#31
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Spoke stress
Jobst Brandt wrote:
Over the years that I have been building wheels I have heard no untwisting sounds because I use an over-shoot-and-back-off method to adjust spokes. Readers of "the Bicycle Wheel" know how to do that as well, it being mentioned in the book under "Spoke Twist". I've used the over-shoot-and-back-off method of spoke adjustment for years (decades), but I've had trouble doing that with very thin spokes. The amount of wind-up varies from spoke to spoke, and even varies on the same spoke as it is tensioned. This variability makes it hard to guess correctly how much to back off each nipple. I've built thin spoke wheels using both the over-shoot-and-back-off and the hold-spoke-while-adjusting method. The second method is more reliable, I never get the charcteristic "ping, ping" of untwisting spokes after using this method. Not so with over-shoot-and-back-off. -- terry morse - Undiscovered Country Tours - http://www.udctours.com/ |
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#32
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Spoke stress
Terry Morse writes:
Over the years that I have been building wheels I have heard no untwisting sounds because I use an over-shoot-and-back-off method to adjust spokes. Readers of "the Bicycle Wheel" know how to do that as well, it being mentioned in the book under "Spoke Twist". I've used the over-shoot-and-back-off method of spoke adjustment for years (decades), but I've had trouble doing that with very thin spokes. The amount of wind-up varies from spoke to spoke, and even varies on the same spoke as it is tensioned. This variability makes it hard to guess correctly how much to back off each nipple. I've built thin spoke wheels using both the over-shoot-and-back-off and the hold-spoke-while-adjusting method. The second method is more reliable, I never get the characteristic "ping, ping" of untwisting spokes after using this method. Not so with over-shoot-and-back-off. There's a fine sense way of assessing windup by feeling the torque when tightening and loosening a tight spoke. (Only the final tightening counts.) A tight spoke will begin to twist and then break loose when it has built up enough torque to make the thread move. This can be felt and it is different for tightening and loosening because one is uphill, so to speak, and the other is down the thread ramp. This break loose point is difficult to feel if the spoke nipple to rim interface is not well lubricated. I suspect most people do not pay attention to that aspect or we wouldn't have spoke wrenches that are in essence slotted four sided socket wrenches. With my hardened steel, slotted spoke wrenches, I can twist off any spoke I have met yet do not round off spoke nipples. That dry cork sound I often hear when I see wheels being built in bicycle shops is a sure sign that the brass spoke nipple is galling. Jobst Brandt |
#33
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Spoke stress
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#34
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Spoke stress
Terry Morse wrote:
I've used the over-shoot-and-back-off method of spoke adjustment for years (decades), but I've had trouble doing that with very thin spokes. The amount of wind-up varies from spoke to spoke, and even varies on the same spoke as it is tensioned. This variability makes it hard to guess correctly how much to back off each nipple. I've built thin spoke wheels using both the over-shoot-and-back-off and the hold-spoke-while-adjusting method. The second method is more reliable, I never get the charcteristic "ping, ping" of untwisting spokes after using this method. Not so with over-shoot-and-back-off. Terry, Besides the "hold-spoke-while-adjusting method" you mention, the variability can be eliminated by marking the spokes, as described he http://groups.google.com/group/rec.b...4b972918e1096f Even after building several wheels and developing a "feel" for windup, I still find it helpful to do this. The only cost is the ~90 seconds it takes to apply the marks. I've never tried the "hold-spoke-while-adjusting method", but I suspect it requires more work than simply marking them. Best, Stephen Greenwood |
#35
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Spoke stress
In article
, Tim McNamara wrote: In article , jim beam wrote: Tim McNamara wrote: In article , "PWNMAN" wrote: wrote in message ... I believe the misunderstanding about stresses that case spoke failures arises because spoke stress is invisible and not easily measured. Your integrity is invisible and not easily measured also! Integrity is measured over time. I find it easy to draw conclusions about the integrity of the participants in this forum after 13 years or so of participation. so repetition of an error for a prolonged period makes it not an error? that's interesting. No. If that were true, then you'd have integrity. Left himself wide open for that one. Some people do not think ahead. It is not only that he does not hearken to what is said to him, he does not even parse what is said to him. -- Michael Press |
#36
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Spoke stress
Stephen Greenwood writes:
I've used the over-shoot-and-back-off method of spoke adjustment for years (decades), but I've had trouble doing that with very thin spokes. The amount of wind-up varies from spoke to spoke, and even varies on the same spoke as it is tensioned. This variability makes it hard to guess correctly how much to back off each nipple. I've built thin spoke wheels using both the over-shoot-and-back-off and the hold-spoke-while-adjusting method. The second method is more reliable, I never get the characteristic "ping, ping" of untwisting spokes after using this method. Not so with over-shoot-and-back-off. Besides the "hold-spoke-while-adjusting method" you mention, the variability can be eliminated by marking the spokes, as described he http://groups.google.com/group/rec.b...4b972918e1096f Even after building several wheels and developing a "feel" for windup, I still find it helpful to do this. The only cost is the ~90 seconds it takes to apply the marks. I've never tried the "hold-spoke-while-adjusting method", but I suspect it requires more work than simply marking them. I also used the marking method and that is how I discovered how poorly holding spokes with pliers works. As I said, I do fine with backing off. The test of the method is to coast standing on one pedal while leaning far to either side. That puts a smooth side load on the wheel that nearly slacken the spokes. Jobst Brandt |
#37
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Spoke stress
jim beam wrote:
wrote: Spoke windup was such a severe problem on early machines that it limited the ability to reach high tension, something that was brought to a head with fewer spokes that requires higher tension. It was the tension limit, caused by spoke windup, that gave machine built wheels a bad name, and it has, to a degree, stuck. btw, can you please explain exactly how the torsional elasticity of a spoke changes with tension? I think it's clear that spoke windup increases with tension due to static friction between spoke and nipple, and not to a change in the properties of the spoke itself. Is the latter what you are suggesting? Chalo |
#38
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Spoke stress
Stephen Greenwood wrote:
Besides the "hold-spoke-while-adjusting method" you mention, the variability can be eliminated by marking the spokes, as described he http://groups.google.com/group/rec.b...4b972918e1096f Even after building several wheels and developing a "feel" for windup, I still find it helpful to do this. The only cost is the ~90 seconds it takes to apply the marks. I've never tried the "hold-spoke-while-adjusting method", but I suspect it requires more work than simply marking them. Thanks, I haven't tried the "mark the spokes" method in quite a while. Maybe I'll try that on my mext wheel. For holding the spokes, I have purchased the Twist Resist tool: http://www.sheldonbrown.com/harris/tools/wheel.html It's fairly easy to use and does the job. |
#39
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Spoke stress
Chalo wrote:
jim beam wrote: wrote: Spoke windup was such a severe problem on early machines that it limited the ability to reach high tension, something that was brought to a head with fewer spokes that requires higher tension. It was the tension limit, caused by spoke windup, that gave machine built wheels a bad name, and it has, to a degree, stuck. btw, can you please explain exactly how the torsional elasticity of a spoke changes with tension? I think it's clear that spoke windup increases with tension due to static friction between spoke and nipple, and not to a change in the properties of the spoke itself. Is the latter what you are suggesting? Chalo you got it right, the spoke properties don't change, just the friction. |
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