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Main Date: 04 Dec 2006 09:19:20 From: dgk Subject: I fixed a broken spoke! Which correctly implies that I broke another one. I got lucky; this one was not on the drive side. So I took a spoke from a retired wheel (rear wheel same bike) and replaced the broken one using the same pattern as the nearby spokes. Once I put the wheel on the bike I was able to true it pretty well by seeing how that section passed the brakes. A few twists and it kept the same distance as the rest of the wheel. It rode fine this morning. I was just on the SheldonBrown site looking at freehubs, and it looks easy enough to remove the cassette. I think I'll almost look forward to the next broken spoke so I have an excuse to remove the cassette. It's almost sure to be on the drive side. Do I have to be concerned about Dish? It seems that if the rest of the wheel is correct and this one spoke has been adjusted so that the rim is straight, then the dish is correct?   Date: 22 Dec 2006 20:22:48 From: Gary Young Subject: Re: I fixed a broken spoke! On Fri, 22 Dec 2006 18:02:01 -0800, jim beam wrote: > Peter Cole wrote: >> jim beam wrote: >>> Peter Cole wrote: >>>> jim beam wrote: >>>>> Peter Cole wrote: >>>>>> jim beam wrote: >> >>>>>>> but again, "correcting" prior to hub hole deformation has the >>>>>>> spoke out of the load line too! do you dispute the geometry i >>>>>>> illustrated? >>>>>> >>>>>> I saw nothing to dispute, just simple trig. >>>>> >>>>> right, and that trig supports the spoke angle at which spokes are >>>>> manufactured, not arbitrarily bent. >>>> >>>> I don't draw that conclusion. >>> >>> what's not clear about it? what conclusion /do/ you draw? >> >> None. > > yes you do. you disagree. that means taking a contrary position. i > want you to state that and analyze it. > >> >>> majority of deformation, yes, but not all. as you say, load/area >>> equilibrium depends on load applied. load when "stress relieving" >>> therefore needs to exceed that experienced in service or else it will >>> occur when the wheel's in use and so send the wheel out of true. >> >> Yes, perhaps, but we're discussing fatigue. > > cop out. /you/ were discussing spoke seating. i responded. not you're > avoiding the question. > >> >> >>>> If the inside radius of the elbow is completely supported by the >>>> flange, how can it flex? It is not able to move. >> >>> now, here we have a spoke whose load is offset from the spoke axis by >>> the length of the elbow shank. the elbow will therefore bend on >>> loading. period. that bending will "amplify" the stress experienced >>> in the skin of the spoke by the leverage exerted. real simple. now >>> add cyclic loading, surface quality irregularities, microstructure >>> irregularities, and we have fatigue. end of story. >> >> If the spoke is constrained from moving, it can't move, hence it can't >> bend. End of story. > > that is a serious misunderstanding. where do you think fatigue comes > from? by definition, if it fatigues, it's experiencing strain, in this > case, bending. > >> >> >>>>>> Furthermore, if the load brings the spoke near yield, it will >>>>>> operate at that point, drastically reducing fatigue life. That's >>>>>> why most of your spokes failed at the outside of the bend. >>>>> >>>>> but "residual stress theory" has /compressive/ residual stress on >>>>> the outside of the bend... >>>> >>>> I'm talking about obtuse angles. If the spoke angle is too obtuse, >>>> load will make the angle more acute, causing tensile stress in the >>>> outside (elbow) skin. If the (initial) spoke angle was obtuse enough >>>> to cause slight yield (bend) during tensioning, then the stress on >>>> the skin will remain just below yield during the (short) operational >>>> life of the spoke. If the spoke bows out from the flange after >>>> tensioning, the angle is too obtuse, and the outside (elbow) with >>>> remain under (additional) tension, perhaps near yield. >>> >>> but how does hub hole distortion on yielding affect that angle? >>> [rhetorical] >> >> It doesn't matter if, at the end of tensioning, the angle is still too >> obtuse. > > no peter, you're dodging again. i demonstrated the effect of spoke > seating on the need to bend the spoke. address the question. > >> >> >>>> I don't know what you mean by "significant". The Mavic method has you >>>> apply about half the final tension, then stress relieve, then fully >>>> tension and stress relieve again. >>> >>> ok, /you/ can apply the leaning method long before mavic say to do so. >> >> Read it yourself: >> <http://home.comcast.net/~carlfogel/download/SpokeTension.pdf> > > /i/ mailed that to carl. and i have read it. you're avoiding my point. > again. > >> >> >>>>> i agree with what you say, but jobst says to bend before the spokes >>>>> are tensioned, and that's premature. >>>> >>>> No, he doesn't -- at least not in his book. I don't know why you keep >>>> repeating this. >>> >>> maybe you read a different version of the book to me? it clearly has >>> a section on "correcting the spoke line" that's spoke bending. and >>> he says to do it after lacing, but before tensioning. and because >>> that precedes hub hole deformation, it can't account for final spoke >>> angle and is therefore premature. i don't understand what's hard to >>> understand about that. >> >> I have the third edition. In Part II "Building and Repairing Wheels", >> under the section "Tensioning the Wheel" (pg. 95), there are six >> sub-sections: "Warning", "Taking Out the Slack", "Making Them Tight", >> "Spoke Twist", "Tension by Tone", and finally "Correcting the Spoke Line". >> >> Does your copy have these sections in a different order? > > so you /do/ have "correcting the spoke line"! and what does it say there? > "To avoid fatigue failures the unsupported spoke shaft should follow a straight line between the last points of contact with the hub and rim. AFTER TENSIONING the lines of the spokes in a new wheel must be corrected to achieve this condition." p. 72 of the 3d edition (emphasis added). >> >>>> If the amount of stress relief applied at that step more or less >>>> equals final tension, then any additional seating would be >>>> identically achieved just by bringing the overall tension up. >>> >>> except that spoke tension in static loading is not the highest the >>> wheel will ever experience in service - as proved by my "round the >>> block" experiment. >> >> When you ride an un-stress relieved wheel "around the block", "honking >> up hills", as I said before, you can put lateral loads on the wheel, >> which will nominally increase (some) spoke tension. > > ok, we agree. > >> Bear in mind that >> the contact patch is also loaded vertically, so you are first reducing >> static tension, then superimposing a (potentially large) lateral load. > > ok. > >> What this does, more than force additional flange seating, is to yield >> the spoke line to the load line, essentially "correcting the spoke line" >> somewhat. > > elastically, not plastically. > >> That will shorten the spoke path and reduce static tension. > > i don't buy that. the rim bends too - that pulls the spokes further > from the flange. tension increase is related to 1/sin theta. > >> >> Your own experiences seem to confirm the need to correct the spoke line. >> The outcomes you describe are entirely consistent with this. > > no, you're trying to twist my words to suit your prejudice. > >> >> >>>> The real reason must be correction of the spoke line. >>> >>> you're trying to twist the facts to fit your preconception. >> >> I don't think so. > > but you've just done it again on almost every point in this response!   Date: 21 Dec 2006 10:40:27 From: Gary Young Subject: Re: I fixed a broken spoke! On Wed, 20 Dec 2006 15:06:58 -0500, Peter Cole wrote: > jim beam wrote: > >> spokes angle towards a rim at say 6 degrees both sides front, and say 6 >> + 3 for rears. and that is what hub flanges are canted to. in >> addition, hub holes are angled perpendicular to the flange, so they too >> are aligned for optimal spoke position. >> >> see: >> http://www.flickr.com/photos/38636024@N00/316202144/ >> http://www.flickr.com/photos/38636024@N00/316202143/ > > I find your "pencil test" a bit unconvincing. > > I have a new, never spoked, LX rear hub (Shimano SH-FHM570-32). I found > that a 8d finish nail is almost an interference fit in the spoke holes. > I can state with absolute certainty that the holes are drilled parallel > to the axle, not perpendicular to the flange. Peter, On your hub, are the inner faces of the flanges perpendicular to the axle, or are they canted at the same angle as the outer faces (that is, are they parallel to the outer faces)? On my XT rear hub, they are perpendicular to the axle. I suspect that's a compromise made because of the difficulty of making a concave surface in a forged hub, at least without subsequent machining. The reason I ask is that if some of the commonest hubs out there don't have optimized inner faces, then jim beam's theory that spoke lines don't need adjusted doesn't hold water.     Date: 21 Dec 2006 13:38:19 From: Peter Cole Subject: Re: I fixed a broken spoke! Gary Young wrote: > On Wed, 20 Dec 2006 15:06:58 -0500, Peter Cole wrote: > >> jim beam wrote: >> >>> spokes angle towards a rim at say 6 degrees both sides front, and say 6 >>> + 3 for rears. and that is what hub flanges are canted to. in >>> addition, hub holes are angled perpendicular to the flange, so they too >>> are aligned for optimal spoke position. >>> >>> see: >>> http://www.flickr.com/photos/38636024@N00/316202144/ >>> http://www.flickr.com/photos/38636024@N00/316202143/ >> I find your "pencil test" a bit unconvincing. >> >> I have a new, never spoked, LX rear hub (Shimano SH-FHM570-32). I found >> that a 8d finish nail is almost an interference fit in the spoke holes. >> I can state with absolute certainty that the holes are drilled parallel >> to the axle, not perpendicular to the flange. > > Peter, > On your hub, are the inner faces of the flanges perpendicular to the axle, > or are they canted at the same angle as the outer faces (that is, are they > parallel to the outer faces)? > > On my XT rear hub, they are perpendicular to the axle. I suspect that's a > compromise made because of the difficulty of making a concave surface in a > forged hub, at least without subsequent machining. > > The reason I ask is that if some of the commonest hubs out there don't > have optimized inner faces, then jim beam's theory that spoke lines don't > need adjusted doesn't hold water. The inner faces of the flanges on my LX hub are perpendicular to the axle, yes.     Date: 21 Dec 2006 13:17:32 From: dvt Subject: Re: I fixed a broken spoke! Gary Young wrote: > The reason I ask is that if some of the commonest hubs out there don't > have optimized inner faces, then jim beam's theory that spoke lines don't > need adjusted doesn't hold water. jim beam has admitted that his theory is limited to special cases. It's so limited as to have little application in real life. -- Dave dvt at psu dot edu   Date: 19 Dec 2006 08:18:44 From: Gary Young Subject: Re: I fixed a broken spoke! On Wed, 06 Dec 2006 21:09:48 -0800, jim beam wrote: > dvt wrote: >> jim beam wrote: >>> dvt wrote: >>>> jim beam wrote: >>>>> but given that the hub flanges are canted and that the angle which >>>>> the spoke manufacturer already provides is already appropriate, >>>>> there's no point in this exercise in the first place. >> >>>> You never answered this question the first time, so let's try again... >> >>> dave, some threads get too long and windy. if you want to /ensure/ i >>> read a question that's somehow important, post a new thread. and make >>> sure i'm not on vacation, traveling, otherwise busy or disinterested. >> >> Nice try, jim. Here's the record: >> >> <http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/1c072f5d8b7c8892/83a78e954c0f932d> > > is this the 'unanswered' question? > "I've been watching this thread, hoping that I wasn't the only one with > this question. How do you "cant and drill" a hole in the hub flange so > that both inbound *and* outbound spokes are "optimized?" If the hole was > so canted, would that mean that the hubs should not be deformed during > the build?" > > if so, i'd have thought the answers obvious. maybe that's why i didn't > bother answering. > >> >> >> Scroll down to messages 103-110. You responded to that exact subthread, >> so I know you were reading it. But you failed to answer the question. >> >>>> In bound vs. out bound, crossing pattern, and rim size all affect the >>>> angle in question. I don't see hubs keted for each variation, and >>>> I don't see holes labeled for inbound and outbound spokes. Do small >>>> wheels (think recumbent) usually use the same hubs as diamond frame >>>> bikes? If so, do they have a much higher incidence of spoke breakage? >> >>> if you want to demonstrate something dave, do the math for the spoke >>> angle given that a hub hole may be larger diameter than the spoke and >>> seated in a flange of given thickness. then compare that to the stock >>> spoke angle of ~95°. >> >> You made the claim. It's your job to prove it. Here's the claim you >> made, in case you've forgotten: >> >> "the spoke elbow comes pre-formed with the best resultant angle and the >> hub flange is canted and drilled also to give the best resultant angle." >> >> You made no reservations about wheel size, lacing pattern, or any of the >> other things you tried to add in later when questioned. And what about >> dished wheels? Or rims with offset spoke beds? >> >> I'm looking forward to your response. >> > unless you want a full custom hub, the economics don't support > accommodating non-standard configurations. > > two hub pics for consideration: > http://www.flickr.com/photos/38636024@N00/316202144/ > http://www.flickr.com/photos/38636024@N00/316202143/ > > for the cynics, i didn't happen to have any 2.4mm rod about for the hub > hole pic, but if you don't believe the hub holes are perpendicular to > the flange, do this experiment yourself. On my XT rear hub, the outer faces of the flanges are canted, but the inner faces are perpendicular to the hub axle or very nearly so. (The same may be true of my LX front hub, but I'm much less sure; on the rear hub, the difference in canting between the inner and outer faces is unmistakable even when eyeballing it.) I can't find a picture of an XT hub that shows this, but if you go to the end of this pdf where there are a series of drawings of hubs, they all appear to have one canted face and one perpendicular face: http://www.dtswiss.com/data/files/MAN_EN_41201162428.pdf If the spoke holes were drilled perpendicular to the canted outer face, I would expect them to exit the 90-degree inner face at a point further from the edge of the flange. But both the outer and inner exit points appear to be the same distance from the edge. That leads me to believe that the holes are drilled parallel to the hub axle, contrary to the caption on the second photo you link to above. There may be a difference in the way the holes are beveled (if that's the right term) on the inside versus the outside, but not that I can see. The effect of the difference in canting is that the inbound spokes exit at what appears to be an optimized angle when their heads are seated squarely in the canted outer face (that is, when the heads lie flat against the face, with no lifting of any part of the circumference). However, when the outbound spokes are seated squarely against the 90-degree inner face, they exit perpendicular to the hub axle, or nearly so. I'm not sure why the hub is designed that way. Is there a reason inbound spokes need to have their seating optimized more than outbound spokes? Maybe because the elbow angle tends to open up as they are pulled, whereas the angle of outbound spokes becomes more acute? In any event, this does seem to fly in the face of your argument that the spoke/hub combination results in an optimized spoke line. > > for dave, no, there's nothing sinister about this hub being black or > large flange. it just happened to be a virgin hub at the top of my > parts box.     Date: 30 Dec 2006 13:11:27 From: Subject: Re: I fixed a broken spoke! On Tue, 19 Dec 2006 08:18:44 -0600, Gary Young <garyyoung3@gmail.com > wrote: >On Wed, 06 Dec 2006 21:09:48 -0800, jim beam wrote: > >> dvt wrote: >>> jim beam wrote: >>>> dvt wrote: >>>>> jim beam wrote: >>>>>> but given that the hub flanges are canted and that the angle which >>>>>> the spoke manufacturer already provides is already appropriate, >>>>>> there's no point in this exercise in the first place. >>> >>>>> You never answered this question the first time, so let's try again... >>> >>>> dave, some threads get too long and windy. if you want to /ensure/ i >>>> read a question that's somehow important, post a new thread. and make >>>> sure i'm not on vacation, traveling, otherwise busy or disinterested. >>> >>> Nice try, jim. Here's the record: >>> >>> <http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/1c072f5d8b7c8892/83a78e954c0f932d> >> >> is this the 'unanswered' question? >> "I've been watching this thread, hoping that I wasn't the only one with >> this question. How do you "cant and drill" a hole in the hub flange so >> that both inbound *and* outbound spokes are "optimized?" If the hole was >> so canted, would that mean that the hubs should not be deformed during >> the build?" >> >> if so, i'd have thought the answers obvious. maybe that's why i didn't >> bother answering. >> >>> >>> >>> Scroll down to messages 103-110. You responded to that exact subthread, >>> so I know you were reading it. But you failed to answer the question. >>> >>>>> In bound vs. out bound, crossing pattern, and rim size all affect the >>>>> angle in question. I don't see hubs keted for each variation, and >>>>> I don't see holes labeled for inbound and outbound spokes. Do small >>>>> wheels (think recumbent) usually use the same hubs as diamond frame >>>>> bikes? If so, do they have a much higher incidence of spoke breakage? >>> >>>> if you want to demonstrate something dave, do the math for the spoke >>>> angle given that a hub hole may be larger diameter than the spoke and >>>> seated in a flange of given thickness. then compare that to the stock >>>> spoke angle of ~95°. >>> >>> You made the claim. It's your job to prove it. Here's the claim you >>> made, in case you've forgotten: >>> >>> "the spoke elbow comes pre-formed with the best resultant angle and the >>> hub flange is canted and drilled also to give the best resultant angle." >>> >>> You made no reservations about wheel size, lacing pattern, or any of the >>> other things you tried to add in later when questioned. And what about >>> dished wheels? Or rims with offset spoke beds? >>> >>> I'm looking forward to your response. >>> >> unless you want a full custom hub, the economics don't support >> accommodating non-standard configurations. >> >> two hub pics for consideration: >> http://www.flickr.com/photos/38636024@N00/316202144/ >> http://www.flickr.com/photos/38636024@N00/316202143/ >> >> for the cynics, i didn't happen to have any 2.4mm rod about for the hub >> hole pic, but if you don't believe the hub holes are perpendicular to >> the flange, do this experiment yourself. > >On my XT rear hub, the outer faces of the flanges are canted, but the >inner faces are perpendicular to the hub axle or very nearly so. (The same >may be true of my LX front hub, but I'm much less sure; on the rear >hub, the difference in canting between the inner and outer faces is >unmistakable even when eyeballing it.) > >I can't find a picture of an XT hub that shows this, but if you go to the >end of this pdf where there are a series of drawings of hubs, they all >appear to have one canted face and one perpendicular face: > >http://www.dtswiss.com/data/files/MAN_EN_41201162428.pdf > >If the spoke holes were drilled perpendicular to the canted outer face, I >would expect them to exit the 90-degree inner face at a point further from >the edge of the flange. But both the outer and inner exit points appear to >be the same distance from the edge. That leads me to believe that the >holes are drilled parallel to the hub axle, contrary to the caption on the >second photo you link to above. > >There may be a difference in the way the holes are beveled (if that's the >right term) on the inside versus the outside, but not that I can see. > >The effect of the difference in canting is that the inbound spokes exit at >what appears to be an optimized angle when their heads are seated squarely >in the canted outer face (that is, when the heads lie flat against the >face, with no lifting of any part of the circumference). > >However, when the outbound spokes are seated squarely against the >90-degree inner face, they exit perpendicular to the hub axle, or nearly >so. > >I'm not sure why the hub is designed that way. Is there a reason inbound >spokes need to have their seating optimized more than outbound spokes? >Maybe because the elbow angle tends to open up as they are pulled, whereas >the angle of outbound spokes becomes more acute? > >In any event, this does seem to fly in the face of your argument that the >spoke/hub combination results in an optimized spoke line. > > > >> >> for dave, no, there's nothing sinister about this hub being black or >> large flange. it just happened to be a virgin hub at the top of my >> parts box. Dear Jim, Here's a link to an archery physics page that others may be able to untangle and apply to bicycle wheels: http://www.mrfizzix.com/archery/bow.html Of course, things are complicated by the springiness of a round-curve pre-tensioned bicycle wheel versus the much straighter curve of the pre-tensioned bow, the different angles of a pair of spokes versus a bow-string, and the spoke crossing that's missing from a bow. But it looks like something to do with storing energy in a complicated springy structure. When the rim deforms sideways, it's bending like a bow. When the squeezed spoke bends the unsqueezed spoke at the crossing, it's doing the same thing in another plane. The result, for those like me who get lost in the calculations on the archery page, is that it's useless to try to calculate spoke tension increases according to absolute spoke deflection between the two springy points of the hub and the rim. A bicycle wheel is worthless as a makeshift tension gauge. You have to use a tension gauge, which isolates a short, straight span of spoke with two massively braced posts that reduce this unexpected behavior, much like a pipe-clamp, to very low levels. The tension gauge gives either a reading, either Park-style spring-needle k or DT-style measured absolute deflection. Then you look up what the reading means in a calibration/conversion table for a spoke of that material, shape, and thickness. So far, no wheel measured with a tension gauge has shown more than about 55~65 pounds of tension increase for a 60-pound squeeze force. A spoke in a much more rigid pipe-clamp does a little better, with the tension increase measured at about ~90 pounds for a 60-lb squeeze force. At low squeeze forces created by adding 5-pound weights, the Park gauge repeatedly shows that the spoke tension in a bicycle wheel drops at first and returns to its original level only after the spoke has bent under 20 pounds of weights. The bicycle wheel acts so much like a springy archer's bow that the simple Park tool reveals the odd behavior. When the same weights are added to the same spoke in the rigid pipe-clamp rig, the Park gauge shows that the spoke tension rises (instead of dropping and returning to the original level). The pipe clamp is so rigid that the Park tool is probably not sensitive enough to reveal the initial drop in tension as the spoke bends. These details are worth repeating, since they've developed over many threads and posts. Cheers, Carl Fogel       Date: 30 Dec 2006 13:21:51 From: Subject: Re: I fixed a broken spoke! On Sat, 30 Dec 2006 13:11:27 -0700, carlfogel@comcast.net wrote: Dear Gary, Whoops! Sorry, I wrote that reply not to your post, but to a post from Jim Beam post way off somewhere else in this thread. My reply ended up mistakenly attached to your post, probably because of my careless clicking. I tacked a copy onto Jim's post. Cheers, Carl Fogel   Date: 19 Dec 2006 07:32:59 From: Gary Young Subject: Re: I fixed a broken spoke! On Wed, 06 Dec 2006 20:41:45 -0800, jim beam wrote: > carlfogel@comcast.net wrote: >> On Wed, 06 Dec 2006 11:36:01 GMT, jtaylor@NOSPAM.hfx.andara.com wrote: >> >>> On Tue, 05 Dec 2006 20:23:10 -0800, jim beam >>> <spamvortex@bad.example.net> wrote: >>> >>> >>>>> In bound vs. out bound, crossing pattern, and rim size all >>>>> affect the angle in question. I don't see hubs keted for each >>>>> variation, and I don't see holes labeled for inbound and outbound >>>>> spokes. Do small wheels (think recumbent) usually use the same hubs as >>>>> diamond frame bikes? If so, do they have a much higher incidence of >>>>> spoke breakage? >>>>> >>>> if you want to demonstrate something dave, do the math for the spoke >>>> angle given that a hub hole may be larger diameter than the spoke and >>>> seated in a flange of given thickness. then compare that to the stock >>>> spoke angle of ~95�. >>> >>> I think I saw those calculations a while ago - it was in a book called >>> "The Bicycle Wheel", I think. >> >> Dear J., >> >> Here's Jobst's diagram in "The Bicycle Wheel," for anyone curious >> about specifics, as opposed to the rhetorical questions and >> why-don't-you-look-it-up so common on RBT: >> >> http://i12.tinypic.com/2dako69.jpg > > thanks carl, but that's not what i was trying to describe - i was > talking about the angle that results from having a 2.0mm spoke in a > 2.4mm hub hole for a 3.4mm flange thickness. > >> >> Jobst's diagram shows spoke angles from hub to rim of 7.3 and 3.5 >> degrees. > > which is how the hub is canted. > >> >> So a slightly widened 95-degree elbow angle is reasonable for inner >> spokes that may be at 97.3~93.5 degrees. > > if the hub flange is canted, the spoke angle is from the point raised > for the spoke not sitting square in the larger hub hole, not from the > angle associated with flange spacing. I'm not sure what this means. Did you mean to say "sitting square" instead of "not sitting square"? If it didn't matter whether the spoke was sitting square, what would be the relevance of canting? > >> >> (Various front and rear hub widths probably don't change the angles >> much for 700c cross-3 wheels. Spoke elbows on tiny wheels for Moultons >> and recumbents may suffer from the orthopedic problems that afflict >> many dwarves, but small rims usually make very strong wheels.) >> >> Jobst recommends bending outer spokes enough to lie flat on the hub >> flange (and bending all spokes enough at the rim to "correct the spoke >> line.") >> >> Sapim disagrees. Here's their FAQ comment on 95 degree elbow angles >> and whether spokes should be bent ("forced") to change the angle: >> >> "If material is forced while lacing the hub, the spokes can be pulled >> over causing material weakness." >> >> "The original bend angle of 95� should remain intact." >> >> http://www.sapim.be/index.php?st=fa >> >> Elsewhere in "The Bicycle Wheel," Jobst mentions that steel spokes >> will bed into aluminum hubs, which have largely replaced the steel >> hubs that were popular when his first edition came out: >> >> "When spokes are properly tensioned the aluminum flange material on >> which they bear is usually under enough stress to conform to the >> spokes." --p. 59, "The Bicycle Wheel," 3rd edition, Jobst Brandt > > they do indeed. > http://www.flickr.com/photos/38636024@N00/104463818/ > >> >> There's a good drawing of a "Spoke Seating in the Flange" next to the >> text quoted above (and oodles more interesting stuff, such as >> correcting the spoke line), but anyone interested will need to get >> their own copy . . . >> >> http://sheldonbrown.com/harris/books.html#brandt >> >> Cheers, >> >> Carl Fogel     Date: 19 Dec 2006 08:21:14 From: jim beam Subject: Re: I fixed a broken spoke! Gary Young wrote: > On Wed, 06 Dec 2006 20:41:45 -0800, jim beam wrote: > >> carlfogel@comcast.net wrote: >>> On Wed, 06 Dec 2006 11:36:01 GMT, jtaylor@NOSPAM.hfx.andara.com wrote: >>> >>>> On Tue, 05 Dec 2006 20:23:10 -0800, jim beam >>>> <spamvortex@bad.example.net> wrote: >>>> >>>> >>>>>> In bound vs. out bound, crossing pattern, and rim size all >>>>>> affect the angle in question. I don't see hubs keted for each >>>>>> variation, and I don't see holes labeled for inbound and outbound >>>>>> spokes. Do small wheels (think recumbent) usually use the same hubs as >>>>>> diamond frame bikes? If so, do they have a much higher incidence of >>>>>> spoke breakage? >>>>>> >>>>> if you want to demonstrate something dave, do the math for the spoke >>>>> angle given that a hub hole may be larger diameter than the spoke and >>>>> seated in a flange of given thickness. then compare that to the stock >>>>> spoke angle of ~95�. >>>> I think I saw those calculations a while ago - it was in a book called >>>> "The Bicycle Wheel", I think. >>> Dear J., >>> >>> Here's Jobst's diagram in "The Bicycle Wheel," for anyone curious >>> about specifics, as opposed to the rhetorical questions and >>> why-don't-you-look-it-up so common on RBT: >>> >>> http://i12.tinypic.com/2dako69.jpg >> thanks carl, but that's not what i was trying to describe - i was >> talking about the angle that results from having a 2.0mm spoke in a >> 2.4mm hub hole for a 3.4mm flange thickness. >> >>> Jobst's diagram shows spoke angles from hub to rim of 7.3 and 3.5 >>> degrees. >> which is how the hub is canted. >> >>> So a slightly widened 95-degree elbow angle is reasonable for inner >>> spokes that may be at 97.3~93.5 degrees. >> if the hub flange is canted, the spoke angle is from the point raised >> for the spoke not sitting square in the larger hub hole, not from the >> angle associated with flange spacing. > > I'm not sure what this means. Did you mean to say "sitting square" instead > of "not sitting square"? If it didn't matter whether the spoke was sitting > square, what would be the relevance of canting? spokes angle towards a rim at say 6 degrees both sides front, and say 6 + 3 for rears. and that is what hub flanges are canted to. in addition, hub holes are angled perpendicular to the flange, so they too are aligned for optimal spoke position. see: http://www.flickr.com/photos/38636024@N00/316202144/ http://www.flickr.com/photos/38636024@N00/316202143/ > >>> (Various front and rear hub widths probably don't change the angles >>> much for 700c cross-3 wheels. Spoke elbows on tiny wheels for Moultons >>> and recumbents may suffer from the orthopedic problems that afflict >>> many dwarves, but small rims usually make very strong wheels.) >>> >>> Jobst recommends bending outer spokes enough to lie flat on the hub >>> flange (and bending all spokes enough at the rim to "correct the spoke >>> line.") >>> >>> Sapim disagrees. Here's their FAQ comment on 95 degree elbow angles >>> and whether spokes should be bent ("forced") to change the angle: >>> >>> "If material is forced while lacing the hub, the spokes can be pulled >>> over causing material weakness." >>> >>> "The original bend angle of 95� should remain intact." >>> >>> http://www.sapim.be/index.php?st=fa >>> >>> Elsewhere in "The Bicycle Wheel," Jobst mentions that steel spokes >>> will bed into aluminum hubs, which have largely replaced the steel >>> hubs that were popular when his first edition came out: >>> >>> "When spokes are properly tensioned the aluminum flange material on >>> which they bear is usually under enough stress to conform to the >>> spokes." --p. 59, "The Bicycle Wheel," 3rd edition, Jobst Brandt >> they do indeed. >> http://www.flickr.com/photos/38636024@N00/104463818/ >> >>> There's a good drawing of a "Spoke Seating in the Flange" next to the >>> text quoted above (and oodles more interesting stuff, such as >>> correcting the spoke line), but anyone interested will need to get >>> their own copy . . . >>> >>> http://sheldonbrown.com/harris/books.html#brandt >>> >>> Cheers, >>> >>> Carl Fogel       Date: 23 Dec 2006 21:01:13 From: Ron Ruff Subject: Re: I fixed a broken spoke! jobst.brandt@stanfordalumni.org wrote: > The diagrams and data are in radial and tangential dimensions. Spoke > tension changes can be derived from cross section and length change, > all of which are given. Length changes are not given... at least not in the 2nd edition... unless you mean the radial deflection of the nodes. The tangential deflection adds a lot to this, but it is easy enough to calculate. > This is about effects not absolute quantities. As I mentioned the > vectors shown are all the same size, braking, torque, and radial load. > I think the data and diagrams are clearly ked, considering all the > reviews by engineers that were made before publishing. I must be missing the cheat sheet... :) Now that I know that "torque = 50" means a 50kg (?) load applied tangent to a 300mm radius rim, and that "spoke angle = 5" means that the spokes are angled 5 degrees from perpendicular to the rim, I have enough info to calculate the tension change. A 5 degree angle gives an effective hub radius of 26.5mm. So plugging in the numbers I get the following. The first numbers use your torque values directly, and the second converts to an equivalent force at the crank with a 2 to1 gear ratio: Effective flange radius (mm) 26.5 26.5 Crank length (mm) 300 170 Front sprocket teeth 1 2 Rear sprocket teeth 1 1 Crossed spokes on drive side 36 36 Force exerted on crank (kg) 50 176.5 Spoke diameter (mm) 1.6 1.6 Spoke length (mm) 300 300 Spoke area (mm^2) 2.01 2.01 Spoke tension change +-(kg) 15.7 15.7 Spoke length change +-(mm) 0.112 0.112 Note that this is an average tension change. Since the rim distorts, the peak variation is somewhat larger... I calculated a maximum length change from your FEM values of 0.147mm, or about 31% higher. These *are* pretty small values... but they don't represent a "worst case" for the effect of torsion on spoke tension. For one thing, to have 36 spokes involved equally in resisting torque you would need a 36 hole hub (rare these days) and an infinitely stiff hub body (impossible). In your book you include an analysis at the end where you calculate that the left side of the hub (even with 3x) contributes only 12% to the torsional stiffness. Most modern hubs are stiffer than this... but radial lacing on the NDS is also common. Radial spokes on the NDS will transfer essentially zero torque when the DS is crossed. There are plenty of rear wheels with 20 spokes and half radial... some are even more extreme: http://tinyurl.com/ym2uxd And obviously highly valued... even with a dent. Also, an effective flange radius of 26.5 is a bit larger than average... ~20mm is more normal and is par for Shimano hubs with 3x. Again, if I plug in the numbers for a hypothetical yet perfectly "normal" wheel (these days at least), I get: Effective flange radius (mm) 20 Crank length (mm) 175 Front sprocket teeth 34 Rear sprocket teeth 25 Crossed spokes on drive side 10 Force exerted on crank (kg) 150 Spoke diameter (mm) 1.60 Spoke length (mm) 280 Spoke area (mm^2) 1.89 Spoke tension change +-(kg) 96.5 Spoke length change +-(mm) 0.661 And this isn't trivial at all. That is very near what spokes are tensioned at to start with. In your book (2nd edition) you show charts (fig 69) indicating that DT butted 1.8/1.6mm spokes will clearly yield at ~175kg. So, if you build a wheel like the one shown above with 95kg tension on the drive side, you can yield the trailing spokes and send the leading ones to zero tension via torque alone. I'll admit that the case shown above is rather extreme... but it was my intention to show an extreme case (though not the most extreme case that is out there). Some riders may never subject their equipment (and their bodies) to a full power uphill sprint in a low gear... but I do that occasionally. If you put your bike in the lowest gear at a stoplight and take off with your full weight on the crank, then you will achieve half the torque I've modeled here (if you weigh 75kg that is). I think that a 150kg max force is very reasonable. The wheels I am presently riding are 32, 3x, with a fairly large diameter hub body, so if I assume that the left flange contributes 25% to stiffness, I essentially have 1.33*16= 21.3 spokes involved in torsion, dropping the spoke tension change to 45.3 kg instead of 96.5 kg. That is a value I feel a little more comfortable with. Conclusion? Torsion should not be ignored when designing and building wheels. There are plenty of wheel configurations out there now that are pushing and exceeding the limit of what the spokes can take... and it is no mystery that failures occur.         Date: 23 Dec 2006 21:05:55 From: jim beam Subject: Re: I fixed a broken spoke! Ron Ruff wrote: > jobst.brandt@stanfordalumni.org wrote: >> The diagrams and data are in radial and tangential dimensions. Spoke >> tension changes can be derived from cross section and length change, >> all of which are given. > > Length changes are not given... at least not in the 2nd edition... > unless you mean the radial deflection of the nodes. The tangential > deflection adds a lot to this, but it is easy enough to calculate. > >> This is about effects not absolute quantities. As I mentioned the >> vectors shown are all the same size, braking, torque, and radial load. >> I think the data and diagrams are clearly ked, considering all the >> reviews by engineers that were made before publishing. > > I must be missing the cheat sheet... :) > > Now that I know that "torque = 50" means a 50kg (?) load applied > tangent to a 300mm radius rim, and that "spoke angle = 5" means that > the spokes are angled 5 degrees from perpendicular to the rim, I have > enough info to calculate the tension change. A 5 degree angle gives an > effective hub radius of 26.5mm. So plugging in the numbers I get the > following. The first numbers use your torque values directly, and the > second converts to an equivalent force at the crank with a 2 to1 gear > ratio: > > Effective flange radius (mm) 26.5 26.5 > Crank length (mm) 300 170 > Front sprocket teeth 1 2 > Rear sprocket teeth 1 1 > Crossed spokes on drive side 36 36 > Force exerted on crank (kg) 50 176.5 > Spoke diameter (mm) 1.6 1.6 > Spoke length (mm) 300 300 > Spoke area (mm^2) 2.01 2.01 > > Spoke tension change +-(kg) 15.7 15.7 > Spoke length change +-(mm) 0.112 0.112 > > Note that this is an average tension change. Since the rim distorts, > the peak variation is somewhat larger... I calculated a maximum length > change from your FEM values of 0.147mm, or about 31% higher. > > These *are* pretty small values... but they don't represent a "worst > case" for the effect of torsion on spoke tension. For one thing, to > have 36 spokes involved equally in resisting torque you would need a 36 > hole hub (rare these days) and an infinitely stiff hub body > (impossible). In your book you include an analysis at the end where you > calculate that the left side of the hub (even with 3x) contributes only > 12% to the torsional stiffness. Most modern hubs are stiffer than > this... but radial lacing on the NDS is also common. Radial spokes on > the NDS will transfer essentially zero torque when the DS is crossed. > > There are plenty of rear wheels with 20 spokes and half radial... some > are even more extreme: > > http://tinyurl.com/ym2uxd > > And obviously highly valued... even with a dent. > > Also, an effective flange radius of 26.5 is a bit larger than > average... ~20mm is more normal and is par for Shimano hubs with 3x. > > Again, if I plug in the numbers for a hypothetical yet perfectly > "normal" wheel (these days at least), I get: > > Effective flange radius (mm) 20 > Crank length (mm) 175 > Front sprocket teeth 34 > Rear sprocket teeth 25 > Crossed spokes on drive side 10 > Force exerted on crank (kg) 150 > Spoke diameter (mm) 1.60 > Spoke length (mm) 280 > Spoke area (mm^2) 1.89 > > Spoke tension change +-(kg) 96.5 > Spoke length change +-(mm) 0.661 > > And this isn't trivial at all. That is very near what spokes are > tensioned at to start with. In your book (2nd edition) you show charts > (fig 69) indicating that DT butted 1.8/1.6mm spokes will clearly yield > at ~175kg. So, if you build a wheel like the one shown above with 95kg > tension on the drive side, you can yield the trailing spokes and send > the leading ones to zero tension via torque alone. > > I'll admit that the case shown above is rather extreme... but it was my > intention to show an extreme case (though not the most extreme case > that is out there). Some riders may never subject their equipment (and > their bodies) to a full power uphill sprint in a low gear... but I do > that occasionally. If you put your bike in the lowest gear at a > stoplight and take off with your full weight on the crank, then you > will achieve half the torque I've modeled here (if you weigh 75kg that > is). I think that a 150kg max force is very reasonable. > > The wheels I am presently riding are 32, 3x, with a fairly large > diameter hub body, so if I assume that the left flange contributes 25% > to stiffness, I essentially have 1.33*16= 21.3 spokes involved in > torsion, dropping the spoke tension change to 45.3 kg instead of 96.5 > kg. That is a value I feel a little more comfortable with. > > Conclusion? Torsion should not be ignored when designing and building > wheels. There are plenty of wheel configurations out there now that are > pushing and exceeding the limit of what the spokes can take... and it > is no mystery that failures occur. > very interesting - thanks ron!       Date: 20 Dec 2006 15:06:58 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > spokes angle towards a rim at say 6 degrees both sides front, and say 6 > + 3 for rears. and that is what hub flanges are canted to. in > addition, hub holes are angled perpendicular to the flange, so they too > are aligned for optimal spoke position. > > see: > http://www.flickr.com/photos/38636024@N00/316202144/ > http://www.flickr.com/photos/38636024@N00/316202143/ I find your "pencil test" a bit unconvincing. I have a new, never spoked, LX rear hub (Shimano SH-FHM570-32). I found that a 8d finish nail is almost an interference fit in the spoke holes. I can state with absolute certainty that the holes are drilled parallel to the axle, not perpendicular to the flange.         Date: 21 Dec 2006 05:43:00 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > jim beam wrote: > >> spokes angle towards a rim at say 6 degrees both sides front, and say >> 6 + 3 for rears. and that is what hub flanges are canted to. in >> addition, hub holes are angled perpendicular to the flange, so they >> too are aligned for optimal spoke position. >> >> see: >> http://www.flickr.com/photos/38636024@N00/316202144/ >> http://www.flickr.com/photos/38636024@N00/316202143/ > > I find your "pencil test" a bit unconvincing. > > I have a new, never spoked, LX rear hub (Shimano SH-FHM570-32). I found > that a 8d finish nail is almost an interference fit in the spoke holes. > I can state with absolute certainty that the holes are drilled parallel > to the axle, not perpendicular to the flange. ok, i accept that. maybe it's a high flange vs. low flange thing. maybe it's a quality level thing - mine was xt. but my hub /definitely/ has holes perpendicular to the canted flange. but all this is dodging the fundamental questions: 1. does or does not hub hole conformation lessen the required spoke angle? 2. does or does not "correcting the spoke line" /prior/ to hub hole conformation exaggerate the "correction", i.e. make it excessive? 3. how does elastic stress from an undeformed spoke bending toward the rim compare to that where the spoke bends around its interleaving partner? from what i can see, the angle is very similar so skin stress has to be of similar magnitude.           Date: 21 Dec 2006 10:54:04 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > Peter Cole wrote: >> I find your "pencil test" a bit unconvincing. >> >> I have a new, never spoked, LX rear hub (Shimano SH-FHM570-32). I >> found that a 8d finish nail is almost an interference fit in the spoke >> holes. I can state with absolute certainty that the holes are drilled >> parallel to the axle, not perpendicular to the flange. > > ok, i accept that. maybe it's a high flange vs. low flange thing. > maybe it's a quality level thing - mine was xt. but my hub /definitely/ > has holes perpendicular to the canted flange. > > but all this is dodging the fundamental questions: If you say so, but I'd still like to see evidence of a hub drilled perpendicular to the flange. > 1. does or does not hub hole conformation lessen the required spoke angle? > 2. does or does not "correcting the spoke line" /prior/ to hub hole > conformation exaggerate the "correction", i.e. make it excessive? > 3. how does elastic stress from an undeformed spoke bending toward the > rim compare to that where the spoke bends around its interleaving > partner? from what i can see, the angle is very similar so skin stress > has to be of similar magnitude. First, I'm not aware of anyone (other than Sheldon, & I don't agree with him) correcting the spoke line before the wheel is tensioned, so I'm not sure who you're arguing with. In all of the above cases, the only important thing is that the spoke take as straight a line as possible. If the spoke has a bend in it, the spoke will flex under change of tension, accelerating fatigue. If, after the wheel is tensioned, the spokes have a bow in them where they exit the flange, it is necessary to correct the line to prevent flex in operation. If they don't, it isn't. The elbow is a critical fatigue location, the crossover is not. The only spokes I have ever seen break at places other than the elbow or threads were chain-nicked.             Date: 21 Dec 2006 10:22:15 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > jim beam wrote: >> Peter Cole wrote: > >>> I find your "pencil test" a bit unconvincing. >>> >>> I have a new, never spoked, LX rear hub (Shimano SH-FHM570-32). I >>> found that a 8d finish nail is almost an interference fit in the >>> spoke holes. I can state with absolute certainty that the holes are >>> drilled parallel to the axle, not perpendicular to the flange. >> >> ok, i accept that. maybe it's a high flange vs. low flange thing. >> maybe it's a quality level thing - mine was xt. but my hub /definitely/ >> has holes perpendicular to the canted flange. >> >> but all this is dodging the fundamental questions: > > If you say so, but I'd still like to see evidence of a hub drilled > perpendicular to the flange. i gave you a pic peter! the pencil may not have been a wise choice of indicator for a hardened disbeliever like you, but i assure you, it's jammed in so it's perpendicular to the hole - the wood deforms to a cylinder that perfectly fits and is square to the pencil axis on removal. > > >> 1. does or does not hub hole conformation lessen the required spoke >> angle? >> 2. does or does not "correcting the spoke line" /prior/ to hub hole >> conformation exaggerate the "correction", i.e. make it excessive? >> 3. how does elastic stress from an undeformed spoke bending toward the >> rim compare to that where the spoke bends around its interleaving >> partner? from what i can see, the angle is very similar so skin stress >> has to be of similar magnitude. > > First, I'm not aware of anyone (other than Sheldon, & I don't agree with > him) correcting the spoke line before the wheel is tensioned, so I'm not > sure who you're arguing with. jobst brandt!!! its specifically stated in "the book"! > > In all of the above cases, the only important thing is that the spoke > take as straight a line as possible. If the spoke has a bend in it, the > spoke will flex under change of tension, accelerating fatigue. no, the spoke elbow is fundamentally going to flex regardless. the elbow's offset means load is non-axial, hence the elbow /will/ bend. and it is /that/ which causes fatigue, not the ethereal dragon that is alleged to be "stress relief". > If, after > the wheel is tensioned, the spokes have a bow in them where they exit > the flange, it is necessary to correct the line to prevent flex in > operation. but if that's true, it should also include the necessity to "correct" the bow at interleaving crossover! > If they don't, it isn't. The elbow is a critical fatigue > location, the crossover is not. agreed. but we may have different reasoning for that. to me, the crossover is subcritical because the straightening of the loading cycle runs /with/ it's natural shape and is /not/ fighting an offset like the elbow. additionally, it's not subject to the surface defects that inevitably accompany a bending operation like elbow forming. "orange peel effect". > The only spokes I have ever seen break > at places other than the elbow or threads were chain-nicked. indeed. and they are surface defects.               Date: 21 Dec 2006 14:55:36 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > Peter Cole wrote: >> jim beam wrote: >>> Peter Cole wrote: >> >>>> I find your "pencil test" a bit unconvincing. >>>> >>>> I have a new, never spoked, LX rear hub (Shimano SH-FHM570-32). I >>>> found that a 8d finish nail is almost an interference fit in the >>>> spoke holes. I can state with absolute certainty that the holes are >>>> drilled parallel to the axle, not perpendicular to the flange. >>> >>> ok, i accept that. maybe it's a high flange vs. low flange thing. >>> maybe it's a quality level thing - mine was xt. but my hub /definitely/ >>> has holes perpendicular to the canted flange. >>> >>> but all this is dodging the fundamental questions: >> >> If you say so, but I'd still like to see evidence of a hub drilled >> perpendicular to the flange. > > i gave you a pic peter! the pencil may not have been a wise choice of > indicator for a hardened disbeliever like you, but i assure you, it's > jammed in so it's perpendicular to the hole - the wood deforms to a > cylinder that perfectly fits and is square to the pencil axis on removal. I tried a pencil first, too, and I could believe that the hole was canted. I tried various other things that weren't a tight fit and found them equally ambiguous. It wasn't until I found something with an interference fit that I became convinced that the holes were not canted. > >> >> >>> 1. does or does not hub hole conformation lessen the required spoke >>> angle? >>> 2. does or does not "correcting the spoke line" /prior/ to hub hole >>> conformation exaggerate the "correction", i.e. make it excessive? >>> 3. how does elastic stress from an undeformed spoke bending toward the >>> rim compare to that where the spoke bends around its interleaving >>> partner? from what i can see, the angle is very similar so skin stress >>> has to be of similar magnitude. >> >> First, I'm not aware of anyone (other than Sheldon, & I don't agree >> with him) correcting the spoke line before the wheel is tensioned, so >> I'm not sure who you're arguing with. > > jobst brandt!!! its specifically stated in "the book"! Not from my reading (which I quoted earlier). The step is described after the section on tensioning. Furthermore, he expressed it in terms of the spoke "may" need correction. If a wheel is brought up to tension, and the spokes still have an overly obtuse angle (as evidenced by bowing out from the flange), I think that needs correction -- the spoke path is not in line with the load path. It's Mavic who seem to propose stress relieving a partially tensioned wheel -- for reasons I don't understand (nor do they, I'm willing to bet). If you claim that all failed elbows you've examined failed from the outside (as BenC says), then I don't understand why you're concerned about an over acute elbow angle. That would put extra tension on the inside of the bend. Perhaps all your spokes fail on the outside because you haven't corrected the spoke line an have an over obtuse angle. >> In all of the above cases, the only important thing is that the spoke >> take as straight a line as possible. If the spoke has a bend in it, >> the spoke will flex under change of tension, accelerating fatigue. > > no, the spoke elbow is fundamentally going to flex regardless. the > elbow's offset means load is non-axial, hence the elbow /will/ bend. and > it is /that/ which causes fatigue, not the ethereal dragon that is > alleged to be "stress relief". If the spoke line matches the load line the spoke won't bend with changes in load. >> If, after the wheel is tensioned, the spokes have a bow in them where >> they exit the flange, it is necessary to correct the line to prevent >> flex in operation. > > but if that's true, it should also include the necessity to "correct" > the bow at interleaving crossover! Since spokes have finite thickness, the spoke line has to deviate slightly from the load line, there's no way to correct for that. > >> If they don't, it isn't. The elbow is a critical fatigue location, the >> crossover is not. > > agreed. but we may have different reasoning for that. to me, the > crossover is subcritical because the straightening of the loading cycle > runs /with/ it's natural shape and is /not/ fighting an offset like the > elbow. additionally, it's not subject to the surface defects that > inevitably accompany a bending operation like elbow forming. "orange > peel effect". I think it's because the bend angle is much smaller and the spokes support each other and prevent much bending.                 Date: 21 Dec 2006 15:20:21 From: Ben C Subject: Re: I fixed a broken spoke! On 2006-12-21, Peter Cole <peter_cole@comcast.net > wrote: [snip] > If you claim that all failed elbows you've examined failed from the > outside (as BenC says) Misunderstanding: by "outside" I meant the outside _surface_, i.e. the exterior of the wire, not the outside of the bend. IIRC jim beam had examined failed spokes with a microscope and found that fatigue had started (nucleated) on the exterior, never on the interior, where there are no surface cracks or imperfections since there's no surface. The point is that the residual stress would be in the interior, although I'm still reading your post about skin stresses and neutral planes and things. The ratio of failures that start on the exterior outside the bend to ones that start on the exterior inside the bend may also be interesting, but noone's claimed it's 1:0.                 