside?
>
> These loads tend to open the elbow angle so that causes tensile
> stress.
Just to recap, because I thought this was (roughly) the picture:
1. I put an outbound spoke in. Its natural elbow angle is a bit too wide.
2. I tighten it up, the elbow bends a bit, making the elbow angle
smaller. It wants to spring back, but it can't, because it's
installed in the wheel and held in place.
3. This leaves applied stress that's tensile on the outside of the elbow
and compressive on the inside.
4. Momentary overload and relaxation leaves a spoke with reduced
stresses.
Do I have this (fundamentally) wrong?
Perhaps the point is it's the other way around for an inbound spoke,
whose elbow gets opened a bit by being installed in the wheel.
> As Mike mentioned above, springback makes the stress reverse
> from that during forming.
Yes, I think I understand that part. That's residual stress from spoke
forming, not retained stress from wheel-building, as I understand it.
During wheelbuilding the spoke is not able to spring back, so an
outbound spoke remains in tensile stress on the outside and compressive
on the inside until you stress-relieve.
After stress-relieving, the stresses may be the other way round again,
but more importantly, reduced in magnitude.
It seems that residual stress from forming would be mitigated and/or
dwarfed in magnitude by retained applied stress from the build? So
perhaps residual stress from forming _is_ a red herring?
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Date: 09 Sep 2007 11:17:13
From: Michael Press
Subject: Re: Yet another broken spoke
|
In article
<slrnfe4q3d.5h8.spamspam@bowser.marioworld >,
Ben C <spamspam@spam.eggs > wrote:
> It seems that residual stress from forming would be mitigated and/or
> dwarfed in magnitude by retained applied stress from the build? So
> perhaps residual stress from forming _is_ a red herring?
Retained stress from forming _plus_ applied stress from
tension in the wheel can bring some portions of the
spoke to the edge of yield. Cyclic unloading and
loading of the spoke during use can initiate fatigue
cracks.
A spoke elbow is cold formed by wrapping it around a
tool and bringing it to yield. In use an outbound spoke
elbow is wrapped around the hub flange, simulating the
tool upon which it was formed, bringing it back near
yield again. Stressing the spoke in a built up
tensioned wheel takes the spoke past the yield point.
Now in use it will not get near the yield point again.
--
Michael Press
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Date: 09 Sep 2007 21:14:26
From: jim beam
Subject: Re: Yet another broken spoke
|
Michael Press wrote:
> In article
> <slrnfe4q3d.5h8.spamspam@bowser.marioworld>,
> Ben C <spamspam@spam.eggs> wrote:
>
>> It seems that residual stress from forming would be mitigated and/or
>> dwarfed in magnitude by retained applied stress from the build? So
>> perhaps residual stress from forming _is_ a red herring?
>
> Retained stress from forming _plus_ applied stress from
> tension in the wheel can bring some portions of the
> spoke to the edge of yield.
that can't be what we find in spokes though because if it's at or even
near yield, fatigue life is minimal.
> Cyclic unloading and
> loading of the spoke during use can initiate fatigue
> cracks.
>
> A spoke elbow is cold formed by wrapping it around a
> tool and bringing it to yield. In use an outbound spoke
> elbow is wrapped around the hub flange, simulating the
> tool upon which it was formed, bringing it back near
> yield again. Stressing the spoke in a built up
> tensioned wheel takes the spoke past the yield point.
> Now in use it will not get near the yield point again.
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Date: 10 Sep 2007 10:34:55
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Michael Press wrote:
>> In article <slrnfe4q3d.5h8.spamspam@bowser.marioworld>,
>> Ben C <spamspam@spam.eggs> wrote:
>>
>>> It seems that residual stress from forming would be mitigated and/or
>>> dwarfed in magnitude by retained applied stress from the build? So
>>> perhaps residual stress from forming _is_ a red herring?
>>
>> Retained stress from forming _plus_ applied stress from tension in the
>> wheel can bring some portions of the spoke to the edge of yield.
>
> that can't be what we find in spokes though because if it's at or even
> near yield, fatigue life is minimal.
If you do the math, you'll see that the tensile stress in a nominally
tensioned spoke (1,000N) is at least 300MPa (for 2mm spoke). This is
slightly above the published yields for 302 & 304 stainless. This
corresponds to a spoke elongation of about 0.25%, which is consistent.
Published endurance limits for 302 & 304 are roughly at yield, so the
superposition of residual stress is in a critical region for fatigue
life impact.
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Date: 10 Sep 2007 10:04:38
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-10, Peter Cole <peter_cole@comcast.net > wrote:
> jim beam wrote:
>> Michael Press wrote:
>>> In article <slrnfe4q3d.5h8.spamspam@bowser.marioworld>,
>>> Ben C <spamspam@spam.eggs> wrote:
>>>
>>>> It seems that residual stress from forming would be mitigated and/or
>>>> dwarfed in magnitude by retained applied stress from the build? So
>>>> perhaps residual stress from forming _is_ a red herring?
>>>
>>> Retained stress from forming _plus_ applied stress from tension in the
>>> wheel can bring some portions of the spoke to the edge of yield.
>>
>> that can't be what we find in spokes though because if it's at or even
>> near yield, fatigue life is minimal.
>
> If you do the math, you'll see that the tensile stress in a nominally
> tensioned spoke (1,000N) is at least 300MPa (for 2mm spoke).
Is this how you did the math:
radius of 2mm diameter spoke = 1./1000 metres
area of spoke = A = pi*r**2 = 3.1415926535897929e-06
force / area = S = 1000 / A = 318309886.18379068
S/1e6 = 318.3098861837907
so 318MPa of stress.
If so then that's the axial stress on the whole spoke, never mind
elbows, right?
> This is slightly above the published yields for 302 & 304 stainless.
> This corresponds to a spoke elongation of about 0.25%, which is
> consistent.
I thought that to yield a spoke axially you needed a huge force, much
bigger than spoke tension? But these numbers imply that normal spoke
tension is enough or close to enough.
Seems weird. I thought Jobst did some experiments where he broke spokes
just by loading them axially and they failed at forces of around 1000 or
2000 kgf, or anyway something big.
Perhaps what I'm underestimating is the size of the gap between yield
stress and ultimate tensile strength.
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Date: 10 Sep 2007 16:07:17
From:
Subject: Re: Yet another broken spoke
|
On Mon, 10 Sep 2007 10:04:38 -0500, Ben C <spamspam@spam.eggs > wrote:
>On 2007-09-10, Peter Cole <peter_cole@comcast.net> wrote:
>> jim beam wrote:
>>> Michael Press wrote:
>>>> In article <slrnfe4q3d.5h8.spamspam@bowser.marioworld>,
>>>> Ben C <spamspam@spam.eggs> wrote:
>>>>
>>>>> It seems that residual stress from forming would be mitigated and/or
>>>>> dwarfed in magnitude by retained applied stress from the build? So
>>>>> perhaps residual stress from forming _is_ a red herring?
>>>>
>>>> Retained stress from forming _plus_ applied stress from tension in the
>>>> wheel can bring some portions of the spoke to the edge of yield.
>>>
>>> that can't be what we find in spokes though because if it's at or even
>>> near yield, fatigue life is minimal.
>>
>> If you do the math, you'll see that the tensile stress in a nominally
>> tensioned spoke (1,000N) is at least 300MPa (for 2mm spoke).
>
>Is this how you did the math:
>
> radius of 2mm diameter spoke = 1./1000 metres
> area of spoke = A = pi*r**2 = 3.1415926535897929e-06
> force / area = S = 1000 / A = 318309886.18379068
> S/1e6 = 318.3098861837907
>
>so 318MPa of stress.
>
>If so then that's the axial stress on the whole spoke, never mind
>elbows, right?
>
>> This is slightly above the published yields for 302 & 304 stainless.
>> This corresponds to a spoke elongation of about 0.25%, which is
>> consistent.
>
>I thought that to yield a spoke axially you needed a huge force, much
>bigger than spoke tension? But these numbers imply that normal spoke
>tension is enough or close to enough.
>
>Seems weird. I thought Jobst did some experiments where he broke spokes
>just by loading them axially and they failed at forces of around 1000 or
>2000 kgf, or anyway something big.
>
>Perhaps what I'm underestimating is the size of the gap between yield
>stress and ultimate tensile strength.
Dear Ben,
Jobst's original tests showed that 2 mm 14 gauge spokes began to fail
at about 700 pounds, 1.8mm 15 gauge at around 600 pounds.
His later tests a few years later showed failures at the same tension,
but revealed much more ductile metal:
"In contrast to tests performed for the first edtion of this book,
these spokes withstood substantial elongation before failure. Some
butted spokes stretched more than six millimeters without breaking, at
which point the test was stopped."
--p. 152, "The Bicycle Wheel," 2nd edition
Cheers,
Carl Fogel
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Date: 10 Sep 2007 22:54:22
From:
Subject: Re: Yet another broken spoke
|
On Mon, 10 Sep 2007 16:07:17 -0600, carlfogel@comcast.net wrote:
You wanted proof spoke wear in the "elbow" region could be an issue?
I said I'd look in my stash and try to find a few samples - I did this
afternoon and took a few pictures. Getting good focus with my digital
camera wasn't easy - but I got a few reasonable shots. See them at
www.on-the-net.ca/worn spokes.htm
or try this link:
http://www.on-the-net.ca/worn%20spokes.htm
I've seen lots worse, including a fair number of broken ones with
obvious signs of the same kind of wear.
--
Posted via a free Usenet account from http://www.teranews.com
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Date: 10 Sep 2007 22:04:34
From: jim beam
Subject: Re: Yet another broken spoke
|
clare at snyder.on.ca wrote:
> On Mon, 10 Sep 2007 16:07:17 -0600, carlfogel@comcast.net wrote:
>
> You wanted proof spoke wear in the "elbow" region could be an issue?
> I said I'd look in my stash and try to find a few samples - I did this
> afternoon and took a few pictures. Getting good focus with my digital
> camera wasn't easy - but I got a few reasonable shots. See them at
> www.on-the-net.ca/worn spokes.htm
> or try this link:
> http://www.on-the-net.ca/worn%20spokes.htm
>
> I've seen lots worse, including a fair number of broken ones with
> obvious signs of the same kind of wear.
while impressive, that's not wear, that's formation marking from a
particularly ugly bending mandrel. fantastic way to create a stress
riser though!
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Date: 10 Sep 2007 23:14:44
From: A Muzi
Subject: Re: Yet another broken spoke
|
clare at snyder.on.ca wrote:
> On Mon, 10 Sep 2007 16:07:17 -0600, carlfogel@comcast.net wrote:
>
> You wanted proof spoke wear in the "elbow" region could be an issue?
> I said I'd look in my stash and try to find a few samples - I did this
> afternoon and took a few pictures. Getting good focus with my digital
> camera wasn't easy - but I got a few reasonable shots. See them at
> www.on-the-net.ca/worn spokes.htm
> or try this link:
> http://www.on-the-net.ca/worn%20spokes.htm
>
> I've seen lots worse, including a fair number of broken ones with
> obvious signs of the same kind of wear.
steel hub flange, yes?
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
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Date: 11 Sep 2007 04:04:16
From:
Subject: Re: Yet another broken spoke
|
Clare who? writes:
> You wanted proof spoke wear in the "elbow" region could be an issue?
> I said I'd look in my stash and try to find a few samples - I did
> this afternoon and took a few pictures. Getting good focus with my
> digital camera wasn't easy - but I got a few reasonable shots. See
> them at:
http://www.on-the-net.ca/worn%20spokes.htm
> I've seen lots worse, including a fair number of broken ones with
> obvious signs of the same kind of wear.
If I'm not mistaken this is from a steel flange hub. I think you'll
find that theses nicks are made when the wheel is first tensioned and
that it isn't from wear. Not being able to see the inside of the
depression, I'm not certain. In any event, we weren't discussing
inexpensive galvanized spokes in steel hubs. As I said they have a
whole set of their own problems.
Please clarify the circumstances.
Jobst Brandt
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Date: 10 Sep 2007 21:38:21
From:
Subject: Re: Yet another broken spoke
|
On Mon, 10 Sep 2007 22:54:22 -0400, clare at snyder.on.ca wrote:
>On Mon, 10 Sep 2007 16:07:17 -0600, carlfogel@comcast.net wrote:
>
>You wanted proof spoke wear in the "elbow" region could be an issue?
>I said I'd look in my stash and try to find a few samples - I did this
>afternoon and took a few pictures. Getting good focus with my digital
>camera wasn't easy - but I got a few reasonable shots. See them at
>www.on-the-net.ca/worn spokes.htm
>or try this link:
>http://www.on-the-net.ca/worn%20spokes.htm
>
>I've seen lots worse, including a fair number of broken ones with
>obvious signs of the same kind of wear.
Dear Clare,
I think that you snipped whoever asked you about spoke wear in the
elbow region--it wasn't me.
The pictures baffle me. I can't think of the kind of profile in a hub
hole that would cause such damage. It looks more like gouging with a
chisel than an elbow wearing and eroding.
The other odd marks on the spokes in two pictures also puzzle me.
The second picture shows a tiny round dent and a curved gouge, both
where I can't think of anything in a hub causing the damage. The tiny
round dent might be from manufacturing, but the gouge seems random.
Here's the picture with the two marks circled:
http://i15.tinypic.com/65z9nar.jpg
The third picture shows two more odd dents or marks, equally
mystifying. Here's the picture with those two marks circled:
http://i5.tinypic.com/5y35nrd.jpg
I'm very curious to see what others with more experience say about
those marks.
Cheers,
Carl Fogel
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Date: 10 Sep 2007 23:34:12
From: A Muzi
Subject: Re: Yet another broken spoke
|
>> carlfogel@comcast.net wrote:
-lost-
> clare at snyder.on.ca wrote:
>> You wanted proof spoke wear in the "elbow" region could be an issue?
>> I said I'd look in my stash and try to find a few samples - I did this
>> afternoon and took a few pictures. Getting good focus with my digital
>> camera wasn't easy - but I got a few reasonable shots. See them at
>> www.on-the-net.ca/worn spokes.htm
>> or try this link:
>> http://www.on-the-net.ca/worn%20spokes.htm
>> I've seen lots worse, including a fair number of broken ones with
>> obvious signs of the same kind of wear.
carlfogel@comcast.net wrote:
> I think that you snipped whoever asked you about spoke wear in the
> elbow region--it wasn't me.
>
> The pictures baffle me. I can't think of the kind of profile in a hub
> hole that would cause such damage. It looks more like gouging with a
> chisel than an elbow wearing and eroding.
>
> The other odd marks on the spokes in two pictures also puzzle me.
>
> The second picture shows a tiny round dent and a curved gouge, both
> where I can't think of anything in a hub causing the damage. The tiny
> round dent might be from manufacturing, but the gouge seems random.
> Here's the picture with the two marks circled:
>
> http://i15.tinypic.com/65z9nar.jpg
>
> The third picture shows two more odd dents or marks, equally
> mystifying. Here's the picture with those two marks circled:
>
> http://i5.tinypic.com/5y35nrd.jpg
>
> I'm very curious to see what others with more experience say about
> those marks.
Looks like steel hub flanges to me. Probably with low tension and a
heavy rim. The spokes are occasionally snug against the flange but
being less than what we'd call tensioned aren't 'seated' in a hub as
most wheels ridden by r.b.t. readers. Steel hubs are simply pierced and
often have no concession to a radiused edge. The spokes show marks from
both sides of the flange.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
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Date: 10 Sep 2007 22:59:09
From:
Subject: Re: Yet another broken spoke
|
On Mon, 10 Sep 2007 23:34:12 -0500, A Muzi <am@yellowjersey.org >
wrote:
>>> carlfogel@comcast.net wrote:
>-lost-
>
>> clare at snyder.on.ca wrote:
>>> You wanted proof spoke wear in the "elbow" region could be an issue?
>>> I said I'd look in my stash and try to find a few samples - I did this
>>> afternoon and took a few pictures. Getting good focus with my digital
>>> camera wasn't easy - but I got a few reasonable shots. See them at
>>> www.on-the-net.ca/worn spokes.htm
>>> or try this link:
>>> http://www.on-the-net.ca/worn%20spokes.htm
>>> I've seen lots worse, including a fair number of broken ones with
>>> obvious signs of the same kind of wear.
>
>carlfogel@comcast.net wrote:
>> I think that you snipped whoever asked you about spoke wear in the
>> elbow region--it wasn't me.
>>
>> The pictures baffle me. I can't think of the kind of profile in a hub
>> hole that would cause such damage. It looks more like gouging with a
>> chisel than an elbow wearing and eroding.
>>
>> The other odd marks on the spokes in two pictures also puzzle me.
>>
>> The second picture shows a tiny round dent and a curved gouge, both
>> where I can't think of anything in a hub causing the damage. The tiny
>> round dent might be from manufacturing, but the gouge seems random.
>> Here's the picture with the two marks circled:
>>
>> http://i15.tinypic.com/65z9nar.jpg
>>
>> The third picture shows two more odd dents or marks, equally
>> mystifying. Here's the picture with those two marks circled:
>>
>> http://i5.tinypic.com/5y35nrd.jpg
>>
>> I'm very curious to see what others with more experience say about
>> those marks.
>
>Looks like steel hub flanges to me. Probably with low tension and a
>heavy rim. The spokes are occasionally snug against the flange but
>being less than what we'd call tensioned aren't 'seated' in a hub as
>most wheels ridden by r.b.t. readers. Steel hubs are simply pierced and
>often have no concession to a radiused edge. The spokes show marks from
>both sides of the flange.
Dear Andrew, Jobst, & Clare,
These diagrams from the 3rd edition of "The Bicycle Wheel" may show
the cause of the gouging:
http://i16.tinypic.com/542bp10.jpg
Under tension, the spoke cants in the thin, sharp-edged steel flange
described by Jobst and Andrew.
Cheers,
Carl Fogel
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Date: 11 Sep 2007 08:23:15
From:
Subject: Re: Yet another broken spoke
|
On Mon, 10 Sep 2007 22:59:09 -0600, carlfogel@comcast.net wrote:
>>
>>Looks like steel hub flanges to me. Probably with low tension and a
>>heavy rim. The spokes are occasionally snug against the flange but
>>being less than what we'd call tensioned aren't 'seated' in a hub as
>>most wheels ridden by r.b.t. readers. Steel hubs are simply pierced and
>>often have no concession to a radiused edge. The spokes show marks from
>>both sides of the flange.
>
>Dear Andrew, Jobst, & Clare,
>
>These diagrams from the 3rd edition of "The Bicycle Wheel" may show
>the cause of the gouging:
>
>http://i16.tinypic.com/542bp10.jpg
>
>Under tension, the spoke cants in the thin, sharp-edged steel flange
>described by Jobst and Andrew.
>
>Cheers,
>
>Carl Fogel
Sturmey archer hub.
--
Posted via a free Usenet account from http://www.teranews.com
|
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Date: 10 Sep 2007 23:51:17
From:
Subject: Re: Yet another broken spoke
|
On Mon, 10 Sep 2007 21:38:21 -0600, carlfogel@comcast.net wrote:
>
>The pictures baffle me. I can't think of the kind of profile in a hub
>hole that would cause such damage. It looks more like gouging with a
>chisel than an elbow wearing and eroding.
>
>The other odd marks on the spokes in two pictures also puzzle me.
>
>The second picture shows a tiny round dent and a curved gouge, both
>where I can't think of anything in a hub causing the damage. The tiny
>round dent might be from manufacturing, but the gouge seems random.
>Here's the picture with the two marks circled:
>
>http://i15.tinypic.com/65z9nar.jpg
>
>The third picture shows two more odd dents or marks, equally
>mystifying. Here's the picture with those two marks circled:
>
>http://i5.tinypic.com/5y35nrd.jpg
>
>I'm very curious to see what others with more experience say about
>those marks.
>
>Cheers,
>
>Carl Fogel
Some of the marks may have been caused while removing, but on the
first picture you will note the mark you circled was parallel to the
other wear line shown - I suspect it was the two edges of the hub
caused the wear lines. Same on the second picture.
--
Posted via a free Usenet account from http://www.teranews.com
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Date: 10 Sep 2007 15:09:18
From: Peter Cole
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-10, Peter Cole <peter_cole@comcast.net> wrote:
>> jim beam wrote:
>>> Michael Press wrote:
>>>> In article <slrnfe4q3d.5h8.spamspam@bowser.marioworld>,
>>>> Ben C <spamspam@spam.eggs> wrote:
>>>>
>>>>> It seems that residual stress from forming would be mitigated and/or
>>>>> dwarfed in magnitude by retained applied stress from the build? So
>>>>> perhaps residual stress from forming _is_ a red herring?
>>>> Retained stress from forming _plus_ applied stress from tension in the
>>>> wheel can bring some portions of the spoke to the edge of yield.
>>> that can't be what we find in spokes though because if it's at or even
>>> near yield, fatigue life is minimal.
>> If you do the math, you'll see that the tensile stress in a nominally
>> tensioned spoke (1,000N) is at least 300MPa (for 2mm spoke).
>
> Is this how you did the math:
>
> radius of 2mm diameter spoke = 1./1000 metres
> area of spoke = A = pi*r**2 = 3.1415926535897929e-06
> force / area = S = 1000 / A = 318309886.18379068
> S/1e6 = 318.3098861837907
>
> so 318MPa of stress.
>
> If so then that's the axial stress on the whole spoke, never mind
> elbows, right?
Yes.
>
>> This is slightly above the published yields for 302 & 304 stainless.
>> This corresponds to a spoke elongation of about 0.25%, which is
>> consistent.
>
> I thought that to yield a spoke axially you needed a huge force, much
> bigger than spoke tension? But these numbers imply that normal spoke
> tension is enough or close to enough.
>
> Seems weird. I thought Jobst did some experiments where he broke spokes
> just by loading them axially and they failed at forces of around 1000 or
> 2000 kgf, or anyway something big.
>
> Perhaps what I'm underestimating is the size of the gap between yield
> stress and ultimate tensile strength.
See my other reply. I quoted a number for fully annealed. Matching to
Jobst's curves indicates the actual spoke material is considerably
hardened, my mistake.
Very roughly speaking, a tensioned spoke is 1kN, begins to plastically
deform at 2kN and snaps at 3kN. (per his graphs).
|
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Date: 10 Sep 2007 17:20:37
From: M-gineering
Subject: Re: Yet another broken spoke
|
Ben C wrote:
>
> so 318MPa of stress.
>
> If so then that's the axial stress on the whole spoke, never mind
> elbows, right?
>
>> This is slightly above the published yields for 302 & 304 stainless.
>> This corresponds to a spoke elongation of about 0.25%, which is
>> consistent.
>
> I thought that to yield a spoke axially you needed a huge force, much
> bigger than spoke tension? But these numbers imply that normal spoke
> tension is enough or close to enough.
>
It is unusual to anneal spokes prior to wheelbuilding. The wire has been
coldworked and your low yieldstrenght for SS doesn't apply
--
/Marten
info(apestaartje)m-gineering(punt)nl
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Date: 10 Sep 2007 15:03:28
From: Peter Cole
Subject: Re: Yet another broken spoke
|
M-gineering wrote:
> Ben C wrote:
>
>>
>> so 318MPa of stress.
