Non wheel builders - what's in your wheel maintenance toolkit?
07-27-20, 10:23 PM
#26
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Yes, an overtensioned wheel will crack due to exceeding the yield strength but it’s not something the happens immediately. It happens due to flexion of the metal of the rim through numerous loading and unloading cycles.
You might make an argument (in a bar near an engineering school late at night) that an undertensioned rim might detenion during unloading at the bottom of the wheel's rotation. In practice the spoke breaks because of cyclic detensioning rather than the rim breaking because of flexion.
I'm afraid that's nowhere near the first manufacturer's customer service rep that doesn't know what they're talking about.
*I’ve had a little bit of interaction with Velocity and the people who answer the phone aren’t exactly stupid.
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Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Last edited by cyccommute; 07-27-20 at 10:27 PM.
07-27-20, 10:29 PM
#27
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You are correct there but the difference in tension between sides on a front disc wheel are relatively small. They might even be in the error of the measurement. That’s largely because there is a lot of error in tension measurements.
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Plan Epsilon Around Lake Michigan in the era of Covid
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Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
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Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
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07-28-20, 04:30 AM
#28
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From DT Swiss. Having spent a couple yrs in Switzerland I wouldn't want to mess with the foreman (forewoman?) in the background. I don't see little hammers being used to check spoke tension
07-28-20, 04:35 AM
#29
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07-28-20, 01:45 PM
#30
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Every wheel undergoes a decrease in tension above the contact patch. There is nothing that stops any rim from doing that. If the spoke were under compression, you could are your argument but the spoke isn’t under compression. It is only under tension. Wheels will undergo spoke unloading from simply inflating a tire.
Yes, an overtensioned wheel will crack due to exceeding the yield strength but it’s not something the happens immediately. It happens due to flexion of the metal of the rim through numerous loading and unloading cycles.
It happens in both practice and theory.
Yes, an overtensioned wheel will crack due to exceeding the yield strength but it’s not something the happens immediately. It happens due to flexion of the metal of the rim through numerous loading and unloading cycles.
It happens in both practice and theory.
As far as time to failure, I haven't seen any references to either "new" or "after X miles."
You really can't compress a spoke (except in the mathematical sense). I've never failed to plastically buckle a spoke when I tried to compress one -- although I've nearly poked a hole in my hand!
Neither you nor I have seen the rim. We can’t tell if the spokes were tight or not. Nor do you know who at Velocity looked at the wheel. Finally, TheCharm said that the wheelbuilder agreed with Velocity. That says to me that is isn’t just someone who answers the phone at Velocity* that is making the determination.
*I’ve had a little bit of interaction with Velocity and the people who answer the phone aren’t exactly stupid.
*I’ve had a little bit of interaction with Velocity and the people who answer the phone aren’t exactly stupid.
Perhaps you've seen an under-tensioned spoke crack a rim? I haven't, and I've fixed a bunch of broken spokes -- almost all from under-tensioning. That's why I made the comment about late night in a bar -- I can make the argument it might fatigue and crack the rim, but I've never seen it. Rims do fail when they're over-tensioned. I'd believe poor manufacturing or corrosion, even though there's no evidence in the picture for either, before I'd believe under-tensioning. If it walks like a duck and quacks like a duck, etc. That's why I suspect over tensioning.
.
07-29-20, 10:04 AM
#31
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I think I see the cause of the confusion. You seem to be thinking tension cycling between (for instance) 100 kgf and 80 kgf will fatigue the material. But to cause metal fatigue, you have to cycle between tension (or compression) and zero (unloaded), or from tension to compression and back.
As far as time to failure, I haven't seen any references to either "new" or "after X miles."
You really can't compress a spoke (except in the mathematical sense). I've never failed to plastically buckle a spoke when I tried to compress one -- although I've nearly poked a hole in my hand!
As far as time to failure, I haven't seen any references to either "new" or "after X miles."
You really can't compress a spoke (except in the mathematical sense). I've never failed to plastically buckle a spoke when I tried to compress one -- although I've nearly poked a hole in my hand!
I agree that there is no compression on the spoke...and that's a large part of why the rim flexes. There is nothing holding the rim to the spoke except tension. Reduce the tension and the rim rides up on the spoke nipple...even just a little. Then the rim unloads and pulls back down on the spoke nipple. That flexes the aluminum around the nipple constantly. Loose spokes flex more so the rim could be prone to cracking in both low tension and high tension regimes.
If someone at Velocity looked at the wheel itself, I missed the reference. I agree you can't tell from the picture (and may I complement the OP, this is excellent photography and far above what's usually posted to the forum!) what the tension of the spoke was.
Perhaps you've seen an under-tensioned spoke crack a rim? I haven't, and I've fixed a bunch of broken spokes -- almost all from under-tensioning. That's why I made the comment about late night in a bar -- I can make the argument it might fatigue and crack the rim, but I've never seen it. Rims do fail when they're over-tensioned. I'd believe poor manufacturing or corrosion, even though there's no evidence in the picture for either, before I'd believe under-tensioning. If it walks like a duck and quacks like a duck, etc. That's why I suspect over tensioning.
.
Perhaps you've seen an under-tensioned spoke crack a rim? I haven't, and I've fixed a bunch of broken spokes -- almost all from under-tensioning. That's why I made the comment about late night in a bar -- I can make the argument it might fatigue and crack the rim, but I've never seen it. Rims do fail when they're over-tensioned. I'd believe poor manufacturing or corrosion, even though there's no evidence in the picture for either, before I'd believe under-tensioning. If it walks like a duck and quacks like a duck, etc. That's why I suspect over tensioning.
.
I have seen cracks on wheels that had very low tension as well as high tension. Both take a while.
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Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
07-29-20, 10:12 AM
#32
Full Member
Learn to build your own wheels.
Use a $5 cell phone app if you need to verify absolute tension. Input gauge and unsupported span. Pluck a spoke. The app will use a fast fourier transform to convert time to frequency domain, then the dominant frequency to tension.
You can hear the difference between spokes.
Use a $5 cell phone app if you need to verify absolute tension. Input gauge and unsupported span. Pluck a spoke. The app will use a fast fourier transform to convert time to frequency domain, then the dominant frequency to tension.
You can hear the difference between spokes.
Thanks.