Date: 21 Dec 2006 12:26:55 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > jim beam wrote: >> Peter Cole wrote: >>> jim beam wrote: >>>> Peter Cole wrote: >>> >>>>> I find your "pencil test" a bit unconvincing. >>>>> >>>>> I have a new, never spoked, LX rear hub (Shimano SH-FHM570-32). I >>>>> found that a 8d finish nail is almost an interference fit in the >>>>> spoke holes. I can state with absolute certainty that the holes are >>>>> drilled parallel to the axle, not perpendicular to the flange. >>>> >>>> ok, i accept that. maybe it's a high flange vs. low flange thing. >>>> maybe it's a quality level thing - mine was xt. but my hub >>>> /definitely/ >>>> has holes perpendicular to the canted flange. >>>> >>>> but all this is dodging the fundamental questions: >>> >>> If you say so, but I'd still like to see evidence of a hub drilled >>> perpendicular to the flange. >> >> i gave you a pic peter! the pencil may not have been a wise choice of >> indicator for a hardened disbeliever like you, but i assure you, it's >> jammed in so it's perpendicular to the hole - the wood deforms to a >> cylinder that perfectly fits and is square to the pencil axis on removal. > > I tried a pencil first, too, and I could believe that the hole was > canted. I tried various other things that weren't a tight fit and found > them equally ambiguous. It wasn't until I found something with an > interference fit that I became convinced that the holes were not canted. well, i accept that it may be different for different hubs, but i am certain of the situation regarding the hub i tested. > > > >> >>> >>> >>>> 1. does or does not hub hole conformation lessen the required spoke >>>> angle? >>>> 2. does or does not "correcting the spoke line" /prior/ to hub hole >>>> conformation exaggerate the "correction", i.e. make it excessive? >>>> 3. how does elastic stress from an undeformed spoke bending toward the >>>> rim compare to that where the spoke bends around its interleaving >>>> partner? from what i can see, the angle is very similar so skin stress >>>> has to be of similar magnitude. >>> >>> First, I'm not aware of anyone (other than Sheldon, & I don't agree >>> with him) correcting the spoke line before the wheel is tensioned, so >>> I'm not sure who you're arguing with. >> >> jobst brandt!!! its specifically stated in "the book"! > > Not from my reading (which I quoted earlier). The step is described > after the section on tensioning. Furthermore, he expressed it in terms > of the spoke "may" need correction. > > If a wheel is brought up to tension, and the spokes still have an overly > obtuse angle (as evidenced by bowing out from the flange), I think that > needs correction -- the spoke path is not in line with the load path. but again, "correcting" prior to hub hole deformation has the spoke out of the load line too! do you dispute the geometry i illustrated? > > It's Mavic who seem to propose stress relieving a partially tensioned > wheel -- for reasons I don't understand (nor do they, I'm willing to bet). presumably because, just like they were st enough to figure out that j-bend spokes are fundamentally fatigue challenged, they also realized that seating was essential /before/ anything else that could influence final spoke line. > > If you claim that all failed elbows you've examined failed from the > outside (as BenC says), then I don't understand why you're concerned > about an over acute elbow angle. i don't claim that. it's roughly 4:1 outside to inside. and again, "outside" the elbow is different from the skin which is where 100% of fatigue initiates. > That would put extra tension on the > inside of the bend. Perhaps all your spokes fail on the outside because > you haven't corrected the spoke line an have an over obtuse angle. see above. > > >>> In all of the above cases, the only important thing is that the spoke >>> take as straight a line as possible. If the spoke has a bend in it, >>> the spoke will flex under change of tension, accelerating fatigue. >> >> no, the spoke elbow is fundamentally going to flex regardless. the >> elbow's offset means load is non-axial, hence the elbow /will/ bend. >> and it is /that/ which causes fatigue, not the ethereal dragon that is >> alleged to be "stress relief". > > If the spoke line matches the load line the spoke won't bend with > changes in load. but it fundamentally /cannot/ match the load line for a j-bend spoke, only straight pull. > > >>> If, after the wheel is tensioned, the spokes have a bow in them where >>> they exit the flange, it is necessary to correct the line to prevent >>> flex in operation. >> >> but if that's true, it should also include the necessity to "correct" >> the bow at interleaving crossover! > > Since spokes have finite thickness, the spoke line has to deviate > slightly from the load line, there's no way to correct for that. straight pull spokes address it as effectively as you could wish. j-bend fundamentally cannot. > > >> >>> If they don't, it isn't. The elbow is a critical fatigue location, >>> the crossover is not. >> >> agreed. but we may have different reasoning for that. to me, the >> crossover is subcritical because the straightening of the loading >> cycle runs /with/ it's natural shape and is /not/ fighting an offset >> like the elbow. additionally, it's not subject to the surface defects >> that inevitably accompany a bending operation like elbow forming. >> "orange peel effect". > > I think it's because the bend angle is much smaller and the spokes > support each other and prevent much bending. do the math for the stress in the outer skin at the bend [3-point] - you'll be surprised.                   Date: 21 Dec 2006 16:40:05 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > Peter Cole wrote: >> If a wheel is brought up to tension, and the spokes still have an >> overly obtuse angle (as evidenced by bowing out from the flange), I >> think that needs correction -- the spoke path is not in line with the >> load path. > > but again, "correcting" prior to hub hole deformation has the spoke out > of the load line too! do you dispute the geometry i illustrated? I saw nothing to dispute, just simple trig. A pin in a plate with clearance will cant. If you put a load on the pin, the hole may wallow and the pin cant further. Most of the wallowing must occur during initial spoke tension (compared to any additional during stress relieving and/or riding). If, after tensioning (and associated wallowing) the spoke angle is still too obtuse, it must be corrected, or the spoke will flex during load cycles. Furthermore, if the load brings the spoke near yield, it will operate at that point, drastically reducing fatigue life. That's why most of your spokes failed at the outside of the bend. >> It's Mavic who seem to propose stress relieving a partially tensioned >> wheel -- for reasons I don't understand (nor do they, I'm willing to >> bet). > > presumably because, just like they were st enough to figure out that > j-bend spokes are fundamentally fatigue challenged, they also realized > that seating was essential /before/ anything else that could influence > final spoke line. Most seating is accomplished by initial tensioning. By stress relieving a partially tensioned wheel, they run at least some risk of over correcting the spoke line. Their method (pressing down on the rim while supporting the axle) could yield both the holes and the spoke bends. I think it's safest to correct a fully tensioned wheel as Jobst indicates, and then only if it needs it, as he also says. > >> >> If you claim that all failed elbows you've examined failed from the >> outside (as BenC says), then I don't understand why you're concerned >> about an over acute elbow angle. > > i don't claim that. it's roughly 4:1 outside to inside. and again, > "outside" the elbow is different from the skin which is where 100% of > fatigue initiates. > >> That would put extra tension on the inside of the bend. Perhaps all >> your spokes fail on the outside because you haven't corrected the >> spoke line an have an over obtuse angle. > > see above. Ditto. >> If the spoke line matches the load line the spoke won't bend with >> changes in load. > > but it fundamentally /cannot/ match the load line for a j-bend spoke, > only straight pull. Why not? > straight pull spokes address it as effectively as you could wish. j-bend > fundamentally cannot. Why not? >> >> >>> >>>> If they don't, it isn't. The elbow is a critical fatigue location, >>>> the crossover is not. >>> >>> agreed. but we may have different reasoning for that. to me, the >>> crossover is subcritical because the straightening of the loading >>> cycle runs /with/ it's natural shape and is /not/ fighting an offset >>> like the elbow. additionally, it's not subject to the surface >>> defects that inevitably accompany a bending operation like elbow >>> forming. "orange peel effect". >> >> I think it's because the bend angle is much smaller and the spokes >> support each other and prevent much bending. > > do the math for the stress in the outer skin at the bend [3-point] - > you'll be surprised. Since spokes don't take a permanent bend at the crossing, yet they do at hub exit, the former aren't at/near yield, the latter are (as Jobst points out).                     Date: 21 Dec 2006 13:59:45 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > jim beam wrote: >> Peter Cole wrote: > >>> If a wheel is brought up to tension, and the spokes still have an >>> overly obtuse angle (as evidenced by bowing out from the flange), I >>> think that needs correction -- the spoke path is not in line with the >>> load path. >> >> but again, "correcting" prior to hub hole deformation has the spoke >> out of the load line too! do you dispute the geometry i illustrated? > > I saw nothing to dispute, just simple trig. right, and that trig supports the spoke angle at which spokes are manufactured, not arbitrarily bent. > > A pin in a plate with clearance will cant. If you put a load on the pin, > the hole may wallow and the pin cant further. Most of the wallowing must > occur during initial spoke tension (compared to any additional during > stress relieving and/or riding). but by definition, if subsequent loading makes it "wallow" deeper, then something is occurring during riding to make it occurred. and that is tension increase, not decrease. if you think about it, that's also what's happening when you "stress relieve" a wheel in the truing stand. it's /definitely/ happing when you use the mavic method. > > If, after tensioning (and associated wallowing) the spoke angle is still > too obtuse, it must be corrected, or the spoke will flex during load > cycles. no, it's going to flex anyway. it has no choice because it's offset from the load axis. > Furthermore, if the load brings the spoke near yield, it will > operate at that point, drastically reducing fatigue life. That's why > most of your spokes failed at the outside of the bend. but "residual stress theory" has /compressive/ residual stress on the outside of the bend... > > >>> It's Mavic who seem to propose stress relieving a partially tensioned >>> wheel -- for reasons I don't understand (nor do they, I'm willing to >>> bet). >> >> presumably because, just like they were st enough to figure out >> that j-bend spokes are fundamentally fatigue challenged, they also >> realized that seating was essential /before/ anything else that could >> influence final spoke line. > > Most seating is accomplished by initial tensioning. not if you employ the mavic method. spokes can be seated before any significant tension is applied. > > By stress relieving a partially tensioned wheel, they run at least some > risk of over correcting the spoke line. thank you! > Their method (pressing down on > the rim while supporting the axle) could yield both the holes and the > spoke bends. I think it's safest to correct a fully tensioned wheel as > Jobst indicates, and then only if it needs it, as he also says. i agree with what you say, but jobst says to bend before the spokes are tensioned, and that's premature. > > >> >>> >>> If you claim that all failed elbows you've examined failed from the >>> outside (as BenC says), then I don't understand why you're concerned >>> about an over acute elbow angle. >> >> i don't claim that. it's roughly 4:1 outside to inside. and again, >> "outside" the elbow is different from the skin which is where 100% of >> fatigue initiates. >> >>> That would put extra tension on the inside of the bend. Perhaps all >>> your spokes fail on the outside because you haven't corrected the >>> spoke line an have an over obtuse angle. >> >> see above. > > Ditto. > > >>> If the spoke line matches the load line the spoke won't bend with >>> changes in load. >> >> but it fundamentally /cannot/ match the load line for a j-bend spoke, >> only straight pull. > > Why not? because the load is offset from the axis of the spoke? > > >> straight pull spokes address it as effectively as you could wish. >> j-bend fundamentally cannot. > > Why not? because the load is offset from the axis of the spoke? shall i do a diagram? > >>> >>> >>>> >>>>> If they don't, it isn't. The elbow is a critical fatigue location, >>>>> the crossover is not. >>>> >>>> agreed. but we may have different reasoning for that. to me, the >>>> crossover is subcritical because the straightening of the loading >>>> cycle runs /with/ it's natural shape and is /not/ fighting an offset >>>> like the elbow. additionally, it's not subject to the surface >>>> defects that inevitably accompany a bending operation like elbow >>>> forming. "orange peel effect". >>> >>> I think it's because the bend angle is much smaller and the spokes >>> support each other and prevent much bending. >> >> do the math for the stress in the outer skin at the bend [3-point] - >> you'll be surprised. > > Since spokes don't take a permanent bend at the crossing, yet they do at > hub exit, the former aren't at/near yield, the latter are (as Jobst > points out). i have some used spokes that show no difference between inner and outer bends, hence they were not yielded by being laced & tensioned. and that's supported by "simple trig", so i don't buy elbow bending as being inevitable - more likely the result of over-enthusiasm.                       Date: 22 Dec 2006 09:54:44 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > Peter Cole wrote: >> jim beam wrote: >>> Peter Cole wrote: >> >>>> If a wheel is brought up to tension, and the spokes still have an >>>> overly obtuse angle (as evidenced by bowing out from the flange), I >>>> think that needs correction -- the spoke path is not in line with >>>> the load path. >>> >>> but again, "correcting" prior to hub hole deformation has the spoke >>> out of the load line too! do you dispute the geometry i illustrated? >> >> I saw nothing to dispute, just simple trig. > > right, and that trig supports the spoke angle at which spokes are > manufactured, not arbitrarily bent. I don't draw that conclusion. > >> >> A pin in a plate with clearance will cant. If you put a load on the >> pin, the hole may wallow and the pin cant further. Most of the >> wallowing must occur during initial spoke tension (compared to any >> additional during stress relieving and/or riding). > > but by definition, if subsequent loading makes it "wallow" deeper, then > something is occurring during riding to make it occurred. and that is > tension increase, not decrease. > > if you think about it, that's also what's happening when you "stress > relieve" a wheel in the truing stand. it's /definitely/ happing when > you use the mavic method. If you think about deformation at the spoke hole you'll realize that the contact is initially a line (zero area, infinite stress) and grows to a certain size area until equilibrium is reached (force/area < yield). The process is non-linear in the sense that the contact area grows non-linearly with force, so that the majority of deformation occurs at the beginning of loading and tapers off as the load increases. >> If, after tensioning (and associated wallowing) the spoke angle is >> still too obtuse, it must be corrected, or the spoke will flex during >> load cycles. > > no, it's going to flex anyway. it has no choice because it's offset > from the load axis. If the inside radius of the elbow is completely supported by the flange, how can it flex? It is not able to move. >> Furthermore, if the load brings the spoke near yield, it will operate >> at that point, drastically reducing fatigue life. That's why most of >> your spokes failed at the outside of the bend. > > but "residual stress theory" has /compressive/ residual stress on the > outside of the bend... I'm talking about obtuse angles. If the spoke angle is too obtuse, load will make the angle more acute, causing tensile stress in the outside (elbow) skin. If the (initial) spoke angle was obtuse enough to cause slight yield (bend) during tensioning, then the stress on the skin will remain just below yield during the (short) operational life of the spoke. If the spoke bows out from the flange after tensioning, the angle is too obtuse, and the outside (elbow) with remain under (additional) tension, perhaps near yield. >>>> It's Mavic who seem to propose stress relieving a partially >>>> tensioned wheel -- for reasons I don't understand (nor do they, I'm >>>> willing to bet). >>> >>> presumably because, just like they were st enough to figure out >>> that j-bend spokes are fundamentally fatigue challenged, they also >>> realized that seating was essential /before/ anything else that could >>> influence final spoke line. >> >> Most seating is accomplished by initial tensioning. > > not if you employ the mavic method. spokes can be seated before any > significant tension is applied. I don't know what you mean by "significant". The Mavic method has you apply about half the final tension, then stress relieve, then fully tension and stress relieve again. >> By stress relieving a partially tensioned wheel, they run at least >> some risk of over correcting the spoke line. > > thank you! > >> Their method (pressing down on the rim while supporting the axle) >> could yield both the holes and the spoke bends. I think it's safest to >> correct a fully tensioned wheel as Jobst indicates, and then only if >> it needs it, as he also says. > > i agree with what you say, but jobst says to bend before the spokes are > tensioned, and that's premature. No, he doesn't -- at least not in his book. I don't know why you keep repeating this. The more I think about the Mavic method, the more I think it may be more effective than I first gave it credit for. Consider that you have a wheel, newly built, with perhaps some spokes deviating from the ideal spoke line one way or the other (acute or obtuse). If you simply tension the wheel like that, all of those less-than-ideal spoke angles are going to contribute a static stress (from bending) which may stay at/near yield if the lines are so bad as to cause plastic deformation (even slight -- especially slight!) during (normal) tensioning. As Sheldon points out, it's much easier to correct a spoke line in an untensioned wheel, but I'd point out that it's also much easier to over correct. With Mavic's method, the partial tension is perhaps a happy compromise. When the rim is half tensioned, the spoke line is more easily correctable, but the danger of over doing it is reduced. When you perform the process again, under full tension, the increased stiffness of the rim makes the amount of "correction" applied even less, very much like Jobst's "degaussing-analogy" description of wire stress relieving. There is no other reason I can think of for Mavic's "2-step" process. It can't be for "flange seating" since most of that will occur with the wheel half tensioned, anyway. If the amount of stress relief applied at that step more or less equals final tension, then any additional seating would be identically achieved just by bringing the overall tension up. The real reason must be correction of the spoke line. Pressing down with full body weight on opposite sides of the rim (with hub supported) on a half-tensioned wheel would yield those spots (whether from too acute or obtuse angles) where stresses were already high. Doing it a second time would apply yet higher aggregate tensions, but through smaller (offset) angles.                         Date: 22 Dec 2006 08:42:30 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > jim beam wrote: >> Peter Cole wrote: >>> jim beam wrote: >>>> Peter Cole wrote: >>> >>>>> If a wheel is brought up to tension, and the spokes still have an >>>>> overly obtuse angle (as evidenced by bowing out from the flange), I >>>>> think that needs correction -- the spoke path is not in line with >>>>> the load path. >>>> >>>> but again, "correcting" prior to hub hole deformation has the spoke >>>> out of the load line too! do you dispute the geometry i illustrated? >>> >>> I saw nothing to dispute, just simple trig. >> >> right, and that trig supports the spoke angle at which spokes are >> manufactured, not arbitrarily bent. > > I don't draw that conclusion. what's not clear about it? what conclusion /do/ you draw? > > >> >>> >>> A pin in a plate with clearance will cant. If you put a load on the >>> pin, the hole may wallow and the pin cant further. Most of the >>> wallowing must occur during initial spoke tension (compared to any >>> additional during stress relieving and/or riding). >> >> but by definition, if subsequent loading makes it "wallow" deeper, >> then something is occurring during riding to make it occurred. and >> that is tension increase, not decrease. >> >> if you think about it, that's also what's happening when you "stress >> relieve" a wheel in the truing stand. it's /definitely/ happing when >> you use the mavic method. > > If you think about deformation at the spoke hole you'll realize that the > contact is initially a line (zero area, infinite stress) and grows to a > certain size area until equilibrium is reached (force/area < yield). The > process is non-linear in the sense that the contact area grows > non-linearly with force, so that the majority of deformation occurs at > the beginning of loading and tapers off as the load increases. majority of deformation, yes, but not all. as you say, load/area equilibrium depends on load applied. load when "stress relieving" therefore needs to exceed that experienced in service or else it will occur when the wheel's in use and so send the wheel out of true. > > >>> If, after tensioning (and associated wallowing) the spoke angle is >>> still too obtuse, it must be corrected, or the spoke will flex during >>> load cycles. >> >> no, it's going to flex anyway. it has no choice because it's offset >> from the load axis. > > If the inside radius of the elbow is completely supported by the flange, > how can it flex? It is not able to move. peter, normally, you're a decent analyst, but here, you're not getting it. any component, experiencing any load, is subject to distortion. again, /any/ component experiencing /any/ load. the earth's crust is experiencing loading distortion at the point where my ass is loading the chair which is loading the floor which is loading the walls which are pressing on the earth where i sit. the distortion may not be much, but it's there. and it's measurable. now, here we have a spoke whose load is offset from the spoke axis by the length of the elbow shank. the elbow will therefore bend on loading. period. that bending will "amplify" the stress experienced in the skin of the spoke by the leverage exerted. real simple. now add cyclic loading, surface quality irregularities, microstructure irregularities, and we have fatigue. end of story. with a straight pull spoke in contrast, there is no bending, no leverage, and therefore, no stress concentrated at any particular zone in the spoke's skin. the load is spread throughout the spoke. and hence we see no fatigue. > > >>> Furthermore, if the load brings the spoke near yield, it will operate >>> at that point, drastically reducing fatigue life. That's why most of >>> your spokes failed at the outside of the bend. >> >> but "residual stress theory" has /compressive/ residual stress on the >> outside of the bend... > > I'm talking about obtuse angles. If the spoke angle is too obtuse, load > will make the angle more acute, causing tensile stress in the outside > (elbow) skin. If the (initial) spoke angle was obtuse enough to cause > slight yield (bend) during tensioning, then the stress on the skin will > remain just below yield during the (short) operational life of the > spoke. If the spoke bows out from the flange after tensioning, the angle > is too obtuse, and the outside (elbow) with remain under (additional) > tension, perhaps near yield. but how does hub hole distortion on yielding affect that angle? [rhetorical] > >>>>> It's Mavic who seem to propose stress relieving a partially >>>>> tensioned wheel -- for reasons I don't understand (nor do they, I'm >>>>> willing to bet). >>>> >>>> presumably because, just like they were st enough to figure out >>>> that j-bend spokes are fundamentally fatigue challenged, they also >>>> realized that seating was essential /before/ anything else that >>>> could influence final spoke line. >>> >>> Most seating is accomplished by initial tensioning. >> >> not if you employ the mavic method. spokes can be seated before any >> significant tension is applied. > > I don't know what you mean by "significant". The Mavic method has you > apply about half the final tension, then stress relieve, then fully > tension and stress relieve again. ok, /you/ can apply the leaning method long before mavic say to do so. > >>> By stress relieving a partially tensioned wheel, they run at least >>> some risk of over correcting the spoke line. >> >> thank you! >> >>> Their method (pressing down on the rim while supporting the axle) >>> could yield both the holes and the spoke bends. I think it's safest >>> to correct a fully tensioned wheel as Jobst indicates, and then only >>> if it needs it, as he also says. >> >> i agree with what you say, but jobst says to bend before the spokes >> are tensioned, and that's premature. > > No, he doesn't -- at least not in his book. I don't know why you keep > repeating this. maybe you read a different version of the book to me? it clearly has a section on "correcting the spoke line" that's spoke bending. and he says to do it after lacing, but before tensioning. and because that precedes hub hole deformation, it can't account for final spoke angle and is therefore premature. i don't understand what's hard to understand about that. > > > The more I think about the Mavic method, the more I think it may be more > effective than I first gave it credit for. Consider that you have a > wheel, newly built, with perhaps some spokes deviating from the ideal > spoke line one way or the other (acute or obtuse). If you simply tension > the wheel like that, all of those less-than-ideal spoke angles are going > to contribute a static stress (from bending) which may stay at/near > yield if the lines are so bad as to cause plastic deformation (even > slight -- especially slight!) during (normal) tensioning. > > As Sheldon points out, it's much easier to correct a spoke line in an > untensioned wheel, but I'd point out that it's also much easier to over > correct. With Mavic's method, the partial tension is perhaps a happy > compromise. When the rim is half tensioned, the spoke line is more > easily correctable, but the danger of over doing it is reduced. if you want to think of it that way, sure. personally, i never "correct" and my wheels last just fine. > When you > perform the process again, under full tension, the increased stiffness > of the rim makes the amount of "correction" applied even less, very much > like Jobst's "degaussing-analogy" description of wire stress relieving. that's an appalling analogy. > > There is no other reason I can think of for Mavic's "2-step" process. It > can't be for "flange seating" since most of that will occur with the > wheel half tensioned, anyway. i simply don't accept that - it does not accord with the experience of anyone witnessing a wheel go out of true when "stress relieving" in the truing stand and watching it go out of true, and it doesn't accord with basic deformation theory. > If the amount of stress relief applied at > that step more or less equals final tension, then any additional seating > would be identically achieved just by bringing the overall tension up. except that spoke tension in static loading is not the highest the wheel will ever experience in service - as proved by my "round the block" experiment. > The real reason must be correction of the spoke line. you're trying to twist the facts to fit your preconception. > Pressing down with > full body weight on opposite sides of the rim (with hub supported) on a > half-tensioned wheel would yield those spots (whether from too acute or > obtuse angles) where stresses were already high. Doing it a second time > would apply yet higher aggregate tensions, but through smaller (offset) > angles.                           Date: 22 Dec 2006 12:37:55 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > Peter Cole wrote: >> jim beam wrote: >>> Peter Cole wrote: >>>> jim beam wrote: >>>>> but again, "correcting" prior to hub hole deformation has the spoke >>>>> out of the load line too! do you dispute the geometry i illustrated? >>>> >>>> I saw nothing to dispute, just simple trig. >>> >>> right, and that trig supports the spoke angle at which spokes are >>> manufactured, not arbitrarily bent. >> >> I don't draw that conclusion. > > what's not clear about it? what conclusion /do/ you draw? None. > majority of deformation, yes, but not all. as you say, load/area > equilibrium depends on load applied. load when "stress relieving" > therefore needs to exceed that experienced in service or else it will > occur when the wheel's in use and so send the wheel out of true. Yes, perhaps, but we're discussing fatigue. >> If the inside radius of the elbow is completely supported by the >> flange, how can it flex? It is not able to move. > now, here we have a spoke whose load is offset from the spoke axis by > the length of the elbow shank. the elbow will therefore bend on > loading. period. that bending will "amplify" the stress experienced in > the skin of the spoke by the leverage exerted. real simple. now add > cyclic loading, surface quality irregularities, microstructure > irregularities, and we have fatigue. end of story. If the spoke is constrained from moving, it can't move, hence it can't bend. End of story. >>>> Furthermore, if the load brings the spoke near yield, it will >>>> operate at that point, drastically reducing fatigue life. That's why >>>> most of your spokes failed at the outside of the bend. >>> >>> but "residual stress theory" has /compressive/ residual stress on the >>> outside of the bend... >> >> I'm talking about obtuse angles. If the spoke angle is too obtuse, >> load will make the angle more acute, causing tensile stress in the >> outside (elbow) skin. If the (initial) spoke angle was obtuse enough >> to cause slight yield (bend) during tensioning, then the stress on the >> skin will remain just below yield during the (short) operational life >> of the spoke. If the spoke bows out from the flange after tensioning, >> the angle is too obtuse, and the outside (elbow) with remain under >> (additional) tension, perhaps near yield. > > but how does hub hole distortion on yielding affect that angle? > [rhetorical] It doesn't matter if, at the end of tensioning, the angle is still too obtuse. >> I don't know what you mean by "significant". The Mavic method has you >> apply about half the final tension, then stress relieve, then fully >> tension and stress relieve again. > > ok, /you/ can apply the leaning method long before mavic say to do so. Read it yourself: <http://home.comcast.net/~carlfogel/download/SpokeTension.pdf > >>> i agree with what you say, but jobst says to bend before the spokes >>> are tensioned, and that's premature. >> >> No, he doesn't -- at least not in his book. I don't know why you keep >> repeating this. > > maybe you read a different version of the book to me? it clearly has a > section on "correcting the spoke line" that's spoke bending. and he > says to do it after lacing, but before tensioning. and because that > precedes hub hole deformation, it can't account for final spoke angle > and is therefore premature. i don't understand what's hard to > understand about that. I have the third edition. In Part II "Building and Repairing Wheels", under the section "Tensioning the Wheel" (pg. 95), there are six sub-sections: "Warning", "Taking Out the Slack", "Making Them Tight", "Spoke Twist", "Tension by Tone", and finally "Correcting the Spoke Line". Does your copy have these sections in a different order? >> If the amount of stress relief applied at that step more or less >> equals final tension, then any additional seating would be identically >> achieved just by bringing the overall tension up. > > except that spoke tension in static loading is not the highest the wheel > will ever experience in service - as proved by my "round the block" > experiment. When you ride an un-stress relieved wheel "around the block", "honking up hills", as I said before, you can put lateral loads on the wheel, which will nominally increase (some) spoke tension. Bear in mind that the contact patch is also loaded vertically, so you are first reducing static tension, then superimposing a (potentially large) lateral load. What this does, more than force additional flange seating, is to yield the spoke line to the load line, essentially "correcting the spoke line" somewhat. That will shorten the spoke path and reduce static tension. Your own experiences seem to confirm the need to correct the spoke line. The outcomes you describe are entirely consistent with this. >> The real reason must be correction of the spoke line. > > you're trying to twist the facts to fit your preconception. I don't think so.                             Date: 23 Dec 2006 13:59:58 From: Michael Press Subject: Re: I fixed a broken spoke! In article <TICdnXGelcpuihHYnZ2dnUVZ_rrinZ2d@comcast.com >, Peter Cole <peter_cole@comcast.net > wrote: > >>> i agree with what you say, but jobst says to bend before the spokes > >>> are tensioned, and that's premature. > >> > >> No, he doesn't -- at least not in his book. I don't know why you keep > >> repeating this. > > > > maybe you read a different version of the book to me? it clearly has a > > section on "correcting the spoke line" that's spoke bending. and he > > says to do it after lacing, but before tensioning. and because that > > precedes hub hole deformation, it can't account for final spoke angle > > and is therefore premature. i don't understand what's hard to > > understand about that. > > I have the third edition. In Part II "Building and Repairing Wheels", > under the section "Tensioning the Wheel" (pg. 95), there are six > sub-sections: "Warning", "Taking Out the Slack", "Making Them Tight", > "Spoke Twist", "Tension by Tone", and finally "Correcting the Spoke Line". > > Does your copy have these sections in a different order? Correcting the spoke line appears in two places: page 72 and page 96. -- Michael Press                               Date: 23 Dec 2006 17:24:00 From: Peter Cole Subject: Re: I fixed a broken spoke! Michael Press wrote: > In article > <TICdnXGelcpuihHYnZ2dnUVZ_rrinZ2d@comcast.com>, > Peter Cole <peter_cole@comcast.net> wrote: > >>>>> i agree with what you say, but jobst says to bend before the spokes >>>>> are tensioned, and that's premature. >>>> No, he doesn't -- at least not in his book. I don't know why you keep >>>> repeating this. >>> maybe you read a different version of the book to me? it clearly has a >>> section on "correcting the spoke line" that's spoke bending. and he >>> says to do it after lacing, but before tensioning. and because that >>> precedes hub hole deformation, it can't account for final spoke angle >>> and is therefore premature. i don't understand what's hard to >>> understand about that. >> I have the third edition. In Part II "Building and Repairing Wheels", >> under the section "Tensioning the Wheel" (pg. 95), there are six >> sub-sections: "Warning", "Taking Out the Slack", "Making Them Tight", >> "Spoke Twist", "Tension by Tone", and finally "Correcting the Spoke Line". >> >> Does your copy have these sections in a different order? > > Correcting the spoke line appears in two places: page > 72 and page 96. > Yes, it does, sorry for the omission. On page 72: "..After tensioning the lines of the spokes in a new wheel must be corrected to achieve this condition." I think this should be clear enough even to jim beam.                                 Date: 23 Dec 2006 14:30:25 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > Michael Press wrote: >> In article <TICdnXGelcpuihHYnZ2dnUVZ_rrinZ2d@comcast.com>, >> Peter Cole <peter_cole@comcast.net> wrote: >> >>>>>> i agree with what you say, but jobst says to bend before the >>>>>> spokes are tensioned, and that's premature. >>>>> No, he doesn't -- at least not in his book. I don't know why you >>>>> keep repeating this. >>>> maybe you read a different version of the book to me? it clearly >>>> has a section on "correcting the spoke line" that's spoke bending. >>>> and he says to do it after lacing, but before tensioning. and >>>> because that precedes hub hole deformation, it can't account for >>>> final spoke angle and is therefore premature. i don't understand >>>> what's hard to understand about that. >>> I have the third edition. In Part II "Building and Repairing Wheels", >>> under the section "Tensioning the Wheel" (pg. 95), there are six >>> sub-sections: "Warning", "Taking Out the Slack", "Making Them Tight", >>> "Spoke Twist", "Tension by Tone", and finally "Correcting the Spoke >>> Line". >>> >>> Does your copy have these sections in a different order? >> >> Correcting the spoke line appears in two places: page 72 and page 96. >> > Yes, it does, sorry for the omission. > > On page 72: > > "..After tensioning the lines of the spokes in a new wheel must be > corrected to achieve this condition." > > I think this should be clear enough even to jim beam. it's clear now!                             Date: 22 Dec 2006 18:02:01 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > jim beam wrote: >> Peter Cole wrote: >>> jim beam wrote: >>>> Peter Cole wrote: >>>>> jim beam wrote: > >>>>>> but again, "correcting" prior to hub hole deformation has the >>>>>> spoke out of the load line too! do you dispute the geometry i >>>>>> illustrated? >>>>> >>>>> I saw nothing to dispute, just simple trig. >>>> >>>> right, and that trig supports the spoke angle at which spokes are >>>> manufactured, not arbitrarily bent. >>> >>> I don't draw that conclusion. >> >> what's not clear about it? what conclusion /do/ you draw? > > None. yes you do. you disagree. that means taking a contrary position. i want you to state that and analyze it. > >> majority of deformation, yes, but not all. as you say, load/area >> equilibrium depends on load applied. load when "stress relieving" >> therefore needs to exceed that experienced in service or else it will >> occur when the wheel's in use and so send the wheel out of true. > > Yes, perhaps, but we're discussing fatigue. cop out. /you/ were discussing spoke seating. i responded. not you're avoiding the question. > > >>> If the inside radius of the elbow is completely supported by the >>> flange, how can it flex? It is not able to move. > >> now, here we have a spoke whose load is offset from the spoke axis by >> the length of the elbow shank. the elbow will therefore bend on >> loading. period. that bending will "amplify" the stress experienced >> in the skin of the spoke by the leverage exerted. real simple. now >> add cyclic loading, surface quality irregularities, microstructure >> irregularities, and we have fatigue. end of story. > > If the spoke is constrained from moving, it can't move, hence it can't > bend. End of story. that is a serious misunderstanding. where do you think fatigue comes from? by definition, if it fatigues, it's experiencing strain, in this case, bending. > > >>>>> Furthermore, if the load brings the spoke near yield, it will >>>>> operate at that point, drastically reducing fatigue life. That's >>>>> why most of your spokes failed at the outside of the bend. >>>> >>>> but "residual stress theory" has /compressive/ residual stress on >>>> the outside of the bend... >>> >>> I'm talking about obtuse angles. If the spoke angle is too obtuse, >>> load will make the angle more acute, causing tensile stress in the >>> outside (elbow) skin. If the (initial) spoke angle was obtuse enough >>> to cause slight yield (bend) during tensioning, then the stress on >>> the skin will remain just below yield during the (short) operational >>> life of the spoke. If the spoke bows out from the flange after >>> tensioning, the angle is too obtuse, and the outside (elbow) with >>> remain under (additional) tension, perhaps near yield. >> >> but how does hub hole distortion on yielding affect that angle? >> [rhetorical] > > It doesn't matter if, at the end of tensioning, the angle is still too > obtuse. no peter, you're dodging again. i demonstrated the effect of spoke seating on the need to bend the spoke. address the question. > > >>> I don't know what you mean by "significant". The Mavic method has you >>> apply about half the final tension, then stress relieve, then fully >>> tension and stress relieve again. >> >> ok, /you/ can apply the leaning method long before mavic say to do so. > > Read it yourself: > <http://home.comcast.net/~carlfogel/download/SpokeTension.pdf> /i/ mailed that to carl. and i have read it. you're avoiding my point. again. > > >>>> i agree with what you say, but jobst says to bend before the spokes >>>> are tensioned, and that's premature. >>> >>> No, he doesn't -- at least not in his book. I don't know why you keep >>> repeating this. >> >> maybe you read a different version of the book to me? it clearly has >> a section on "correcting the spoke line" that's spoke bending. and >> he says to do it after lacing, but before tensioning. and because >> that precedes hub hole deformation, it can't account for final spoke >> angle and is therefore premature. i don't understand what's hard to >> understand about that. > > I have the third edition. In Part II "Building and Repairing Wheels", > under the section "Tensioning the Wheel" (pg. 95), there are six > sub-sections: "Warning", "Taking Out the Slack", "Making Them Tight", > "Spoke Twist", "Tension by Tone", and finally "Correcting the Spoke Line". > > Does your copy have these sections in a different order? so you /do/ have "correcting the spoke line"! and what does it say there? > > >>> If the amount of stress relief applied at that step more or less >>> equals final tension, then any additional seating would be >>> identically achieved just by bringing the overall tension up. >> >> except that spoke tension in static loading is not the highest the >> wheel will ever experience in service - as proved by my "round the >> block" experiment. > > When you ride an un-stress relieved wheel "around the block", "honking > up hills", as I said before, you can put lateral loads on the wheel, > which will nominally increase (some) spoke tension. ok, we agree. > Bear in mind that > the contact patch is also loaded vertically, so you are first reducing > static tension, then superimposing a (potentially large) lateral load. ok. > What this does, more than force additional flange seating, is to yield > the spoke line to the load line, essentially "correcting the spoke line" > somewhat. elastically, not plastically. > That will shorten the spoke path and reduce static tension. i don't buy that. the rim bends too - that pulls the spokes further from the flange. tension increase is related to 1/sin theta. > > Your own experiences seem to confirm the need to correct the spoke line. > The outcomes you describe are entirely consistent with this. no, you're trying to twist my words to suit your prejudice. > > >>> The real reason must be correction of the spoke line. >> >> you're trying to twist the facts to fit your preconception. > > I don't think so. but you've just done it again on almost every point in this response!                               Date: 23 Dec 2006 09:23:17 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > Peter Cole wrote: >> jim beam wrote: >>> Peter Cole wrote: >>>> jim beam wrote: >>>>> Peter Cole wrote: >>>>>> jim beam wrote: >> >>>>>>> but again, "correcting" prior to hub hole deformation has the >>>>>>> spoke out of the load line too! do you dispute the geometry i >>>>>>> illustrated? >>>>>> >>>>>> I saw nothing to dispute, just simple trig. >>>>> >>>>> right, and that trig supports the spoke angle at which spokes are >>>>> manufactured, not arbitrarily bent. >>>> >>>> I don't draw that conclusion. >>> >>> what's not clear about it? what conclusion /do/ you draw? >> >> None. > > yes you do. you disagree. that means taking a contrary position. i > want you to state that and analyze it. You are conjecturing that the combination of cant (in a less than interference fit) and flange deformation will combine to make the spoke "factory" angle perfect. You also claim that some flange holes are drilled canted, while I measured at least one (common) one that wasn't. How could both yield a perfect match to factory angle? Theory, in this case, really is academic. If the spoke, after tensioning, has a noticeable bow at the flange, the angle is not perfect and should be adjusted. That's all Jobst's book says. >>> majority of deformation, yes, but not all. as you say, load/area >>> equilibrium depends on load applied. load when "stress relieving" >>> therefore needs to exceed that experienced in service or else it will >>> occur when the wheel's in use and so send the wheel out of true. >> >> Yes, perhaps, but we're discussing fatigue. > > cop out. /you/ were discussing spoke seating. i responded. not you're > avoiding the question. Change in tension after stress relieving may come from plastic deformation of the flange or spoke. I think analysis shows it to be more likely to be predominated by spoke yield. That's not to say that there's no additional flange yield, just that it's not the important factor that you make it out to be. >>>> If the inside radius of the elbow is completely supported by the >>>> flange, how can it flex? It is not able to move. >> >>> now, here we have a spoke whose load is offset from the spoke axis by >>> the length of the elbow shank. the elbow will therefore bend on >>> loading. period. that bending will "amplify" the stress experienced >>> in the skin of the spoke by the leverage exerted. real simple. now >>> add cyclic loading, surface quality irregularities, microstructure >>> irregularities, and we have fatigue. end of story. >> >> If the spoke is constrained from moving, it can't move, hence it can't >> bend. End of story. > > that is a serious misunderstanding. where do you think fatigue comes > from? by definition, if it fatigues, it's experiencing strain, in this > case, bending. But you haven't explained how a fully supported spoke can bend. >>>>>> Furthermore, if the load brings the spoke near yield, it will >>>>>> operate at that point, drastically reducing fatigue life. That's >>>>>> why most of your spokes failed at the outside of the bend. >>>>> >>>>> but "residual stress theory" has /compressive/ residual stress on >>>>> the outside of the bend... >>>> >>>> I'm talking about obtuse angles. If the spoke angle is too obtuse, >>>> load will make the angle more acute, causing tensile stress in the >>>> outside (elbow) skin. If the (initial) spoke angle was obtuse enough >>>> to cause slight yield (bend) during tensioning, then the stress on >>>> the skin will remain just below yield during the (short) operational >>>> life of the spoke. If the spoke bows out from the flange after >>>> tensioning, the angle is too obtuse, and the outside (elbow) with >>>> remain under (additional) tension, perhaps near yield. >>> >>> but how does hub hole distortion on yielding affect that angle? >>> [rhetorical] >> >> It doesn't matter if, at the end of tensioning, the angle is still too >> obtuse. > > no peter, you're dodging again. i demonstrated the effect of spoke > seating on the need to bend the spoke. address the question. No, you conjectured. The proof is in the pudding. If the spoke is too obtuse, it won't lay flat on the flange, and should be corrected. If the spoke does lay flat, it's still possible that it was over corrected or the factory angle was too acute. >>>> I don't know what you mean by "significant". The Mavic method has >>>> you apply about half the final tension, then stress relieve, then >>>> fully tension and stress relieve again. >>> >>> ok, /you/ can apply the leaning method long before mavic say to do so. >> >> Read it yourself: >> <http://home.comcast.net/~carlfogel/download/SpokeTension.pdf> > > /i/ mailed that to carl. and i have read it. you're avoiding my point. > again. Well, then how am I "applying the Mavic method long before they say to"? Perhaps you should reread it to refresh your memory. >>>>> i agree with what you say, but jobst says to bend before the spokes >>>>> are tensioned, and that's premature. >>>> >>>> No, he doesn't -- at least not in his book. I don't know why you >>>> keep repeating this. >>> >>> maybe you read a different version of the book to me? it clearly has >>> a section on "correcting the spoke line" that's spoke bending. and >>> he says to do it after lacing, but before tensioning. and because >>> that precedes hub hole deformation, it can't account for final spoke >>> angle and is therefore premature. i don't understand what's hard to >>> understand about that. >> >> I have the third edition. In Part II "Building and Repairing Wheels", >> under the section "Tensioning the Wheel" (pg. 95), there are six >> sub-sections: "Warning", "Taking Out the Slack", "Making Them Tight", >> "Spoke Twist", "Tension by Tone", and finally "Correcting the Spoke >> Line". >> >> Does your copy have these sections in a different order? > > so you /do/ have "correcting the spoke line"! and what does it say there? I quoted this verbatim in an earlier post, and I have paraphrased it several times since (including in this post). You're simply misrepresenting what he said. > >> >> >>>> If the amount of stress relief applied at that step more or less >>>> equals final tension, then any additional seating would be >>>> identically achieved just by bringing the overall tension up. >>> >>> except that spoke tension in static loading is not the highest the >>> wheel will ever experience in service - as proved by my "round the >>> block" experiment. >> >> When you ride an un-stress relieved wheel "around the block", "honking >> up hills", as I said before, you can put lateral loads on the wheel, >> which will nominally increase (some) spoke tension. > > ok, we agree. > >> Bear in mind that the contact patch is also loaded vertically, so you >> are first reducing static tension, then superimposing a (potentially >> large) lateral load. > > ok. > >> What this does, more than force additional flange seating, is to yield >> the spoke line to the load line, essentially "correcting the spoke >> line" somewhat. > > elastically, not plastically. Not necessarily. Obviously not so if the spokes are close to yield at the start (as they might well be if the angle was too acute/obtuse). >> That will shorten the spoke path and reduce static tension. > > i don't buy that. the rim bends too - that pulls the spokes further > from the flange. tension increase is related to 1/sin theta. You don't buy what? That riding loads don't deflect the rim and lower spoke tension? >> Your own experiences seem to confirm the need to correct the spoke >> line. The outcomes you describe are entirely consistent with this. > > no, you're trying to twist my words to suit your prejudice. > >> >> >>>> The real reason must be correction of the spoke line. >>> >>> you're trying to twist the facts to fit your preconception. >> >> I don't think so. > > but you've just done it again on almost every point in this response! You're the one who is misrepresenting both Jobst and Mavic. I don't think I'm misrepresenting your experiences with slacking and breaking spokes -- just trying to explain them to you.                                 