>>
>> If so then that's the axial stress on the whole spoke, never mind
>> elbows, right?
>>
>>> This is slightly above the published yields for 302 & 304 stainless.
>>> This corresponds to a spoke elongation of about 0.25%, which is
>>> consistent.
>>
>> I thought that to yield a spoke axially you needed a huge force, much
>> bigger than spoke tension? But these numbers imply that normal spoke
>> tension is enough or close to enough.
>>
>
> It is unusual to anneal spokes prior to wheelbuilding. The wire has been
> coldworked and your low yieldstrenght for SS doesn't apply
>
OK, fair enough. I see the range for 302/304 goes from 200-1,000MPa
(0.2% offset) yield, from annealed to full hard.
Jobst's curves show non-linearity at around 2kN for 1.8mm spokes, so
that puts measured yield somewhere around there (~800MPa). So, with a
working tension providing 400MPa, we need to double that to enter bulk
yield. Of course, the higher the yield, the higher the possible residual
stresses.
I assume that hardening moves the endurance limit up with the yield
(certainly no more than that), so that puts the nominal spoke (with
static load) within ~400MPa of the endurance limit. Since that's around
1/2 of yield, it seems residual stress is within range, whereas the
stress from bending at spoke crossings isn't.
|
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Date: 10 Sep 2007 22:00:34
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> M-gineering wrote:
>> Ben C wrote:
>>
>>>
>>> so 318MPa of stress.
>>>
>>> If so then that's the axial stress on the whole spoke, never mind
>>> elbows, right?
>>>
>>>> This is slightly above the published yields for 302 & 304 stainless.
>>>> This corresponds to a spoke elongation of about 0.25%, which is
>>>> consistent.
>>>
>>> I thought that to yield a spoke axially you needed a huge force, much
>>> bigger than spoke tension? But these numbers imply that normal spoke
>>> tension is enough or close to enough.
>>>
>>
>> It is unusual to anneal spokes prior to wheelbuilding. The wire has
>> been coldworked and your low yieldstrenght for SS doesn't apply
>>
>
> OK, fair enough. I see the range for 302/304 goes from 200-1,000MPa
> (0.2% offset) yield, from annealed to full hard.
>
> Jobst's curves show non-linearity at around 2kN for 1.8mm spokes, so
> that puts measured yield somewhere around there (~800MPa). So, with a
> working tension providing 400MPa, we need to double that to enter bulk
> yield. Of course, the higher the yield, the higher the possible residual
> stresses.
>
> I assume that hardening moves the endurance limit up
there is no endurance limit on that material - there is no "knee" in the
graph, there is no dislocation locking mechanism like there is in
materials that have one.
> with the yield
> (certainly no more than that), so that puts the nominal spoke (with
> static load) within ~400MPa of the endurance limit. Since that's around
> 1/2 of yield,
only in mild steel. titanium, the other common endurance limit material
is only 40% or less. the fatigue "limit" defined for stainless that can
sustain a given number of cycles is roughly 30% of yield.
> it seems residual stress is within range, whereas the
> stress from bending at spoke crossings isn't.
but fatigue is not observed to initiate at the regions where there could
be high residual stress in spokes...
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Date: 11 Sep 2007 06:22:59
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> M-gineering wrote:
>>> Ben C wrote:
>>>
>>>>
>>>> so 318MPa of stress.
>>>>
>>>> If so then that's the axial stress on the whole spoke, never mind
>>>> elbows, right?
>>>>
>>>>> This is slightly above the published yields for 302 & 304 stainless.
>>>>> This corresponds to a spoke elongation of about 0.25%, which is
>>>>> consistent.
>>>>
>>>> I thought that to yield a spoke axially you needed a huge force, much
>>>> bigger than spoke tension? But these numbers imply that normal spoke
>>>> tension is enough or close to enough.
>>>>
>>>
>>> It is unusual to anneal spokes prior to wheelbuilding. The wire has
>>> been coldworked and your low yieldstrenght for SS doesn't apply
>>>
>>
>> OK, fair enough. I see the range for 302/304 goes from 200-1,000MPa
>> (0.2% offset) yield, from annealed to full hard.
>>
>> Jobst's curves show non-linearity at around 2kN for 1.8mm spokes, so
>> that puts measured yield somewhere around there (~800MPa). So, with a
>> working tension providing 400MPa, we need to double that to enter bulk
>> yield. Of course, the higher the yield, the higher the possible
>> residual stresses.
>>
>> I assume that hardening moves the endurance limit up
>
> there is no endurance limit on that material - there is no "knee" in the
> graph, there is no dislocation locking mechanism like there is in
> materials that have one.
>
>
>> with the yield (certainly no more than that), so that puts the nominal
>> spoke (with static load) within ~400MPa of the endurance limit. Since
>> that's around 1/2 of yield,
>
> only in mild steel. titanium, the other common endurance limit material
> is only 40% or less. the fatigue "limit" defined for stainless that can
> sustain a given number of cycles is roughly 30% of yield.
We've been over this before. There is lots of evidence of SS having an
endurance limit, including MS lectures and manufacturers specs and
application design notes. I have cited this in the past and you have
dismissed it by saying that you didn't understand the mechanism
therefore it didn't exist. If that was a valid basis for exclusion we'd
have a small world.
>
>> it seems residual stress is within range, whereas the stress from
>> bending at spoke crossings isn't.
>
> but fatigue is not observed to initiate at the regions where there could
> be high residual stress in spokes...
There can be high residual stress at the surface, and there typically
is. Look at the *actual profile* I posted in the link upthread.
|
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Date: 10 Sep 2007 15:42:44
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-10, Peter Cole <peter_cole@comcast.net > wrote:
[...]
> I assume that hardening moves the endurance limit up with the yield
> (certainly no more than that), so that puts the nominal spoke (with
> static load) within ~400MPa of the endurance limit. Since that's around
> 1/2 of yield, it seems residual stress is within range,
Do you have a number for the sort of magnitudes one would expect
residual stress from forming to be?
> whereas the stress from bending at spoke crossings isn't.
Still not sure how you're working that one out. Bending is harder to
work out because you have to estimate moments which to do with any
accuracy would require taking into account the details of the geometry
around the hub hole which is complicated and I would expect to vary from
wheel to wheel.
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Date: 10 Sep 2007 18:02:13
From: Peter Cole
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-10, Peter Cole <peter_cole@comcast.net> wrote:
> [...]
>> I assume that hardening moves the endurance limit up with the yield
>> (certainly no more than that), so that puts the nominal spoke (with
>> static load) within ~400MPa of the endurance limit. Since that's around
>> 1/2 of yield, it seems residual stress is within range,
>
> Do you have a number for the sort of magnitudes one would expect
> residual stress from forming to be?
No, not really. My little experiment confirmed residual stress and its
direction in bent spokes and formed elbows, but I couldn't really
estimate magnitude.
This source says 40-90% of yield in one case:
<http://cedb.asce.org/cgi/WWWdisplay.cgi?9000025 >
This one shows typical profiles, measured with slitting, much the same
way I did it.
<http://www.lanl.gov/residual/bentbeam.shtml >
>
>> whereas the stress from bending at spoke crossings isn't.
>
> Still not sure how you're working that one out. Bending is harder to
> work out because you have to estimate moments which to do with any
> accuracy would require taking into account the details of the geometry
> around the hub hole which is complicated and I would expect to vary from
> wheel to wheel.
Simple beam deflection model.
|
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Date: 10 Sep 2007 21:53:43
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> Ben C wrote:
>> On 2007-09-10, Peter Cole <peter_cole@comcast.net> wrote:
>> [...]
>>> I assume that hardening moves the endurance limit up with the yield
>>> (certainly no more than that), so that puts the nominal spoke (with
>>> static load) within ~400MPa of the endurance limit. Since that's
>>> around 1/2 of yield, it seems residual stress is within range,
>>
>> Do you have a number for the sort of magnitudes one would expect
>> residual stress from forming to be?
>
> No, not really. My little experiment confirmed residual stress and its
> direction in bent spokes and formed elbows, but I couldn't really
> estimate magnitude.
>
> This source says 40-90% of yield in one case:
> <http://cedb.asce.org/cgi/WWWdisplay.cgi?9000025>
>
> This one shows typical profiles, measured with slitting, much the same
> way I did it.
> <http://www.lanl.gov/residual/bentbeam.shtml>
but the reason they're interested in residual stress in the large
section materials they're looking at is not fatigue - it's because of
the elastic distortion that occurs on machining.
>
>>
>>> whereas the stress from bending at spoke crossings isn't.
>>
>> Still not sure how you're working that one out. Bending is harder to
>> work out because you have to estimate moments which to do with any
>> accuracy would require taking into account the details of the geometry
>> around the hub hole which is complicated and I would expect to vary from
>> wheel to wheel.
>
> Simple beam deflection model.
|
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Date: 11 Sep 2007 06:16:36
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> Ben C wrote:
>>> On 2007-09-10, Peter Cole <peter_cole@comcast.net> wrote:
>>> [...]
>>>> I assume that hardening moves the endurance limit up with the yield
>>>> (certainly no more than that), so that puts the nominal spoke (with
>>>> static load) within ~400MPa of the endurance limit. Since that's
>>>> around 1/2 of yield, it seems residual stress is within range,
>>>
>>> Do you have a number for the sort of magnitudes one would expect
>>> residual stress from forming to be?
>>
>> No, not really. My little experiment confirmed residual stress and its
>> direction in bent spokes and formed elbows, but I couldn't really
>> estimate magnitude.
>>
>> This source says 40-90% of yield in one case:
>> <http://cedb.asce.org/cgi/WWWdisplay.cgi?9000025>
>>
>> This one shows typical profiles, measured with slitting, much the same
>> way I did it.
>> <http://www.lanl.gov/residual/bentbeam.shtml>
>
> but the reason they're interested in residual stress in the large
> section materials they're looking at is not fatigue - it's because of
> the elastic distortion that occurs on machining.
So what? What difference does it make why they're looking at residual
stress? These are just examples of its presence, typical profiles and
possible magnitudes. It also confirms the accuracy of slitting and
looking at strain.
|
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Date: 10 Sep 2007 10:43:20
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-10, M-gineering <ikmotgeenspam@m-gineering.nl > wrote:
> Ben C wrote:
>
>>
>> so 318MPa of stress.
>>
>> If so then that's the axial stress on the whole spoke, never mind
>> elbows, right?
>>
>>> This is slightly above the published yields for 302 & 304 stainless.
>>> This corresponds to a spoke elongation of about 0.25%, which is
>>> consistent.
>>
>> I thought that to yield a spoke axially you needed a huge force, much
>> bigger than spoke tension? But these numbers imply that normal spoke
>> tension is enough or close to enough.
>>
>
> It is unusual to anneal spokes prior to wheelbuilding. The wire has been
> coldworked and your low yieldstrenght for SS doesn't apply
So what is the rough figure for yield stress of the stuff they use for
spokes?
|
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Date: 10 Sep 2007 20:07:41
From: M-gineering
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-10, M-gineering <ikmotgeenspam@m-gineering.nl> wrote:
>> Ben C wrote:
>>
>>> so 318MPa of stress.
>>>
>>> If so then that's the axial stress on the whole spoke, never mind
>>> elbows, right?
>>>
>>>> This is slightly above the published yields for 302 & 304 stainless.
>>>> This corresponds to a spoke elongation of about 0.25%, which is
>>>> consistent.
>>> I thought that to yield a spoke axially you needed a huge force, much
>>> bigger than spoke tension? But these numbers imply that normal spoke
>>> tension is enough or close to enough.
>>>
>> It is unusual to anneal spokes prior to wheelbuilding. The wire has been
>> coldworked and your low yieldstrenght for SS doesn't apply
>
> So what is the rough figure for yield stress of the stuff they use for
> spokes?
tensile strenght in the middle section varies from 1000-1600 N/mm2,
yield probably 70-85% or so. The ends are not as deformed so will give a
lower figure
--
/Marten
info(apestaartje)m-gineering(punt)nl
|
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Date: 10 Sep 2007 21:54:37
From: jim beam
Subject: Re: Yet another broken spoke
|
M-gineering wrote:
> Ben C wrote:
>> On 2007-09-10, M-gineering <ikmotgeenspam@m-gineering.nl> wrote:
>>> Ben C wrote:
>>>
>>>> so 318MPa of stress.
>>>>
>>>> If so then that's the axial stress on the whole spoke, never mind
>>>> elbows, right?
>>>>
>>>>> This is slightly above the published yields for 302 & 304 stainless.
>>>>> This corresponds to a spoke elongation of about 0.25%, which is
>>>>> consistent.
>>>> I thought that to yield a spoke axially you needed a huge force, much
>>>> bigger than spoke tension? But these numbers imply that normal spoke
>>>> tension is enough or close to enough.
>>>>
>>> It is unusual to anneal spokes prior to wheelbuilding. The wire has
>>> been coldworked and your low yieldstrenght for SS doesn't apply
>>
>> So what is the rough figure for yield stress of the stuff they use for
>> spokes?
>
> tensile strenght in the middle section varies from 1000-1600 N/mm2,
> yield probably 70-85% or so. The ends are not as deformed so will give a
> lower figure
>
correct.
|
| | | | | | | | | | | | | | | | | | | | | | | |
Date: 08 Sep 2007 07:14:50
From: jim beam
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-07, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org> wrote:
>> Ben C? writes:
> [...]
>>> MP Since that location has tensile residual stress, tensile applied
>>> MP mean stress from the spoke tension and bending,
>>> Is the _applied_ stress on the inside of the elbow from spoke
>>> tension and bending really tensile?
> [...]
>>> I don't understand that. I thought when you bent a wire you got tensile
>>> stress on the outside of the bend and compressive on the inside?
>> These loads tend to open the elbow angle so that causes tensile
>> stress.
>
> Just to recap, because I thought this was (roughly) the picture:
>
> 1. I put an outbound spoke in. Its natural elbow angle is a bit too wide.
> 2. I tighten it up, the elbow bends a bit, making the elbow angle
> smaller. It wants to spring back, but it can't, because it's
> installed in the wheel and held in place.
> 3. This leaves applied stress that's tensile on the outside of the elbow
> and compressive on the inside.
> 4. Momentary overload and relaxation leaves a spoke with reduced
> stresses.
>
> Do I have this (fundamentally) wrong?
>
> Perhaps the point is it's the other way around for an inbound spoke,
> whose elbow gets opened a bit by being installed in the wheel.
>
>> As Mike mentioned above, springback makes the stress reverse
>> from that during forming.
>
> Yes, I think I understand that part. That's residual stress from spoke
> forming, not retained stress from wheel-building, as I understand it.
> During wheelbuilding the spoke is not able to spring back, so an
> outbound spoke remains in tensile stress on the outside and compressive
> on the inside until you stress-relieve.
only parts of it. read this from luns tee:
http://groups.google.com/group/rec.bicycles.tech/msg/af080b93a59cca03
most notably:
"For a more severely bent wire, the yielded layers extend deeper,
and the residual stress pattern becomes more like:
cccTCttt "
so here's the problem - that [simplified but useful] depiction shows
where the residual stress profiles would be. if residual stress were
causing fatigue, we would observe fatigue initiating at a "T" point.
instead, we observe it initiating at /both/ "c"'s and "t"'s.
"engineers" can argue all they want about what they think should be
happening, but if observed facts tell a different story, it's just so
much hot air.
>
> After stress-relieving, the stresses may be the other way round again,
> but more importantly, reduced in magnitude.
>
> It seems that residual stress from forming would be mitigated and/or
> dwarfed in magnitude by retained applied stress from the build? So
> perhaps residual stress from forming _is_ a red herring?
truth is, outside of the lab and in carefully controlled environments,
fatigue is *always* observed to initiate at surface defects. these can
be from processing, corrosion, or even inclusions within the material.
addressing each of these is observed to directly affect fatigue life.
among these, electron microscopy shows inclusion content to be a
significant fatigue initiator. removing inclusions is _proven_ to
extend fatigue life considerably.
that's why spoke manufacturers spend lots of money on expensive vacuum
degassed materials. if cheap materials could offer superior fatigue
life by way of simple stress relief, you'd better believe they'd be used.
|
| | | | | | | | | | | | | | | | | | | | | | | | |
Date: 08 Sep 2007 14:19:46
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Ben C wrote:
>> On 2007-09-07, jobst.brandt@stanfordalumni.org
>> <jobst.brandt@stanfordalumni.org> wrote:
>>> Ben C? writes:
>> [...]
>>>> MP Since that location has tensile residual stress, tensile applied
>>>> MP mean stress from the spoke tension and bending,
>>>> Is the _applied_ stress on the inside of the elbow from spoke
>>>> tension and bending really tensile?
>> [...]
>>>> I don't understand that. I thought when you bent a wire you got tensile
>>>> stress on the outside of the bend and compressive on the inside?
>>> These loads tend to open the elbow angle so that causes tensile
>>> stress.
>>
>> Just to recap, because I thought this was (roughly) the picture:
>>
>> 1. I put an outbound spoke in. Its natural elbow angle is a bit too wide.
>> 2. I tighten it up, the elbow bends a bit, making the elbow angle
>> smaller. It wants to spring back, but it can't, because it's
>> installed in the wheel and held in place.
>> 3. This leaves applied stress that's tensile on the outside of the elbow
>> and compressive on the inside.
>> 4. Momentary overload and relaxation leaves a spoke with reduced
>> stresses.
>>
>> Do I have this (fundamentally) wrong?
>>
>> Perhaps the point is it's the other way around for an inbound spoke,
>> whose elbow gets opened a bit by being installed in the wheel.
>>
>>> As Mike mentioned above, springback makes the stress reverse
>>> from that during forming.
>>
>> Yes, I think I understand that part. That's residual stress from spoke
>> forming, not retained stress from wheel-building, as I understand it.
>> During wheelbuilding the spoke is not able to spring back, so an
>> outbound spoke remains in tensile stress on the outside and compressive
>> on the inside until you stress-relieve.
>
> only parts of it. read this from luns tee:
> http://groups.google.com/group/rec.bicycles.tech/msg/af080b93a59cca03
>
> most notably:
> "For a more severely bent wire, the yielded layers extend deeper,
> and the residual stress pattern becomes more like:
>
> cccTCttt "
>
> so here's the problem - that [simplified but useful] depiction shows
> where the residual stress profiles would be. if residual stress were
> causing fatigue, we would observe fatigue initiating at a "T" point.
> instead, we observe it initiating at /both/ "c"'s and "t"'s.
>
> "engineers" can argue all they want about what they think should be
> happening, but if observed facts tell a different story, it's just so
> much hot air.
I performed the experiment Luns suggested on the above thread and posted
my results:
http://tinyurl.com/356ru7
I think that was an "observed fact". Yours?
>
>>
>> After stress-relieving, the stresses may be the other way round again,
>> but more importantly, reduced in magnitude.
>>
>> It seems that residual stress from forming would be mitigated and/or
>> dwarfed in magnitude by retained applied stress from the build? So
>> perhaps residual stress from forming _is_ a red herring?
>
> truth is, outside of the lab and in carefully controlled environments,
> fatigue is *always* observed to initiate at surface defects. these can
> be from processing, corrosion, or even inclusions within the material.
> addressing each of these is observed to directly affect fatigue life.
> among these, electron microscopy shows inclusion content to be a
> significant fatigue initiator. removing inclusions is _proven_ to
> extend fatigue life considerably.
Everybody knows this stuff. Lots of us have had nicked spokes break in
mid-span. So what? Stress + flaw = failure. Film at 11.
>
> that's why spoke manufacturers spend lots of money on expensive vacuum
> degassed materials. if cheap materials could offer superior fatigue
> life by way of simple stress relief, you'd better believe they'd be used.
Vacuum degassing was big news in the 50's. It's a cheap bulk process,
common as dirt. What else have you got?
|
| | | | | | | | | | | | | | | | | | | | | | | | | |
Date: 09 Sep 2007 06:50:28
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Ben C wrote:
>>> On 2007-09-07, jobst.brandt@stanfordalumni.org
>>> <jobst.brandt@stanfordalumni.org> wrote:
>>>> Ben C? writes:
>>> [...]
>>>>> MP Since that location has tensile residual stress, tensile applied
>>>>> MP mean stress from the spoke tension and bending,
>>>>> Is the _applied_ stress on the inside of the elbow from spoke
>>>>> tension and bending really tensile?
>>> [...]
>>>>> I don't understand that. I thought when you bent a wire you got
>>>>> tensile
>>>>> stress on the outside of the bend and compressive on the inside?
>>>> These loads tend to open the elbow angle so that causes tensile
>>>> stress.
>>>
>>> Just to recap, because I thought this was (roughly) the picture:
>>>
>>> 1. I put an outbound spoke in. Its natural elbow angle is a bit too
>>> wide.
>>> 2. I tighten it up, the elbow bends a bit, making the elbow angle
>>> smaller. It wants to spring back, but it can't, because it's
>>> installed in the wheel and held in place.
>>> 3. This leaves applied stress that's tensile on the outside of the elbow
>>> and compressive on the inside.
>>> 4. Momentary overload and relaxation leaves a spoke with reduced
>>> stresses.
>>>
>>> Do I have this (fundamentally) wrong?
>>>
>>> Perhaps the point is it's the other way around for an inbound spoke,
>>> whose elbow gets opened a bit by being installed in the wheel.
>>>
>>>> As Mike mentioned above, springback makes the stress reverse
>>>> from that during forming.
>>>
>>> Yes, I think I understand that part. That's residual stress from spoke
>>> forming, not retained stress from wheel-building, as I understand it.
>>> During wheelbuilding the spoke is not able to spring back, so an
>>> outbound spoke remains in tensile stress on the outside and compressive
>>> on the inside until you stress-relieve.
>>
>> only parts of it. read this from luns tee:
>> http://groups.google.com/group/rec.bicycles.tech/msg/af080b93a59cca03
>>
>> most notably:
>> "For a more severely bent wire, the yielded layers extend deeper,
>> and the residual stress pattern becomes more like:
>>
>> cccTCttt "
>>
>> so here's the problem - that [simplified but useful] depiction shows
>> where the residual stress profiles would be. if residual stress were
>> causing fatigue, we would observe fatigue initiating at a "T" point.
>> instead, we observe it initiating at /both/ "c"'s and "t"'s.
>>
>> "engineers" can argue all they want about what they think should be
>> happening, but if observed facts tell a different story, it's just so
>> much hot air.
>
> I performed the experiment Luns suggested on the above thread and posted
> my results:
>
> http://tinyurl.com/356ru7
>
> I think that was an "observed fact". Yours?
and your explanation of why spoke fatigue initiates at a region of
little or zero residual stress is???
http://www.flickr.com/photos/38636024@N00/1346747861/
>
>
>>
>>>
>>> After stress-relieving, the stresses may be the other way round again,
>>> but more importantly, reduced in magnitude.
>>>
>>> It seems that residual stress from forming would be mitigated and/or
>>> dwarfed in magnitude by retained applied stress from the build? So
>>> perhaps residual stress from forming _is_ a red herring?
