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Main
Date: 02 Sep 2007 10:14:58
From:
Subject: physics of bicycle rollers information?
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Can anyone point me towards some information about the physics of
bicycle rollers. By rollers I mean:
http://www.kreitler.com/product.php?section=product&item=rollers_4_5
I have been reading about the physics of a bike in motion, and why it
"stays up," but i was wondering if these same principles explain why
you can ride on cycling rollers and not fall over. A simple
explanation would be fine as well, with some keywords that I can
further research. Thanks.
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Date: 07 Sep 2007 12:39:49
From: Joe Riel
Subject: Re: physics of bicycle rollers information?
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"joseph.santaniello@gmail.com" <joseph.santaniello@gmail.com > writes:
> I suppose the fact you point out that leaning against a wall is not
> the same due to the CG plumb line may be the key to my
> misunderstanding of this. So leaning on a wall isn't a good way to
> simulate a leaned turn. Being stationary perpendicular to the slope of
> a steep hill (like on a velodrome straight) would be more analogous.
> So in that scenario, is there "flop" like when leaning against a wall?
> I have no veldrome handy to test. I've got a big plywood board I could
> pull out to play with, but it's windy and my wife thinks I'm crazy
> enough as it is.
Not perpendicular to the slope. Keep the bike perpendicular to level.
I tried that this morning using the (modest) slope on the transition
from driveway to street. However, my shift cables are such that they
apply a constant torque to the handlebars, which makes any measurement
impractical. Much of the resistance, with the bike not moving, is
due to scrubbing of the tire against the floor. That shouldn't
occur with bike moving.
--
Joe Riel
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Date: 07 Sep 2007 11:23:04
From: joseph.santaniello@gmail.com
Subject: Re: physics of bicycle rollers information?
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On Sep 7, 6:21 pm, jobst.bra...@stanfordalumni.org wrote:
> Joseph Santaniello writes:
> >>>>>> Gyroscopic forces only have a significant effect on bicycling
> >>>>>> when riding no-hands.
> >>>>> I was thinking it doesn't matter whether you're riding with
> >>>>> hands or no-hands on the bar, the gyroscopic forces would be the
> >>>>> same. And that would be proven when riding no-hands on rollers?
> >>>> They are the same and so small that hands on the bars override
> >>>> any effect they have. That is why many folks cannot ride
> >>>> no-hands. Just the transition of releasing the grip on the bars
> >>>> unstabilizes the bicycle.
> >>> I agree. I don't think gyroscopic forces have any bearing at all.
> >>> A caster wheel on a lunch cart goes straight not because of the
> >>> gyroscopic forces from the rotating wheel. This is also why a
> >>> bike goes straight when you walk it holding the saddle. The bike
> >>> self- rights as in the video you posted the link to because of the
> >>> trail and steering angle and how these combine to make the front
> >>> wheel flop to various steering angles for given angles of lean.
> >> I disagree. With no hands on the bars, any change in lean of the
> >> head tube causes gyroscopic steering. To sense how much this is,
> >> hold a rotating wheel in your hands by the axle and tilt it. After
> >> you try this, I don't think you will believe gyroscopic forces do
> >> not play a role in steering a bicycle without using the
> >> handlebars... walking a bicycle by holding the saddle, for
> >> instance.
> > I just did the spin-the-wheel-and-lean to feel the gyroscopic forces.
> > They are certainly perceptible, but I still think they are a
> > negligible component in no-hands riding.
> > Perhaps more significant in rider-less. If you sit on a bike and
> > prop yourself against a wall, and then lean the bike without hold
> > the bars, you will of course see that the bars flop toward the side
> > the bike is leaning. If you then try to forcibly straighten the bars
> > with your hands while still leaning the bike you will see that the
> > force from the lean is much greater than the gyroscopic ones even at
> > high speed. If the gyroscopic forces where that important, one
> > could ride a bike with a 90deg headtube no hands.
>
> Leaning against a wall is not analogous to riding no-hands, in which
> the CG plum line remains on center to the road, while small
> corrections are made by tilting the steering axis but not the
> rider-CG. These are made by swiveling the hips or swinging one knee
> outward. Try it.
I'm a big fan of adjusting my line with swinging my knees out. Heavy
legs!
I suppose the fact you point out that leaning against a wall is not
the same due to the CG plumb line may be the key to my
misunderstanding of this. So leaning on a wall isn't a good way to
simulate a leaned turn. Being stationary perpendicular to the slope of
a steep hill (like on a velodrome straight) would be more analogous.
So in that scenario, is there "flop" like when leaning against a wall?
I have no veldrome handy to test. I've got a big plywood board I could
pull out to play with, but it's windy and my wife thinks I'm crazy
enough as it is.
> http://www.sheldonbrown.com/brandt/gyro.html
>
>
>
> >>> The fact that these steering angles do not match up to the angle
> >>> of lean is the mechanism by which a bike self rights. That is to
> >>> say some of the bike's forward momentum is used up by the front
> >>> wheel scrubbing by flopping too far from the bike leaning making
> >>> the steering tighter than it "should" be for that angle of lean,
> >>> and thus correcting itself, until it goes too far the other way
> >>> until it settles into a equilibrium of sorts where these
> >>> corrections are minute and it looks like the bike is just going
> >>> straight. I suspect this ghost-rider type thing only works in a
> >>> speed range where the angle of lean and angle of steering from the
> >>> flop of that lean are not too out of whack. In other words don't
> >>> try this at 100mph.
> >> I don't believe your analysis of stability in the riderless bicycle
> >> is correct. There is no "scrubbing" and there are no discrete
> >> corrections or over-corrections. It is an analog process, a
> >> continuous system that only dithers if there is an external
> >> disturbance, such as the manual one in the video. Otherwise it is
> >> a stable continuum such as a pendulum at rest. It only dithers if
> >> disturbed.
> > Scrub wasn't the right word. If you lean a stationary bike, the
> > steering will turn in the direction of the lean without any gyroscopic
> > forces.
>
> As I said, this is not analogous to riding. When riding the rider and
> bicycle remain plumb to the contact of the tires to the road. The
> example you give does not do that.
>
>
>
> > If you then push the bike slowly you will see that the bike curves
> > along some radius. I contend that this radius is tighter that the
> > radius of the steady turn a bike at that same lean angle would take
> > at a steady speed. In other words, the steering is attempting to
> > make the bike turn too sharply for the lean angle of the bike. So
> > for a bike at speed, this makes the bike lean less, becoming more
> > upright. As the bike becomes more upright, the flopped steering
> > becomes more straight, yet still too tight for the lean so the
> > correction continues until the bike is fully upright, where it stays
> > until the bike starts falling to one side and the whole thing starts
> > again minutely oscillating back and forth. It's just you can't see
> > it unless the corrections are big like in the manual video.
> > Gyroscopic forces are not necessary to turn the steering, and even
> > if they do contribute to lean induced steering I think this has no
> > bearing on the self correcting of a bike, and maybe even makes it
> > worse!
>
> You are mixing modes of operation that do not occur. I think you
> might see that more easily if you ride (coast down a slight grade) and
> observe what facilitates steering no-hands and what is being leaned to
> do that.
>
> Jobst Brandt
Hmmm. It's getting too dark to ride today, but I'll try tommorow. I
suppose a way to test would be to use one of those clown bikes with
the tiny wheels. Can they be ridden no hands, or do they have
insufficeint gyroscopic force? I do notice that riding no hands with
my lightweight wheels is sketchier that riding with my regular wheels.
I guess that's proof right there isn't it?
Joseph
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Date: 07 Sep 2007 19:52:46
From:
Subject: Re: physics of bicycle rollers information?
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Joseph Santaniello writes:
>>>>>>>> Gyroscopic forces only have a significant effect on bicycling
>>>>>>>> when riding no-hands.
>>>>>>> I was thinking it doesn't matter whether you're riding with
>>>>>>> hands or no-hands on the bar, the gyroscopic forces would be
>>>>>>> the same. And that would be proven when riding no-hands on
>>>>>>> rollers?
>>>>>> They are the same and so small that hands on the bars override
>>>>>> any effect they have. That is why many folks cannot ride
>>>>>> no-hands. Just the transition of releasing the grip on the
>>>>>> bars unstabilizes the bicycle.
>>>>> I agree. I don't think gyroscopic forces have any bearing at
>>>>> all. A caster wheel on a lunch cart goes straight not because
>>>>> of the gyroscopic forces from the rotating wheel. This is also
>>>>> why a bike goes straight when you walk it holding the saddle.
>>>>> The bike self- rights as in the video you posted the link to
>>>>> because of the trail and steering angle and how these combine to
>>>>> make the front wheel flop to various steering angles for given
>>>>> angles of lean.
>>>> I disagree. With no hands on the bars, any change in lean of the
>>>> head tube causes gyroscopic steering. To sense how much this is,
>>>> hold a rotating wheel in your hands by the axle and tilt it.
>>>> After you try this, I don't think you will believe gyroscopic
>>>> forces do not play a role in steering a bicycle without using the
>>>> handlebars... walking a bicycle by holding the saddle, for
>>>> instance.
>>> I just did the spin-the-wheel-and-lean to feel the gyroscopic
>>> forces. They are certainly perceptible, but I still think they
>>> are a negligible component in no-hands riding.
>>> Perhaps more significant in rider-less. If you sit on a bike and
>>> prop yourself against a wall, and then lean the bike without hold
>>> the bars, you will of course see that the bars flop toward the
>>> side the bike is leaning. If you then try to forcibly straighten
>>> the bars with your hands while still leaning the bike you will see
>>> that the force from the lean is much greater than the gyroscopic
>>> ones even at high speed. If the gyroscopic forces where that
>>> important, one could ride a bike with a 90deg headtube no hands.
>> Leaning against a wall is not analogous to riding no-hands, in which
>> the CG plum line remains on center to the road, while small
>> corrections are made by tilting the steering axis but not the
>> rider-CG. These are made by swiveling the hips or swinging one knee
>> outward. Try it.
> I'm a big fan of adjusting my line with swinging my knees out. Heavy
> legs!
> I suppose the fact you point out that leaning against a wall is not
> the same due to the CG plumb line may be the key to my
> misunderstanding of this. So leaning on a wall isn't a good way to
> simulate a leaned turn. Being stationary perpendicular to the slope
> of a steep hill (like on a velodrome straight) would be more
> analogous. So in that scenario, is there "flop" like when leaning
> against a wall? I have no velodrome handy to test. I've got a big
> plywood board I could pull out to play with, but it's windy and my
> wife thinks I'm crazy enough as it is.
Stop already! We already mentioned the effect of riding on a
laterally sloped surface. That moves the center of pressure on the
tire a couple of mm to one side, a lean angle to compensate for this
asymmetry for a CG 4-feet above the ground of about 1.6 milli-radians.
This is smaller than the lean required by many improperly dished rear
wheels.
http://www.sheldonbrown.com/brandt/gyro.html
>>>>> The fact that these steering angles do not match up to the angle
>>>>> of lean is the mechanism by which a bike self rights. That is
>>>>> to say some of the bike's forward momentum is used up by the
>>>>> front wheel scrubbing by flopping too far from the bike leaning
>>>>> making the steering tighter than it "should" be for that angle
>>>>> of lean, and thus correcting itself, until it goes too far the
>>>>> other way until it settles into a equilibrium of sorts where
>>>>> these corrections are minute and it looks like the bike is just
>>>>> going straight. I suspect this ghost-rider type thing only
>>>>> works in a speed range where the angle of lean and angle of
>>>>> steering from the flop of that lean are not too out of whack.
>>>>> In other words don't try this at 100mph.
>>>> I don't believe your analysis of stability in the riderless
>>>> bicycle is correct. There is no "scrubbing" and there are no
>>>> discrete corrections or over-corrections. It is an analog
>>>> process, a continuous system that only dithers if there is an
>>>> external disturbance, such as the manual one in the video.
>>>> Otherwise it is a stable continuum such as a pendulum at rest.
>>>> It only dithers if disturbed.
>>> Scrub wasn't the right word. If you lean a stationary bike, the
>>> steering will turn in the direction of the lean without any
>>> gyroscopic forces.
>> As I said, this is not analogous to riding. When riding the rider
>> and bicycle remain plumb to the contact of the tires to the road.
>> The example you give does not do that.
>>> If you then push the bike slowly you will see that the bike curves
>>> along some radius. I contend that this radius is tighter that the
>>> radius of the steady turn a bike at that same lean angle would
>>> take at a steady speed. In other words, the steering is
>>> attempting to make the bike turn too sharply for the lean angle of
>>> the bike. So for a bike at speed, this makes the bike lean less,
>>> becoming more upright. As the bike becomes more upright, the
>>> flopped steering becomes more straight, yet still too tight for
>>> the lean so the correction continues until the bike is fully
>>> upright, where it stays until the bike starts falling to one side
>>> and the whole thing starts again minutely oscillating back and
>>> forth. It's just you can't see it unless the corrections are big
>>> like in the manual video. Gyroscopic forces are not necessary to
>>> turn the steering, and even if they do contribute to lean induced
>>> steering I think this has no bearing on the self correcting of a
>>> bike, and maybe even makes it worse!
>> You are mixing modes of operation that do not occur. I think you
>> might see that more easily if you ride (coast down a slight grade)
>> and observe what facilitates steering no-hands and what is being
>> leaned to do that.
> Hmmm. It's getting too dark to ride today, but I'll try tomorrow.
> I suppose a way to test would be to use one of those clown bikes
> with the tiny wheels. Can they be ridden no hands, or do they have
> insufficient gyroscopic force? I do notice that riding no hands
> with my lightweight wheels is sketchier that riding with my regular
> wheels. I guess that's proof right there isn't it?
I think you'll have a hard time riding no-hands with a tiny wheel.
First try to wheel the bike holding only onto the saddle and you'll
see what effect the small front wheel has.
Jobst Brandt
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Date: 07 Sep 2007 11:09:21
From: joseph.santaniello@gmail.com
Subject: Re: physics of bicycle rollers information?
|
On Sep 7, 6:02 pm, jobst.bra...@stanfordalumni.org wrote:
> Joseph Santaniello writes:
> >>>>> Gyroscopic forces only have a significant effect on bicycling when
> >>>>> riding no-hands:
> >>>> I was thinking it doesn't matter whether you're riding with hands or
> >>>> no-hands on the bar, the gyroscopic forces would be the same. And
> >>>> that would be proven when riding no-hands on rollers?