Date: 23 Dec 2006 15:10:45 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > jim beam wrote: >> Peter Cole wrote: >>> jim beam wrote: >>>> Peter Cole wrote: >>>>> jim beam wrote: >>>>>> Peter Cole wrote: >>>>>>> jim beam wrote: >>> >>>>>>>> but again, "correcting" prior to hub hole deformation has the >>>>>>>> spoke out of the load line too! do you dispute the geometry i >>>>>>>> illustrated? >>>>>>> >>>>>>> I saw nothing to dispute, just simple trig. >>>>>> >>>>>> right, and that trig supports the spoke angle at which spokes are >>>>>> manufactured, not arbitrarily bent. >>>>> >>>>> I don't draw that conclusion. >>>> >>>> what's not clear about it? what conclusion /do/ you draw? >>> >>> None. >> >> yes you do. you disagree. that means taking a contrary position. i >> want you to state that and analyze it. > > You are conjecturing that the combination of cant (in a less than > interference fit) and flange deformation will combine to make the spoke > "factory" angle perfect. You also claim that some flange holes are > drilled canted, while I measured at least one (common) one that wasn't. > How could both yield a perfect match to factory angle? if the flange is canted /and/ drilled correctly, factory spoke angle is perfect. if the flange is either uncanted or drilled parallel to the hub axis, then factory spoke angle may indeed not be perfect. solution: buy better hubs. > > Theory, in this case, really is academic. If the spoke, after > tensioning, has a noticeable bow at the flange, the angle is not perfect > and should be adjusted. That's all Jobst's book says. and i'm saying that it's advice that is premature and doesn't consider the obvious effects that result from hub hole deformation. > > >>>> majority of deformation, yes, but not all. as you say, load/area >>>> equilibrium depends on load applied. load when "stress relieving" >>>> therefore needs to exceed that experienced in service or else it >>>> will occur when the wheel's in use and so send the wheel out of true. >>> >>> Yes, perhaps, but we're discussing fatigue. >> >> cop out. /you/ were discussing spoke seating. i responded. not >> you're avoiding the question. > > Change in tension after stress relieving may come from plastic > deformation of the flange or spoke. I think analysis shows it to be more > likely to be predominated by spoke yield. That's not to say that there's > no additional flange yield, just that it's not the important factor that > you make it out to be. so how are you going to judge which is which? you're using a supposition about spoke yield to suit your argument, which is unproven, whereas hub hole yield, which is obvious and easily observed, you're trying to trivialize. now, are you going to say that this pic is evidence of misrepresentation? http://www.flickr.com/photos/38636024@N00/331112190/ > > > >>>>> If the inside radius of the elbow is completely supported by the >>>>> flange, how can it flex? It is not able to move. >>> >>>> now, here we have a spoke whose load is offset from the spoke axis >>>> by the length of the elbow shank. the elbow will therefore bend on >>>> loading. period. that bending will "amplify" the stress >>>> experienced in the skin of the spoke by the leverage exerted. real >>>> simple. now add cyclic loading, surface quality irregularities, >>>> microstructure irregularities, and we have fatigue. end of story. >>> >>> If the spoke is constrained from moving, it can't move, hence it >>> can't bend. End of story. >> >> that is a serious misunderstanding. where do you think fatigue comes >> from? by definition, if it fatigues, it's experiencing strain, in >> this case, bending. > > But you haven't explained how a fully supported spoke can bend. peter, with respect, you're either conceptually blocked /or/ you're avoiding the question. if there is not a completely straight line between two points, whatever is joining them will bend. the load point of a spoke is not axial to the spoke, it's offset by the elbow. if you don't see that, i'm not sure we can debate it further because you're not getting it. if you're denying it, that's a whole other ball of wax. > > >>>>>>> Furthermore, if the load brings the spoke near yield, it will >>>>>>> operate at that point, drastically reducing fatigue life. That's >>>>>>> why most of your spokes failed at the outside of the bend. >>>>>> >>>>>> but "residual stress theory" has /compressive/ residual stress on >>>>>> the outside of the bend... >>>>> >>>>> I'm talking about obtuse angles. If the spoke angle is too obtuse, >>>>> load will make the angle more acute, causing tensile stress in the >>>>> outside (elbow) skin. If the (initial) spoke angle was obtuse >>>>> enough to cause slight yield (bend) during tensioning, then the >>>>> stress on the skin will remain just below yield during the (short) >>>>> operational life of the spoke. If the spoke bows out from the >>>>> flange after tensioning, the angle is too obtuse, and the outside >>>>> (elbow) with remain under (additional) tension, perhaps near yield. >>>> >>>> but how does hub hole distortion on yielding affect that angle? >>>> [rhetorical] >>> >>> It doesn't matter if, at the end of tensioning, the angle is still >>> too obtuse. >> >> no peter, you're dodging again. i demonstrated the effect of spoke >> seating on the need to bend the spoke. address the question. > > No, you conjectured. The proof is in the pudding. If the spoke is too > obtuse, it won't lay flat on the flange, and should be corrected. If the > spoke does lay flat, it's still possible that it was over corrected or > the factory angle was too acute. so at which point does it require correction? hopefully we now agree that bending prior to hub hole deformation is premature. and if the hub hole has deformed and the spoke is full tensioned, you're not going to see anything other than a correctly aligned spoke. > > > >>>>> I don't know what you mean by "significant". The Mavic method has >>>>> you apply about half the final tension, then stress relieve, then >>>>> fully tension and stress relieve again. >>>> >>>> ok, /you/ can apply the leaning method long before mavic say to do so. >>> >>> Read it yourself: >>> <http://home.comcast.net/~carlfogel/download/SpokeTension.pdf> >> >> /i/ mailed that to carl. and i have read it. you're avoiding my >> point. again. > > Well, then how am I "applying the Mavic method long before they say to"? > Perhaps you should reread it to refresh your memory. no dude, you're twisting my words again. i've said repeatedly that you can use the "mavic method" [as in pressing on opposite sides of the rim] even when spokes are slack. and you can. now you're trying to say that's b.s. because mavic say to start the process after the wheel is partially tensioned. hence you're avoiding my point. > > >>>>>> i agree with what you say, but jobst says to bend before the >>>>>> spokes are tensioned, and that's premature. >>>>> >>>>> No, he doesn't -- at least not in his book. I don't know why you >>>>> keep repeating this. >>>> >>>> maybe you read a different version of the book to me? it clearly >>>> has a section on "correcting the spoke line" that's spoke bending. >>>> and he says to do it after lacing, but before tensioning. and >>>> because that precedes hub hole deformation, it can't account for >>>> final spoke angle and is therefore premature. i don't understand >>>> what's hard to understand about that. >>> >>> I have the third edition. In Part II "Building and Repairing Wheels", >>> under the section "Tensioning the Wheel" (pg. 95), there are six >>> sub-sections: "Warning", "Taking Out the Slack", "Making Them Tight", >>> "Spoke Twist", "Tension by Tone", and finally "Correcting the Spoke >>> Line". >>> >>> Does your copy have these sections in a different order? >> >> so you /do/ have "correcting the spoke line"! and what does it say >> there? > > I quoted this verbatim in an earlier post, and I have paraphrased it > several times since (including in this post). You're simply > misrepresenting what he said. i stand corrected on sequence. but that's maybe why i asked you for the quote. and maybe you'll talk with sheldon about that. but now i want to see how the line is supposed to be corrected on fully tensioned spoke wire! actually, i don't - i don't think it should be done at all. > > >> >>> >>> >>>>> If the amount of stress relief applied at that step more or less >>>>> equals final tension, then any additional seating would be >>>>> identically achieved just by bringing the overall tension up. >>>> >>>> except that spoke tension in static loading is not the highest the >>>> wheel will ever experience in service - as proved by my "round the >>>> block" experiment. >>> >>> When you ride an un-stress relieved wheel "around the block", >>> "honking up hills", as I said before, you can put lateral loads on >>> the wheel, which will nominally increase (some) spoke tension. >> >> ok, we agree. >> >>> Bear in mind that the contact patch is also loaded vertically, so you >>> are first reducing static tension, then superimposing a (potentially >>> large) lateral load. >> >> ok. >> >>> What this does, more than force additional flange seating, is to >>> yield the spoke line to the load line, essentially "correcting the >>> spoke line" somewhat. >> >> elastically, not plastically. > > Not necessarily. Obviously not so if the spokes are close to yield at > the start (as they might well be if the angle was too acute/obtuse). elastically. http://www.flickr.com/photos/38636024@N00/331112190/ > > > >>> That will shorten the spoke path and reduce static tension. >> >> i don't buy that. the rim bends too - that pulls the spokes further >> from the flange. tension increase is related to 1/sin theta. > > You don't buy what? That riding loads don't deflect the rim and lower > spoke tension? in axial loading, yes. that's why we were talking about lateral loading - hill honking, remember? > > >>> Your own experiences seem to confirm the need to correct the spoke >>> line. The outcomes you describe are entirely consistent with this. >> >> no, you're trying to twist my words to suit your prejudice. >> >>> >>> >>>>> The real reason must be correction of the spoke line. >>>> >>>> you're trying to twist the facts to fit your preconception. >>> >>> I don't think so. >> >> but you've just done it again on almost every point in this response! > > You're the one who is misrepresenting both Jobst and Mavic. I don't > think I'm misrepresenting your experiences with slacking and breaking > spokes -- just trying to explain them to you. hardly. waving your hands about spokes plastically deforming in preference to a soft aluminum hub flange, without benefit of evidence, isn't what i'd call explanation.                         Date: 22 Dec 2006 08:05:07 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > jim beam wrote: >> Peter Cole wrote: >>> jim beam wrote: >>>> Peter Cole wrote: >>> >>>>> If a wheel is brought up to tension, and the spokes still have an >>>>> overly obtuse angle (as evidenced by bowing out from the flange), I >>>>> think that needs correction -- the spoke path is not in line with >>>>> the load path. >>>> >>>> but again, "correcting" prior to hub hole deformation has the spoke >>>> out of the load line too! do you dispute the geometry i illustrated? >>> >>> I saw nothing to dispute, just simple trig. >> >> right, and that trig supports the spoke angle at which spokes are >> manufactured, not arbitrarily bent. > > I don't draw that conclusion. > > >> >>> >>> A pin in a plate with clearance will cant. If you put a load on the >>> pin, the hole may wallow and the pin cant further. Most of the >>> wallowing must occur during initial spoke tension (compared to any >>> additional during stress relieving and/or riding). >> >> but by definition, if subsequent loading makes it "wallow" deeper, >> then something is occurring during riding to make it occurred. and >> that is tension increase, not decrease. >> >> if you think about it, that's also what's happening when you "stress >> relieve" a wheel in the truing stand. it's /definitely/ happing when >> you use the mavic method. > > If you think about deformation at the spoke hole you'll realize that the > contact is initially a line (zero area, infinite stress) and grows to a > certain size area until equilibrium is reached (force/area < yield). The > process is non-linear in the sense that the contact area grows > non-linearly with force, so that the majority of deformation occurs at > the beginning of loading and tapers off as the load increases. > > >>> If, after tensioning (and associated wallowing) the spoke angle is >>> still too obtuse, it must be corrected, or the spoke will flex during >>> load cycles. >> >> no, it's going to flex anyway. it has no choice because it's offset >> from the load axis. > > If the inside radius of the elbow is completely supported by the flange, > how can it flex? It is not able to move. > > >>> Furthermore, if the load brings the spoke near yield, it will operate >>> at that point, drastically reducing fatigue life. That's why most of >>> your spokes failed at the outside of the bend. >> >> but "residual stress theory" has /compressive/ residual stress on the >> outside of the bend... > > I'm talking about obtuse angles. If the spoke angle is too obtuse, load > will make the angle more acute, causing tensile stress in the outside > (elbow) skin. If the (initial) spoke angle was obtuse enough to cause > slight yield (bend) during tensioning, then the stress on the skin will > remain just below yield during the (short) operational life of the > spoke. If the spoke bows out from the flange after tensioning, the angle > is too obtuse, and the outside (elbow) with remain under (additional) > tension, perhaps near yield. > >>>>> It's Mavic who seem to propose stress relieving a partially >>>>> tensioned wheel -- for reasons I don't understand (nor do they, I'm >>>>> willing to bet). >>>> >>>> presumably because, just like they were st enough to figure out >>>> that j-bend spokes are fundamentally fatigue challenged, they also >>>> realized that seating was essential /before/ anything else that >>>> could influence final spoke line. >>> >>> Most seating is accomplished by initial tensioning. >> >> not if you employ the mavic method. spokes can be seated before any >> significant tension is applied. > > I don't know what you mean by "significant". The Mavic method has you > apply about half the final tension, then stress relieve, then fully > tension and stress relieve again. > >>> By stress relieving a partially tensioned wheel, they run at least >>> some risk of over correcting the spoke line. >> >> thank you! >> >>> Their method (pressing down on the rim while supporting the axle) >>> could yield both the holes and the spoke bends. I think it's safest >>> to correct a fully tensioned wheel as Jobst indicates, and then only >>> if it needs it, as he also says. >> >> i agree with what you say, but jobst says to bend before the spokes >> are tensioned, and that's premature. > > No, he doesn't -- at least not in his book. I don't know why you keep > repeating this. > > > The more I think about the Mavic method, the more I think it may be more > effective than I first gave it credit for. Consider that you have a > wheel, newly built, with perhaps some spokes deviating from the ideal > spoke line one way or the other (acute or obtuse). If you simply tension > the wheel like that, all of those less-than-ideal spoke angles are going > to contribute a static stress (from bending) which may stay at/near > yield if the lines are so bad as to cause plastic deformation (even > slight -- especially slight!) during (normal) tensioning. > > As Sheldon points out, it's much easier to correct a spoke line in an > untensioned wheel, but I'd point out that it's also much easier to over > correct. With Mavic's method, the partial tension is perhaps a happy > compromise. When the rim is half tensioned, the spoke line is more > easily correctable, but the danger of over doing it is reduced. When you > perform the process again, under full tension, the increased stiffness > of the rim makes the amount of "correction" applied even less, very much > like Jobst's "degaussing-analogy" description of wire stress relieving. > > There is no other reason I can think of for Mavic's "2-step" process. It > can't be for "flange seating" since most of that will occur with the > wheel half tensioned, anyway. If the amount of stress relief applied at > that step more or less equals final tension, then any additional seating > would be identically achieved just by bringing the overall tension up. > The real reason must be correction of the spoke line. Pressing down with > full body weight on opposite sides of the rim (with hub supported) on a > half-tensioned wheel would yield those spots (whether from too acute or > obtuse angles) where stresses were already high. Doing it a second time > would apply yet higher aggregate tensions, but through smaller (offset) > angles.   Date: 19 Dec 2006 06:13:22 From: Gary Young Subject: Re: I fixed a broken spoke! On Tue, 19 Dec 2006 04:30:54 -0600, Gary Young wrote: > On Wed, 06 Dec 2006 21:09:48 -0800, jim beam wrote: > >> dvt wrote: >>> jim beam wrote: >>>> dvt wrote: >>>>> jim beam wrote: >>>>>> but given that the hub flanges are canted and that the angle which >>>>>> the spoke manufacturer already provides is already appropriate, >>>>>> there's no point in this exercise in the first place. >>> >>>>> You never answered this question the first time, so let's try again... >>> >>>> dave, some threads get too long and windy. if you want to /ensure/ i >>>> read a question that's somehow important, post a new thread. and make >>>> sure i'm not on vacation, traveling, otherwise busy or disinterested. >>> >>> Nice try, jim. Here's the record: >>> >>> <http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/1c072f5d8b7c8892/83a78e954c0f932d> >> >> is this the 'unanswered' question? >> "I've been watching this thread, hoping that I wasn't the only one with >> this question. How do you "cant and drill" a hole in the hub flange so >> that both inbound *and* outbound spokes are "optimized?" If the hole was >> so canted, would that mean that the hubs should not be deformed during >> the build?" >> >> if so, i'd have thought the answers obvious. maybe that's why i didn't >> bother answering. >> >>> >>> >>> Scroll down to messages 103-110. You responded to that exact subthread, >>> so I know you were reading it. But you failed to answer the question. >>> >>>>> In bound vs. out bound, crossing pattern, and rim size all affect the >>>>> angle in question. I don't see hubs keted for each variation, and >>>>> I don't see holes labeled for inbound and outbound spokes. Do small >>>>> wheels (think recumbent) usually use the same hubs as diamond frame >>>>> bikes? If so, do they have a much higher incidence of spoke breakage? >>> >>>> if you want to demonstrate something dave, do the math for the spoke >>>> angle given that a hub hole may be larger diameter than the spoke and >>>> seated in a flange of given thickness. then compare that to the stock >>>> spoke angle of ~95°. > > I think Dave has a point. Elsewhere you've suggested that spoke > manufacturers optimize the elbow angle based on the average configuration > (number of spokes, cross pattern, type of hub, etc.) Even if that's true, > and if spoke manufacturers really go to the extent you suggest to optimize > their spokes, you would expect things to be different on spokes so short > that they can only be used on smaller wheels. Does anyone have such a > spoke (e.g. a spoke for a bmx hub)? Is the angle different? Are the > flanges on bmx hubs canted at a different angle? > >>> >>> You made the claim. It's your job to prove it. Here's the claim you >>> made, in case you've forgotten: >>> >>> "the spoke elbow comes pre-formed with the best resultant angle and the >>> hub flange is canted and drilled also to give the best resultant angle." >>> >>> You made no reservations about wheel size, lacing pattern, or any of the >>> other things you tried to add in later when questioned. And what about >>> dished wheels? Or rims with offset spoke beds? >>> >>> I'm looking forward to your response. >>> >> unless you want a full custom hub, the economics don't support >> accommodating non-standard configurations. >> >> two hub pics for consideration: >> http://www.flickr.com/photos/38636024@N00/316202144/ >> http://www.flickr.com/photos/38636024@N00/316202143/ >> >> for the cynics, i didn't happen to have any 2.4mm rod about for the hub >> hole pic, but if you don't believe the hub holes are perpendicular to >> the flange, do this experiment yourself. > Please ignore everything below this point. I clearly wasn't thinking things through very well. > Is there anyone here who's denied that flanges are canted? Even with > canting, when you build a wheel, you can see that the outbound spokes > don't lie as flat against the flange as inbound spokes. If correcting the > spoke line were merely a premature way of bedding in the spokes, wouldn't > the same bulge be evident on both sides of the flange? > > While canting may make a gross correction in the spoke line, it > seems to me that canting in itself introduces a new difference in > the lines of inbound and outbound spokes (at least when using a > non-radial, cross-laced pattern). With a canted or funnel-like flange, as > in inbound spoke runs tangentially along the flange, it will be closer to > the edge of the flange than will an outbound spoke. In other words, it > will take a lesser amount of tension to bring the inbound spoke in contact > with the canted-in edge as it leaves the hub. Is there some way to > compensate for that without drilling the inbound spoke holes in a > different way than the outbound ones? Or making separate sets of inbound > and outbound spokes? > > I suppose the beveling of the spoke holes could compensate for that to a > certain degree, but it doesn't seem to do so entirely. I just put a spoke > in a unlaced LX front hub, first inbound and then outbound. It takes > noticeably greater force to bring the outbound spoke in contact with the > edge of the flange when the spoke leaves the hole tangentially. It seems > to me that your assertions only make sense when the wheel is laced > radially. > > >> for dave, no, there's nothing sinister about this hub being black or >> large flange. it just happened to be a virgin hub at the top of my >> parts box.   Date: 19 Dec 2006 04:30:54 From: Gary Young Subject: Re: I fixed a broken spoke! On Wed, 06 Dec 2006 21:09:48 -0800, jim beam wrote: > dvt wrote: >> jim beam wrote: >>> dvt wrote: >>>> jim beam wrote: >>>>> but given that the hub flanges are canted and that the angle which >>>>> the spoke manufacturer already provides is already appropriate, >>>>> there's no point in this exercise in the first place. >> >>>> You never answered this question the first time, so let's try again... >> >>> dave, some threads get too long and windy. if you want to /ensure/ i >>> read a question that's somehow important, post a new thread. and make >>> sure i'm not on vacation, traveling, otherwise busy or disinterested. >> >> Nice try, jim. Here's the record: >> >> <http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/1c072f5d8b7c8892/83a78e954c0f932d> > > is this the 'unanswered' question? > "I've been watching this thread, hoping that I wasn't the only one with > this question. How do you "cant and drill" a hole in the hub flange so > that both inbound *and* outbound spokes are "optimized?" If the hole was > so canted, would that mean that the hubs should not be deformed during > the build?" > > if so, i'd have thought the answers obvious. maybe that's why i didn't > bother answering. > >> >> >> Scroll down to messages 103-110. You responded to that exact subthread, >> so I know you were reading it. But you failed to answer the question. >> >>>> In bound vs. out bound, crossing pattern, and rim size all affect the >>>> angle in question. I don't see hubs keted for each variation, and >>>> I don't see holes labeled for inbound and outbound spokes. Do small >>>> wheels (think recumbent) usually use the same hubs as diamond frame >>>> bikes? If so, do they have a much higher incidence of spoke breakage? >> >>> if you want to demonstrate something dave, do the math for the spoke >>> angle given that a hub hole may be larger diameter than the spoke and >>> seated in a flange of given thickness. then compare that to the stock >>> spoke angle of ~95°. I think Dave has a point. Elsewhere you've suggested that spoke manufacturers optimize the elbow angle based on the average configuration (number of spokes, cross pattern, type of hub, etc.) Even if that's true, and if spoke manufacturers really go to the extent you suggest to optimize their spokes, you would expect things to be different on spokes so short that they can only be used on smaller wheels. Does anyone have such a spoke (e.g. a spoke for a bmx hub)? Is the angle different? Are the flanges on bmx hubs canted at a different angle? >> >> You made the claim. It's your job to prove it. Here's the claim you >> made, in case you've forgotten: >> >> "the spoke elbow comes pre-formed with the best resultant angle and the >> hub flange is canted and drilled also to give the best resultant angle." >> >> You made no reservations about wheel size, lacing pattern, or any of the >> other things you tried to add in later when questioned. And what about >> dished wheels? Or rims with offset spoke beds? >> >> I'm looking forward to your response. >> > unless you want a full custom hub, the economics don't support > accommodating non-standard configurations. > > two hub pics for consideration: > http://www.flickr.com/photos/38636024@N00/316202144/ > http://www.flickr.com/photos/38636024@N00/316202143/ > > for the cynics, i didn't happen to have any 2.4mm rod about for the hub > hole pic, but if you don't believe the hub holes are perpendicular to > the flange, do this experiment yourself. Is there anyone here who's denied that flanges are canted? Even with canting, when you build a wheel, you can see that the outbound spokes don't lie as flat against the flange as inbound spokes. If correcting the spoke line were merely a premature way of bedding in the spokes, wouldn't the same bulge be evident on both sides of the flange? While canting may make a gross correction in the spoke line, it seems to me that canting in itself introduces a new difference in the lines of inbound and outbound spokes (at least when using a non-radial, cross-laced pattern). With a canted or funnel-like flange, as in inbound spoke runs tangentially along the flange, it will be closer to the edge of the flange than will an outbound spoke. In other words, it will take a lesser amount of tension to bring the inbound spoke in contact with the canted-in edge as it leaves the hub. Is there some way to compensate for that without drilling the inbound spoke holes in a different way than the outbound ones? Or making separate sets of inbound and outbound spokes? I suppose the beveling of the spoke holes could compensate for that to a certain degree, but it doesn't seem to do so entirely. I just put a spoke in a unlaced LX front hub, first inbound and then outbound. It takes noticeably greater force to bring the outbound spoke in contact with the edge of the flange when the spoke leaves the hole tangentially. It seems to me that your assertions only make sense when the wheel is laced radially. > for dave, no, there's nothing sinister about this hub being black or > large flange. it just happened to be a virgin hub at the top of my > parts box.     Date: 19 Dec 2006 10:13:17 From: Subject: Re: I fixed a broken spoke! On Tue, 19 Dec 2006 04:30:54 -0600, Gary Young <garyyoung3@gmail.com > wrote: [snip] Dear Gary, For what it's worth, Sapim disagrees with the common practice of "correcting the spoke line." Here's their FAQ comment on 95 degree elbow angles and whether spokes should be bent ("forced") to change the angle: "If material is forced while lacing the hub, the spokes can be pulled over causing material weakness." "The original bend angle of 95° should remain intact." http://www.sapim.be/index.php?st=fa Cheers, Carl Fogel   Date: 12 Dec 2006 00:35:36 From: Gary Young Subject: Re: I fixed a broken spoke! On Mon, 11 Dec 2006 20:45:41 -0800, jim beam wrote: > Gary Young wrote: >> On Fri, 08 Dec 2006 21:52:51 -0800, jim beam wrote: >> >>> Johnny Sunset wrote: >>>> jim beam wrote: >>>>> Johnny Sunset wrote: >>>>>> Jobst Brandt wrote: >>>>>>> Tom Sherman writes: >>>>>>> >>>>>>>>> ... I agree and in addition, a spoke elbow that is, perhaps, 85? >>>>>>>>> and needs to be 95? cannot be opened to that angle once in >>>>>>>>> place... >>>>>>>> Work hardening, "fulcrum" in the wrong place, or a combination of >>>>>>>> the two? >>>>>>> No fulcrum about which to change the bend. Try it sometime. That >>>>>>> is why the spoke lone must be improved manually, because tension >>>>>>> alone will not change the shape of the elbow. >>>>>>> >>>>>>> Spokes do not further work harden in use because that would require >>>>>>> substantial form change while yielding. >>>>>> Previous discussions on rec.bicycles.tech have established that most >>>>>> higher quality spokes (e.g. DT, Sapim, and Wheelsmith) are made from >>>>>> 304 stainless steel. >>>>> i think that too much of an assumption. sapim describe their material >>>>> as "18/8", a broad but common designation which can be included in >>>>> 304, but neither d.t. nor wheelsmith say what they use iirc. whatever >>>>> the details, a simple magnet test reveals all 3 brands to be >>>>> different. sapim is strongly magnetic, wheelsmith very weakly and d.t. >>>>> in between. >>>> >From the Wheelsmith website [1]: "All Wheelsmith spokes are produced >>>> from a specially drawn 304 stainless steel using a variety of cold >>>> forging techniques, some proprietary." >>>> >>>>>> It is my understanding that the austenitic (FCC) crystalline >>>>>> structure of 304 is changed to a tensitic crystalline structure >>>>>> that is either HCP or BCC when cold worked, and that (as expected) >>>>>> the tensite is harder and less ductile (i.e. work hardened) than >>>>>> the parent austenite. >>>>> there can indeed be work-induced tensitic transformations, but >>>>> again, i'm not comfortable saying that is definitely the case here. >>>>> 304 is not commonly designated as a tensitic grade. >>>>> http://www.msm.cam.ac.uk/phase-trans/2005/Stainless_steels/stainless.html >>>> This is a claim that austenitic 304 will form tensite when >>>> plastically deformed at cold temperatures [2]. Are you differing on >>>> degree of tensitic transformation or suggesting some other mechanism >>>> for work hardening? >>> ok, 2 things: >>> >>> 1. yes, i would want to be sure of degree of transformation rather than >>> making extreme broad-brush claims. the second paper you cite does >>> indeed discuss transformation at low temperatures [-50 centigrade] which >>> accords with my understanding that transformation at more normal >>> temperatures is much more limited. >>> 2. work hardening occurs regardless of any tensitic transformation. >>> as cited, extent and type of transformation will affect the degree of >>> hardening - obviously, but straight, stable austenitic stainless steels >>> significantly work harden as a function of deformation [increasing >>> dislocation density], as do most simple ductile metals. >>> >>> >>>>>> Is the amount of deformation when installing a new 304 spoke in a >>>>>> wheel insufficient to significantly work harden the elbow? >>>>>> >>>>> unless it exhibits strain aging, /any/ deformation creates work >>>>> hardening. that's why the stress/strain graph *rises* above the yield >>>>> point rather than goes sideways. >>>> I am aware of the strain hardening of 304 steel (having run tension >>>> tests on said material to failure), which is why I used the qualifier >>>> "significantly". Would the degree of work hardening of bending the >>>> elbow of a 304 steel spoke to 85� make it impractical to bend back to >>>> 95�? >>> if it remains austenitic, it's less likely to be an issue, but >>> regardless, it depends on the degree of cold work already performed. if >>> you're dealing with cold drawn wire, the majority of its strength >>> derives from cold work. it it's near its ductile limit [full hard], >>> then yes, additional bending could be a problem, but it's unlikely the >>> wire would be offered in this condition for general manufacture. and >>> "304" is a /real/ wide spec. since wheelsmith seem to regard the simple >>> grinding process they use to butt their spokes as "proprietary", i'd not >>> want to rely too heavily on accuracy of their disclosure of alloy used. >>> >>> >> >> >> According to Wheelsmith, their butted spokes have "center sections [that] >> are forged rather than cut, ground or drawn ...." >> >> http://www.wheelsmith.com/index_files/spoketech.htm > > yeah, i saw that too. the appearance of the spoke does not accord with > that statement though - it appears to have been ground and polished. > and i believe that the japanese factory from which wheelsmith spokes > originated uses this process also, producing both polished and > unpolished ground spokes, depending on price point. the only way to > know for sure is metallography. perhaps chas can oblige? > What is it about the appearance that leads you to say that? Is it the abruptness of the transition from the center section to the elbow and threads? Or something about the surface finish? >> >> >> >>>> [1] <http://www.wheelsmith.com/index_files/wsspokes.htm>. [2] >>>> <http://doc.tms.org/ezMerchant/prodtms.nsf/ProductLookupItemID/MMTA-0606-1875/$FILE/MMTA-0606-1875F.pdf?OpenElement>. >>>> >>>> >>> that second paper is a good cite.     Date: 12 Dec 2006 18:55:48 From: jim beam Subject: Re: I fixed a broken spoke! Gary Young wrote: > On Mon, 11 Dec 2006 20:45:41 -0800, jim beam wrote: > >> Gary Young wrote: >>> On Fri, 08 Dec 2006 21:52:51 -0800, jim beam wrote: >>> >>>> Johnny Sunset wrote: >>>>> jim beam wrote: >>>>>> Johnny Sunset wrote: >>>>>>> Jobst Brandt wrote: >>>>>>>> Tom Sherman writes: >>>>>>>> >>>>>>>>>> ... I agree and in addition, a spoke elbow that is, perhaps, 85? >>>>>>>>>> and needs to be 95? cannot be opened to that angle once in >>>>>>>>>> place... >>>>>>>>> Work hardening, "fulcrum" in the wrong place, or a combination of >>>>>>>>> the two? >>>>>>>> No fulcrum about which to change the bend. Try it sometime. That >>>>>>>> is why the spoke lone must be improved manually, because tension >>>>>>>> alone will not change the shape of the elbow. >>>>>>>> >>>>>>>> Spokes do not further work harden in use because that would require >>>>>>>> substantial form change while yielding. >>>>>>> Previous discussions on rec.bicycles.tech have established that most >>>>>>> higher quality spokes (e.g. DT, Sapim, and Wheelsmith) are made from >>>>>>> 304 stainless steel. >>>>>> i think that too much of an assumption. sapim describe their material >>>>>> as "18/8", a broad but common designation which can be included in >>>>>> 304, but neither d.t. nor wheelsmith say what they use iirc. whatever >>>>>> the details, a simple magnet test reveals all 3 brands to be >>>>>> different. sapim is strongly magnetic, wheelsmith very weakly and d.t. >>>>>> in between. >>>>> >From the Wheelsmith website [1]: "All Wheelsmith spokes are produced >>>>> from a specially drawn 304 stainless steel using a variety of cold >>>>> forging techniques, some proprietary." >>>>> >>>>>>> It is my understanding that the austenitic (FCC) crystalline >>>>>>> structure of 304 is changed to a tensitic crystalline structure >>>>>>> that is either HCP or BCC when cold worked, and that (as expected) >>>>>>> the tensite is harder and less ductile (i.e. work hardened) than >>>>>>> the parent austenite. >>>>>> there can indeed be work-induced tensitic transformations, but >>>>>> again, i'm not comfortable saying that is definitely the case here. >>>>>> 304 is not commonly designated as a tensitic grade. >>>>>> http://www.msm.cam.ac.uk/phase-trans/2005/Stainless_steels/stainless.html >>>>> This is a claim that austenitic 304 will form tensite when >>>>> plastically deformed at cold temperatures [2]. Are you differing on >>>>> degree of tensitic transformation or suggesting some other mechanism >>>>> for work hardening? >>>> ok, 2 things: >>>> >>>> 1. yes, i would want to be sure of degree of transformation rather than >>>> making extreme broad-brush claims. the second paper you cite does >>>> indeed discuss transformation at low temperatures [-50 centigrade] which >>>> accords with my understanding that transformation at more normal >>>> temperatures is much more limited. >>>> 2. work hardening occurs regardless of any tensitic transformation. >>>> as cited, extent and type of transformation will affect the degree of >>>> hardening - obviously, but straight, stable austenitic stainless steels >>>> significantly work harden as a function of deformation [increasing >>>> dislocation density], as do most simple ductile metals. >>>> >>>> >>>>>>> Is the amount of deformation when installing a new 304 spoke in a >>>>>>> wheel insufficient to significantly work harden the elbow? >>>>>>> >>>>>> unless it exhibits strain aging, /any/ deformation creates work >>>>>> hardening. that's why the stress/strain graph *rises* above the yield >>>>>> point rather than goes sideways. >>>>> I am aware of the strain hardening of 304 steel (having run tension >>>>> tests on said material to failure), which is why I used the qualifier >>>>> "significantly". Would the degree of work hardening of bending the >>>>> elbow of a 304 steel spoke to 85� make it impractical to bend back to >>>>> 95�? >>>> if it remains austenitic, it's less likely to be an issue, but >>>> regardless, it depends on the degree of cold work already performed. if >>>> you're dealing with cold drawn wire, the majority of its strength >>>> derives from cold work. it it's near its ductile limit [full hard], >>>> then yes, additional bending could be a problem, but it's unlikely the >>>> wire would be offered in this condition for general manufacture. and >>>> "304" is a /real/ wide spec. since wheelsmith seem to regard the simple >>>> grinding process they use to butt their spokes as "proprietary", i'd not >>>> want to rely too heavily on accuracy of their disclosure of alloy used. >>>> >>>> >>> >>> According to Wheelsmith, their butted spokes have "center sections [that] >>> are forged rather than cut, ground or drawn ...." >>> >>> http://www.wheelsmith.com/index_files/spoketech.htm >> yeah, i saw that too. the appearance of the spoke does not accord with >> that statement though - it appears to have been ground and polished. >> and i believe that the japanese factory from which wheelsmith spokes >> originated uses this process also, producing both polished and >> unpolished ground spokes, depending on price point. the only way to >> know for sure is metallography. perhaps chas can oblige? >> > > What is it about the appearance that leads you to say that? Is it the > abruptness of the transition from the center section to the elbow and > threads? Or something about the surface finish? both, if you mean the transition on the butting. there, the section transition is very smooth and shows no signs of mechanical work. that implies post-process polishing. with a forging or drawing process, the surface finish is usually good enough to not warrant further [cost increasing] work - see d.t., alpina and sapim for examples. regarding the section profile, not only is it /not/ like any drawing or cold forging process seen with any other manufacturer, it /is/ identical to the profile of the japanese ground section spokes i have. mine are unpolished, so i know for sure how they were made without having to do metallography. > >>> >>> >>>>> [1] <http://www.wheelsmith.com/index_files/wsspokes.htm>. [2] >>>>> <http://doc.tms.org/ezMerchant/prodtms.nsf/ProductLookupItemID/MMTA-0606-1875/$FILE/MMTA-0606-1875F.pdf?OpenElement>. >>>>> >>>>> >>>> that second paper is a good cite.   Date: 11 Dec 2006 11:45:31 From: Gary Young Subject: Re: I fixed a broken spoke! On Fri, 08 Dec 2006 21:52:51 -0800, jim beam wrote: > Johnny Sunset wrote: >> jim beam wrote: >>> Johnny Sunset wrote: >>>> Jobst Brandt wrote: >>>>> Tom Sherman writes: >>>>> >>>>>>> ... I agree and in addition, a spoke elbow that is, perhaps, 85? >>>>>>> and needs to be 95? cannot be opened to that angle once in >>>>>>> place... >>>>>> Work hardening, "fulcrum" in the wrong place, or a combination of >>>>>> the two? >>>>> No fulcrum about which to change the bend. Try it sometime. That >>>>> is why the spoke lone must be improved manually, because tension >>>>> alone will not change the shape of the elbow. >>>>> >>>>> Spokes do not further work harden in use because that would require >>>>> substantial form change while yielding. >>>> Previous discussions on rec.bicycles.tech have established that most >>>> higher quality spokes (e.g. DT, Sapim, and Wheelsmith) are made from >>>> 304 stainless steel. >>> i think that too much of an assumption. sapim describe their material >>> as "18/8", a broad but common designation which can be included in >>> 304, but neither d.t. nor wheelsmith say what they use iirc. whatever >>> the details, a simple magnet test reveals all 3 brands to be >>> different. sapim is strongly magnetic, wheelsmith very weakly and d.t. >>> in between. >> >>>From the Wheelsmith website [1]: "All Wheelsmith spokes are produced >> from a specially drawn 304 stainless steel using a variety of cold >> forging techniques, some proprietary." >> >>>> It is my understanding that the austenitic (FCC) crystalline >>>> structure of 304 is changed to a tensitic crystalline structure >>>> that is either HCP or BCC when cold worked, and that (as expected) >>>> the tensite is harder and less ductile (i.e. work hardened) than >>>> the parent austenite. >>> there can indeed be work-induced tensitic transformations, but >>> again, i'm not comfortable saying that is definitely the case here. >>> 304 is not commonly designated as a tensitic grade. >>> http://www.msm.cam.ac.uk/phase-trans/2005/Stainless_steels/stainless.html >> >> This is a claim that austenitic 304 will form tensite when >> plastically deformed at cold temperatures [2]. Are you differing on >> degree of tensitic transformation or suggesting some other mechanism >> for work hardening? > > ok, 2 things: > > 1. yes, i would want to be sure of degree of transformation rather than > making extreme broad-brush claims. the second paper you cite does > indeed discuss transformation at low temperatures [-50 centigrade] which > accords with my understanding that transformation at more normal > temperatures is much more limited. > 2. work hardening occurs regardless of any tensitic transformation. > as cited, extent and type of transformation will affect the degree of > hardening - obviously, but straight, stable austenitic stainless steels > significantly work harden as a function of deformation [increasing > dislocation density], as do most simple ductile metals. > > >>>> Is the amount of deformation when installing a new 304 spoke in a >>>> wheel insufficient to significantly work harden the elbow? >>>> >>> unless it exhibits strain aging, /any/ deformation creates work >>> hardening. that's why the stress/strain graph *rises* above the yield >>> point rather than goes sideways. >> >> I am aware of the strain hardening of 304 steel (having run tension >> tests on said material to failure), which is why I used the qualifier >> "significantly". Would the degree of work hardening of bending the >> elbow of a 304 steel spoke to 85� make it impractical to bend back to >> 95�? > > if it remains austenitic, it's less likely to be an issue, but > regardless, it depends on the degree of cold work already performed. if > you're dealing with cold drawn wire, the majority of its strength > derives from cold work. it it's near its ductile limit [full hard], > then yes, additional bending could be a problem, but it's unlikely the > wire would be offered in this condition for general manufacture. and > "304" is a /real/ wide spec. since wheelsmith seem to regard the simple > grinding process they use to butt their spokes as "proprietary", i'd not > want to rely too heavily on accuracy of their disclosure of alloy used. > > According to Wheelsmith, their butted spokes have "center sections [that] are forged rather than cut, ground or drawn ...." http://www.wheelsmith.com/index_files/spoketech.htm >> [1] <http://www.wheelsmith.com/index_files/wsspokes.htm>. [2] >> <http://doc.tms.org/ezMerchant/prodtms.nsf/ProductLookupItemID/MMTA-0606-1875/$FILE/MMTA-0606-1875F.pdf?OpenElement>. >> >> > that second paper is a good cite.     Date: 11 Dec 2006 20:45:41 From: jim beam Subject: Re: I fixed a broken spoke! Gary Young wrote: > On Fri, 08 Dec 2006 21:52:51 -0800, jim beam wrote: > >> Johnny Sunset wrote: >>> jim beam wrote: >>>> Johnny Sunset wrote: >>>>> Jobst Brandt wrote: >>>>>> Tom Sherman writes: >>>>>> >>>>>>>> ... I agree and in addition, a spoke elbow that is, perhaps, 85? >>>>>>>> and needs to be 95? cannot be opened to that angle once in >>>>>>>> place... >>>>>>> Work hardening, "fulcrum" in the wrong place, or a combination of >>>>>>> the two? >>>>>> No fulcrum about which to change the bend. Try it sometime. That >>>>>> is why the spoke lone must be improved manually, because tension >>>>>> alone will not change the shape of the elbow. >>>>>> >>>>>> Spokes do not further work harden in use because that would require >>>>>> substantial form change while yielding. >>>>> Previous discussions on rec.bicycles.tech have established that most >>>>> higher quality spokes (e.g. DT, Sapim, and Wheelsmith) are made from >>>>> 304 stainless steel. >>>> i think that too much of an assumption. sapim describe their material >>>> as "18/8", a broad but common designation which can be included in >>>> 304, but neither d.t. nor wheelsmith say what they use iirc. whatever >>>> the details, a simple magnet test reveals all 3 brands to be >>>> different. sapim is strongly magnetic, wheelsmith very weakly and d.t. >>>> in between. >>> >From the Wheelsmith website [1]: "All Wheelsmith spokes are produced >>> from a specially drawn 304 stainless steel using a variety of cold >>> forging techniques, some proprietary." >>> >>>>> It is my understanding that the austenitic (FCC) crystalline >>>>> structure of 304 is changed to a tensitic crystalline structure >>>>> that is either HCP or BCC when cold worked, and that (as expected) >>>>> the tensite is harder and less ductile (i.e. work hardened) than >>>>> the parent austenite. >>>> there can indeed be work-induced tensitic transformations, but >>>> again, i'm not comfortable saying that is definitely the case here. >>>> 304 is not commonly designated as a tensitic grade. >>>> http://www.msm.cam.ac.uk/phase-trans/2005/Stainless_steels/stainless.html >>> This is a claim that austenitic 304 will form tensite when >>> plastically deformed at cold temperatures [2]. Are you differing on >>> degree of tensitic transformation or suggesting some other mechanism >>> for work hardening? >> ok, 2 things: >> >> 1. yes, i would want to be sure of degree of transformation rather than >> making extreme broad-brush claims. the second paper you cite does >> indeed discuss transformation at low temperatures [-50 centigrade] which >> accords with my understanding that transformation at more normal >> temperatures is much more limited. >> 2. work hardening occurs regardless of any tensitic transformation. >> as cited, extent and type of transformation will affect the degree of >> hardening - obviously, but straight, stable austenitic stainless steels >> significantly work harden as a function of deformation [increasing >> dislocation density], as do most simple ductile metals. >> >> >>>>> Is the amount of deformation when installing a new 304 spoke in a >>>>> wheel insufficient to significantly work harden the elbow? >>>>> >>>> unless it exhibits strain aging, /any/ deformation creates work >>>> hardening. that's why the stress/strain graph *rises* above the yield >>>> point rather than goes sideways. >>> I am aware of the strain hardening of 304 steel (having run tension >>> tests on said material to failure), which is why I used the qualifier >>> "significantly". Would the degree of work hardening of bending the >>> elbow of a 304 steel spoke to 85� make it impractical to bend back to >>> 95�? >> if it remains austenitic, it's less likely to be an issue, but >> regardless, it depends on the degree of cold work already performed. if >> you're dealing with cold drawn wire, the majority of its strength >> derives from cold work. it it's near its ductile limit [full hard], >> then yes, additional bending could be a problem, but it's unlikely the >> wire would be offered in this condition for general manufacture. and >> "304" is a /real/ wide spec. since wheelsmith seem to regard the simple >> grinding process they use to butt their spokes as "proprietary", i'd not >> want to rely too heavily on accuracy of their disclosure of alloy used. >> >> > > > According to Wheelsmith, their butted spokes have "center sections [that] > are forged rather than cut, ground or drawn ...." > > http://www.wheelsmith.com/index_files/spoketech.htm yeah, i saw that too. the appearance of the spoke does not accord with that statement though - it appears to have been ground and polished. and i believe that the japanese factory from which wheelsmith spokes originated uses this process also, producing both polished and unpolished ground spokes, depending on price point. the only way to know for sure is metallography. perhaps chas can oblige? > > > >>> [1] <http://www.wheelsmith.com/index_files/wsspokes.htm>. [2] >>> <http://doc.tms.org/ezMerchant/prodtms.nsf/ProductLookupItemID/MMTA-0606-1875/$FILE/MMTA-0606-1875F.pdf?OpenElement>. >>> >>> >> that second paper is a good cite.   Date: 08 Dec 2006 17:17:48 From: Johnny Sunset Subject: Re: I fixed a broken spoke! jim beam wrote: > Johnny Sunset wrote: > > Jobst Brandt wrote: > >> Tom Sherman writes: > >> > >>>> ... I agree and in addition, a spoke elbow that is, perhaps, 85? > >>>> and needs to be 95? cannot be opened to that angle once in > >>>> place... > >>> Work hardening, "fulcrum" in the wrong place, or a combination of > >>> the two? > >> No fulcrum about which to change the bend. Try it sometime. That is > >> why the spoke lone must be improved manually, because tension alone > >> will not change the shape of the elbow. > >> > >> Spokes do not further work harden in use because that would require > >> substantial form change while yielding. > > > > Previous discussions on rec.bicycles.tech have established that most > > higher quality spokes (e.g. DT, Sapim, and Wheelsmith) are made from > > 304 stainless steel. > > i think that too much of an assumption. sapim describe their material > as "18/8", a broad but common designation which can be included in 304, > but neither d.t. nor wheelsmith say what they use iirc. whatever the > details, a simple magnet test reveals all 3 brands to be different. > sapim is strongly magnetic, wheelsmith very weakly and d.t. in between. >From the Wheelsmith website [1]: "All Wheelsmith spokes are produced from a specially drawn 304 stainless steel using a variety of cold forging techniques, some proprietary." > > It is my understanding that the austenitic (FCC) crystalline structure > > of 304 is changed to a tensitic crystalline structure that is either > > HCP or BCC when cold worked, and that (as expected) the tensite is > > harder and less ductile (i.e. work hardened) than the parent austenite. > > there can indeed be work-induced tensitic transformations, but again, > i'm not comfortable saying that is definitely the case here. 304 is not > commonly designated as a tensitic grade. > http://www.msm.cam.ac.uk/phase-trans/2005/Stainless_steels/stainless.html This is a claim that austenitic 304 will form tensite when plastically deformed at cold temperatures [2]. Are you differing on degree of tensitic transformation or suggesting some other mechanism for work hardening? > > Is the amount of deformation when installing a new 304 spoke in a wheel > > insufficient to significantly work harden the elbow? > > > > unless it exhibits strain aging, /any/ deformation creates work > hardening. that's why the stress/strain graph *rises* above the yield > point rather than goes sideways. I am aware of the strain hardening of 304 steel (having run tension tests on said material to failure), which is why I used the qualifier "significantly". Would the degree of work hardening of bending the elbow of a 304 steel spoke to 85=B0 make it impractical to bend back to 95=B0? [1] <http://www.wheelsmith.com/index_files/wsspokes.htm >. [2] <http://doc.tms.org/ezMerchant/prodtms.nsf/ProductLookupItemID/MMTA-0606-18= 75/$FILE/MMTA-0606-1875F.pdf?OpenElement >. --=20 Tom Sherman - Post Free or Die!     Date: 08 Dec 2006 21:52:51 From: jim beam Subject: Re: I fixed a broken spoke! Johnny Sunset wrote: > jim beam wrote: >> Johnny Sunset wrote: >>> Jobst Brandt wrote: >>>> Tom Sherman writes: >>>> >>>>>> ... I agree and in addition, a spoke elbow that is, perhaps, 85? >>>>>> and needs to be 95? cannot be opened to that angle once in >>>>>> place... >>>>> Work hardening, "fulcrum" in the wrong place, or a combination of >>>>> the two? >>>> No fulcrum about which to change the bend. Try it sometime. That is >>>> why the spoke lone must be improved manually, because tension alone >>>> will not change the shape of the elbow. >>>> >>>> Spokes do not further work harden in use because that would require >>>> substantial form change while yielding. >>> Previous discussions on rec.bicycles.tech have established that most >>> higher quality spokes (e.g. DT, Sapim, and Wheelsmith) are made from >>> 304 stainless steel. >> i think that too much of an assumption. sapim describe their material >> as "18/8", a broad but common designation which can be included in 304, >> but neither d.t. nor wheelsmith say what they use iirc. whatever the >> details, a simple magnet test reveals all 3 brands to be different. >> sapim is strongly magnetic, wheelsmith very weakly and d.t. in between. > >>From the Wheelsmith website [1]: "All Wheelsmith spokes are produced > from a specially drawn 304 stainless steel using a variety of cold > forging techniques, some proprietary." > >>> It is my understanding that the austenitic (FCC) crystalline structure >>> of 304 is changed to a tensitic crystalline structure that is either >>> HCP or BCC when cold worked, and that (as expected) the tensite is >>> harder and less ductile (i.e. work hardened) than the parent austenite. >> there can indeed be work-induced tensitic transformations, but again, >> i'm not comfortable saying that is definitely the case here. 304 is not >> commonly designated as a tensitic grade. >> http://www.msm.cam.ac.uk/phase-trans/2005/Stainless_steels/stainless.html > > This is a claim that austenitic 304 will form tensite when > plastically deformed at cold temperatures [2]. Are you differing on > degree of tensitic transformation or suggesting some other mechanism > for work hardening? ok, 2 things: 1. yes, i would want to be sure of degree of transformation rather than making extreme broad-brush claims. the second paper you cite does indeed discuss transformation at low temperatures [-50 centigrade] which accords with my understanding that transformation at more normal temperatures is much more limited. 2. work hardening occurs regardless of any tensitic transformation. as cited, extent and type of transformation will affect the degree of hardening - obviously, but straight, stable austenitic stainless steels significantly work harden as a function of deformation [increasing dislocation density], as do most simple ductile metals. > >>> Is the amount of deformation when installing a new 304 spoke in a wheel >>> insufficient to significantly work harden the elbow? >>> >> unless it exhibits strain aging, /any/ deformation creates work >> hardening. that's why the stress/strain graph *rises* above the yield >> point rather than goes sideways. > > I am aware of the strain hardening of 304 steel (having run tension > tests on said material to failure), which is why I used the qualifier > "significantly". Would the degree of work hardening of bending the > elbow of a 304 steel spoke to 85� make it impractical to bend back to > 95�? if it remains austenitic, it's less likely to be an issue, but regardless, it depends on the degree of cold work already performed. if you're dealing with cold drawn wire, the majority of its strength derives from cold work. it it's near its ductile limit [full hard], then yes, additional bending could be a problem, but it's unlikely the wire would be offered in this condition for general manufacture. and "304" is a /real/ wide spec. since wheelsmith seem to regard the simple grinding process they use to butt their spokes as "proprietary", i'd not want to rely too heavily on accuracy of their disclosure of alloy used. > > [1] <http://www.wheelsmith.com/index_files/wsspokes.htm>. > [2] > <http://doc.tms.org/ezMerchant/prodtms.nsf/ProductLookupItemID/MMTA-0606-1875/$FILE/MMTA-0606-1875F.pdf?OpenElement>. > that second paper is a good cite.   Date: 08 Dec 2006 05:14:22 From: Johnny Sunset Subject: Re: I fixed a broken spoke! Jobst Brandt wrote: > Tom Sherman writes: > > >> ... I agree and in addition, a spoke elbow that is, perhaps, 85=B0 > >> and needs to be 95=B0 cannot be opened to that angle once in > >> place... > > > Work hardening, "fulcrum" in the wrong place, or a combination of > > the two? > > No fulcrum about which to change the bend. Try it sometime. That is > why the spoke lone must be improved manually, because tension alone > will not change the shape of the elbow. > > Spokes do not further work harden in use because that would require > substantial form change while yielding. Previous discussions on rec.bicycles.tech have established that most higher quality spokes (e.g. DT, Sapim, and Wheelsmith) are made from 304 stainless steel. It is my understanding that the austenitic (FCC) crystalline structure of 304 is changed to a tensitic crystalline structure that is either HCP or BCC when cold worked, and that (as expected) the tensite is harder and less ductile (i.e. work hardened) than the parent austenite. Is the amount of deformation when installing a new 304 spoke in a wheel insufficient to significantly work harden the elbow? --=20 Tom Sherman - Post Free or Die!     Date: 08 Dec 2006 07:46:17 From: jim beam Subject: Re: I fixed a broken spoke! Johnny Sunset wrote: > Jobst Brandt wrote: >> Tom Sherman writes: >> >>>> ... I agree and in addition, a spoke elbow that is, perhaps, 85� >>>> and needs to be 95� cannot be opened to that angle once in >>>> place... >>> Work hardening, "fulcrum" in the wrong place, or a combination of >>> the two? >> No fulcrum about which to change the bend. Try it sometime. That is >> why the spoke lone must be improved manually, because tension alone >> will not change the shape of the elbow. >> >> Spokes do not further work harden in use because that would require >> substantial form change while yielding. > > Previous discussions on rec.bicycles.tech have established that most > higher quality spokes (e.g. DT, Sapim, and Wheelsmith) are made from > 304 stainless steel. i think that too much of an assumption. sapim describe their material as "18/8", a broad but common designation which can be included in 304, but neither d.t. nor wheelsmith say what they use iirc. whatever the details, a simple magnet test reveals all 3 brands to be different. sapim is strongly magnetic, wheelsmith very weakly and d.t. in between. > > It is my understanding that the austenitic (FCC) crystalline structure > of 304 is changed to a tensitic crystalline structure that is either > HCP or BCC when cold worked, and that (as expected) the tensite is > harder and less ductile (i.e. work hardened) than the parent austenite. there can indeed be work-induced tensitic transformations, but again, i'm not comfortable saying that is definitely the case here. 304 is not commonly designated as a tensitic grade. http://www.msm.cam.ac.uk/phase-trans/2005/Stainless_steels/stainless.html > > Is the amount of deformation when installing a new 304 spoke in a wheel > insufficient to significantly work harden the elbow? > unless it exhibits strain aging, /any/ deformation creates work hardening. that's why the stress/strain graph *rises* above the yield point rather than goes sideways.   