>>
>> truth is, outside of the lab and in carefully controlled environments,
>> fatigue is *always* observed to initiate at surface defects. these
>> can be from processing, corrosion, or even inclusions within the
>> material. addressing each of these is observed to directly affect
>> fatigue life.
>> among these, electron microscopy shows inclusion content to be a
>> significant fatigue initiator. removing inclusions is _proven_ to
>> extend fatigue life considerably.
>
> Everybody knows this stuff. Lots of us have had nicked spokes break in
> mid-span. So what? Stress + flaw = failure. Film at 11.
eh? surface nicks are /not/ inclusions!!!
>
>>
>> that's why spoke manufacturers spend lots of money on expensive vacuum
>> degassed materials. if cheap materials could offer superior fatigue
>> life by way of simple stress relief, you'd better believe they'd be used.
>
> Vacuum degassing was big news in the 50's. It's a cheap bulk process,
> common as dirt. What else have you got?
it's /cheaper/ than it was, but it's still expensive. and it didn't
start being used for bike spoke material until the 70's - at the time
when jobst brandt started claiming credit for inventing other peoples
build techniques and claiming that he could thus eliminate metal
fatigue. of course, improved results from using vacuum degassed steels
were incidental and could be completely ignored in his /rigorous/
fatigue analysis...
|
| | | | | | | | | | | | | | | | | | | | | | | | | | |
Date: 09 Sep 2007 13:37:13
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Ben C wrote:
>>>> On 2007-09-07, jobst.brandt@stanfordalumni.org
>>>> <jobst.brandt@stanfordalumni.org> wrote:
>>>>> Ben C? writes:
>>>> [...]
>>>>>> MP Since that location has tensile residual stress, tensile applied
>>>>>> MP mean stress from the spoke tension and bending,
>>>>>> Is the _applied_ stress on the inside of the elbow from spoke
>>>>>> tension and bending really tensile?
>>>> [...]
>>>>>> I don't understand that. I thought when you bent a wire you got
>>>>>> tensile
>>>>>> stress on the outside of the bend and compressive on the inside?
>>>>> These loads tend to open the elbow angle so that causes tensile
>>>>> stress.
>>>>
>>>> Just to recap, because I thought this was (roughly) the picture:
>>>>
>>>> 1. I put an outbound spoke in. Its natural elbow angle is a bit too
>>>> wide.
>>>> 2. I tighten it up, the elbow bends a bit, making the elbow angle
>>>> smaller. It wants to spring back, but it can't, because it's
>>>> installed in the wheel and held in place.
>>>> 3. This leaves applied stress that's tensile on the outside of the
>>>> elbow
>>>> and compressive on the inside.
>>>> 4. Momentary overload and relaxation leaves a spoke with reduced
>>>> stresses.
>>>>
>>>> Do I have this (fundamentally) wrong?
>>>>
>>>> Perhaps the point is it's the other way around for an inbound spoke,
>>>> whose elbow gets opened a bit by being installed in the wheel.
>>>>
>>>>> As Mike mentioned above, springback makes the stress reverse
>>>>> from that during forming.
>>>>
>>>> Yes, I think I understand that part. That's residual stress from spoke
>>>> forming, not retained stress from wheel-building, as I understand it.
>>>> During wheelbuilding the spoke is not able to spring back, so an
>>>> outbound spoke remains in tensile stress on the outside and compressive
>>>> on the inside until you stress-relieve.
>>>
>>> only parts of it. read this from luns tee:
>>> http://groups.google.com/group/rec.bicycles.tech/msg/af080b93a59cca03
>>>
>>> most notably:
>>> "For a more severely bent wire, the yielded layers extend deeper,
>>> and the residual stress pattern becomes more like:
>>>
>>> cccTCttt "
>>>
>>> so here's the problem - that [simplified but useful] depiction shows
>>> where the residual stress profiles would be. if residual stress were
>>> causing fatigue, we would observe fatigue initiating at a "T" point.
>>> instead, we observe it initiating at /both/ "c"'s and "t"'s.
>>>
>>> "engineers" can argue all they want about what they think should be
>>> happening, but if observed facts tell a different story, it's just so
>>> much hot air.
>>
>> I performed the experiment Luns suggested on the above thread and
>> posted my results:
>>
>> http://tinyurl.com/356ru7
>>
>> I think that was an "observed fact". Yours?
>
> and your explanation of why spoke fatigue initiates at a region of
> little or zero residual stress is???
>
> http://www.flickr.com/photos/38636024@N00/1346747861/
Who says there's little or no residual stress at the surface? That's not
what I found when I did the experiment.
>>>
>>>>
>>>> After stress-relieving, the stresses may be the other way round again,
>>>> but more importantly, reduced in magnitude.
>>>>
>>>> It seems that residual stress from forming would be mitigated and/or
>>>> dwarfed in magnitude by retained applied stress from the build? So
>>>> perhaps residual stress from forming _is_ a red herring?
>>>
>>> truth is, outside of the lab and in carefully controlled
>>> environments, fatigue is *always* observed to initiate at surface
>>> defects. these can be from processing, corrosion, or even inclusions
>>> within the material. addressing each of these is observed to directly
>>> affect fatigue life.
>>> among these, electron microscopy shows inclusion content to be a
>>> significant fatigue initiator. removing inclusions is _proven_ to
>>> extend fatigue life considerably.
>>
>> Everybody knows this stuff. Lots of us have had nicked spokes break in
>> mid-span. So what? Stress + flaw = failure. Film at 11.
>
> eh? surface nicks are /not/ inclusions!!!
Both are defects (obviously).
>
>>
>>>
>>> that's why spoke manufacturers spend lots of money on expensive
>>> vacuum degassed materials. if cheap materials could offer superior
>>> fatigue life by way of simple stress relief, you'd better believe
>>> they'd be used.
>>
>> Vacuum degassing was big news in the 50's. It's a cheap bulk process,
>> common as dirt. What else have you got?
>
> it's /cheaper/ than it was, but it's still expensive.
No, it's not.
> and it didn't
> start being used for bike spoke material until the 70's
Cite, please. It was used in auto sheet metal by that time.
|
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Date: 09 Sep 2007 21:12:27
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>> Ben C wrote:
>>>>> On 2007-09-07, jobst.brandt@stanfordalumni.org
>>>>> <jobst.brandt@stanfordalumni.org> wrote:
>>>>>> Ben C? writes:
>>>>> [...]
>>>>>>> MP Since that location has tensile residual stress, tensile applied
>>>>>>> MP mean stress from the spoke tension and bending,
>>>>>>> Is the _applied_ stress on the inside of the elbow from spoke
>>>>>>> tension and bending really tensile?
>>>>> [...]
>>>>>>> I don't understand that. I thought when you bent a wire you got
>>>>>>> tensile
>>>>>>> stress on the outside of the bend and compressive on the inside?
>>>>>> These loads tend to open the elbow angle so that causes tensile
>>>>>> stress.
>>>>>
>>>>> Just to recap, because I thought this was (roughly) the picture:
>>>>>
>>>>> 1. I put an outbound spoke in. Its natural elbow angle is a bit too
>>>>> wide.
>>>>> 2. I tighten it up, the elbow bends a bit, making the elbow angle
>>>>> smaller. It wants to spring back, but it can't, because it's
>>>>> installed in the wheel and held in place.
>>>>> 3. This leaves applied stress that's tensile on the outside of the
>>>>> elbow
>>>>> and compressive on the inside.
>>>>> 4. Momentary overload and relaxation leaves a spoke with reduced
>>>>> stresses.
>>>>>
>>>>> Do I have this (fundamentally) wrong?
>>>>>
>>>>> Perhaps the point is it's the other way around for an inbound spoke,
>>>>> whose elbow gets opened a bit by being installed in the wheel.
>>>>>
>>>>>> As Mike mentioned above, springback makes the stress reverse
>>>>>> from that during forming.
>>>>>
>>>>> Yes, I think I understand that part. That's residual stress from spoke
>>>>> forming, not retained stress from wheel-building, as I understand it.
>>>>> During wheelbuilding the spoke is not able to spring back, so an
>>>>> outbound spoke remains in tensile stress on the outside and
>>>>> compressive
>>>>> on the inside until you stress-relieve.
>>>>
>>>> only parts of it. read this from luns tee:
>>>> http://groups.google.com/group/rec.bicycles.tech/msg/af080b93a59cca03
>>>>
>>>> most notably:
>>>> "For a more severely bent wire, the yielded layers extend deeper,
>>>> and the residual stress pattern becomes more like:
>>>>
>>>> cccTCttt "
>>>>
>>>> so here's the problem - that [simplified but useful] depiction shows
>>>> where the residual stress profiles would be. if residual stress
>>>> were causing fatigue, we would observe fatigue initiating at a "T"
>>>> point. instead, we observe it initiating at /both/ "c"'s and "t"'s.
>>>>
>>>> "engineers" can argue all they want about what they think should be
>>>> happening, but if observed facts tell a different story, it's just
>>>> so much hot air.
>>>
>>> I performed the experiment Luns suggested on the above thread and
>>> posted my results:
>>>
>>> http://tinyurl.com/356ru7
>>>
>>> I think that was an "observed fact". Yours?
>>
>> and your explanation of why spoke fatigue initiates at a region of
>> little or zero residual stress is???
>>
>> http://www.flickr.com/photos/38636024@N00/1346747861/
>
> Who says there's little or no residual stress at the surface? That's not
> what I found when I did the experiment.
but you did! you obviously didn't understand what you were observing.
>
>>>>
>>>>>
>>>>> After stress-relieving, the stresses may be the other way round again,
>>>>> but more importantly, reduced in magnitude.
>>>>>
>>>>> It seems that residual stress from forming would be mitigated and/or
>>>>> dwarfed in magnitude by retained applied stress from the build? So
>>>>> perhaps residual stress from forming _is_ a red herring?
>>>>
>>>> truth is, outside of the lab and in carefully controlled
>>>> environments, fatigue is *always* observed to initiate at surface
>>>> defects. these can be from processing, corrosion, or even
>>>> inclusions within the material. addressing each of these is observed
>>>> to directly affect fatigue life.
>>>> among these, electron microscopy shows inclusion content to be a
>>>> significant fatigue initiator. removing inclusions is _proven_ to
>>>> extend fatigue life considerably.
>>>
>>> Everybody knows this stuff. Lots of us have had nicked spokes break
>>> in mid-span. So what? Stress + flaw = failure. Film at 11.
>>
>> eh? surface nicks are /not/ inclusions!!!
>
> Both are defects (obviously).
wriggle, squirm. a nick is not an inclusion. period.
>
>>
>>>
>>>>
>>>> that's why spoke manufacturers spend lots of money on expensive
>>>> vacuum degassed materials. if cheap materials could offer superior
>>>> fatigue life by way of simple stress relief, you'd better believe
>>>> they'd be used.
>>>
>>> Vacuum degassing was big news in the 50's. It's a cheap bulk process,
>>> common as dirt. What else have you got?
>>
>> it's /cheaper/ than it was, but it's still expensive.
>
> No, it's not.
er, it is actually.
>
>> and it didn't
>> start being used for bike spoke material until the 70's
>
> Cite, please. It was used in auto sheet metal by that time.
not even in the 80's big guy. that's the last time i went through a
strip mill and it was either open ingot or con-cast. look at this stuff
under a microscope some time and you'll see the evidence for yourself.
|
| | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Date: 10 Sep 2007 08:19:05
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>>> jim beam wrote:
>>>>> Ben C wrote:
>>>>>> On 2007-09-07, jobst.brandt@stanfordalumni.org
>>>>>> <jobst.brandt@stanfordalumni.org> wrote:
>>>>>>> Ben C? writes:
>>>>>> [...]
>>>>>>>> MP Since that location has tensile residual stress, tensile applied
>>>>>>>> MP mean stress from the spoke tension and bending,
>>>>>>>> Is the _applied_ stress on the inside of the elbow from spoke
>>>>>>>> tension and bending really tensile?
>>>>>> [...]
>>>>>>>> I don't understand that. I thought when you bent a wire you got
>>>>>>>> tensile
>>>>>>>> stress on the outside of the bend and compressive on the inside?
>>>>>>> These loads tend to open the elbow angle so that causes tensile
>>>>>>> stress.
>>>>>>
>>>>>> Just to recap, because I thought this was (roughly) the picture:
>>>>>>
>>>>>> 1. I put an outbound spoke in. Its natural elbow angle is a bit
>>>>>> too wide.
>>>>>> 2. I tighten it up, the elbow bends a bit, making the elbow angle
>>>>>> smaller. It wants to spring back, but it can't, because it's
>>>>>> installed in the wheel and held in place.
>>>>>> 3. This leaves applied stress that's tensile on the outside of the
>>>>>> elbow
>>>>>> and compressive on the inside.
>>>>>> 4. Momentary overload and relaxation leaves a spoke with reduced
>>>>>> stresses.
>>>>>>
>>>>>> Do I have this (fundamentally) wrong?
>>>>>>
>>>>>> Perhaps the point is it's the other way around for an inbound spoke,
>>>>>> whose elbow gets opened a bit by being installed in the wheel.
>>>>>>
>>>>>>> As Mike mentioned above, springback makes the stress reverse
>>>>>>> from that during forming.
>>>>>>
>>>>>> Yes, I think I understand that part. That's residual stress from
>>>>>> spoke
>>>>>> forming, not retained stress from wheel-building, as I understand it.
>>>>>> During wheelbuilding the spoke is not able to spring back, so an
>>>>>> outbound spoke remains in tensile stress on the outside and
>>>>>> compressive
>>>>>> on the inside until you stress-relieve.
>>>>>
>>>>> only parts of it. read this from luns tee:
>>>>> http://groups.google.com/group/rec.bicycles.tech/msg/af080b93a59cca03
>>>>>
>>>>> most notably:
>>>>> "For a more severely bent wire, the yielded layers extend deeper,
>>>>> and the residual stress pattern becomes more like:
>>>>>
>>>>> cccTCttt "
>>>>>
>>>>> so here's the problem - that [simplified but useful] depiction
>>>>> shows where the residual stress profiles would be. if residual
>>>>> stress were causing fatigue, we would observe fatigue initiating at
>>>>> a "T" point. instead, we observe it initiating at /both/ "c"'s and
>>>>> "t"'s.
>>>>>
>>>>> "engineers" can argue all they want about what they think should be
>>>>> happening, but if observed facts tell a different story, it's just
>>>>> so much hot air.
>>>>
>>>> I performed the experiment Luns suggested on the above thread and
>>>> posted my results:
>>>>
>>>> http://tinyurl.com/356ru7
>>>>
>>>> I think that was an "observed fact". Yours?
>>>
>>> and your explanation of why spoke fatigue initiates at a region of
>>> little or zero residual stress is???
>>>
>>> http://www.flickr.com/photos/38636024@N00/1346747861/
>>
>> Who says there's little or no residual stress at the surface? That's
>> not what I found when I did the experiment.
>
> but you did! you obviously didn't understand what you were observing.
Why don't you post your "explanation" then?
>
>
>>
>>>>>
>>>>>>
>>>>>> After stress-relieving, the stresses may be the other way round
>>>>>> again,
>>>>>> but more importantly, reduced in magnitude.
>>>>>>
>>>>>> It seems that residual stress from forming would be mitigated and/or
>>>>>> dwarfed in magnitude by retained applied stress from the build? So
>>>>>> perhaps residual stress from forming _is_ a red herring?
>>>>>
>>>>> truth is, outside of the lab and in carefully controlled
>>>>> environments, fatigue is *always* observed to initiate at surface
>>>>> defects. these can be from processing, corrosion, or even
>>>>> inclusions within the material. addressing each of these is
>>>>> observed to directly affect fatigue life.
>>>>> among these, electron microscopy shows inclusion content to be a
>>>>> significant fatigue initiator. removing inclusions is _proven_ to
>>>>> extend fatigue life considerably.
>>>>
>>>> Everybody knows this stuff. Lots of us have had nicked spokes break
>>>> in mid-span. So what? Stress + flaw = failure. Film at 11.
>>>
>>> eh? surface nicks are /not/ inclusions!!!
>>
>> Both are defects (obviously).
>
> wriggle, squirm. a nick is not an inclusion. period.
No kidding, but they're both defects, flaws, stress concentrators --
take your pick -- or perhaps you'd like to explain why an "inclusion" is
a special form of defect from a fatigue POV?
>
>>
>>>
>>>>
>>>>>
>>>>> that's why spoke manufacturers spend lots of money on expensive
>>>>> vacuum degassed materials. if cheap materials could offer superior
>>>>> fatigue life by way of simple stress relief, you'd better believe
>>>>> they'd be used.
>>>>
>>>> Vacuum degassing was big news in the 50's. It's a cheap bulk
>>>> process, common as dirt. What else have you got?
>>>
>>> it's /cheaper/ than it was, but it's still expensive.
>>
>> No, it's not.
>
> er, it is actually.
>
>
>>
>>> and it didn't
>>> start being used for bike spoke material until the 70's
>>
>> Cite, please. It was used in auto sheet metal by that time.
>
> not even in the 80's big guy. that's the last time i went through a
> strip mill and it was either open ingot or con-cast. look at this stuff
> under a microscope some time and you'll see the evidence for yourself.
Used by the Japanese for auto bodies in the 70's. US by 80's, little
man. How can this be "expensive" if it's used in massive quantities in cars?
|
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Date: 10 Sep 2007 22:27:57
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>> Peter Cole wrote:
>>>>> jim beam wrote:
>>>>>> Ben C wrote:
>>>>>>> On 2007-09-07, jobst.brandt@stanfordalumni.org
>>>>>>> <jobst.brandt@stanfordalumni.org> wrote:
>>>>>>>> Ben C? writes:
>>>>>>> [...]
>>>>>>>>> MP Since that location has tensile residual stress, tensile
>>>>>>>>> applied
>>>>>>>>> MP mean stress from the spoke tension and bending,
>>>>>>>>> Is the _applied_ stress on the inside of the elbow from spoke
>>>>>>>>> tension and bending really tensile?
>>>>>>> [...]
>>>>>>>>> I don't understand that. I thought when you bent a wire you got
>>>>>>>>> tensile
>>>>>>>>> stress on the outside of the bend and compressive on the inside?
>>>>>>>> These loads tend to open the elbow angle so that causes tensile
>>>>>>>> stress.
>>>>>>>
>>>>>>> Just to recap, because I thought this was (roughly) the picture:
>>>>>>>
>>>>>>> 1. I put an outbound spoke in. Its natural elbow angle is a bit
>>>>>>> too wide.
>>>>>>> 2. I tighten it up, the elbow bends a bit, making the elbow angle
>>>>>>> smaller. It wants to spring back, but it can't, because it's
>>>>>>> installed in the wheel and held in place.
>>>>>>> 3. This leaves applied stress that's tensile on the outside of
>>>>>>> the elbow
>>>>>>> and compressive on the inside.
>>>>>>> 4. Momentary overload and relaxation leaves a spoke with reduced
>>>>>>> stresses.
>>>>>>>
>>>>>>> Do I have this (fundamentally) wrong?
>>>>>>>
>>>>>>> Perhaps the point is it's the other way around for an inbound spoke,
>>>>>>> whose elbow gets opened a bit by being installed in the wheel.
>>>>>>>
>>>>>>>> As Mike mentioned above, springback makes the stress reverse
>>>>>>>> from that during forming.
>>>>>>>
>>>>>>> Yes, I think I understand that part. That's residual stress from
>>>>>>> spoke
>>>>>>> forming, not retained stress from wheel-building, as I understand
>>>>>>> it.
>>>>>>> During wheelbuilding the spoke is not able to spring back, so an
>>>>>>> outbound spoke remains in tensile stress on the outside and
>>>>>>> compressive
>>>>>>> on the inside until you stress-relieve.
>>>>>>
>>>>>> only parts of it. read this from luns tee:
>>>>>> http://groups.google.com/group/rec.bicycles.tech/msg/af080b93a59cca03
>>>>>>
>>>>>> most notably:
>>>>>> "For a more severely bent wire, the yielded layers extend deeper,
>>>>>> and the residual stress pattern becomes more like:
>>>>>>
>>>>>> cccTCttt "
>>>>>>
>>>>>> so here's the problem - that [simplified but useful] depiction
>>>>>> shows where the residual stress profiles would be. if residual
>>>>>> stress were causing fatigue, we would observe fatigue initiating
>>>>>> at a "T" point. instead, we observe it initiating at /both/ "c"'s
>>>>>> and "t"'s.
>>>>>>
>>>>>> "engineers" can argue all they want about what they think should
>>>>>> be happening, but if observed facts tell a different story, it's
>>>>>> just so much hot air.
>>>>>
>>>>> I performed the experiment Luns suggested on the above thread and
>>>>> posted my results:
>>>>>
>>>>> http://tinyurl.com/356ru7
>>>>>
>>>>> I think that was an "observed fact". Yours?
>>>>
>>>> and your explanation of why spoke fatigue initiates at a region of
>>>> little or zero residual stress is???
>>>>
>>>> http://www.flickr.com/photos/38636024@N00/1346747861/
>>>
>>> Who says there's little or no residual stress at the surface? That's
>>> not what I found when I did the experiment.
>>
>> but you did! you obviously didn't understand what you were observing.
>
> Why don't you post your "explanation" then?
you're evidencing an adjustment in equilibrium if there's residual
stress present. but it does not evidence residual stress at the surface!
>
>
>>
>>
>>>
>>>>>>
>>>>>>>
>>>>>>> After stress-relieving, the stresses may be the other way round
>>>>>>> again,
>>>>>>> but more importantly, reduced in magnitude.
>>>>>>>
>>>>>>> It seems that residual stress from forming would be mitigated and/or
>>>>>>> dwarfed in magnitude by retained applied stress from the build? So
>>>>>>> perhaps residual stress from forming _is_ a red herring?
>>>>>>
>>>>>> truth is, outside of the lab and in carefully controlled
>>>>>> environments, fatigue is *always* observed to initiate at surface
>>>>>> defects. these can be from processing, corrosion, or even
>>>>>> inclusions within the material. addressing each of these is
>>>>>> observed to directly affect fatigue life.
>>>>>> among these, electron microscopy shows inclusion content to be a
>>>>>> significant fatigue initiator. removing inclusions is _proven_ to
>>>>>> extend fatigue life considerably.
>>>>>
>>>>> Everybody knows this stuff. Lots of us have had nicked spokes break
>>>>> in mid-span. So what? Stress + flaw = failure. Film at 11.
>>>>
>>>> eh? surface nicks are /not/ inclusions!!!
>>>
>>> Both are defects (obviously).
>>
>> wriggle, squirm. a nick is not an inclusion. period.
>
> No kidding, but they're both defects, flaws, stress concentrators --
> take your pick -- or perhaps you'd like to explain why an "inclusion" is
> a special form of defect from a fatigue POV?
sure - if surface defects are controlled and kept below a certain
feature size, fatigue can be substantially mitigated.
http://www.flickr.com/photos/38636024@N00/340348242/
[that's not an explanation, just an illustration.]
but in searching for an explanation of why even mirror polished
materials still initiate fatigue at the surface, it was found that
fatigue was initiating at inclusions where they interrupted the surface.
removing the inclusions removed these initiators and fatigue life was
found to be improved again.