> >>> They are the same and sop small that hands on the bars override any
> >>> effect they have. That is why many folks cannot ride no-hands. Just
> >>> the transition of releasing the grip on the bars unstabilizes the
> >>> bicycle.
> >>>> Or another example would be riding no hands on a steep banked track,
> >>>> such as a velodrome. I believe the bike is no longer perpendicular
> >>>> to the pavement angle, and the gyroscopic forces is making that so.
> >>> If you consider the center of pressure in the contact of the tire to
> >>> the track, you'll note that it is a few mm from center on a 25mm tire,
> >>> not enough to cause any steering that is not readily countered by
> >>> leaning the bicycle ever so slightly. This is not gyroscopic action
> >>> that comes into play when changing the angle of lean when riding
> >>> no-hands.
>
> http://www.sheldonbrown.com/brandt/gyro.html
>
> >> One of the things that caught my attention from the article was the
> >> "ski-bob- bicycle that has no gyroscopic forces. A bicycle with no
> >> rotating parts. Wouldn't that be the same as riding rollers, since
> >> the rotation of the drums canceling out the rotation of the
> >> wheels? Therefore, that is why when one leans the bike on rollers,
> >> you'll topple over.
>
> The rollers run in fixed axes, and cannot have a gyroscopic effect,
> active or canceling because they don't tilt. I think we have already
> gone over that.
>
> > If indeed a ski-bob thingy can't be ridden no hands, I don't think
> > this is because it lacks gyroscopic forces, but because it lacks
> > point- like contact patches. The contact patch of a bike wheel is
> > so small the steering can easily pivot and the whole trail mechanism
> > is free to do it's thing. The front ski on a ski bike is long and
> > has so many places for forces to act on it in an inconsistent
> > manner, and so much drag, I think it would be like trying to ride a
> > bike no hands with a pitted headset that was too tight. Impossible,
> > but not because of gyroscopic forces.
>
> I think you are missing the effect that causes steering when riding
> no-hands or wheeling a bicycle while holding it by the saddle. If you
> try the exercise described in the FAQ item, you'll readily see that it
> is not trail that steers the bicycle but gyroscopic force.
I haven't tried the exercise, but I'll take your word for it. I don't
dispute that gyroscopic forces steer the wheel when leaned, just that
it is insignificant compared to the trail flopping. I think it is the
trail head-tube angle combo that is the major component. I'll bet one
of those ski-doo thingees could be walked no hands by holding the
saddle. In the FAQ item it says a plumb bob would hang down inline
with the seat tube during a constant turn. Is that really the case?
Isn't it somepalce between straight down and the seat tube?
> > An ice-skater can skate indefinitely on one skate. Same thing.
>
> An ice skater steers the single skate to remain in a plumb line with
> his CG. I think we are getting recursive. The FAQ item already
> discusses non rotating balance (ski-bob), basically a two runner
> skater.
Things seem to have gotten muddled in this thread a bit. No doubt from
my tortured logic! I thought that gyroscopic forces were being
presented as the means by which a bike is held in a stable upright
position, not that they were being presented as the mechanism by which
a turn is instigated. The ice skaketer was my way of showing that
keeping things upright doesn't require gyroscopic forces, but just as
you say keeping the skate (or bike) under the CG.
> > And you can lean on rollers. Just not for long, as you have to stop
> > doing so before you steer off the side.
>
> Leaning on rollers when riding no-hands is the same as on the road, a
> temporary steering motion. The bicycle and rider is not leaned. The
> bicycle is leaned while the rider (and CG) remains plumb. I think this
> was already mentioned, you cannot lean on rollers, there bing no
> lateral acceleration as in a curve on a road and rider momentum.
Ok I agree more or less with tha. But I think it is possible to get
the bike and rider to be plumb, albeit for a very short duration, on
rollers.
Joseph
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| | |
Date: 07 Sep 2007 19:32:34
From:
Subject: Re: physics of bicycle rollers information?
|
Joseph Santaniello writes:
>>>>>>> Gyroscopic forces only have a significant effect on bicycling
>>>>>>> when riding no-hands.
>>>>>> I was thinking it doesn't matter whether you're riding with
>>>>>> hands or no-hands on the bar, the gyroscopic forces would be
>>>>>> the same. And that would be proven when riding no-hands on
>>>>>> rollers?
>>>>> They are the same and sop small that hands on the bars override
>>>>> any effect they have. That is why many folks cannot ride
>>>>> no-hands. Just the transition of releasing the grip on the bars
>>>>> unstabilizes the bicycle.
>>>>>> Or another example would be riding no hands on a steep banked
>>>>>> track, such as a velodrome. I believe the bike is no longer
>>>>>> perpendicular to the pavement angle, and the gyroscopic forces
>>>>>> is making that so.
>>>>> If you consider the center of pressure in the contact of the
>>>>> tire to the track, you'll note that it is a few mm from center
>>>>> on a 25mm tire, not enough to cause any steering that is not
>>>>> readily countered by leaning the bicycle ever so slightly. This
>>>>> is not gyroscopic action that comes into play when changing the
>>>>> angle of lean when riding no-hands.
http://www.sheldonbrown.com/brandt/gyro.html
>>>> One of the things that caught my attention from the article was
>>>> the "ski-bob- bicycle that has no gyroscopic forces. A bicycle
>>>> with no rotating parts. Wouldn't that be the same as riding
>>>> rollers, since the rotation of the drums canceling out the
>>>> rotation of the wheels? Therefore, that is why when one leans
>>>> the bike on rollers, you'll topple over.
>> The rollers run in fixed axes, and cannot have a gyroscopic effect,
>> active or canceling because they don't tilt. I think we have
>> already gone over that.
>>> If indeed a ski-bob thingy can't be ridden no hands, I don't think
>>> this is because it lacks gyroscopic forces, but because it lacks
>>> point- like contact patches. The contact patch of a bike wheel is
>>> so small the steering can easily pivot and the whole trail
>>> mechanism is free to do it's thing. The front ski on a ski bike
>>> is long and has so many places for forces to act on it in an
>>> inconsistent manner, and so much drag, I think it would be like
>>> trying to ride a bike no hands with a pitted headset that was too
>>> tight. Impossible, but not because of gyroscopic forces.
>> I think you are missing the effect that causes steering when riding
>> no-hands or wheeling a bicycle while holding it by the saddle. If
>> you try the exercise described in the FAQ item, you'll readily see
>> that it is not trail that steers the bicycle but gyroscopic force.
> I haven't tried the exercise, but I'll take your word for it. I
> don't dispute that gyroscopic forces steer the wheel when leaned,
> just that it is insignificant compared to the trail flopping. I
> think it is the trail head-tube angle combo that is the major
> component.
You should explain what -art of that has an effect. From your
appreciation of trail with respect to bicycle lean, I don't think you
have the variables in order.
> I'll bet one of those ski-bob thingees could be walked no hands by
> holding the saddle.
You'd lose that bet. Steering a bicycle while walking next to it
holding it by the saddle makes use of gyroscopic forces that are not
present in a ski-bob. The trouble with your approach is that you find
lean-steer from static lean the same as the means by which a rider
steers when riding no-hands. The two are not the same effect.
> In the FAQ item it says a plumb bob would hang down in line with the
> seat tube during a constant turn. Is that really the case? Isn't
> it someplace between straight down and the seat tube?
Your wheel flop concept doesn't hold for a ridden bicycle, there being
no side forces from lean. When a rider and bicycle are leaned, the
load lies in the plane of the wheel. That the effect is small is
demonstrated by folks who like to stick out their knee in curves or
otherwise, lean off the bicycle, believing that this improves cornering
speed somehow. In review, look at the cornering shot:
http://tinyurl.com/p3f2y
>>> An ice-skater can skate indefinitely on one skate. Same thing.
>> An ice skater steers the single skate to remain in a plumb line with
>> his CG. I think we are getting recursive. The FAQ item already
>> discusses non rotating balance (ski-bob), basically a two runner
>> skater.
> Things seem to have gotten muddled in this thread a bit. No doubt
> from my tortured logic! I thought that gyroscopic forces were being
> presented as the means by which a bike is held in a stable upright
> position, not that they were being presented as the mechanism by
> which a turn is instigated.
Don't say that! It only reveals you haven't read the explanation of
what keeps the bicycle upright, the basis for much of this discussion.
> The ice skater was my way of showing that keeping things upright
> doesn't require gyroscopic forces, but just as you say keeping the
> skate (or bike) under the CG.
The ski-bob was my way of showing that keeping things upright doesn't
require gyroscopic forces, but just as you say keeping the skate (or
bike) under the CG in the FAQ item.
>>> And you can lean on rollers. Just not for long, as you have to
>>> stop doing so before you steer off the side.
>> Leaning on rollers when riding no-hands is the same as on the road, a
>> temporary steering motion. The bicycle and rider is not leaned. The
>> bicycle is leaned while the rider (and CG) remains plumb. I think this
>> was already mentioned, you cannot lean on rollers, there bing no
>> lateral acceleration as in a curve on a road and rider momentum.
> OK I agree more or less with that. But I think it is possible to get
> the bike and rider to be plumb, albeit for a very short duration, on
> rollers.
Jobst Brandt
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| |
Date: 07 Sep 2007 08:57:26
From: joseph.santaniello@gmail.com
Subject: Re: physics of bicycle rollers information?
|
On Sep 7, 5:19 pm, jobst.bra...@stanfordalumni.org wrote:
> Joseph Santaniello writes:
> >>>> Gyroscopic forces only have a significant effect on bicycling when
> >>>> riding no-hands.
> >>> I was thinking it doesn't matter whether you're riding with hands
> >>> or no-hands on the bar, the gyroscopic forces would be the same.
> >>> And that would be proven when riding no-hands on rollers?
> >> They are the same and so small that hands on the bars override any
> >> effect they have. That is why many folks cannot ride no-hands.
> >> Just the transition of releasing the grip on the bars unstabilizes
> >> the bicycle.
> > I agree. I don't think gyroscopic forces have any bearing at all.
> > A caster wheel on a lunch cart goes straight not because of the
> > gyroscopic forces from the rotating wheel. This is also why a bike
> > goes straight when you walk it holding the saddle. The bike self-
> > rights as in the video you posted the link to because of the trail
> > and steering angle and how these combine to make the front wheel
> > flop to various steering angles for given angles of lean.
>
> I disagree. With no hands on the bars, any change in lean of the head
> tube causes gyroscopic steering. To sens how much this is, hold a
> rotating wheel in your hands by the axle and tilt it. After you try
> this, I don't think you will believe gyroscopic forces do not play a
> role in steering a bicycle without using the handlebars... walking a
> bicycle by holding the saddle, for instance.
I just did the spin-the-wheel-and-lean to feel the gyroscopic forces.
They are certainly perceptible, but I still think they are a
negligable component in no-hands riding. Perhaps more significant in
rider-less. If you sit on a bike and prop yourself against a wall, and
then lean the bike without hold the bars, you will of course see that
the bars flop toward the side the bike is leaning. If you then try to
forcibly straigten the bars with your hands while still leaning the
bike you will see that the force from the lean is much greater than
the gyroscopic ones even at high speed. If the gyroscopic forces where
that important, one could ride a bike with a 90deg headtube no hands.
> http://www.sheldonbrown.com/brandt/gyro.html
>
> > The fact that these steering angles do not match up to the angle of
> > lean is the mechanism by which a bike self rights. That is to say
> > some of the bike's forward momentum is used up by the front wheel
> > scrubbing by flopping too far from the bike leaning making the
> > steering tighter than it "should" be for that angle of lean, and thus
> > correcting itself, until it goes too far the other way until it
> > settles into a equilibrium of sorts where these corrections are
> > minute and it looks like the bike is just going straight. I suspect
> > this ghost-rider type thing only works in a speed range where the
> > angle of lean and angle of steering from the flop of that lean are
> > not too out of whack. In other words don't try this at 100mph.
>
> I don't believe your analysis of stability in the riderless bicycle is
> correct. There is no "scrubbing" and there are no discrete
> corrections or over-corrections. It is an analog process, a
> continuous system that only dithers if there is an external
> disturbance, such as the manual one in the video. Otherwise it is a stable
> continuum such as a pendulum at rest. It only dithers if disturbed.
Scrub wasn't the right word. If you lean a stationary bike, the
steering will turn in the direction of the lean without any gyroscopic
forces. If you then push the bike slowly you will see that the bike
curves along some radius. I contend that this radius is tighter that
the radius of the steady turn a bike at that same lean angle would
take at a steady speed. In other words, the steering is attempting to
make the bike turn too sharply for the lean angle of the bike. So for
a bike at speed, this makes the bike lean less, becoming more upright.
As the bike becomes more upright, the flopped steering becomes more
straight, yet still too tight for the lean so the correction continues
until the bike is fully upright, where it stays until the bike starts
falling to one side and the whole thing starts again minutely
oscilating back and forth. It's just you can't see it unless the
corrections are big like in the manual video. Gyroscopic forces are
not necessary to turn the steering, and even if they do contibute to
lean induced steering I think this has no bearing on the self
correcting of a bike, and maybe even makes it worse!
Joseph
|
| | |
Date: 07 Sep 2007 16:21:44
From:
Subject: Re: physics of bicycle rollers information?
|
Joseph Santaniello writes:
>>>>>> Gyroscopic forces only have a significant effect on bicycling
>>>>>> when riding no-hands.
>>>>> I was thinking it doesn't matter whether you're riding with
>>>>> hands or no-hands on the bar, the gyroscopic forces would be the
>>>>> same. And that would be proven when riding no-hands on rollers?
>>>> They are the same and so small that hands on the bars override
>>>> any effect they have. That is why many folks cannot ride
>>>> no-hands. Just the transition of releasing the grip on the bars
>>>> unstabilizes the bicycle.
>>> I agree. I don't think gyroscopic forces have any bearing at all.
>>> A caster wheel on a lunch cart goes straight not because of the
>>> gyroscopic forces from the rotating wheel. This is also why a
>>> bike goes straight when you walk it holding the saddle. The bike
>>> self- rights as in the video you posted the link to because of the
>>> trail and steering angle and how these combine to make the front
>>> wheel flop to various steering angles for given angles of lean.
>> I disagree. With no hands on the bars, any change in lean of the
>> head tube causes gyroscopic steering. To sense how much this is,
>> hold a rotating wheel in your hands by the axle and tilt it. After
>> you try this, I don't think you will believe gyroscopic forces do
>> not play a role in steering a bicycle without using the
>> handlebars... walking a bicycle by holding the saddle, for
>> instance.
> I just did the spin-the-wheel-and-lean to feel the gyroscopic forces.