Date: 07 Dec 2006 20:03:19 From: Johnny Sunset aka Tom Sherman Subject: Re: I fixed a broken spoke! Jobst Brandt wrote: > ... > I agree and in addition, a spoke elbow that is, perhaps, 85=B0 and needs > to be 95=B0 cannot be opened to that angle once in place.... Work hardening, "fulcrum" in the wrong place, or a combination of the two? --=20 Tom Sherman - Post Free or Die!     Date: 08 Dec 2006 04:55:05 From: Subject: Re: I fixed a broken spoke! Tom Sherman writes: >> ... I agree and in addition, a spoke elbow that is, perhaps, 85=C2=B0 >> and needs to be 95=C2=B0 cannot be opened to that angle once in >> place... > Work hardening, "fulcrum" in the wrong place, or a combination of > the two? No fulcrum about which to change the bend. Try it sometime. That is why the spoke lone must be improved manually, because tension alone will not change the shape of the elbow. Spokes do not further work harden in use because that would require substantial form change while yielding. Jobst       Date: 08 Dec 2006 09:52:21 From: Pat Lamb Subject: Re: I fixed a broken spoke! jobst.brandt@stanfordalumni.org wrote: > Tom Sherman writes: > >>> ... I agree and in addition, a spoke elbow that is, perhaps, 85° >>> and needs to be 95° cannot be opened to that angle once in >>> place... > >> Work hardening, "fulcrum" in the wrong place, or a combination of >> the two? > > No fulcrum about which to change the bend. Try it sometime. That is > why the spoke lone must be improved manually, because tension alone > will not change the shape of the elbow. I'm not sure I understand this. Couldn't you slide a big flat-head screwdriver between the spoke and the flange and bend it back out? Pat         Date: 08 Dec 2006 17:16:11 From: Subject: Re: I fixed a broken spoke! Pat Lamb writes: >>>> ... I agree and in addition, a spoke elbow that is, perhaps, 85=C2=B0 >>>> and needs to be 95=C2=B0 cannot be opened to that angle once in >>>> place... >>> Work hardening, "fulcrum" in the wrong place, or a combination of >>> the two? >> No fulcrum about which to change the bend. Try it sometime. That >> is why the spoke line must be improved manually, because tension >> alone will not change the shape of the elbow. > I'm not sure I understand this. Couldn't you slide a big flat-head > screwdriver between the spoke and the flange and bend it back out? That doesn't work because the elbow would only rock in its aluminum bore and change little if any. Besides, there is no gap to insert a screwdriver. Something thin enough to enter there would be too weak to bend a spoke. Jobst Brandt       Date: 07 Dec 2006 21:12:34 From: jim beam Subject: Re: I fixed a broken spoke! jobst.brandt@stanfordalumni.org wrote: > Tom Sherman writes: > >>> ... I agree and in addition, a spoke elbow that is, perhaps, 85° >>> and needs to be 95° cannot be opened to that angle once in >>> place... > >> Work hardening, "fulcrum" in the wrong place, or a combination of >> the two? > > No fulcrum about which to change the bend. Try it sometime. if there's no fulcrum, what is this "flange" thing about which spokes are being bent to "correct the spoke line"? > That is > why the spoke lone must be improved manually, because tension alone > will not change the shape of the elbow. is that not because of hub hole conformance to the spoke??? > > Spokes do not further work harden in use because that would require > substantial form change while yielding. but it's not "substantial". since stainless spoke steels do not strain age, as demonstrated by the testing in your own book, they most definitely /do/ work harden from from the slightest deformation while the spoke line is being "corrected".         Date: 12 Dec 2006 01:24:36 From: Jasper Janssen Subject: Re: I fixed a broken spoke! On Thu, 07 Dec 2006 21:12:34 -0800, jim beam <spamvortex@bad.example.net > wrote: >jobst.brandt@stanfordalumni.org wrote: >> No fulcrum about which to change the bend. Try it sometime. > >if there's no fulcrum, what is this "flange" thing about which spokes >are being bent to "correct the spoke line"? There's a fulcrum for bending it further, but not back, or at least not without getting the nipple end *way* out of the wheel plane, ie, loosened. And even then it's damn hard, because the geometry means that the force you apply tends to rotate the spoke head instead of bending it, whereas with bending further the head tends to lock in place. This is incredibly obvious if you actually try it. Jasper           Date: 11 Dec 2006 20:48:35 From: jim beam Subject: Re: I fixed a broken spoke! Jasper Janssen wrote: > On Thu, 07 Dec 2006 21:12:34 -0800, jim beam <spamvortex@bad.example.net> > wrote: >> jobst.brandt@stanfordalumni.org wrote: > >>> No fulcrum about which to change the bend. Try it sometime. >> if there's no fulcrum, what is this "flange" thing about which spokes >> are being bent to "correct the spoke line"? > > There's a fulcrum for bending it further, but not back, or at least not > without getting the nipple end *way* out of the wheel plane, ie, loosened. that makes no sense. if the spoke's loose, it's loose and can be bent. against the hole in the flange in which it's inserted. which acts as a fulcrum. > And even then it's damn hard, because the geometry means that the force > you apply tends to rotate the spoke head instead of bending it, whereas > with bending further the head tends to lock in place. > > This is incredibly obvious if you actually try it. i think you're confused.       Date: 07 Dec 2006 22:02:28 From: Subject: Re: I fixed a broken spoke! On 08 Dec 2006 04:55:05 GMT, jobst.brandt@stanfordalumni.org wrote: >Tom Sherman writes: > >>> ... I agree and in addition, a spoke elbow that is, perhaps, 85° >>> and needs to be 95° cannot be opened to that angle once in >>> place... > >> Work hardening, "fulcrum" in the wrong place, or a combination of >> the two? > >No fulcrum about which to change the bend. Try it sometime. That is >why the spoke lone must be improved manually, because tension alone >will not change the shape of the elbow. > >Spokes do not further work harden in use because that would require >substantial form change while yielding. > >Jobst Dear Jobst, "The spoke lone" puzzled me for a moment, so others may wonder, too, but the explanation is right next to the "o" on the keyboard. "That is why the spoke line must be improved manually . . ." It would be nice if someone else would take pity on my moment of bafflement and confess to drawing a blank, even if only for an instant. Cheers, Carl Fogel         Date: 08 Dec 2006 06:28:29 From: Michael Press Subject: Re: I fixed a broken spoke! In article <i3shn21utlg92qanrk90st4dd2gcjc1v7t@4ax.com >, carlfogel@comcast.net wrote: > "That is why the spoke line must be improved manually . . ." > > It would be nice if someone else would take pity on my moment of > bafflement and confess to drawing a blank, even if only for an > instant. More than an instant. Almost all Jobst's typographical errors are a real word. Spell checkers are not what they used to be. Used to bring me coffee and sit in my lap. -- Michael Press   Date: 07 Dec 2006 09:01:20 From: Sheldon Brown Subject: Re: I fixed a broken spoke! Peter Cole wrote: > I can't see what's so controversial about carefully taking the bow out > of a tensioned wheel if one exists. I don't see it as controversial, but is much _easier_ to do it on an un-tensioned wheel. When you try to bend any piece of metal to a particular shape, you must bend it past the desired position, allowing the elasticity of the metal to bring it back to the desired shape once the force is removed. Since you need to bend the spoke temporarily beyond "straight" you will be fighting the spoke tension if you try to do this on a fully tensioned wheel. Maybe your thumbs are strong enough for this, but mine aren't. Also, when the spoke are un-tensioned, it is easier to see when the alignment has been optimized. Sheldon "Sequence" Brown +---------------------------------------------------+     Date: 07 Dec 2006 20:10:27 From: jim beam Subject: Re: I fixed a broken spoke! Sheldon Brown wrote: > Peter Cole wrote: > >> I can't see what's so controversial about carefully taking the bow out >> of a tensioned wheel if one exists. > > I don't see it as controversial, but is much _easier_ to do it on an > un-tensioned wheel. but doing it when the hub hole is not yet conformed to the spoke means that it's being bent too much. > > When you try to bend any piece of metal to a particular shape, you must > bend it past the desired position, allowing the elasticity of the metal > to bring it back to the desired shape once the force is removed. > > Since you need to bend the spoke temporarily beyond "straight" you will > be fighting the spoke tension if you try to do this on a fully > tensioned wheel. Maybe your thumbs are strong enough for this, but > mine aren't. > > Also, when the spoke are un-tensioned, it is easier to see when the > alignment has been optimized. > > Sheldon "Sequence" Brown > +---------------------------------------------------+ >       Date: 12 Dec 2006 01:28:14 From: Jasper Janssen Subject: Re: I fixed a broken spoke! On Thu, 07 Dec 2006 20:10:27 -0800, jim beam <spamvortex@bad.example.net > wrote: >Sheldon Brown wrote: >> Peter Cole wrote: >> >>> I can't see what's so controversial about carefully taking the bow out >>> of a tensioned wheel if one exists. >> >> I don't see it as controversial, but is much _easier_ to do it on an >> un-tensioned wheel. > >but doing it when the hub hole is not yet conformed to the spoke means >that it's being bent too much. Does it matter if the hub flange is alu (and what kind) or chromed steel as in classic and (still) ultracheap hubs? Jasper         Date: 11 Dec 2006 20:48:02 From: jim beam Subject: Re: I fixed a broken spoke! Jasper Janssen wrote: > On Thu, 07 Dec 2006 20:10:27 -0800, jim beam <spamvortex@bad.example.net> > wrote: > >> Sheldon Brown wrote: >>> Peter Cole wrote: >>> >>>> I can't see what's so controversial about carefully taking the bow out >>>> of a tensioned wheel if one exists. >>> I don't see it as controversial, but is much _easier_ to do it on an >>> un-tensioned wheel. >> but doing it when the hub hole is not yet conformed to the spoke means >> that it's being bent too much. > > Does it matter if the hub flange is alu (and what kind) or chromed steel > as in classic and (still) ultracheap hubs? > > Jasper steel hubs still conform, just not as much. spoke wire is much harder than the steel in hub flange material.   Date: 06 Dec 2006 04:38:20 From: Johnny Sunset Subject: Re: I fixed a broken spoke! jtaylor@NOSPAM.hfx.andara.com wrote: > On Tue, 05 Dec 2006 20:23:10 -0800, jim beam > <spamvortex@bad.example.net> wrote: > > > >> In bound vs. out bound, crossing pattern, and rim size all > >> affect the angle in question. I don't see hubs keted for each > >> variation, and I don't see holes labeled for inbound and outbound > >> spokes. Do small wheels (think recumbent) usually use the same hubs as > >> diamond frame bikes? If so, do they have a much higher incidence of > >> spoke breakage? > >> > > > >if you want to demonstrate something dave, do the math for the spoke > >angle given that a hub hole may be larger diameter than the spoke and > >seated in a flange of given thickness. then compare that to the stock > >spoke angle of ~95=B0. > > > I think I saw those calculations a while ago - it was in a book called > "The Bicycle Wheel", I think. LOL ;-) --=20 Tom Sherman - Post Free or Die!   Date: 05 Dec 2006 16:22:12 From: Johnny Sunset Subject: Re: I fixed a broken spoke! dvt wrote: > jim beam wrote: > > but given that the hub flanges are canted and that the > > angle which the spoke manufacturer already provides is already > > appropriate, there's no point in this exercise in the first place. > > You never answered this question the first time, so let's try again... > How are the hub flanges canted optimally for all the variations of > wheels? In bound vs. out bound, crossing pattern, and rim size all > affect the angle in question. I don't see hubs keted for each > variation, and I don't see holes labeled for inbound and outbound > spokes. Do small wheels (think recumbent) usually use the same hubs as > diamond frame bikes? 99+% of recumbents use the same hubs [1], if for no other reason than cost and availability. > If so, do they have a much higher incidence of spoke breakage? No. Typically, smaller wheels are laced 2X or even 1X to avoid large angles at the rim. In addition, 32 and 36 spoke wheels are common, which means more spokes per unit length of rim than larger wheels. And whatever lateral forces the wheels do see are smaller due to shorter moment arm from contact patch to hub. [1] I happen to have several recumbents that use OEM custom Phil Wood hubs, but those are the exception to the rule. -- Tom Sherman - Post Free or Die!   Date: 05 Dec 2006 13:24:35 From: Subject: Re: I fixed a broken spoke! dgk wrote: > On 5 Dec 2006 11:12:43 -0800, joseph.santaniello@gmail.com wrote: > > > > >dgk wrote: > >> On 5 Dec 2006 08:09:21 -0800, joseph.santaniello@gmail.com wrote: > >> > > >> > >> Good. I just posted about a Shimano wheel that I'm thinking about > >> getting. It might be overkill but piece by piece I'm turning my Trek > >> 7100 into a 7300. I broken spoke, causing me to limp home with a > >> detached brake, is just really annoying. > > > >That $120 + shipping wheel looks pretty good, but I think it's maybe > >not money well spent. Your hub and rim are probably fine, so replacing > >them won't get you any further. I'd get $26 worth of DT spokes from > >Performance and swap them out myself. Do them one-by-one and it'll work > >out fine. And pretend someone is paying you $100 to do it! > > > >Joseph > > Ah, but it's 20% off! Who can resist that bargin? Plus, it would take > me a lot of time to replace each spoke and true it after each one > since I dare not wait until the end to true it. > > Besides, it is the holiday season. > > I'm more worried that I may run into a problem because of the spacer > requirement for my bike. The spacer will work fine. But I'd still go for replacing the spokes. the LBS (even an expensive Manhattan one!) could replace them for less than that wheel and one would hope that it would be built well, at least as well and probably much better than the Performance wheel. Joseph     Date: 06 Dec 2006 16:19:58 From: dgk Subject: Re: I fixed a broken spoke! On 5 Dec 2006 13:24:35 -0800, joseph.santaniello@gmail.com wrote: > >The spacer will work fine. But I'd still go for replacing the spokes. >the LBS (even an expensive Manhattan one!) could replace them for less >than that wheel and one would hope that it would be built well, at >least as well and probably much better than the Performance wheel. > >Joseph I spoke to the LBS. They said that the wheel I have doesn't really pay to put good spokes in. It isn't a terrible wheel but putting good spokes in it would cost more than the thing is worth. They suggested buying a new wheel, $60 - $75 range. I figured that I'd get the Shimano one instead. I know that comes with the better spokes. The LBS gets plenty of other business from me. Really, the other option was to buy a new bike, say around $500. I'd do it but I just don't see how I can keep it from getting stolen.   Date: 05 Dec 2006 11:12:43 From: Subject: Re: I fixed a broken spoke! dgk wrote: > On 5 Dec 2006 08:09:21 -0800, joseph.santaniello@gmail.com wrote: > > > > >dgk wrote: > >> On 4 Dec 2006 13:48:49 -0800, joseph.santaniello@gmail.com wrote: > >> > >> > > >> >jobst.brandt@stanfordalumni.org wrote: > >> >> Joseph Santaniello writes: > >> >> > >> >> > If you are breaking non-drive side spokes, this indicates without a > >> >> > doubt that they are crap spokes. (based on info from your previous > >> >> > posts, that you don't weigh 400lbs,etc) > >> >> > >> >> Even the best spokes fail if they are not formed to the hub and stress > >> >> relieved. Don't push it off on the spoke manufacturer when it's the > >> >> builder who needs to take measures to make the wheel durable. > >> >> > >> >> Jobst Brandt > >> > > >> >Perhaps, but I was making some assumptions based on previous posts. As > >> >I recall this is an inexpensive machine built wheel as spec'd for a > >> >$350 bike that doesn't see particularly heavy use. I'll bet they are > >> >cheap spokes AND they are not formed to the hub nor stress-relieved. > >> > > >> >Joseph > >> > >> Recall correct. Except that, being a hybrid, the rear wheel does get a > >> lot of weight, Especially since the travel bag sits over it. > > > >They weight distribution difference from the hybrid configuration is > >minimal. The travel bag could make a difference, but unless you are > >carrying around several dehydrated grandfather clocks, your total > >weight is still well within range of what should not be a problem for > >36 spoke wheels. > > > >Joseph > > Good. I just posted about a Shimano wheel that I'm thinking about > getting. It might be overkill but piece by piece I'm turning my Trek > 7100 into a 7300. I broken spoke, causing me to limp home with a > detached brake, is just really annoying. That $120 + shipping wheel looks pretty good, but I think it's maybe not money well spent. Your hub and rim are probably fine, so replacing them won't get you any further. I'd get $26 worth of DT spokes from Performance and swap them out myself. Do them one-by-one and it'll work out fine. And pretend someone is paying you $100 to do it! Joseph     Date: 05 Dec 2006 14:49:13 From: dgk Subject: Re: I fixed a broken spoke! On 5 Dec 2006 11:12:43 -0800, joseph.santaniello@gmail.com wrote: > >dgk wrote: >> On 5 Dec 2006 08:09:21 -0800, joseph.santaniello@gmail.com wrote: >> >> >> Good. I just posted about a Shimano wheel that I'm thinking about >> getting. It might be overkill but piece by piece I'm turning my Trek >> 7100 into a 7300. I broken spoke, causing me to limp home with a >> detached brake, is just really annoying. > >That $120 + shipping wheel looks pretty good, but I think it's maybe >not money well spent. Your hub and rim are probably fine, so replacing >them won't get you any further. I'd get $26 worth of DT spokes from >Performance and swap them out myself. Do them one-by-one and it'll work >out fine. And pretend someone is paying you $100 to do it! > >Joseph Ah, but it's 20% off! Who can resist that bargin? Plus, it would take me a lot of time to replace each spoke and true it after each one since I dare not wait until the end to true it. Besides, it is the holiday season. I'm more worried that I may run into a problem because of the spacer requirement for my bike.   Date: 05 Dec 2006 08:09:21 From: Subject: Re: I fixed a broken spoke! dgk wrote: > On 4 Dec 2006 13:48:49 -0800, joseph.santaniello@gmail.com wrote: > > > > >jobst.brandt@stanfordalumni.org wrote: > >> Joseph Santaniello writes: > >> > >> > If you are breaking non-drive side spokes, this indicates without a > >> > doubt that they are crap spokes. (based on info from your previous > >> > posts, that you don't weigh 400lbs,etc) > >> > >> Even the best spokes fail if they are not formed to the hub and stress > >> relieved. Don't push it off on the spoke manufacturer when it's the > >> builder who needs to take measures to make the wheel durable. > >> > >> Jobst Brandt > > > >Perhaps, but I was making some assumptions based on previous posts. As > >I recall this is an inexpensive machine built wheel as spec'd for a > >$350 bike that doesn't see particularly heavy use. I'll bet they are > >cheap spokes AND they are not formed to the hub nor stress-relieved. > > > >Joseph > > Recall correct. Except that, being a hybrid, the rear wheel does get a > lot of weight, Especially since the travel bag sits over it. They weight distribution difference from the hybrid configuration is minimal. The travel bag could make a difference, but unless you are carrying around several dehydrated grandfather clocks, your total weight is still well within range of what should not be a problem for 36 spoke wheels. Joseph     Date: 05 Dec 2006 12:47:58 From: dgk Subject: Re: I fixed a broken spoke! On 5 Dec 2006 08:09:21 -0800, joseph.santaniello@gmail.com wrote: > >dgk wrote: >> On 4 Dec 2006 13:48:49 -0800, joseph.santaniello@gmail.com wrote: >> >> > >> >jobst.brandt@stanfordalumni.org wrote: >> >> Joseph Santaniello writes: >> >> >> >> > If you are breaking non-drive side spokes, this indicates without a >> >> > doubt that they are crap spokes. (based on info from your previous >> >> > posts, that you don't weigh 400lbs,etc) >> >> >> >> Even the best spokes fail if they are not formed to the hub and stress >> >> relieved. Don't push it off on the spoke manufacturer when it's the >> >> builder who needs to take measures to make the wheel durable. >> >> >> >> Jobst Brandt >> > >> >Perhaps, but I was making some assumptions based on previous posts. As >> >I recall this is an inexpensive machine built wheel as spec'd for a >> >$350 bike that doesn't see particularly heavy use. I'll bet they are >> >cheap spokes AND they are not formed to the hub nor stress-relieved. >> > >> >Joseph >> >> Recall correct. Except that, being a hybrid, the rear wheel does get a >> lot of weight, Especially since the travel bag sits over it. > >They weight distribution difference from the hybrid configuration is >minimal. The travel bag could make a difference, but unless you are >carrying around several dehydrated grandfather clocks, your total >weight is still well within range of what should not be a problem for >36 spoke wheels. > >Joseph Good. I just posted about a Shimano wheel that I'm thinking about getting. It might be overkill but piece by piece I'm turning my Trek 7100 into a 7300. I broken spoke, causing me to limp home with a detached brake, is just really annoying.   Date: 04 Dec 2006 18:04:48 From: Johnny Sunset aka Tom Sherman Subject: Re: I fixed a broken spoke! Jobst Brandt wrote: > someone writes: > > >>> If you are breaking non-drive side spokes, this indicates without > >>> a doubt that they are crap spokes. (based on info from your > >>> previous posts, that you don't weigh 400lbs,etc) > > >> Even the best spokes fail if they are not formed to the hub and > >> stress relieved. Don't push it off on the spoke manufacturer when > >> it's the builder who needs to take measures to make the wheel > >> durable. > > > Stress relief is just going around the wheel sort of pinching the > > spokes? > > There's more to it than that, but yes. A better method of stress > relief is to stand the wheel on its axle and press down on the rim > with hands diametrically opposite, once between each pair of spokes. > > However, first the outbound spokes must be manually bent to lie flush > against the flange. Then by grasping pairs of spokes on opposite > sides of the wheel and squeezing them together will make sure that > your wheel is not too tight. Dear Jobst, What is your opinion of this book: <http://sheldonbrown.com/harris/books.html#brandt >? Thank you, J. Sunset   Date: 04 Dec 2006 15:32:11 From: Subject: Re: I fixed a broken spoke! dgk wrote: > On 04 Dec 2006 20:55:44 GMT, jobst.brandt@stanfordalumni.org wrote: > > >Joseph Santaniello writes: > > > >> If you are breaking non-drive side spokes, this indicates without a > >> doubt that they are crap spokes. (based on info from your previous > >> posts, that you don't weigh 400lbs,etc) > > > >Even the best spokes fail if they are not formed to the hub and stress > >relieved. Don't push it off on the spoke manufacturer when it's the > >builder who needs to take measures to make the wheel durable. > > > >Jobst Brandt > > Stress relief is just going around the wheel sort of pinching the > spokes? Dear DGK, Forgive me, but your innocent response is too good not to cross-post to rec.bicycles.tech. While pinching spoke pairs together probably helps to seat the spokes in the hub and the nipples in the rim, tests showed no further residual stresses being relieved after ordinary spoke tension, even when tension was much higher than the typical 60-lb tension increase that other testing shows can be achieved by pinching. I pinched spokes together on various wheels with known forces and measured the tension changes. Despite the impressive bending, the spoke tension rose only about 55~65 for a 60 lb pinch. (The bending was not due to the spokes being stretched by tremendous tension increases, but to the slack gained when the rims bent into faint N or Z shapes.) I bent new stainless steel spokes into a near-U, tensioned them in a bench-vise rig up to 394 lbs, and measured how far the spoke ends moved when the residual stresses in the U-bends were relieved by heating to glowing orange with a propane torch. As would be expected, the greatest movement (most residual stress exposed) occurred when the bent spoke had not been tensioned at all. Modest tension quickly reduced the amount that the spoke ends would move when the bend was heated, suggesting that some residual stresses had been relieved by the initial tension. By the time that tension reached the lowest level of an ordinary bicycle wheel, scarcely any effect was seen when the bends were heated. The most likely explanation for an occasional spoke breaking is variation in the spoke material. The bending and tensioning and so forth are quite regular. If pinching the spokes were solving some residual stress problem, the same problem would be causing all the other spokes to fail. There's no question that improvements in spoke material have reduced spoke failure dramatically. Spokes are still being bent and formed the same way, but ten years after his book's first edition, Jobst high-lighted the improvement in spokes in his 3rd edition: "It appears that the better spokes now available would have made the discovery of many of the concepts of this book more difficult for lack of failure data. I am grateful in retrospect for the poor durability of earlier spokes. They operated so near their limits that durability was significantly altered by the techniques that I have outlined." --Jobst Brandt, "The Bicycle Wheel," 3rd Edition, 1993, p.124 So pinch 'em and expect improved seating, but don't expect miracles in residual stress relief. That's achieved just by raising the tension to normal levels. Cheers, Carl Fogel     Date: 31 Dec 2006 01:44:22 From: Subject: Re: I fixed a broken spoke! Carl Fogel writes: >>>> If you are breaking non-drive side spokes, this indicates without >>>> a doubt that they are crap spokes. (based on info from your >>>> previous posts, that you don't weigh 400lbs,etc) >>> Even the best spokes fail if they are not formed to the hub and >>> stress relieved. Don't push it off on the spoke manufacturer when >>> it's the builder who needs to take measures to make the wheel >>> durable. >> Stress relief is just going around the wheel sort of pinching the >> spokes? > Forgive me, but your innocent response is too good not to cross-post > to rec.bicycles.tech. Don't be so condescending about finding an opening to present your belief in the misplaced experiments you performed to support your belief in stress relief. You are not forgiven. > While pinching spoke pairs together probably helps to seat the > spokes in the hub and the nipples in the rim, tests showed no > further residual stresses being relieved after ordinary spoke > tension, even when tension was much higher than the typical 60-lb > tension increase that other testing shows can be achieved by > pinching. Consider that typically an outbound spoke is bent to yield when tightened after a wheel is laced. This is apparent from its elbow bend that was obtuse when new and acute after a wheel build. That the elbow that is raised to tensile yield during tensioning should be evident because all additional tension can only yield that portion of the spoke in the elbow further. It will remain at yield, there being no mechanism to make it less than that. Because no over-tensioning followed by relaxation (manually stretching spokes) is used, the elbow must be at yield in the finished wheel. Therefore, the residual stress from elbow modification remains with that spoke that is tensioned to less than yield stress in the absence of stress relieving. Your heating experiment was done on a relaxed spoke and does not reveal what the tension was on the outside of an elbow bend, for instance. If you raised your spoke tension to yield stress prior to relaxing it and heating, then it is evidence of stress relieving by momentary over-stress, nothing more. > I pinched spokes together on various wheels with known forces and > measured the tension changes. Despite the impressive bending, the > spoke tension rose only about 55~65 for a 60 lb pinch. (The bending > was not due to the spokes being stretched by tremendous tension > increases, but to the slack gained when the rims bent into faint N > or Z shapes.) Any momentary overload will cause yielding in the portions of a spoke that are at tensile yield stress and relaxing that overload constitutes stress relief. I don't see what is not obvious about that process. Jobst Brandt       Date: 30 Dec 2006 19:18:54 From: jim beam Subject: Re: I fixed a broken spoke! jobst.brandt@stanfordalumni.org wrote: > Carl Fogel writes: > >>>>> If you are breaking non-drive side spokes, this indicates without >>>>> a doubt that they are crap spokes. (based on info from your >>>>> previous posts, that you don't weigh 400lbs,etc) > >>>> Even the best spokes fail if they are not formed to the hub and >>>> stress relieved. Don't push it off on the spoke manufacturer when >>>> it's the builder who needs to take measures to make the wheel >>>> durable. > >>> Stress relief is just going around the wheel sort of pinching the >>> spokes? > >> Forgive me, but your innocent response is too good not to cross-post >> to rec.bicycles.tech. > > Don't be so condescending about finding an opening to present your > belief in the misplaced experiments you performed to support your > belief in stress relief. You are not forgiven. > >> While pinching spoke pairs together probably helps to seat the >> spokes in the hub and the nipples in the rim, tests showed no >> further residual stresses being relieved after ordinary spoke >> tension, even when tension was much higher than the typical 60-lb >> tension increase that other testing shows can be achieved by >> pinching. > > Consider that typically an outbound spoke is bent to yield when > tightened after a wheel is laced. This is apparent from its elbow > bend that was obtuse when new and acute after a wheel build. That the > elbow that is raised to tensile yield during tensioning should be > evident because all additional tension can only yield that portion of > the spoke in the elbow further. It will remain at yield, there being > no mechanism to make it less than that. > > Because no over-tensioning followed by relaxation (manually stretching > spokes) is used, the elbow must be at yield in the finished wheel. > Therefore, the residual stress from elbow modification remains with > that spoke that is tensioned to less than yield stress in the absence > of stress relieving. > > Your heating experiment was done on a relaxed spoke and does not > reveal what the tension was on the outside of an elbow bend, for > instance. If you raised your spoke tension to yield stress prior to > relaxing it and heating, then it is evidence of stress relieving by > momentary over-stress, nothing more. > >> I pinched spokes together on various wheels with known forces and >> measured the tension changes. Despite the impressive bending, the >> spoke tension rose only about 55~65 for a 60 lb pinch. (The bending >> was not due to the spokes being stretched by tremendous tension >> increases, but to the slack gained when the rims bent into faint N >> or Z shapes.) > > Any momentary overload will cause yielding in the portions of a spoke > that are at tensile yield stress and relaxing that overload > constitutes stress relief. I don't see what is not obvious about that > process. i'm an [ex] metallurgist, and i see nothing "obvious" about this supposition at all. you repeatedly prove know nothing about materials [particularly fatigue or deformation - metal yields to zero "brick dragging" b.s!!!!], you've done no testing, you have no data. you even have the temerity to claim "invention" of wheel building practice that dates before your birth. and yet here you are, years after being confronted with facts and data that would allow you to correct your mistakes, still in denial. you've even been asked to perform simple [cheap] industry standard testing that could /prove/ you correct if you're so damned confident, but you won't. why not? this is not a technology problem: this is an i.q. problem.       Date: 30 Dec 2006 19:02:10 From: Subject: Re: I fixed a broken spoke! On 31 Dec 2006 01:44:22 GMT, jobst.brandt@stanfordalumni.org wrote: >Carl Fogel writes: > >>>>> If you are breaking non-drive side spokes, this indicates without >>>>> a doubt that they are crap spokes. (based on info from your >>>>> previous posts, that you don't weigh 400lbs,etc) > >>>> Even the best spokes fail if they are not formed to the hub and >>>> stress relieved. Don't push it off on the spoke manufacturer when >>>> it's the builder who needs to take measures to make the wheel >>>> durable. > >>> Stress relief is just going around the wheel sort of pinching the >>> spokes? > >> Forgive me, but your innocent response is too good not to cross-post >> to rec.bicycles.tech. > >Don't be so condescending about finding an opening to present your >belief in the misplaced experiments you performed to support your >belief in stress relief. You are not forgiven. [snip] Dear Jobst, Don't be such a pompous, paranoid ass, particularly 11 days after the post first appeared. Cheers, Carl Fogel     Date: 05 Dec 2006 10:30:41 From: dgk Subject: Re: I fixed a broken spoke! On 4 Dec 2006 15:32:11 -0800, carlfogel@comcast.net wrote: > >dgk wrote: >> On 04 Dec 2006 20:55:44 GMT, jobst.brandt@stanfordalumni.org wrote: >> >> >Joseph Santaniello writes: >> > >> >> If you are breaking non-drive side spokes, this indicates without a >> >> doubt that they are crap spokes. (based on info from your previous >> >> posts, that you don't weigh 400lbs,etc) >> > >> >Even the best spokes fail if they are not formed to the hub and stress >> >relieved. Don't push it off on the spoke manufacturer when it's the >> >builder who needs to take measures to make the wheel durable. >> > >> >Jobst Brandt >> >> Stress relief is just going around the wheel sort of pinching the >> spokes? > >Dear DGK, > >Forgive me, but your innocent response is too good not to cross-post to >rec.bicycles.tech. > THANKS! I can't recall the last time someone called anything about me "innocent". It's almost like being carded.     Date: 05 Dec 2006 02:15:48 From: Werehatrack Subject: Re: I fixed a broken spoke! On 4 Dec 2006 15:32:11 -0800, carlfogel@comcast.net wrote: >The most likely explanation for an occasional spoke breaking is >variation in the spoke material. The bending and tensioning and so >forth are quite regular. If pinching the spokes were solving some >residual stress problem, the same problem would be causing all the >other spokes to fail. No idea if this is relevant or not, but if the spokes in question are some of those made from the Korean steel which has now been acknowledged to have been below spec on strength and flaws, then the breakage is most likely due to that. >There's no question that improvements in spoke material have reduced >spoke failure dramatically. Spokes are still being bent and formed the >same way, but ten years after his book's first edition, Jobst >high-lighted the improvement in spokes in his 3rd edition: > >"It appears that the better spokes now available would have made the >discovery of many of the concepts of this book more difficult for lack >of failure data. I am grateful in retrospect for the poor durability of >earlier spokes. They operated so near their limits that durability was >significantly altered by the techniques that I have outlined." > >--Jobst Brandt, "The Bicycle Wheel," 3rd Edition, 1993, p.124 And the speed with which spoke failures became common again when just one prolific mill was producing substandard wire, was quite demonstrative of the accuracy of Jobst's statements. >So pinch 'em and expect improved seating, but don't expect miracles in >residual stress relief. That's achieved just by raising the tension to >normal levels. OTOH, it couldn't hurt, either, and once in a while it'll be just enough to reveal the one ready-to-fail spoke lurking in the bunch. -- Typoes are a feature, not a bug. Some gardening required to reply via email. Words processed in a facility that contains nuts.   Date: 04 Dec 2006 13:48:49 From: Subject: Re: I fixed a broken spoke! jobst.brandt@stanfordalumni.org wrote: > Joseph Santaniello writes: > > > If you are breaking non-drive side spokes, this indicates without a > > doubt that they are crap spokes. (based on info from your previous > > posts, that you don't weigh 400lbs,etc) > > Even the best spokes fail if they are not formed to the hub and stress > relieved. Don't push it off on the spoke manufacturer when it's the > builder who needs to take measures to make the wheel durable. > > Jobst Brandt Perhaps, but I was making some assumptions based on previous posts. As I recall this is an inexpensive machine built wheel as spec'd for a $350 bike that doesn't see particularly heavy use. I'll bet they are cheap spokes AND they are not formed to the hub nor stress-relieved. Joseph     Date: 05 Dec 2006 10:32:28 From: dgk Subject: Re: I fixed a broken spoke! On 4 Dec 2006 13:48:49 -0800, joseph.santaniello@gmail.com wrote: > >jobst.brandt@stanfordalumni.org wrote: >> Joseph Santaniello writes: >> >> > If you are breaking non-drive side spokes, this indicates without a >> > doubt that they are crap spokes. (based on info from your previous >> > posts, that you don't weigh 400lbs,etc) >> >> Even the best spokes fail if they are not formed to the hub and stress >> relieved. Don't push it off on the spoke manufacturer when it's the >> builder who needs to take measures to make the wheel durable. >> >> Jobst Brandt > >Perhaps, but I was making some assumptions based on previous posts. As >I recall this is an inexpensive machine built wheel as spec'd for a >$350 bike that doesn't see particularly heavy use. I'll bet they are >cheap spokes AND they are not formed to the hub nor stress-relieved. > >Joseph Recall correct. Except that, being a hybrid, the rear wheel does get a lot of weight, Especially since the travel bag sits over it.   Date: 04 Dec 2006 12:28:29 From: Subject: Re: I fixed a broken spoke! joseph.santanie...@gmail.com wrote: > dgk wrote: > > Which correctly implies that I broke another one. I got lucky; this > > one was not on the drive side. So I took a spoke from a retired wheel > > (rear wheel same bike) and replaced the broken one using the same > > pattern as the nearby spokes. > > > > Once I put the wheel on the bike I was able to true it pretty well by > > seeing how that section passed the brakes. A few twists and it kept > > the same distance as the rest of the wheel. It rode fine this morning. > > > > I was just on the SheldonBrown site looking at freehubs, and it looks > > easy enough to remove the cassette. I think I'll almost look forward > > to the next broken spoke so I have an excuse to remove the cassette. > > It's almost sure to be on the drive side. > > > > Do I have to be concerned about Dish? It seems that if the rest of the > > wheel is correct and this one spoke has been adjusted so that the rim > > is straight, then the dish is correct? > > Way to go! Soon you'll be building your own wheels! > > Dish cannot be changed by one spoke. It is regulated by the average > tension difference between sides. That means the drive side is usually > a lot tighter to pull the rim that way, instead of having it centered > between the flanges, as on a front wheel (which has even tension, and > thus no dish.) > > The cassette tool is a good one to have. > > Joseph PS: If you are breaking non-drive side spokes, this indicates without a doubt that they are crap spokes. (based on info from your previous posts, that you don't weigh 400lbs,etc) Joseph     Date: 19 Dec 2006 12:00:16 From: Gary Young Subject: Re: I fixed a broken spoke! On Tue, 19 Dec 2006 10:13:17 -0700, carlfogel wrote: > On Tue, 19 Dec 2006 04:30:54 -0600, Gary Young <garyyoung3@gmail.com> > wrote: > > [snip] > > Dear Gary, > > For what it's worth, Sapim disagrees with the common practice of > "correcting the spoke line." > > Here's their FAQ comment on 95 degree elbow angles and whether spokes > should be bent ("forced") to change the angle: > > "If material is forced while lacing the hub, the spokes can be pulled > over causing material weakness." > > "The original bend angle of 95° should remain intact." > > http://www.sapim.be/index.php?st=fa > > Cheers, > > Carl Fogel Carl, Unlike "jim beam," I'm not inclined to take what manufacturers say on faith. (For that matter, neither is jim beam, it seems -- for instance, he thinks the center sections of Wheelsmith spokes are ground despite what they say on their website.) Furthermore, just on its face this faq doesn't inspire a whole lot of confidence. Examples -- sapim recommends that if you break one or two spokes, it's best to replace all of the spokes (apparently even if the broken spokes failed because of surface nicks). Better yet, you should replace the entire hub! "SAPIM draws wire in such way that no change in molecular material structure occurs." Seems a little oversweeping to this layman. No change in structure even when the spoke is butted and the elbow, head and threads are formed? "The spoke does not twist much when it is built into a wheel." This sentence immediately follows the one above. Are they trying to say that twisting is a function of the molecular structure? I thought it was a function of the thickness and cross-section of the spoke. Indeed, the faq goes on to say that elliptical spokes like sapim's CX-Ray are prone to twisting. A break at the thread "often occurs as a result of nipple/rim and spoke mis-alignment." I believe that's the reason that Jobst suggests correcting the spoke line at the nipple. What does sapim propose be done about misalignment? "If spokes are used which are too long, new threads in the nipple will be made. Under heavy pressure the spoke threads will be stressed too greatly." Huh? If anything, it would be the nipple making new threads in the spoke (though wouldn't the nipple be too soft?). Maybe they mean that as the unthreaded part of the spoke is drawn up, it would destroy the threads inside the nipple.       Date: 19 Dec 2006 12:51:10 From: Subject: Re: I fixed a broken spoke! On Tue, 19 Dec 2006 12:00:16 -0600, Gary Young <garyyoung3@gmail.com > wrote: >On Tue, 19 Dec 2006 10:13:17 -0700, carlfogel wrote: > >> On Tue, 19 Dec 2006 04:30:54 -0600, Gary Young <garyyoung3@gmail.com> >> wrote: >> >> [snip] >> >> Dear Gary, >> >> For what it's worth, Sapim disagrees with the common practice of >> "correcting the spoke line." >> >> Here's their FAQ comment on 95 degree elbow angles and whether spokes >> should be bent ("forced") to change the angle: >> >> "If material is forced while lacing the hub, the spokes can be pulled >> over causing material weakness." >> >> "The original bend angle of 95° should remain intact." >> >> http://www.sapim.be/index.php?st=fa >> >> Cheers, >> >> Carl Fogel > >Carl, >Unlike "jim beam," I'm not inclined to take what manufacturers say on >faith. (For that matter, neither is jim beam, it seems -- for instance, he >thinks the center sections of Wheelsmith spokes are ground despite >what they say on their website.) > >Furthermore, just on its face this faq doesn't inspire a whole lot of >confidence. > >Examples -- sapim recommends that if you break one or two spokes, it's >best to replace all of the spokes (apparently even if the broken spokes >failed because of surface nicks). Better yet, you should replace the >entire hub! > >"SAPIM draws wire in such way that no change in molecular material >structure occurs." Seems a little oversweeping to this layman. No change >in structure even when the spoke is butted and the elbow, head and threads >are formed? > >"The spoke does not twist much when it is built into a wheel." This >sentence immediately follows the one above. Are they trying to say that >twisting is a function of the molecular structure? I thought it was a >function of the thickness and cross-section of the spoke. Indeed, the faq >goes on to say that elliptical spokes like sapim's CX-Ray are prone to >twisting. > >A break at the thread "often occurs as a result of nipple/rim and spoke >mis-alignment." I believe that's the reason that Jobst suggests correcting >the spoke line at the nipple. What does sapim propose be done about >misalignment? > >"If spokes are used which are too long, new threads in the nipple will be >made. Under heavy pressure the spoke threads will be stressed too >greatly." Huh? If anything, it would be the nipple making new threads in >the spoke (though wouldn't the nipple be too soft?). Maybe they mean that >as the unthreaded part of the spoke is drawn up, it would destroy the >threads inside the nipple. Dear Gary, For what it's worth, posters on RBT often recommend replacing all spokes if one or two break. You might also try to pin down some actual explanations for what the pros and cons are for trying to hand-bend spokes to touch (or come close to) hub flanges. But don't hope for any actual testing or statistics. Cheers, Carl Fogel     Date: 04 Dec 2006 20:55:44 From: Subject: Re: I fixed a broken spoke! Joseph Santaniello writes: > If you are breaking non-drive side spokes, this indicates without a > doubt that they are crap spokes. (based on info from your previous > posts, that you don't weigh 400lbs,etc) Even the best spokes fail if they are not formed to the hub and stress relieved. Don't push it off on the spoke manufacturer when it's the builder who needs to take measures to make the wheel durable. Jobst Brandt       Date: 04 Dec 2006 16:12:37 From: dgk Subject: Re: I fixed a broken spoke! On 04 Dec 2006 20:55:44 GMT, jobst.brandt@stanfordalumni.org wrote: >Joseph Santaniello writes: > >> If you are breaking non-drive side spokes, this indicates without a >> doubt that they are crap spokes. (based on info from your previous >> posts, that you don't weigh 400lbs,etc) > >Even the best spokes fail if they are not formed to the hub and stress >relieved. Don't push it off on the spoke manufacturer when it's the >builder who needs to take measures to make the wheel durable. > >Jobst Brandt Stress relief is just going around the wheel sort of pinching the spokes?         Date: 19 Dec 2006 21:33:47 From: Subject: Re: I fixed a broken spoke! Gary Young wrote: > Well, I can't say I understand the crux of your disagreement with > Jobst, but I'm trying to work my way through it. Carl is an ex-teacher who readily admits that he can't stop grading folks here. Teachers, of course, choose to spend their career surrounded by persons who are known to be inferior to themselves; in other words, in flight from the normal situation in which we are surrounded by peers at work and will be judged by our deeds and abilities. Of course, after decades of anything, it's hard to decompress; hence his endless attempts to turn r.b.t. readers into his students by pretending to teach them things which they already know. This bit of self-deceipt works well but not 100% - much to his dismay, Carl cannot shut out the realization that Jobst knows more and also is ster - and it drives him crazy. Of course, Jobst is here as a teacher as well. In ten years of reading I have yet to see him ask a [non-sarcastic or non-rhetorical] question here. He is not here to learn anything, so why is he here? It can only be to teach. At the crux of these recent disagreements that Carl has initiated is competition for self-perception. Doug           Date: 19 Dec 2006 21:36:52 From: jim beam Subject: Re: I fixed a broken spoke! doug.landau@gmail.com wrote: > Gary Young wrote: > >> Well, I can't say I understand the crux of your disagreement with >> Jobst, but I'm trying to work my way through it. > > Carl is an ex-teacher who readily admits that he can't stop grading > folks here. Teachers, of course, choose to spend their career > surrounded by persons who are known to be inferior to themselves; in > other words, in flight from the normal situation in which we are > surrounded by peers at work and will be judged by our deeds and > abilities. > > Of course, after decades of anything, it's hard to decompress; hence > his endless attempts to turn r.b.t. readers into his students by > pretending to teach them things which they already know. This bit of > self-deceipt works well but not 100% - much to his dismay, Carl cannot > shut out the realization that Jobst knows more and also is ster - > and it drives him crazy. > > Of course, Jobst is here as a teacher as well. In ten years of reading > I have yet to see him ask a [non-sarcastic or non-rhetorical] question > here. He is not here to learn anything, so why is he here? It can > only be to teach. shame he doesn't teach the truth. shame others don't ask questions. > > At the crux of these recent disagreements that Carl has initiated is > competition for self-perception. > > Doug >         Date: 19 Dec 2006 14:05:00 From: Gary Young Subject: Re: I fixed a broken spoke! On Tue, 19 Dec 2006 12:51:10 -0700, carlfogel wrote: > On Tue, 19 Dec 2006 12:00:16 -0600, Gary Young <garyyoung3@gmail.com> > wrote: > >>On Tue, 19 Dec 2006 10:13:17 -0700, carlfogel wrote: >> >>> On Tue, 19 Dec 2006 04:30:54 -0600, Gary Young <garyyoung3@gmail.com> >>> wrote: >>> >>> [snip] >>> >>> Dear Gary, >>> >>> For what it's worth, Sapim disagrees with the common practice of >>> "correcting the spoke line." >>> >>> Here's their FAQ comment on 95 degree elbow angles and whether spokes >>> should be bent ("forced") to change the angle: >>> >>> "If material is forced while lacing the hub, the spokes can be pulled >>> over causing material weakness." >>> >>> "The original bend angle of 95° should remain intact." >>> >>> http://www.sapim.be/index.php?st=fa >>> >>> Cheers, >>> >>> Carl Fogel >> >>Carl, >>Unlike "jim beam," I'm not inclined to take what manufacturers say on >>faith. (For that matter, neither is jim beam, it seems -- for instance, he >>thinks the center sections of Wheelsmith spokes are ground despite >>what they say on their website.) >> >>Furthermore, just on its face this faq doesn't inspire a whole lot of >>confidence. >> >>Examples -- sapim recommends that if you break one or two spokes, it's >>best to replace all of the spokes (apparently even if the broken spokes >>failed because of surface nicks). Better yet, you should replace the >>entire hub! >> >>"SAPIM draws wire in such way that no change in molecular material >>structure occurs." Seems a little oversweeping to this layman. No change >>in structure even when the spoke is butted and the elbow, head and threads >>are formed? >> >>"The spoke does not twist much when it is built into a wheel." This >>sentence immediately follows the one above. Are they trying to say that >>twisting is a function of the molecular structure? I thought it was a >>function of the thickness and cross-section of the spoke. Indeed, the faq >>goes on to say that elliptical spokes like sapim's CX-Ray are prone to >>twisting. >> >>A break at the thread "often occurs as a result of nipple/rim and spoke >>mis-alignment." I believe that's the reason that Jobst suggests correcting >>the spoke line at the nipple. What does sapim propose be done about >>misalignment? >> >>"If spokes are used which are too long, new threads in the nipple will be >>made. Under heavy pressure the spoke threads will be stressed too >>greatly." Huh? If anything, it would be the nipple making new threads in >>the spoke (though wouldn't the nipple be too soft?). Maybe they mean that >>as the unthreaded part of the spoke is drawn up, it would destroy the >>threads inside the nipple. > > Dear Gary, > > For what it's worth, posters on RBT often recommend replacing all > spokes if one or two break. True -- if one has reason to believe that the first couple of spokes failed because of fatigue without any outward signs of damage. It was my impression, however, that if the broken spokes were visibly damaged (e.g., by the chain jamming between the cassette and spokes), then there's no reason to replace the spokes that aren't so damaged. And what about replacing the hub? How do fatigue failures damage the spoke holes? > > You might also try to pin down some actual explanations for what the > pros and cons are for trying to hand-bend spokes to touch (or come > close to) hub flanges. > > But don't hope for any actual testing or statistics. Well, I can't say I understand the crux of your disagreement with Jobst, but I'm trying to work my way through it. > > Cheers, > > Carl Fogel           Date: 20 Dec 2006 01:53:18 From: Subject: Re: I fixed a broken spoke! On Tue, 19 Dec 2006 14:05:00 -0600, Gary Young <garyyoung3@gmail.com > wrote: [snip] >Well, I can't say I understand the crux of your disagreement with >Jobst, but I'm trying to work my way through it. [snip] Dear Gary, So am I. For decades, riders usually carried a few spare spokes on tours because they expected spokes to break. Jobst has mentioned this practice. In the early 1980's, Jobst wrote "The Bicycle Wheel" and theorized that squeezing spoke pairs together would relieve residual stress in spoke bends. But ten years later, Jobst wrote "It appears that the better spokes now available would have made the discovery of many of the concepts of this book more difficult for lack of failure data. I am grateful in retrospect for the poor durability of earlier spokes. They operated so near their limits that durability was significantly altered by the techniques that I have outlined." --Jobst Brandt, "The Bicycle Wheel," 3rd Edition, 1993, p.124 I agree that spokes have become much more durable. The evidence is overwhelming. Few riders bother to carry spare spokes any more, partly because they have cell phones, but mostly because they don't expect spokes to break very often. The 36-spoke wheels of the past have been replaced by wheels with fewer and fewer spokes. Despite the obvious increase in stress, the spokes last longer. The spokes are the same length and thickness. The threading and elbow bends are made in the same way. The only real change has been years of steady improvement in the quality of the stainless steel wire. After all, the most likely explanation for an occasional spoke breaking is variation in the spoke material. The bending and tensioning and so forth are quite regular. If squeezing spoke pairs was solving some residual stress problem by raising tension, the same problem would be causing all the other spokes to fail. I see Jobst's comment in 1993 that spokes somehow became much more durable as strong evidence that he was mistaken about how efffective spoke-sqeezing is. I also see the lack of variation in results as evidence that spoke-squeezers are fooling themselves. The repeated claim that squeezing makes spokes immortal implies that there is no level at which the spokes are merely given longer lifespans. Everyone seems to believe that they squeeze just as strongly with their weak hand as they do with their strong hand, and just as strongly the ninth time as they do the first time. I'm unable to find any testing or evidence that supports the claim, as opposed claims that one step out of many in building a wheel must be responsible for anecdotal improvements. Again, look at the strange comment in the 3rd edition. Spokes somehow became so durable in a decade that Jobst wrote that it would have been hard to "discover" his theory. I see it as evidence that his theory was wrong. The lack of testing and measuring to confirm the theory is curious. Until I started hanging weights from spokes and measuring the tension changes with a gauge, RBT posters would make good-faith theoretical calculations that showed huge tension increases. This illustrates how easily we fool ourselves and how easy it is to make huge mistakes. I have never doubted the good faith of the last such calculation that appeared on RBT. A 30 pound side force moved a spoke a certain distance and bent the spoke at such and so an angle, which in turn allowed calculations for steel of specifc thickness to indicate that the spoke tension would rise approximately 150 pounds, a 5 to 1 ratio. The calculations were correct, but they were based on the assumption that the rim and the hub would stay in fixed positions. How could a newsgroup full of wheel-builders assume that the rim would stay in a fixed position when tension increased 150 pounds? I'm just as guilty as everyone else who read such posts over the years without raising an eyebrow. The huge tension increase seemed plausible and certainly supported Jobst's theory. But I was curious enough to fiddle around until I finally figured out an obvious way to measure the tension increase directly. Oops! A 30-pound squeeze force on a left and a right spoke-pair will raise the spoke tension only about 30 pounds, not 150. A 60-pound squeeze will raise tension only about 55~65 pounds. Higher squeeze forces are unlikely for most RBT posters. A 100-pound squeeze will leave a faint permanent bend in a spoke. The impressive bend angles are due mostly to the slack gained as the four obviously unbalanced spokes twist the rim into a slight N or Z shape. (A weird detail is that spoke tension actually drops as you start to squeeze. In addition to the rim deforming, the spokes are bent across other spokes in a cross-3 pattern, and they gain a little initial slack as they press into the other spoke and straighten a little at that point. The low-squeeze-force tension drop startled the hell out of me, but was so consistent that I finally had to admit that it was real. Noticing the bend where the spokes cross took an embarrassingly long time.) All of this could have been figured out and predicted as theory, but no one was trying to figure out what might be wrong with Jobst's theory. Most of us set out with an unconscious bias toward working things out in accordance with the theory. That's how sensible people can end up calculating a 150-pound spoke tension increase from 250 to 400 pounds with a 30-pound squeeze force. A moment's thought would raise the obvious objection. No one ever complains that he squeezed his spokes so hard that they stretched like taffy or pulled through the rim. But there are a number of posters who could squeeze with 100 pounds of force--which the mistaken calculation predicts would raise the spoke tension over 450 pounds, from 250 to 700. Jobst's tensile tests showed that spokes yield at around 600 pounds. I tested various wheels and had fun staring at odd details and working out better and better techniques, but most of my elaborate testing was a waste of time--the results were immediately obvious. Anyone who supports one spoke with a ceiling rope, hangs a known weight on a rope tied to the spoke above it, and measures the tension with a Park gauge can see how much a 60-pound squeeze force wil raise the spoke tension. It's not a matter of great precision or poring over reams of data. It's about like weighing sacks of dog food. So spoke-squeezing didn't actually raise spoke tension anywhere near as high as people had been thinking. Their mistake was thinking instead of testing and letting theory and what they'd like to prove lead them to where they wanted to go. The next thing to test was the effect of tension on residual stress. Everyone agrees that residual stresses exist when a spoke is bent to form the elbow. The usual method of relieving residual stress is heating. Bend a stainless steel spoke 90 degrees, heat the bend to a glowing orange with a propane torch, and you can see the end of the spoke move as the bend expands. So I cobbled together a crude vise rig and started bending spokes into U shapes. A spoke bent but not stretched expands considerably when heated. A spoke bent and tensioned slightly in the vise will expand noticeably less. A spoke bent and tensioned more will expand even less. A spoke bent and tensioned to normal bicycle wheel levels (~200 lbs) will hardly expand at all. A spoke bent and tensioned to ~400 pounds will hardly expand at all, just like the spoke tensioned to ~200 pounds. I think that heating the whole bend to a glowing orange relieves any residual stresses. The spoke that was never tensioned has lots of residual stresses and its bend expands a lot. The spoke that was lightly tensioned has had its strongest residual stresses relieved byt the tension, so it bends less. By the time that tension has reached 200 pounds, practically all residual stresses have been relieved, so there's practically nothing left for the heat to change, and the spoke bend scarcely changes. The bending after heating clearly depends on how much tension is applied to the spoke. Note that rather than pursuing the testing and trying to think of ways to change the test and confirm or refute it, Jobst just complains that it's destructive. I'm willing to listen to suggestions and arguments about whether what happens is explained by stress relief, but red herrings about the destruction of a few dollars worth of spokes are absurd. My problem with the spoke-squeezing theory is that it seems to be a lot of theory developed to support preconceived and self-flattering conclusions about how we can cure the King's Evil by the laying on of hands. My counter-argument is subject to the same criticism in that I naturally want my tests and interpretations to be right. But I think that it's obvious who's interested in actual testing and measuring. There's not only a lack of interest in testing and confirmation on one side, but an explicit bias against any testing or confirmation. Anyone can read through the endless posts on the subject and see commment after comment about how no tests would be convincing evidence against the theory, how no tests are needed, and how we don't need no stinkin' tests. Of course, the stress-relief question is just a tempest in a tea-cup. But it does shed some interesting light on how prone RBT is to typing and defending theories instead of trying to test them. Cheers, Carl Fogel             Date: 28 Dec 2006 00:09:19 From: Ron Ruff Subject: Re: I fixed a broken spoke! Michael Press wrote: > > Consistent and precise mean much the same thing. I think I understand your point. If the device was very consistent, then it would be very precise... and with perfect calibration, very accurate. But what I meant in this case is that it is consistent given the lack of precision in reading it's scale. In other words I can get a reading of 21.5 on the same spoke +- ~.25, or 116kg +-3kg... and I think trying to read better than +-.25 on the scale would be difficult anyway. BTW, the biggest problem I have with the Park is the lack of *contrast* on the scale, since it is simply lines cut into the aluminum plate which is then anodized all the same color. It is difficult to read unless the lighting is good, you have good eyesight, and are looking straight at it. A scale with contrasting black on white would be a lot better...               