>
>
>>
>>>
>>>>
>>>>>
>>>>>>
>>>>>> that's why spoke manufacturers spend lots of money on expensive
>>>>>> vacuum degassed materials. if cheap materials could offer
>>>>>> superior fatigue life by way of simple stress relief, you'd better
>>>>>> believe they'd be used.
>>>>>
>>>>> Vacuum degassing was big news in the 50's. It's a cheap bulk
>>>>> process, common as dirt. What else have you got?
>>>>
>>>> it's /cheaper/ than it was, but it's still expensive.
>>>
>>> No, it's not.
>>
>> er, it is actually.
>>
>>
>>>
>>>> and it didn't
>>>> start being used for bike spoke material until the 70's
>>>
>>> Cite, please. It was used in auto sheet metal by that time.
>>
>> not even in the 80's big guy. that's the last time i went through a
>> strip mill and it was either open ingot or con-cast. look at this stuff
>> under a microscope some time and you'll see the evidence for yourself.
>
> Used by the Japanese for auto bodies in the 70's. US by 80's, little
> man. How can this be "expensive" if it's used in massive quantities in
> cars?
but wasn't! not for bulk sheet. maybe you're thinking of oxygen lancing?
http://en.wikipedia.org/wiki/Basic_oxygen_steelmaking
|
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Date: 11 Sep 2007 07:29:58
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>>>>> Vacuum degassing was big news in the 50's. It's a cheap bulk
>>>>>> process, common as dirt. What else have you got?
>>>>>
>>>>> it's /cheaper/ than it was, but it's still expensive.
>>>>
>>>> No, it's not.
>>>
>>> er, it is actually.
>>>
>>>
>>>>
>>>>> and it didn't
>>>>> start being used for bike spoke material until the 70's
>>>>
>>>> Cite, please. It was used in auto sheet metal by that time.
>>>
>>> not even in the 80's big guy. that's the last time i went through a
>>> strip mill and it was either open ingot or con-cast. look at this stuff
>>> under a microscope some time and you'll see the evidence for yourself.
>>
>> Used by the Japanese for auto bodies in the 70's. US by 80's, little
>> man. How can this be "expensive" if it's used in massive quantities in
>> cars?
>
> but wasn't! not for bulk sheet. maybe you're thinking of oxygen lancing?
>
> http://en.wikipedia.org/wiki/Basic_oxygen_steelmaking
No. From that article (did you read it?):
"The first basic oxygen steelmaking process was the LD process developed
in 1952 by voestalpine AG in Linz, Austria. Some major steelmaking
companies in the US did not convert to this process for decades, with
the last Bessemer converter still operating commercially until 1968.
The LD process replaced both the previously common Siemens-Martin
process, also known as the open-hearth process, and the Bessemer process."
As you should know, vacuum degassing is not related to the "LD" process
which is merely an upgrade to the original Bessemer process, using
oxygen instead of air.
As for vacuum degassing (your magic process)
<http://www.memagazine.org/backissues/membersonly/april98/features/vacuum/vacuum.html >
"Vacuum-degassing systems, which are all customized, fall into two
categories. The first type, RH recirculating degassers invented by
Heraeus-Rheinstahl in Germany, involves inserting two legs, or snorkels,
of a vacuum chamber into a ladle of liquid steel. The metal is drawn
into the chamber via one snorkel that injects argon to promote
turbulence; it is then exposed to the vacuum to remove gases and
recirculated back through the other snorkel. The other system, a tank
degasser, is a vessel into which the ladle is sent and stirred by the
injection of argon. The chamber is depressurized to remove gases, and
finally the ladle is removed."
As for the timeline:
"Cramb noted that automakers' demand for ultralow-carbon sheet steel to
make lightweight but durable car panels for more-fuel-efficient cars has
been the major factor driving vacuum degassing's growing share of the
sheet-steel market in the later 1980s and early 1990s.
"One plant has been making over 1.2 million tons of degassed sheet steel
to supply the automotive market" out of an annual production of 6
million tons, according to Ron Holmes, a metallurgical engineer and
senior process consultant at Kvaerner Metals, a subsidiary of Kvaerner
ASA in Oslo, Norway. Kvaerner Metals has designed and installed numerous
vacuum-degassing systems for processing sheet steel for automotive end
users.
"Although this is a relatively new story in the United States, dating
from the late 1980s, Japanese steel makers were degassing sheet metal
for autos at least 10 years earlier,""
|
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Date: 11 Sep 2007 21:14:04
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>> Peter Cole wrote:
>
>>>>>>> Vacuum degassing was big news in the 50's. It's a cheap bulk
>>>>>>> process, common as dirt. What else have you got?
>>>>>>
>>>>>> it's /cheaper/ than it was, but it's still expensive.
>>>>>
>>>>> No, it's not.
>>>>
>>>> er, it is actually.
>>>>
>>>>
>>>>>
>>>>>> and it didn't
>>>>>> start being used for bike spoke material until the 70's
>>>>>
>>>>> Cite, please. It was used in auto sheet metal by that time.
>>>>
>>>> not even in the 80's big guy. that's the last time i went through a
>>>> strip mill and it was either open ingot or con-cast. look at this
>>>> stuff
>>>> under a microscope some time and you'll see the evidence for yourself.
>>>
>>> Used by the Japanese for auto bodies in the 70's. US by 80's, little
>>> man. How can this be "expensive" if it's used in massive quantities
>>> in cars?
>>
>> but wasn't! not for bulk sheet. maybe you're thinking of oxygen
>> lancing?
>>
>> http://en.wikipedia.org/wiki/Basic_oxygen_steelmaking
>
> No. From that article (did you read it?):
>
> "The first basic oxygen steelmaking process was the LD process developed
> in 1952 by voestalpine AG in Linz, Austria. Some major steelmaking
> companies in the US did not convert to this process for decades, with
> the last Bessemer converter still operating commercially until 1968.
>
> The LD process replaced both the previously common Siemens-Martin
> process, also known as the open-hearth process, and the Bessemer process."
>
> As you should know, vacuum degassing is not related to the "LD" process
> which is merely an upgrade to the original Bessemer process, using
> oxygen instead of air.
not only did i read it, i've done it. and it's the process that
produces the majority of the material used in bulk product like sheet,
rod, bar, etc. used today. the product is good enough that you don't
need to worry too much about additional refining unless you have a
special use.
>
> As for vacuum degassing (your magic process)
> <http://www.memagazine.org/backissues/membersonly/april98/features/vacuum/vacuum.html>
>
>
> "Vacuum-degassing systems, which are all customized, fall into two
> categories. The first type, RH recirculating degassers invented by
> Heraeus-Rheinstahl in Germany, involves inserting two legs, or snorkels,
> of a vacuum chamber into a ladle of liquid steel. The metal is drawn
> into the chamber via one snorkel that injects argon to promote
> turbulence; it is then exposed to the vacuum to remove gases and
> recirculated back through the other snorkel. The other system, a tank
> degasser, is a vessel into which the ladle is sent and stirred by the
> injection of argon. The chamber is depressurized to remove gases, and
> finally the ladle is removed."
>
> As for the timeline:
>
> "Cramb noted that automakers' demand for ultralow-carbon sheet steel to
> make lightweight but durable car panels for more-fuel-efficient cars has
> been the major factor driving vacuum degassing's growing share of the
> sheet-steel market in the later 1980s and early 1990s.
>
> "One plant has been making over 1.2 million tons of degassed sheet steel
> to supply the automotive market" out of an annual production of 6
> million tons, according to Ron Holmes, a metallurgical engineer and
> senior process consultant at Kvaerner Metals, a subsidiary of Kvaerner
> ASA in Oslo, Norway. Kvaerner Metals has designed and installed numerous
> vacuum-degassing systems for processing sheet steel for automotive end
> users.
>
> "Although this is a relatively new story in the United States, dating
> from the late 1980s, Japanese steel makers were degassing sheet metal
> for autos at least 10 years earlier,""
ok, first, 10 points for producing an interesting article for once.
second, if you read further, you'll see that it gets slightly more
specific about the product this material is used to produce. this may
indeed be used in some sheet used in vehicles, but price alone prohibits
it being used for the majority - it would only make sense for some
chassis componentry and other fatigued components like suspension and
engine bolts. and even then, not every manufacturer would be
interested. it would be great for forged cranks for example, but the
majority of producers cast cranks because it's so much cheaper - fatigue
benefits of superior materials be hanged.
as for chronology, the benefits have been known for a long time - since
the 30's i believe, but knowing about it, being able to produce it, and
/paying/ for it are all completely different things. i don't believe
that an auto industry that will save 6' of copper wire by using the same
bulb for brake lights and turn signals, or not using washers/gaskets on
spark plugs, has the /slightest/ interest in paying extra for vacuum
degassed steels when cheap cast iron crap will do.
|
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Date: 12 Sep 2007 09:14:24
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
[vacuum degassed steel]
> as for chronology, the benefits have been known for a long time - since
> the 30's i believe, but knowing about it, being able to produce it, and
> /paying/ for it are all completely different things. i don't believe
> that an auto industry that will save 6' of copper wire by using the same
> bulb for brake lights and turn signals, or not using washers/gaskets on
> spark plugs, has the /slightest/ interest in paying extra for vacuum
> degassed steels when cheap cast iron crap will do.
An interesting report from *1966*:
<http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=AD0803703 >
"VACUUM-DEGASSED STEELS FROM THE CONSUMER'S VIEWPOINT
Numerous industrial users were asked for their appraisal of
vacuum-degassed steel. Their responses regarding the merits of this
vacuum treatment were varied. ...
Unfortunately, many of the users could not give a meaningful evaluation
because they knew that frequently their suppliers filled orders with
vacuum-degassed steels even though such treatment was not specified."
Sounds like cost wasn't a deal breaker even in 1966.
|
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Date: 12 Sep 2007 19:58:02
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>
> [vacuum degassed steel]
>
>> as for chronology, the benefits have been known for a long time -
>> since the 30's i believe, but knowing about it, being able to produce
>> it, and /paying/ for it are all completely different things. i don't
>> believe that an auto industry that will save 6' of copper wire by
>> using the same bulb for brake lights and turn signals, or not using
>> washers/gaskets on spark plugs, has the /slightest/ interest in paying
>> extra for vacuum degassed steels when cheap cast iron crap will do.
>
> An interesting report from *1966*:
> <http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=AD0803703>
>
>
> "VACUUM-DEGASSED STEELS FROM THE CONSUMER'S VIEWPOINT
>
> Numerous industrial users were asked for their appraisal of
> vacuum-degassed steel. Their responses regarding the merits of this
> vacuum treatment were varied. ...
>
> Unfortunately, many of the users could not give a meaningful evaluation
> because they knew that frequently their suppliers filled orders with
> vacuum-degassed steels even though such treatment was not specified."
>
> Sounds like cost wasn't a deal breaker even in 1966.
dude, you are /so/ freakin' twisted. if they're using it for re-bar,
you can be damned sure they're _not_ going to notice the difference -
other than wasting money of course. if they're using it for elevator
rope wire, you can be sure they will - and it's money well spent.
and you've just contradicted yourself on dates.
|
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Date: 13 Sep 2007 07:20:00
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>
>> [vacuum degassed steel]
>>
>>> as for chronology, the benefits have been known for a long time -
>>> since the 30's i believe, but knowing about it, being able to produce
>>> it, and /paying/ for it are all completely different things. i don't
>>> believe that an auto industry that will save 6' of copper wire by
>>> using the same bulb for brake lights and turn signals, or not using
>>> washers/gaskets on spark plugs, has the /slightest/ interest in
>>> paying extra for vacuum degassed steels when cheap cast iron crap
>>> will do.
>>
>> An interesting report from *1966*:
>> <http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=AD0803703>
>>
>>
>> "VACUUM-DEGASSED STEELS FROM THE CONSUMER'S VIEWPOINT
>>
>> Numerous industrial users were asked for their appraisal of
>> vacuum-degassed steel. Their responses regarding the merits of this
>> vacuum treatment were varied. ...
>>
>> Unfortunately, many of the users could not give a meaningful
>> evaluation because they knew that frequently their suppliers filled
>> orders with vacuum-degassed steels even though such treatment was not
>> specified."
>>
>> Sounds like cost wasn't a deal breaker even in 1966.
>
> dude, you are /so/ freakin' twisted. if they're using it for re-bar,
> you can be damned sure they're _not_ going to notice the difference -
> other than wasting money of course. if they're using it for elevator
> rope wire, you can be sure they will - and it's money well spent.
You missed the point (deliberately?). Cost wasn't an issue in 1966.
>
> and you've just contradicted yourself on dates.
How's that?
|
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Date: 13 Sep 2007 06:15:29
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>
>>> [vacuum degassed steel]
>>>
>>>> as for chronology, the benefits have been known for a long time -
>>>> since the 30's i believe, but knowing about it, being able to
>>>> produce it, and /paying/ for it are all completely different
>>>> things. i don't believe that an auto industry that will save 6' of
>>>> copper wire by using the same bulb for brake lights and turn
>>>> signals, or not using washers/gaskets on spark plugs, has the
>>>> /slightest/ interest in paying extra for vacuum degassed steels when
>>>> cheap cast iron crap will do.
>>>
>>> An interesting report from *1966*:
>>> <http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=AD0803703>
>>>
>>>
>>> "VACUUM-DEGASSED STEELS FROM THE CONSUMER'S VIEWPOINT
>>>
>>> Numerous industrial users were asked for their appraisal of
>>> vacuum-degassed steel. Their responses regarding the merits of this
>>> vacuum treatment were varied. ...
>>>
>>> Unfortunately, many of the users could not give a meaningful
>>> evaluation because they knew that frequently their suppliers filled
>>> orders with vacuum-degassed steels even though such treatment was not
>>> specified."
>>>
>>> Sounds like cost wasn't a deal breaker even in 1966.
>>
>> dude, you are /so/ freakin' twisted. if they're using it for re-bar,
>> you can be damned sure they're _not_ going to notice the difference -
>> other than wasting money of course. if they're using it for elevator
>> rope wire, you can be sure they will - and it's money well spent.
>
> You missed the point (deliberately?). Cost wasn't an issue in 1966.
eh??????????????????? possibly the most bizarre statement i've ever seen.
>
>>
>> and you've just contradicted yourself on dates.
>
> How's that?
|
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Date: 14 Sep 2007 13:11:39
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>>> jim beam wrote:
>>>>
>>>> [vacuum degassed steel]
>>>>
>>>>> as for chronology, the benefits have been known for a long time -
>>>>> since the 30's i believe, but knowing about it, being able to
>>>>> produce it, and /paying/ for it are all completely different
>>>>> things. i don't believe that an auto industry that will save 6' of
>>>>> copper wire by using the same bulb for brake lights and turn
>>>>> signals, or not using washers/gaskets on spark plugs, has the
>>>>> /slightest/ interest in paying extra for vacuum degassed steels
>>>>> when cheap cast iron crap will do.
>>>>
>>>> An interesting report from *1966*:
>>>> <http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=AD0803703>
>>>>
>>>>
>>>> "VACUUM-DEGASSED STEELS FROM THE CONSUMER'S VIEWPOINT
>>>>
>>>> Numerous industrial users were asked for their appraisal of
>>>> vacuum-degassed steel. Their responses regarding the merits of this
>>>> vacuum treatment were varied. ...
>>>>
>>>> Unfortunately, many of the users could not give a meaningful
>>>> evaluation because they knew that frequently their suppliers filled
>>>> orders with vacuum-degassed steels even though such treatment was
>>>> not specified."
>>>>
>>>> Sounds like cost wasn't a deal breaker even in 1966.
>>>
>>> dude, you are /so/ freakin' twisted. if they're using it for re-bar,
>>> you can be damned sure they're _not_ going to notice the difference -
>>> other than wasting money of course. if they're using it for elevator
>>> rope wire, you can be sure they will - and it's money well spent.
>>
>> You missed the point (deliberately?). Cost wasn't an issue in 1966.
>
> eh??????????????????? possibly the most bizarre statement i've ever seen.
For spokes, not rebar.
>>> and you've just contradicted yourself on dates.
>>
>> How's that?
How's that, again?
|
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Date: 12 Sep 2007 09:08:01
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>>> jim beam wrote:
>>>>> Peter Cole wrote:
>>
>>>>>>>> Vacuum degassing was big news in the 50's. It's a cheap bulk
>>>>>>>> process, common as dirt. What else have you got?
>>>>>>>
>>>>>>> it's /cheaper/ than it was, but it's still expensive.
>>>>>>
>>>>>> No, it's not.
>>>>>
>>>>> er, it is actually.
>>>>>
>>>>>
>>>>>>
>>>>>>> and it didn't
>>>>>>> start being used for bike spoke material until the 70's
>>>>>>
>>>>>> Cite, please. It was used in auto sheet metal by that time.
>>>>>
>>>>> not even in the 80's big guy. that's the last time i went through a
>>>>> strip mill and it was either open ingot or con-cast. look at this
>>>>> stuff
>>>>> under a microscope some time and you'll see the evidence for yourself.
>>>>
>>>> Used by the Japanese for auto bodies in the 70's. US by 80's, little
>>>> man. How can this be "expensive" if it's used in massive quantities
>>>> in cars?
>>>
>>> but wasn't! not for bulk sheet. maybe you're thinking of oxygen
>>> lancing?
>>>
>>> http://en.wikipedia.org/wiki/Basic_oxygen_steelmaking
>>
>> No. From that article (did you read it?):
>>
>> "The first basic oxygen steelmaking process was the LD process
>> developed in 1952 by voestalpine AG in Linz, Austria. Some major
>> steelmaking companies in the US did not convert to this process for
>> decades, with the last Bessemer converter still operating commercially
>> until 1968.
>>
>> The LD process replaced both the previously common Siemens-Martin
>> process, also known as the open-hearth process, and the Bessemer
>> process."
>>
>> As you should know, vacuum degassing is not related to the "LD"
>> process which is merely an upgrade to the original Bessemer process,
>> using oxygen instead of air.
>
> not only did i read it, i've done it. and it's the process that
> produces the majority of the material used in bulk product like sheet,
> rod, bar, etc. used today. the product is good enough that you don't
> need to worry too much about additional refining unless you have a
> special use.
OK, so it has nothing to do with "vacuum degassing"?
>
>
>>
>> As for vacuum degassing (your magic process)
>> <http://www.memagazine.org/backissues/membersonly/april98/features/vacuum/vacuum.html>
>>
>>
>> "Vacuum-degassing systems, which are all customized, fall into two
>> categories. The first type, RH recirculating degassers invented by
>> Heraeus-Rheinstahl in Germany, involves inserting two legs, or
>> snorkels, of a vacuum chamber into a ladle of liquid steel. The metal
>> is drawn into the chamber via one snorkel that injects argon to
>> promote turbulence; it is then exposed to the vacuum to remove gases
>> and recirculated back through the other snorkel. The other system, a
>> tank degasser, is a vessel into which the ladle is sent and stirred by
>> the injection of argon. The chamber is depressurized to remove gases,
>> and finally the ladle is removed."
>>
>> As for the timeline:
>>
>> "Cramb noted that automakers' demand for ultralow-carbon sheet steel
>> to make lightweight but durable car panels for more-fuel-efficient
>> cars has been the major factor driving vacuum degassing's growing
>> share of the sheet-steel market in the later 1980s and early 1990s.
>>
>> "One plant has been making over 1.2 million tons of degassed sheet
>> steel to supply the automotive market" out of an annual production of
>> 6 million tons, according to Ron Holmes, a metallurgical engineer and
>> senior process consultant at Kvaerner Metals, a subsidiary of Kvaerner
>> ASA in Oslo, Norway. Kvaerner Metals has designed and installed
>> numerous vacuum-degassing systems for processing sheet steel for
>> automotive end users.
>>
>> "Although this is a relatively new story in the United States, dating
>> from the late 1980s, Japanese steel makers were degassing sheet metal
>> for autos at least 10 years earlier,""
>
>
> ok, first, 10 points for producing an interesting article for once.
Why don't you just stick to the point?
>
> second, if you read further, you'll see that it gets slightly more
> specific about the product this material is used to produce.
Funny, I don't see that.
> this may
> indeed be used in some sheet used in vehicles, but price alone prohibits
> it being used for the majority - it would only make sense for some
> chassis componentry and other fatigued components like suspension and
> engine bolts.
>> "One plant has been making over 1.2 million tons of degassed sheet
>> steel to supply the automotive market" (annual).
Given that the US annual vehicle production is around 15M, just that one
plant would be contributing around 200lb of *sheet* to the average vehicle.
> and even then, not every manufacturer would be
> interested. it would be great for forged cranks for example, but the
> majority of producers cast cranks because it's so much cheaper - fatigue
> benefits of superior materials be hanged.
http://tinyurl.com/ywqhhy
> as for chronology, the benefits have been known for a long time - since
> the 30's i believe, but knowing about it, being able to produce it, and
> /paying/ for it are all completely different things. i don't believe
> that an auto industry that will save 6' of copper wire by using the same
> bulb for brake lights and turn signals, or not using washers/gaskets on
> spark plugs, has the /slightest/ interest in paying extra for vacuum
> degassed steels when cheap cast iron crap will do.
Well, you're entitled to your beliefs, but it seems you are wrong.
As for vacuum degassing being somehow cost prohibitive for bicycle
spokes, consider that even at an extra $100/ton, the change in raw
material costs would be less than a dime for a bike's worth of spokes.
|
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Date: 12 Sep 2007 19:59:39
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
<snip for clarity >
>
> >> "One plant has been making over 1.2 million tons of degassed sheet
> >> steel to supply the automotive market" (annual).
>
> Given that the US annual vehicle production is around 15M, just that one
> plant would be contributing around 200lb of *sheet* to the average vehicle.
and as i said earlier, for a 3,000lb vehicle, it's /clearly/ not being
used for /all/ the material.
>
>
>> and even then, not every manufacturer would be interested. it would
>> be great for forged cranks for example, but the majority of producers
>> cast cranks because it's so much cheaper - fatigue benefits of
>> superior materials be hanged.
>
> http://tinyurl.com/ywqhhy
what part of "Racing Crankshaft" is hard to comprehend as being atypical
when we're talking about using cast iron for cheap crap?
>
>
>> as for chronology, the benefits have been known for a long time -
>> since the 30's i believe, but knowing about it, being able to produce
>> it, and /paying/ for it are all completely different things. i don't
>> believe that an auto industry that will save 6' of copper wire by
>> using the same bulb for brake lights and turn signals, or not using
>> washers/gaskets on spark plugs, has the /slightest/ interest in paying
>> extra for vacuum degassed steels when cheap cast iron crap will do.
>
> Well, you're entitled to your beliefs, but it seems you are wrong.
eh? wrong like trying to bullshit about racing cranks being used in
everyday vehicles is wrong?