> They are certainly perceptible, but I still think they are a
> negligible component in no-hands riding.
> Perhaps more significant in rider-less. If you sit on a bike and
> prop yourself against a wall, and then lean the bike without hold
> the bars, you will of course see that the bars flop toward the side
> the bike is leaning. If you then try to forcibly straighten the bars
> with your hands while still leaning the bike you will see that the
> force from the lean is much greater than the gyroscopic ones even at
> high speed. If the gyroscopic forces where that important, one
> could ride a bike with a 90deg headtube no hands.
Leaning against a wall is not analogous to riding no-hands, in which
the CG plum line remains on center to the road, while small
corrections are made by tilting the steering axis but not the
rider-CG. These are made by swiveling the hips or swinging one knee
outward. Try it.
http://www.sheldonbrown.com/brandt/gyro.html
>>> The fact that these steering angles do not match up to the angle
>>> of lean is the mechanism by which a bike self rights. That is to
>>> say some of the bike's forward momentum is used up by the front
>>> wheel scrubbing by flopping too far from the bike leaning making
>>> the steering tighter than it "should" be for that angle of lean,
>>> and thus correcting itself, until it goes too far the other way
>>> until it settles into a equilibrium of sorts where these
>>> corrections are minute and it looks like the bike is just going
>>> straight. I suspect this ghost-rider type thing only works in a
>>> speed range where the angle of lean and angle of steering from the
>>> flop of that lean are not too out of whack. In other words don't
>>> try this at 100mph.
>> I don't believe your analysis of stability in the riderless bicycle
>> is correct. There is no "scrubbing" and there are no discrete
>> corrections or over-corrections. It is an analog process, a
>> continuous system that only dithers if there is an external
>> disturbance, such as the manual one in the video. Otherwise it is
>> a stable continuum such as a pendulum at rest. It only dithers if
>> disturbed.
> Scrub wasn't the right word. If you lean a stationary bike, the
> steering will turn in the direction of the lean without any gyroscopic
> forces.
As I said, this is not analogous to riding. When riding the rider and
bicycle remain plumb to the contact of the tires to the road. The
example you give does not do that.
> If you then push the bike slowly you will see that the bike curves
> along some radius. I contend that this radius is tighter that the
> radius of the steady turn a bike at that same lean angle would take
> at a steady speed. In other words, the steering is attempting to
> make the bike turn too sharply for the lean angle of the bike. So
> for a bike at speed, this makes the bike lean less, becoming more
> upright. As the bike becomes more upright, the flopped steering
> becomes more straight, yet still too tight for the lean so the
> correction continues until the bike is fully upright, where it stays
> until the bike starts falling to one side and the whole thing starts
> again minutely oscillating back and forth. It's just you can't see
> it unless the corrections are big like in the manual video.
> Gyroscopic forces are not necessary to turn the steering, and even
> if they do contribute to lean induced steering I think this has no
> bearing on the self correcting of a bike, and maybe even makes it
> worse!
You are mixing modes of operation that do not occur. I think you
might see that more easily if you ride (coast down a slight grade) and
observe what facilitates steering no-hands and what is being leaned to
do that.
Jobst Brandt
|
| |
Date: 07 Sep 2007 06:06:29
From: joseph.santaniello@gmail.com
Subject: Re: physics of bicycle rollers information?
|
On Sep 6, 8:55 pm, "Tom Nakashima" <t...@slac.stanford.edu > wrote:
> <jobst.bra...@stanfordalumni.org> wrote in message
>
> news:46e01b22$0$14126$742ec2ed@news.sonic.net...
>
>
>
> > Tom Nakashima writes:
>
> >>> Gyroscopic forces only have a significant effect on bicycling when
> >>> riding no-hands:
>
> >> I was thinking it doesn't matter whether you're riding with hands or
> >> no-hands on the bar, the gyroscopic forces would be the same. And
> >> that would be proven when riding no-hands on rollers?
>
> > They are the same and sop small that hands on the bars override any
> > effect they have. That is why many folks cannot ride no-hands. Just
> > the transition of releasing the grip on the bars unstabilizes the
> > bicycle.
>
> >> Or another example would be riding no hands on a steep banked track,
> >> such as a velodrome. I believe the bike is no longer perpendicular
> >> to the pavement angle, and the gyroscopic forces is making that so.
>
> > If you consider the center of pressure in the contact of the tire to
> > the track, you'll note that it is a few mm from center on a 25mm tire,
> > not enough to cause any steering that is not readily countered by
> > leaning the bicycle ever so slightly. This is not gyroscopic action
> > that comes into play when changing the angle of lean when riding
> > no-hands.
>
> >http://www.sheldonbrown.com/brandt/gyro.html
>
> > Jobst Brandt
>
> One of the things that caught my attention from the article was the
> "ski-bob-
> bicycle that has no gyroscopic forces. A bicycle with no rotating parts.
> Wouldn't that be the same as riding rollers, since the rotation of the drums
> cancelling out the rotation of the wheels? Therefore, that is why when one
> leans the bike on rollers, you'll topple over.
> -tom
If indeed a ski-bob thingy can't be ridden no hands, I don't think
this is because it lacks gyroscopic forces, but because it lacks point-
like contact patches. The contact patch of a bike wheel is so small
the steering can easily pivot and the whole trail mechanism is free to
do it's thing. The front ski on a ski bike is long and has so many
places for forces to act on it in an inconsistent manner, and so much
drag, I think it would be like trying to ride a bike no hands with a
pitted headset that was too tight. Impossible, but not because of
gyroscopic forces.
An ice-skater can skate indefinitely on one skate. Same thing.
And you can lean on rollers. Just not for long, as you have to stop
doing so before you steer off the side.
Joseph
|
| | |
Date: 07 Sep 2007 16:02:12
From:
Subject: Re: physics of bicycle rollers information?
|
Joseph Santaniello writes:
>>>>> Gyroscopic forces only have a significant effect on bicycling when
>>>>> riding no-hands:
>>>> I was thinking it doesn't matter whether you're riding with hands or
>>>> no-hands on the bar, the gyroscopic forces would be the same. And
>>>> that would be proven when riding no-hands on rollers?
>>> They are the same and sop small that hands on the bars override any
>>> effect they have. That is why many folks cannot ride no-hands. Just
>>> the transition of releasing the grip on the bars unstabilizes the
>>> bicycle.
>>>> Or another example would be riding no hands on a steep banked track,
>>>> such as a velodrome. I believe the bike is no longer perpendicular
>>>> to the pavement angle, and the gyroscopic forces is making that so.
>>> If you consider the center of pressure in the contact of the tire to
>>> the track, you'll note that it is a few mm from center on a 25mm tire,
>>> not enough to cause any steering that is not readily countered by
>>> leaning the bicycle ever so slightly. This is not gyroscopic action
>>> that comes into play when changing the angle of lean when riding
>>> no-hands.
http://www.sheldonbrown.com/brandt/gyro.html
>> One of the things that caught my attention from the article was the
>> "ski-bob- bicycle that has no gyroscopic forces. A bicycle with no
>> rotating parts. Wouldn't that be the same as riding rollers, since
>> the rotation of the drums canceling out the rotation of the
>> wheels? Therefore, that is why when one leans the bike on rollers,
>> you'll topple over.
The rollers run in fixed axes, and cannot have a gyroscopic effect,
active or canceling because they don't tilt. I think we have already
gone over that.
> If indeed a ski-bob thingy can't be ridden no hands, I don't think
> this is because it lacks gyroscopic forces, but because it lacks
> point- like contact patches. The contact patch of a bike wheel is
> so small the steering can easily pivot and the whole trail mechanism
> is free to do it's thing. The front ski on a ski bike is long and
> has so many places for forces to act on it in an inconsistent
> manner, and so much drag, I think it would be like trying to ride a
> bike no hands with a pitted headset that was too tight. Impossible,
> but not because of gyroscopic forces.
I think you are missing the effect that causes steering when riding
no-hands or wheeling a bicycle while holding it by the saddle. If you
try the exercise described in the FAQ item, you'll readily see that it
is not trail that steers the bicycle but gyroscopic force.
> An ice-skater can skate indefinitely on one skate. Same thing.
An ice skater steers the single skate to remain in a plumb line with
his CG. I think we are getting recursive. The FAQ item already
discusses non rotating balance (ski-bob), basically a two runner
skater.
> And you can lean on rollers. Just not for long, as you have to stop
> doing so before you steer off the side.
Leaning on rollers when riding no-hands is the same as on the road, a
temporary steering motion. The bicycle and rider is not leaned. The
bicycle is leaned while the rider (and CG) remains plumb. I think this
was already mentioned, you cannot lean on rollers, there bing no
lateral acceleration as in a curve on a road and rider momentum.
Jobst Brandt
|
| |
Date: 07 Sep 2007 05:58:53
From: joseph.santaniello@gmail.com
Subject: Re: physics of bicycle rollers information?
|
On Sep 6, 5:22 pm, jobst.bra...@stanfordalumni.org wrote:
> Tom Nakashima writes:
> >> Gyroscopic forces only have a significant effect on bicycling when
> >> riding no-hands:
> > I was thinking it doesn't matter whether you're riding with hands or
> > no-hands on the bar, the gyroscopic forces would be the same. And
> > that would be proven when riding no-hands on rollers?
>
> They are the same and sop small that hands on the bars override any
> effect they have. That is why many folks cannot ride no-hands. Just
> the transition of releasing the grip on the bars unstabilizes the
> bicycle.
I agree. I don't think gyroscopic forces have any bearing at all. A
castor wheel on a lunch cart goes straight not because of the
gyroscopic forces from the rotating wheel. This is also why a bike
goes straight when you walk it holding the saddle. The bike self-
rights as in the video you posted the link to because of the trail and
steering angle and how these combine to make the front wheel flop to
various steering angles for given angles of lean. The fact that these
steering angles do not match up to the angle of lean is the mechanism
by which a bike self rights. That is to say some of the bike's forward
momentum is used up by the front wheel scrubbing by flopping too far
from the bike leaning making the steering tigher than it "should" be
for that angle of lean, and thus correcting itself, until it goes too
far the other way until it settles into a equilibrium of sorts where
these corrections are minute and it looks like the bike is just going
straight. I suspect this ghost-rider type thing only works in a speed
range where the angle of lean and angle of steering from the flop of
that lean are not too out of whack. In other words don't try this at
100mph.
Joseph
|
| | |
Date: 07 Sep 2007 15:19:59
From:
Subject: Re: physics of bicycle rollers information?
|
Joseph Santaniello writes:
>>>> Gyroscopic forces only have a significant effect on bicycling when
>>>> riding no-hands.
>>> I was thinking it doesn't matter whether you're riding with hands
>>> or no-hands on the bar, the gyroscopic forces would be the same.
>>> And that would be proven when riding no-hands on rollers?
>> They are the same and so small that hands on the bars override any
>> effect they have. That is why many folks cannot ride no-hands.
>> Just the transition of releasing the grip on the bars unstabilizes
>> the bicycle.
> I agree. I don't think gyroscopic forces have any bearing at all.
> A caster wheel on a lunch cart goes straight not because of the
> gyroscopic forces from the rotating wheel. This is also why a bike
> goes straight when you walk it holding the saddle. The bike self-
> rights as in the video you posted the link to because of the trail
> and steering angle and how these combine to make the front wheel
> flop to various steering angles for given angles of lean.
I disagree. With no hands on the bars, any change in lean of the head
tube causes gyroscopic steering. To sens how much this is, hold a
rotating wheel in your hands by the axle and tilt it. After you try
this, I don't think you will believe gyroscopic forces do not play a
role in steering a bicycle without using the handlebars... walking a
bicycle by holding the saddle, for instance.
http://www.sheldonbrown.com/brandt/gyro.html
> The fact that these steering angles do not match up to the angle of
> lean is the mechanism by which a bike self rights. That is to say
> some of the bike's forward momentum is used up by the front wheel
> scrubbing by flopping too far from the bike leaning making the
> steering tighter than it "should" be for that angle of lean, and thus
> correcting itself, until it goes too far the other way until it
> settles into a equilibrium of sorts where these corrections are
> minute and it looks like the bike is just going straight. I suspect
> this ghost-rider type thing only works in a speed range where the
> angle of lean and angle of steering from the flop of that lean are
> not too out of whack. In other words don't try this at 100mph.
I don't believe your analysis of stability in the riderless bicycle is
correct. There is no "scrubbing" and there are no discrete
corrections or over-corrections. It is an analog process, a
continuous system that only dithers if there is an external
disturbance, such as the manual one in the video. Otherwise it is a stable
continuum such as a pendulum at rest. It only dithers if disturbed.
Jobst Brandt
|
| |
Date: 06 Sep 2007 23:46:58
From: joseph.santaniello@gmail.com
Subject: Re: physics of bicycle rollers information?
|
On Sep 7, 5:48 am, jobst.bra...@stanfordalumni.org wrote:
> Joseph Santaniello writes:
> >>>>>>> Is it because the gyroscope is pivoting on one point rather
> >>>>>>> than two?
> >>>>>> I have never tried rollers and have no feeling, nor any good
> >>>>>> idea either, of what you are talking about. But one thing I
> >>>>>> surely know. Any rigid body has one, and only can it have,
> >>>>>> instantaneous axis of rotation. So, no two simultaneous
> >>>>>> pivoting points, unless both on that very axis.
> >>>>> Sorry, actually when riding rollers, it's 3 points contact. Two
> >>>>> contact points on the rear, and one on the front. Take away the
> >>>>> belt that rotates the front rollers, and you're in trouble.
> >>>>> Very interesting.
> >>>> If the front wheel isn't rotating you can't steer. I think that
> >>>> is obvious and uninteresting.
> >>>> In effect, rollers have two points of contact, the two rear
> >>>> rollers being so close that any steering angle is insignificant
> >>>> leaving the effective contact of the rear wheel between the two
> >>>> rollers. Rear roller separation serves only to keep the bicycle
> >>>> from moving fore and aft and has no significance for steering
> >>>> (lateral control).
> >>> When riding straight ahead on rollers the wheels are essentially
> >>> perpendicular to the rollers. When one zig-zags or otherwise make
> >>> large corrections such that the wheels are no longer perpendicular
> >>> to the rollers I wonder how this affects rear steering? The
> >>> spacing of the rear patches changes and the location of the
> >>> patches seems to me that it would introduce some yaw forces.