Date: 28 Dec 2006 10:35:40 From: Subject: Re: I fixed a broken spoke! On 28 Dec 2006 00:09:19 -0800, "Ron Ruff" <rruffrruff@yahoo.com > wrote: > >Michael Press wrote: >> >> Consistent and precise mean much the same thing. > >I think I understand your point. If the device was very consistent, >then it would be very precise... No. Accuracy, precision, and consistency are _different_ things.                 Date: 30 Dec 2006 05:14:19 From: Michael Press Subject: Re: I fixed a broken spoke! In article <bg77p2t8hqj8tcptvjkigmbe4r1n2tppg4@4ax.com >, jtaylor@NOSPAM.hfx.andara.com wrote: > On 28 Dec 2006 00:09:19 -0800, "Ron Ruff" <rruffrruff@yahoo.com> > wrote: > > > > >Michael Press wrote: > >> > >> Consistent and precise mean much the same thing. > > > >I think I understand your point. If the device was very consistent, > >then it would be very precise... > > No. > > Accuracy, precision, and consistency are _different_ things. What is consistency in a laboratory? Precision is getting the same value each time you measure the same thing. -- Michael Press                   Date: 30 Dec 2006 14:55:45 From: Subject: Re: I fixed a broken spoke! On Sat, 30 Dec 2006 05:14:19 GMT, Michael Press <rubrum@pacbell.net > wrote: >In article ><bg77p2t8hqj8tcptvjkigmbe4r1n2tppg4@4ax.com>, > jtaylor@NOSPAM.hfx.andara.com wrote: > >> On 28 Dec 2006 00:09:19 -0800, "Ron Ruff" <rruffrruff@yahoo.com> >> wrote: >> >> > >> >Michael Press wrote: >> >> >> >> Consistent and precise mean much the same thing. >> > >> >I think I understand your point. If the device was very consistent, >> >then it would be very precise... >> >> No. >> >> Accuracy, precision, and consistency are _different_ things. > >What is consistency in a laboratory? > >Precision is getting the same value each time you >measure the same thing. No, that's consistency. Precision is a different thing. As is accuracy. (shakes head and mutters 'what are they teaching these young pups today...')                     Date: 31 Dec 2006 00:12:42 From: Michael Press Subject: Re: I fixed a broken spoke! In article <levcp2tlm5aj6von7tc45s64s345stbm3p@4ax.com >, jtaylor@NOSPAM.hfx.andara.com wrote: > On Sat, 30 Dec 2006 05:14:19 GMT, Michael Press <rubrum@pacbell.net> > wrote: > > >In article > ><bg77p2t8hqj8tcptvjkigmbe4r1n2tppg4@4ax.com>, > > jtaylor@NOSPAM.hfx.andara.com wrote: > > > >> On 28 Dec 2006 00:09:19 -0800, "Ron Ruff" <rruffrruff@yahoo.com> > >> wrote: > >> > >> > > >> >Michael Press wrote: > >> >> > >> >> Consistent and precise mean much the same thing. > >> > > >> >I think I understand your point. If the device was very consistent, > >> >then it would be very precise... > >> > >> No. > >> > >> Accuracy, precision, and consistency are _different_ things. > > > >What is consistency in a laboratory? > > > >Precision is getting the same value each time you > >measure the same thing. > > > No, that's consistency. > > Precision is a different thing. > > As is accuracy. > > (shakes head and mutters 'what are they teaching these young pups > today...') Read 'em and weep, smalltimer. <http://scidiv.bcc.ctc.edu/Physics/Measure&sigfigs/B-Acc-Prec-Unc.html > -- Michael Press             Date: 27 Dec 2006 18:34:47 From: Subject: Re: I fixed a broken spoke! Michael Press wrote: > In article > <1166948028.987967.312030@42g2000cwt.googlegroups.com>, > "Ron Ruff" <rruffrruff@yahoo.com> wrote: > > > I don't know if the Park tensiometer is any good but I picked one up > > from Performance when they were having their $20 off $50 with free > > shipping sale, and I'm having fun with it. It seems to be pretty > > consistent at least, if not very precise... > > Consistent and precise mean much the same thing. > > > ie a single digit on the > > scale can represent a 4 to 20 kg variation in tension. The force it > > exerts on the spoke is not that small either... considering that it > > takes ~3lb to squeeze the handle and a leverage ratio of ~8 to 1 gives > > a force of ~24lb. Supposedly their conversion table compensates for > > this... > > You think that it may not be as _accurate_ as the scale > allows. > > A clock that reads the correct time within a certain > bound is accurate to that bound. A clock whose > oscillator measures the same interval to within a > certain bound is precise to that bound. The oscillator > may have little twitches & anomalies; diurnal > variations; sensitivity to barometric pressure, > temperature, and humidity that overall add up to little > variation making the clock accurate for time telling, > but poor as a frequency standard. A clock may have a > very precise oscillator that does not oscillate at the > design frequency, making it a poor instrument for > telling time. A clock with no oscillator at all is still accurate twice a day. dl             Date: 26 Dec 2006 12:31:40 From: Subject: Re: I fixed a broken spoke! Ron Ruff wrote: > jim beam wrote: > > you can't tell what initial tension is at all! but in our case, we're > > looking for /increase/ in tension, so that's ok. now, if only we can > > address the variable L... > > L is around 290mm long in our case, and if it changed by 1mm it would > be a lot. So... we risk an error of 1/290 = about 0.3% in the tension > calculation by ignoring it. Since there is much less precision than > this in measuring d, I think we are safe to ignore it. > > Now, I wish you guys would make up and play nice and get on to more > interesting topics... Dear Ron, You may be missing where things change. Push a brake pad so that it touches the rim next to a spoke Squeeze the spoke pair. I get a sideways movement of about 6 mm on a front wheel, using my weaker hand. Now look at the spoke crossing, where a typical cross-3 spoke goes around another spoke near the hub at about 4 degrees. How much does the crossing change when you squeeze the spoke pair? The ~ 4 degree angle should flatten a bit, but I won't try to guess how much. My crossing point moved about 10 mm. In short, the spoke on a typical cross-3 wheel is already going around a bend. When I squeeze mine, the spoke moves up to 10 mm along the spoke that it crosses to a new position (and a new counter-tension from the other spoke). Meanwhile, the rim at the other end of the spoke moves up to 6 mm sideways. The rim also pulls inward some distance (much smaller, I think, but still exaggerating the "calculated" tension). At least the hub flange is pretty solid. But this mish-mash doesn't really resemble the theoretical two fixed points and a nicely centered sideways deflection. Here's a page that addresses just the problem of whether the load is applied at the center of the span: http://www.josephcurtinstudios.com/news/tech/journal_vsa/principles.htm Is the squeeze force on the bicycle spoke pair centered relative to the hub and rim, or to the crossing point and rim? Where does the rim end up? How far does the crossing flatten? How far does the crossing point move? With a tension gauge, the force is automatically centered on a short, straight spoke span with no crossing bend. Both posts are fixed, instead of one moving 6 mm sideways and the other sliding along a counter-tensioned wire. Oddly enough, the spoke tension gauge keeps giving a different answer than over-simplified calculations. It's as if the practical details that the calculations ignore lead to exaggerated results. I predict that a spoke tension gauge will show that a typical 32 or 36 spoke wheel will see a tension rise of about 55~65 pounds for four spokes at normal tension that are squeezed as two pairs with 60 pounds of force. Anyone with a tension gauge, some rope, and some weights can test my prediction. I've tested it on a variety of wheels with a tension gauge that appears to be more than accurate enough. Cheers, Carl Fogel               Date: From: Subject:             Date: 26 Dec 2006 07:38:12 From: Ron Ruff Subject: Re: I fixed a broken spoke! jim beam wrote: > you can't tell what initial tension is at all! but in our case, we're > looking for /increase/ in tension, so that's ok. now, if only we can > address the variable L... L is around 290mm long in our case, and if it changed by 1mm it would be a lot. So... we risk an error of 1/290 = about 0.3% in the tension calculation by ignoring it. Since there is much less precision than this in measuring d, I think we are safe to ignore it. Now, I wish you guys would make up and play nice and get on to more interesting topics...               Date: 26 Dec 2006 07:58:29 From: jim beam Subject: Re: I fixed a broken spoke! Ron Ruff wrote: > jim beam wrote: >> you can't tell what initial tension is at all! but in our case, we're >> looking for /increase/ in tension, so that's ok. now, if only we can >> address the variable L... > > L is around 290mm long in our case, and if it changed by 1mm it would > be a lot. So... we risk an error of 1/290 = about 0.3% in the tension > calculation by ignoring it. Since there is much less precision than > this in measuring d, I think we are safe to ignore it. > > Now, I wish you guys would make up and play nice and get on to more > interesting topics... > imagine this: [fixed width font] v concrete                 Date: 04 Jan 2007 12:32:04 From: dvt Subject: Re: I fixed a broken spoke! jim beam wrote: > imagine this: > [fixed width font] > > v > concrete                   Date: 04 Jan 2007 22:31:28 From: jim beam Subject: Re: I fixed a broken spoke! dvt wrote: > jim beam wrote: >> imagine this: >> [fixed width font] >> >> v >> concrete                     Date: 05 Jan 2007 00:48:32 From: Subject: Re: I fixed a broken spoke! On Thu, 04 Jan 2007 22:31:28 -0800, jim beam <spamvortex@bad.example.net > wrote: >dvt wrote: >> jim beam wrote: >>> imagine this: >>> [fixed width font] >>> >>> v >>> concrete                       Date: 05 Jan 2007 08:13:38 From: Peter Cole Subject: Re: I fixed a broken spoke! carlfogel@comcast.net wrote: > On Thu, 04 Jan 2007 22:31:28 -0800, jim beam > <spamvortex@bad.example.net> wrote: > >> dvt wrote: >>> jim beam wrote: >>>> imagine this: >>>> [fixed width font] >>>> >>>> v >>>> concrete                         Date: 05 Jan 2007 13:27:20 From: dvt Subject: Re: I fixed a broken spoke! Peter Cole wrote: >>> dvt wrote: >>>> jim beam wrote: >>>>> imagine this: >>>>> [fixed width font] >>>>> >>>>> v >>>>> concrete                           Date: 05 Jan 2007 14:21:03 From: Peter Cole Subject: Re: I fixed a broken spoke! dvt wrote: > Peter Cole wrote: >>>> dvt wrote: >>>>> jim beam wrote: >>>>>> imagine this: >>>>>> [fixed width font] >>>>>> >>>>>> v >>>>>> concrete                         Date: 05 Jan 2007 09:39:46 From: dgk Subject: Re: I fixed a broken spoke! On Fri, 05 Jan 2007 08:13:38 -0500, Peter Cole <peter_cole@comcast.net > wrote: >carlfogel@comcast.net wrote: >> On Thu, 04 Jan 2007 22:31:28 -0800, jim beam >> <spamvortex@bad.example.net> wrote: > >Dave was wrong. > >The angle gives the ratio of load to tension. > >In these scenarios, the load is the same, the angle different, the >tension different. What's so hard? As the OP, I think I should point out that this thread may have exceeded the length of most helmet war threads.                           Date: 05 Jan 2007 11:54:47 From: Peter Cole Subject: Re: I fixed a broken spoke! dgk wrote: > On Fri, 05 Jan 2007 08:13:38 -0500, Peter Cole > <peter_cole@comcast.net> wrote: > >> carlfogel@comcast.net wrote: >>> On Thu, 04 Jan 2007 22:31:28 -0800, jim beam >>> <spamvortex@bad.example.net> wrote: > >> Dave was wrong. >> >> The angle gives the ratio of load to tension. >> >> In these scenarios, the load is the same, the angle different, the >> tension different. What's so hard? > > As the OP, I think I should point out that this thread may have > exceeded the length of most helmet war threads. Apparently, most of the length (and tedium) was due to a basic misunderstanding of elementary physics. The worst thing about these threads is that noobs come along regularly to begin the whole process anew. It's a bore, but sometimes it's harder to let the blather stand unchallenged. What appears to be the underlying agenda in these threads is "anti-engineering", or even "anti-science". It's common for engineering to clash with intuition, but some people can't accept that.                             Date: 05 Jan 2007 18:28:15 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > dgk wrote: >> On Fri, 05 Jan 2007 08:13:38 -0500, Peter Cole >> <peter_cole@comcast.net> wrote: >> >>> carlfogel@comcast.net wrote: >>>> On Thu, 04 Jan 2007 22:31:28 -0800, jim beam >>>> <spamvortex@bad.example.net> wrote: >> >>> Dave was wrong. >>> >>> The angle gives the ratio of load to tension. >>> >>> In these scenarios, the load is the same, the angle different, the >>> tension different. What's so hard? >> >> As the OP, I think I should point out that this thread may have >> exceeded the length of most helmet war threads. > > Apparently, most of the length (and tedium) was due to a basic > misunderstanding of elementary physics. The worst thing about these > threads is that noobs come along regularly to begin the whole process > anew. It's a bore, but sometimes it's harder to let the blather stand > unchallenged. > > What appears to be the underlying agenda in these threads is > "anti-engineering", or even "anti-science". It's common for engineering > to clash with intuition, but some people can't accept that. eh? from where i'm sitting, the agenda seems to be "engineers" having a hard time coming to terms their grasp of reality. "oh, this piece of metal is springing back after i bent it - that must be residual stress" for example.                               Date: 06 Jan 2007 13:01:01 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > Peter Cole wrote: >> Apparently, most of the length (and tedium) was due to a basic >> misunderstanding of elementary physics. The worst thing about these >> threads is that noobs come along regularly to begin the whole process >> anew. It's a bore, but sometimes it's harder to let the blather stand >> unchallenged. >> >> What appears to be the underlying agenda in these threads is >> "anti-engineering", or even "anti-science". It's common for >> engineering to clash with intuition, but some people can't accept that. > > eh? from where i'm sitting, the agenda seems to be "engineers" having a > hard time coming to terms their grasp of reality. OK, perhaps you forgot where this started: I said: "I measured 7mm deflection with an initial 23lb, and 12mm with an additional 26lb (49lb total). I used hung weights, so I'm sure of the forces. I used a caliper to measure the deflections. I don't have a tensiometer, so I don't know the initial tension, but the differential should be reasonably accurate." "By the formula in Jobst's book (T=Force*length/4*displacement), I calculated a tension of 230lb for the first load, 285 for the second. So, the additional 26lb increased tension 55lb, or a little over 2:1." you replied: "that's the problem! jobst's formula doesn't account for rim distortion. you need to measure tension of the spoke directly. which exactly what fogel did." If you understood vectors, you'd have known that "L" included rim deflection. If you understood wheels (and vectors), you'd realize that even not taking that into account doesn't significantly affect the outcome. All you need to know to accurately measure spoke tension is the load and the angle. Carl understands now, how about you? Ready to retract?                                 Date: 06 Jan 2007 11:28:39 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > jim beam wrote: >> Peter Cole wrote: > >>> Apparently, most of the length (and tedium) was due to a basic >>> misunderstanding of elementary physics. The worst thing about these >>> threads is that noobs come along regularly to begin the whole process >>> anew. It's a bore, but sometimes it's harder to let the blather stand >>> unchallenged. >>> >>> What appears to be the underlying agenda in these threads is >>> "anti-engineering", or even "anti-science". It's common for >>> engineering to clash with intuition, but some people can't accept that. >> >> eh? from where i'm sitting, the agenda seems to be "engineers" having >> a hard time coming to terms their grasp of reality. > > OK, perhaps you forgot where this started: > > I said: > > "I measured 7mm deflection with an initial 23lb, and 12mm with an > additional 26lb (49lb total). I used hung weights, so I'm sure of the > forces. I used a caliper to measure the deflections. I don't have a > tensiometer, so I don't know the initial tension, but the differential > should be reasonably accurate." > > "By the formula in Jobst's book (T=Force*length/4*displacement), I > calculated a tension of 230lb for the first load, 285 for the second. > So, the additional 26lb increased tension 55lb, or a little over 2:1." > > you replied: > "that's the problem! jobst's formula doesn't account for rim > distortion. you need to measure tension of the spoke directly. which > exactly what fogel did." > > If you understood vectors, you'd have known that "L" included rim > deflection. If you understood wheels (and vectors), you'd realize that > even not taking that into account doesn't significantly affect the outcome. condescending drivel. /you/ are the guy that "forgot" to take L into account. /you/ are the guy with the problem recognizing elasticity. as i pointed out right at the start. now of course, you're trying to gloss over all this, but hey peter, don't let little details get in the way of your method when you "measure" spoke tension. > > All you need to know to accurately measure spoke tension is the load and > the angle. > > Carl understands now, how about you? > > Ready to retract? er, /you/ are the one that needs to eat crow here buddy. your unabashed attempts to ignore the inconvenient stuff is quite ridiculous.                                   Date: 06 Jan 2007 16:10:17 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > condescending drivel. /you/ are the guy that "forgot" to take L into > account. /you/ are the guy with the problem recognizing elasticity. as > i pointed out right at the start. now of course, you're trying to gloss > over all this, but hey peter, don't let little details get in the way of > your method when you "measure" spoke tension. I didn't "forget" to take "L" into account. What you (continue to) fail to grasp is that rim deflection doesn't matter. The ratio of the force to the tension is exactly equal to the ratio of the displacement to the hypotenuse, which, in this case is "L", and doesn't change. Your response (to my complete explanation) was: "This stuff is real basic. "3. if there is no fraud, then the math model is incomplete. and half a moment's thought paying attention to the fact that we don't see rim stiffness in the equation should make anyone pause. assumption that the distance between the two ends of the wire therefore remains perfectly fixed is incorrect." "this stuff is real basic peter and it concerns me that you either don't get this stuff or are prepared to deny it." It is "real basic". Rim stiffness doesn't enter into it. Nobody is assuming "the distance between the two ends of the wire remains perfectly fixed". It doesn't matter. Everyone seems to "get this stuff" by now except you. > er, /you/ are the one that needs to eat crow here buddy. your unabashed > attempts to ignore the inconvenient stuff is quite ridiculous. Ridiculous, indeed. I think you're the one who needs to give it more than "half a moment's thought".                   Date: 04 Jan 2007 12:48:47 From: Subject: Re: I fixed a broken spoke! On Thu, 04 Jan 2007 12:32:04 -0500, dvt <dvt+usenet@psu.edu > wrote: >jim beam wrote: >> imagine this: >> [fixed width font] >> >> v >> concrete             Date: 24 Dec 2006 23:54:37 From: Ron Ruff Subject: Re: I fixed a broken spoke! jim beam wrote: > yes it does. try unanchoring one end of the wire. it can still be > deflected, but see what happens to the tension. Or... you can anchor both ends... or not... it doesn't matter. I think you are still stuck on the idea that the for a given force, the deflection (and tension) will vary a lot depending on how rigid the ends are fixed... and you are absolutely correct! If you apply a 50 lb load to spoke that has rigidly fixed ends, the tension rise will be much higher than if the ends flex a large amount... but in *both* cases you'll still be able to determine the *resulting* tension if you can measure F, L, and d! I had a block about this too at first... I even started to write Peter a post telling him he was wrong... then I went back and looked at how the equation was derived... It's just vectors and force balance. It's trickier to tell what the initial tension was though... this only gives you the tension after the load is applied.               Date: 26 Dec 2006 07:13:01 From: jim beam Subject: Re: I fixed a broken spoke! Ron Ruff wrote: > jim beam wrote: >> yes it does. try unanchoring one end of the wire. it can still be >> deflected, but see what happens to the tension. > > Or... you can anchor both ends... or not... it doesn't matter. I think > you are still stuck on the idea that the for a given force, the > deflection (and tension) will vary a lot depending on how rigid the > ends are fixed... and you are absolutely correct! If you apply a 50 lb > load to spoke that has rigidly fixed ends, the tension rise will be > much higher than if the ends flex a large amount... but in *both* cases > you'll still be able to determine the *resulting* tension if you can > measure F, L, and d! L is not constant in our case. you'd need to substitute L for a function of anchor elasticity to get a meaningful result. > > I had a block about this too at first... I even started to write Peter > a post telling him he was wrong... then I went back and looked at how > the equation was derived... It's just vectors and force balance. > > It's trickier to tell what the initial tension was though... this only > gives you the tension after the load is applied. you can't tell what initial tension is at all! but in our case, we're looking for /increase/ in tension, so that's ok. now, if only we can address the variable L...             Date: 24 Dec 2006 10:20:42 From: Ron Ruff Subject: Re: I fixed a broken spoke! jim beam wrote: > no because the math assumes the ends are fixed in space. it doesn't > explicitly state that, but it's the assumption nevertheless. Let me try to re-explain. At first I thought the same as you... it is intuitively obvious that if the end points are not rigid (they come together some amount), you'll be able to deflect the spoke farther with the same force... and this true! But at the same time it doesn't matter. The calculation of tension via T= F*L/4/d is pure trig (force balance perpendicular to the spoke) and doesn't care if the end points have moved at all. The spoke is modeled as thread with zero bending stiffness; we don't care about it's modulus or anything. You only need to know those quanities, F, L, and d fairly accurately to determine the tension in the spoke. Note that the "initial" spoke tension or conditions is not a part of this at all... we are just looking at the tension *after* the side load (F) is applied. This is a key point in understanding I think. It is true that if you have perfectly rigid endpoints a given F will result in a smaller d, and T will be higher. But the equation is not invalidated if the ends come together a little. Then d will be greater and you will calculate a smaller T. I can't say if Peter made an error in measurement or not, but his method is sound.               Date: 24 Dec 2006 16:10:20 From: jim beam Subject: Re: I fixed a broken spoke! Ron Ruff wrote: > jim beam wrote: >> no because the math assumes the ends are fixed in space. it doesn't >> explicitly state that, but it's the assumption nevertheless. > > Let me try to re-explain. At first I thought the same as you... it is > intuitively obvious that if the end points are not rigid (they come > together some amount), you'll be able to deflect the spoke farther with > the same force... and this true! But at the same time it doesn't > matter. The calculation of tension via T= F*L/4/d is pure trig (force > balance perpendicular to the spoke) and doesn't care if the end points > have moved at all. yes it does. try unanchoring one end of the wire. it can still be deflected, but see what happens to the tension. > The spoke is modeled as thread with zero bending > stiffness; we don't care about it's modulus or anything. You only need > to know those quanities, F, L, and d fairly accurately to determine the > tension in the spoke. Note that the "initial" spoke tension or > conditions is not a part of this at all... we are just looking at the > tension *after* the side load (F) is applied. This is a key point in > understanding I think. > > It is true that if you have perfectly rigid endpoints a given F will > result in a smaller d, and T will be higher. But the equation is not > invalidated if the ends come together a little. Then d will be greater > and you will calculate a smaller T. > > I can't say if Peter made an error in measurement or not, but his > method is sound. > his calculated values don't agree with measured values for exactly that reason - he didn't measure, he just calculated! and the calculation he performed did not allow for the changes in length where the end anchors are not rigid.               Date: 24 Dec 2006 17:02:48 From: Subject: Re: I fixed a broken spoke! On 24 Dec 2006 10:20:42 -0800, "Ron Ruff" <rruffrruff@yahoo.com > wrote: > >jim beam wrote: >> no because the math assumes the ends are fixed in space. it doesn't >> explicitly state that, but it's the assumption nevertheless. > >Let me try to re-explain. At first I thought the same as you... it is >intuitively obvious that if the end points are not rigid (they come >together some amount), you'll be able to deflect the spoke farther with >the same force... and this true! But at the same time it doesn't >matter. The calculation of tension via T= F*L/4/d is pure trig (force >balance perpendicular to the spoke) and doesn't care if the end points >have moved at all. The spoke is modeled as thread with zero bending >stiffness; we don't care about it's modulus or anything. You only need >to know those quanities, F, L, and d fairly accurately to determine the >tension in the spoke. Note that the "initial" spoke tension or >conditions is not a part of this at all... we are just looking at the >tension *after* the side load (F) is applied. This is a key point in >understanding I think. > >It is true that if you have perfectly rigid endpoints a given F will >result in a smaller d, and T will be higher. But the equation is not >invalidated if the ends come together a little. Then d will be greater >and you will calculate a smaller T. > >I can't say if Peter made an error in measurement or not, but his >method is sound. Dear Ron, If the method is sound in this specific situation, then it would be easy to confirm its soundness with a tension gauge. For fun, I'm going to see about hanging a weight around 200 pounds from a spoke and applying a tension gauge. I'll be very surprised if it is the 50% off suggested elsewhere. (The immediate problem is that the only handy and easily mounted ~200 weight in my basement will be busy trying to apply the tension gauge, and it's too dark and cold to try to hoist a motorycle into the air out on the car port.) As an analogy, some people are claiming that measuring the depth of two footprints in a muddy field lets them determine that whoever walked through the field and left those tracks must have weighed either 300 pounds or 1,000 pounds--the muddiness makes no difference and they scoff at the notion that the soil might vary. But everyone who actually stood on a bathroom scale at the far side of the muddy field seemed to weigh around 200 pounds. Why not step on the scale? RBT has a bad habit of debating theories in a vacuum instead of trying to test whether the actual situation involves what the theory requires. Think of the fun if I report that my Park tension gauge is wildly inaccurate! Cheers, Carl Fogel                 Date: 25 Dec 2006 12:43:09 From: Peter Cole Subject: Re: I fixed a broken spoke! carlfogel@comcast.net wrote: > For fun, I'm going to see about hanging a weight around 200 pounds > from a spoke and applying a tension gauge. I'll be very surprised if > it is the 50% off suggested elsewhere. > I'm not sure if I'm the "elsewhere", but from the numbers you posted on your wheel, I calculated 395lb, whereas you measured 340lb, I believe. That makes the my method either 16% too high, or yours 14% too low. Not huge discrepancies, 15% rather than 50%. Looking at the data you posted: <http://home.comcast.net/~carlfogel/download/newspok2.jpg >, I'm troubled by the fairly large deviations from what should be a straight-ish line (or at least a smooth curve), as well as (what looks like) a negative slope in one section. Could my measurements be off by 10%? Sure. Could yours? Perhaps. That would pretty easily bracket the difference. Given the relative crudeness of both of our setups, I'm not surprised to see a 15% disagreement.             Date: 24 Dec 2006 00:13:49 From: Ron Ruff Subject: Re: I fixed a broken spoke! carlfogel@comcast.net wrote: > Since it's easy to do, your reluctance to confirm your claim to > implausibly high tension rises by a simple direct measurement will be > the last word on the matter. I can't offer an explanation of why yours and Peter's results differ, but the way he is determining the spoke tension (*with* the load applied) truly is independant of the stiffness of the rim. It is simple trig. *If* we can assume that a spoke is as flexible as a thread (more plausible over long spans), and if we know the length, deflection, and force applied... then the tension is absolutely defined. I know it doesn't seem intuitively correct, but you can move the end points around all you want... as long as you measure L, d, and F accurately, then you *can* calculate T. This doesn't tell us what the initial tension was... only the tension with the applied load. I don't know if the Park tensiometer is any good but I picked one up from Performance when they were having their $20 off $50 with free shipping sale, and I'm having fun with it. It seems to be pretty consistent at least, if not very precise... ie a single digit on the scale can represent a 4 to 20 kg variation in tension. The force it exerts on the spoke is not that small either... considering that it takes ~3lb to squeeze the handle and a leverage ratio of ~8 to 1 gives a force of ~24lb. Supposedly their conversion table compensates for this...               Date: 28 Dec 2006 01:38:45 From: Michael Press Subject: Re: I fixed a broken spoke! In article <1166948028.987967.312030@42g2000cwt.googlegroups.com >, "Ron Ruff" <rruffrruff@yahoo.com > wrote: > I don't know if the Park tensiometer is any good but I picked one up > from Performance when they were having their $20 off $50 with free > shipping sale, and I'm having fun with it. It seems to be pretty > consistent at least, if not very precise... Consistent and precise mean much the same thing. > ie a single digit on the > scale can represent a 4 to 20 kg variation in tension. The force it > exerts on the spoke is not that small either... considering that it > takes ~3lb to squeeze the handle and a leverage ratio of ~8 to 1 gives > a force of ~24lb. Supposedly their conversion table compensates for > this... You think that it may not be as _accurate_ as the scale allows. A clock that reads the correct time within a certain bound is accurate to that bound. A clock whose oscillator measures the same interval to within a certain bound is precise to that bound. The oscillator may have little twitches & anomalies; diurnal variations; sensitivity to barometric pressure, temperature, and humidity that overall add up to little variation making the clock accurate for time telling, but poor as a frequency standard. A clock may have a very precise oscillator that does not oscillate at the design frequency, making it a poor instrument for telling time. -- Michael Press                 Date: 27 Dec 2006 19:50:49 From: Tim McNamara Subject: Re: I fixed a broken spoke! In article <rubrum-2E50C8.17384527122006@newsclstr02.news.prodigy.com >, Michael Press <rubrum@pacbell.net > wrote: > In article <1166948028.987967.312030@42g2000cwt.googlegroups.com>, > "Ron Ruff" <rruffrruff@yahoo.com> wrote: > > > I don't know if the Park tensiometer is any good but I picked one > > up from Performance when they were having their $20 off $50 with > > free shipping sale, and I'm having fun with it. It seems to be > > pretty consistent at least, if not very precise... > > Consistent and precise mean much the same thing. Hardly, and neither necessarily mean accurate.               Date: 24 Dec 2006 07:08:47 From: jim beam Subject: Re: I fixed a broken spoke! Ron Ruff wrote: > carlfogel@comcast.net wrote: >> Since it's easy to do, your reluctance to confirm your claim to >> implausibly high tension rises by a simple direct measurement will be >> the last word on the matter. > > I can't offer an explanation of why yours and Peter's results differ, > but the way he is determining the spoke tension (*with* the load > applied) truly is independant of the stiffness of the rim. It is simple > trig. *If* we can assume that a spoke is as flexible as a thread (more > plausible over long spans), and if we know the length, deflection, and > force applied... then the tension is absolutely defined. no because the math assumes the ends are fixed in space. it doesn't explicitly state that, but it's the assumption nevertheless. so peter doesn't have a result, he has a calculation which doesn't reflect reality. carl otoh has an actual repeatable consistent measurement. > I know it > doesn't seem intuitively correct, but you can move the end points > around all you want... as long as you measure L, d, and F accurately, > then you *can* calculate T. if the length of the wire remains the same, and there's deflection, then by definition, the end points have moved. and that is precisely the problem with the calculation. > > This doesn't tell us what the initial tension was... only the tension > with the applied load. > > I don't know if the Park tensiometer is any good but I picked one up > from Performance when they were having their $20 off $50 with free > shipping sale, and I'm having fun with it. It seems to be pretty > consistent at least, if not very precise... ie a single digit on the > scale can represent a 4 to 20 kg variation in tension. The force it > exerts on the spoke is not that small either... considering that it > takes ~3lb to squeeze the handle and a leverage ratio of ~8 to 1 gives > a force of ~24lb. Supposedly their conversion table compensates for > this... > don't blame the tool.                 Date: 05 Jan 2007 07:39:19 From: Joe Riel Subject: Re: I fixed a broken spoke! carlfogel@comcast.net writes: > For anyone curious, the easy equation is . . . > > tension = (weight * length) / (4 * deflection) > > . . . where length is the current distance between the two end points, > and deflection is the distance from a line drawn between them to the > bend. For practical purposes, it works as well as the precise equation > of tension = force / 2 x sine(half-the-bend-angle). They are (or should be) identical; however, you wrote the wrong sine formula. Correct is sin(a) = deflection/hypotensus where a is ----------- \ a                   Date: 05 Jan 2007 10:28:07 From: Subject: Re: I fixed a broken spoke! On Fri, 05 Jan 2007 07:39:19 -0800, Joe Riel <joer@san.rr.com > wrote: >carlfogel@comcast.net writes: > >> For anyone curious, the easy equation is . . . >> >> tension = (weight * length) / (4 * deflection) >> >> . . . where length is the current distance between the two end points, >> and deflection is the distance from a line drawn between them to the >> bend. For practical purposes, it works as well as the precise equation >> of tension = force / 2 x sine(half-the-bend-angle). > >They are (or should be) identical; however, you wrote the wrong sine >formula. Correct is > > sin(a) = deflection/hypotensus > >where a is > > > >----------- >\ a                     Date: 05 Jan 2007 12:57:57 From: Peter Cole Subject: Re: I fixed a broken spoke! carlfogel@comcast.net wrote: > So I think that Dave is right, and that Jim is mistaken. With a known > weight, we can ideally determine the tension from a picture that shows > only the vee of the rubber band--whatever supports the two ends of the > rubber band can be ignored. > > But practically, we have to be able to determine the two current > endpoints that define the current L, the weight has to be right at the > midpoint of L, the force has to act at right angles to L, and the bend > has to be an idealized point instead of the flattening curve that it > actually is. All of these effects can be analyzed -- with vectors. If the simple 3-point case is opaque to those without the necessary background, extended discussions/debates of the effects of departures from it are pointless.                 Date: 24 Dec 2006 07:49:41 From: jim beam Subject: Re: I fixed a broken spoke! jim beam wrote: > Ron Ruff wrote: >> carlfogel@comcast.net wrote: >>> Since it's easy to do, your reluctance to confirm your claim to >>> implausibly high tension rises by a simple direct measurement will be >>> the last word on the matter. >> >> I can't offer an explanation of why yours and Peter's results differ, >> but the way he is determining the spoke tension (*with* the load >> applied) truly is independant of the stiffness of the rim. It is simple >> trig. *If* we can assume that a spoke is as flexible as a thread (more >> plausible over long spans), and if we know the length, deflection, and >> force applied... then the tension is absolutely defined. > > no because the math assumes the ends are fixed in space. it doesn't > explicitly state that, but it's the assumption nevertheless. so peter > doesn't have a result, he has a calculation which doesn't reflect > reality. carl otoh has an actual repeatable consistent measurement. > >> I know it >> doesn't seem intuitively correct, but you can move the end points >> around all you want... as long as you measure L, d, and F accurately, >> then you *can* calculate T. > > if the length of the wire remains the same, and there's deflection, then > by definition, the end points have moved. on re-reading, i need to qualify that: if the length of wire remains the same, and there's deflection, then, by definition, two possible things have happened. 1. if the end points are not affixed to something perfectly rigid, then the two ends have moved closer together. 2. if the end points /are/ perfectly rigid, then the wire has become longer by elasticity, and will experience a tension rise accordingly. reality is, there is a mix of the two. there will be /some/ tension rise, but that is defined by the rigidity of the mountings. as an illustration, have two kids hold a piece of rope, then pull in the middle of the rope. how much additional tension can the kids exert? not much! therefore to accommodate the the deflection, the kids get pulled closer together. the rope experiences /some/ tension increase, but the majority of geometry change is accommodated by movement of the two anchor points. pretty basic. as is the concept that rims are far from rigid. anyone that's ever trued a wheel knows that. > and that is precisely the > problem with the calculation. > >> >> This doesn't tell us what the initial tension was... only the tension >> with the applied load. >> >> I don't know if the Park tensiometer is any good but I picked one up >> from Performance when they were having their $20 off $50 with free >> shipping sale, and I'm having fun with it. It seems to be pretty >> consistent at least, if not very precise... ie a single digit on the >> scale can represent a 4 to 20 kg variation in tension. The force it >> exerts on the spoke is not that small either... considering that it >> takes ~3lb to squeeze the handle and a leverage ratio of ~8 to 1 gives >> a force of ~24lb. Supposedly their conversion table compensates for >> this... >> > > don't blame the tool.             Date: 20 Dec 2006 16:59:12 From: Peter Cole Subject: Re: I fixed a broken spoke! carlfogel@comcast.net wrote: > After all, the most likely explanation for an occasional spoke > breaking is variation in the spoke material. The bending and > tensioning and so forth are quite regular. If squeezing spoke pairs > was solving some residual stress problem by raising tension, the same > problem would be causing all the other spokes to fail. > > I see Jobst's comment in 1993 that spokes somehow became much more > durable as strong evidence that he was mistaken about how efffective > spoke-sqeezing is. I think you're missing the point. Spoke failure is from fatigue. Fatigue life is shortened both by poor material quality and residual stress. Removing residual stress will make poor spokes and good spokes last longer. That even modern, presumably better made, spokes can benefit from stress relief is supported by the observation that spoke failures still occur. > This illustrates how easily we fool ourselves and how easy it is to > make huge mistakes. I have never doubted the good faith of the last > such calculation that appeared on RBT. A 30 pound side force moved a > spoke a certain distance and bent the spoke at such and so an angle, > which in turn allowed calculations for steel of specifc thickness to > indicate that the spoke tension would rise approximately 150 pounds, a > 5 to 1 ratio. I think you're mis-remembering that thread. Phil Holman reported measuring that 5:1 ratio on his wheel. After much posting, all concluded that little could be improved in Jobst's description in his book. The reason you found such a surprising (to yourself) ratio of 1:1 was because your rims were not very stiff. > The next thing to test was the effect of tension on residual stress. > So I cobbled together a crude vise rig and started bending spokes into > U shapes. > > A spoke bent but not stretched expands considerably when heated. > > A spoke bent and tensioned slightly in the vise will expand noticeably > less. > > A spoke bent and tensioned more will expand even less. > > A spoke bent and tensioned to normal bicycle wheel levels (~200 lbs) > will hardly expand at all. > > A spoke bent and tensioned to ~400 pounds will hardly expand at all, > just like the spoke tensioned to ~200 pounds. I had trouble following this "experiment". I assume that after tensioning the spokes had very different "starting angles" before heat was applied? It's very difficult to know exactly what was going on, specifically if the various changes in angle with heating have anything to do with residual stresses at all. > My problem with the spoke-squeezing theory is that it seems to be a > lot of theory developed to support preconceived and self-flattering > conclusions about how we can cure the King's Evil by the laying on of > hands. This method of relieving residual stress is well known and used in various industrial processes.               Date: 21 Dec 2006 05:43:53 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > carlfogel@comcast.net wrote: > >> After all, the most likely explanation for an occasional spoke >> breaking is variation in the spoke material. The bending and >> tensioning and so forth are quite regular. If squeezing spoke pairs >> was solving some residual stress problem by raising tension, the same >> problem would be causing all the other spokes to fail. >> >> I see Jobst's comment in 1993 that spokes somehow became much more >> durable as strong evidence that he was mistaken about how efffective >> spoke-sqeezing is. > > > I think you're missing the point. Spoke failure is from fatigue. Fatigue > life is shortened both by poor material quality and residual stress. > Removing residual stress will make poor spokes and good spokes last > longer. That even modern, presumably better made, spokes can benefit > from stress relief is supported by the observation that spoke failures > still occur. sure they do. and it's almost always inferior no-name spokes. one of my coworkers was breaking spokes every week earlier this year and gave me the broken ones to examine. sure enough, no-name and serious surface quality issues. all he needed was a rebuild with a quality brand spoke and his breakage issues have been eliminated. > > >> This illustrates how easily we fool ourselves and how easy it is to >> make huge mistakes. I have never doubted the good faith of the last >> such calculation that appeared on RBT. A 30 pound side force moved a >> spoke a certain distance and bent the spoke at such and so an angle, >> which in turn allowed calculations for steel of specifc thickness to >> indicate that the spoke tension would rise approximately 150 pounds, a >> 5 to 1 ratio. > > I think you're mis-remembering that thread. Phil Holman reported > measuring that 5:1 ratio on his wheel. After much posting, all concluded > that little could be improved in Jobst's description in his book. The > reason you found such a surprising (to yourself) ratio of 1:1 was > because your rims were not very stiff. > > >> The next thing to test was the effect of tension on residual stress. > > >> So I cobbled together a crude vise rig and started bending spokes into >> U shapes. >> >> A spoke bent but not stretched expands considerably when heated. >> >> A spoke bent and tensioned slightly in the vise will expand noticeably >> less. >> >> A spoke bent and tensioned more will expand even less. >> >> A spoke bent and tensioned to normal bicycle wheel levels (~200 lbs) >> will hardly expand at all. >> >> A spoke bent and tensioned to ~400 pounds will hardly expand at all, >> just like the spoke tensioned to ~200 pounds. > > I had trouble following this "experiment". I assume that after > tensioning the spokes had very different "starting angles" before heat > was applied? It's very difficult to know exactly what was going on, > specifically if the various changes in angle with heating have anything > to do with residual stresses at all. absolutely they do! that's why frames need to be re-set after heat treatment for example. > > >> My problem with the spoke-squeezing theory is that it seems to be a >> lot of theory developed to support preconceived and self-flattering >> conclusions about how we can cure the King's Evil by the laying on of >> hands. > > This method of relieving residual stress is well known and used in > various industrial processes. indeed. but with a quality material without residual stress, it's pointless and can initiate fatigue, not eliminate it. when's the last time you saw a bridge being "stress relieved"?                 