>
> As for vacuum degassing being somehow cost prohibitive for bicycle
> spokes, consider that even at an extra $100/ton, the change in raw
> material costs would be less than a dime for a bike's worth of spokes.
er, you need to check out http://www.steelonthenet.com/steel_cost_bof.html
if i'm paying $261.50 per ton for steel, paying an extra 38% to get it
degassed is kind of significant.
|
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Date: 13 Sep 2007 07:27:44
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
> <snip for clarity>
>>
>> >> "One plant has been making over 1.2 million tons of degassed sheet
>> >> steel to supply the automotive market" (annual).
>>
>> Given that the US annual vehicle production is around 15M, just that
>> one plant would be contributing around 200lb of *sheet* to the average
>> vehicle.
>
> and as i said earlier, for a 3,000lb vehicle, it's /clearly/ not being
> used for /all/ the material.
>
>
>>
>>
>>> and even then, not every manufacturer would be interested. it would
>>> be great for forged cranks for example, but the majority of producers
>>> cast cranks because it's so much cheaper - fatigue benefits of
>>> superior materials be hanged.
>>
>> http://tinyurl.com/ywqhhy
>
> what part of "Racing Crankshaft" is hard to comprehend as being atypical
> when we're talking about using cast iron for cheap crap?
>
>
>>
>>
>>> as for chronology, the benefits have been known for a long time -
>>> since the 30's i believe, but knowing about it, being able to produce
>>> it, and /paying/ for it are all completely different things. i don't
>>> believe that an auto industry that will save 6' of copper wire by
>>> using the same bulb for brake lights and turn signals, or not using
>>> washers/gaskets on spark plugs, has the /slightest/ interest in
>>> paying extra for vacuum degassed steels when cheap cast iron crap
>>> will do.
>>
>> Well, you're entitled to your beliefs, but it seems you are wrong.
>
> eh? wrong like trying to bullshit about racing cranks being used in
> everyday vehicles is wrong?
Who said that? All I'm proving with that link is that a complete (65lb)
crankshaft, forged with vacuum degassed steel is only $438, qty 1. How
much do you think the vacuum degassing added to that price?
>
>>
>> As for vacuum degassing being somehow cost prohibitive for bicycle
>> spokes, consider that even at an extra $100/ton, the change in raw
>> material costs would be less than a dime for a bike's worth of spokes.
>
> er, you need to check out http://www.steelonthenet.com/steel_cost_bof.html
>
> if i'm paying $261.50 per ton for steel, paying an extra 38% to get it
> degassed is kind of significant.
Not if you're making spokes, which is the whole point.
All of these examples prove that vacuum degassed steel has been in
common use for a long time and doesn't cost much, contrary to your
assertions. Since this is the crux of your argument about the need for
stress relieving, you need to rethink the matter.
|
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Date: 13 Sep 2007 06:14:17
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>> <snip for clarity>
>>>
>>> >> "One plant has been making over 1.2 million tons of degassed sheet
>>> >> steel to supply the automotive market" (annual).
>>>
>>> Given that the US annual vehicle production is around 15M, just that
>>> one plant would be contributing around 200lb of *sheet* to the
>>> average vehicle.
>>
>> and as i said earlier, for a 3,000lb vehicle, it's /clearly/ not being
>> used for /all/ the material.
>>
>>
>>>
>>>
>>>> and even then, not every manufacturer would be interested. it would
>>>> be great for forged cranks for example, but the majority of
>>>> producers cast cranks because it's so much cheaper - fatigue
>>>> benefits of superior materials be hanged.
>>>
>>> http://tinyurl.com/ywqhhy
>>
>> what part of "Racing Crankshaft" is hard to comprehend as being
>> atypical when we're talking about using cast iron for cheap crap?
>>
>>
>>>
>>>
>>>> as for chronology, the benefits have been known for a long time -
>>>> since the 30's i believe, but knowing about it, being able to
>>>> produce it, and /paying/ for it are all completely different
>>>> things. i don't believe that an auto industry that will save 6' of
>>>> copper wire by using the same bulb for brake lights and turn
>>>> signals, or not using washers/gaskets on spark plugs, has the
>>>> /slightest/ interest in paying extra for vacuum degassed steels when
>>>> cheap cast iron crap will do.
>>>
>>> Well, you're entitled to your beliefs, but it seems you are wrong.
>>
>> eh? wrong like trying to bullshit about racing cranks being used in
>> everyday vehicles is wrong?
>
> Who said that? All I'm proving with that link is that a complete (65lb)
> crankshaft, forged with vacuum degassed steel is only $438, qty 1. How
> much do you think the vacuum degassing added to that price?
er, the majority of domestic crankshafts are cast. /you/ cite one that
isn't in a context of being contrarian. as usual.
>
>>
>>>
>>> As for vacuum degassing being somehow cost prohibitive for bicycle
>>> spokes, consider that even at an extra $100/ton, the change in raw
>>> material costs would be less than a dime for a bike's worth of spokes.
>>
>> er, you need to check out
>> http://www.steelonthenet.com/steel_cost_bof.html
>>
>> if i'm paying $261.50 per ton for steel, paying an extra 38% to get it
>> degassed is kind of significant.
>
> Not if you're making spokes, which is the whole point.
yes if you're making spokes, which is the whole point. materials costs
are something and they need to be managed. processing is another.
>
> All of these examples prove that vacuum degassed steel has been in
> common use for a long time and doesn't cost much, contrary to your
> assertions. Since this is the crux of your argument about the need for
> stress relieving, you need to rethink the matter.
it's been around since the 30's iirc, but it's not been widely used -
partly due to low tonnage, but mainly due to cost. it's not
/prohibitively/ expensive, but if it erodes a manufacturers profit, and
there's no benefit for that application, who is going to use it?
|
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Date: 14 Sep 2007 13:10:23
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>> <snip for clarity>
>>>>
>>>> >> "One plant has been making over 1.2 million tons of degassed sheet
>>>> >> steel to supply the automotive market" (annual).
>>>>
>>>> Given that the US annual vehicle production is around 15M, just that
>>>> one plant would be contributing around 200lb of *sheet* to the
>>>> average vehicle.
>>>
>>> and as i said earlier, for a 3,000lb vehicle, it's /clearly/ not
>>> being used for /all/ the material.
>>>
>>>
>>>>
>>>>
>>>>> and even then, not every manufacturer would be interested. it
>>>>> would be great for forged cranks for example, but the majority of
>>>>> producers cast cranks because it's so much cheaper - fatigue
>>>>> benefits of superior materials be hanged.
>>>>
>>>> http://tinyurl.com/ywqhhy
>>>
>>> what part of "Racing Crankshaft" is hard to comprehend as being
>>> atypical when we're talking about using cast iron for cheap crap?
>>>
>>>
>>>>
>>>>
>>>>> as for chronology, the benefits have been known for a long time -
>>>>> since the 30's i believe, but knowing about it, being able to
>>>>> produce it, and /paying/ for it are all completely different
>>>>> things. i don't believe that an auto industry that will save 6' of
>>>>> copper wire by using the same bulb for brake lights and turn
>>>>> signals, or not using washers/gaskets on spark plugs, has the
>>>>> /slightest/ interest in paying extra for vacuum degassed steels
>>>>> when cheap cast iron crap will do.
>>>>
>>>> Well, you're entitled to your beliefs, but it seems you are wrong.
>>>
>>> eh? wrong like trying to bullshit about racing cranks being used in
>>> everyday vehicles is wrong?
>>
>> Who said that? All I'm proving with that link is that a complete
>> (65lb) crankshaft, forged with vacuum degassed steel is only $438, qty
>> 1. How much do you think the vacuum degassing added to that price?
>
> er, the majority of domestic crankshafts are cast. /you/ cite one that
> isn't in a context of being contrarian. as usual.
No, just looking at the economics.
>>>> As for vacuum degassing being somehow cost prohibitive for bicycle
>>>> spokes, consider that even at an extra $100/ton, the change in raw
>>>> material costs would be less than a dime for a bike's worth of spokes.
>>>
>>> er, you need to check out
>>> http://www.steelonthenet.com/steel_cost_bof.html
>>>
>>> if i'm paying $261.50 per ton for steel, paying an extra 38% to get
>>> it degassed is kind of significant.
>>
>> Not if you're making spokes, which is the whole point.
>
> yes if you're making spokes, which is the whole point. materials costs
> are something and they need to be managed. processing is another.
OK, you're claiming that for a $438/65lb ($6.75/lb) crankshaft, vacuum
degassed steel is economical, but for a $.60/8g spoke ($165/lb) it isn't?
>> All of these examples prove that vacuum degassed steel has been in
>> common use for a long time and doesn't cost much, contrary to your
>> assertions. Since this is the crux of your argument about the need for
>> stress relieving, you need to rethink the matter.
>
> it's been around since the 30's iirc, but it's not been widely used -
> partly due to low tonnage, but mainly due to cost. it's not
> /prohibitively/ expensive, but if it erodes a manufacturers profit, and
> there's no benefit for that application, who is going to use it?
You are the one claiming the benefit (in spokes). It's been around and
widely available since the mid 60's anyway -- used in bulk,
cost-sensitive apps (auto sheet metal) since the 70's at least.
Let's review.
You have claimed that stress relieving of spokes is not necessary since
spoke failures are caused by surface defects, commonly inclusions. The
solution is to use quality spokes like Sapim, who, according to their
website, use vacuum degassed steel. You back up this claim with a hand
drawing of a spoke failing at an inclusion, which you assert is
representative.
You claim that the use of vacuum degassed steels was unlikely until
fairly recently because of cost and availability. The record indicates
that this was not true since at least the mid-60's.
You claim that the use of vacuum degassed steel in spokes is still
prohibitively expensive for some manufacturers. It defies reason that a
manufacturer could afford the alloying elements of stainless and not
afford to degass the steel.
Let's suppose your claim that spokes only fail at inclusions is true,
and that after using defect free material we don't need to stress
relieve. This is because:
1) There aren't any residual stresses to relieve.
2) They don't matter for fatigue life.
Item 1 is false. Metallurgists have agreed with Jobst's model on this
forum (it's archived). I have observed the residual stress first hand by
making a "slitting" experiment -- a technique that is used in industry.
Item 2 is also false. If a spoke is nominally tensioned to 33% of yield,
and the endurance limit is 40% of yield, even a small amount of residual
stress can dramatically shorten the fatigue life. Since Jobst has
reported spoke lifetimes of over 10^8 cycles, his technique must be
reducing residual stresses to a very low level since he must be below
the endurance limit.
|
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Date: 12 Sep 2007 02:54:10
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-12, jim beam <spamvortex@bad.example.net > wrote:
> Peter Cole wrote:
[...]
>> As for vacuum degassing (your magic process)
>> <http://www.memagazine.org/backissues/membersonly/april98/features/vacuum/vacuum.html>
[...]
> ok, first, 10 points for producing an interesting article for once.
>
> second, if you read further, you'll see that it gets slightly more
> specific about the product this material is used to produce. this may
> indeed be used in some sheet used in vehicles, but price alone prohibits
> it being used for the majority - it would only make sense for some
> chassis componentry and other fatigued components like suspension and
> engine bolts.
I thought it said the degassing for cars was not to remove hydrogen for
better cold-worked stuff but a slightly different process, although
based on the same principle, to remove carbon, making this "ultra-low
carbon" stuff for body panels.
I thought the point of that was it was then easier to make into
pressings. But I would have thought it would be rather soft. Perhaps
that doesn't matter though, and perhaps it's the reason why you can ping
car body panels in and out quite easily these days when in the past it
required repeated applications of a lump hammer.
[...]
> as for chronology, the benefits have been known for a long time - since
> the 30's i believe, but knowing about it, being able to produce it, and
> /paying/ for it are all completely different things. i don't believe
> that an auto industry that will save 6' of copper wire by using the same
> bulb for brake lights and turn signals, or not using washers/gaskets on
> spark plugs, has the /slightest/ interest in paying extra for vacuum
> degassed steels when cheap cast iron crap will do.
You add up the cost though. The degassing process might cost a bit but
maybe you can use a bit less steel that way and also produce a lighter
and more fuel-efficient (and therefore competitive-- at least outside
the USA) car.
|
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Date: 12 Sep 2007 05:55:23
From: jim beam
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-12, jim beam <spamvortex@bad.example.net> wrote:
>> Peter Cole wrote:
> [...]
>>> As for vacuum degassing (your magic process)
>>> <http://www.memagazine.org/backissues/membersonly/april98/features/vacuum/vacuum.html>
> [...]
>> ok, first, 10 points for producing an interesting article for once.
>>
>> second, if you read further, you'll see that it gets slightly more
>> specific about the product this material is used to produce. this may
>> indeed be used in some sheet used in vehicles, but price alone prohibits
>> it being used for the majority - it would only make sense for some
>> chassis componentry and other fatigued components like suspension and
>> engine bolts.
>
> I thought it said the degassing for cars was not to remove hydrogen for
> better cold-worked stuff but a slightly different process, although
> based on the same principle, to remove carbon, making this "ultra-low
> carbon" stuff for body panels.
good point - and oxygen lancing is the process that removes the carbon.
>
> I thought the point of that was it was then easier to make into
> pressings. But I would have thought it would be rather soft. Perhaps
> that doesn't matter though, and perhaps it's the reason why you can ping
> car body panels in and out quite easily these days when in the past it
> required repeated applications of a lump hammer.
softer is definitely more formable, but body panel sheet is cold worked
and thus not fully soft like it would be if it were annealed.
>
> [...]
>> as for chronology, the benefits have been known for a long time - since
>> the 30's i believe, but knowing about it, being able to produce it, and
>> /paying/ for it are all completely different things. i don't believe
>> that an auto industry that will save 6' of copper wire by using the same
>> bulb for brake lights and turn signals, or not using washers/gaskets on
>> spark plugs, has the /slightest/ interest in paying extra for vacuum
>> degassed steels when cheap cast iron crap will do.
>
> You add up the cost though. The degassing process might cost a bit but
> maybe you can use a bit less steel that way and also produce a lighter
> and more fuel-efficient (and therefore competitive-- at least outside
> the USA) car.
you're right, but i don't think domestic producers have the slightest
interest in fuel efficiency. and all the so-called "safety" features
built into cars today add to the weight of vehicles significantly.
weight is directly contradictory to fuel efficiency. and making sure a
car can withstand a 30mph side impact with a semi is somewhat pointless
given that the occupants still impact the interior of the vehicle with
pretty much zero deceleration room whether the shell deforms or not.
regarding cost of materials, yes, there comes a point where reducing
material pays back, but for cast iron cranks, the cost savings are not
just material, but processing. and that is substantial.
|
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Date: 11 Sep 2007 07:04:14
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>>>>> Everybody knows this stuff. Lots of us have had nicked spokes
>>>>>> break in mid-span. So what? Stress + flaw = failure. Film at 11.
>>>>>
>>>>> eh? surface nicks are /not/ inclusions!!!
>>>>
>>>> Both are defects (obviously).
>>>
>>> wriggle, squirm. a nick is not an inclusion. period.
>>
>> No kidding, but they're both defects, flaws, stress concentrators --
>> take your pick -- or perhaps you'd like to explain why an "inclusion"
>> is a special form of defect from a fatigue POV?
>
> sure - if surface defects are controlled and kept below a certain
> feature size, fatigue can be substantially mitigated.
"Surface defects" -- of course those would include nicks.
> but in searching for an explanation of why even mirror polished
> materials still initiate fatigue at the surface, it was found that
> fatigue was initiating at inclusions where they interrupted the surface.
> removing the inclusions removed these initiators and fatigue life was
> found to be improved again.
Of course -- inclusions are defects. So are persistent slip bands.
<http://www.key-to-steel.com/Articles/Art162.htm >
"An overpowering structural consideration in fatigue is the fact that
fatigue cracks usually are initiated at a free surface. In those rare
instances where fatigue cracks initiate in the interior there is always
an interface involved, such as the interface of a carburized surface
layer and the base metal."
"An important structural feature, which appears to be unique to fatigue
deformation, is the formation on the surface of ridges and grooves
called slip-band extrusions and slip-band intrusions. Extremely careful
metallography on tapered sections through the surface of the specimen
has shown that fatigue cracks initiate at intrusions and extrusions."
|
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Date: 11 Sep 2007 06:35:51
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>>> jim beam wrote:
>>>>> Peter Cole wrote:
>>>>>> I performed the experiment Luns suggested on the above thread and
>>>>>> posted my results:
>>>>>>
>>>>>> http://tinyurl.com/356ru7
>>>>>>
>>>>>> I think that was an "observed fact". Yours?
>>>>>
>>>>> and your explanation of why spoke fatigue initiates at a region of
>>>>> little or zero residual stress is???
>>>>>
>>>>> http://www.flickr.com/photos/38636024@N00/1346747861/
>>>>
>>>> Who says there's little or no residual stress at the surface? That's
>>>> not what I found when I did the experiment.
>>>
>>> but you did! you obviously didn't understand what you were observing.
>>
>> Why don't you post your "explanation" then?
>
> you're evidencing an adjustment in equilibrium if there's residual
> stress present.
Of course you're "adjusting equilibrium", at least in the sense that the
spoke reaches a new equilibrium -- otherwise, according to Newton, it
would keep moving.
> but it does not evidence residual stress at the surface!
Upon re-reading I see I didn't really post enough information to allow
you to reach that conclusion.
The spoke movement didn't start until I was close to 90% through. I only
stopped when the remaining section became too thin to support (the
nearly vertical) weight.
If you examine a typical residual stress profile (cross section) like
the one I posted, and consider the predicted change in forces as a slit
is made, you'll understand that I saw exactly what I should have seen.
It's unambiguous.
>>>>> eh? surface nicks are /not/ inclusions!!!
>>>>
>>>> Both are defects (obviously).
>>>
>>> wriggle, squirm. a nick is not an inclusion. period.
>>
>> No kidding, but they're both defects, flaws, stress concentrators --
>> take your pick -- or perhaps you'd like to explain why an "inclusion"
>> is a special form of defect from a fatigue POV?
>
> sure - if surface defects are controlled and kept below a certain
> feature size, fatigue can be substantially mitigated.
>
> http://www.flickr.com/photos/38636024@N00/340348242/
>
> [that's not an explanation, just an illustration.]
>
> but in searching for an explanation of why even mirror polished
> materials still initiate fatigue at the surface, it was found that
> fatigue was initiating at inclusions where they interrupted the surface.
> removing the inclusions removed these initiators and fatigue life was
> found to be improved again.
>
>
>>
>>
>>>
>>>>
>>>>>
>>>>>>
>>>>>>>
>>>>>>> that's why spoke manufacturers spend lots of money on expensive
>>>>>>> vacuum degassed materials. if cheap materials could offer
>>>>>>> superior fatigue life by way of simple stress relief, you'd
>>>>>>> better believe they'd be used.
>>>>>>
>>>>>> Vacuum degassing was big news in the 50's. It's a cheap bulk
>>>>>> process, common as dirt. What else have you got?
>>>>>
>>>>> it's /cheaper/ than it was, but it's still expensive.
>>>>
>>>> No, it's not.
>>>
>>> er, it is actually.
>>>
>>>
>>>>
>>>>> and it didn't
>>>>> start being used for bike spoke material until the 70's
>>>>
>>>> Cite, please. It was used in auto sheet metal by that time.
>>>
>>> not even in the 80's big guy. that's the last time i went through a
>>> strip mill and it was either open ingot or con-cast. look at this stuff
>>> under a microscope some time and you'll see the evidence for yourself.
>>
>> Used by the Japanese for auto bodies in the 70's. US by 80's, little
>> man. How can this be "expensive" if it's used in massive quantities in
>> cars?
>
> but wasn't! not for bulk sheet. maybe you're thinking of oxygen lancing?
>
> http://en.wikipedia.org/wiki/Basic_oxygen_steelmaking
|
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Date: 10 Sep 2007 08:58:04
From: Bill Sornson
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> Used by the Japanese for auto bodies in the 70's. US by 80's, little
> man. How can this be "expensive" if it's used in massive quantities
> in cars?
TRIM!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
|
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Date: 10 Sep 2007 21:30:22
From: A Muzi
Subject: Re: Yet another broken spoke
|
> Peter Cole wrote:
>> Used by the Japanese for auto bodies in the 70's. US by 80's, little
>> man. How can this be "expensive" if it's used in massive quantities
>> in cars?
Bill Sornson wrote:
> TRIM!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Family newsgroup, buddy
(or do kids still call it that??)
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
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Date: 08 Sep 2007 21:02:52
From:
Subject: Re: Yet another broken spoke
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In rec.bicycles.tech Peter Cole writes:
>> truth is, outside of the lab and in carefully controlled
>> environments, fatigue is *always* observed to initiate at surface
>> defects. these can be from processing, corrosion, or even
>> inclusions within the material. addressing each of these is
>> observed to directly affect fatigue life. among these, electron
>> microscopy shows inclusion content to be a significant fatigue
>> initiator. removing inclusions is _proven_ to extend fatigue life
>> considerably.
> Everybody knows this stuff. Lots of us have had nicked spokes break
> in mid-span. So what? Stress + flaw = failure. Film at 11.
>> that's why spoke manufacturers spend lots of money on expensive
>> vacuum degassed materials. if cheap materials could offer superior
>> fatigue life by way of simple stress relief, you'd better believe
>> they'd be used.
> Vacuum degassing was big news in the 50's. It's a cheap bulk
> process, common as dirt. What else have you got?
Let me add that DT does not make its spoke wire which is made in
Sweden. DT cannot stress relieve their spokes for you because that
must be done after wheel tensioning. Manufacturers of spokes
anticipate spoke yielding in wheel building and for that reason make
elbows with slightly obtuse angles. Still we hear of riders who break
spokes, some of which are from reputable sources. This is not from
lack of vacuum degassing or cheap materials.
Jobst Brandt
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Date: 09 Sep 2007 06:49:48
From: jim beam
Subject: Re: Yet another broken spoke
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jobst.brandt@stanfordalumni.org wrote:
> In rec.bicycles.tech Peter Cole writes:
>
>>> truth is, outside of the lab and in carefully controlled
>>> environments, fatigue is *always* observed to initiate at surface
>>> defects. these can be from processing, corrosion, or even
>>> inclusions within the material. addressing each of these is
>>> observed to directly affect fatigue life. among these, electron
>>> microscopy shows inclusion content to be a significant fatigue
>>> initiator. removing inclusions is _proven_ to extend fatigue life
>>> considerably.
>
>> Everybody knows this stuff. Lots of us have had nicked spokes break
>> in mid-span. So what? Stress + flaw = failure. Film at 11.
>
>>> that's why spoke manufacturers spend lots of money on expensive
>>> vacuum degassed materials. if cheap materials could offer superior
>>> fatigue life by way of simple stress relief, you'd better believe
>>> they'd be used.
>
>> Vacuum degassing was big news in the 50's. It's a cheap bulk
>> process, common as dirt. What else have you got?
>
> Let me add that DT does not make its spoke wire which is made in
> Sweden. DT cannot stress relieve their spokes for you because that
> must be done after wheel tensioning. Manufacturers of spokes
> anticipate spoke yielding in wheel building and for that reason make
> elbows with slightly obtuse angles.
no, the angle is set in anticipation of hub geometry, not deformation by
the wheelbuilder. indeed, sapim specifically advise /not/ bending their
spokes.
http://www.flickr.com/photos/38636024@N00/327722444/
basic geometry gives the spoke exit angle at ~95 degrees - exactly what
spoke manufacturers use.