> >>> Gravity is also trying to pull the wheel down between the rear
> >>> rollers and when the wheel is no longer perpendicular I think the
> >>> force of gravity and the offset patches would server to further
> >>> tend to apply a steering force the likes of which do not occur on
> >>> the road. I wonder how great these forces are.
> >> If the rear wheel is not perpendicular to the rollers (as seen from
> >> above) you will get two patches with shearing forces caused by the
> >> forward rotation of the drums, accompanied by the somewhat screechy
> >> sound of rubber slipping on the metal drum (I have never ridden
> >> rollers with PVC drums, so I don't know what that sounds like).
> >> If the front wheel is not perpendicular to the roller (as seen from
> >> above) it starts to try to slip down the roller because the
> >> steering trail pulls the contact patch backward and gravity does
> >> its thing, and the shearing force tries to drag the tire back up
> >> the slope. Of course, if the roller is set too far back, the wheel
> >> may try to slide down the front of the roller pulling the bike
> >> forward and possibly off the rear rollers.
> >> The narrow width of rollers limits the angle that can be achieved,
> >> however, which in turn limits these adverse effects.
> > It indeed limits them, but since the corrections (and presumably
> > forces) needed to keep upright riding rollers are small, I wonder
> > although slight, these things have a noticeable affect.
> >> Here's a thought experiment: it seems obvious that one could not
> >> ride rollers if the front drum was disengaged and the front wheel
> >> therefore did not turn, because you couldn't steer the contact
> >> patch under your center of gravity. Is it possible to "ride"
> >> rollers if only the front drum is turning (e.g. motorized) and the
> >> rear drums are stationary? My guess would be "yes," at least
> >> somewhat ridable.
> > About as easy as a skid. While a skid requires more concentration
> > to control that regular riding, it can be maintained more or less
> > indefinitely as long as you keep the rear wheel from washing out,
> > which wouldn't be a problem in the set-up you suggest.
>
> I suspect you have not tried this but the rear wheel rollers not
> turning means that the rear end will not follow the position of the
> front wheel as it traverses its roller, causing the bicycle to
> "cross-up". I suspect that is what you are referring to as a skid.
I meant that I presume controlling a bike on rollers where somehow the
rear wheel is not rotating is probably about as difficult to control
as a bike on the road (in a straight line) where the rear wheel is
locked by the brake. However a skid on the road is probably harder to
control as you have to avoid wash-out.
> > Another thought experiment (or a real one for anyone out there with
> > the equipment!) would be to try to ride a unicycle on the back
> > rollers to see whether the shearing forces on the back wheel would
> > amount to anything with any effect.
>
> That won't work because to keep upright in the fore and aft direction
> on a unicycle requires accelerating the contact patch to be beneath
> the CG. That is not possible with a fore and aft position fixed on
> rollers. Only lateral position can be altered and that isn't easy
> with reasonably spaced rollers by steering left and right.
>
> Jobst Brandt
That is true, but with some cheating (hands on the wall) to avoid
falling over forward or backward one could still test the shearing
forces.
Joseph
|
| |
Date: 06 Sep 2007 22:48:02
From: Joe Riel
Subject: Re: physics of bicycle rollers information?
|
jobst.brandt@stanfordalumni.org writes:
>> Another thought experiment (or a real one for anyone out there with
>> the equipment!) would be to try to ride a unicycle on the back
>> rollers to see whether the shearing forces on the back wheel would
>> amount to anything with any effect.
>
> That won't work because to keep upright in the fore and aft direction
> on a unicycle requires accelerating the contact patch to be beneath
> the CG. That is not possible with a fore and aft position fixed on
> rollers. Only lateral position can be altered and that isn't easy
> with reasonably spaced rollers by steering left and right.
If the rollers have suffient drag, or mass, to work against, then it
might be possible to shift the CG back and forth. Not sure about
that, though. Fortunately, I gave me giraffe unicycle to my
sister, so don't have to actually test this.
--
Joe Riel
|
| |
Date: 06 Sep 2007 13:29:19
From: joseph.santaniello@gmail.com
Subject: Re: physics of bicycle rollers information?
|
On Sep 6, 7:51 pm, Tim McNamara <tim...@bitstream.net > wrote:
> In article <1189064590.298161.166...@y42g2000hsy.googlegroups.com>,
>
>
>
> "joseph.santanie...@gmail.com" <joseph.santanie...@gmail.com> wrote:
> > On Sep 5, 11:45 pm, jobst.bra...@stanfordalumni.org wrote:
> > > Tom Nakashima writes:
> > > >>> Is it because the gyroscope is pivoting on one point rather
> > > >>> than two?
> > > >> I have never tried rollers and have no feeling, nor any good
> > > >> idea either, of what you are talking about. But one thing I
> > > >> surely know. Any rigid body has one, and only can it have,
> > > >> instantaneous axis of rotation. So, no two simultaneous pivoting
> > > >> points, unless both on that very axis.
> > > > Sorry, actually when riding rollers, it's 3 points contact. Two
> > > > contact points on the rear, and one on the front. Take away the
> > > > belt that rotates the front rollers, and you're in trouble. Very
> > > > interesting.
>
> > > If the front wheel isn't rotating you can't steer. I think that is
> > > obvious and uninteresting.
>
> > > In effect, rollers have two points of contact, the two rear rollers
> > > being so close that any steering angle is insignificant leaving the
> > > effective contact of the rear wheel between the two rollers. Rear
> > > roller separation serves only to keep the bicycle from moving fore
> > > and aft and has no significance for steering (lateral control).
>
> > When riding straight ahead on rollers the wheels are essentially
> > perpedicular to the rollers. When one zig-zags or otherwise make
> > large corrections such that the wheels are no longer perpendicular to
> > the rollers I wonder how this affects rear steering? The spacing of
> > the rear patches changes and the location of the patches seems to me
> > that it would introduce some yaw forces. Gravity is also trying to
> > pull the wheel down between the rear rollers and when the wheel is no
> > longer perpendicular I think the force of gravity and the offset
> > patches would server to further tend to apply a steering force the
> > likes of which do not occur on the road. I wonder how great these
> > forces are.
>
> If the rear wheel is not perpendicular to the rollers (as seen from
> above) you will get two patches with shearing forces caused by the
> forward rotation of the drums, accompanied by the somewhat screechy
> sound of rubber slipping on the metal drum (I have never ridden rollers
> with PVC drums, so I don't know what that sounds like).
>
> If the front wheel is not perpendicular to the roller (as seen from
> above) it starts to try to slip down the roller because the steering
> trail pulls the contact patch backwards and gravity does its thing, and
> the shearing force tries to drag the tire back up the slope. Of course,
> if the roller is set too far back, the wheel may try to slide down the
> front of the roller pulling the bike forward and possibly off the rear
> rollers.
>
> The narrow width of rollers limits the angle that can be achieved,
> however, which in turn limits these adverse effects.
It indeed limits them, but since the corrections (and presumably
forces) needed to keep upright riding rollers are small, I wonder
although slight, these things have a noticable affect.
> Here's a thought experiment: it seems obvious that one could not ride
> rollers if the front drum was disengaged and the front wheel therefore
> did not turn, because you couldn't steer the contact patch under your
> center of gravity. Is it possible to "ride" rollers if only the front
> drum is turning (e.g. motorized) and the rear drums are stationary? My
> guess would be "yes," at least somewhat ridable.
About as easy as a skid. While a skid requires more concentration to
controll that regular riding, it can be maintained more or less
indefinitely as long as you keep the rear wheel from washing out,
which wouldn't be a problem in the set-up you suggest.
Another thought experiment (or a real one for anyone out there with
the equipment!) would be to try to ride a unicycle on the back rollers
to see whether the shearing forces on the back wheel would amount to
anything with any effect.
Joseph
|
| | |
Date: 07 Sep 2007 03:48:28
From:
Subject: Re: physics of bicycle rollers information?
|
Joseph Santaniello writes:
>>>>>>> Is it because the gyroscope is pivoting on one point rather
>>>>>>> than two?
>>>>>> I have never tried rollers and have no feeling, nor any good
>>>>>> idea either, of what you are talking about. But one thing I
>>>>>> surely know. Any rigid body has one, and only can it have,
>>>>>> instantaneous axis of rotation. So, no two simultaneous
>>>>>> pivoting points, unless both on that very axis.
>>>>> Sorry, actually when riding rollers, it's 3 points contact. Two
>>>>> contact points on the rear, and one on the front. Take away the
>>>>> belt that rotates the front rollers, and you're in trouble.
>>>>> Very interesting.
>>>> If the front wheel isn't rotating you can't steer. I think that
>>>> is obvious and uninteresting.
>>>> In effect, rollers have two points of contact, the two rear
>>>> rollers being so close that any steering angle is insignificant
>>>> leaving the effective contact of the rear wheel between the two
>>>> rollers. Rear roller separation serves only to keep the bicycle
>>>> from moving fore and aft and has no significance for steering
>>>> (lateral control).
>>> When riding straight ahead on rollers the wheels are essentially
>>> perpendicular to the rollers. When one zig-zags or otherwise make
>>> large corrections such that the wheels are no longer perpendicular
>>> to the rollers I wonder how this affects rear steering? The
>>> spacing of the rear patches changes and the location of the
>>> patches seems to me that it would introduce some yaw forces.
>>> Gravity is also trying to pull the wheel down between the rear
>>> rollers and when the wheel is no longer perpendicular I think the
>>> force of gravity and the offset patches would server to further
>>> tend to apply a steering force the likes of which do not occur on
>>> the road. I wonder how great these forces are.
>> If the rear wheel is not perpendicular to the rollers (as seen from
>> above) you will get two patches with shearing forces caused by the
>> forward rotation of the drums, accompanied by the somewhat screechy
>> sound of rubber slipping on the metal drum (I have never ridden
>> rollers with PVC drums, so I don't know what that sounds like).
>> If the front wheel is not perpendicular to the roller (as seen from
>> above) it starts to try to slip down the roller because the
>> steering trail pulls the contact patch backward and gravity does
>> its thing, and the shearing force tries to drag the tire back up
>> the slope. Of course, if the roller is set too far back, the wheel
>> may try to slide down the front of the roller pulling the bike
>> forward and possibly off the rear rollers.
>> The narrow width of rollers limits the angle that can be achieved,
>> however, which in turn limits these adverse effects.
> It indeed limits them, but since the corrections (and presumably
> forces) needed to keep upright riding rollers are small, I wonder
> although slight, these things have a noticeable affect.
>> Here's a thought experiment: it seems obvious that one could not
>> ride rollers if the front drum was disengaged and the front wheel
>> therefore did not turn, because you couldn't steer the contact
>> patch under your center of gravity. Is it possible to "ride"
>> rollers if only the front drum is turning (e.g. motorized) and the
>> rear drums are stationary? My guess would be "yes," at least
>> somewhat ridable.
> About as easy as a skid. While a skid requires more concentration
> to control that regular riding, it can be maintained more or less
> indefinitely as long as you keep the rear wheel from washing out,
> which wouldn't be a problem in the set-up you suggest.
I suspect you have not tried this but the rear wheel rollers not
turning means that the rear end will not follow the position of the
front wheel as it traverses its roller, causing the bicycle to
"cross-up". I suspect that is what you are referring to as a skid.
> Another thought experiment (or a real one for anyone out there with
> the equipment!) would be to try to ride a unicycle on the back
> rollers to see whether the shearing forces on the back wheel would
> amount to anything with any effect.
That won't work because to keep upright in the fore and aft direction
on a unicycle requires accelerating the contact patch to be beneath
the CG. That is not possible with a fore and aft position fixed on
rollers. Only lateral position can be altered and that isn't easy
with reasonably spaced rollers by steering left and right.
Jobst Brandt
|
| | |
Date: 06 Sep 2007 14:41:03
From:
Subject: Re: physics of bicycle rollers information?
|
On Thu, 06 Sep 2007 13:29:19 -0700, "joseph.santaniello@gmail.com"
<joseph.santaniello@gmail.com > wrote:
[snip]
>Another thought experiment (or a real one for anyone out there with
>the equipment!) would be to try to ride a unicycle on the back rollers
>to see whether the shearing forces on the back wheel would amount to
>anything with any effect.
>
>Joseph
Dear Joseph,
Hmmm . . .
My immediate reaction is that a unicyclist would find riding on
rollers much, much more difficult.
The unicycle wheel would be trapped between the rear rollers and
couldn't move backwards and forwards, which is pretty much how
unicyclists balance.
Now I have to look for a video of some evil Chinese acrobat riding a
uncicyle on rollers, probably while juggling.
Cheers,
Carl Fogel
|
| | | |
Date: 07 Sep 2007 06:48:23
From: Tom Nakashima
Subject: Re: physics of bicycle rollers information?
|
<carlfogel@comcast.net > wrote in message
news:o2p0e3tb2ab3t2m66toh7ovlg2jti4drlv@4ax.com...
> On Thu, 06 Sep 2007 13:29:19 -0700, "joseph.santaniello@gmail.com"
> <joseph.santaniello@gmail.com> wrote:
>
> [snip]
>
>>Another thought experiment (or a real one for anyone out there with
>>the equipment!) would be to try to ride a unicycle on the back rollers
>>to see whether the shearing forces on the back wheel would amount to
>>anything with any effect.
>>
>>Joseph
>
> Dear Joseph,
>
> Hmmm . . .
>
> My immediate reaction is that a unicyclist would find riding on
> rollers much, much more difficult.
>
> The unicycle wheel would be trapped between the rear rollers and
> couldn't move backwards and forwards, which is pretty much how
> unicyclists balance.
>
> Now I have to look for a video of some evil Chinese acrobat riding a
> uncicyle on rollers, probably while juggling.
>
> Cheers,
>
> Carl Fogel
Carl,
when riding a unicycle, which I do on occasions, my weight is leaning
slightly forward and I'm pedaling in the forward direction. The only time
I'm balancing is when I need to motion forward and backwards.
I'll have to put my uni on rollers sometime to see if it could be done.
-tom
|
| | | |
Date: 06 Sep 2007 14:49:14
From:
Subject: Re: physics of bicycle rollers information?
|
On Thu, 06 Sep 2007 14:41:03 -0600, carlfogel@comcast.net wrote:
>On Thu, 06 Sep 2007 13:29:19 -0700, "joseph.santaniello@gmail.com"
><joseph.santaniello@gmail.com> wrote:
>
>[snip]
>
>>Another thought experiment (or a real one for anyone out there with
>>the equipment!) would be to try to ride a unicycle on the back rollers
>>to see whether the shearing forces on the back wheel would amount to
>>anything with any effect.