Date: 21 Dec 2006 11:08:21 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > Peter Cole wrote: >> I think you're missing the point. Spoke failure is from fatigue. >> Fatigue life is shortened both by poor material quality and residual >> stress. Removing residual stress will make poor spokes and good spokes >> last longer. That even modern, presumably better made, spokes can >> benefit from stress relief is supported by the observation that spoke >> failures still occur. > > sure they do. and it's almost always inferior no-name spokes. one > of my coworkers was breaking spokes every week earlier this year and > gave me the broken ones to examine. sure enough, no-name and serious > surface quality issues. all he needed was a rebuild with a quality > brand spoke and his breakage issues have been eliminated. I have had a few DT spokes fail (at elbows) before I began stress relieving, none since. >> I had trouble following this "experiment". I assume that after >> tensioning the spokes had very different "starting angles" before heat >> was applied? It's very difficult to know exactly what was going on, >> specifically if the various changes in angle with heating have >> anything to do with residual stresses at all. > > absolutely they do! that's why frames need to be re-set after heat > treatment for example. Carl didn't "heat treat". Thermal warping has many causes. If even the direction (never mind the magnitude) revealed residual stresses, why did carbon steel spokes bend the other way? >> This method of relieving residual stress is well known and used in >> various industrial processes. > > indeed. but with a quality material without residual stress, it's > pointless and can initiate fatigue, not eliminate it. You assume that spokes are delivered w/o residual stresses and that none are introduced in wheel building. The only way the first could be true is if the manufacturer annealed the spokes -- I have seen no claims of this -- you? If, after unlacing a tensioned wheel, spoke elbow angles are no longer equal, there must be residual stresses introduced. > when's the last > time you saw a bridge being "stress relieved"? Perhaps not bridges, but I posted a link to an overload stress relief procedure required by the Coast Guard for large pressure tanks. At least some companies ket equipment for vibrational stress relief of large structures. The principle is the same. I don't know what parts of a bridge you think might need stress relief, but for known problems like welds, mitigation is done.                   Date: 21 Dec 2006 10:53:59 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > jim beam wrote: >> Peter Cole wrote: > >>> I think you're missing the point. Spoke failure is from fatigue. >>> Fatigue life is shortened both by poor material quality and residual >>> stress. Removing residual stress will make poor spokes and good >>> spokes last longer. That even modern, presumably better made, spokes >>> can benefit from stress relief is supported by the observation that >>> spoke failures still occur. >> >> sure they do. and it's almost always inferior no-name spokes. one >> of my coworkers was breaking spokes every week earlier this year and >> gave me the broken ones to examine. sure enough, no-name and serious >> surface quality issues. all he needed was a rebuild with a quality >> brand spoke and his breakage issues have been eliminated. > > I have had a few DT spokes fail (at elbows) before I began stress > relieving, none since. were they from the famous "long shank" era? they broke rapidly because of geometry issues. > >>> I had trouble following this "experiment". I assume that after >>> tensioning the spokes had very different "starting angles" before >>> heat was applied? It's very difficult to know exactly what was going >>> on, specifically if the various changes in angle with heating have >>> anything to do with residual stresses at all. >> >> absolutely they do! that's why frames need to be re-set after heat >> treatment for example. > > Carl didn't "heat treat". no. but he demonstrated the effect of residual stress. > Thermal warping has many causes. not many at those temperatures and that quickly. #1 candidate is thermal stress relief. nothing else is close. > If even the > direction (never mind the magnitude) revealed residual stresses, why did > carbon steel spokes bend the other way? it's undergoing a phase change at the same time. austenitic stainless is not. > > >>> This method of relieving residual stress is well known and used in >>> various industrial processes. >> >> indeed. but with a quality material without residual stress, it's >> pointless and can initiate fatigue, not eliminate it. > > You assume that spokes are delivered w/o residual stresses and that none > are introduced in wheel building. The only way the first could be true > is if the manufacturer annealed the spokes -- I have seen no claims of > this -- you? with respect, the years of argument on this topic have all been concerned with the efficacy of mechanical stress relief. why then eliminate it and say that only thermal is possible? > If, after unlacing a tensioned wheel, spoke elbow angles > are no longer equal, there must be residual stresses introduced. fogel has demonstrated that mechanical relief occurs are low levels. mere bending is not evidence of residual stress. > > > when's the last > > time you saw a bridge being "stress relieved"? > > Perhaps not bridges, but I posted a link to an overload stress relief > procedure required by the Coast Guard for large pressure tanks. and like i told you, i do not accept that explanation. every fracture mechanics student will tell you that that procedure is done to reveal crack flaws. there is no evidence that it performs mechanical relief, and that's not the true objective. i can only assume that piece was written by a well intentioned but mistaken intern. > At least > some companies ket equipment for vibrational stress relief of large > structures. indeed. and they precipitate yielding. but weren[t you just arguing that stress relief has to be thermal? > The principle is the same. I don't know what parts of a > bridge you think might need stress relief, but for known problems like > welds, mitigation is done. yes, it's thermal. elevated temperature allows hydrogen to diffuse out before welds crack.                     Date: 21 Dec 2006 15:37:07 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > Peter Cole wrote: >> I have had a few DT spokes fail (at elbows) before I began stress >> relieving, none since. > > were they from the famous "long shank" era? they broke rapidly because > of geometry issues. I don't think so. >> Thermal warping has many causes. > > not many at those temperatures and that quickly. #1 candidate is > thermal stress relief. nothing else is close. I don't think thermal "opening up" of bends proportional to the degree of bend is a slam-dunk demonstration of residual stresses. >> If even the direction (never mind the magnitude) revealed residual >> stresses, why did carbon steel spokes bend the other way? > > it's undergoing a phase change at the same time. austenitic stainless > is not. You're guessing. >> You assume that spokes are delivered w/o residual stresses and that >> none are introduced in wheel building. The only way the first could be >> true is if the manufacturer annealed the spokes -- I have seen no >> claims of this -- you? > > with respect, the years of argument on this topic have all been > concerned with the efficacy of mechanical stress relief. why then > eliminate it and say that only thermal is possible? With equal respect, why should DT, or any other, mess about with mechanical stress relief in formed parts when annealing would be so much easier? On the other hand, annealing a built wheel presents some thorny issues. I thought those arguments were obvious. >> If, after unlacing a tensioned wheel, spoke elbow angles are no longer >> equal, there must be residual stresses introduced. > > fogel has demonstrated that mechanical relief occurs are low levels. > mere bending is not evidence of residual stress. I think he showed thermal deformation, the cause of which is unclear. >> > when's the last >> > time you saw a bridge being "stress relieved"? >> >> Perhaps not bridges, but I posted a link to an overload stress relief >> procedure required by the Coast Guard for large pressure tanks. > > and like i told you, i do not accept that explanation. every fracture > mechanics student will tell you that that procedure is done to reveal > crack flaws. there is no evidence that it performs mechanical relief, > and that's not the true objective. i can only assume that piece was > written by a well intentioned but mistaken intern. Sure, if you say so. > >> At least some companies ket equipment for vibrational stress relief >> of large structures. > > indeed. and they precipitate yielding. but weren[t you just arguing > that stress relief has to be thermal? No, just that it's the easier way sometimes. >> The principle is the same. I don't know what parts of a bridge you >> think might need stress relief, but for known problems like welds, >> mitigation is done. > > yes, it's thermal. elevated temperature allows hydrogen to diffuse out > before welds crack. So bridges are stress relieved?                       Date: 21 Dec 2006 12:50:01 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > jim beam wrote: >> Peter Cole wrote: > >>> I have had a few DT spokes fail (at elbows) before I began stress >>> relieving, none since. >> >> were they from the famous "long shank" era? they broke rapidly >> because of geometry issues. > > I don't think so. > > >>> Thermal warping has many causes. >> >> not many at those temperatures and that quickly. #1 candidate is >> thermal stress relief. nothing else is close. > > I don't think thermal "opening up" of bends proportional to the degree > of bend is a slam-dunk demonstration of residual stresses. i'm not saying it quantifies because it doesn't, but it reliably demonstrates. > > >>> If even the direction (never mind the magnitude) revealed residual >>> stresses, why did carbon steel spokes bend the other way? >> >> it's undergoing a phase change at the same time. austenitic stainless >> is not. > > You're guessing. it's definitely undergoing phase change. the "guess" is whether it explains the difference, but it's an educated guess based on facts i know, not stuff i've made up. can you explain better? > >>> You assume that spokes are delivered w/o residual stresses and that >>> none are introduced in wheel building. The only way the first could >>> be true is if the manufacturer annealed the spokes -- I have seen no >>> claims of this -- you? >> >> with respect, the years of argument on this topic have all been >> concerned with the efficacy of mechanical stress relief. why then >> eliminate it and say that only thermal is possible? > > With equal respect, why should DT, or any other, mess about with > mechanical stress relief in formed parts when annealing would be so much > easier? because it will soften the steel! spoke steel is worked to ~1000N/mm^2 yield. annealed, i doubt it would be 400N/mm^2. > On the other hand, annealing a built wheel presents some thorny > issues. I thought those arguments were obvious. apparently not. > >>> If, after unlacing a tensioned wheel, spoke elbow angles are no >>> longer equal, there must be residual stresses introduced. >> >> fogel has demonstrated that mechanical relief occurs are low levels. >> mere bending is not evidence of residual stress. > > I think he showed thermal deformation, the cause of which is unclear. there is no impetus to deform other than that caused by [internal] residual stress. unless he fabricated results of course. but i doubt that since his results are consistent with materials theory. > >>> > when's the last >>> > time you saw a bridge being "stress relieved"? >>> >>> Perhaps not bridges, but I posted a link to an overload stress relief >>> procedure required by the Coast Guard for large pressure tanks. >> >> and like i told you, i do not accept that explanation. every fracture >> mechanics student will tell you that that procedure is done to reveal >> crack flaws. there is no evidence that it performs mechanical relief, >> and that's not the true objective. i can only assume that piece was >> written by a well intentioned but mistaken intern. > > Sure, if you say so. > >> >>> At least some companies ket equipment for vibrational stress >>> relief of large structures. >> >> indeed. and they precipitate yielding. but weren[t you just arguing >> that stress relief has to be thermal? > > No, just that it's the easier way sometimes. depends on application. you /don't/ want to thermally stress relieve cold drawn wire unless you want to soften it too. > > >>> The principle is the same. I don't know what parts of a bridge you >>> think might need stress relief, but for known problems like welds, >>> mitigation is done. >> >> yes, it's thermal. elevated temperature allows hydrogen to diffuse >> out before welds crack. > > So bridges are stress relieved? no - temperature is insufficient for that. usually they're pre-heated to a few hundred degrees to minimize stress gradient on weld pool solidification and retro-heated to allow hydrogen to diffuse out. you can argue that hydrogen presence causes internal stress, but it's not the result of weld pool phase change or contraction.                         Date: 22 Dec 2006 08:40:42 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > Peter Cole wrote: >> jim beam wrote: >>> Peter Cole wrote: >>>> If even the direction (never mind the magnitude) revealed residual >>>> stresses, why did carbon steel spokes bend the other way? >>> >>> it's undergoing a phase change at the same time. austenitic >>> stainless is not. >> >> You're guessing. > > it's definitely undergoing phase change. the "guess" is whether it > explains the difference, but it's an educated guess based on facts i > know, not stuff i've made up. can you explain better? No, I can't explain it, and neither can you. > > depends on application. you /don't/ want to thermally stress relieve > cold drawn wire unless you want to soften it too. > <http://www.hghouston.com/ss_heat.html > "Stainless steels may be stress relieved. There are several stress relief treatments. Guidelines follow. Stress redistribution at 290 to 425C (550 to 800F), which is below the sensitization range. When stainless steel sheet and bar are cold reduced greater than about 30% and subsequently heated to 290 - 425C (550 - 800F), there is a significant redistribution of peak stresses and an increase in both tensile and yield strength. Stress redistribution heat treatments at 290 - 425C (550 - 800F) will reduce movement in later machining operations and are occasionally used to increase strength. Since stress redistribution treatments are made at temperatures below 425C (800F), carbide precipitation and sensitization to intergranular attack (IGA) are not a problem for the higher carbon grades. "                           Date: 22 Dec 2006 07:21:33 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > jim beam wrote: >> Peter Cole wrote: >>> jim beam wrote: >>>> Peter Cole wrote: > >>>>> If even the direction (never mind the magnitude) revealed residual >>>>> stresses, why did carbon steel spokes bend the other way? >>>> >>>> it's undergoing a phase change at the same time. austenitic >>>> stainless is not. >>> >>> You're guessing. >> >> it's definitely undergoing phase change. the "guess" is whether it >> explains the difference, but it's an educated guess based on facts i >> know, not stuff i've made up. can you explain better? > > No, I can't explain it, and neither can you. > > >> >> depends on application. you /don't/ want to thermally stress relieve >> cold drawn wire unless you want to soften it too. >> > > <http://www.hghouston.com/ss_heat.html> > > "Stainless steels may be stress relieved. There are several stress > relief treatments. Guidelines follow. > > Stress redistribution at 290 to 425C (550 to 800F), which is below the > sensitization range. > > When stainless steel sheet and bar are cold reduced greater than about > 30% and subsequently heated to 290 - 425C (550 - 800F), there is a > significant redistribution of peak stresses and an increase in both > tensile and yield strength. Stress redistribution heat treatments at 290 > - 425C (550 - 800F) will reduce movement in later machining operations > and are occasionally used to increase strength. Since stress > redistribution treatments are made at temperatures below 425C (800F), > carbide precipitation and sensitization to intergranular attack (IGA) > are not a problem for the higher carbon grades. " but you're caught between the devil and the deep blue sea - you don't want to soften the material either, so what do you do? real world fatigue failures suggest that residual stress is not the prime suspect - so why waste resources chasing after something that's not going to affect fatigue life?               Date: 20 Dec 2006 15:28:40 From: Subject: Re: I fixed a broken spoke! On Wed, 20 Dec 2006 16:59:12 -0500, Peter Cole <peter_cole@comcast.net > wrote: [snip] >I think you're mis-remembering that thread. Phil Holman reported >measuring that 5:1 ratio on his wheel. After much posting, all concluded >that little could be improved in Jobst's description in his book. The >reason you found such a surprising (to yourself) ratio of 1:1 was >because your rims were not very stiff. [snip] Dear Peter, No, I tested various wheels, including a box-section Mavic MA3, and found the same results. You must have missed those details. Apparently, you also missed my more recent test, in which I hung weights on a horizontal spoke tensioned in a massive pipe-clamp rig, far stiffer than any bicycle wheel: http://groups.google.com/group/rec.bicycles.tech/msg/bce241a75595fbed A 60-pound weight produced only a 90-pound tension rise when hung from the middle of horizontal spoke whose original tension was 235 pounds. Of course, no bicycle rim will ever approach the stiffness of a pair of steel clamps on a 3/4" steel pipe whose walls are thicker than the spoke itself. Again, the impressive bend angles seen when pairs of bicycle spokes are squeezed are not signs of huge tension increases. The bends are the result of the slack gained when the rim distorts into a faint N or Z shape and the slack gained when the squeezed spoke presses down against the unsqueezed spoke in a 3-cross patter. Feel free to do some actual testing instead of just asserting that stiffer rims will produce the results that you want. The pipe clamp cost eight bucks, the spoke was about fifty cents. A tension gauge costs about $50, but no one really interested in this kind of thing can consider that a barrier. Cheers, Carl Fogel                 Date: 21 Dec 2006 08:33:50 From: Peter Cole Subject: Re: I fixed a broken spoke! carlfogel@comcast.net wrote: > On Wed, 20 Dec 2006 16:59:12 -0500, Peter Cole > <peter_cole@comcast.net> wrote: > > [snip] > >> I think you're mis-remembering that thread. Phil Holman reported >> measuring that 5:1 ratio on his wheel. After much posting, all concluded >> that little could be improved in Jobst's description in his book. The >> reason you found such a surprising (to yourself) ratio of 1:1 was >> because your rims were not very stiff. > > [snip] > > Dear Peter, > > No, I tested various wheels, including a box-section Mavic MA3, and > found the same results. You must have missed those details. You apparently assume the MA3 is a stiff rim. A box section does not improve stiffness, as it adds material in the neutral plane (something Jobst has pointed out before). Rim stiffness is pretty much a function of cross section height. > Apparently, you also missed my more recent test, in which I hung > weights on a horizontal spoke tensioned in a massive pipe-clamp rig, > far stiffer than any bicycle wheel: > > http://groups.google.com/group/rec.bicycles.tech/msg/bce241a75595fbed > > A 60-pound weight produced only a 90-pound tension rise when hung from > the middle of horizontal spoke whose original tension was 235 pounds. > > Of course, no bicycle rim will ever approach the stiffness of a pair > of steel clamps on a 3/4" steel pipe whose walls are thicker than the > spoke itself. How can you be sure of the stiffness of your fixture without measuring it? How can you be sure that your spoke mounting/support exactly replicates a hub and rim? There are many ways for errors to creep in. > Again, the impressive bend angles seen when pairs of bicycle spokes > are squeezed are not signs of huge tension increases. The bends are > the result of the slack gained when the rim distorts into a faint N or > Z shape and the slack gained when the squeezed spoke presses down > against the unsqueezed spoke in a 3-cross patter. As said so many times before, the spoke angle only reveals the ratio of forces. To say you get low ratios and large angles is just repeating yourself. The real question is why the angles are large. This can only be from something in the path that is less stiff than the spoke itself. Likely candidates are the rim and the spoke path/end support. You generalize from your measurements on your wheels to predict that all of us get less tension increases than you, despite at least one report to the contrary. This is, of course, a tempest in a teapot, since it makes little difference what the precise amount of spoke overload is as long as it falls within the rough bounds of being enough to improve the residual stresses but not so much as to damage the rim. > Feel free to do some actual testing instead of just asserting that > stiffer rims will produce the results that you want. I would be perfectly happy with 60 lbf that your worst case tests seem to predict.                   Date: 21 Dec 2006 18:35:10 From: Subject: Re: I fixed a broken spoke! On Thu, 21 Dec 2006 08:33:50 -0500, Peter Cole <peter_cole@comcast.net > wrote: [snip] Dear Peter, Feel free to ship me a spoked bicycle wheel that you think is stiffer than a 3/4" steel pipe clamp. You pay to ship it, I'll pay to ship it back after testing. If you're just as happy with a mistaken claim that a 30-pound squeeze will raise a spoke 150 pounds from 250 to 400 pounds of tension as you are with test results showing that a 60-pound squeeze (twice as much squeeze force) will raise the same spoke only 55~65 pounds (less than half), then your theory is rekably elastic. Cheers, Carl Fogel 309 Grace Pueblo, CO 81004                     Date: 30 Dec 2006 13:21:32 From: Andrew W Subject: Re: I fixed a broken spoke! Ron Ruff wrote: <cut > > > About the Park gauge... I was quite surprised to discover that the DS > spokes on my rear wheel were tensioned to 175kg! Yikes! Yes, I did that > myself. I knew it was high tension, but I had no idea it was that high. > It wasn't difficult to achieve even with a very cheap spoke wrench... > maybe the grease on the nipples helped. > > Then I noticed that every other spoke hole was cracked... oh well, that > rim was dented anyway... I have just bought a Park tensiometer as I had a rim crack (possibly due to overtensioning when I built the wheel originally), and, when replacing it, broke three spokes that went off like a machine gun, first the one I was tightening, then those next to it, breaking at about 2/3 of the way along. Obviously the tension in this wheel was too high. But, like you, I was surprised at just how high a tension my wheels had when measured. All that I have read seems to imply that, before you snap spokes either the wheel will "taco", or the nipples will become very hard to turn. Indeed "the bicycle wheel" p105 suggests finding the highest tension the rim will support by determining the tesnion at which it "tacos" when stress relieved. My experience shows that spokes may well break before that tension is reached. This was for a "standard" 36 spoke, socketed rim (Rigida Sputnik). The same page also says (referring to deep section rims) that "the tension of 36 spokes may not exceed the tension or the rim...tensioning is usually at the limit when the nipples can no longer be tightened easily". In my case the nipples still turned freely and the rim remianed true until the spokes went ping. This suggests to me that, contrary to what I had expected, spokes can be the weakest link in a wheel. My experience backs yours up. It can be surprisingly easy to reach tensions that may caus rim cracking and spoke breakage. With the aid of my newly acquired tensiometer I have rebuilt with butted spokes and stopped tensioning at 150Kg force on the drive side. If, as this thread suggests, the tool is a reliable guide, then theis should be plenty. Andrew Webster                     Date: 25 Dec 2006 01:21:14 From: Chalo Subject: Re: I fixed a broken spoke! carlfogel@comcast.net wrote: > > As an analogy, some people are claiming that measuring the depth of > two footprints in a muddy field lets them determine that whoever > walked through the field and left those tracks must have weighed > either 300 pounds or 1,000 pounds--the muddiness makes no difference > and they scoff at the notion that the soil might vary. Why are you singling me out for this example, Carl? Chalo                       Date: 25 Dec 2006 11:42:38 From: Subject: Re: I fixed a broken spoke! On 25 Dec 2006 01:21:14 -0800, "Chalo" <chalo.colina@gmail.com > wrote: > >carlfogel@comcast.net wrote: >> >> As an analogy, some people are claiming that measuring the depth of >> two footprints in a muddy field lets them determine that whoever >> walked through the field and left those tracks must have weighed >> either 300 pounds or 1,000 pounds--the muddiness makes no difference >> and they scoff at the notion that the soil might vary. > >Why are you singling me out for this example, Carl? > >Chalo Dear Chalo, A) You live in Seattle in the Pacific Northwest. B) It's often damp and drizzly there, so the fields are muddy. C) http://www.isu.edu/~meldd/fxnlmorph.html D) If the shoe fits . . . Tactfully, Carl Fogel                     Date: 25 Dec 2006 00:25:38 From: Ron Ruff Subject: Re: I fixed a broken spoke! carlfogel@comcast.net wrote: > For fun, I'm going to see about hanging a weight around 200 pounds > from a spoke and applying a tension gauge. I'll be very surprised if > it is the 50% off suggested elsewhere. > > (The immediate problem is that the only handy and easily mounted ~200 > weight in my basement will be busy trying to apply the tension gauge, > and it's too dark and cold to try to hoist a motorycle into the air > out on the car port.) I had the same idea for an obvious way to test a tensiometer... but since hoisting 200 lb objects is cumbersome, I thought it might be better to use leverage... provided that you have some strong tubing or angle laying around. I envy your ability to even do these experiments. My "shop" is in the dining room so it limits what I can do (my wife is tolerant, but...). It's better than Hawaii though... there my shop was at the foot of the bed! I've just moved to NM with essentially nothing, so I don't have many tools or any extra bits and pieces laying around. I'm still reeling from the cost and effort of putting a household together from scratch... even buying everything second hand or building it. Someday though, I hope to join you in experimenting. About the Park gauge... I was quite surprised to discover that the DS spokes on my rear wheel were tensioned to 175kg! Yikes! Yes, I did that myself. I knew it was high tension, but I had no idea it was that high. It wasn't difficult to achieve even with a very cheap spoke wrench... maybe the grease on the nipples helped. Then I noticed that every other spoke hole was cracked... oh well, that rim was dented anyway...                     Date: 22 Dec 2006 09:14:05 From: Peter Cole Subject: Re: I fixed a broken spoke! carlfogel@comcast.net wrote: > On Thu, 21 Dec 2006 08:33:50 -0500, Peter Cole > <peter_cole@comcast.net> wrote: > > [snip] > > Dear Peter, > > Feel free to ship me a spoked bicycle wheel that you think is stiffer > than a 3/4" steel pipe clamp. Again, how stiff is your clamp? Remember, the overall stiffness is not the stiffness of the pipe, as you claim, but the complete path, including the end supports. If the spoke is not well supported at the elbow and nipple your results could be way off. An aluminum hub flange has the advantage of being soft enough to conform to the spoke bend radius at the elbow, unless your fixture is carefully replicating this you're only measuring elbow flex. > If you're just as happy with a mistaken claim that a 30-pound squeeze > will raise a spoke 150 pounds from 250 to 400 pounds of tension How do you know this was mistaken? It's easy to see how less-than-ideal conditions could show low ratios of force to tension, it's much harder to see how they could show (inaccurately) high ones. > as you > are with test results showing that a 60-pound squeeze (twice as much > squeeze force) will raise the same spoke only 55~65 pounds (less than > half), then your theory is rekably elastic. I wouldn't claim stress relief ineffective if I could only get 60 lb increase in tension, whether it be from weak hands or weak rims.                       Date: 30 Dec 2006 01:27:03 From: Tom Keats Subject: Re: I fixed a broken spoke! In article <rubrum-A2E213.21142229122006@newsclstr02.news.prodigy.com >, Michael Press <rubrum@pacbell.net > writes: > In article > <bg77p2t8hqj8tcptvjkigmbe4r1n2tppg4@4ax.com>, > jtaylor@NOSPAM.hfx.andara.com wrote: > >> On 28 Dec 2006 00:09:19 -0800, "Ron Ruff" <rruffrruff@yahoo.com> >> wrote: >> >> > >> >Michael Press wrote: >> >> >> >> Consistent and precise mean much the same thing. >> > >> >I think I understand your point. If the device was very consistent, >> >then it would be very precise... >> >> No. >> >> Accuracy, precision, and consistency are _different_ things. > > What is consistency in a laboratory? > > Precision is getting the same value each time you > measure the same thing. That sounds to me more like a definition of consistency. Precision, as I learned about it, has to do with "degrees of accuracy," taking into consideration such things as the effects of multiplication and division on error, significant digits, rounding, and irrational numbers. Precision doesn't need to be any finer than the practical demands of what it's applied to, so precision is relative and arbitrary. "False precision" (e.g: use of insignificant digits) is a waste of time and effort. cheers, Tom -- Nothing is safe from me. Above address is just a spam midden. I'm really at: tkeats curlicue vcn dot bc dot ca                         Date: 31 Dec 2006 00:11:26 From: Michael Press Subject: Re: I fixed a broken spoke! In article <7db5ne.k87.ln@bud.garden.local >, tkeats2005@hotmail.com (Tom Keats) wrote: > In article <rubrum-A2E213.21142229122006@newsclstr02.news.prodigy.com>, > Michael Press <rubrum@pacbell.net> writes: > > In article > > <bg77p2t8hqj8tcptvjkigmbe4r1n2tppg4@4ax.com>, > > jtaylor@NOSPAM.hfx.andara.com wrote: > > > >> On 28 Dec 2006 00:09:19 -0800, "Ron Ruff" <rruffrruff@yahoo.com> > >> wrote: > >> > >> > > >> >Michael Press wrote: > >> >> > >> >> Consistent and precise mean much the same thing. > >> > > >> >I think I understand your point. If the device was very consistent, > >> >then it would be very precise... > >> > >> No. > >> > >> Accuracy, precision, and consistency are _different_ things. > > > > What is consistency in a laboratory? > > > > Precision is getting the same value each time you > > measure the same thing. > > That sounds to me more like a definition of consistency. > > Precision, as I learned about it, has to do with "degrees > of accuracy," taking into consideration such things as > the effects of multiplication and division on error, > significant digits, rounding, and irrational numbers. > > Precision doesn't need to be any finer than the practical > demands of what it's applied to, so precision is relative > and arbitrary. "False precision" (e.g: use of insignificant > digits) is a waste of time and effort. Consistency is not a technical term in laboratory technique. Search the web on the conjunction of the words {accuracy, precision, laboratory}. First hit. <http://scidiv.bcc.ctc.edu/Physics/Measure&sigfigs/B-Acc-Prec-Unc.html > -- Michael Press                       Date: 22 Dec 2006 11:44:38 From: Subject: Re: I fixed a broken spoke! On Fri, 22 Dec 2006 09:14:05 -0500, Peter Cole <peter_cole@comcast.net > wrote: >carlfogel@comcast.net wrote: >> On Thu, 21 Dec 2006 08:33:50 -0500, Peter Cole >> <peter_cole@comcast.net> wrote: >> >> [snip] >> >> Dear Peter, >> >> Feel free to ship me a spoked bicycle wheel that you think is stiffer >> than a 3/4" steel pipe clamp. > >Again, how stiff is your clamp? Remember, the overall stiffness is not >the stiffness of the pipe, as you claim, but the complete path, >including the end supports. If the spoke is not well supported at the >elbow and nipple your results could be way off. An aluminum hub flange >has the advantage of being soft enough to conform to the spoke bend >radius at the elbow, unless your fixture is carefully replicating this >you're only measuring elbow flex. > >> If you're just as happy with a mistaken claim that a 30-pound squeeze >> will raise a spoke 150 pounds from 250 to 400 pounds of tension > >How do you know this was mistaken? > >It's easy to see how less-than-ideal conditions could show low ratios of >force to tension, it's much harder to see how they could show >(inaccurately) high ones. > > >> as you >> are with test results showing that a 60-pound squeeze (twice as much >> squeeze force) will raise the same spoke only 55~65 pounds (less than >> half), then your theory is rekably elastic. > >I wouldn't claim stress relief ineffective if I could only get 60 lb >increase in tension, whether it be from weak hands or weak rims. Dear Peter, This isn't a difficult question to resolve. I say that a 60 pound squeeze force will raise ordinary spoke tension about 55~65 pounds because I've tested various wheels and found a roughly 1-to-1 ratio. You seem to be claiming that some unnamed wheel that you haven't tested should see a much larger tension increase, up to a 5-to-1 ratio. If you want to test a wheel yourself, mount the wheel upright over the end of a workbench, support one horizontal spoke with a ceiling rope, and hang 60 pounds of weights on a rope from the spoke above it. Squeeze the spoke pair on the other side of the wheel with a clamp or your hand to a similar bend angle. A Park tension gauge will show the original and increased tension. No great accuracy is needed--the 5-to-1 tension increase that you seem to expect would be well past the calibrated range of a Park gauge. Feel free to mail me a wheel that you think is stiffer than a 3/4" steel pipe clamp for spoke-squeezing. I'll be happy to test it. Wheels are light and cheap to ship, so I'll pay to ship it back to you. Cheers, Carl Fogel 309 Grace Pueblo, CO 81008                         Date: 23 Dec 2006 11:16:54 From: Peter Cole Subject: Re: I fixed a broken spoke! carlfogel@comcast.net wrote: > On Fri, 22 Dec 2006 09:14:05 -0500, Peter Cole > <peter_cole@comcast.net> wrote: > >> carlfogel@comcast.net wrote: >>> On Thu, 21 Dec 2006 08:33:50 -0500, Peter Cole >>> <peter_cole@comcast.net> wrote: >>> >>> [snip] >>> >>> Dear Peter, >>> >>> Feel free to ship me a spoked bicycle wheel that you think is stiffer >>> than a 3/4" steel pipe clamp. >> Again, how stiff is your clamp? Remember, the overall stiffness is not >> the stiffness of the pipe, as you claim, but the complete path, >> including the end supports. If the spoke is not well supported at the >> elbow and nipple your results could be way off. An aluminum hub flange >> has the advantage of being soft enough to conform to the spoke bend >> radius at the elbow, unless your fixture is carefully replicating this >> you're only measuring elbow flex. >> >>> If you're just as happy with a mistaken claim that a 30-pound squeeze >>> will raise a spoke 150 pounds from 250 to 400 pounds of tension >> How do you know this was mistaken? >> >> It's easy to see how less-than-ideal conditions could show low ratios of >> force to tension, it's much harder to see how they could show >> (inaccurately) high ones. >> >> >>> as you >>> are with test results showing that a 60-pound squeeze (twice as much >>> squeeze force) will raise the same spoke only 55~65 pounds (less than >>> half), then your theory is rekably elastic. >> I wouldn't claim stress relief ineffective if I could only get 60 lb >> increase in tension, whether it be from weak hands or weak rims. > > Dear Peter, > > This isn't a difficult question to resolve. > > I say that a 60 pound squeeze force will raise ordinary spoke tension > about 55~65 pounds because I've tested various wheels and found a > roughly 1-to-1 ratio. > > You seem to be claiming that some unnamed wheel that you haven't > tested should see a much larger tension increase, up to a 5-to-1 > ratio. To be clear, I'm just quoting what Phil Holman reported with his wheel. > If you want to test a wheel yourself, mount the wheel upright over the > end of a workbench, support one horizontal spoke with a ceiling rope, > and hang 60 pounds of weights on a rope from the spoke above it. > Squeeze the spoke pair on the other side of the wheel with a clamp or > your hand to a similar bend angle. > > A Park tension gauge will show the original and increased tension. No > great accuracy is needed--the 5-to-1 tension increase that you seem to > expect would be well past the calibrated range of a Park gauge. > > Feel free to mail me a wheel that you think is stiffer than a 3/4" > steel pipe clamp for spoke-squeezing. I'll be happy to test it. Wheels > are light and cheap to ship, so I'll pay to ship it back to you. OK, I had some time this morning. I took an old (rear) wheel I have -- Mavic Reflex, 36 hole, rear, 2mm spokes. I measured 7mm deflection with an initial 23lb, and 12mm with an additional 26lb (49lb total). I used hung weights, so I'm sure of the forces. I used a caliper to measure the deflections. I don't have a tensiometer, so I don't know the initial tension, but the differential should be reasonably accurate. By the formula in Jobst's book (T=Force*length/4*displacement), I calculated a tension of 230lb for the first load, 285 for the second. So, the additional 26lb increased tension 55lb, or a little over 2:1. This was about what I expected, a hard (50-60lb) squeeze will give me the nominal 50% over-tension I want in stress relieving. I didn't expect 5:1, that's just what Phil H reported. My rims aren't as stiff, so that would explain at least some of the difference. Parenthetically, this also suggests my wheel was a little under-tensioned, something I don't doubt, since as I recall, this rim replaced an identical prior rim that cracked at the spoke holes (both anodized), so I think I took the tension only as far as I needed to without the spokes unscrewing when ridden.                           Date: 23 Dec 2006 11:11:02 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > carlfogel@comcast.net wrote: >> On Fri, 22 Dec 2006 09:14:05 -0500, Peter Cole >> <peter_cole@comcast.net> wrote: >> >>> carlfogel@comcast.net wrote: >>>> On Thu, 21 Dec 2006 08:33:50 -0500, Peter Cole >>>> <peter_cole@comcast.net> wrote: >>>> >>>> [snip] >>>> >>>> Dear Peter, >>>> >>>> Feel free to ship me a spoked bicycle wheel that you think is stiffer >>>> than a 3/4" steel pipe clamp. >>> Again, how stiff is your clamp? Remember, the overall stiffness is >>> not the stiffness of the pipe, as you claim, but the complete path, >>> including the end supports. If the spoke is not well supported at the >>> elbow and nipple your results could be way off. An aluminum hub >>> flange has the advantage of being soft enough to conform to the spoke >>> bend radius at the elbow, unless your fixture is carefully >>> replicating this you're only measuring elbow flex. >>> >>>> If you're just as happy with a mistaken claim that a 30-pound squeeze >>>> will raise a spoke 150 pounds from 250 to 400 pounds of tension >>> How do you know this was mistaken? >>> >>> It's easy to see how less-than-ideal conditions could show low ratios >>> of force to tension, it's much harder to see how they could show >>> (inaccurately) high ones. >>> >>> >>>> as you >>>> are with test results showing that a 60-pound squeeze (twice as much >>>> squeeze force) will raise the same spoke only 55~65 pounds (less than >>>> half), then your theory is rekably elastic. >>> I wouldn't claim stress relief ineffective if I could only get 60 lb >>> increase in tension, whether it be from weak hands or weak rims. >> >> Dear Peter, >> >> This isn't a difficult question to resolve. >> I say that a 60 pound squeeze force will raise ordinary spoke tension >> about 55~65 pounds because I've tested various wheels and found a >> roughly 1-to-1 ratio. >> >> You seem to be claiming that some unnamed wheel that you haven't >> tested should see a much larger tension increase, up to a 5-to-1 >> ratio. > > To be clear, I'm just quoting what Phil Holman reported with his wheel. > > >> If you want to test a wheel yourself, mount the wheel upright over the >> end of a workbench, support one horizontal spoke with a ceiling rope, >> and hang 60 pounds of weights on a rope from the spoke above it. >> Squeeze the spoke pair on the other side of the wheel with a clamp or >> your hand to a similar bend angle. >> >> A Park tension gauge will show the original and increased tension. No >> great accuracy is needed--the 5-to-1 tension increase that you seem to >> expect would be well past the calibrated range of a Park gauge. >> >> Feel free to mail me a wheel that you think is stiffer than a 3/4" >> steel pipe clamp for spoke-squeezing. I'll be happy to test it. Wheels >> are light and cheap to ship, so I'll pay to ship it back to you. > > OK, I had some time this morning. > > I took an old (rear) wheel I have -- Mavic Reflex, 36 hole, rear, 2mm > spokes. > > I measured 7mm deflection with an initial 23lb, and 12mm with an > additional 26lb (49lb total). I used hung weights, so I'm sure of the > forces. I used a caliper to measure the deflections. I don't have a > tensiometer, so I don't know the initial tension, but the differential > should be reasonably accurate. > > By the formula in Jobst's book (T=Force*length/4*displacement), I > calculated a tension of 230lb for the first load, 285 for the second. > So, the additional 26lb increased tension 55lb, or a little over 2:1. that's the problem! jobst's formula doesn't account for rim distortion. you need to measure tension of the spoke directly. which exactly what fogel did. > > This was about what I expected, a hard (50-60lb) squeeze will give me > the nominal 50% over-tension I want in stress relieving. I didn't expect > 5:1, that's just what Phil H reported. My rims aren't as stiff, so that > would explain at least some of the difference. Parenthetically, this > also suggests my wheel was a little under-tensioned, something I don't > doubt, since as I recall, this rim replaced an identical prior rim that > cracked at the spoke holes (both anodized), so I think I took the > tension only as far as I needed to without the spokes unscrewing when > ridden.                             Date: 23 Dec 2006 20:24:40 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > > that's the problem! jobst's formula doesn't account for rim distortion. > you need to measure tension of the spoke directly. which exactly what > fogel did. Yah, you nailed that impostor once again, jim. Keep up the good work!                               Date: 23 Dec 2006 18:25:38 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > jim beam wrote: > >> >> that's the problem! jobst's formula doesn't account for rim >> distortion. you need to measure tension of the spoke directly. which >> exactly what fogel did. > > > Yah, you nailed that impostor once again, jim. Keep up the good work! don't be a sarcastic fool peter. the assumption that a rim is perfectly rigid, as your formula does, is incorrect. therefore assuming spoke tension is a function of simple deflection is incorrect. unless you know the stiffness of the rim and want to adjust accordingly, you have to measure direct. you didn't do that. jobst didn't do that. and besides, if you're so confident that your rims /are/ perfectly rigid, go ahead and prove the point by making direct tension measurements, then reporting your results!                           Date: 23 Dec 2006 12:07:05 From: Subject: Re: I fixed a broken spoke! On Sat, 23 Dec 2006 11:16:54 -0500, Peter Cole <peter_cole@comcast.net > wrote: >OK, I had some time this morning. > >I took an old (rear) wheel I have -- Mavic Reflex, 36 hole, rear, 2mm >spokes. > >I measured 7mm deflection with an initial 23lb, and 12mm with an >additional 26lb (49lb total). I used hung weights, so I'm sure of the >forces. I used a caliper to measure the deflections. I don't have a >tensiometer, so I don't know the initial tension, but the differential >should be reasonably accurate. > >By the formula in Jobst's book (T=Force*length/4*displacement), I >calculated a tension of 230lb for the first load, 285 for the second. >So, the additional 26lb increased tension 55lb, or a little over 2:1. > >This was about what I expected, a hard (50-60lb) squeeze will give me >the nominal 50% over-tension I want in stress relieving. I didn't expect >5:1, that's just what Phil H reported. My rims aren't as stiff, so that >would explain at least some of the difference. Parenthetically, this >also suggests my wheel was a little under-tensioned, something I don't >doubt, since as I recall, this rim replaced an identical prior rim that >cracked at the spoke holes (both anodized), so I think I took the >tension only as far as I needed to without the spokes unscrewing when >ridden. Dear Peter, Sorry, no tension gauge means no reasonably accurate measurement. You're missing repeated explanations of what's wrong with approach that you're using. A bicycle wheel is worthless as a makeshift tension gauge because all tension gauge calculations depend on the two support points being as rigidly fixed as possible. A mere quarter turn of a spoke nipple will visibly deform the rim, so squeezing four spokes twists the rim so much out of shape that the calculations are pointless. Applying large forces to an aluminum hoop braced by a few steel wires is simply not the same as using a massively braced tension gauge that applies small forces. The Park gauge braces its two posts with 3mm thick aluminum against a spring that applies a "weight" so small that you can put your finger between the spoke and the hammer applied by the spring. The whole idea is to avoid deforming the test rig. You measured one spoke's deflection at 12 mm for 49 pounds. Look at these results: http://home.comcast.net/~carlfogel/download/newspok2.jpg I measured the gap between the two squeezed spokes narrowing from ~82 mm to ~47 mm, about ~35 for 2 spokes, or an ~18 mm single spoke deflection with a 100 pound weight hung. God knows what absurd imaginary tension increases might be calculated from this deflection, but the measured real tension increase was only about 90 pounds. Using a tension gauge is like using a rope stretched between a pair of oak trees and measuring the deflection caused by a 5 pound weight. Measuring the deflection of a spoke on an aluminum hoop under a 49 pound weight is like watching a hammock sag between two saplings. Any calculations according to the bend are worthless. Buy a tension gauge and let us know what the actual tensions are. The Park gauge works fine and is about $50 to $75. Afterward, you can sell it on eBay to save money, but it would be a useful tool. If you're not willing to buy a tension gauge for $50, see if you can borrow one from a friend or a local bike shop. Whatever you do to obtain a tension gauge, I predict that it will not show even a 90 pound tension increase for a 60 pound squeeze force. But we're making progress. Your estimates are still high, but you're now aware that your wheels are nowhere near as stiff as you thought they were. Like you, I thought that the high tension increase claims were plausible until I started actually measuring things. Once I slapped a tension gauge on an actual spoke, I stopped relying on theoretical calculations based on theoretical wheels that theoretically were so stiff that they couldn't possibly be trued. Cheers, Carl Fogel                             Date: 23 Dec 2006 20:22:09 From: Peter Cole Subject: Re: I fixed a broken spoke! carlfogel@comcast.net wrote: > On Sat, 23 Dec 2006 11:16:54 -0500, Peter Cole > <peter_cole@comcast.net> wrote: > >> OK, I had some time this morning. >> >> I took an old (rear) wheel I have -- Mavic Reflex, 36 hole, rear, 2mm >> spokes. >> >> I measured 7mm deflection with an initial 23lb, and 12mm with an >> additional 26lb (49lb total). I used hung weights, so I'm sure of the >> forces. I used a caliper to measure the deflections. I don't have a >> tensiometer, so I don't know the initial tension, but the differential >> should be reasonably accurate. >> >> By the formula in Jobst's book (T=Force*length/4*displacement), I >> calculated a tension of 230lb for the first load, 285 for the second. >> So, the additional 26lb increased tension 55lb, or a little over 2:1. >> >> This was about what I expected, a hard (50-60lb) squeeze will give me >> the nominal 50% over-tension I want in stress relieving. I didn't expect >> 5:1, that's just what Phil H reported. My rims aren't as stiff, so that >> would explain at least some of the difference. Parenthetically, this >> also suggests my wheel was a little under-tensioned, something I don't >> doubt, since as I recall, this rim replaced an identical prior rim that >> cracked at the spoke holes (both anodized), so I think I took the >> tension only as far as I needed to without the spokes unscrewing when >> ridden. > > Dear Peter, > > Sorry, no tension gauge means no reasonably accurate measurement. > You're missing repeated explanations of what's wrong with approach > that you're using. > > A bicycle wheel is worthless as a makeshift tension gauge because all > tension gauge calculations depend on the two support points being as > rigidly fixed as possible. > > A mere quarter turn of a spoke nipple will visibly deform the rim, so > squeezing four spokes twists the rim so much out of shape that the > calculations are pointless. > > Applying large forces to an aluminum hoop braced by a few steel wires > is simply not the same as using a massively braced tension gauge that > applies small forces. > > The Park gauge braces its two posts with 3mm thick aluminum against a > spring that applies a "weight" so small that you can put your finger > between the spoke and the hammer applied by the spring. The whole idea > is to avoid deforming the test rig. > > You measured one spoke's deflection at 12 mm for 49 pounds. > > Look at these results: > > http://home.comcast.net/~carlfogel/download/newspok2.jpg > > I measured the gap between the two squeezed spokes narrowing from ~82 > mm to ~47 mm, about ~35 for 2 spokes, or an ~18 mm single spoke > deflection with a 100 pound weight hung. > > God knows what absurd imaginary tension increases might be calculated > from this deflection, but the measured real tension increase was only > about 90 pounds. > > Using a tension gauge is like using a rope stretched between a pair of > oak trees and measuring the deflection caused by a 5 pound weight. > > Measuring the deflection of a spoke on an aluminum hoop under a 49 > pound weight is like watching a hammock sag between two saplings. Any > calculations according to the bend are worthless. > > Buy a tension gauge and let us know what the actual tensions are. The > Park gauge works fine and is about $50 to $75. Afterward, you can sell > it on eBay to save money, but it would be a useful tool. > > If you're not willing to buy a tension gauge for $50, see if you can > borrow one from a friend or a local bike shop. > > Whatever you do to obtain a tension gauge, I predict that it will not > show even a 90 pound tension increase for a 60 pound squeeze force. > > But we're making progress. Your estimates are still high, but you're > now aware that your wheels are nowhere near as stiff as you thought > they were. > > Like you, I thought that the high tension increase claims were > plausible until I started actually measuring things. Once I slapped a > tension gauge on an actual spoke, I stopped relying on theoretical > calculations based on theoretical wheels that theoretically were so > stiff that they couldn't possibly be trued. > > Cheers, > > Carl Fogel Ah, thanks for the concern about the mote in my eye -- shall we now turn to the beam in yours? (double pun intended). I'm not sure if it's worth the bother, as it does really require a grasp of high school level physics -- but here goes: First, to the theory (physics- >vectors). The angle of deflection with a known load does *exactly* determine the tension. Your examples of sturdy oaks and tender saplings are exactly equivalent. The angle *must* reveal the exact ratio of the tension force to the load force (unless Newton was wrong, of course). Since you know the load, and you know the *exact* ratio, you know the *exact* tension. Second, to the measurements. Does the deflection amount *exactly* determine the angle? Despite those nasty rim deflections (seemingly moving the goal posts, as it were)? In a word, yes. As you may recall from middle school trigonometry, we can determine the angle of a right triangle from the hypotenuse and the opposite side. In this case, the hypotenuse is the spoke itself, unchanged in length from its unloaded state except for an ignorable (much less than 1%) amount of stretch. The opposite side is the measured deflection. Note that the other side of the triangle (distance to rim) doesn't enter into the calculation of angle. Third, to the calculations. I know you consider this "theoretical", but I assure you your handy-dandy tensiometer relies on the same theory. Tension = Force/2*sin(theta) (into the book directly from Newton). alternately, Tension = Force*Length/4*Deflection (close approximation). From the measurements you gave, I compute a final tension of 395lb with your 100lb load and 17.5mm deflection, or a ratio of load to tension increase of about 1.5. Fourth, to the issue of "a wheel as a tensiometer". The reason tensiometers (most, anyway) use small loads is so that they won't be measuring the extra tension they create. Unfortunately, this means deflections are small, requiring precision in displacement measurement and also makes them sensitive to friction. These issues, in turn, present challenges to manufacture at a palatable consumer price point. In other words, a $50 tensiometer is probably not a very good tensiometer. A wheel, in comparison, makes a considerably better tensiometer, at least in this rather unusual application. We get to use very large forces and measure over the whole spoke length, making displacement measurements relatively easy with cruder references. Since the forces are large, errors from friction are also less likely to throw things off. Fifth, "what about rim stiffness"? Rim stiffness affects the angle formed by the load. In doing that, it determines the ratio between the load and the tension. Consider the extremes: if your saplings were very flexible, the angle could go to 90. In that case, the tension would be 1/2 the load (the minimum). On the other hand, consider your oaks to be infinitely strong and the rope between them incapable of stretching in the slightest -- in that case, a butterfly landing on it would create infinite tension (with an angle of zero). The reason I measured a force to tension ratio of about 2, and you about 1.5 (despite what your blue-handled vel says) is only because my rim is a bit stiffer. If you still can't get you head around all this, send me your brain. I'll do what I can and pay the return postage.                               