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Old 2016-05-23, 05:32 AM   #16
kamikaze
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Quote:
Originally Posted by harper View Post
They just don't want you to put a flat, fully deflated tube in the tire to mount it. It's easier when it is very slightly inflated and has a more or less round cross section. They just list 0.5 psi to get you to put some air in it to make it easier on yourself. Anyway, you're a clever guy with access to lots of stuff. You could borrow a Wallace and Tiernan pressure gauge from a lab in Karlsruhe and easily measure the 1.034 bar within a couple percent.
Intelligent, but not so clever.

I put the uninflated tube on the rim and inflated it to 1.5 bar. Then I kneaded it through and moved it around until the valve stuck out of the hole centred and I was confident the tension was pretty even. Inflate a bit more, repeat, a couple of times.

The interesting bit is that for a long stretch the pressure just stays the same. With every push on the pump the tyre is expanded permanently (instead of elastic stretching like a regular tube). That changes once the tube starts pressing against the walls.
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Old 2016-06-23, 05:45 PM   #17
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I tuned the spoke tension to just below 110 kg.

Now, one month later, I checked the assembled wheel. And the same tension meter tells me my spokes are down to just below 80 kg of force.

I know the tube kind of compresses the rim, but I wouldn't expect that effect to be big enough to even measure with that tool. What happened, where is my force?

I think 80 kg is certainly not enough. By now the wheel is back to creaking as much as it used to. Do I need to use loctite?
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Old 2016-06-23, 07:56 PM   #18
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Stainless steel spokes stretch. (Nice alliteration, that.) Zinc coated steel spokes don't stretch so much but they're pretty hard to come by.

The tube and tire can't exert anywhere near as much force as the spokes. There are 32 to 40 spokes and each one is exerting 60-100 kg-force on the rim.
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Old 2016-06-23, 09:03 PM   #19
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110kgf should be plenty to keep the spokes from becoming slack during riding. Most rims are rated to around 120kgf anymore, and the recommendation is generally to keep the tension between 110-120. For any specific rim you need to check with the manufacturer, but these numbers seem pretty consistent.

I wonder if you had twisted spokes, and as you rode the spokes untwisted without the nipple moving thereby loosening. That is a dramatic difference between the "set" tension, and the tension after riding. I don't think it is close enough to be explained by spoke stretch. Maybe though. It is hard to say anything more than speculation without having the wheel in front of me.
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Old 2016-06-23, 09:21 PM   #20
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What surprises me is that the effect spread so evenly.
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Old 2016-06-23, 09:30 PM   #21
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Originally Posted by kamikaze View Post
What surprises me is that the effect spread so evenly.
Yeah, that's strange. It almost seems like it might be the tool since it would only be one thing that would have to be off to explain the 36 other things.
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Old 2016-06-24, 05:43 AM   #22
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Originally Posted by jtrops View Post
Yeah, that's strange. It almost seems like it might be the tool since it would only be one thing that would have to be off to explain the 36 other things.
I wish I had a spare spoke. I could tension it with ~1 kN to calibrate the tool.

On a friends bicycle the tool shows reasonable values between 110 and 120 kg.
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Old 2016-06-25, 08:48 AM   #23
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I took a couple of samples, reducing the tyre pressure. A pressure drop of 200kPa resulted in a 3 to 8 kg increase in tension. So the effect is significant, but does not explain it all.

So I upped the tension, this time with the tyre installed (200 kPa above atmospheric pressure). Which resulted in a wheel a lot less true. I put some work into truing it and increased the pressure again, in two steps to my desired 400 kPa above atmosphere.

The tension seems reasonable, now. The wheel is just true enough to be bearable. On the test ride the wheel felt much stiffer (good), but the creaking returned with the first turn. And it stayed (bad).

I think I'll give it up, just true the wheel and lubricate the spokes.
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Old 2016-06-25, 02:37 PM   #24
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I believe that I read in Jobst Brandt's book that an inflated tire can have a 5 to 10 percent effect on spoke tension. I don't remember the number specifically but he did acknowledge that.
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Old 2016-06-29, 02:20 AM   #25
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Originally Posted by kamikaze View Post
I think evening the tension was really necessary and I couldn't have done it without the tension meter.
I know that "tuning spokes" by it's sound is not entirely accurate to have equal tentsion.
I pretty much have all wheel building tools, but not a tension meter.
Therefor I'm curious when you listen to your spokes is there much (unexpected) difference in tone levels?
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Old 2016-06-29, 07:28 AM   #26
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Quote:
Originally Posted by leo View Post
I know that "tuning spokes" by it's sound is not entirely accurate to have equal tentsion.
I pretty much have all wheel building tools, but not a tension meter.
Therefor I'm curious when you listen to your spokes is there much (unexpected) difference in tone levels?
No, it's kind of the opposite. There is only little tone difference for huge tension differences.