>>
>>Joseph
>
>Dear Joseph,
>
>Hmmm . . .
>
>My immediate reaction is that a unicyclist would find riding on
>rollers much, much more difficult.
>
>The unicycle wheel would be trapped between the rear rollers and
>couldn't move backwards and forwards, which is pretty much how
>unicyclists balance.
>
>Now I have to look for a video of some evil Chinese acrobat riding a
>uncicyle on rollers, probably while juggling.
>
>Cheers,
>
>Carl Fogel
One expert unicyclist is skeptical about riding on rollers:
"Of course a bicycle can balance with the wheel rotating but not
moving, and that's because the bike can still move side to side to
maintain balance. The problem for the unicyclist will be that the
wheel needs to go at least a little bit forward and back for the rider
to be able to maintain a balance above it."
But he doesn't quite rule it out:
"I don't think unicycling on rollers is completely impossible, but it
would be very difficult to do, and probably impossible to do in
combination with trying to get a workout of any kind."
http://www.unicycling.org/unicycling/hypermail/4093.html
Cheers,
Carl Fogel
|
| | | | |
Date: 06 Sep 2007 14:56:20
From:
Subject: Re: physics of bicycle rollers information?
|
On Thu, 06 Sep 2007 14:49:14 -0600, carlfogel@comcast.net wrote:
>On Thu, 06 Sep 2007 14:41:03 -0600, carlfogel@comcast.net wrote:
>
>>On Thu, 06 Sep 2007 13:29:19 -0700, "joseph.santaniello@gmail.com"
>><joseph.santaniello@gmail.com> wrote:
>>
>>[snip]
>>
>>>Another thought experiment (or a real one for anyone out there with
>>>the equipment!) would be to try to ride a unicycle on the back rollers
>>>to see whether the shearing forces on the back wheel would amount to
>>>anything with any effect.
>>>
>>>Joseph
>>
>>Dear Joseph,
>>
>>Hmmm . . .
>>
>>My immediate reaction is that a unicyclist would find riding on
>>rollers much, much more difficult.
>>
>>The unicycle wheel would be trapped between the rear rollers and
>>couldn't move backwards and forwards, which is pretty much how
>>unicyclists balance.
>>
>>Now I have to look for a video of some evil Chinese acrobat riding a
>>uncicyle on rollers, probably while juggling.
>>
>>Cheers,
>>
>>Carl Fogel
>
>One expert unicyclist is skeptical about riding on rollers:
>
>"Of course a bicycle can balance with the wheel rotating but not
>moving, and that's because the bike can still move side to side to
>maintain balance. The problem for the unicyclist will be that the
>wheel needs to go at least a little bit forward and back for the rider
>to be able to maintain a balance above it."
>
>But he doesn't quite rule it out:
>
>"I don't think unicycling on rollers is completely impossible, but it
>would be very difficult to do, and probably impossible to do in
>combination with trying to get a workout of any kind."
>
>http://www.unicycling.org/unicycling/hypermail/4093.html
>
>Cheers,
>
>Carl Fogel
Here's another unicycle-on-rollers thread:
http://www.unicyclist.com/forums/archive/index.php/t-8292.html
The consensus seems to be that rollers can't be ridden (unless you
hold onto a doorway), but treadmills can be ridden, even though
they're tricky.
Cheers,
Carl Fogel
|
| |
Date: 06 Sep 2007 00:43:10
From: joseph.santaniello@gmail.com
Subject: Re: physics of bicycle rollers information?
|
On Sep 5, 11:45 pm, jobst.bra...@stanfordalumni.org wrote:
> Tom Nakashima writes:
> >>> Is it because the gyroscope is pivoting on one point rather than two?
> >> I have never tried rollers and have no feeling, nor any good idea
> >> either, of what you are talking about. But one thing I surely know.
> >> Any rigid body has one, and only can it have, instantaneous axis of
> >> rotation.
> >> So, no two simultaneous pivoting points, unless both on that very
> >> axis.
> > Sorry, actually when riding rollers, it's 3 points contact. Two
> > contact points on the rear, and one on the front. Take away the
> > belt that rotates the front rollers, and you're in trouble.
> > Very interesting.
>
> If the front wheel isn't rotating you can't steer. I think that is
> obvious and uninteresting.
>
> In effect, rollers have two points of contact, the two rear rollers
> being so close that any steering angle is insignificant leaving the
> effective contact of the rear wheel between the two rollers. Rear
> roller separation serves only to keep the bicycle from moving fore and
> aft and has no significance for steering (lateral control).
>
> Jobst Brandt
When riding straight ahead on rollers the wheels are essentially
perpedicular to the rollers. When one zig-zags or otherwise make large
corrections such that the wheels are no longer perpendicular to the
rollers I wonder how this affects rear steering? The spacing of the
rear patches changes and the location of the patches seems to me that
it would introduce some yaw forces. Gravity is also trying to pull the
wheel down between the rear rollers and when the wheel is no longer
perpendicular I think the force of gravity and the offset patches
would server to further tend to apply a steering force the likes of
which do not occur on the road. I wonder how great these forces are.
Joseph
|
| | |
Date: 06 Sep 2007 12:51:35
From: Tim McNamara
Subject: Re: physics of bicycle rollers information?
|
In article <1189064590.298161.166790@y42g2000hsy.googlegroups.com >,
"joseph.santaniello@gmail.com" <joseph.santaniello@gmail.com > wrote:
> On Sep 5, 11:45 pm, jobst.bra...@stanfordalumni.org wrote:
> > Tom Nakashima writes:
> > >>> Is it because the gyroscope is pivoting on one point rather
> > >>> than two?
> > >> I have never tried rollers and have no feeling, nor any good
> > >> idea either, of what you are talking about. But one thing I
> > >> surely know. Any rigid body has one, and only can it have,
> > >> instantaneous axis of rotation. So, no two simultaneous pivoting
> > >> points, unless both on that very axis.
> > > Sorry, actually when riding rollers, it's 3 points contact. Two
> > > contact points on the rear, and one on the front. Take away the
> > > belt that rotates the front rollers, and you're in trouble. Very
> > > interesting.
> >
> > If the front wheel isn't rotating you can't steer. I think that is
> > obvious and uninteresting.
> >
> > In effect, rollers have two points of contact, the two rear rollers
> > being so close that any steering angle is insignificant leaving the
> > effective contact of the rear wheel between the two rollers. Rear
> > roller separation serves only to keep the bicycle from moving fore
> > and aft and has no significance for steering (lateral control).
>
> When riding straight ahead on rollers the wheels are essentially
> perpedicular to the rollers. When one zig-zags or otherwise make
> large corrections such that the wheels are no longer perpendicular to
> the rollers I wonder how this affects rear steering? The spacing of
> the rear patches changes and the location of the patches seems to me
> that it would introduce some yaw forces. Gravity is also trying to
> pull the wheel down between the rear rollers and when the wheel is no
> longer perpendicular I think the force of gravity and the offset
> patches would server to further tend to apply a steering force the
> likes of which do not occur on the road. I wonder how great these
> forces are.
If the rear wheel is not perpendicular to the rollers (as seen from
above) you will get two patches with shearing forces caused by the
forward rotation of the drums, accompanied by the somewhat screechy
sound of rubber slipping on the metal drum (I have never ridden rollers
with PVC drums, so I don't know what that sounds like).
If the front wheel is not perpendicular to the roller (as seen from
above) it starts to try to slip down the roller because the steering
trail pulls the contact patch backwards and gravity does its thing, and
the shearing force tries to drag the tire back up the slope. Of course,
if the roller is set too far back, the wheel may try to slide down the
front of the roller pulling the bike forward and possibly off the rear
rollers.
The narrow width of rollers limits the angle that can be achieved,
however, which in turn limits these adverse effects.
Here's a thought experiment: it seems obvious that one could not ride
rollers if the front drum was disengaged and the front wheel therefore
did not turn, because you couldn't steer the contact patch under your
center of gravity. Is it possible to "ride" rollers if only the front
drum is turning (e.g. motorized) and the rear drums are stationary? My
guess would be "yes," at least somewhat ridable.
|
| |
Date: 05 Sep 2007 11:43:35
From: sergio
Subject: Re: physics of bicycle rollers information?
|
On 5 Set, 16:55, "Tom Nakashima" <t...@slac.stanford.edu >
> Sorry, actually when riding rollers, it's 3 points contact.
> Two contact points on the rear, and one on the front.
Please, differentiate between a contact point and a pivoting point. No
more than one at a time for a rigid body in rotation about it.
Just a matter of wording?
Sergio
Pisa
|
| |
Date: 05 Sep 2007 03:06:09
From: joseph.santaniello@gmail.com
Subject: Re: physics of bicycle rollers information?
|
On Sep 5, 9:19 am, carlfo...@comcast.net wrote:
> On Wed, 05 Sep 2007 01:25:53 -0500, A Muzi <a...@yellowjersey.org>
> wrote:
>
>
>
> >> "A Muzi" <a...@yellowjersey.org> wrote
> >> I suspect the gyroscopic effect, minimal on the road,
> >>> becomes the primary effect on rollers.
>
> >Tom Nakashima wrote:
> >> I've watched a gyroscope, why is it that it has great leaning capabilities,
> >> while
> >> riding a bicycle does not and riding on rollers even less of a lean angle?
> >> Is it because the gyroscope is pivoting on one point rather than two?
>
> >I suspect the normal steering behavior of a bicycle is limited on
> >rollers. Look over the excellent 'Building An Unrideable Bicycle' for
> >background on 'normal'.
>
> >The motion of the rims/tires, which is trivial to a moving bicycle,
> >probably has some effect on the rollers where our arcs across the
> >pavement are absent. You can tell I'm speculating. Any other roller
> >riders care to comment? The bike definitely handles differently on
> >rollers and I'm grasping at why exactly. The net effect though is that
> >style which would be merely sloppy or inefficient on the road will dump
> >you off the rollers.
>
> Dear Andrew,
>
> Here's a theory.
>
> On pavement, you can do two things: lean into turns and steer the
> contact patch under your center of gravity.
>
> On rollers, you can't lean. If you do, you either fall down or else
> stop leaning and steer the contact patch back under your center of
> gravity as quick as you can.
>
> There's just no centripetal force, no actual turn on rollers, to allow
> the normal leaning that pavement provides.
>
> Cheers,
>
> Carl Fogel
There certainly is centripetal force, and you can lean for an actual
turn. It's just that these turns are limited in arc and duration by
the width of the rollers. But it does feel weird.
My rollers are heavy and thus keep spinning even after I stop pedaling
so I have had the chance to notice some odd things. When I pull one
foot out, and stand on that one foot like I were stopped with th ebike
leaned to one side, if the wheels are still turing the rear wheel has
a tendency to move away from the side the bike is leaning to. This
leads me to belive there is some weirdness with the 2 contact patches
in the back and their combined responses to leaning.
Joseph
|
| |
Date: 05 Sep 2007 01:14:03
From: sergio
Subject: Re: physics of bicycle rollers information?
|
On Sep 4, 4:12 pm, "Tom Nakashima" <t...@slac.stanford.edu > wrote:
> Is it because the gyroscope is pivoting on one point rather than two?
I have never tried rollers and have no feeling, nor any good idea
either, of what you are alking about. But one thing I surely know.
Any rigid body has one, and oinly can it have, instantaneous axis of
rotation.
So, no two simultaneous pivoting points, unless both on that very
axis.
Sergio
Pisa
|
| | |
Date: 05 Sep 2007 07:55:01
From: Tom Nakashima
Subject: Re: physics of bicycle rollers information?
|
"sergio" <servadio@df.unipi.it > wrote in message
news:1188980043.388965.109340@w3g2000hsg.googlegroups.com...
> On Sep 4, 4:12 pm, "Tom Nakashima" <t...@slac.stanford.edu> wrote:
>> Is it because the gyroscope is pivoting on one point rather than two?
>
> I have never tried rollers and have no feeling, nor any good idea
> either, of what you are alking about. But one thing I surely know.
> Any rigid body has one, and oinly can it have, instantaneous axis of
> rotation.
> So, no two simultaneous pivoting points, unless both on that very
> axis.
>
> Sergio
> Pisa
>
Sorry, actually when riding rollers, it's 3 points contact.
Two contact points on the rear, and one on the front.
Take away the belt that rotates the front rollers, and you're in trouble.
Very interesting.
-tom
|
| | | |
Date: 05 Sep 2007 21:45:14
From:
Subject: Re: physics of bicycle rollers information?
|
Tom Nakashima writes:
>>> Is it because the gyroscope is pivoting on one point rather than two?
>> I have never tried rollers and have no feeling, nor any good idea
>> either, of what you are talking about. But one thing I surely know.
>> Any rigid body has one, and only can it have, instantaneous axis of
>> rotation.
>> So, no two simultaneous pivoting points, unless both on that very
>> axis.
> Sorry, actually when riding rollers, it's 3 points contact. Two
> contact points on the rear, and one on the front. Take away the
> belt that rotates the front rollers, and you're in trouble.
> Very interesting.
If the front wheel isn't rotating you can't steer. I think that is
obvious and uninteresting.
In effect, rollers have two points of contact, the two rear rollers
being so close that any steering angle is insignificant leaving the
effective contact of the rear wheel between the two rollers. Rear
roller separation serves only to keep the bicycle from moving fore and
aft and has no significance for steering (lateral control).
Jobst Brandt
|
| |
Date: 04 Sep 2007 12:50:25
From: joseph.santaniello@gmail.com
Subject: Re: physics of bicycle rollers information?
|
On Sep 4, 8:51 am, A Muzi <a...@yellowjersey.org > wrote:
> >> Its the same effect except you must visually keep track of position on
> >> the rollers. See:
> >>http://www.sheldonbrown.com/brandt/gyro.html
> >> Jobst Brandt
> Chocobot wrote:
> > Thanks, I had read this previously, but it didn't seem to answer my
> > question. If I am reading this write, the act of moving forward has
> > nothing to do with the riders ability to balance the bike, that is why
> > one can ride on a set of rollers and still stay upright? However,
> > moving forward does help to keep the front wheel straight?
>
> > On another note, here is a video of someone people attempting
> > ridiculous tricks on rollers. At one point someone tries to do a skid
> > (as in on a track bike) on the rollers, i think this proves the point
> > that there is a little to zero forward momentum, and "rolling off"
> > these things pretty much not possible.
>
> > Also, one last question. I had my headphones plugged into my computer
> > while riding on the rollers and I was given a very startling
> > electrical shock, where is that energy coming from? my bike is
> > totally aluminum.