Date: 23 Dec 2006 18:23:58 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > carlfogel@comcast.net wrote: >> On Sat, 23 Dec 2006 11:16:54 -0500, Peter Cole >> <peter_cole@comcast.net> wrote: >> >>> OK, I had some time this morning. >>> >>> I took an old (rear) wheel I have -- Mavic Reflex, 36 hole, rear, 2mm >>> spokes. >>> >>> I measured 7mm deflection with an initial 23lb, and 12mm with an >>> additional 26lb (49lb total). I used hung weights, so I'm sure of the >>> forces. I used a caliper to measure the deflections. I don't have a >>> tensiometer, so I don't know the initial tension, but the >>> differential should be reasonably accurate. >>> >>> By the formula in Jobst's book (T=Force*length/4*displacement), I >>> calculated a tension of 230lb for the first load, 285 for the second. >>> So, the additional 26lb increased tension 55lb, or a little over 2:1. >>> >>> This was about what I expected, a hard (50-60lb) squeeze will give me >>> the nominal 50% over-tension I want in stress relieving. I didn't >>> expect 5:1, that's just what Phil H reported. My rims aren't as >>> stiff, so that would explain at least some of the difference. >>> Parenthetically, this also suggests my wheel was a little >>> under-tensioned, something I don't doubt, since as I recall, this rim >>> replaced an identical prior rim that cracked at the spoke holes (both >>> anodized), so I think I took the tension only as far as I needed to >>> without the spokes unscrewing when ridden. >> >> Dear Peter, >> >> Sorry, no tension gauge means no reasonably accurate measurement. >> You're missing repeated explanations of what's wrong with approach >> that you're using. >> A bicycle wheel is worthless as a makeshift tension gauge because all >> tension gauge calculations depend on the two support points being as >> rigidly fixed as possible. >> A mere quarter turn of a spoke nipple will visibly deform the rim, so >> squeezing four spokes twists the rim so much out of shape that the >> calculations are pointless. >> >> Applying large forces to an aluminum hoop braced by a few steel wires >> is simply not the same as using a massively braced tension gauge that >> applies small forces. >> >> The Park gauge braces its two posts with 3mm thick aluminum against a >> spring that applies a "weight" so small that you can put your finger >> between the spoke and the hammer applied by the spring. The whole idea >> is to avoid deforming the test rig. >> >> You measured one spoke's deflection at 12 mm for 49 pounds. >> >> Look at these results: >> >> http://home.comcast.net/~carlfogel/download/newspok2.jpg >> >> I measured the gap between the two squeezed spokes narrowing from ~82 >> mm to ~47 mm, about ~35 for 2 spokes, or an ~18 mm single spoke >> deflection with a 100 pound weight hung. >> God knows what absurd imaginary tension increases might be calculated >> from this deflection, but the measured real tension increase was only >> about 90 pounds. >> >> Using a tension gauge is like using a rope stretched between a pair of >> oak trees and measuring the deflection caused by a 5 pound weight. >> Measuring the deflection of a spoke on an aluminum hoop under a 49 >> pound weight is like watching a hammock sag between two saplings. Any >> calculations according to the bend are worthless. >> >> Buy a tension gauge and let us know what the actual tensions are. The >> Park gauge works fine and is about $50 to $75. Afterward, you can sell >> it on eBay to save money, but it would be a useful tool. >> If you're not willing to buy a tension gauge for $50, see if you can >> borrow one from a friend or a local bike shop. >> >> Whatever you do to obtain a tension gauge, I predict that it will not >> show even a 90 pound tension increase for a 60 pound squeeze force. >> >> But we're making progress. Your estimates are still high, but you're >> now aware that your wheels are nowhere near as stiff as you thought >> they were. >> Like you, I thought that the high tension increase claims were >> plausible until I started actually measuring things. Once I slapped a >> tension gauge on an actual spoke, I stopped relying on theoretical >> calculations based on theoretical wheels that theoretically were so >> stiff that they couldn't possibly be trued. >> >> Cheers, >> >> Carl Fogel > > Ah, thanks for the concern about the mote in my eye -- shall we now turn > to the beam in yours? (double pun intended). I'm not sure if it's worth > the bother, as it does really require a grasp of high school level > physics -- but here goes: > > First, to the theory (physics->vectors). > > The angle of deflection with a known load does *exactly* determine the > tension. Your examples of sturdy oaks and tender saplings are exactly > equivalent. The angle *must* reveal the exact ratio of the tension force > to the load force (unless Newton was wrong, of course). Since you know > the load, and you know the *exact* ratio, you know the *exact* tension. > > Second, to the measurements. > > Does the deflection amount *exactly* determine the angle? Despite those > nasty rim deflections (seemingly moving the goal posts, as it were)? In > a word, yes. > > As you may recall from middle school trigonometry, we can determine the > angle of a right triangle from the hypotenuse and the opposite side. > > In this case, the hypotenuse is the spoke itself, unchanged in length > from its unloaded state except for an ignorable (much less than 1%) > amount of stretch. The opposite side is the measured deflection. Note > that the other side of the triangle (distance to rim) doesn't enter into > the calculation of angle. > > Third, to the calculations. > > I know you consider this "theoretical", but I assure you your > handy-dandy tensiometer relies on the same theory. > > Tension = Force/2*sin(theta) (into the book directly from Newton). > > alternately, Tension = Force*Length/4*Deflection (close approximation). > > From the measurements you gave, I compute a final tension of 395lb with > your 100lb load and 17.5mm deflection, or a ratio of load to tension > increase of about 1.5. > > Fourth, to the issue of "a wheel as a tensiometer". > > The reason tensiometers (most, anyway) use small loads is so that they > won't be measuring the extra tension they create. Unfortunately, this > means deflections are small, requiring precision in displacement > measurement and also makes them sensitive to friction. These issues, in > turn, present challenges to manufacture at a palatable consumer price > point. In other words, a $50 tensiometer is probably not a very good > tensiometer. > > A wheel, in comparison, makes a considerably better tensiometer, at > least in this rather unusual application. We get to use very large > forces and measure over the whole spoke length, making displacement > measurements relatively easy with cruder references. Since the forces > are large, errors from friction are also less likely to throw things off. > > Fifth, "what about rim stiffness"? > > Rim stiffness affects the angle formed by the load. In doing that, it > determines the ratio between the load and the tension. Consider the > extremes: if your saplings were very flexible, the angle could go to 90. > In that case, the tension would be 1/2 the load (the minimum). On the > other hand, consider your oaks to be infinitely strong and the rope > between them incapable of stretching in the slightest -- in that case, a > butterfly landing on it would create infinite tension (with an angle of > zero). > > The reason I measured a force to tension ratio of about 2, and you about > 1.5 (despite what your blue-handled vel says) is only because my rim > is a bit stiffer. > > If you still can't get you head around all this, send me your brain. > I'll do what I can and pay the return postage. > wow dude, you're deeply afflicted with nonsensicitis, with a large dose of dontgethebasics stubbornius thrown in. really, that has to be one of the most willfully obtuse responses i've ever seen on r.b.t., and that's saying something. this stuff is real basic. 1. we have theory and we have practice. if the two do not accord, either the theory is incomplete or the practice is wrong. do you deny that? 2. since the measuring instrument is a commercial off the shelf tool available to us all, with presumably reasonable calibration and consistency from instrument to instrument, that leaves measuring discord in the territory of fogel fraud. are you accusing him of that? 3. if there is no fraud, then the math model is incomplete. and half a moment's thought paying attention to the fact that we don't see rim stiffness in the equation should make anyone pause. assumption that the distance between the two ends of the wire therefore remains perfectly fixed is incorrect. this stuff is real basic peter and it concerns me that you either don't get this stuff or are prepared to deny it.                                 Date: 26 Dec 2006 09:30:49 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > wow dude, you're deeply afflicted with nonsensicitis, with a large dose > of dontgethebasics stubbornius thrown in. really, that has to be one of > the most willfully obtuse responses i've ever seen on r.b.t., and that's > saying something. > > this stuff is real basic. > this stuff is real basic peter and it concerns me that you either don't > get this stuff or are prepared to deny it. OK, you've had a couple of days to think it over, ready to retract?                                   Date: 26 Dec 2006 07:29:11 From: jim beam Subject: Re: I fixed a broken spoke! Peter Cole wrote: > jim beam wrote: > >> wow dude, you're deeply afflicted with nonsensicitis, with a large >> dose of dontgethebasics stubbornius thrown in. really, that has to be >> one of the most willfully obtuse responses i've ever seen on r.b.t., >> and that's saying something. >> >> this stuff is real basic. > >> this stuff is real basic peter and it concerns me that you either >> don't get this stuff or are prepared to deny it. > > OK, you've had a couple of days to think it over, ready to retract? retract that the equation assumes constant L? no!                                     Date: 26 Dec 2006 13:36:45 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > Peter Cole wrote: >> jim beam wrote: >> >>> wow dude, you're deeply afflicted with nonsensicitis, with a large >>> dose of dontgethebasics stubbornius thrown in. really, that has to >>> be one of the most willfully obtuse responses i've ever seen on >>> r.b.t., and that's saying something. >>> >>> this stuff is real basic. >> >>> this stuff is real basic peter and it concerns me that you either >>> don't get this stuff or are prepared to deny it. >> >> OK, you've had a couple of days to think it over, ready to retract? > > retract that the equation assumes constant L? no! You do realize that, according to Pythagoras anyway, that if you know the length of 2 sides of a right triangle you can compute the 3rd? I know you and CF have this abhorrence of "calculation", but you can take it too far.                                       Date: From: Subject:                               Date: 23 Dec 2006 18:51:57 From: Subject: Re: I fixed a broken spoke! On Sat, 23 Dec 2006 20:22:09 -0500, Peter Cole <peter_cole@comcast.net > wrote: >carlfogel@comcast.net wrote: >> On Sat, 23 Dec 2006 11:16:54 -0500, Peter Cole >> <peter_cole@comcast.net> wrote: >> >>> OK, I had some time this morning. >>> >>> I took an old (rear) wheel I have -- Mavic Reflex, 36 hole, rear, 2mm >>> spokes. >>> >>> I measured 7mm deflection with an initial 23lb, and 12mm with an >>> additional 26lb (49lb total). I used hung weights, so I'm sure of the >>> forces. I used a caliper to measure the deflections. I don't have a >>> tensiometer, so I don't know the initial tension, but the differential >>> should be reasonably accurate. >>> >>> By the formula in Jobst's book (T=Force*length/4*displacement), I >>> calculated a tension of 230lb for the first load, 285 for the second. >>> So, the additional 26lb increased tension 55lb, or a little over 2:1. >>> >>> This was about what I expected, a hard (50-60lb) squeeze will give me >>> the nominal 50% over-tension I want in stress relieving. I didn't expect >>> 5:1, that's just what Phil H reported. My rims aren't as stiff, so that >>> would explain at least some of the difference. Parenthetically, this >>> also suggests my wheel was a little under-tensioned, something I don't >>> doubt, since as I recall, this rim replaced an identical prior rim that >>> cracked at the spoke holes (both anodized), so I think I took the >>> tension only as far as I needed to without the spokes unscrewing when >>> ridden. >> >> Dear Peter, >> >> Sorry, no tension gauge means no reasonably accurate measurement. >> You're missing repeated explanations of what's wrong with approach >> that you're using. >> >> A bicycle wheel is worthless as a makeshift tension gauge because all >> tension gauge calculations depend on the two support points being as >> rigidly fixed as possible. >> >> A mere quarter turn of a spoke nipple will visibly deform the rim, so >> squeezing four spokes twists the rim so much out of shape that the >> calculations are pointless. >> >> Applying large forces to an aluminum hoop braced by a few steel wires >> is simply not the same as using a massively braced tension gauge that >> applies small forces. >> >> The Park gauge braces its two posts with 3mm thick aluminum against a >> spring that applies a "weight" so small that you can put your finger >> between the spoke and the hammer applied by the spring. The whole idea >> is to avoid deforming the test rig. >> >> You measured one spoke's deflection at 12 mm for 49 pounds. >> >> Look at these results: >> >> http://home.comcast.net/~carlfogel/download/newspok2.jpg >> >> I measured the gap between the two squeezed spokes narrowing from ~82 >> mm to ~47 mm, about ~35 for 2 spokes, or an ~18 mm single spoke >> deflection with a 100 pound weight hung. >> >> God knows what absurd imaginary tension increases might be calculated >> from this deflection, but the measured real tension increase was only >> about 90 pounds. >> >> Using a tension gauge is like using a rope stretched between a pair of >> oak trees and measuring the deflection caused by a 5 pound weight. >> >> Measuring the deflection of a spoke on an aluminum hoop under a 49 >> pound weight is like watching a hammock sag between two saplings. Any >> calculations according to the bend are worthless. >> >> Buy a tension gauge and let us know what the actual tensions are. The >> Park gauge works fine and is about $50 to $75. Afterward, you can sell >> it on eBay to save money, but it would be a useful tool. >> >> If you're not willing to buy a tension gauge for $50, see if you can >> borrow one from a friend or a local bike shop. >> >> Whatever you do to obtain a tension gauge, I predict that it will not >> show even a 90 pound tension increase for a 60 pound squeeze force. >> >> But we're making progress. Your estimates are still high, but you're >> now aware that your wheels are nowhere near as stiff as you thought >> they were. >> >> Like you, I thought that the high tension increase claims were >> plausible until I started actually measuring things. Once I slapped a >> tension gauge on an actual spoke, I stopped relying on theoretical >> calculations based on theoretical wheels that theoretically were so >> stiff that they couldn't possibly be trued. >> >> Cheers, >> >> Carl Fogel > >Ah, thanks for the concern about the mote in my eye -- shall we now turn >to the beam in yours? (double pun intended). I'm not sure if it's worth >the bother, as it does really require a grasp of high school level >physics -- but here goes: > >First, to the theory (physics->vectors). > >The angle of deflection with a known load does *exactly* determine the >tension. Your examples of sturdy oaks and tender saplings are exactly >equivalent. The angle *must* reveal the exact ratio of the tension force >to the load force (unless Newton was wrong, of course). Since you know >the load, and you know the *exact* ratio, you know the *exact* tension. > >Second, to the measurements. > >Does the deflection amount *exactly* determine the angle? Despite those >nasty rim deflections (seemingly moving the goal posts, as it were)? In >a word, yes. > >As you may recall from middle school trigonometry, we can determine the >angle of a right triangle from the hypotenuse and the opposite side. > >In this case, the hypotenuse is the spoke itself, unchanged in length >from its unloaded state except for an ignorable (much less than 1%) >amount of stretch. The opposite side is the measured deflection. Note >that the other side of the triangle (distance to rim) doesn't enter into >the calculation of angle. > >Third, to the calculations. > >I know you consider this "theoretical", but I assure you your >handy-dandy tensiometer relies on the same theory. > >Tension = Force/2*sin(theta) (into the book directly from Newton). > >alternately, Tension = Force*Length/4*Deflection (close approximation). > > From the measurements you gave, I compute a final tension of 395lb with >your 100lb load and 17.5mm deflection, or a ratio of load to tension >increase of about 1.5. > >Fourth, to the issue of "a wheel as a tensiometer". > >The reason tensiometers (most, anyway) use small loads is so that they >won't be measuring the extra tension they create. Unfortunately, this >means deflections are small, requiring precision in displacement >measurement and also makes them sensitive to friction. These issues, in >turn, present challenges to manufacture at a palatable consumer price >point. In other words, a $50 tensiometer is probably not a very good >tensiometer. > >A wheel, in comparison, makes a considerably better tensiometer, at >least in this rather unusual application. We get to use very large >forces and measure over the whole spoke length, making displacement >measurements relatively easy with cruder references. Since the forces >are large, errors from friction are also less likely to throw things off. > >Fifth, "what about rim stiffness"? > >Rim stiffness affects the angle formed by the load. In doing that, it >determines the ratio between the load and the tension. Consider the >extremes: if your saplings were very flexible, the angle could go to 90. >In that case, the tension would be 1/2 the load (the minimum). On the >other hand, consider your oaks to be infinitely strong and the rope >between them incapable of stretching in the slightest -- in that case, a >butterfly landing on it would create infinite tension (with an angle of >zero). > >The reason I measured a force to tension ratio of about 2, and you about >1.5 (despite what your blue-handled vel says) is only because my rim >is a bit stiffer. > >If you still can't get you head around all this, send me your brain. >I'll do what I can and pay the return postage. Dear Peter, There's not much point in discussing things with someone who'll do anything but measure the actual tension under discussion. I predict that you won't see 90 pounds of tension rise for a squeeze force of 60 pounds if you ever actually measure the spoke tension instead of insisting that you can calculate it correctly. Your rim is unlikely to be anywhere near as stiff in regard to the tensions applied as a steel pipe clamp. Since it's easy to do, your reluctance to confirm your claim to implausibly high tension rises by a simple direct measurement will be the last word on the matter. Cheers, Carl Fogel             Date: 20 Dec 2006 08:03:01 From: jim beam Subject: Re: I fixed a broken spoke! carlfogel@comcast.net wrote: > On Tue, 19 Dec 2006 14:05:00 -0600, Gary Young <garyyoung3@gmail.com> > wrote: > > > [snip] > >> Well, I can't say I understand the crux of your disagreement with >> Jobst, but I'm trying to work my way through it. > > [snip] > > Dear Gary, > > So am I. > > For decades, riders usually carried a few spare spokes on tours > because they expected spokes to break. Jobst has mentioned this > practice. > > In the early 1980's, Jobst wrote "The Bicycle Wheel" and theorized > that squeezing spoke pairs together would relieve residual stress in > spoke bends. > > But ten years later, Jobst wrote > > "It appears that the better spokes now available would have made the > discovery of many of the concepts of this book more difficult for lack > of failure data. I am grateful in retrospect for the poor durability > of earlier spokes. They operated so near their limits that durability > was significantly altered by the techniques that I have outlined." > > --Jobst Brandt, "The Bicycle Wheel," 3rd Edition, 1993, p.124 > > I agree that spokes have become much more durable. The evidence is > overwhelming. Few riders bother to carry spare spokes any more, partly > because they have cell phones, but mostly because they don't expect > spokes to break very often. The 36-spoke wheels of the past have been > replaced by wheels with fewer and fewer spokes. Despite the obvious > increase in stress, the spokes last longer. > > The spokes are the same length and thickness. The threading and elbow > bends are made in the same way. The only real change has been years of > steady improvement in the quality of the stainless steel wire. > > After all, the most likely explanation for an occasional spoke > breaking is variation in the spoke material. The bending and > tensioning and so forth are quite regular. If squeezing spoke pairs > was solving some residual stress problem by raising tension, the same > problem would be causing all the other spokes to fail. > > I see Jobst's comment in 1993 that spokes somehow became much more > durable as strong evidence that he was mistaken about how efffective > spoke-sqeezing is. > > I also see the lack of variation in results as evidence that > spoke-squeezers are fooling themselves. The repeated claim that > squeezing makes spokes immortal implies that there is no level at > which the spokes are merely given longer lifespans. Everyone seems to > believe that they squeeze just as strongly with their weak hand as > they do with their strong hand, and just as strongly the ninth time as > they do the first time. > > I'm unable to find any testing or evidence that supports the claim, as > opposed claims that one step out of many in building a wheel must be > responsible for anecdotal improvements. Again, look at the strange > comment in the 3rd edition. Spokes somehow became so durable in a > decade that Jobst wrote that it would have been hard to "discover" his > theory. I see it as evidence that his theory was wrong. > > The lack of testing and measuring to confirm the theory is curious. > > Until I started hanging weights from spokes and measuring the tension > changes with a gauge, RBT posters would make good-faith theoretical > calculations that showed huge tension increases. > > This illustrates how easily we fool ourselves and how easy it is to > make huge mistakes. I have never doubted the good faith of the last > such calculation that appeared on RBT. A 30 pound side force moved a > spoke a certain distance and bent the spoke at such and so an angle, > which in turn allowed calculations for steel of specifc thickness to > indicate that the spoke tension would rise approximately 150 pounds, a > 5 to 1 ratio. > > The calculations were correct, but they were based on the assumption > that the rim and the hub would stay in fixed positions. > > How could a newsgroup full of wheel-builders assume that the rim would > stay in a fixed position when tension increased 150 pounds? > > I'm just as guilty as everyone else who read such posts over the years > without raising an eyebrow. The huge tension increase seemed plausible > and certainly supported Jobst's theory. But I was curious enough to > fiddle around until I finally figured out an obvious way to measure > the tension increase directly. > > Oops! > > A 30-pound squeeze force on a left and a right spoke-pair will raise > the spoke tension only about 30 pounds, not 150. A 60-pound squeeze > will raise tension only about 55~65 pounds. Higher squeeze forces are > unlikely for most RBT posters. A 100-pound squeeze will leave a faint > permanent bend in a spoke. > > The impressive bend angles are due mostly to the slack gained as the > four obviously unbalanced spokes twist the rim into a slight N or Z > shape. > > (A weird detail is that spoke tension actually drops as you start to > squeeze. In addition to the rim deforming, the spokes are bent across > other spokes in a cross-3 pattern, and they gain a little initial > slack as they press into the other spoke and straighten a little at > that point. The low-squeeze-force tension drop startled the hell out > of me, but was so consistent that I finally had to admit that it was > real. Noticing the bend where the spokes cross took an embarrassingly > long time.) > > All of this could have been figured out and predicted as theory, but > no one was trying to figure out what might be wrong with Jobst's > theory. Most of us set out with an unconscious bias toward working > things out in accordance with the theory. > > That's how sensible people can end up calculating a 150-pound spoke > tension increase from 250 to 400 pounds with a 30-pound squeeze force. > A moment's thought would raise the obvious objection. No one ever > complains that he squeezed his spokes so hard that they stretched like > taffy or pulled through the rim. But there are a number of posters who > could squeeze with 100 pounds of force--which the mistaken calculation > predicts would raise the spoke tension over 450 pounds, from 250 to > 700. Jobst's tensile tests showed that spokes yield at around 600 > pounds. > > I tested various wheels and had fun staring at odd details and working > out better and better techniques, but most of my elaborate testing was > a waste of time--the results were immediately obvious. > > Anyone who supports one spoke with a ceiling rope, hangs a known > weight on a rope tied to the spoke above it, and measures the tension > with a Park gauge can see how much a 60-pound squeeze force wil raise > the spoke tension. It's not a matter of great precision or poring over > reams of data. It's about like weighing sacks of dog food. > > So spoke-squeezing didn't actually raise spoke tension anywhere near > as high as people had been thinking. Their mistake was thinking > instead of testing and letting theory and what they'd like to prove > lead them to where they wanted to go. > > The next thing to test was the effect of tension on residual stress. > > Everyone agrees that residual stresses exist when a spoke is bent to > form the elbow. > > The usual method of relieving residual stress is heating. > > Bend a stainless steel spoke 90 degrees, heat the bend to a glowing > orange with a propane torch, and you can see the end of the spoke move > as the bend expands. > > So I cobbled together a crude vise rig and started bending spokes into > U shapes. > > A spoke bent but not stretched expands considerably when heated. > > A spoke bent and tensioned slightly in the vise will expand noticeably > less. > > A spoke bent and tensioned more will expand even less. > > A spoke bent and tensioned to normal bicycle wheel levels (~200 lbs) > will hardly expand at all. > > A spoke bent and tensioned to ~400 pounds will hardly expand at all, > just like the spoke tensioned to ~200 pounds. > > I think that heating the whole bend to a glowing orange relieves any > residual stresses. The spoke that was never tensioned has lots of > residual stresses and its bend expands a lot. The spoke that was > lightly tensioned has had its strongest residual stresses relieved byt > the tension, so it bends less. By the time that tension has reached > 200 pounds, practically all residual stresses have been relieved, so > there's practically nothing left for the heat to change, and the spoke > bend scarcely changes. > > The bending after heating clearly depends on how much tension is > applied to the spoke. > > Note that rather than pursuing the testing and trying to think of ways > to change the test and confirm or refute it, Jobst just complains that > it's destructive. I'm willing to listen to suggestions and arguments > about whether what happens is explained by stress relief, but red > herrings about the destruction of a few dollars worth of spokes are > absurd. > > My problem with the spoke-squeezing theory is that it seems to be a > lot of theory developed to support preconceived and self-flattering > conclusions about how we can cure the King's Evil by the laying on of > hands. > > My counter-argument is subject to the same criticism in that I > naturally want my tests and interpretations to be right. > > But I think that it's obvious who's interested in actual testing and > measuring. There's not only a lack of interest in testing and > confirmation on one side, but an explicit bias against any testing or > confirmation. Anyone can read through the endless posts on the subject > and see commment after comment about how no tests would be convincing > evidence against the theory, how no tests are needed, and how we don't > need no stinkin' tests. > > Of course, the stress-relief question is just a tempest in a tea-cup. > But it does shed some interesting light on how prone RBT is to typing > and defending theories instead of trying to test them. > > Cheers, > > Carl Fogel carl, i gotta say, that's an excellent sumy of the situation. in terms of theory, you are 100% correct about the influence of materials on fatigue vs. unsubstantiated supposition, and you are 100% correct about your heating experiments being illustrative of residual stress relaxation - no bending on heating, no residual stress. finally, your experiments on spoke tension increase on squeezing are excellent. i would have always thought it obvious that when the usual bleatings about "wheels stand on their bottom spokes" were being batted around, we were simply observing rim deformation [hopefully it's obvious that if the rim were perfectly rigid, spoke tension pattern would be totally different], but apparently not. i only have one other comment; it is /not/ correct to say that "all rbt posters agree" that spokes contain residual stress just because they're bent however - that's the jobstian assumption that seems to have propagated into the vacuum that is the mind of the unquestioning. but all in all, a great sumy, and i applaud your willingness to ask the difficult question "why?" - it seems to be a dirty word around these parts. i guess because most people that dare ask it are derided as charlatans and [understandably] take their learning elsewhere. a very regrettable state of affairs.         Date: 05 Dec 2006 01:04:10 From: Subject: Re: I fixed a broken spoke! someone writes: >>> If you are breaking non-drive side spokes, this indicates without >>> a doubt that they are crap spokes. (based on info from your >>> previous posts, that you don't weigh 400lbs,etc) >> Even the best spokes fail if they are not formed to the hub and >> stress relieved. Don't push it off on the spoke manufacturer when >> it's the builder who needs to take measures to make the wheel >> durable. > Stress relief is just going around the wheel sort of pinching the > spokes? There's more to it than that, but yes. A better method of stress relief is to stand the wheel on its axle and press down on the rim with hands diametrically opposite, once between each pair of spokes. However, first the outbound spokes must be manually bent to lie flush against the flange. Then by grasping pairs of spokes on opposite sides of the wheel and squeezing them together will make sure that your wheel is not too tight. Jobst Brandt           Date: 04 Dec 2006 19:33:43 From: jim beam Subject: Re: I fixed a broken spoke! jobst.brandt@stanfordalumni.org wrote: > someone writes: > >>>> If you are breaking non-drive side spokes, this indicates without >>>> a doubt that they are crap spokes. (based on info from your >>>> previous posts, that you don't weigh 400lbs,etc) > >>> Even the best spokes fail if they are not formed to the hub and >>> stress relieved. Don't push it off on the spoke manufacturer when >>> it's the builder who needs to take measures to make the wheel >>> durable. > >> Stress relief is just going around the wheel sort of pinching the >> spokes? > > There's more to it than that, but yes. A better method of stress > relief is to stand the wheel on its axle and press down on the rim > with hands diametrically opposite, once between each pair of spokes. > > However, first the outbound spokes must be manually bent to lie flush > against the flange. doing that before raising spokes to full "stress relief" tension will ensure the angle to which they will be bent is too acute. the hub holes will deform [seat] under tension, and it is /that/ angle to which the spokes must be formed, if any, *NOT* the angle /before/ the hub holes are seated. but given that the hub flanges are canted and that the angle which the spoke manufacturer already provides is already appropriate, there's no point in this exercise in the first place. spoke quality is item #1 in the fight against fatigue, not witchcraft. > Then by grasping pairs of spokes on opposite > sides of the wheel and squeezing them together will make sure that > your wheel is not too tight. > > Jobst Brandt             Date: 06 Dec 2006 21:30:18 From: Jasper Janssen Subject: Re: I fixed a broken spoke! On Mon, 04 Dec 2006 19:33:43 -0800, jim beam <spamvortex@bad.example.net > wrote: >doing that before raising spokes to full "stress relief" tension will >ensure the angle to which they will be bent is too acute. the hub holes >will deform [seat] under tension, and it is /that/ angle to which the >spokes must be formed, if any, *NOT* the angle /before/ the hub holes >are seated. but given that the hub flanges are canted and that the >angle which the spoke manufacturer already provides is already >appropriate, there's no point in this exercise in the first place. >spoke quality is item #1 in the fight against fatigue, not witchcraft. Spoke heads are bent at about a 95 degree angle, which is just about appropriate for the inside spokes, but the outside spokes need to be bent a bit further than 90 degrees. The fact that the spoke head angle isn't 90 degrees and that the flange is not at the same place in the dimension along the axle as the rim is means that there is always asymmetry between inside and outside spokes and therefore they are *not* already perfectly formed. Jasper               Date: 06 Dec 2006 21:13:24 From: jim beam Subject: Re: I fixed a broken spoke! Jasper Janssen wrote: > On Mon, 04 Dec 2006 19:33:43 -0800, jim beam <spamvortex@bad.example.net> > wrote: > >> doing that before raising spokes to full "stress relief" tension will >> ensure the angle to which they will be bent is too acute. the hub holes >> will deform [seat] under tension, and it is /that/ angle to which the >> spokes must be formed, if any, *NOT* the angle /before/ the hub holes >> are seated. but given that the hub flanges are canted and that the >> angle which the spoke manufacturer already provides is already >> appropriate, there's no point in this exercise in the first place. >> spoke quality is item #1 in the fight against fatigue, not witchcraft. > > Spoke heads are bent at about a 95 degree angle, which is just about > appropriate for the inside spokes, but the outside spokes need to be bent > a bit further than 90 degrees. no they don't - for this reason: http://www.flickr.com/photos/38636024@N00/104463818/ you also forget the interleaving of the spokes averaging the angles on both sides of the flange. > The fact that the spoke head angle isn't 90 > degrees and that the flange is not at the same place in the dimension > along the axle as the rim is means that there is always asymmetry between > inside and outside spokes and therefore they are *not* already perfectly > formed. no. see above.                 Date: 07 Dec 2006 09:33:38 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > Jasper Janssen wrote: >> Spoke heads are bent at about a 95 degree angle, which is just about >> appropriate for the inside spokes, but the outside spokes need to be bent >> a bit further than 90 degrees. > > no they don't - for this reason: > http://www.flickr.com/photos/38636024@N00/104463818/ > you also forget the interleaving of the spokes averaging the angles on > both sides of the flange. > >> The fact that the spoke head angle isn't 90 >> degrees and that the flange is not at the same place in the dimension >> along the axle as the rim is means that there is always asymmetry between >> inside and outside spokes and therefore they are *not* already perfectly >> formed. > > no. see above. "If the spokes have a good snug fit at the flange, the outbound spokes may have a slight bow where they emerge from the spoke holes. Push these spokes down against the flange near their elbows with your thumb so that they make contact against the flange. Inbound spokes usually lie flat and need no correction. These adjustments require skills that come with practice." "The Bicycle Wheel", third edition, page 96. The context is for a tensioned wheel. I can't see what's so controversial about carefully taking the bow out of a tensioned wheel if one exists. Ditto for bows at the nipples.               Date: 06 Dec 2006 20:31:38 From: jim beam Subject: Re: I fixed a broken spoke! Jasper Janssen wrote: > On Mon, 04 Dec 2006 19:33:43 -0800, jim beam <spamvortex@bad.example.net> > wrote: > >> doing that before raising spokes to full "stress relief" tension will >> ensure the angle to which they will be bent is too acute. the hub holes >> will deform [seat] under tension, and it is /that/ angle to which the >> spokes must be formed, if any, *NOT* the angle /before/ the hub holes >> are seated. but given that the hub flanges are canted and that the >> angle which the spoke manufacturer already provides is already >> appropriate, there's no point in this exercise in the first place. >> spoke quality is item #1 in the fight against fatigue, not witchcraft. > > Spoke heads are bent at about a 95 degree angle, which is just about > appropriate for the inside spokes, but the outside spokes need to be bent > a bit further than 90 degrees. The fact that the spoke head angle isn't 90 > degrees and that the flange is not at the same place in the dimension > along the axle as the rim is means that there is always asymmetry between > inside and outside spokes and therefore they are *not* already perfectly > formed. > > Jasper they're not "perfectly" formed, but they're good enough given that the hub flanges are canted and that the hub holes deform! and don't forget that the spokes interleave making the exit angle of the spoke about the same for both inbound and outbound spokes at full tension - unlike when untensioned, the time at with "correcting the spoke like" is [prematurely] advocated.                 Date: 07 Dec 2006 09:07:57 From: Peter Cole Subject: Re: I fixed a broken spoke! jim beam wrote: > unlike when > untensioned, the time at with "correcting the spoke like" is > [prematurely] advocated. Who advocates correcting the spoke line on an untensioned wheel?               Date: 07 Dec 2006 00:40:34 From: Subject: Re: I fixed a broken spoke! Jasper Janssen writes: >> doing that before raising spokes to full "stress relief" tension >> will ensure the angle to which they will be bent is too acute. the >> hub holes will deform [seat] under tension, and it is /that/ angle >> to which the spokes must be formed, if any, *NOT* the angle >> /before/ the hub holes are seated. but given that the hub flanges >> are canted and that the angle which the spoke manufacturer already >> provides is already appropriate, there's no point in this exercise >> in the first place. spoke quality is item #1 in the fight against >> fatigue, not witchcraft. > Spoke heads are bent at about a 95 degree angle, which is just about > appropriate for the inside spokes, but the outside spokes need to be > bent a bit further than 90 degrees. The fact that the spoke head > angle isn't 90 degrees and that the flange is not at the same place > in the dimension along the axle as the rim is means that there is > always asymmetry between inside and outside spokes and therefore > they are *not* already perfectly formed. I agree and in addition, a spoke elbow that is, perhaps, 85=C2=B0 and nee= ds to be 95=C2=B0 cannot be opened to that angle once in place. That is the reason for not reusing spokes that have been taken out of a wheel. The inbound and outbound spokes being difficult to recognize and the ones with acute angles may not fit the new wheel. Jobst Brandt                 Date: 06 Dec 2006 20:41:56 From: jim beam Subject: Re: I fixed a broken spoke! jobst.brandt@stanfordalumni.org wrote: > Jasper Janssen writes: > >>> doing that before raising spokes to full "stress relief" tension >>> will ensure the angle to which they will be bent is too acute. the >>> hub holes will deform [seat] under tension, and it is /that/ angle >>> to which the spokes must be formed, if any, *NOT* the angle >>> /before/ the hub holes are seated. but given that the hub flanges >>> are canted and that the angle which the spoke manufacturer already >>> provides is already appropriate, there's no point in this exercise >>> in the first place. spoke quality is item #1 in the fight against >>> fatigue, not witchcraft. > >> Spoke heads are bent at about a 95 degree angle, which is just about >> appropriate for the inside spokes, but the outside spokes need to be >> bent a bit further than 90 degrees. The fact that the spoke head >> angle isn't 90 degrees and that the flange is not at the same place >> in the dimension along the axle as the rim is means that there is >> always asymmetry between inside and outside spokes and therefore >> they are *not* already perfectly formed. > > I agree and in addition, a spoke elbow that is, perhaps, 85° and needs > to be 95° cannot be opened to that angle once in place. That is the > reason for not reusing spokes that have been taken out of a wheel. > The inbound and outbound spokes being difficult to recognize and the > ones with acute angles may not fit the new wheel. eh? so which side of the fence do you sit here jobst? if the inbound and outbound spokes can't be told apart after they've been used, there's no necessity to "correct the spoke line", right?                   Date: 12 Dec 2006 01:21:09 From: Jasper Janssen Subject: Re: I fixed a broken spoke! On Wed, 06 Dec 2006 20:41:56 -0800, jim beam <spamvortex@bad.example.net > wrote: >jobst.brandt@stanfordalumni.org wrote: >> I agree and in addition, a spoke elbow that is, perhaps, 85° and needs >> to be 95° cannot be opened to that angle once in place. That is the >> reason for not reusing spokes that have been taken out of a wheel. >> The inbound and outbound spokes being difficult to recognize and the >> ones with acute angles may not fit the new wheel. > >eh? so which side of the fence do you sit here jobst? if the inbound >and outbound spokes can't be told apart after they've been used, there's >no necessity to "correct the spoke line", right? How good are you at telling 95 from 85 degrees, visually, on something the radius of a spoke head bend? In an often dark-ish workshop, of course. Jasper                     Date: 11 Dec 2006 20:49:00 From: jim beam Subject: Re: I fixed a broken spoke! Jasper Janssen wrote: > On Wed, 06 Dec 2006 20:41:56 -0800, jim beam <spamvortex@bad.example.net> > wrote: >> jobst.brandt@stanfordalumni.org wrote: > >>> I agree and in addition, a spoke elbow that is, perhaps, 85� and needs >>> to be 95� cannot be opened to that angle once in place. That is the >>> reason for not reusing spokes that have been taken out of a wheel. >>> The inbound and outbound spokes being difficult to recognize and the >>> ones with acute angles may not fit the new wheel. >> eh? so which side of the fence do you sit here jobst? if the inbound >> and outbound spokes can't be told apart after they've been used, there's >> no necessity to "correct the spoke line", right? > > How good are you at telling 95 from 85 degrees, visually, on something the > radius of a spoke head bend? In an often dark-ish workshop, of course. > > Jasper well, i can compare used with new, since i have both in the lab. and i can compare left with right if i'm repairing a wheel. i can also measure extension of the straight sections if i want to be really pedantic. it's not impossible. particularly if i can be bothered to turn the lab lights on.                   Date: 07 Dec 2006 13:24:52 From: Subject: Re: I fixed a broken spoke! On Wed, 06 Dec 2006 20:41:56 -0800, jim beam <spamvortex@bad.example.net > wrote: >> >> I agree and in addition, a spoke elbow that is, perhaps, 85° and needs >> to be 95° cannot be opened to that angle once in place. That is the >> reason for not reusing spokes that have been taken out of a wheel. >> The inbound and outbound spokes being difficult to recognize and the >> ones with acute angles may not fit the new wheel. > >eh? so which side of the fence do you sit here jobst? if the inbound >and outbound spokes can't be told apart after they've been used, there's >no necessity to "correct the spoke line", right? How do you get from "difficult" to "can't be told"? Or are they the same, for you?             Date: 05 Dec 2006 09:43:21 From: dvt Subject: Re: I fixed a broken spoke! jim beam wrote: > but given that the hub flanges are canted and that the > angle which the spoke manufacturer already provides is already > appropriate, there's no point in this exercise in the first place. You never answered this question the first time, so let's try again... How are the hub flanges canted optimally for all the variations of wheels? In bound vs. out bound, crossing pattern, and rim size all affect the angle in question. I don't see hubs keted for each variation, and I don't see holes labeled for inbound and outbound spokes. Do small wheels (think recumbent) usually use the same hubs as diamond frame bikes? If so, do they have a much higher incidence of spoke breakage? -- Dave dvt at psu dot edu Everyone confesses that exertion which brings out all the powers of body and mind is the best thing for us; but most people do all they can to get rid of it, and as a general rule nobody does much more than circumstances drive them to do. -Harriet Beecher Stowe, abolitionist and novelist (1811-1896)               Date: 22 Dec 2006 11:02:35 From: Ron Ruff Subject: Re: I fixed a broken spoke! Peter Cole wrote: > When you ride an un-stress relieved wheel "around the block", "honking > up hills", as I said before, you can put lateral loads on the wheel, > which will nominally increase (some) spoke tension. Bear in mind that > the contact patch is also loaded vertically, so you are first reducing > static tension, then superimposing a (potentially large) lateral load. I'd like to add that the torque component can be significant as well... especially if there are 10 or less spokes resisting torque... and the rider is really throwing his weight on the pedals. For instance: Effective flange radius (mm) 20 Crank length (mm) 175 Front sprocket teeth 34 Rear sprocket teeth 25 Crossed spokes on drive side 10 Force exerted on crank (kg) 150 Spoke tension change (kg) +-96.5! You may object to the 150kg force... but I'm pretty sure I can get that much force (double body weight) momentarily without even trying that hard. Of course, during normal seated climbing it would be much lower... ~1/4th as much.                 Date: 22 Dec 2006 19:24:13 From: Subject: Re: I fixed a broken spoke! Ron Ruff writes: >> When you ride an un-stress relieved wheel "around the block", >> "honking up hills", as I said before, you can put lateral loads on >> the wheel, which will nominally increase (some) spoke tension. >> Bear in mind that the contact patch is also loaded vertically, so >> you are first reducing static tension, then superimposing a >> (potentially large) lateral load. > I'd like to add that the torque component can be significant as > well... especially if there are 10 or less spokes resisting > torque... and the rider is really throwing his weight on the > pedals. For instance: > Effective flange radius (mm) 20 Crank length (mm) 175 Front sprocket > teeth 34 Rear sprocket teeth 25 Crossed spokes on drive side 10 > Force exerted on crank (kg) 150 > Spoke tension change (kg) +-96.5! > You may object to the 150kg force... but I'm pretty sure I can get > that much force (double body weight) momentarily without even trying > that hard. Of course, during normal seated climbing it would be > much lower... ~1/4th as much. I wasn't aware that there were ten spoke rear wheels, but the analysis of torque on wheels is graphically shown in "the Bicycle Wheel" and, even for fewer spokes, is not as large as you say. The load is borne by both pulling and pushing spokes, the ones getting tighter and the others, looser. These graphs and values in the book are based on a unit load for comparison sake and is much higher than a rider can exert. It is in essence climbing a vertical wall. All loads are the same for radial load, braking and accelerating, in oder to show comparisons. Jobst Brandt               Date: 05 Dec 2006 20:23:10 From: jim beam Subject: Re: I fixed a broken spoke! dvt wrote: > jim beam wrote: >> but given that the hub flanges are canted and that the angle which the >> spoke manufacturer already provides is already appropriate, there's no >> point in this exercise in the first place. > > You never answered this question the first time, so let's try again... dave, some threads get too long and windy. if you want to /ensure/ i read a question that's somehow important, post a new thread. and make sure i'm not on vacation, traveling, otherwise busy or disinterested. > How are the hub flanges canted optimally for all the variations of > wheels? they're not. they're optimized for the commonest configuration 32/36, 3x. road hubs for road rims, mtb hubs for 26" rims, etc. roughly 3° for drive, 6° for non-drive. > In bound vs. out bound, crossing pattern, and rim size all > affect the angle in question. I don't see hubs keted for each > variation, and I don't see holes labeled for inbound and outbound > spokes. Do small wheels (think recumbent) usually use the same hubs as > diamond frame bikes? If so, do they have a much higher incidence of > spoke breakage? > if you want to demonstrate something dave, do the math for the spoke angle given that a hub hole may be larger diameter than the spoke and seated in a flange of given thickness. then compare that to the stock spoke angle of ~95°.                 Date: 06 Dec 2006 12:18:35 From: dvt Subject: Re: I fixed a broken spoke! jim beam wrote: > dvt wrote: >> jim beam wrote: >>> but given that the hub flanges are canted and that the angle which >>> the spoke manufacturer already provides is already appropriate, >>> there's no point in this exercise in the first place. >> You never answered this question the first time, so let's try again... > dave, some threads get too long and windy. if you want to /ensure/ i > read a question that's somehow important, post a new thread. and make > sure i'm not on vacation, traveling, otherwise busy or disinterested. Nice try, jim. Here's the record: <http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/1c072f5d8b7c8892/83a78e954c0f932d > Scroll down to messages 103-110. You responded to that exact subthread, so I know you were reading it. But you failed to answer the question. >> In bound vs. out bound, crossing pattern, and rim size all affect the >> angle in question. I don't see hubs keted for each variation, and I >> don't see holes labeled for inbound and outbound spokes. Do small >> wheels (think recumbent) usually use the same hubs as diamond frame >> bikes? If so, do they have a much higher incidence of spoke breakage? > if you want to demonstrate something dave, do the math for the spoke > angle given that a hub hole may be larger diameter than the spoke and > seated in a flange of given thickness. then compare that to the stock > spoke angle of ~95°. You made the claim. It's your job to prove it. Here's the claim you made, in case you've forgotten: "the spoke elbow comes pre-formed with the best resultant angle and the hub flange is canted and drilled also to give the best resultant angle." You made no reservations about wheel size, lacing pattern, or any of the other things you tried to add in later when questioned. And what about dished wheels? Or rims with offset spoke beds? I'm looking forward to your response. -- Dave dvt at psu dot edu Everyone confesses that exertion which brings out all the powers of body and mind is the best thing for us; but most people do all they can to get rid of it, and as a general rule nobody does much more than circumstances drive them to do. -Harriet Beecher Stowe, abolitionist and novelist (1811-1896)                   Date: 06 Dec 2006 21:09:48 From: jim beam Subject: Re: I fixed a broken spoke! dvt wrote: > jim beam wrote: >> dvt wrote: >>> jim beam wrote: >>>> but given that the hub flanges are canted and that the angle which >>>> the spoke manufacturer already provides is already appropriate, >>>> there's no point in this exercise in the first place. > >>> You never answered this question the first time, so let's try again... > >> dave, some threads get too long and windy. if you want to /ensure/ i >> read a question that's somehow important, post a new thread. and make >> sure i'm not on vacation, traveling, otherwise busy or disinterested. > > Nice try, jim. Here's the record: > > <http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/1c072f5d8b7c8892/83a78e954c0f932d> is this the 'unanswered' question? "I've been watching this thread, hoping that I wasn't the only one with this question. How do you "cant and drill" a hole in the hub flange so that both inbound *and* outbound spokes are "optimized?" If the hole was so canted, would that mean that the hubs should not be deformed during the build?" if so, i'd have thought the answers obvious. maybe that's why i didn't bother answering. > > > Scroll down to messages 103-110. You responded to that exact subthread, > so I know you were reading it. But you failed to answer the question. > >>> In bound vs. out bound, crossing pattern, and rim size all affect the >>> angle in question. I don't see hubs keted for each variation, and >>> I don't see holes labeled for inbound and outbound spokes. Do small >>> wheels (think recumbent) usually use the same hubs as diamond frame >>> bikes? If so, do they have a much higher incidence of spoke breakage? > >> if you want to demonstrate something dave, do the math for the spoke >> angle given that a hub hole may be larger diameter than the spoke and >> seated in a flange of given thickness. then compare that to the stock >> spoke angle of ~95°. > > You made the claim. It's your job to prove it. Here's the claim you > made, in case you've forgotten: > > "the spoke elbow comes pre-formed with the best resultant angle and the > hub flange is canted and drilled also to give the best resultant angle." > > You made no reservations about wheel size, lacing pattern, or any of the > other things you tried to add in later when questioned. And what about > dished wheels? Or rims with offset spoke beds? > > I'm looking forward to your response. > unless you want a full custom hub, the economics don't support accommodating non-standard configurations. two hub pics for consideration: http://www.flickr.com/photos/38636024@N00/316202144/ http://www.flickr.com/photos/38636024@N00/316202143/ for the cynics, i didn't happen to have any 2.4mm rod about for the hub hole pic, but if you don't believe the hub holes are perpendicular to the flange, do this experiment yourself. for dave, no, there's nothing sinister about this hub being black or large flange. it just happened to be a virgin hub at the top of my parts box.                     