> Still we hear of riders who break
> spokes, some of which are from reputable sources. This is not from
> lack of vacuum degassing or cheap materials.
>
and cheapo chinese spokes break in a few hundred miles. quality spokes
with decent materials, many thousands. /that/ is the effect if
materials and manufacture, not "stress relief".
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Date: 09 Sep 2007 12:09:24
From: Jambo
Subject: Re: Yet another broken spoke
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"jim beam" <spamvortex@bad.example.net > wrote in message
news:RdSdnRkOeJZhZH7bnZ2dnUVZ_gqdnZ2d@speakeasy.net...
>
> and cheapo chinese spokes break in a few hundred miles. quality spokes
> with decent materials, many thousands. /that/ is the effect if
> materials and manufacture, not "stress relief".
SO now you can't even understand the fact that material nature and stress
loadings act IN COMBINATION, and separating the two is just FUCKTARDY!
You are too much sometimes, dumbass!
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Date: 08 Sep 2007 13:53:13
From: Jambo
Subject: Re: Yet another broken spoke
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"jim beam" <spamvortex@bad.example.net > wrote in message
news:mrydnTinlvjBM3_bnZ2dnUVZ_t2inZ2d@speakeasy.net...
> Ben C wrote:
>
> only parts of it. read this from luns tee:
> http://groups.google.com/group/rec.bicycles.tech/msg/af080b93a59cca03
>
> most notably:
> "For a more severely bent wire, the yielded layers extend deeper,
> and the residual stress pattern becomes more like:
>
> cccTCttt "
>
> so here's the problem - that [simplified but useful] depiction shows where
> the residual stress profiles would be. if residual stress were causing
> fatigue, we would observe fatigue initiating at a "T" point. instead, we
> observe it initiating at /both/ "c"'s and "t"'s.
As if you understand it - take someone else's idea and run with it, eh?
Because it's just more ammunition to get JB.
> "engineers" can argue all they want about what they think should be
> happening, but if observed facts tell a different story, it's just so much
> hot air.
But you're full of hot air - you don't even understand the mechanisms, and
yet you bleat like you're an expert! How funny!
> truth is, outside of the lab and in carefully controlled environments,
> fatigue is *always* observed to initiate at surface defects.
Bullshit again. A simple Google of aircraft component failures proves this
is not so! Don't you ever get embarrassed by your stupidity?
> these can be from processing, corrosion, or even inclusions within the
> material. addressing each of these is observed to directly affect fatigue
> life.
> among these, electron microscopy shows inclusion content to be a
> significant fatigue initiator. removing inclusions is _proven_ to extend
> fatigue life considerably.
Wow, well cut and pasted from an introductory chapter of some publication
(wikipedia, maybe? the poor [stupid] man's reference?)
> that's why spoke manufacturers spend lots of money on expensive vacuum
> degassed materials. if cheap materials could offer superior fatigue life
> by way of simple stress relief, you'd better believe they'd be used.
AH, sometimes it's just not worth the stink of your crap...
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Date: 08 Sep 2007 11:10:20
From: jim beam
Subject: Re: Yet another broken spoke
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Jambo wrote:
> "jim beam" <spamvortex@bad.example.net> wrote in message
> news:mrydnTinlvjBM3_bnZ2dnUVZ_t2inZ2d@speakeasy.net...
>> Ben C wrote:
>>
>> only parts of it. read this from luns tee:
>> http://groups.google.com/group/rec.bicycles.tech/msg/af080b93a59cca03
>>
>> most notably:
>> "For a more severely bent wire, the yielded layers extend deeper,
>> and the residual stress pattern becomes more like:
>>
>> cccTCttt "
>>
>> so here's the problem - that [simplified but useful] depiction shows where
>> the residual stress profiles would be. if residual stress were causing
>> fatigue, we would observe fatigue initiating at a "T" point. instead, we
>> observe it initiating at /both/ "c"'s and "t"'s.
>
> As if you understand it - take someone else's idea and run with it, eh?
> Because it's just more ammunition to get JB.
so, are you going to set me straight mr. modulus?
>
>> "engineers" can argue all they want about what they think should be
>> happening, but if observed facts tell a different story, it's just so much
>> hot air.
>
> But you're full of hot air - you don't even understand the mechanisms, and
> yet you bleat like you're an expert! How funny!
no sense of irony then?
>
>
>> truth is, outside of the lab and in carefully controlled environments,
>> fatigue is *always* observed to initiate at surface defects.
>
> Bullshit again. A simple Google of aircraft component failures proves this
> is not so! Don't you ever get embarrassed by your stupidity?
hey, moron, i /have/ done failure analysis - and you hardly /ever/ find
fatigue that has not started at some form of surface defect.
>
>> these can be from processing, corrosion, or even inclusions within the
>> material. addressing each of these is observed to directly affect fatigue
>> life.
>> among these, electron microscopy shows inclusion content to be a
>> significant fatigue initiator. removing inclusions is _proven_ to extend
>> fatigue life considerably.
>
> Wow, well cut and pasted from an introductory chapter of some publication
> (wikipedia, maybe? the poor [stupid] man's reference?)
do you even know what an inclusion is?
>
>> that's why spoke manufacturers spend lots of money on expensive vacuum
>> degassed materials. if cheap materials could offer superior fatigue life
>> by way of simple stress relief, you'd better believe they'd be used.
>
> AH, sometimes it's just not worth the stink of your crap...
so fuck off then! geeze, what a moron.
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Date: 09 Sep 2007 12:00:33
From: Jambo
Subject: Re: Yet another broken spoke
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"jim beam" <spamvortex@bad.example.net > wrote in message
news:Z_udnacG_IsQeH_bnZ2dnUVZ_tmhnZ2d@speakeasy.net...
> Jambo wrote:
>>
>> As if you understand it - take someone else's idea and run with it, eh?
>> Because it's just more ammunition to get JB.
>
> so, are you going to set me straight mr. modulus?
Yeah. Specific modulus is NOT the same as Young's modulus. Got that yet?
>
>>
>>> "engineers" can argue all they want about what they think should be
>>> happening, but if observed facts tell a different story, it's just so
>>> much hot air.
>>
>> But you're full of hot air - you don't even understand the mechanisms,
>> and yet you bleat like you're an expert! How funny!
>
> no sense of irony then?
HAHAHAHA. At least you can laugh at yourself!
>>
>>> truth is, outside of the lab and in carefully controlled environments,
>>> fatigue is *always* observed to initiate at surface defects.
>>
>> Bullshit again. A simple Google of aircraft component failures proves
>> this is not so! Don't you ever get embarrassed by your stupidity?
>
> hey, moron, i /have/ done failure analysis - and you hardly /ever/ find
> fatigue that has not started at some form of surface defect.
So now it's "hardly ever", instead of "always". Good job, mr goalpost
mover.
Anyway, reading Pop Science does not constitute failure analysis. Try
mixing it with the industry boys for a change, you might learn something.
>>> these can be from processing, corrosion, or even inclusions within the
>>> material. addressing each of these is observed to directly affect
>>> fatigue life.
>>> among these, electron microscopy shows inclusion content to be a
>>> significant fatigue initiator. removing inclusions is _proven_ to
>>> extend fatigue life considerably.
>>
>> Wow, well cut and pasted from an introductory chapter of some publication
>> (wikipedia, maybe? the poor [stupid] man's reference?)
>
> do you even know what an inclusion is?
Yes, inclusion is when you mix fucktards with normal people, exactly what
you are in this ng.
>>> that's why spoke manufacturers spend lots of money on expensive vacuum
>>> degassed materials. if cheap materials could offer superior fatigue
>>> life by way of simple stress relief, you'd better believe they'd be
>>> used.
>>
>> AH, sometimes it's just not worth the stink of your crap...
>
> so fuck off then! geeze, what a moron.
Nah, you don't get off that easy, fucktard liar!
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Date: 07 Sep 2007 18:56:50
From: jim beam
Subject: Re: Yet another broken spoke
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jobst.brandt@stanfordalumni.org wrote:
> Ben C? writes:
>
>>> It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
>>> good job. Apparently it didn't stick. I can see why Jobst no longer
>>> bothers to respond.
>
> http://tinyurl.com/29v4u2
>
>> OK I have a question.
>
>> jb i have ignored residual stress as a factor in these failures
>> jb because the majority of the fractures i've examined initiate on
>> jb the /inside/ of the spoke elbow bend, not the outside [although i
>> jb have examples of each]. residual stress in this location is
>> jb compressive so i'm just looking at the external [+cyclic] load.
>
>> MP The inside of the spoke elbow will have TENSILE residual stress,
>> MP not compressive, because of the elastic springback after
>> MP bending. See below. That 0.5 Sy number is for a beam; I'm too
>> MP lazy to derive the number for a circular cross section right now.
>
>> MP Since that location has tensile residual stress, tensile applied
>> MP mean stress from the spoke tension and bending,
>
>> Is the _applied_ stress on the inside of the elbow from spoke
>> tension and bending really tensile?
>
> As I mentioned, don't fly your kite on every breeze that comes along,
> especially those sent aloft by jb.
as opposed to red herrings by JB?
> The elbow of a spoke is the last
> operation in spoke manufacture and it is accomplished by extending the
> head end of the spoke an appropriate length from a collet as a blunt
> piston goes by to bend it just enough to make an obtuse angle.
fantastic. spokes get bent!
>
>> I don't understand that. I thought when you bent a wire you got tensile
>> stress on the outside of the bend and compressive on the inside?
>
> These loads tend to open the elbow angle so that causes tensile
> stress.
we make progress!!!
> As Mike mentioned above, springback makes the stress reverse
> from that during forming. I spent a few exchanges on that issue at
> the time. You could also find them. When you bend a spoke it takes a
> set only after you exceed yield stress in the extreme "fibers" of the
> skin of the spoke. The farther you bend, the deeper the yield stress
> reaches.
and yet, we don't observe fatigue to nucleate at the regions where high
residual stress are... how inconvenient.
>
> For instance, a thin wire will not easily take a bend because it must
> be bent severely to go beyond yield. That's why we use braided cables
> made of fine strands that do not reach yield in the bends encountered
> in curves to reach the derailleur or brake to which it is attached.
red herring.
> In addition, there is no length change in these being helically wound
> cables, all of whose strands pass through the inside and outside of
> each curve (equal path length).
still red herring.
>
> Thus, the core "fibers" of a spoke never go to yield (being thin
> wires) and want to spring back while the outer "fibers" yields and
> wants to stay bent. This causes springback when bending a wire.
absolutely not - residual stress does NOT cause or evidence springback.
springback is simply elasticity and relaxation of load. /relaxation/
causes residual stress - it's not present when the material starts to
spring back. - it's all /applied/ stress.
> The
> reason it doesn't spring all the way back to straight is that the
> outer "fibers" resist,
eh? it doesn't return to straight because it's yielded!!!!
> having taken a new shape.
yes, "yielding"!!!
> This resistance is
> residual stress which appears as tension on the inside of the bend and
> compression on the outside.
no. see above.
>
> You'll find that jb learned about this on this forum just as he
> learned about fretting damage to bearings while fighting it all the
> way, denouncing every explanation with ridicule.
eh? would you be somehow "misremembering" our little episode on headset
bearings where you said they don't brinell? and "forgetting" that i,
fogel, and subsequently "chas" all proved the opposite?
>
>> I know that the residual stress, after it springs back, is tensile
>> on the inside.
>
> That's the one that counts and adds to the tensile and working load
> stress of a spoke. That is why spokes need stress relieving after the
> wheel is tensioned.
unproven suppositional rubbish. the process of "stress relief" simply
beds spokes in so they don't go slack in use. and that in turn can help
with fatigue. you neither invented it nor have proved any efficacy
outside of the above. and you certainly haven't managed to
differentiate from the effects of using materials /formulated and
proven/ to be more fatigue resistant.
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Date: 08 Sep 2007 04:22:57
From: Ben C
Subject: Re: Yet another broken spoke
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On 2007-09-08, jim beam <spamvortex@bad.example.net > wrote:
> jobst.brandt@stanfordalumni.org wrote:
[...]
>> As I mentioned, don't fly your kite on every breeze that comes along,
>> especially those sent aloft by jb.
>
> as opposed to red herrings by JB?
Please both of you calm down. I'm not about to fly any kites OR swallow
any herrings. You are both much better at explaining things when you
aren't blinded by paranoia or rage respectively.
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Date: 08 Sep 2007 07:24:10
From: jim beam
Subject: Re: Yet another broken spoke
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Ben C wrote:
> On 2007-09-08, jim beam <spamvortex@bad.example.net> wrote:
>> jobst.brandt@stanfordalumni.org wrote:
> [...]
>>> As I mentioned, don't fly your kite on every breeze that comes along,
>>> especially those sent aloft by jb.
>> as opposed to red herrings by JB?
>
> Please both of you calm down. I'm not about to fly any kites OR swallow
> any herrings. You are both much better at explaining things when you
> aren't blinded by paranoia or rage respectively.
so what's the question?
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Date: 08 Sep 2007 13:53:47
From: Jambo
Subject: Re: Yet another broken spoke
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"jim beam" <spamvortex@bad.example.net > wrote in message
news:J5ydnYzRCbQWLX_bnZ2dnUVZ_hCdnZ2d@speakeasy.net...
> Ben C wrote:
>> On 2007-09-08, jim beam <spamvortex@bad.example.net> wrote:
>>> jobst.brandt@stanfordalumni.org wrote:
>> [...]
>>>> As I mentioned, don't fly your kite on every breeze that comes along,
>>>> especially those sent aloft by jb.
>>> as opposed to red herrings by JB?
>>
>> Please both of you calm down. I'm not about to fly any kites OR swallow
>> any herrings. You are both much better at explaining things when you
>> aren't blinded by paranoia or rage respectively.
>
> so what's the question?
Why are you such a hallucinating moron?
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Date: 08 Sep 2007 11:05:50
From: jim beam
Subject: Re: Yet another broken spoke
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Jambo wrote:
> "jim beam" <spamvortex@bad.example.net> wrote in message
> news:J5ydnYzRCbQWLX_bnZ2dnUVZ_hCdnZ2d@speakeasy.net...
>> Ben C wrote:
>>> On 2007-09-08, jim beam <spamvortex@bad.example.net> wrote:
>>>> jobst.brandt@stanfordalumni.org wrote:
>>> [...]
>>>>> As I mentioned, don't fly your kite on every breeze that comes along,
>>>>> especially those sent aloft by jb.
>>>> as opposed to red herrings by JB?
>>> Please both of you calm down. I'm not about to fly any kites OR swallow
>>> any herrings. You are both much better at explaining things when you
>>> aren't blinded by paranoia or rage respectively.
>> so what's the question?
>
> Why are you such a hallucinating moron?
>
>
are you missing your meds?
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Date: 09 Sep 2007 11:57:05
From: Jambo
Subject: Re: Yet another broken spoke
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"jim beam" <spamvortex@bad.example.net > wrote in message
news:R4WdnRQ2sLrieX_bnZ2dnUVZ_sbinZ2d@speakeasy.net...
> Jambo wrote:
>> Why are you such a hallucinating moron?
>>
>>
>
> are you missing your meds?
You didn't answer the question. Let me re-phrase:
Why are you such a delusional liar?
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Date: 08 Sep 2007 11:48:29
From: Ben C
Subject: Re: Yet another broken spoke
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On 2007-09-08, jim beam <spamvortex@bad.example.net > wrote:
> Ben C wrote:
>> On 2007-09-08, jim beam <spamvortex@bad.example.net> wrote:
>>> jobst.brandt@stanfordalumni.org wrote:
>> [...]
>>>> As I mentioned, don't fly your kite on every breeze that comes along,
>>>> especially those sent aloft by jb.
>>> as opposed to red herrings by JB?
>>
>> Please both of you calm down. I'm not about to fly any kites OR swallow
>> any herrings. You are both much better at explaining things when you
>> aren't blinded by paranoia or rage respectively.
>
> so what's the question?
See the other thread, which you already have done. Thank you.
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Date: 07 Sep 2007 15:08:29
From:
Subject: Re: Yet another broken spoke
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On Fri, 07 Sep 2007 15:30:08 -0500, Ben C <spamspam@spam.eggs > wrote:
>On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>[...]
>> It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
>> good job. Apparently it didn't stick. I can see why Jobst no longer
>> bothers to respond.
>>
>> http://tinyurl.com/29v4u2
>
>OK I have a question.
>
>jim beam> i have ignored residual stress as a factor in these failures
>jim beam> because the majority of the fractures i've examined initiate
>jim beam> on the /inside/ of the spoke elbow bend, not the outside
>jim beam> [although i have examples of each]. residual stress in this
>jim beam> location is compressive so i'm just looking at the external
>jim beam> [+cyclic] load.
>
>Mike Prime> The inside of the spoke elbow will have TENSILE residual
>Mike Prime> stress, not compressive, because of the elastic springback
>Mike Prime> after bending. See below. That 0.5 Sy number is for a beam;
>Mike Prime> I'm too lazy to derive the number for a circular cross
>Mike Prime> section right now.
>
>Mike Prime> Since that location has tensile residual stress, tensile
>Mike Prime> applied mean stress from the spoke tension and bending,
> ^^^^^^^
>
>Is the _applied_ stress on the inside of the elbow from spoke tension
>and bending really tensile?
>
>I don't understand that. I thought when you bent a wire you got tensile
>stress on the outside of the bend and compressive on the inside?
>
>I know that the residual stress, after it springs back, is tensile on
>the inside.
Dear Ben,
Possibly things change from bending to pulling?
That is, if you clamp a spoke in a vise and push it sideways with your
hand, you get the tensile stress on the outside of the curve and the
compressive on the inside of the curve when the metal yields.
If you then pull hard enough on the end of the bent wire, you start to
change the inside curve from compressive, to neutral, to tensile.
Just to complicate things, the bend itself narrows--check a spoke
elbow with a micrometer.
For such reliable and apparently simple things, wire-spoke wheels are
awfully tricky.
Right now, I'm getting ready for some high-tech spoke-tension testing
of helpless front wheels lashed into my Mark II testing rig:
http://i9.tinypic.com/4p97ur7.jpg
SSTW has reminded me that the spokes in the Mark I test failed to
behave as expected and predicted. Putting up a picture of the new and
improved test rig will goad me to go through the tedious business of
measuring and re-measuring spoke tension on umpteen spokes on several
wheels.
I suspect that the stupid spokes on real wheels with inflated tires
will stubbornly refuse to lose tension on only the bottom spokes,
defying the predictions of theory and single-spoke rolling tests.
If so, I'll wonder if the expected less-than-even tension or the
cross-3 lacing is the cause.
Cheers,
Carl Fogel
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Date: 07 Sep 2007 14:47:54
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-07, Peter Cole <peter_cole@comcast.net > wrote:
[...]
> It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
> good job. Apparently it didn't stick. I can see why Jobst no longer
> bothers to respond.
>
> http://tinyurl.com/29v4u2
Thanks for the link, that's an interesting thread. Before my time.
How much more civilized everyone was back then! I might as well just
read the archives and not bother with new RBT.
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Date: 07 Sep 2007 18:55:28
From: Peter Cole
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
> [...]
>> It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
>> good job. Apparently it didn't stick. I can see why Jobst no longer
>> bothers to respond.
>>
>> http://tinyurl.com/29v4u2
>
> Thanks for the link, that's an interesting thread. Before my time.
>
> How much more civilized everyone was back then!
Unfortunately, incivility seems to drive the civil away. Perhaps that's
the motive.
> I might as well just
> read the archives and not bother with new RBT.
There's a lot to learn in many NG archives, I often get info there that
I can't find with a web search -- on all kinds of topics. The signal to
noise ratio is tough, ours has declined a lot.
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Date: 07 Sep 2007 18:29:24
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> Ben C wrote:
>> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>> [...]
>>> It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
>>> good job. Apparently it didn't stick. I can see why Jobst no longer
>>> bothers to respond.
>>>
>>> http://tinyurl.com/29v4u2
>>
>> Thanks for the link, that's an interesting thread. Before my time.
>>
>> How much more civilized everyone was back then!
>
> Unfortunately, incivility seems to drive the civil away. Perhaps that's
> the motive.
>
>> I might as well just
>> read the archives and not bother with new RBT.
>
> There's a lot to learn in many NG archives, I often get info there that
> I can't find with a web search -- on all kinds of topics.
and yet, you seem to absorb so little!
> The signal to
> noise ratio is tough, ours has declined a lot.
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Date: 08 Sep 2007 10:10:29
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> Ben C wrote:
>>> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>>> [...]
>>>> It was over 4 years ago. I thought Mike Prime (a metallurgist) did a
>>>> good job. Apparently it didn't stick. I can see why Jobst no longer
>>>> bothers to respond.
>>>>
>>>> http://tinyurl.com/29v4u2
>>>
>>> Thanks for the link, that's an interesting thread. Before my time.
>>>
>>> How much more civilized everyone was back then!
>>
>> Unfortunately, incivility seems to drive the civil away. Perhaps
>> that's the motive.
>>
>>> I might as well just
>>> read the archives and not bother with new RBT.
>>
>> There's a lot to learn in many NG archives, I often get info there
>> that I can't find with a web search -- on all kinds of topics.
>
> and yet, you seem to absorb so little!
I think the evidence (for who is not absorbing) is there for anyone who
wishes to take the trouble to find it. It's all in the archives.
|
| | | | | | | | | | | | | | | | | | | | | | | | |
Date: 08 Sep 2007 07:44:24
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> Ben C wrote:
>>>> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>>>> [...]
>>>>> It was over 4 years ago. I thought Mike Prime (a metallurgist) did
>>>>> a good job. Apparently it didn't stick. I can see why Jobst no
>>>>> longer bothers to respond.
>>>>>
>>>>> http://tinyurl.com/29v4u2
>>>>
>>>> Thanks for the link, that's an interesting thread. Before my time.
>>>>
>>>> How much more civilized everyone was back then!
>>>
>>> Unfortunately, incivility seems to drive the civil away. Perhaps
>>> that's the motive.
>>>
>>>> I might as well just
>>>> read the archives and not bother with new RBT.
>>>
>>> There's a lot to learn in many NG archives, I often get info there
>>> that I can't find with a web search -- on all kinds of topics.
>>
>> and yet, you seem to absorb so little!
>
> I think the evidence (for who is not absorbing) is there for anyone who
> wishes to take the trouble to find it. It's all in the archives.
eh? you dig back through /four years/ of crap and you fuck up simple
things like elasticity, plasticity, etc? that's rich!
btw, why are posting on a saturday? do you get paid on the weekends?
|
| | | | | | | | | | | | | | | | | | | | | | | | | |
Date: 08 Sep 2007 14:28:25
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>>> Ben C wrote:
>>>>> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>>>>> [...]
>>>>>> It was over 4 years ago. I thought Mike Prime (a metallurgist) did
>>>>>> a good job. Apparently it didn't stick. I can see why Jobst no
>>>>>> longer bothers to respond.