>
> Even I can ride no-hands, change a jersey and do a jump-to-floor to
> finish, these are not difficult things to learn. I'd even say that after
> you've ridden rollers for twenty minutes _anything_ to break the boredom
> is a good adventure.
Jump to floor sounds like fun! As far as stability for no-handed goes,
it is important to have rollers that are adjusted to the wheelbase of
the bike. As most rollers are not infinitely adjustable, some bike/
roller combos may be more stable than others. As for boredome
breakers, I like lane-changes on my rollers. I try to ride as close to
one edge as I can and randomly zig over to the other side as fast as I
dare. I try to zoom all the way over so I end up exactly at the
opposite edge without having to do any adjustments. Another fun thing
is to have peices of tape making lanes you can try to ride in and on.
> Yes static electricity can build up while riding. Like rubbing a nylon
> comb across a sweater.
>
> I think the way a bike rides on rollers is perhaps different from actual
> pavement cycling. I suspect the gyroscopic effect, minimal on the road,
> becomes the primary effect on rollers. Riding rollers teaches good
> riding habits quickly and subliminally. Spinning smoothly, not keeping a
> death grip on the handlebars, being relaxed on the bike all keep the
> bike upright and smooth.
I think there is some geometric differences with the 2 contact patches
in tha back and their relative distance to each other that affects how
rollers feel differnt as well. I think this is one of the reasons
standing is so difficult; the rear steers in an unusual way when the
bike leans by any significant degree. When I stand on the road I can
rock the bike quite a bit still keeping a very straight line. Standing
on the rollers I need to keep the bike much more upright if I want to
not crash.
> Those unfamiliar with rollers expect that riding off will shoot the bike
> through the plaster at 25mph. Since only the rims and tires are moving,
> you merely get a small skid on the floor as the bike falls over. (proper
> jumps require a burst of muscle to move the bike across the room instead
> of falling on the floor)
>
I think I'll try that one in the grass first...
Joseph
|
| |
Date: 04 Sep 2007 18:39:32
From: zencycle
Subject: Re: physics of bicycle rollers information?
|
On Sep 4, 10:42 am, Paul Myron Hobson <phob...@gatech.edu > wrote:
> Tom Nakashima wrote:
> > "A Muzi" <a...@yellowjersey.org> wrote in message
> >news:13dq02fdkja1l72@corp.supernews.com...
> > I suspect the gyroscopic effect, minimal on the road,
> >> becomes the primary effect on rollers. Andrew Muzi
> >>www.yellowjersey.org
> >> Open every day since 1 April, 1971
>
> > I've watched a gyroscope, why is it that it has great leaning capabilities,
> > while
> > riding a bicycle does not and riding on rollers even less of a lean angle?
> > Is it because the gyroscope is pivoting on one point rather than two?
> > -tom
>
> The gyroscopic moments of a rotating bicycle wheel are very small
> compared to the moment of the weight of the cyclist while leaning.
>
> \\paul
Besides, the gyro has a fixed point of resistance. A bike on rollers
will 'slide' since the vector force of the leaning tire against the
smooth drum will push it away from the direction of the lean. The
extremely low rolling resistance of the smooth drum against the tire
doesn't provide enough opposing force to counter the force of gravity.
If you lean on rollers, you have to slightly turn the front wheel in
the _same_ direction as the lean, which is not only counter intuitive
to normal bicycle handling technique, but also exceptionally difficult
to perform - try to lean a bike to the right while turning left.
Outside, the resistance of the rubber against the earth or pavement
provides enough opposing force that it's easy to compensate will small
steering motions. You'd have the same problem if you were to ride on a
polished aluminum floor, and also why it's nearly impossible to ride
on ice - you lean, you slide. FWIW, get a mag loader for your rollers.
The added resistance makes it much easier to learn to stay up.
|
| |
Date: 03 Sep 2007 08:21:27
From: Chocobot
Subject: Re: physics of bicycle rollers information?
|
>
> Its the same effect except you must visually keep track of position on
> the rollers. See:
>
> http://www.sheldonbrown.com/brandt/gyro.html
>
> Jobst Brandt
Thanks, I had read this previously, but it didn't seem to answer my
question. If I am reading this write, the act of moving forward has
nothing to do with the riders ability to balance the bike, that is why
one can ride on a set of rollers and still stay upright? However,
moving forward does help to keep the front wheel straight?
On another note, here is a video of someone people attempting
ridiculous tricks on rollers. At one point someone tries to do a skid
(as in on a track bike) on the rollers, i think this proves the point
that there is a little to zero forward momentum, and "rolling off"
these things pretty much not possible.
Also, one last question. I had my headphones plugged into my computer
while riding on the rollers and I was given a very startling
electrical shock, where is that energy coming from? my bike is
totally aluminum.
|
| | |
Date: 04 Sep 2007 01:51:33
From: A Muzi
Subject: Re: physics of bicycle rollers information?
|
>> Its the same effect except you must visually keep track of position on
>> the rollers. See:
>> http://www.sheldonbrown.com/brandt/gyro.html
>> Jobst Brandt
Chocobot wrote:
> Thanks, I had read this previously, but it didn't seem to answer my
> question. If I am reading this write, the act of moving forward has
> nothing to do with the riders ability to balance the bike, that is why
> one can ride on a set of rollers and still stay upright? However,
> moving forward does help to keep the front wheel straight?
>
> On another note, here is a video of someone people attempting
> ridiculous tricks on rollers. At one point someone tries to do a skid
> (as in on a track bike) on the rollers, i think this proves the point
> that there is a little to zero forward momentum, and "rolling off"
> these things pretty much not possible.
>
> Also, one last question. I had my headphones plugged into my computer
> while riding on the rollers and I was given a very startling
> electrical shock, where is that energy coming from? my bike is
> totally aluminum.
Even I can ride no-hands, change a jersey and do a jump-to-floor to
finish, these are not difficult things to learn. I'd even say that after
you've ridden rollers for twenty minutes _anything_ to break the boredom
is a good adventure.
Yes static electricity can build up while riding. Like rubbing a nylon
comb across a sweater.
I think the way a bike rides on rollers is perhaps different from actual
pavement cycling. I suspect the gyroscopic effect, minimal on the road,
becomes the primary effect on rollers. Riding rollers teaches good
riding habits quickly and subliminally. Spinning smoothly, not keeping a
death grip on the handlebars, being relaxed on the bike all keep the
bike upright and smooth.
Those unfamiliar with rollers expect that riding off will shoot the bike
through the plaster at 25mph. Since only the rims and tires are moving,
you merely get a small skid on the floor as the bike falls over. (proper
jumps require a burst of muscle to move the bike across the room instead
of falling on the floor)
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
|
| | | |
Date: 06 Sep 2007 14:05:54
From: joseph.santaniello@gmail.com
Subject: Re: physics of bicycle rollers information?
|
On Sep 6, 10:56 pm, carlfo...@comcast.net wrote:
> On Thu, 06 Sep 2007 14:49:14 -0600, carlfo...@comcast.net wrote:
> >On Thu, 06 Sep 2007 14:41:03 -0600, carlfo...@comcast.net wrote:
>
> >>On Thu, 06 Sep 2007 13:29:19 -0700, "joseph.santanie...@gmail.com"
> >><joseph.santanie...@gmail.com> wrote:
>
> >>[snip]
>
> >>>Another thought experiment (or a real one for anyone out there with
> >>>the equipment!) would be to try to ride a unicycle on the back rollers
> >>>to see whether the shearing forces on the back wheel would amount to
> >>>anything with any effect.
>
> >>>Joseph
>
> >>Dear Joseph,
>
> >>Hmmm . . .
>
> >>My immediate reaction is that a unicyclist would find riding on
> >>rollers much, much more difficult.
>
> >>The unicycle wheel would be trapped between the rear rollers and
> >>couldn't move backwards and forwards, which is pretty much how
> >>unicyclists balance.
>
> >>Now I have to look for a video of some evil Chinese acrobat riding a
> >>uncicyle on rollers, probably while juggling.
>
> >>Cheers,
>
> >>Carl Fogel
>
> >One expert unicyclist is skeptical about riding on rollers:
>
> >"Of course a bicycle can balance with the wheel rotating but not
> >moving, and that's because the bike can still move side to side to
> >maintain balance. The problem for the unicyclist will be that the
> >wheel needs to go at least a little bit forward and back for the rider
> >to be able to maintain a balance above it."
>
> >But he doesn't quite rule it out:
>
> >"I don't think unicycling on rollers is completely impossible, but it
> >would be very difficult to do, and probably impossible to do in
> >combination with trying to get a workout of any kind."
>
> >http://www.unicycling.org/unicycling/hypermail/4093.html
>
> >Cheers,
>
> >Carl Fogel
>
> Here's another unicycle-on-rollers thread:
>
> http://www.unicyclist.com/forums/archive/index.php/t-8292.html
>
> The consensus seems to be that rollers can't be ridden (unless you
> hold onto a doorway), but treadmills can be ridden, even though
> they're tricky.
>
> Cheers,
>
> Carl Fogel
While it may be impossible to ride a unicycle on rollers, one could be
used to get a feel for how strong these shearing forces are when the
wheel gets non-perpendicular. You could also find out how far from
perpendicular one would need to be for them to have any appeciable
effect. And the folks who thought you were crazy enough to ride
rollers in the first place or to even have a unicycle would be
vindicated.
Joseph
|
| | | |
Date: 06 Sep 2007 14:02:53
From: joseph.santaniello@gmail.com
Subject: Re: physics of bicycle rollers information?
|
On Sep 6, 10:56 pm, carlfo...@comcast.net wrote:
> On Thu, 06 Sep 2007 14:49:14 -0600, carlfo...@comcast.net wrote:
> >On Thu, 06 Sep 2007 14:41:03 -0600, carlfo...@comcast.net wrote:
>
> >>On Thu, 06 Sep 2007 13:29:19 -0700, "joseph.santanie...@gmail.com"
> >><joseph.santanie...@gmail.com> wrote:
>
> >>[snip]
>
> >>>Another thought experiment (or a real one for anyone out there with
> >>>the equipment!) would be to try to ride a unicycle on the back rollers
> >>>to see whether the shearing forces on the back wheel would amount to
> >>>anything with any effect.
>
> >>>Joseph
>
> >>Dear Joseph,
>
> >>Hmmm . . .
>
> >>My immediate reaction is that a unicyclist would find riding on
> >>rollers much, much more difficult.
>
> >>The unicycle wheel would be trapped between the rear rollers and
> >>couldn't move backwards and forwards, which is pretty much how
> >>unicyclists balance.
>
> >>Now I have to look for a video of some evil Chinese acrobat riding a
> >>uncicyle on rollers, probably while juggling.
>
> >>Cheers,
>
> >>Carl Fogel
>
> >One expert unicyclist is skeptical about riding on rollers:
>
> >"Of course a bicycle can balance with the wheel rotating but not
> >moving, and that's because the bike can still move side to side to
> >maintain balance. The problem for the unicyclist will be that the
> >wheel needs to go at least a little bit forward and back for the rider
> >to be able to maintain a balance above it."
>
> >But he doesn't quite rule it out:
>
> >"I don't think unicycling on rollers is completely impossible, but it
> >would be very difficult to do, and probably impossible to do in
> >combination with trying to get a workout of any kind."
>
> >http://www.unicycling.org/unicycling/hypermail/4093.html
>
> >Cheers,
>
> >Carl Fogel
>
> Here's another unicycle-on-rollers thread:
>
> http://www.unicyclist.com/forums/archive/index.php/t-8292.html
>
> The consensus seems to be that rollers can't be ridden (unless you
> hold onto a doorway), but treadmills can be ridden, even though
> they're tricky.
>
> Cheers,
>
> Carl Fogel
What about a bike on a treadmill? Fixed gear for better speed control
is they way I'd go.
Joseph
|
| | | |
Date: 04 Sep 2007 07:12:37
From: Tom Nakashima
Subject: Re: physics of bicycle rollers information?
|
"A Muzi" <am@yellowjersey.org > wrote in message
news:13dq02fdkja1l72@corp.supernews.com...
I suspect the gyroscopic effect, minimal on the road,
> becomes the primary effect on rollers. Andrew Muzi
> www.yellowjersey.org
> Open every day since 1 April, 1971
I've watched a gyroscope, why is it that it has great leaning capabilities,
while
riding a bicycle does not and riding on rollers even less of a lean angle?
Is it because the gyroscope is pivoting on one point rather than two?
-tom
|
| | | | |
Date: 05 Sep 2007 01:25:53
From: A Muzi
Subject: Re: physics of bicycle rollers information?
|
> "A Muzi" <am@yellowjersey.org> wrote
> I suspect the gyroscopic effect, minimal on the road,
>> becomes the primary effect on rollers.
Tom Nakashima wrote:
> I've watched a gyroscope, why is it that it has great leaning capabilities,
> while
> riding a bicycle does not and riding on rollers even less of a lean angle?
> Is it because the gyroscope is pivoting on one point rather than two?
I suspect the normal steering behavior of a bicycle is limited on
rollers. Look over the excellent 'Building An Unrideable Bicycle' for
background on 'normal'.
The motion of the rims/tires, which is trivial to a moving bicycle,
probably has some effect on the rollers where our arcs across the
pavement are absent. You can tell I'm speculating. Any other roller
riders care to comment? The bike definitely handles differently on
rollers and I'm grasping at why exactly. The net effect though is that
style which would be merely sloppy or inefficient on the road will dump
you off the rollers.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
|
| | | | | |
Date: 05 Sep 2007 08:43:21
From: Tim McNamara
Subject: Re: physics of bicycle rollers information?
|
In article <13dsitue55letc2@corp.supernews.com >,
A Muzi <am@yellowjersey.org > wrote:
> > "A Muzi" <am@yellowjersey.org> wrote
> > I suspect the gyroscopic effect, minimal on the road,
> >> becomes the primary effect on rollers.
>
> Tom Nakashima wrote:
> > I've watched a gyroscope, why is it that it has great leaning
> > capabilities, while riding a bicycle does not and riding on rollers
> > even less of a lean angle? Is it because the gyroscope is pivoting
> > on one point rather than two?
>
> I suspect the normal steering behavior of a bicycle is limited on
> rollers. Look over the excellent 'Building An Unrideable Bicycle'
> for background on 'normal'.
>
> The motion of the rims/tires, which is trivial to a moving bicycle,
> probably has some effect on the rollers where our arcs across the
> pavement are absent. You can tell I'm speculating. Any other roller
> riders care to comment? The bike definitely handles differently on
> rollers and I'm grasping at why exactly. The net effect though is
> that style which would be merely sloppy or inefficient on the road
> will dump you off the rollers.