Any way, after reading about twisted spokes I spent another 4 or so hours retensioning all spokes putting some lubricant on the threads. This time I made it 200 metres before the first noise and 600 metres before the annoying persistent noise returned. Which is about 10 times the distance I covered last time, before my work proved futile.

I wonder, do the spokes just unwind? Do I need to use loctite? Or did the wheel builder maybe not stress relieve the spokes?

I have talked to some people who built wheels and when I asked them about stress relieving they told me they've never done that.

How do I determine the wheel was built properly?
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Old 2016-06-29, 01:25 PM   #27
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Quote:
Originally Posted by kamikaze View Post
No, it's kind of the opposite. There is only little tone difference for huge tension differences.

Any way, after reading about twisted spokes I spent another 4 or so hours retensioning all spokes putting some lubricant on the threads. This time I made it 200 metres before the first noise and 600 metres before the annoying persistent noise returned. Which is about 10 times the distance I covered last time, before my work proved futile.

I wonder, do the spokes just unwind? Do I need to use loctite? Or did the wheel builder maybe not stress relieve the spokes?

I have talked to some people who built wheels and when I asked them about stress relieving they told me they've never done that.

How do I determine the wheel was built properly?
Don't use loctite on nipples! It is too strong for such fine threads, and if there's enough tension it shouldn't be needed anyway. I use boiled linseed oil to prep my spokes. It acts as a mild thread lock, and anti-seize after it cures. As a lube it benefits the initial build, but it persists after the oil has cured as well. I have never had a seized nipple on a spoke that was prepped with it.

I don't know why it's called "stress relieving," but I don't know any wheel builders who don't do it. It is really setting the spokes, and nipples so that everything is in its proper place at rest. Then when you bring it up to tension all of the force is exerted in a straight path between the rim and hub. If you don't do it there is wasted energy in having to straighten everything out. It is uneven, and as the spokes "set" themselves it will introduce slack into the system. The result at best is an out of true wheel, and at worst is a wheel that lets the nipples unwind.

I guess there is a difference between people who have built wheels, and a wheel builder.

As for determining a good wheel build, I don't know how you could tell. If it is a machine built wheel the lacing is fine, but it probably wasn't "stress relieved." I would detention the wheel, and treat it as a new build that is already laced. Take the slack out of the spokes so that the tension is still low, and use my nipple driver between each crossed pair to bend the spokes around each othe slightly. I also use a small plastic hammer to tap the outside heads establishing a little tighter bend in the elbows. This is simple, and fast, and removes many problems later on. There are more things you can do to relieve tension, but these two things probably make the biggest impact.

Then bring the tension up a bit so that it is still low, but the wheel feels solid for the most part, maybe 60-80kgf (I've never gauged it). This is when you dish and true the wheel. Finally bring it up to final tension. At this point you shouldn't need to do more than minor adjustments for trueness, and the dish should still be good.

As you turn the nipples you can get a feel for when you are winding the spoke. If you feel the spoke wind a quarter turn before the nipple starts tightening, then unwind that same quarter turn when you are done. This becomes intuitive. You can also use spoke pliers if you need to keep the spokes from winding up, but I only use them on very light spokes like Lasers.

That should get you a strong wheel.
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Old 2016-06-29, 01:43 PM   #28
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Quote:
Originally Posted by jtrops View Post
I don't know why it's called "stress relieving," but I don't know any wheel builders who don't do it. It is really setting the spokes, and nipples so that everything is in its proper place at rest. Then when you bring it up to tension all of the force is exerted in a straight path between the rim and hub.
There's this link floating around the forums:
http://sheldonbrown.com/brandt/stress-relieving.html

I quote:
Quote:
It is not done to bed the spokes into the hub, as is often stated. Bedding-in occurs sufficiently from tension.
I don't know how credible the source is, though.
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Old 2016-06-29, 01:57 PM   #29
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Originally Posted by kamikaze View Post
There's this link floating around the forums:
http://sheldonbrown.com/brandt/stress-relieving.html

I quote:


I don't know how credible the source is, though.
This is different than what we are talking about. Bedding the heads into the hub doesn't matter for the reason you quoted. I've built wheels where I took time to set each head with a center punch just to see if there was any difference, and in the end the wheels were as strong as any others I had built.
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Old 2016-06-29, 02:24 PM   #30
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Quote:
Originally Posted by jtrops View Post
This is different than what we are talking about. Bedding the heads into the hub doesn't matter for the reason you quoted. I've built wheels where I took time to set each head with a center punch just to see if there was any difference, and in the end the wheels were as strong as any others I had built.
OK, I have to admit I struggle with the wheel building lingua. My imagination comes short when reading about it. The picture in my head is an old dude who has built racing wheels his entire life, bending the spokes with a spoon handle where they meet.

But I have no idea about a lot of details, like how are the spokes anchored? Are they already suspended from the hub? Are they already connected to the rim? But how do I "grab and yank" them?

I probably should just watch one of those youtube tutorials, though I hate learning from videos. Most videos are done by hacks who teach you bullshit and I don't like not going through it at my own pace.
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