>>>>>>
>>>>>> http://tinyurl.com/29v4u2
>>>>>
>>>>> Thanks for the link, that's an interesting thread. Before my time.
>>>>>
>>>>> How much more civilized everyone was back then!
>>>>
>>>> Unfortunately, incivility seems to drive the civil away. Perhaps
>>>> that's the motive.
>>>>
>>>>> I might as well just
>>>>> read the archives and not bother with new RBT.
>>>>
>>>> There's a lot to learn in many NG archives, I often get info there
>>>> that I can't find with a web search -- on all kinds of topics.
>>>
>>> and yet, you seem to absorb so little!
>>
>> I think the evidence (for who is not absorbing) is there for anyone
>> who wishes to take the trouble to find it. It's all in the archives.
>
> eh? you dig back through /four years/ of crap and you fuck up simple
> things like elasticity, plasticity, etc? that's rich!
>
> btw, why are posting on a saturday? do you get paid on the weekends?
Some things are difficult to put a price on.
|
| | | | | | | | | | | | | | | | | | | | | | | | | | |
Date: 09 Sep 2007 07:59:00
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>> Peter Cole wrote:
>>>>> Ben C wrote:
>>>>>> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>>>>>> [...]
>>>>>>> It was over 4 years ago. I thought Mike Prime (a metallurgist)
>>>>>>> did a good job. Apparently it didn't stick. I can see why Jobst
>>>>>>> no longer bothers to respond.
>>>>>>>
>>>>>>> http://tinyurl.com/29v4u2
>>>>>>
>>>>>> Thanks for the link, that's an interesting thread. Before my time.
>>>>>>
>>>>>> How much more civilized everyone was back then!
>>>>>
>>>>> Unfortunately, incivility seems to drive the civil away. Perhaps
>>>>> that's the motive.
>>>>>
>>>>>> I might as well just
>>>>>> read the archives and not bother with new RBT.
>>>>>
>>>>> There's a lot to learn in many NG archives, I often get info there
>>>>> that I can't find with a web search -- on all kinds of topics.
>>>>
>>>> and yet, you seem to absorb so little!
>>>
>>> I think the evidence (for who is not absorbing) is there for anyone
>>> who wishes to take the trouble to find it. It's all in the archives.
>>
>> eh? you dig back through /four years/ of crap and you fuck up simple
>> things like elasticity, plasticity, etc? that's rich!
>>
>> btw, why are posting on a saturday? do you get paid on the weekends?
>
> Some things are difficult to put a price on.
but don't you only post on other peoples dollar?
|
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Date: 09 Sep 2007 13:38:09
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>>> jim beam wrote:
>>>>> Peter Cole wrote:
>>>>>> Ben C wrote:
>>>>>>> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>>>>>>> [...]
>>>>>>>> It was over 4 years ago. I thought Mike Prime (a metallurgist)
>>>>>>>> did a good job. Apparently it didn't stick. I can see why Jobst
>>>>>>>> no longer bothers to respond.
>>>>>>>>
>>>>>>>> http://tinyurl.com/29v4u2
>>>>>>>
>>>>>>> Thanks for the link, that's an interesting thread. Before my time.
>>>>>>>
>>>>>>> How much more civilized everyone was back then!
>>>>>>
>>>>>> Unfortunately, incivility seems to drive the civil away. Perhaps
>>>>>> that's the motive.
>>>>>>
>>>>>>> I might as well just
>>>>>>> read the archives and not bother with new RBT.
>>>>>>
>>>>>> There's a lot to learn in many NG archives, I often get info there
>>>>>> that I can't find with a web search -- on all kinds of topics.
>>>>>
>>>>> and yet, you seem to absorb so little!
>>>>
>>>> I think the evidence (for who is not absorbing) is there for anyone
>>>> who wishes to take the trouble to find it. It's all in the archives.
>>>
>>> eh? you dig back through /four years/ of crap and you fuck up simple
>>> things like elasticity, plasticity, etc? that's rich!
>>>
>>> btw, why are posting on a saturday? do you get paid on the weekends?
>>
>> Some things are difficult to put a price on.
>
> but don't you only post on other peoples dollar?
You're a genius. You should have been a private dick.
|
| | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Date: 09 Sep 2007 21:14:35
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> Peter Cole wrote:
>>> jim beam wrote:
>>>> Peter Cole wrote:
>>>>> jim beam wrote:
>>>>>> Peter Cole wrote:
>>>>>>> Ben C wrote:
>>>>>>>> On 2007-09-07, Peter Cole <peter_cole@comcast.net> wrote:
>>>>>>>> [...]
>>>>>>>>> It was over 4 years ago. I thought Mike Prime (a metallurgist)
>>>>>>>>> did a good job. Apparently it didn't stick. I can see why Jobst
>>>>>>>>> no longer bothers to respond.
>>>>>>>>>
>>>>>>>>> http://tinyurl.com/29v4u2
>>>>>>>>
>>>>>>>> Thanks for the link, that's an interesting thread. Before my time.
>>>>>>>>
>>>>>>>> How much more civilized everyone was back then!
>>>>>>>
>>>>>>> Unfortunately, incivility seems to drive the civil away. Perhaps
>>>>>>> that's the motive.
>>>>>>>
>>>>>>>> I might as well just
>>>>>>>> read the archives and not bother with new RBT.
>>>>>>>
>>>>>>> There's a lot to learn in many NG archives, I often get info
>>>>>>> there that I can't find with a web search -- on all kinds of topics.
>>>>>>
>>>>>> and yet, you seem to absorb so little!
>>>>>
>>>>> I think the evidence (for who is not absorbing) is there for anyone
>>>>> who wishes to take the trouble to find it. It's all in the archives.
>>>>
>>>> eh? you dig back through /four years/ of crap and you fuck up
>>>> simple things like elasticity, plasticity, etc? that's rich!
>>>>
>>>> btw, why are posting on a saturday? do you get paid on the weekends?
>>>
>>> Some things are difficult to put a price on.
>>
>> but don't you only post on other peoples dollar?
>
> You're a genius. You should have been a private dick.
better than being a public prick.
|
| | | | | | | | | | | | | | | |
Date: 05 Sep 2007 05:47:55
From: jim beam
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-05, clare at snyder.on.ca <> wrote:
> [...]
>> Loose spokes also wear the holes in the hubs - and wear the spokes
>> where they go through the hub.
>
> I hadn't thought of that. That would explain the phenomenon (loose
> spokes breaking) in a way that's consistent with my understanding of
> Jobst's earlier suggestion that there is a bit of clearance down there.
>
> I thought the reasoning was: the spoke can't easily be bent since it
> isn't firmly held in the hub hole but free to wobble a bit. But if it's
> wobbling up and down it can wear and that can initiate fatigue.
>
>> I've replaced numerous spokes that were worn half way through before
>> breaking (and some that had not yet broken)
>
> Maybe this is something datakoll's practice of putting Teflon wax in the
> hub holes before you put the spokes in could help with.
he lives in a hot salty climate, so in his case, it's more likely that
it mitigates corrosion or stress corrosion. sticky crap that retains
grit sure isn't going to do a thing to mitigate wear.
|
| | | | | | | | | | | | | | | | |
Date: 05 Sep 2007 08:10:55
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-05, jim beam <spamvortex@bad.example.net > wrote:
> Ben C wrote:
>> On 2007-09-05, clare at snyder.on.ca <> wrote:
>> [...]
>>> Loose spokes also wear the holes in the hubs - and wear the spokes
>>> where they go through the hub.
>>
>> I hadn't thought of that. That would explain the phenomenon (loose
>> spokes breaking) in a way that's consistent with my understanding of
>> Jobst's earlier suggestion that there is a bit of clearance down there.
>>
>> I thought the reasoning was: the spoke can't easily be bent since it
>> isn't firmly held in the hub hole but free to wobble a bit. But if it's
>> wobbling up and down it can wear and that can initiate fatigue.
>>
>>> I've replaced numerous spokes that were worn half way through before
>>> breaking (and some that had not yet broken)
>>
>> Maybe this is something datakoll's practice of putting Teflon wax in the
>> hub holes before you put the spokes in could help with.
>
> he lives in a hot salty climate, so in his case, it's more likely that
> it mitigates corrosion or stress corrosion. sticky crap that retains
> grit sure isn't going to do a thing to mitigate wear.
Good point. IIRC he may also have reported this was a way to get more
life out of generic spokes. I don't know if those are the galvanized
kind, but also some kinds of Chinese "stainless" steel do rust in little
spots. I know because I've seen it happen to teaspoons.
|
| | | | | | | | | | | | | | | | | |
Date: 05 Sep 2007 21:21:54
From:
Subject: Re: Yet another broken spoke
|
Ben C? writes:
>>>> Loose spokes also wear the holes in the hubs - and wear the
>>>> spokes where they go through the hub.
>>> I hadn't thought of that. That would explain the phenomenon
>>> (loose spokes breaking) in a way that's consistent with my
>>> understanding of Jobst's earlier suggestion that there is a bit of
>>> clearance down there.
>>> I thought the reasoning was: the spoke can't easily be bent since
>>> it isn't firmly held in the hub hole but free to wobble a bit.
>>> But if it's wobbling up and down it can wear and that can initiate
>>> fatigue.
>>>> I've replaced numerous spokes that were worn half way through
>>>> before breaking (and some that had not yet broken)
>>> Maybe this is something datakoll's practice of putting Teflon wax
>>> in the hub holes before you put the spokes in could help with.
>> he lives in a hot salty climate, so in his case, it's more likely
>> that it mitigates corrosion or stress corrosion. sticky crap that
>> retains grit sure isn't going to do a thing to mitigate wear.
> Good point. IIRC he may also have reported this was a way to get
> more life out of generic spokes. I don't know if those are the
> galvanized kind, but also some kinds of Chinese "stainless" steel do
> rust in little spots. I know because I've seen it happen to
> teaspoons.
You needn't fly your kite on every breeze that comes along. Remember,
it's the jam nut on valve stems that caused stem separations about a
year ago, information that was brought to this newsgroup by the same
folks who say spokes break from low tension.
Jobst Brandt
|
| | | | | | | | | | | | | | | | | | |
Date: 05 Sep 2007 20:59:07
From: jim beam
Subject: Re: Yet another broken spoke
|
jobst.brandt@stanfordalumni.org wrote:
> Ben C? writes:
>
>>>>> Loose spokes also wear the holes in the hubs - and wear the
>>>>> spokes where they go through the hub.
>
>>>> I hadn't thought of that. That would explain the phenomenon
>>>> (loose spokes breaking) in a way that's consistent with my
>>>> understanding of Jobst's earlier suggestion that there is a bit of
>>>> clearance down there.
>
>>>> I thought the reasoning was: the spoke can't easily be bent since
>>>> it isn't firmly held in the hub hole but free to wobble a bit.
>>>> But if it's wobbling up and down it can wear and that can initiate
>>>> fatigue.
>
>>>>> I've replaced numerous spokes that were worn half way through
>>>>> before breaking (and some that had not yet broken)
>
>>>> Maybe this is something datakoll's practice of putting Teflon wax
>>>> in the hub holes before you put the spokes in could help with.
>
>>> he lives in a hot salty climate, so in his case, it's more likely
>>> that it mitigates corrosion or stress corrosion. sticky crap that
>>> retains grit sure isn't going to do a thing to mitigate wear.
>
>> Good point. IIRC he may also have reported this was a way to get
>> more life out of generic spokes. I don't know if those are the
>> galvanized kind, but also some kinds of Chinese "stainless" steel do
>> rust in little spots. I know because I've seen it happen to
>> teaspoons.
>
> You needn't fly your kite on every breeze that comes along. Remember,
> it's the jam nut on valve stems that caused stem separations about a
> year ago, information that was brought to this newsgroup by the same
> folks who say spokes break from low tension.
specious crap - rubber usage has /nothing/ to do with metal fatigue.
|
| | | | | | | | | | | | | | | | | | | |
Date: 06 Sep 2007 16:10:35
From: Peter Cole
Subject: Re: Yet another broken spoke
|
jim beam wrote:
> jobst.brandt@stanfordalumni.org wrote:
>> Ben C? writes:
>>
>>>>>> Loose spokes also wear the holes in the hubs - and wear the
>>>>>> spokes where they go through the hub.
>>
>>>>> I hadn't thought of that. That would explain the phenomenon
>>>>> (loose spokes breaking) in a way that's consistent with my
>>>>> understanding of Jobst's earlier suggestion that there is a bit of
>>>>> clearance down there.
>>
>>>>> I thought the reasoning was: the spoke can't easily be bent since
>>>>> it isn't firmly held in the hub hole but free to wobble a bit.
>>>>> But if it's wobbling up and down it can wear and that can initiate
>>>>> fatigue.
>>
>>>>>> I've replaced numerous spokes that were worn half way through
>>>>>> before breaking (and some that had not yet broken)
>>
>>>>> Maybe this is something datakoll's practice of putting Teflon wax
>>>>> in the hub holes before you put the spokes in could help with.
>>
>>>> he lives in a hot salty climate, so in his case, it's more likely
>>>> that it mitigates corrosion or stress corrosion. sticky crap that
>>>> retains grit sure isn't going to do a thing to mitigate wear.
>>
>>> Good point. IIRC he may also have reported this was a way to get
>>> more life out of generic spokes. I don't know if those are the
>>> galvanized kind, but also some kinds of Chinese "stainless" steel do
>>> rust in little spots. I know because I've seen it happen to
>>> teaspoons.
>>
>> You needn't fly your kite on every breeze that comes along. Remember,
>> it's the jam nut on valve stems that caused stem separations about a
>> year ago, information that was brought to this newsgroup by the same
>> folks who say spokes break from low tension.
>
> specious crap - rubber usage has /nothing/ to do with metal fatigue.
Does this mean you won't repeat your spew of everything (off topic) you
disagree with when he posts?
|
| | | | | | | | | | | | | | | | | | | | |
Date: 06 Sep 2007 20:59:21
From: jim beam
Subject: Re: Yet another broken spoke
|
Peter Cole wrote:
> jim beam wrote:
>> jobst.brandt@stanfordalumni.org wrote:
>>> Ben C? writes:
>>>
>>>>>>> Loose spokes also wear the holes in the hubs - and wear the
>>>>>>> spokes where they go through the hub.
>>>
>>>>>> I hadn't thought of that. That would explain the phenomenon
>>>>>> (loose spokes breaking) in a way that's consistent with my
>>>>>> understanding of Jobst's earlier suggestion that there is a bit of
>>>>>> clearance down there.
>>>
>>>>>> I thought the reasoning was: the spoke can't easily be bent since
>>>>>> it isn't firmly held in the hub hole but free to wobble a bit.
>>>>>> But if it's wobbling up and down it can wear and that can initiate
>>>>>> fatigue.
>>>
>>>>>>> I've replaced numerous spokes that were worn half way through
>>>>>>> before breaking (and some that had not yet broken)
>>>
>>>>>> Maybe this is something datakoll's practice of putting Teflon wax
>>>>>> in the hub holes before you put the spokes in could help with.
>>>
>>>>> he lives in a hot salty climate, so in his case, it's more likely
>>>>> that it mitigates corrosion or stress corrosion. sticky crap that
>>>>> retains grit sure isn't going to do a thing to mitigate wear.
>>>
>>>> Good point. IIRC he may also have reported this was a way to get
>>>> more life out of generic spokes. I don't know if those are the
>>>> galvanized kind, but also some kinds of Chinese "stainless" steel do
>>>> rust in little spots. I know because I've seen it happen to
>>>> teaspoons.
>>>
>>> You needn't fly your kite on every breeze that comes along. Remember,
>>> it's the jam nut on valve stems that caused stem separations about a
>>> year ago, information that was brought to this newsgroup by the same
>>> folks who say spokes break from low tension.
>>
>> specious crap - rubber usage has /nothing/ to do with metal fatigue.
>
> Does this mean you won't repeat your spew of everything (off topic) you
> disagree with when he posts?
eh?
|
| | | | | | | | | | |
Date: 04 Sep 2007 16:51:05
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-04, clare at snyder.on.ca < > wrote:
> On Tue, 04 Sep 2007 15:35:56 -0500, Ben C <spamspam@spam.eggs> wrote:
>
>>On 2007-09-04, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org> wrote:
>>[...]
>>> With a tighter spoke the stress variation can have a larger excursion
>>> than that of a looser spoke.
>>
>>Why?
>>
>>Just to clarify: suppose I plot a graph of stress against time for a
>>spoke on a wheel on a bicycle that's being ridden down the road. I
>>expect the graph would be some kind of wave, going up and down as the
>>spoke passes over the contact patch.
>>
>>By "larger excursion" do you mean that this wave would have a greater
>>amplitude?
>>
>>Perhaps I'm being stupid but I don't see why you would get a larger
>>amplitude for a tighter spoke.
>
>
> Because you would not. If tensioned to, say 200 lbs, and 200 lbs is
> suspended from roughly8 of the 28 spokes, you might end up with
> something like 250 lbs tension on any one spoke.
Are we still talking about riding on the wheel here? You say "suspended"
and I'm not sure.
If you had 200lbf spoke tension (which is a bit high, usually it's more
like 100lbf I think), about 28 spokes, and you put a weight of 250lbs on
the bike, so acting at the hub, you'd expect to see some of the spokes
in the bottom part of the wheel lose a bit of tension, and little or no
tension change in the spokes in the top half. No spoke would go up to
250lbf tension.
> That tension would only change something like 60 lbs in use, and at
> all times the spoke would be under a minimum of something like 140
> lbs. With a 15 or 14 guage spoke,that tension would keep the spoke
> from fatigue.
>
> Think of the spoke as a bolt, and read the following from
> Writetool.com:
[...]
> How can we get all of the strength we pay for, or do we assume the
> bolt strength is only 500 lbs. and use twice as many bolts in the
> joint? If the joint has been properly designed, the clamping surfaces
> around the bolt will take almost all of the variation if the bolt is
> properly tightened.
This is an interesting theory, but I'm not sure it's correct to think of
the spoke as a bolt this way. The equivalent of "the clamping surfaces
around the bolt" is the rest of the wheel, i.e. the rim basically. The
rim is quite stiff, and so I don't think we can build the wheel tight
enough so that the rim flexes but the spokes don't.
But in the bolt example the idea is that the bolt doesn't get a stress
cycle at all (or not much of a one).
The spokes are always going to have a stress cycle. We don't care about
the axial stress cycle (stretching the spoke along its length and
letting it relax again), because the size of the stress in that cycle is
very small compared to the yield strength of the spoke in that
direction, which means fatigue life in that direction is very long and
not a problem.
The key thing is the elbow. If the spoke goes loose, does the elbow bend
and unbend? Bending and unbending means leverage, and therefore much
higher stresses on parts of the spoke. Not enough stress to break it in
one go, but enough to reduce the number of cycles to failure to only a
few hundred miles of riding.
So does it bend and unbend? Jobst says no, jim beam says yes, although
it's not unusual for those guys to disagree with each other.
I think it's very hard to say because how much leverage there is depends
on the details of how the spoke is supported at the elbow and just how
things move around (and don't forget about the interleaving) when the
rim deforms at the contact patch.
It doesn't take much force to bend a spoke (i.e. bring it right up to
yield) when one end of it is anchored in a hub and you're pulling on the
long end. We do it all the time when building wheels often without
thinking about it or doing it deliberately. So I can easily believe that
a slack spoke does receive a cycle that involves stresses close to yield
at the elbow that therefore lead it to premature fatigue failure.
But one cannot rule out the opinion of Jobst easily, and he has a much
better quantitative idea of things like how much the rim does move by
and how much clearance is present in the hub hole than I do.
|
| | | | | | | | | | | |
Date: 04 Sep 2007 18:42:04
From:
Subject: Re: Yet another broken spoke
|
On Tue, 04 Sep 2007 16:51:05 -0500, Ben C <spamspam@spam.eggs > wrote:
>On 2007-09-04, clare at snyder.on.ca <> wrote:
>> On Tue, 04 Sep 2007 15:35:56 -0500, Ben C <spamspam@spam.eggs> wrote:
>>
>>>On 2007-09-04, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org> wrote:
>>>[...]
>>>> With a tighter spoke the stress variation can have a larger excursion
>>>> than that of a looser spoke.
>>>
>>>Why?
>>>
>>>Just to clarify: suppose I plot a graph of stress against time for a
>>>spoke on a wheel on a bicycle that's being ridden down the road. I
>>>expect the graph would be some kind of wave, going up and down as the
>>>spoke passes over the contact patch.
>>>
>>>By "larger excursion" do you mean that this wave would have a greater
>>>amplitude?
>>>
>>>Perhaps I'm being stupid but I don't see why you would get a larger
>>>amplitude for a tighter spoke.
>>
>>
>> Because you would not. If tensioned to, say 200 lbs, and 200 lbs is
>> suspended from roughly8 of the 28 spokes, you might end up with
>> something like 250 lbs tension on any one spoke.
>
>Are we still talking about riding on the wheel here? You say "suspended"
>and I'm not sure.
>
>If you had 200lbf spoke tension (which is a bit high, usually it's more
>like 100lbf I think), about 28 spokes, and you put a weight of 250lbs on
>the bike, so acting at the hub, you'd expect to see some of the spokes
>in the bottom part of the wheel lose a bit of tension, and little or no
>tension change in the spokes in the top half. No spoke would go up to
>250lbf tension.
>
>> That tension would only change something like 60 lbs in use, and at
>> all times the spoke would be under a minimum of something like 140
>> lbs. With a 15 or 14 guage spoke,that tension would keep the spoke
>> from fatigue.
>>
>> Think of the spoke as a bolt, and read the following from
>> Writetool.com:
>[...]
>> How can we get all of the strength we pay for, or do we assume the
>> bolt strength is only 500 lbs. and use twice as many bolts in the
>> joint? If the joint has been properly designed, the clamping surfaces
>> around the bolt will take almost all of the variation if the bolt is
>> properly tightened.
>
>This is an interesting theory, but I'm not sure it's correct to think of
>the spoke as a bolt this way. The equivalent of "the clamping surfaces
>around the bolt" is the rest of the wheel, i.e. the rim basically. The
>rim is quite stiff, and so I don't think we can build the wheel tight
>enough so that the rim flexes but the spokes don't.
>
>But in the bolt example the idea is that the bolt doesn't get a stress
>cycle at all (or not much of a one).
>
>The spokes are always going to have a stress cycle. We don't care about
>the axial stress cycle (stretching the spoke along its length and
>letting it relax again), because the size of the stress in that cycle is
>very small compared to the yield strength of the spoke in that
>direction, which means fatigue life in that direction is very long and
>not a problem.
>
>The key thing is the elbow. If the spoke goes loose, does the elbow bend
>and unbend? Bending and unbending means leverage, and therefore much
>higher stresses on parts of the spoke. Not enough stress to break it in
>one go, but enough to reduce the number of cycles to failure to only a
>few hundred miles of riding.
>
>So does it bend and unbend? Jobst says no, jim beam says yes, although
>it's not unusual for those guys to disagree with each other.