I think that bikes handle different on rollers for at least a couple of
reasons. One of them is that the rear wheel has two contact patches
rather than one which restrains the bike from moving fore and aft under
the rider's center of gravity (which is maybe the root of one of the
benefits of roller riding- developing a smoother style). The other is
the slope of the front roller- as the wheel turns from side to side, it
slips downhill because the rake of the fork pulls the contact patch
backwards. At the same time the rotation of the roller is trying to
drag the wheel forwards and uphill.
|
| | | | | |
Date: 05 Sep 2007 01:19:02
From:
Subject: Re: physics of bicycle rollers information?
|
On Wed, 05 Sep 2007 01:25:53 -0500, A Muzi <am@yellowjersey.org >
wrote:
>> "A Muzi" <am@yellowjersey.org> wrote
>> I suspect the gyroscopic effect, minimal on the road,
>>> becomes the primary effect on rollers.
>
>Tom Nakashima wrote:
>> I've watched a gyroscope, why is it that it has great leaning capabilities,
>> while
>> riding a bicycle does not and riding on rollers even less of a lean angle?
>> Is it because the gyroscope is pivoting on one point rather than two?
>
>I suspect the normal steering behavior of a bicycle is limited on
>rollers. Look over the excellent 'Building An Unrideable Bicycle' for
>background on 'normal'.
>
>The motion of the rims/tires, which is trivial to a moving bicycle,
>probably has some effect on the rollers where our arcs across the
>pavement are absent. You can tell I'm speculating. Any other roller
>riders care to comment? The bike definitely handles differently on
>rollers and I'm grasping at why exactly. The net effect though is that
>style which would be merely sloppy or inefficient on the road will dump
>you off the rollers.
Dear Andrew,
Here's a theory.
On pavement, you can do two things: lean into turns and steer the
contact patch under your center of gravity.
On rollers, you can't lean. If you do, you either fall down or else
stop leaning and steer the contact patch back under your center of
gravity as quick as you can.
There's just no centripetal force, no actual turn on rollers, to allow
the normal leaning that pavement provides.
Cheers,
Carl Fogel
|
| | | | | | |
Date: 05 Sep 2007 13:37:04
From: A Muzi
Subject: Re: physics of bicycle rollers information?
|
>>> "A Muzi" <am@yellowjersey.org> wrote
>>> I suspect the gyroscopic effect, minimal on the road,
>>>> becomes the primary effect on rollers.
>> Tom Nakashima wrote:
>>> I've watched a gyroscope, why is it that it has great leaning capabilities,
>>> while
>>> riding a bicycle does not and riding on rollers even less of a lean angle?
>>> Is it because the gyroscope is pivoting on one point rather than two?
> A Muzi <am@yellowjersey.org> wrote:
>> I suspect the normal steering behavior of a bicycle is limited on
>> rollers. Look over the excellent 'Building An Unrideable Bicycle' for
>> background on 'normal'.
>> The motion of the rims/tires, which is trivial to a moving bicycle,
>> probably has some effect on the rollers where our arcs across the
>> pavement are absent. You can tell I'm speculating. Any other roller
>> riders care to comment? The bike definitely handles differently on
>> rollers and I'm grasping at why exactly. The net effect though is that
>> style which would be merely sloppy or inefficient on the road will dump
>> you off the rollers.
carlfogel@comcast.net wrote:
> Here's a theory.
> On pavement, you can do two things: lean into turns and steer the
> contact patch under your center of gravity.
> On rollers, you can't lean. If you do, you either fall down or else
> stop leaning and steer the contact patch back under your center of
> gravity as quick as you can.
> There's just no centripetal force, no actual turn on rollers, to allow
> the normal leaning that pavement provides.
Yes that's right.
But it's magnitudes harder to trackstand on rollers with the wheels not
turning.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
|
| | | | | | | |
Date: 05 Sep 2007 21:53:32
From:
Subject: Re: physics of bicycle rollers information?
|
Andrew Muzi writes:
>>>>> I suspect the gyroscopic effect, minimal on the road, becomes
>>>>> the primary effect on rollers.
>>>> I've watched a gyroscope, why is it that it has great leaning
>>>> capabilities, while riding a bicycle does not and riding on
>>>> rollers even less of a lean angle? Is it because the gyroscope
>>>> is pivoting on one point rather than two?
I think a toy gyroscope is hard to compare to a bicycle, where
gyroscopic forces play no role in keeping the bicycle upright, but
rather, are used to ride no-hands at best. The toy gyroscope has all
its significant mass in its rotor while the bicycle has almost no
significant mass IN its rotor (front wheel).
>>> I suspect the normal steering behavior of a bicycle is limited on
>>> rollers. Look over the excellent 'Building An Unrideable Bicycle'
>>> for background on 'normal'.
>>> The motion of the rims/tires, which is trivial to a moving
>>> bicycle, probably has some effect on the rollers where our arcs
>>> across the pavement are absent. You can tell I'm speculating.
>>> Any other roller riders care to comment? The bike definitely
>>> handles differently on rollers and I'm grasping at why exactly.
>>> The net effect though is that style which would be merely sloppy
>>> or inefficient on the road will dump you off the rollers.
>> Here's a theory.
>> On pavement, you can do two things: lean into turns and steer the
>> contact patch under your center of gravity. On rollers, you can't
>> lean. If you do, you either fall down or else stop leaning and
>> steer the contact patch back under your center of gravity as quick
>> as you can. There's just no centripetal force, no actual turn on
>> rollers, to allow the normal leaning that pavement provides.
> Yes that's right.
> But it's magnitudes harder to trackstand on rollers with the wheels
> not turning.
That has more to do with trail of the front wheel by which slight
changes in CG to ground can be made on the road but not on rollers
where the trail is usually closer to zero to prevent overrunning the
front roller. Besides, you can't arbitrarily move forward or back to
regain stability before standing still.
Jobst Brandt
|
| | | | | | | |
Date: 05 Sep 2007 12:49:48
From:
Subject: Re: physics of bicycle rollers information?
|
On Wed, 05 Sep 2007 13:37:04 -0500, A Muzi <am@yellowjersey.org >
wrote:
>>>> "A Muzi" <am@yellowjersey.org> wrote
>>>> I suspect the gyroscopic effect, minimal on the road,
>>>>> becomes the primary effect on rollers.
>
>>> Tom Nakashima wrote:
>>>> I've watched a gyroscope, why is it that it has great leaning capabilities,
>>>> while
>>>> riding a bicycle does not and riding on rollers even less of a lean angle?
>>>> Is it because the gyroscope is pivoting on one point rather than two?
>
>> A Muzi <am@yellowjersey.org> wrote:
>>> I suspect the normal steering behavior of a bicycle is limited on
>>> rollers. Look over the excellent 'Building An Unrideable Bicycle' for
>>> background on 'normal'.
>>> The motion of the rims/tires, which is trivial to a moving bicycle,
>>> probably has some effect on the rollers where our arcs across the
>>> pavement are absent. You can tell I'm speculating. Any other roller
>>> riders care to comment? The bike definitely handles differently on
>>> rollers and I'm grasping at why exactly. The net effect though is that
>>> style which would be merely sloppy or inefficient on the road will dump
>>> you off the rollers.
>
>carlfogel@comcast.net wrote:
>> Here's a theory.
>> On pavement, you can do two things: lean into turns and steer the
>> contact patch under your center of gravity.
>> On rollers, you can't lean. If you do, you either fall down or else
>> stop leaning and steer the contact patch back under your center of
>> gravity as quick as you can.
>> There's just no centripetal force, no actual turn on rollers, to allow
>> the normal leaning that pavement provides.
>
>Yes that's right.
>But it's magnitudes harder to trackstand on rollers with the wheels not
>turning.
Dear Andrew,
When stopped on rollers, you can't move the bike back and forth the
slight amount that moves the tires back under your center of gravity
and makes trackstands much easier.
Instead, you just spin the rollers without any forward-backward
motion. The tires stay pretty much stuck in the same place in terms of
backing and filling, while moving very little sideways in an attempted
trackstand on rollers.
(Let's ignore the despicable creatures who can do trackstands while
doing handstands on the seat or handlebars and who probably find
rollers no challenge.)
Cheers,
Carl Fogel
|
| | | | | | |
Date: 05 Sep 2007 07:52:27
From: Tom Nakashima
Subject: Re: physics of bicycle rollers information?
|
<carlfogel@comcast.net > wrote in message
news:i6lsd3ls8585eh9qfqr11180giu85e81rp@4ax.com...
> On Wed, 05 Sep 2007 01:25:53 -0500, A Muzi <am@yellowjersey.org>
> wrote:
>
>>> "A Muzi" <am@yellowjersey.org> wrote
>>> I suspect the gyroscopic effect, minimal on the road,
>>>> becomes the primary effect on rollers.
>>
>>Tom Nakashima wrote:
>>> I've watched a gyroscope, why is it that it has great leaning
>>> capabilities,
>>> while
>>> riding a bicycle does not and riding on rollers even less of a lean
>>> angle?
>>> Is it because the gyroscope is pivoting on one point rather than two?
>>
>>I suspect the normal steering behavior of a bicycle is limited on
>>rollers. Look over the excellent 'Building An Unrideable Bicycle' for
>>background on 'normal'.
>>
>>The motion of the rims/tires, which is trivial to a moving bicycle,
>>probably has some effect on the rollers where our arcs across the
>>pavement are absent. You can tell I'm speculating. Any other roller
>>riders care to comment? The bike definitely handles differently on
>>rollers and I'm grasping at why exactly. The net effect though is that
>>style which would be merely sloppy or inefficient on the road will dump
>>you off the rollers.
>
> Dear Andrew,
>
> Here's a theory.
>
> On pavement, you can do two things: lean into turns and steer the
> contact patch under your center of gravity.
>
> On rollers, you can't lean. If you do, you either fall down or else
> stop leaning and steer the contact patch back under your center of
> gravity as quick as you can.
>
> There's just no centripetal force, no actual turn on rollers, to allow
> the normal leaning that pavement provides.
>
> Cheers,
>
> Carl Fogel
But what if you're "not" leaning into a "turn" on pavement, but instead
just leaning the bike on a straight where there is no centrifugal force?
One still manages to stay upright on pavement while leaning the bike,
rather on rollers where you'll topple over.
The more I think about the science of riding on rollers, the more
confusing it becomes. It sort of defies the gyroscope theory.
-tom
|
| | | | | | | |
Date: 05 Sep 2007 21:37:56
From:
Subject: Re: physics of bicycle rollers information?
|
Tom Nakashima writes:
>>>>> I suspect the gyroscopic effect, minimal on the road, becomes
>>>>> the primary effect on rollers.
>>>> I've watched a gyroscope, why is it that it has great leaning
>>>> capabilities, while riding a bicycle does not and riding on
>>>> rollers even less of a lean angle? Is it because the gyroscope
>>>> is pivoting on one point rather than two?
>>> I suspect the normal steering behavior of a bicycle is limited on
>>> rollers. Look over the excellent 'Building An Unridable Bicycle'
>>> for background on 'normal'.
>>> The motion of the rims/tires, which is trivial to a moving
>>> bicycle, probably has some effect on the rollers where our arcs
>>> across the pavement are absent. You can tell I'm speculating.
>>> Any other roller riders care to comment? The bike definitely
>>> handles differently on rollers and I'm grasping at why exactly.
>>> The net effect though is that style which would be merely sloppy
>>> or inefficient on the road will dump you off the rollers.
>> Here's a theory.
>> On pavement, you can do two things: lean into turns and steer the
>> contact patch under your center of gravity.
>> On rollers, you can't lean. If you do, you either fall down or
>> else stop leaning and steer the contact patch back under your
>> center of gravity as quick as you can.
>> There's just no centripetal force, no actual turn on rollers, to
>> allow the normal leaning that pavement provides.
> But what if you're "not" leaning into a "turn" on pavement, but
> instead just leaning the bike on a straight where there is no
> centrifugal force? One still manages to stay upright on pavement
> while leaning the bike, rather on rollers where you'll topple over.
> The more I think about the science of riding on rollers, the more
> confusing it becomes. It sort of defies the gyroscope theory.
You cannot lean (have the cg of rider and bicycle off vertical on
rollers or you fall. Leaning the body one way and the bicycle the
other, as you mention on the road is not "leaning" but contorting the
line between CG and road. It is still vertical if you travel straight
ahead on the road even though the wheel is canted.
Gyroscopic forces only have a significant effect on bicycling when
riding no-hands:
http://www.sheldonbrown.com/brandt/gyro.html
You can steer a bicycle on rollers riding no-hands and this is done
the same as on the road, but it doesn't constitute leaning the CG, but
only the bicycle. You must lean the body the other way to not fall.
Therein, and the lack of momentum, lies the difference between road
and rollers that makes it odd for first time users. You must not lean
into course corrections!
Jobst Brandt
|
| | | | | | | | |
Date: 06 Sep 2007 06:28:01
From: Tom Nakashima
Subject: Re: physics of bicycle rollers information?
|
<jobst.brandt@stanfordalumni.org > wrote in message
news:46df21b4$0$14088$742ec2ed@news.sonic.net...
> Gyroscopic forces only have a significant effect on bicycling when
> riding no-hands:
> Jobst Brandt
I was thinking it doesn't matter whether you're riding with hands or
no-hands
on the bar, the gyroscopic forces would be the same. And that would be
proven when riding no-hands on rollers?
Or another example would be riding no hands on a steep banked track, such as
a velodrome. I believe the bike is no longer perpendicular to the pavement
angle,
and the gyroscopic forces is making that so.
-tom
|
| | | | | | | | | |
Date: 06 Sep 2007 15:22:10
From:
Subject: Re: physics of bicycle rollers information?
|
Tom Nakashima writes:
>> Gyroscopic forces only have a significant effect on bicycling when
>> riding no-hands:
> I was thinking it doesn't matter whether you're riding with hands or
> no-hands on the bar, the gyroscopic forces would be the same. And
> that would be proven when riding no-hands on rollers?
They are the same and sop small that hands on the bars override any
effect they have. That is why many folks cannot ride no-hands. Just
the transition of releasing the grip on the bars unstabilizes the
bicycle.
> Or another example would be riding no hands on a steep banked track,
> such as a velodrome. I believe the bike is no longer perpendicular
> to the pavement angle, and the gyroscopic forces is making that so.