Date: 22 Dec 2006 23:54:00 From: Ron Ruff Subject: Re: I fixed a broken spoke! jim beam wrote: > Ron Ruff wrote: > > wheels. My question is... would more tension be even better? Carl may > > be convinced that overtension isn't even necessary... but I'm not > > convinced that his tests replicate what is going on in the j-bend of > > the spoke. > > it may not mimic exactly, but it's a damned good illustration of the > principles - and his results are entirely consistent with theory. if > you're not convinced, you should be. I've taken a more thorough look at Carl's test and I'm closer to being convinced than I used to be. The only obvious issue I see now is: Are j-bends on spokes formed by stretching them around a curve as Carl did? (I think not) And if not, would this result in a difference between his results and the behaviour of a real spoke? As I recall from Jobst's experience at the DT factory, their j-bends were formed by knocking the head sideways... hopefully around a mandrel of some sort. I would expect(?) this to produce a different stress distribution than pulling the spoke around a radius with high tensile force. One way to find out would be to form the tight bend radius using... a roller?... a rubber or plastic mallet?... hopefully replicating the way that the bend is formed at the factory, *then* put it in the vice as before and pull, with the two ends close together.                     Date: 22 Dec 2006 00:09:35 From: Ron Ruff Subject: Re: I fixed a broken spoke! jim beam wrote: > ironically, no. it relies too much on spoke tension being exactly even > - most unlikely. as a consequence of this method, the highest tension > spokes will see even more, the least less so. the best method is the > mavic method - it raises tension for just a few spokes at a time, seats > even untensioned spokes, and doesn't require fancy equipment or > extensive prep. There will be a variance in max tension equal to the initial variation... but that should be small if the wheel was trued ahead of time...~10kg. The advantage I see is that the force can be higher than that achieved by using muscle and body weight and it can also be precisely controlled. > i don't agree that bit. spokes need to conform in the tensed state, not > relaxed. What I meant was that the spoke has no tendency to bend outward from the hub when the tension is relaxed... ie it conforms in both conditions. > it may not mimic exactly, but it's a damned good illustration of the > principles - and his results are entirely consistent with theory. if > you're not convinced, you should be. Again, I might have missed something... but what I recall of Carl's experiments was that he bent spokes sharply in the middle, then tensioned them a certain amount, then heated them (annealed) to relieve stress, and observed how much they opened up in the bent portion. His conclusion was that the stress was relieved at a relatively low tension... less than a typical wheel is tensioned to... and that overtensioning was unnecessary. One objection I have (beyond any that I'm too ignorant to think of) is that he didn't replicate the way that a j bend is supported in the hub... which could require a higher tension to achieve the same thing. At least I would expect that to be the case. I probably should dig through those posts more thoroughly, but time has been short lately... > or if you simply want to test to see if residual stress > exists, either before or after build, place the degreased spoke in a > strongish chloride solution, sit back and wait a few weeks. it's a > stress corrosion test and this kind of thing is used throughout industry > as a quick and dirty means of seeing if things are ok. Sounds promising... could you explain in more detail how that would be done, and what it would mean?                       Date: 22 Dec 2006 07:46:18 From: jim beam Subject: Re: I fixed a broken spoke! Ron Ruff wrote: > jim beam wrote: >> ironically, no. it relies too much on spoke tension being exactly even >> - most unlikely. as a consequence of this method, the highest tension >> spokes will see even more, the least less so. the best method is the >> mavic method - it raises tension for just a few spokes at a time, seats >> even untensioned spokes, and doesn't require fancy equipment or >> extensive prep. > > There will be a variance in max tension equal to the initial > variation... but that should be small if the wheel was trued ahead of > time...~10kg. bit's a lot of work to tension to that accuracy, then destroy it again, while getting uneven results spoke to spoke, etc. the point is, the mavic method is insensitive to variance - the above method is not. > The advantage I see is that the force can be higher than > that achieved by using muscle and body weight and it can also be > precisely controlled. the useful limit appears to be quite easy to control - if the wheel's tensioned, when the spokes farthest from you go slack, you know the job is done. > >> i don't agree that bit. spokes need to conform in the tensed state, not >> relaxed. > > What I meant was that the spoke has no tendency to bend outward from > the hub when the tension is relaxed... ie it conforms in both > conditions. > >> it may not mimic exactly, but it's a damned good illustration of the >> principles - and his results are entirely consistent with theory. if >> you're not convinced, you should be. > > Again, I might have missed something... but what I recall of Carl's > experiments was that he bent spokes sharply in the middle, then > tensioned them a certain amount, then heated them (annealed) to relieve > stress, and observed how much they opened up in the bent portion. His > conclusion was that the stress was relieved at a relatively low > tension... less than a typical wheel is tensioned to... and that > overtensioning was unnecessary. One objection I have (beyond any that > I'm too ignorant to think of) is that he didn't replicate the way that > a j bend is supported in the hub... which could require a higher > tension to achieve the same thing. At least I would expect that to be > the case. I probably should dig through those posts more thoroughly, > but time has been short lately... that's irrelevant. the point of the experiment, which it so well shows, is that regardless of configuration, residual stress as evidenced by springback on thermal activation, is present in the untensed state, then progressively disappears as increasing tension is applied. the useful quantization is that the tension necessary to achieve this result is below that which is the service stress. > >> or if you simply want to test to see if residual stress >> exists, either before or after build, place the degreased spoke in a >> strongish chloride solution, sit back and wait a few weeks. it's a >> stress corrosion test and this kind of thing is used throughout industry >> as a quick and dirty means of seeing if things are ok. > > Sounds promising... could you explain in more detail how that would be > done, and what it would mean? > use an old jelly jar and a salt. http://en.wikipedia.org/wiki/Stress_corrosion_cracking boiling 42% magnesium chloride is industry standard, but room temp common salt works, albeit /much/ more slowly. this seems a good explanation: http://www.npl.co.uk/lmm/docs/stress.pdf                     Date: 21 Dec 2006 21:35:19 From: Ron Ruff Subject: Re: I fixed a broken spoke! carlfogel@comcast.net wrote: > If you're just as happy with a mistaken claim that a 30-pound squeeze > will raise a spoke 150 pounds from 250 to 400 pounds of tension as you > are with test results showing that a 60-pound squeeze (twice as much > squeeze force) will raise the same spoke only 55~65 pounds (less than > half), then your theory is rekably elastic. I must have missed that thread... I've missed a lot lately. But... FWIW I was able to raise the tension on my front wheel by ~50kg (110lb) by resting most of my 165lb on opposing edges of the rim. The rim is a Mavic CXP21 and spokes are 32 WS AE15s (1.8x1.55mm) 2x... so I'd say that using the "mavic method" works pretty well for increasing the tension. Supporting the rim fully and using a hydraulic press on the axle to give uniform and controlled pressure sounds even better, though (Rinard and Trek). It seems like the big unknown here is how much over-tension (if any) is needed to stress relieve the elbow of the spoke. I think even jim beam will agree that we want j-bend spokes to conform to the side of the hub as well as possible, even if there is disagreement on how this is best achieved. If the spoke is properly formed (before and during the build) there should minimal bending stress on the spoke elbow. I think this is what all good wheel builders are trying to achieve. I also think history gives evidence that a well built wheel with j-bend spokes performs very well and that straight pull spokes, though they have some theoretical advantages, offer little if any improvement compared to a *good* wheel with j-bend spokes. J-bend spokes are problematic only if the wheel was poorly built. So what constitutes a "good" build? Most of us can agree that lubrication of the spoke-nipple-rim interfaces, "forming" the spokes so that they take a straight path in the relaxed state, and stress relieving (overtensioning) the spokes are good practices. I think Jobst and those who have used his method of stress relieving have also shown that "spoke-squeezing" is at least adequate for producing a good set of wheels. My question is... would more tension be even better? Carl may be convinced that overtension isn't even necessary... but I'm not convinced that his tests replicate what is going on in the j-bend of the spoke. Carl... I applaud you for your efforts, though! You are doing a lot more interesting experimental work than anybody else around here... hope you keep it up. Can anyone think of a simple test that would verify the effect of overtension on an actual j-bend of a spoke installed in a hub? Jim... do you have access to equipment that could be used to analyze this, or know someone who does?                       Date: 22 Dec 2006 00:58:55 From: Subject: Re: I fixed a broken spoke! On 21 Dec 2006 21:35:19 -0800, "Ron Ruff" <rruffrruff@yahoo.com > wrote: > >carlfogel@comcast.net wrote: >> If you're just as happy with a mistaken claim that a 30-pound squeeze >> will raise a spoke 150 pounds from 250 to 400 pounds of tension as you >> are with test results showing that a 60-pound squeeze (twice as much >> squeeze force) will raise the same spoke only 55~65 pounds (less than >> half), then your theory is rekably elastic. > >I must have missed that thread... I've missed a lot lately. But... FWIW >I was able to raise the tension on my front wheel by ~50kg (110lb) by >resting most of my 165lb on opposing edges of the rim. The rim is a >Mavic CXP21 and spokes are 32 WS AE15s (1.8x1.55mm) 2x... so I'd say >that using the "mavic method" works pretty well for increasing the >tension. Supporting the rim fully and using a hydraulic press on the >axle to give uniform and controlled pressure sounds even better, though >(Rinard and Trek). [snip] Dear Ron, Squeezing two pairs of spokes, each with ~60 pounds of squeeze, will raise the spoke tension about 55~65 pounds. The rim deforms into a faint N or Z shape, providing enough slack for dramatic bends. The deformity is due to the four spokes always being staggered so that the end spokes are pulling in opposite directions. This should be no surprise, since that's how we true wheels--a quarter turn of a 56 tpi spoke nipple will move a rim noticeably sideways. Leaning with your weight on either side of a wheel laid flat will produce noticeably larger spoke tension increases for two reasons. First, most posters can lean eighteen times with a lot more force than they can squeeze eighteen times. Lean with your arms locked, and gravity is going to do the rest. Second, the rim is much stiffer in respect to the spokes under each palm and you're effectively using those sections as handles in opposition to each other. That's why other spokes lose tension dramatically with the Mavic lean-on-the-rim method and make cracking noises as they unwind. The rim is being pushed down on either side, so the top spokes under each hand gain tension, while the spokes underneath lose it. Squeezing spoke pairs does almost nothing to lower tension. Here's a graph of a what happens to the spokes with a 100 pound load on a board laid across a horizontal wheel to mimic the Mavic method: http://i10.tinypic.com/2njccc9.jpg The pattern is quite regular. With 36 spokes and evenly spaced hands (like a board), one hand will be right over one topside spoke, while the other hand will be between two topside spokes. Notice that this is reflected in the two peaks on the graph. Notice also how five bottom spokes lose significant tension. That's why more than one poster noticed cracking noises as spokes unwound on wheels whose spoke pairs had previously been squeezed--the lean-on-the-rim method drops spoke tension dramatically. Here's the start of the thread: http://groups.google.com/group/rec.bicycles.tech/msg/5c0ce7ddb9094b02 As for the spoke-squeeze testing, here's a graph for initial high tension: http://home.comcast.net/~carlfogel/download/newspok2.jpg Notice that the red spoke that started out at higher initial tension actually loses tension at first and never gains as much as the other spoke (yellow line). The graph goes from 0 to 100 pounds of squeeze force in 5-lb increments, so you can see that at about 60 pounds of squeeze force, there's about a 60-pound rise in tension. And another graph for lower initial tension: http://home.comcast.net/~carlfogel/download/newspoke_graph.jpg Same pattern. The spoke with higher initial tension doesn't gain as much as the spoke with lower initial tension. Again, 60 pounds of squeeze force produces about 60 pounds of tension rise. Claims that stiffer rims will somehow produce a 5-fold tension increase for the same force are implausible. Even the stiffest bicycle rim moves visibly with a quarter turn of a spoke nipple--that's how we true them. After testing various aluminum rims and finding none that produced anything better than 55~65 pounds of tension increase for a 60-pound squeeze force, I stretched a 2mm spoke horizontally in a 3/4" steel pipe clamp, tensioned it to 235 pounds, and hung a 60 pound weight from its midspan. Tension rose about 90 pounds. If anyone thinks that a round spoke 2mm thick will significantly bend a 3/4" (19mm) steel pipe clamp whose walls are 0.110" (2.8mm) thick over a span of about 12 inches, they're welcome to try the experiment and post pictures. Here's the pipe-clamp thread: http://groups.google.com/group/rec.bicycles.tech/msg/bce241a75595fbed Here's a picture of the pipe-clamp in action: http://i13.tinypic.com/2yo7778.jpg An email asked how I'd hung 60 pounds of weights from a claw hammer. I didn't. That's a 2-foot ripping or wrecking crowbar, which does look a bit like a claw hammer from that angle. The weights fit onto the shaft quite conveniently. Cheers, Carl Fogel                       Date: 21 Dec 2006 23:03:24 From: jim beam Subject: Re: I fixed a broken spoke! Ron Ruff wrote: > carlfogel@comcast.net wrote: >> If you're just as happy with a mistaken claim that a 30-pound squeeze >> will raise a spoke 150 pounds from 250 to 400 pounds of tension as you >> are with test results showing that a 60-pound squeeze (twice as much >> squeeze force) will raise the same spoke only 55~65 pounds (less than >> half), then your theory is rekably elastic. > > I must have missed that thread... I've missed a lot lately. But... FWIW > I was able to raise the tension on my front wheel by ~50kg (110lb) by > resting most of my 165lb on opposing edges of the rim. The rim is a > Mavic CXP21 and spokes are 32 WS AE15s (1.8x1.55mm) 2x... so I'd say > that using the "mavic method" works pretty well for increasing the > tension. Supporting the rim fully and using a hydraulic press on the > axle to give uniform and controlled pressure sounds even better, though > (Rinard and Trek). ironically, no. it relies too much on spoke tension being exactly even - most unlikely. as a consequence of this method, the highest tension spokes will see even more, the least less so. the best method is the mavic method - it raises tension for just a few spokes at a time, seats even untensioned spokes, and doesn't require fancy equipment or extensive prep. > > It seems like the big unknown here is how much over-tension (if any) is > needed to stress relieve the elbow of the spoke. I think even jim beam > will agree that we want j-bend spokes to conform to the side of the hub > as well as possible, even if there is disagreement on how this is best > achieved. If the spoke is properly formed (before and during the build) > there should minimal bending stress on the spoke elbow. I think this is > what all good wheel builders are trying to achieve. I also think > history gives evidence that a well built wheel with j-bend spokes > performs very well and that straight pull spokes, though they have some > theoretical advantages, offer little if any improvement compared to a > *good* wheel with j-bend spokes. J-bend spokes are problematic only if > the wheel was poorly built. > > So what constitutes a "good" build? Most of us can agree that > lubrication of the spoke-nipple-rim interfaces, "forming" the spokes so > that they take a straight path in the relaxed state, i don't agree that bit. spokes need to conform in the tensed state, not relaxed. > and stress > relieving (overtensioning) the spokes are good practices. I think Jobst > and those who have used his method of stress relieving have also shown > that "spoke-squeezing" is at least adequate for producing a good set of > wheels. My question is... would more tension be even better? Carl may > be convinced that overtension isn't even necessary... but I'm not > convinced that his tests replicate what is going on in the j-bend of > the spoke. it may not mimic exactly, but it's a damned good illustration of the principles - and his results are entirely consistent with theory. if you're not convinced, you should be. it's regrettable that r.b.t. is so poisoned with bullshit and spite that no one believes anything anyone says, even when they're telling the truth. > Carl... I applaud you for your efforts, though! You are > doing a lot more interesting experimental work than anybody else around > here... hope you keep it up. indeed. > > Can anyone think of a simple test that would verify the effect of > overtension on an actual j-bend of a spoke installed in a hub? Jim... > do you have access to equipment that could be used to analyze this, or > know someone who does? you can do the expensive thing and get it x-rayed or even neutron diffracted. or if you simply want to test to see if residual stress exists, either before or after build, place the degreased spoke in a strongish chloride solution, sit back and wait a few weeks. it's a stress corrosion test and this kind of thing is used throughout industry as a quick and dirty means of seeing if things are ok.                     Date: 07 Dec 2006 11:59:40 From: dvt Subject: Re: I fixed a broken spoke! jim beam wrote: > dvt wrote: > > is this the 'unanswered' question? > 'I've been watching this thread, hoping that I wasn't the only one with > this question. How do you "cant and drill" a hole in the hub flange so > that both inbound *and* outbound spokes are "optimized?"' I snipped the last bit, leaving the specific question. > if you don't believe the hub holes are perpendicular to > the flange, do this experiment yourself. I never doubted that hub flanges were canted. I *don't* understand why you consider that cant optimal when there are so many different ways to lace a wheel. -- Dave dvt at psu dot edu Everyone confesses that exertion which brings out all the powers of body and mind is the best thing for us; but most people do all they can to get rid of it, and as a general rule nobody does much more than circumstances drive them to do. -Harriet Beecher Stowe, abolitionist and novelist (1811-1896)                       Date: 07 Dec 2006 20:07:55 From: jim beam Subject: Re: I fixed a broken spoke! dvt wrote: > jim beam wrote: >> dvt wrote: > >> >> is this the 'unanswered' question? >> 'I've been watching this thread, hoping that I wasn't the only one with >> this question. How do you "cant and drill" a hole in the hub flange so >> that both inbound *and* outbound spokes are "optimized?"' > > I snipped the last bit, leaving the specific question. > >> if you don't believe the hub holes are perpendicular to the flange, do >> this experiment yourself. > > I never doubted that hub flanges were canted. I *don't* understand why > you consider that cant optimal when there are so many different ways to > lace a wheel. > i already answered this question. 12/05.                         Date: 08 Dec 2006 13:46:14 From: dvt Subject: Re: I fixed a broken spoke! jim beam wrote: > dvt wrote: >> I never doubted that hub flanges were canted. I *don't* understand why >> you consider that cant optimal when there are so many different ways >> to lace a wheel. > i already answered this question. 12/05. On 9 Nov 2006, jim beam wrote: > the hub holes deform during the build. "correcting the spoke line" > before this process has occurred is premature and will leave the > spoke elbow with the wrong resultant angle. the spoke elbow comes > pre-formed with the best resultant angle and the hub flange is canted > and drilled also to give the best resultant angle. it may look odd > when first laced, but when fully tensioned, the net result is > optimized. i therefore say leave the spoke elbow angle alone - do > /not/ bend. On 5 Dec 2006, jim beam wrote: >> How are the hub flanges canted optimally for all the variations of >> wheels? > they're not. they're optimized for the commonest configuration > 32/36, 3x. road hubs for road rims, mtb hubs for 26" rims, etc. > roughly 3° for drive, 6° for non-drive. When building a small wheel, or a wheel that's not 3x, or some other combination that does not meet your specs, should the user "improve the spoke line?" What crossing pattern should be used with <32 spoke hubs? -- Dave dvt at psu dot edu Everyone confesses that exertion which brings out all the powers of body and mind is the best thing for us; but most people do all they can to get rid of it, and as a general rule nobody does much more than circumstances drive them to do. -Harriet Beecher Stowe, abolitionist and novelist (1811-1896)                           Date: 08 Dec 2006 21:31:14 From: jim beam Subject: Re: I fixed a broken spoke! dvt wrote: > jim beam wrote: >> dvt wrote: > >>> I never doubted that hub flanges were canted. I *don't* understand >>> why you consider that cant optimal when there are so many different >>> ways to lace a wheel. > >> i already answered this question. 12/05. > > On 9 Nov 2006, jim beam wrote: > >> the hub holes deform during the build. "correcting the spoke line" >> before this process has occurred is premature and will leave the >> spoke elbow with the wrong resultant angle. the spoke elbow comes >> pre-formed with the best resultant angle and the hub flange is canted >> and drilled also to give the best resultant angle. it may look odd >> when first laced, but when fully tensioned, the net result is >> optimized. i therefore say leave the spoke elbow angle alone - do >> /not/ bend. > > On 5 Dec 2006, jim beam wrote: >>> How are the hub flanges canted optimally for all the variations of >>> wheels? > >> they're not. they're optimized for the commonest configuration >> 32/36, 3x. road hubs for road rims, mtb hubs for 26" rims, etc. >> roughly 3° for drive, 6° for non-drive. > > When building a small wheel, or a wheel that's not 3x, or some other > combination that does not meet your specs, should the user "improve the > spoke line?" in extreme circumstances, probably, yes. but otoh, i'd never use a hub/rim combo that were that deviant. whatever the situation, if it were my wheel, i'd do the "mavic method" of stress relief first [which does not require full spoke tension] to be sure the hub holes were fully conformed before any consideration of bending. > > What crossing pattern should be used with <32 spoke hubs? > that's a "how long is a piece of string" question - it depends on the hub size, rim size, etc. personally, i use 3x on 28 spoke, low flange, road rim. and i never bend spoke elbows.                             Date: 11 Dec 2006 12:24:29 From: dvt Subject: Re: I fixed a broken spoke! jim beam wrote: > dvt wrote: >> When building a small wheel, or a wheel that's not 3x, or some other >> combination that does not meet your specs, should the user "improve >> the spoke line?" > > in extreme circumstances, probably, yes. but otoh, i'd never use a > hub/rim combo that were that deviant. whatever the situation, if it > were my wheel, i'd do the "mavic method" of stress relief first [which > does not require full spoke tension] to be sure the hub holes were fully > conformed before any consideration of bending. So in some cases, the benefits of "improving the spoke line" outweigh what you you see as the detriments of that method. I'd like to know where to draw that line. -- Dave dvt at psu dot edu                               Date: 11 Dec 2006 20:50:42 From: jim beam Subject: Re: I fixed a broken spoke! dvt wrote: > jim beam wrote: >> dvt wrote: >>> When building a small wheel, or a wheel that's not 3x, or some other >>> combination that does not meet your specs, should the user "improve >>> the spoke line?" >> >> in extreme circumstances, probably, yes. but otoh, i'd never use a >> hub/rim combo that were that deviant. whatever the situation, if it >> were my wheel, i'd do the "mavic method" of stress relief first [which >> does not require full spoke tension] to be sure the hub holes were >> fully conformed before any consideration of bending. > > So in some cases, the benefits of "improving the spoke line" outweigh > what you you see as the detriments of that method. I'd like to know > where to draw that line. > you can do a pretty good guesstimate of the cant on the flange, [if you can't find it on the manufacturer web site], you can determine if the spoke holes are parallel to the hub axle or perpendicular to the flange and you can calculate the spoke angle with the rim. from there, you can make a pretty well informed decision on whether to mutilate your spokes or not.                                 Date: 12 Dec 2006 09:26:09 From: dvt Subject: Re: I fixed a broken spoke! jim beam wrote: > dvt wrote: >> jim beam wrote: >>> dvt wrote: >>>> When building a small wheel, or a wheel that's not 3x, or some other >>>> combination that does not meet your specs, should the user "improve >>>> the spoke line?" >>> in extreme circumstances, probably, yes. but otoh, i'd never use a >>> hub/rim combo that were that deviant. whatever the situation, if it >>> were my wheel, i'd do the "mavic method" of stress relief first >>> [which does not require full spoke tension] to be sure the hub holes >>> were fully conformed before any consideration of bending. >> So in some cases, the benefits of "improving the spoke line" outweigh >> what you you see as the detriments of that method. I'd like to know >> where to draw that line. > you can do a pretty good guesstimate of the cant on the flange, [if you > can't find it on the manufacturer web site], you can determine if the > spoke holes are parallel to the hub axle or perpendicular to the flange > and you can calculate the spoke angle with the rim. from there, you can > make a pretty well informed decision on whether to mutilate your spokes > or not. Maybe you could, but I couldn't. What is a reasonable cutoff? 1°? 10°? -- Dave dvt at psu dot edu Everyone confesses that exertion which brings out all the powers of body and mind is the best thing for us; but most people do all they can to get rid of it, and as a general rule nobody does much more than circumstances drive them to do. -Harriet Beecher Stowe, abolitionist and novelist (1811-1896)                                   Date: 12 Dec 2006 19:29:02 From: jim beam Subject: Re: I fixed a broken spoke! dvt wrote: > jim beam wrote: >> dvt wrote: >>> jim beam wrote: >>>> dvt wrote: >>>>> When building a small wheel, or a wheel that's not 3x, or some >>>>> other combination that does not meet your specs, should the user >>>>> "improve the spoke line?" > >>>> in extreme circumstances, probably, yes. but otoh, i'd never use a >>>> hub/rim combo that were that deviant. whatever the situation, if it >>>> were my wheel, i'd do the "mavic method" of stress relief first >>>> [which does not require full spoke tension] to be sure the hub holes >>>> were fully conformed before any consideration of bending. > >>> So in some cases, the benefits of "improving the spoke line" outweigh >>> what you you see as the detriments of that method. I'd like to know >>> where to draw that line. > >> you can do a pretty good guesstimate of the cant on the flange, [if >> you can't find it on the manufacturer web site], you can determine if >> the spoke holes are parallel to the hub axle or perpendicular to the >> flange and you can calculate the spoke angle with the rim. from >> there, you can make a pretty well informed decision on whether to >> mutilate your spokes or not. > > Maybe you could, but I couldn't. why not? you're st enough to progress your position this far. the rest is simple geometry. > What is a reasonable cutoff? 1°? 10°? > what's the angle in the bent spoke resulting from where crossed spokes interleave? spokes never fail there, even though the spoke is under substantial bending strain. that would be a good place from which to gauge whether permanent deformation is or is not required. but even then, this debate is entirely academic for regular rim/hub/crossing combos since that's what spokes are optimized for out of the box.                     Date: 06 Dec 2006 23:49:12 From: Subject: Re: I fixed a broken spoke! On Wed, 06 Dec 2006 21:09:48 -0800, jim beam <spamvortex@bad.example.net > wrote: >dvt wrote: >> jim beam wrote: >>> dvt wrote: >>>> jim beam wrote: >>>>> but given that the hub flanges are canted and that the angle which >>>>> the spoke manufacturer already provides is already appropriate, >>>>> there's no point in this exercise in the first place. >> >>>> You never answered this question the first time, so let's try again... >> >>> dave, some threads get too long and windy. if you want to /ensure/ i >>> read a question that's somehow important, post a new thread. and make >>> sure i'm not on vacation, traveling, otherwise busy or disinterested. >> >> Nice try, jim. Here's the record: >> >> <http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/1c072f5d8b7c8892/83a78e954c0f932d> > >is this the 'unanswered' question? >"I've been watching this thread, hoping that I wasn't the only one with >this question. How do you "cant and drill" a hole in the hub flange so >that both inbound *and* outbound spokes are "optimized?" If the hole was >so canted, would that mean that the hubs should not be deformed during >the build?" > >if so, i'd have thought the answers obvious. maybe that's why i didn't >bother answering. > >> >> >> Scroll down to messages 103-110. You responded to that exact subthread, >> so I know you were reading it. But you failed to answer the question. >> >>>> In bound vs. out bound, crossing pattern, and rim size all affect the >>>> angle in question. I don't see hubs keted for each variation, and >>>> I don't see holes labeled for inbound and outbound spokes. Do small >>>> wheels (think recumbent) usually use the same hubs as diamond frame >>>> bikes? If so, do they have a much higher incidence of spoke breakage? >> >>> if you want to demonstrate something dave, do the math for the spoke >>> angle given that a hub hole may be larger diameter than the spoke and >>> seated in a flange of given thickness. then compare that to the stock >>> spoke angle of ~95°. >> >> You made the claim. It's your job to prove it. Here's the claim you >> made, in case you've forgotten: >> >> "the spoke elbow comes pre-formed with the best resultant angle and the >> hub flange is canted and drilled also to give the best resultant angle." >> >> You made no reservations about wheel size, lacing pattern, or any of the >> other things you tried to add in later when questioned. And what about >> dished wheels? Or rims with offset spoke beds? >> >> I'm looking forward to your response. >> >unless you want a full custom hub, the economics don't support >accommodating non-standard configurations. > >two hub pics for consideration: >http://www.flickr.com/photos/38636024@N00/316202144/ >http://www.flickr.com/photos/38636024@N00/316202143/ > >for the cynics, i didn't happen to have any 2.4mm rod about for the hub >hole pic, but if you don't believe the hub holes are perpendicular to >the flange, do this experiment yourself. > >for dave, no, there's nothing sinister about this hub being black or >large flange. it just happened to be a virgin hub at the top of my >parts box. Dear Jim, The canting of the outside hub flanges is indeed obvious, once I looked carefully. Alas, I can't take very good pictures, but here's a used 1998 Shimano 7-speed cassette hub that shows the canting that you're talking about. The inside of each flange is as dead-on to the camera as I could manage, and is 90-degrees to the axle. The outside of each flange angles noticeably inward, toward a rim. You can see the dirty spoke holes on the outside of each flange because of the canting. An on-screen protractor shows that the outside of the drive-side flange is angled about 10 degrees inward toward a rim, while the outside of the non-drive-side flange is angled inward a bit less, about 7~8 degrees. In Explorer click on the lower right to enlarge images. Drive-side hub flange, outside canted inward about 10 degrees: http://i12.tinypic.com/49fvs3t.jpg Non-drive-side hub flange, outside canted inward about 8 degrees: http://i10.tinypic.com/43ykwmx.jpg Onscreen protractor and ruler: http://www.kus-bader.de/MB-Ruler/ Cheers, Carl Fogel                       Date: 07 Dec 2006 09:23:33 From: Peter Cole Subject: Re: I fixed a broken spoke! carlfogel@comcast.net wrote: > > The canting of the outside hub flanges is indeed obvious, once I > looked carefully. > > "Most hubs have their flanges angled inward slightly to reduce the difference between the elbow bends of inbound and outbound spokes." The Bicycle Wheel, third edition, page 96.                 Date: 06 Dec 2006 11:36:01 From: Subject: Re: I fixed a broken spoke! On Tue, 05 Dec 2006 20:23:10 -0800, jim beam <spamvortex@bad.example.net > wrote: >> In bound vs. out bound, crossing pattern, and rim size all >> affect the angle in question. I don't see hubs keted for each >> variation, and I don't see holes labeled for inbound and outbound >> spokes. Do small wheels (think recumbent) usually use the same hubs as >> diamond frame bikes? If so, do they have a much higher incidence of >> spoke breakage? >> > >if you want to demonstrate something dave, do the math for the spoke >angle given that a hub hole may be larger diameter than the spoke and >seated in a flange of given thickness. then compare that to the stock >spoke angle of ~95°. I think I saw those calculations a while ago - it was in a book called "The Bicycle Wheel", I think.                   Date: 22 Dec 2006 14:20:59 From: Subject: Re: I fixed a broken spoke! jobst.brandt@stanfordalumni.org wrote: > I wasn't aware that there were ten spoke rear wheels, but the analysis > of torque on wheels is graphically shown in "the Bicycle Wheel" and, > even for fewer spokes, is not as large as you say. Well... I might have made a mistake... but off hand I don't see where it is. I only have the 2nd edition of your book and it doesn't seem to have the analysis you describe. Anyway, it is a simple calculation (or at least I *thought* it was): dT= Fc*Lc*Nr/Nf/re/Ns Fc= Crank force Lc= Crank length Nr= Number of teeth in the rear cog Nf= Number of teeth in the front cog re= Effective radius of spokes at the hub flange Ns= Number of crossed spokes Did I miss something? There are plenty of wheels these days that only have 20 spokes in the back, with one side being radial.                     Date: 22 Dec 2006 23:45:45 From: Subject: Re: I fixed a broken spoke! Ron Ruff writes: >> I wasn't aware that there were ten spoke rear wheels, but the >> analysis of torque on wheels is graphically shown in "the Bicycle >> Wheel" and, even for fewer spokes, is not as large as you say. > Well... I might have made a mistake... but off hand I don't see > where it is. I only have the 2nd edition of your book and it doesn't > seem to have the analysis you describe. Anyway, it is a simple > calculation (or at least I *thought* it was): > dT= Fc*Lc*Nr/Nf/re/Ns > Fc= Crank force > Lc= Crank length > Nr= Number of teeth in the rear cog > Nf= Number of teeth in the front cog > re= Effective radius of spokes at the hub flange > Ns= Number of crossed spokes > Did I miss something? I don't know what you mean by number of crossed spokes. Even radial spokes will transmit torque of a strong sprinter. > There are plenty of wheels these days that only have 20 spokes in > the back, with one side being radial. Most of those wheels have a sufficiently large center piece to cause both sides of the wheel (left and right spokes) to transmit drive. All editions have the deflection diagrams of wheel deflections under load, braking and drive and combinations of each, the numerical values for which are in the appendix. Take a look. It isn't much. Jobst Brandt                       Date: 22 Dec 2006 17:48:03 From: jim beam Subject: Re: I fixed a broken spoke! jobst.brandt@stanfordalumni.org wrote: > Ron Ruff writes: > >>> I wasn't aware that there were ten spoke rear wheels, but the >>> analysis of torque on wheels is graphically shown in "the Bicycle >>> Wheel" and, even for fewer spokes, is not as large as you say. > >> Well... I might have made a mistake... but off hand I don't see >> where it is. I only have the 2nd edition of your book and it doesn't >> seem to have the analysis you describe. Anyway, it is a simple >> calculation (or at least I *thought* it was): > >> dT= Fc*Lc*Nr/Nf/re/Ns > >> Fc= Crank force >> Lc= Crank length >> Nr= Number of teeth in the rear cog >> Nf= Number of teeth in the front cog >> re= Effective radius of spokes at the hub flange >> Ns= Number of crossed spokes > >> Did I miss something? > > I don't know what you mean by number of crossed spokes. Even radial > spokes will transmit torque of a strong sprinter. > >> There are plenty of wheels these days that only have 20 spokes in >> the back, with one side being radial. > > Most of those wheels have a sufficiently large center piece to cause > both sides of the wheel (left and right spokes) to transmit drive. All > editions have the deflection diagrams of wheel deflections under load, > braking and drive and combinations of each, the numerical values for > which are in the appendix. Take a look. It isn't much. > > Jobst Brandt wow, what a spectacular non-answer!                   Date: 06 Dec 2006 12:09:28 From: Subject: Re: I fixed a broken spoke! On Wed, 06 Dec 2006 11:36:01 GMT, jtaylor@NOSPAM.hfx.andara.com wrote: >On Tue, 05 Dec 2006 20:23:10 -0800, jim beam ><spamvortex@bad.example.net> wrote: > > >>> In bound vs. out bound, crossing pattern, and rim size all >>> affect the angle in question. I don't see hubs keted for each >>> variation, and I don't see holes labeled for inbound and outbound >>> spokes. Do small wheels (think recumbent) usually use the same hubs as >>> diamond frame bikes? If so, do they have a much higher incidence of >>> spoke breakage? >>> >> >>if you want to demonstrate something dave, do the math for the spoke >>angle given that a hub hole may be larger diameter than the spoke and >>seated in a flange of given thickness. then compare that to the stock >>spoke angle of ~95°. > > >I think I saw those calculations a while ago - it was in a book called >"The Bicycle Wheel", I think. Dear J., Here's Jobst's diagram in "The Bicycle Wheel," for anyone curious about specifics, as opposed to the rhetorical questions and why-don't-you-look-it-up so common on RBT: http://i12.tinypic.com/2dako69.jpg Jobst's diagram shows spoke angles from hub to rim of 7.3 and 3.5 degrees. So a slightly widened 95-degree elbow angle is reasonable for inner spokes that may be at 97.3~93.5 degrees. (Various front and rear hub widths probably don't change the angles much for 700c cross-3 wheels. Spoke elbows on tiny wheels for Moultons and recumbents may suffer from the orthopedic problems that afflict many dwarves, but small rims usually make very strong wheels.) Jobst recommends bending outer spokes enough to lie flat on the hub flange (and bending all spokes enough at the rim to "correct the spoke line.") Sapim disagrees. Here's their FAQ comment on 95 degree elbow angles and whether spokes should be bent ("forced") to change the angle: "If material is forced while lacing the hub, the spokes can be pulled over causing material weakness." "The original bend angle of 95° should remain intact." http://www.sapim.be/index.php?st=fa Elsewhere in "The Bicycle Wheel," Jobst mentions that steel spokes will bed into aluminum hubs, which have largely replaced the steel hubs that were popular when his first edition came out: "When spokes are properly tensioned the aluminum flange material on which they bear is usually under enough stress to conform to the spokes." --p. 59, "The Bicycle Wheel," 3rd edition, Jobst Brandt There's a good drawing of a "Spoke Seating in the Flange" next to the text quoted above (and oodles more interesting stuff, such as correcting the spoke line), but anyone interested will need to get their own copy . . . http://sheldonbrown.com/harris/books.html#brandt Cheers, Carl Fogel                     Date: 06 Dec 2006 20:41:45 From: jim beam Subject: Re: I fixed a broken spoke! carlfogel@comcast.net wrote: > On Wed, 06 Dec 2006 11:36:01 GMT, jtaylor@NOSPAM.hfx.andara.com wrote: > >> On Tue, 05 Dec 2006 20:23:10 -0800, jim beam >> <spamvortex@bad.example.net> wrote: >> >> >>>> In bound vs. out bound, crossing pattern, and rim size all >>>> affect the angle in question. I don't see hubs keted for each >>>> variation, and I don't see holes labeled for inbound and outbound >>>> spokes. Do small wheels (think recumbent) usually use the same hubs as >>>> diamond frame bikes? If so, do they have a much higher incidence of >>>> spoke breakage? >>>> >>> if you want to demonstrate something dave, do the math for the spoke >>> angle given that a hub hole may be larger diameter than the spoke and >>> seated in a flange of given thickness. then compare that to the stock >>> spoke angle of ~95�. >> >> I think I saw those calculations a while ago - it was in a book called >> "The Bicycle Wheel", I think. > > Dear J., > > Here's Jobst's diagram in "The Bicycle Wheel," for anyone curious > about specifics, as opposed to the rhetorical questions and > why-don't-you-look-it-up so common on RBT: > > http://i12.tinypic.com/2dako69.jpg thanks carl, but that's not what i was trying to describe - i was talking about the angle that results from having a 2.0mm spoke in a 2.4mm hub hole for a 3.4mm flange thickness. > > Jobst's diagram shows spoke angles from hub to rim of 7.3 and 3.5 > degrees. which is how the hub is canted. > > So a slightly widened 95-degree elbow angle is reasonable for inner > spokes that may be at 97.3~93.5 degrees. if the hub flange is canted, the spoke angle is from the point raised for the spoke not sitting square in the larger hub hole, not from the angle associated with flange spacing. > > (Various front and rear hub widths probably don't change the angles > much for 700c cross-3 wheels. Spoke elbows on tiny wheels for Moultons > and recumbents may suffer from the orthopedic problems that afflict > many dwarves, but small rims usually make very strong wheels.) > > Jobst recommends bending outer spokes enough to lie flat on the hub > flange (and bending all spokes enough at the rim to "correct the spoke > line.") > > Sapim disagrees. Here's their FAQ comment on 95 degree elbow angles > and whether spokes should be bent ("forced") to change the angle: > > "If material is forced while lacing the hub, the spokes can be pulled > over causing material weakness." > > "The original bend angle of 95� should remain intact." > > http://www.sapim.be/index.php?st=fa > > Elsewhere in "The Bicycle Wheel," Jobst mentions that steel spokes > will bed into aluminum hubs, which have largely replaced the steel > hubs that were popular when his first edition came out: > > "When spokes are properly tensioned the aluminum flange material on > which they bear is usually under enough stress to conform to the > spokes." --p. 59, "The Bicycle Wheel," 3rd edition, Jobst Brandt they do indeed. http://www.flickr.com/photos/38636024@N00/104463818/ > > There's a good drawing of a "Spoke Seating in the Flange" next to the > text quoted above (and oodles more interesting stuff, such as > correcting the spoke line), but anyone interested will need to get > their own copy . . . > > http://sheldonbrown.com/harris/books.html#brandt > > Cheers, > > Carl Fogel                       Date: 22 Dec 2006 23:04:08 From: Ron Ruff Subject: Re: I fixed a broken spoke! jobst.brandt@stanfordalumni.org wrote: > All > editions have the deflection diagrams of wheel deflections under load, > braking and drive and combinations of each, the numerical values for > which are in the appendix. Take a look. It isn't much. jobst.brandt@stanfordalumni.org wrote: > both sides of the wheel (left and right spokes) to transmit drive. All > editions have the deflection diagrams of wheel deflections under load, > braking and drive and combinations of each, the numerical values for > which are in the appendix. Take a look. It isn't much. Sorry... thought you were talking about diagrams of tension changes. I am familiar with those charts and diagrams, but I'm having difficulty infering spoke tension from them. You list rim deflections as radial, tangential, and rotational... but I'm having a tough time figuring what tangential vs rotational means. Since it is a 2d model I would expect only 2 values to define node locations. At first I thought that "rotational" was just another way of showing the "tangential" change, but the values don't square with that idea, because the tangential displacements are consistently ~1mm but the radial deflections vary from .0026 to .0043 radians... which I guess averages out to about the same thing (1mm= .0033 radians or .19 degrees), so maybe that *is* what it means. Also, the hub radius is never given... and I'm not sure what units "torque=50" are in... though m-kg would be my first guess. That *would* be a lot of torque. But the size of your deflection values makes me think that it is N-m or something else. Total torque is equal to the tension change x the number of spokes x the effective flange radius. If you were using a 21mm flange, 18 spokes, 50,000 kg-mm torque, we have: dT= 50,000/21/18 = +-132 kg... and that is a lot. A lot more than what is suggested by the deflection values in the chart. However, on pages 64-65 you discuss flange diameter and torsional stiffness of a wheel. There you give some values and conclude that it would take a 250kg force at the crank to produce a 1 degree rotation of the hub. If I plug your values into my equation, I get: Effective flange radius (mm) 21 (assumed from other examples) Crank length (mm) 170 Front sprocket teeth 34 (you say 2 to 1 ratio) Rear sprocket teeth 17 Crossed spokes on drive side 18 (assumed from other examples) Force exerted on crank (kg) 250 Spoke diameter (mm) 1.6 (assumed from other examples) Spoke length (mm) 280 (assumed) Spoke area (mm^2) 2.01 Spoke tension change (kg) 56.2 Spoke length change (mm) 0.37 Incidentally, a spoke length change of 0.37 mm with a radius of 21mm is 1.01 degrees... so at least this example indicates that we are in close agreement. Going back to the chart at the end of the book (Fig 73), if you are only getting a rotational change of .0033 radians (0.19 degrees) this would indicate a tension change of only 10.6kg... or a torque of 4.0 kg-m at the wheel... or a force of 47kg at the crank... assuming that the configuration of the wheel in these two examples is the same. So... I'm confused. And as for the unlikeliness of a wheel with only 10 spokes taking torsional loads, here is one that only has 6... looks like a small effective flange radius as well: http://cgi.ebay.com/shamal-campagnolo-wheelset_W0QQitemZ270070197330QQihZ017QQcategoryZ58099QQrdZ1QQcmdZViewItem And... yes, I am wondering how that wheel would hold up during stomping uphill sprints... If I'm making some calculation errors I'd like to know what they are...                         Date: 23 Dec 2006 18:09:31 From: Subject: Re: I fixed a broken spoke! Ron Ruff writes: >> All editions have the deflection diagrams of wheel deflections >> under load, braking and drive and combinations of each, the >> numerical values for which are in the appendix. Take a look. It >> isn't much. >> Most of those wheels have a sufficiently large center piece to >> cause both sides of the wheel (left and right spokes) to transmit >> drive. All editions have the deflection diagrams of wheel >> deflections under load, braking and drive and combinations of each, >> the numerical values for which are in the appendix. Take a look. >> It isn't much. > Sorry... thought you were talking about diagrams of tension > changes. I am familiar with those charts and diagrams, but I'm > having difficulty inferring spoke tension from them. You list rim > deflections as radial, tangential, and rotational... but I'm having > a tough time figuring what tangential vs rotational means. Since it > is a 2d model I would expect only 2 values to define node locations. > At first I thought that "rotational" was just another way of showing > the "tangential" change, but the values don't square with that idea, > because the tangential displacements are consistently ~1mm but the > radial deflections vary from .0026 to .0043 radians... which I > guess averages out to about the same thing (1mm= .0033 radians or > .19 degrees), so maybe that *is* what it means. The diagrams and data are in radial and tangential dimensions. Spoke tension changes can be derived from cross section and length change, all of which are given. For finite element analysis, spokes do not need to have any pre-tension, they are elastic elements. There is a diagram showing a wheel with spoke tension and its effect on rim diameter. All deflections in the diagrams are uniformly enlarged, the true values being in the numerical tables. > Also, the hub radius is never given... and I'm not sure what units > "torque=50" are in... though m-kg would be my first guess. That > *would* be a lot of torque. But the size of your deflection values > makes me think that it is N-m or something else. Total torque is > equal to the tension change x the number of spokes x the effective > flange radius. If you were using a 21mm flange, 18 spokes, 50,000 > kg-mm torque, we have: > dT= 50,000/21/18 = +-132 kg... and that is a lot. A lot more than > what is suggested by the deflection values in the chart. This is about effects not absolute quantities. As I mentioned the vectors shown are all the same size, braking, torque, and radial load. I think the data and diagrams are clearly ked, considering all the reviews by engineers that were made before publishing. > However, on pages 64-65 you discuss flange diameter and torsional > stiffness of a wheel. There you give some values and conclude that > it would take a 250kg force at the crank to produce a 1 degree > rotation of the hub. If I plug your values into my equation, I get: > Effective flange radius (mm) 21 (assumed from other examples) Crank > length (mm) 170 Front sprocket teeth 34 (you say 2 to 1 ratio) Rear > sprocket teeth 17 Crossed spokes on drive side 18 (assumed from > other examples) Force exerted on crank (kg) 250 Spoke diameter (mm) > 1.6 (assumed from other examples) Spoke length (mm) 280 (assumed) > Spoke area (mm^2) 2.01 > Spoke tension change (kg) 56.2 Spoke length change (mm) 0.37 > Incidentally, a spoke length change of 0.37 mm with a radius of 21mm > is 1.01 degrees... so at least this example indicates that we are > in close agreement. The loads are introduced at the road contact. There is no chain or pedals. Just lock the wheel to the center and apply the loads shown. That way you don't get caught in sprockets, chain, cranks and rider strength. > Going back to the chart at the end of the book (Fig 73), if you are > only getting a rotational change of .0033 radians (0.19 degrees) > this would indicate a tension change of only 10.6kg... or a torque > of 4.0 kg-m at the wheel... or a force of 47kg at the crank... > assuming that the configuration of the wheel in these two examples > is the same. So... I'm confused. You can deduce that from the cross section and elongation of the spoke as well. Yes, there is little change, as I said. Radial load is by far the greatest spoke load change in operation. Al the other forces make little difference. > And as for the unlikeliness of a wheel with only 10 spokes taking > torsional loads, here is one that only has 6... looks like a small > effective flange radius as well: http://tinyurl.com/ym2uxd We also have Tri-Spoke. > And... yes, I am wondering how that wheel would hold up during > stomping uphill sprints... That isn't its problem. It's the radial load deflection that counts. > If I'm making some calculation errors I'd like to know what they are... I think you should review the diagrams and numbers in the book that explain the relationships. Jobst Brandt         Date: 04 Dec 2006 23:23:20 From: Subject: Re: I fixed a broken spoke! someone writes: >>> If you are breaking non-drive side spokes, this indicates without >>> a doubt that they are crap spokes. (based on info from your >>> previous posts, that you don't weigh 400lbs,etc) >> Even the best spokes fail if they are not formed to the hub and >> stress relieved. Don't push it off on the spoke manufacturer when >> it's the builder who needs to take measures to make the wheel >> durable. > Stress relief is just going around the wheel sort of pinching the > spokes? There's more to it than that, but yes. A better method of stress relief is to stand the wheel on its axle and press down on the rim with hands diametrically opposite, once between each pair of spokes. However, first the outbound spokes must be manually bent to lie flush against the flange. Then by grasping pairs of spokes on opposite sides of the wheel and squeezing them together will make sure that your wheel is not too tight. Jobst Brandt   Date: 04 Dec 2006 12:26:44 From: Subject: Re: I fixed a broken spoke! dgk wrote: > Which correctly implies that I broke another one. I got lucky; this > one was not on the drive side. So I took a spoke from a retired wheel > (rear wheel same bike) and replaced the broken one using the same > pattern as the nearby spokes. > > Once I put the wheel on the bike I was able to true it pretty well by > seeing how that section passed the brakes. A few twists and it kept > the same distance as the rest of the wheel. It rode fine this morning. > > I was just on the SheldonBrown site looking at freehubs, and it looks > easy enough to remove the cassette. I think I'll almost look forward > to the next broken spoke so I have an excuse to remove the cassette. > It's almost sure to be on the drive side. > > Do I have to be concerned about Dish? It seems that if the rest of the > wheel is correct and this one spoke has been adjusted so that the rim > is straight, then the dish is correct? Way to go! Soon you'll be building your own wheels! Dish cannot be changed by one spoke. It is regulated by the average tension difference between sides. That means the drive side is usually a lot tighter to pull the rim that way, instead of having it centered between the flanges, as on a front wheel (which has even tension, and thus no dish.) The cassette tool is a good one to have. Joseph