>
>I think it's very hard to say because how much leverage there is depends
>on the details of how the spoke is supported at the elbow and just how
>things move around (and don't forget about the interleaving) when the
>rim deforms at the contact patch.
>
>It doesn't take much force to bend a spoke (i.e. bring it right up to
>yield) when one end of it is anchored in a hub and you're pulling on the
>long end. We do it all the time when building wheels often without
>thinking about it or doing it deliberately. So I can easily believe that
>a slack spoke does receive a cycle that involves stresses close to yield
>at the elbow that therefore lead it to premature fatigue failure.
>
>But one cannot rule out the opinion of Jobst easily, and he has a much
>better quantitative idea of things like how much the rim does move by
>and how much clearance is present in the hub hole than I do.
Like a said, my numbers were picked from thin air - but the tension
and related bending at the elbow are real. I've never had a properly
tensioned spoke break, and I've had some pretty crappy wheels over the
years. I've had lots of loose spokes break.
Today when I work on a bike with a broken spoke, invariably I find a
generally sloppy wheel.(loose spokes)
--
Posted via a free Usenet account from http://www.teranews.com
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Date: 04 Sep 2007 20:32:53
From: jim beam
Subject: Re: Yet another broken spoke
|
clare at snyder.on.ca wrote:
> On Tue, 04 Sep 2007 16:51:05 -0500, Ben C <spamspam@spam.eggs> wrote:
>
>> On 2007-09-04, clare at snyder.on.ca <> wrote:
>>> On Tue, 04 Sep 2007 15:35:56 -0500, Ben C <spamspam@spam.eggs> wrote:
>>>
>>>> On 2007-09-04, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org> wrote:
>>>> [...]
>>>>> With a tighter spoke the stress variation can have a larger excursion
>>>>> than that of a looser spoke.
>>>> Why?
>>>>
>>>> Just to clarify: suppose I plot a graph of stress against time for a
>>>> spoke on a wheel on a bicycle that's being ridden down the road. I
>>>> expect the graph would be some kind of wave, going up and down as the
>>>> spoke passes over the contact patch.
>>>>
>>>> By "larger excursion" do you mean that this wave would have a greater
>>>> amplitude?
>>>>
>>>> Perhaps I'm being stupid but I don't see why you would get a larger
>>>> amplitude for a tighter spoke.
>>>
>>> Because you would not. If tensioned to, say 200 lbs, and 200 lbs is
>>> suspended from roughly8 of the 28 spokes, you might end up with
>>> something like 250 lbs tension on any one spoke.
>> Are we still talking about riding on the wheel here? You say "suspended"
>> and I'm not sure.
>>
>> If you had 200lbf spoke tension (which is a bit high, usually it's more
>> like 100lbf I think), about 28 spokes, and you put a weight of 250lbs on
>> the bike, so acting at the hub, you'd expect to see some of the spokes
>> in the bottom part of the wheel lose a bit of tension, and little or no
>> tension change in the spokes in the top half. No spoke would go up to
>> 250lbf tension.
>>
>>> That tension would only change something like 60 lbs in use, and at
>>> all times the spoke would be under a minimum of something like 140
>>> lbs. With a 15 or 14 guage spoke,that tension would keep the spoke
>>> from fatigue.
>>>
>>> Think of the spoke as a bolt, and read the following from
>>> Writetool.com:
>> [...]
>>> How can we get all of the strength we pay for, or do we assume the
>>> bolt strength is only 500 lbs. and use twice as many bolts in the
>>> joint? If the joint has been properly designed, the clamping surfaces
>>> around the bolt will take almost all of the variation if the bolt is
>>> properly tightened.
>> This is an interesting theory, but I'm not sure it's correct to think of
>> the spoke as a bolt this way. The equivalent of "the clamping surfaces
>> around the bolt" is the rest of the wheel, i.e. the rim basically. The
>> rim is quite stiff, and so I don't think we can build the wheel tight
>> enough so that the rim flexes but the spokes don't.
>>
>> But in the bolt example the idea is that the bolt doesn't get a stress
>> cycle at all (or not much of a one).
>>
>> The spokes are always going to have a stress cycle. We don't care about
>> the axial stress cycle (stretching the spoke along its length and
>> letting it relax again), because the size of the stress in that cycle is
>> very small compared to the yield strength of the spoke in that
>> direction, which means fatigue life in that direction is very long and
>> not a problem.
>>
>> The key thing is the elbow. If the spoke goes loose, does the elbow bend
>> and unbend? Bending and unbending means leverage, and therefore much
>> higher stresses on parts of the spoke. Not enough stress to break it in
>> one go, but enough to reduce the number of cycles to failure to only a
>> few hundred miles of riding.
>>
>> So does it bend and unbend? Jobst says no, jim beam says yes, although
>> it's not unusual for those guys to disagree with each other.
>>
>> I think it's very hard to say because how much leverage there is depends
>> on the details of how the spoke is supported at the elbow and just how
>> things move around (and don't forget about the interleaving) when the
>> rim deforms at the contact patch.
>>
>> It doesn't take much force to bend a spoke (i.e. bring it right up to
>> yield) when one end of it is anchored in a hub and you're pulling on the
>> long end. We do it all the time when building wheels often without
>> thinking about it or doing it deliberately. So I can easily believe that
>> a slack spoke does receive a cycle that involves stresses close to yield
>> at the elbow that therefore lead it to premature fatigue failure.
>>
>> But one cannot rule out the opinion of Jobst easily, and he has a much
>> better quantitative idea of things like how much the rim does move by
>> and how much clearance is present in the hub hole than I do.
>
>
> Like a said, my numbers were picked from thin air - but the tension
> and related bending at the elbow are real. I've never had a properly
> tensioned spoke break, and I've had some pretty crappy wheels over the
> years. I've had lots of loose spokes break.
>
> Today when I work on a bike with a broken spoke, invariably I find a
> generally sloppy wheel.(loose spokes)
>
and that is the crux of the matter. jobst claims to "solve" the fatigue
problem with a bunch of underinformed bullshit and suppositional
fantasy, but reality is, the /process/ he describes [claims to have
"invented"] is that of the european masters - and which works for
exactly the reason you say - spokes stay tight, hence they do not bend
as much, hence they do not fatigue as fast.
and that's all there is to it.
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Date: 03 Sep 2007 22:20:42
From:
Subject: Re: Yet another broken spoke
|
I wrote:
>>>> And be SURE the spokes are tensioned adequately. Loose spokes
>>>> break. Tight spokes don't (as a general rule of thumb)
>>> I keep seeing this admonition yet no one seems to be able to
>>> describe the mechanism that causes such spoke failures. Loosely
>>> spoked wheels can allow the nipples to unscrew and cause wheel
>>> misalignment, but spoke failure is caused by metal fatigue that
>>> arises from tension change, caused once with every wheel rotation
>>> as spokes pass through the zone of tire contact with the road.
>>> This must occur with stress near the yield stress, something that
>>> does not readily occur in loose spokes.
>>> Please explain.
>> A properly tensioned spoke is "pre stretched" and does not flex or
>> stretch in operation. A loose spoke bends at least twice every
>> revolution, and stretches repeatedly. This is what fatigues a
>> spoke and breaks it.
> Please explain what bends the spokes. Rim deflection is a few
> thousandths of an inch, the spoke holes in the flange have 10 to 20
> thousandths clearance and spoke nipples much more. Where is this
> fatiguing compression force arising? Spokes do not go into column
> buckling when slack.
> I have a feeling the concept requires some exaggerated model of a
> spoke that is less than properly tight. The bending of which you
> speak cannot occur and cause fatiguing stress. To do that the bend
> would need to approach yield (permanent deformation). To see what
> that is, try how much of a bend it takes to put a bend in a spoke by
> manually using it as a walking cane.
I should add that the subject of this thread is short term spoke
failure, not infinite life or long term fatigue. For short term spoke
failure, as this one seems to be from the description, low spoke
tension cannot be the cause and similarly for others that have raised
the specter of low tension. If the spokes are not reused or poor
quality spokes, stress concentrations that have not been relieved are
the cause of failure as has been discussed at length in this forum.
Waving the long term fatigue flag does not answer the question of how
low spoke tension causes spoke failure; a claim that appears in this
newsgroup often. I believe the example of rim deflection under riding
loads (which is the amount by which spoke preload is reduced) is the
appropriate parameter for stress change and it shows that compression
buckling is not possible in that respect as I pointed out.
Jobst Brandt
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Date: 03 Sep 2007 15:43:50
From: jim beam
Subject: Re: Yet another broken spoke
|
jobst.brandt@stanfordalumni.org wrote:
> I wrote:
>
>>>>> And be SURE the spokes are tensioned adequately. Loose spokes
>>>>> break. Tight spokes don't (as a general rule of thumb)
>
>>>> I keep seeing this admonition yet no one seems to be able to
>>>> describe the mechanism that causes such spoke failures. Loosely
>>>> spoked wheels can allow the nipples to unscrew and cause wheel
>>>> misalignment, but spoke failure is caused by metal fatigue that
>>>> arises from tension change, caused once with every wheel rotation
>>>> as spokes pass through the zone of tire contact with the road.
>>>> This must occur with stress near the yield stress, something that
>>>> does not readily occur in loose spokes.
>
>>>> Please explain.
>
>>> A properly tensioned spoke is "pre stretched" and does not flex or
>>> stretch in operation. A loose spoke bends at least twice every
>>> revolution, and stretches repeatedly. This is what fatigues a
>>> spoke and breaks it.
>
>> Please explain what bends the spokes. Rim deflection is a few
>> thousandths of an inch, the spoke holes in the flange have 10 to 20
>> thousandths clearance and spoke nipples much more. Where is this
>> fatiguing compression force arising? Spokes do not go into column
>> buckling when slack.
>
>> I have a feeling the concept requires some exaggerated model of a
>> spoke that is less than properly tight. The bending of which you
>> speak cannot occur and cause fatiguing stress. To do that the bend
>> would need to approach yield (permanent deformation). To see what
>> that is, try how much of a bend it takes to put a bend in a spoke by
>> manually using it as a walking cane.
>
> I should add that the subject of this thread is short term spoke
> failure, not infinite life or long term fatigue. For short term spoke
> failure, as this one seems to be from the description, low spoke
> tension cannot be the cause and similarly for others that have raised
> the specter of low tension. If the spokes are not reused or poor
> quality spokes, stress concentrations that have not been relieved
be careful with that usage - "stress concentrations" are what occur at
stress risers, e.g. surface defects. a stress concentration is not
"residual stress" which is what you're talking about.
> are
> the cause of failure as has been discussed at length in this forum.
no, they have been asserted at length by those who don't understand the
subject sufficiently and who have never bothered to examine a fracture
surface and correlate that with residual stress profiles.
>
> Waving the long term fatigue flag does not answer the question of how
> low spoke tension causes spoke failure; a claim that appears in this
> newsgroup often. I believe the example of rim deflection under riding
> loads (which is the amount by which spoke preload is reduced) is the
> appropriate parameter for stress change and it shows that compression
> buckling is not possible in that respect as I pointed out.
>
> Jobst Brandt
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Date: 03 Sep 2007 06:44:39
From: jim beam
Subject: Re: Yet another broken spoke
|
jobst.brandt@stanfordalumni.org wrote:
> Clare who? writes:
>
>>>> And be SURE the spokes are tensioned adequately. Loose spokes break.
>>>> Tight spokes don't (as a general rule of thumb)
>
>>> I keep seeing this admonition yet no one seems to be able to describe
>>> the mechanism that causes such spoke failures. Loosely spoked wheels
>>> can allow the nipples to unscrew and cause wheel misalignment, but
>>> spoke failure is caused by metal fatigue that arises from tension
>>> change, caused once with every wheel rotation as spokes pass through
>>> the zone of tire contact with the road. This must occur with stress
>>> near the yield stress, something that does not readily occur in loose
>>> spokes.
>
>>> Please explain.
>
>> A properly tensioned spoke is "pre stretched" and does not flex or
>> stretch in operation. A loose spoke bends at least twice every
>> revolution, and stretches repeatedly. This is what fatigues a spoke
>> and breaks it.
>
> Please explain what bends the spokes.
interleaving. the spoke that goes slack receives its bending from it's
interleaving neighbor.
and the fact that spokes fatigue at the elbow [as opposed to another
location] means that is where the bending is greatest - by definition.
> Rim deflection is a few
> thousandths of an inch, the spoke holes in the flange have 10 to 20
> thousandths clearance and spoke nipples much more. Where is this
> fatiguing compression force arising? Spokes do not go into column
> buckling when slack.
red herring.
>
> I have a feeling the concept requires some exaggerated model of a
> spoke that is less than properly tight. The bending of which you
> speak cannot occur and cause fatiguing stress.
simply untrue. you don't understand the principles of fatigue.
> To do that the bend
> would need to approach yield (permanent deformation).
er, fatigue happens well below yield - that's why it's called "fatigue"
and not "yield". you really need to study this subject before you can
credibly presume to lecture on it.
> To see what
> that is, try how much of a bend it takes to put a bend in a spoke by
> manually using it as a walking cane.
red herring. the elbow bends in tension, not just compression. the
very fact that the elbow is offset from the spoke axis ensures there is
a bending moment. again, that's by definition.
|
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Date: 03 Sep 2007 10:20:28
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-03, jim beam <spamvortex@bad.example.net > wrote:
> jobst.brandt@stanfordalumni.org wrote:
[...]
>> I have a feeling the concept requires some exaggerated model of a
>> spoke that is less than properly tight. The bending of which you
>> speak cannot occur and cause fatiguing stress.
>
> simply untrue. you don't understand the principles of fatigue.
>
>
>> To do that the bend
>> would need to approach yield (permanent deformation).
>
> er, fatigue happens well below yield - that's why it's called "fatigue"
> and not "yield".
Yes, and as I think you've pointed out before, the steel typically used
for spokes doesn't have a fatigue limit, so there is always fatigue in
use.
The question is time to failure-- a few hundred miles or tens of
thousands.
Fatigue happens below yield, but premature fatigue happens close to
yield, I think is the point.
So the interesting question is, what does the stress cycle for a
too-loose spoke look like?
[...]
>> To see what
>> that is, try how much of a bend it takes to put a bend in a spoke by
>> manually using it as a walking cane.
>
> red herring. the elbow bends in tension, not just compression. the
> very fact that the elbow is offset from the spoke axis ensures there is
> a bending moment. again, that's by definition.
So you're saying that if a spoke goes slack enough to exceed its
preload, it will pretty much inevitably get at or close to yield stress
around the bend?
Jobst was suggesting I think that there's a bit of slop around the hub
hole and the rim hole to take up first, that's typically bigger than the
amount of rim deformation. Seems a reasonable argument. It all depends
on the amounts these things move by which we have some idea of from FEAs
and things.
|
| | | | | | | | |
Date: 03 Sep 2007 08:53:18
From: jim beam
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-03, jim beam <spamvortex@bad.example.net> wrote:
>> jobst.brandt@stanfordalumni.org wrote:
> [...]
>>> I have a feeling the concept requires some exaggerated model of a
>>> spoke that is less than properly tight. The bending of which you
>>> speak cannot occur and cause fatiguing stress.
>> simply untrue. you don't understand the principles of fatigue.
>>
>>
>>> To do that the bend
>>> would need to approach yield (permanent deformation).
>> er, fatigue happens well below yield - that's why it's called "fatigue"
>> and not "yield".
>
> Yes, and as I think you've pointed out before, the steel typically used
> for spokes doesn't have a fatigue limit, so there is always fatigue in
> use.
>
> The question is time to failure-- a few hundred miles or tens of
> thousands.
>
> Fatigue happens below yield, but premature fatigue happens close to
> yield, I think is the point.
>
> So the interesting question is, what does the stress cycle for a
> too-loose spoke look like?
that is indeed the question.
http://www.flickr.com/photos/38636024@N00/1313347532/
what's the elastic deviation here? a couple of degrees? what's the
stress delta between that and straight for the elbow?
>
> [...]
>>> To see what
>>> that is, try how much of a bend it takes to put a bend in a spoke by
>>> manually using it as a walking cane.
>> red herring. the elbow bends in tension, not just compression. the
>> very fact that the elbow is offset from the spoke axis ensures there is
>> a bending moment. again, that's by definition.
>
> So you're saying that if a spoke goes slack enough to exceed its
> preload, it will pretty much inevitably get at or close to yield stress
> around the bend?
not yield, but there will be a stress cycle, and it's cycling that
causes fatigue.
>
> Jobst was suggesting I think that there's a bit of slop around the hub
> hole and the rim hole to take up first, that's typically bigger than the
> amount of rim deformation.
rim deformation is a red herring - yes, the rim deforms, but we're not
worried about rim fatigue, we're worried about spoke fatigue, so let's
figure out what's going on there.
> Seems a reasonable argument. It all depends
> on the amounts these things move by which we have some idea of from FEAs
> and things.
right, but you don't need fea to calculate the stress rise for a bending
elbow. it's not a simple calculation, but the whole fea thing is
water-muddying.
|
| | | | | | | | | |
Date: 03 Sep 2007 11:20:20
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-03, jim beam <spamvortex@bad.example.net > wrote:
> Ben C wrote:
[...]
>> So the interesting question is, what does the stress cycle for a
>> too-loose spoke look like?
>
> that is indeed the question.
>
> http://www.flickr.com/photos/38636024@N00/1313347532/
>
> what's the elastic deviation here? a couple of degrees? what's the
> stress delta between that and straight for the elbow?
Good question, I don't know.
>> [...]
>>>> To see what
>>>> that is, try how much of a bend it takes to put a bend in a spoke by
>>>> manually using it as a walking cane.
>>> red herring. the elbow bends in tension, not just compression. the
>>> very fact that the elbow is offset from the spoke axis ensures there is
>>> a bending moment. again, that's by definition.
>>
>> So you're saying that if a spoke goes slack enough to exceed its
>> preload, it will pretty much inevitably get at or close to yield stress
>> around the bend?
>
> not yield, but there will be a stress cycle, and it's cycling that
> causes fatigue.
Yes but, at the risk of stating the obvious, the spoke has a stress
cycle anyway whenever you ride the bike. But the mean stress in that
cycle is low enough, or so you hope, that the spokes last a good long
time.
>> Jobst was suggesting I think that there's a bit of slop around the hub
>> hole and the rim hole to take up first, that's typically bigger than the
>> amount of rim deformation.
>
> rim deformation is a red herring - yes, the rim deforms, but we're not
> worried about rim fatigue, we're worried about spoke fatigue, so let's
> figure out what's going on there.
I was thinking that the rim deformation is what brings the threaded end
of the spoke closer to the hub and therefore allows it to bend.
>> Seems a reasonable argument. It all depends
>> on the amounts these things move by which we have some idea of from FEAs
>> and things.
>
> right, but you don't need fea to calculate the stress rise for a bending
> elbow. it's not a simple calculation, but the whole fea thing is
> water-muddying.
Unless one actually provides the FEA, yes. Otherwise it just is a way of
doing that calculation.
|
| | | | | | | | | | |
Date: 03 Sep 2007 09:28:27
From: jim beam
Subject: Re: Yet another broken spoke
|
Ben C wrote:
> On 2007-09-03, jim beam <spamvortex@bad.example.net> wrote:
>> Ben C wrote:
> [...]
>>> So the interesting question is, what does the stress cycle for a
>>> too-loose spoke look like?
>> that is indeed the question.
>>
>> http://www.flickr.com/photos/38636024@N00/1313347532/
>>
>> what's the elastic deviation here? a couple of degrees? what's the
>> stress delta between that and straight for the elbow?
>
> Good question, I don't know.
>
>>> [...]
>>>>> To see what
>>>>> that is, try how much of a bend it takes to put a bend in a spoke by
>>>>> manually using it as a walking cane.
>>>> red herring. the elbow bends in tension, not just compression. the
>>>> very fact that the elbow is offset from the spoke axis ensures there is
>>>> a bending moment. again, that's by definition.
>>> So you're saying that if a spoke goes slack enough to exceed its
>>> preload, it will pretty much inevitably get at or close to yield stress
>>> around the bend?
>> not yield, but there will be a stress cycle, and it's cycling that
>> causes fatigue.
>
> Yes but, at the risk of stating the obvious, the spoke has a stress
> cycle anyway whenever you ride the bike. But the mean stress in that
> cycle is low enough, or so you hope, that the spokes last a good long
> time.
the axial spoke tension is relatively low as a faction of yield, but
spoke /bending/ is unaddressed in consideration by the ancients. pretty
fundamental omission since the spoke is not axially loaded due to its
offset and fatigue evidence _proves_ bending to be the stress cycle of
interest.
>
>>> Jobst was suggesting I think that there's a bit of slop around the hub
>>> hole and the rim hole to take up first, that's typically bigger than the
>>> amount of rim deformation.
>> rim deformation is a red herring - yes, the rim deforms, but we're not
>> worried about rim fatigue, we're worried about spoke fatigue, so let's
>> figure out what's going on there.
>
> I was thinking that the rim deformation is what brings the threaded end
> of the spoke closer to the hub and therefore allows it to bend.
don't swallow the herring - you don't need to know that to get to the
point. what you /do/ need to know is that the spoke is
a. loaded, and
b. subject to bending.
then you can try to figure out by how much.
>
>>> Seems a reasonable argument. It all depends
>>> on the amounts these things move by which we have some idea of from FEAs
>>> and things.
>> right, but you don't need fea to calculate the stress rise for a bending
>> elbow. it's not a simple calculation, but the whole fea thing is
>> water-muddying.
>
> Unless one actually provides the FEA, yes. Otherwise it just is a way of
> doing that calculation.
|
| | | | | | |
Date: 03 Sep 2007 02:43:41
From: Ben C
Subject: Re: Yet another broken spoke
|
On 2007-09-03, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org > wrote:
> Clare who? writes:
>
>>>> And be SURE the spokes are tensioned adequately. Loose spokes break.
>>>> Tight spokes don't (as a general rule of thumb)
>
>>> I keep seeing this admonition yet no one seems to be able to describe
>>> the mechanism that causes such spoke failures. Loosely spoked wheels
>>> can allow the nipples to unscrew and cause wheel misalignment, but
>>> spoke failure is caused by metal fatigue that arises from tension
>>> change, caused once with every wheel rotation as spokes pass through
>>> the zone of tire contact with the road. This must occur with stress
>>> near the yield stress, something that does not readily occur in loose
>>> spokes.
>
>>> Please explain.
I also thought that, and my reason was the same as Clare's. If a spoke
loses preload it might bend out of line resulting in enough moment to
produce yield stress (or close to it) at the elbow.
I admit I have absolutely no evidence that that's what happens, so I'm
glad you brought this up.
>> A properly tensioned spoke is "pre stretched" and does not flex or
>> stretch in operation. A loose spoke bends at least twice every
>> revolution, and stretches repeatedly. This is what fatigues a spoke
>> and breaks it.
>
> Please explain what bends the spokes. Rim deflection is a few
> thousandths of an inch,
Is that for a basically healthy wheel with one or two loose spokes or
for one where they are all so loose as to be losing their preload?
Or perhaps if they're all that loose the wheel will collapse anyway
making my question a red herring?
|
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