If you consider the center of pressure in the contact of the tire to
the track, you'll note that it is a few mm from center on a 25mm tire,
not enough to cause any steering that is not readily countered by
leaning the bicycle ever so slightly. This is not gyroscopic action
that comes into play when changing the angle of lean when riding
no-hands.
http://www.sheldonbrown.com/brandt/gyro.html
Jobst Brandt
|
| | | | | | | | | | |
Date: 06 Sep 2007 11:55:36
From: Tom Nakashima
Subject: Re: physics of bicycle rollers information?
|
<jobst.brandt@stanfordalumni.org > wrote in message
news:46e01b22$0$14126$742ec2ed@news.sonic.net...
> Tom Nakashima writes:
>
>>> Gyroscopic forces only have a significant effect on bicycling when
>>> riding no-hands:
>
>> I was thinking it doesn't matter whether you're riding with hands or
>> no-hands on the bar, the gyroscopic forces would be the same. And
>> that would be proven when riding no-hands on rollers?
>
> They are the same and sop small that hands on the bars override any
> effect they have. That is why many folks cannot ride no-hands. Just
> the transition of releasing the grip on the bars unstabilizes the
> bicycle.
>
>> Or another example would be riding no hands on a steep banked track,
>> such as a velodrome. I believe the bike is no longer perpendicular
>> to the pavement angle, and the gyroscopic forces is making that so.
>
> If you consider the center of pressure in the contact of the tire to
> the track, you'll note that it is a few mm from center on a 25mm tire,
> not enough to cause any steering that is not readily countered by
> leaning the bicycle ever so slightly. This is not gyroscopic action
> that comes into play when changing the angle of lean when riding
> no-hands.
>
> http://www.sheldonbrown.com/brandt/gyro.html
>
> Jobst Brandt
One of the things that caught my attention from the article was the
"ski-bob-
bicycle that has no gyroscopic forces. A bicycle with no rotating parts.
Wouldn't that be the same as riding rollers, since the rotation of the drums
cancelling out the rotation of the wheels? Therefore, that is why when one
leans the bike on rollers, you'll topple over.
-tom
|
| | | | | | | | | | | |
Date: 07 Sep 2007 03:37:59
From:
Subject: Re: physics of bicycle rollers information?
|
Tom Nakashima writes:
>>>> Gyroscopic forces only have a significant effect on bicycling when
>>>> riding no-hands:
>>> I was thinking it doesn't matter whether you're riding with hands or
>>> no-hands on the bar, the gyroscopic forces would be the same. And
>>> that would be proven when riding no-hands on rollers?
>> They are the same and sop small that hands on the bars override any
>> effect they have. That is why many folks cannot ride no-hands. Just
>> the transition of releasing the grip on the bars unstabilizes the
>> bicycle.
>>> Or another example would be riding no hands on a steep banked track,
>>> such as a velodrome. I believe the bike is no longer perpendicular
>>> to the pavement angle, and the gyroscopic forces is making that so.
>> If you consider the center of pressure in the contact of the tire to
>> the track, you'll note that it is a few mm from center on a 25mm tire,
>> not enough to cause any steering that is not readily countered by
>> leaning the bicycle ever so slightly. This is not gyroscopic action
>> that comes into play when changing the angle of lean when riding
>> no-hands.
http://www.sheldonbrown.com/brandt/gyro.html
> One of the things that caught my attention from the article was the
> "ski-bob- bicycle that has no gyroscopic forces. A bicycle with no
> rotating parts. Wouldn't that be the same as riding rollers, since
> the rotation of the drums canceling the rotation of the wheels?
> Therefore, that is why when one leans the bike on rollers, you'll
> topple over.
The rollers on which the bicycle is supported do not contribute
gyroscopic steering forces, being on fixed axes. The bicycle front
wheel will steer just as it does on the road, when the bicycle is
leaned to one side or the other. I hope you can ride no-hands on the
road so you can try all this. If not, try wheeling the riderless
bicycle holding it by the saddle as described in the FAQ.
The Ski-bob cannot be ridden no-hands, but a bicycle on rollers can.
The steering is accomplished the same as on the road, with gyroscopic
forces. As I said, these are so slight that people unskilled in the
art cannot ride no-hands. Most of these people pass it off as a
stupid and dangerous act when asked whether their obviously bent frame
rides straight ahead, no-hands.
Jobst Brandt
|
| | | | | | | |
Date: 05 Sep 2007 14:06:03
From: A Muzi
Subject: Re: physics of bicycle rollers information?
|
>>>> "A Muzi" <am@yellowjersey.org> wrote
>>>> I suspect the gyroscopic effect, minimal on the road,
>>>>> becomes the primary effect on rollers.
>>> Tom Nakashima wrote:
>>>> I've watched a gyroscope, why is it that it has great leaning
>>>> capabilities,
>>>> while
>>>> riding a bicycle does not and riding on rollers even less of a lean
>>>> angle?
>>>> Is it because the gyroscope is pivoting on one point rather than two?
>> A Muzi <am@yellowjersey.org> wrote:
>>> I suspect the normal steering behavior of a bicycle is limited on
>>> rollers. Look over the excellent 'Building An Unrideable Bicycle' for
>>> background on 'normal'.
>>> The motion of the rims/tires, which is trivial to a moving bicycle,
>>> probably has some effect on the rollers where our arcs across the
>>> pavement are absent. You can tell I'm speculating. Any other roller
>>> riders care to comment? The bike definitely handles differently on
>>> rollers and I'm grasping at why exactly. The net effect though is that
>>> style which would be merely sloppy or inefficient on the road will dump
>>> you off the rollers.
> <carlfogel@comcast.net> wrote
>> Here's a theory.
>> On pavement, you can do two things: lean into turns and steer the
>> contact patch under your center of gravity.
>>
>> On rollers, you can't lean. If you do, you either fall down or else
>> stop leaning and steer the contact patch back under your center of
>> gravity as quick as you can.
>>
>> There's just no centripetal force, no actual turn on rollers, to allow
>> the normal leaning that pavement provides.
Tom Nakashima wrote:
> But what if you're "not" leaning into a "turn" on pavement, but instead
> just leaning the bike on a straight where there is no centrifugal force?
> One still manages to stay upright on pavement while leaning the bike,
> rather on rollers where you'll topple over.
>
> The more I think about the science of riding on rollers, the more
> confusing it becomes. It sort of defies the gyroscope theory.
Acrobatics aside, a bicycle ridden on pavement describes a series of
arcs, not actually a straight line.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
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Date: 05 Sep 2007 22:03:34
From:
Subject: Re: physics of bicycle rollers information?
|
Andrew Muzi writes:
>>>>>> I suspect the gyroscopic effect, minimal on the road, becomes
>>>>>> the primary effect on rollers.
>>>>> I've watched a gyroscope, why is it that it has great leaning
>>>>> capabilities, while riding a bicycle does not and riding on
>>>>> rollers even less of a lean angle? Is it because the gyroscope
>>>>> is pivoting on one point rather than two?
>>>> I suspect the normal steering behavior of a bicycle is limited on
>>>> rollers. Look over the excellent 'Building An Unrideable
>>>> Bicycle' for background on 'normal'. The motion of the
>>>> rims/tires, which is trivial to a moving bicycle, probably has
>>>> some effect on the rollers where our arcs across the pavement are
>>>> absent. You can tell I'm speculating. Any other roller riders
>>>> care to comment? The bike definitely handles differently on
>>>> rollers and I'm grasping at why exactly. The net effect though is
>>>> that style which would be merely sloppy or inefficient on the
>>>> road will dump you off the rollers.
>>> Here's a theory. On pavement, you can do two things: lean into
>>> turns and steer the contact patch under your center of gravity.
>>> On rollers, you can't lean. If you do, you either fall down or
>>> else stop leaning and steer the contact patch back under your
>>> center of gravity as quick as you can.
>>> There's just no centripetal force, no actual turn on rollers, to
>>> allow the normal leaning that pavement provides.
>> But what if you're "not" leaning into a "turn" on pavement, but
>> instead just leaning the bike on a straight where there is no
>> centrifugal force? One still manages to stay upright on pavement
>> while leaning the bike, rather on rollers where you'll topple over.
>> The more I think about the science of riding on rollers, the more
>> confusing it becomes. It sort of defies the gyroscope theory.
> Acrobatics aside, a bicycle ridden on pavement describes a series of
> arcs, not actually a straight line.
I prefer not to call it that, having ridden no-hands at high speed
down smooth roads and watched the white stripe on which I was riding.
The "arc" (zigzag) definition that Jim Papadopoulos often cited doe not
fit practice. The same goes for the riderless bicycle of which we saw
videos here not long ago. Note the bicycle weaves only after being
diverted from its path:
http://ruina.tam.cornell.edu/research/topics/bicycle_mechanics/bicycle_stability.mov
It may be an arc but of extremely large radius. The earth surface is
also curved.
Jobst Brandt
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Date: 04 Sep 2007 10:42:15
From: Paul Myron Hobson
Subject: Re: physics of bicycle rollers information?
|
Tom Nakashima wrote:
> "A Muzi" <am@yellowjersey.org> wrote in message
> news:13dq02fdkja1l72@corp.supernews.com...
> I suspect the gyroscopic effect, minimal on the road,
>> becomes the primary effect on rollers. Andrew Muzi
>> www.yellowjersey.org
>> Open every day since 1 April, 1971
>
> I've watched a gyroscope, why is it that it has great leaning capabilities,
> while
> riding a bicycle does not and riding on rollers even less of a lean angle?
> Is it because the gyroscope is pivoting on one point rather than two?
> -tom
>
>
The gyroscopic moments of a rotating bicycle wheel are very small
compared to the moment of the weight of the cyclist while leaning.
\\paul
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Date: 03 Sep 2007 22:24:28
From: Jim Behning
Subject: Re: physics of bicycle rollers information?
|
On Mon, 03 Sep 2007 08:21:27 -0700, Chocobot <chrisallick@gmail.com >
wrote:
>
>>
>> Its the same effect except you must visually keep track of position on
>> the rollers. See:
>>
>> http://www.sheldonbrown.com/brandt/gyro.html
>>
>> Jobst Brandt
>
>Thanks, I had read this previously, but it didn't seem to answer my
>question. If I am reading this write, the act of moving forward has
>nothing to do with the riders ability to balance the bike, that is why
>one can ride on a set of rollers and still stay upright? However,
>moving forward does help to keep the front wheel straight?
>
>On another note, here is a video of someone people attempting
>ridiculous tricks on rollers. At one point someone tries to do a skid
>(as in on a track bike) on the rollers, i think this proves the point
>that there is a little to zero forward momentum, and "rolling off"
>these things pretty much not possible.
>
>Also, one last question. I had my headphones plugged into my computer
>while riding on the rollers and I was given a very startling
>electrical shock, where is that energy coming from? my bike is
>totally aluminum.
Your bike is not totally aluminum. There is steel and other materials
in it. The power lines in the US that service most houses is aluminum.
Aluminum has nothing to do with you question about static. You can
create a static charge getting in and out of your car seat. That is
why they recommend you discharge yourself of static before you start
fueling your car and do not resfresh that static by sitting in the car
while the pump is running.
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Date: 03 Sep 2007 17:49:15
From:
Subject: Re: physics of bicycle rollers information?
|
Chris Allick writes:
>> Its the same effect except you must visually keep track of position on
>> the rollers. See:
http://www.sheldonbrown.com/brandt/gyro.html
> Thanks, I had read this previously, but it didn't seem to answer my
> question. If I am reading this write, the act of moving forward has
> nothing to do with the riders ability to balance the bike, that is
> why one can ride on a set of rollers and still stay upright?
> However, moving forward does help to keep the front wheel straight?
It doesn't matter whether the bicycle moves forward or the road moves
backward for staying upright from steering. The inertia of rider
velocity makes road riding more stable but riding slowly is much like
balancing on rollers at any speed, there being no forward momentum and
inertia of the bicycle.
> On another note, there is a video of someone people attempting
> ridiculous tricks on rollers. At one point someone tries to do a skid
> (as in on a track bike) on the rollers, I think this proves the point
> that there is a little to zero forward momentum, and "rolling off"
> these things pretty much not possible.
But you can roll of them to either side and therein lies the skill. I
have seen 150mm diameter rollers about as wide on which a skilled
rider rides with little effort.
> Also, one last question. I had my headphones plugged into my computer
> while riding on the rollers and I was given a very startling
> electrical shock, where is that energy coming from? My bike is
> totally aluminum.
Static electricity is on the surface of insulators and most likely
generated like a Van de Graaff generator in dry air by the tires.
http://amasci.com/emotor/vdg.html
http://en.wikipedia.org/wiki/Van_de_Graaff_generator
Jobst Brandt
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Date: 03 Sep 2007 02:30:29
From:
Subject: Re: physics of bicycle rollers information?
|
chrisallick@gmail.com writes:
> Can anyone point me toward some information about the physics of
> bicycle rollers. By rollers I mean:
http://www.kreitler.com/product.php?section=product&item=rollers_4_5
> I have been reading about the physics of a bike in motion, and why
> it "stays up," but I was wondering if these same principles explain
> why you can ride on cycling rollers and not fall over. A simple
> explanation would be fine as well, with some keywords that I can
> further research.
Its the same effect except you must visually keep track of position on
the rollers. See:
http://www.sheldonbrown.com/brandt/gyro.html
Jobst Brandt
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Date: 02 Sep 2007 14:01:38
From: Tim McNamara
Subject: Re: physics of bicycle rollers information?
|
In article <1188753298.627344.290870@o80g2000hse.googlegroups.com >,
chrisallick@gmail.com wrote:
> Can anyone point me towards some information about the physics of
> bicycle rollers. By rollers I mean:
>
> http://www.kreitler.com/product.php?section=product&item=rollers_4_5
>
> I have been reading about the physics of a bike in motion, and why it
> "stays up," but i was wondering if these same principles explain why
> you can ride on cycling rollers and not fall over.
Yes, since there's nothing else to keep a bike upright unless you
mechanically prop it up. It doesn't make any difference whether the
bike is on pavement or on rollers.
Learning to ride rollers takes practice, though, because of the effects
of the front roller as the front wheel turns from side to side. As the
tire turns to the side, it wants to slide down the slope but the motion
of the roller tends to pull the tire forward. It makes for a nervous
rider who tends to overcorrect initially. I have seen photos of people
riding rollers no-handed, even taking off jerseys, arm or leg warmers,
etc.- even playing guitar! I've never gotten anywhere near that good at
riding rollers...
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