dahoyle

There are a number of things. A spoke failure may be caused by constant stressing and de-stressing reaching it's fatigue life(unlikely in practice), it could be that it is tensioned too tightly, too close to the ultimate tensile strength of the spoke, or the rim, causing a mechanical failure of one or the other. It could be an incursion into the strength curve of the spoke where it yields(stretches beyond it's capacity to recover). In the case of a Taco, it can simply me a momentary incursion into regional tension where equilibrium is no longer maintained, and the wheel springs the opposite direction.

The reduced bracing angle in a highly dished wheel requires a much higher tension in the drive side spoke to maintain the equilibrium in comparison to the non drive side, and it is that elevated tension which leads to failure, not the fact that it is different from the other. In addition, any lateral force applied to the rim is multiplied by the number on the chart for any given angle. Therefore a force acting on the drive side has a higher effect on the spokes (guys) and rim(anchor) than the same force on the non drive side.

If you look at the chart, specifically at the curve or the multiplication factor, you can see how an increase in the angle leads to higher and higher loads, that are not linear with the change in angle.

This is not something I made up. It is basic physics. I had to search a while to find a specific chart detailing the curve, but that is not the only one.

You can also use the sling angle vs load chart to detail exactly the same principal.

it can be found on https://www.spanset-usa.com/SlingAngle.html. Also graphically detailed here https://www.tpub.com/content/engine/1.../14081_371.htm also here https://www.kwrs.com/syncpdfs/spdf07.pdf

I could look up the same data on various Govt sites, OSHA MSHA, etc but it is pointless if the information is sumarrily dismissed because it is contrary to what they have come to believe.

Panthers007

Here's the Sheldon Brown Wheel Stress-Gauge:

dahoyle

That statement is scientific fact. How about you come up with something supporting your argument, rather than continuously quoting the same site. How about some independent corroboration. Come on, one little tidbit would go a long way in establishing that you actually know something, rather than constantly quoting the same party line.

I want you to explain the principals that are in play to support your argument. Come on, a little analysis of your own, how hard can that be?

How exactly does a difference in tension create a weaker wheel? In the case of a dished wheel, it is exactly that difference in tension that makes it possible. Why is it the difference in tension, rather than the load angle. Please, I'm really slow, and am trying to understand. Can you actually explain it, or even think independently. If not, your opinion really has no value to me., because you are obviously not a subject matter expert.

Shimagnolo

Rather than re-inventing the wheel, why not just read the Jobst Brandt book?
He is a trained engineer and has done all the research.

dahoyle

There are many many trained engineers in the world. Some of them designed the Macinaw Narrows bridge.

Are you making that statement after looking at the data I provided, or are you just running with what you know?

Curious why one engineers word means so much to you, but you so readily discount all others.

His work is not without criticism.

Shimagnolo

Science and engineering build on the work of those who have come before.
You seem like a bright guy, but you seem to believe you can figure it all out just by thinking about it, and totally ignore the research that has already been done.
This is *mechanics*, and the same principles of physics that governed it 20 years ago still hold today.

dahoyle

And yet you seem so readily willing to discount the examples I show. Do you really think that they were just randomly selected by me? They are the accepted data developed by and used by engineers, and they relate directly to the forces in play in a bicycle wheel.

I AM NOT GUILTY OF JUST THINKING ABOUT IT. I am applying my knowledge of the forces in play including the various mathematical formulas which I believe are relevant. If you are interested, I am also trained in a different engineering discipline (electronic), as well as medicine and pharmacology, and have a 10 years experience as a Construction superintendent, dealing closely with mechanical and civil engineers. I can tell you that as often as not, they interpret the same problem differently and come up with widely varying opinions, and have often deferred to my experience, rather than their theoretical analysis. I am perfectly capable of advanced problem solving, and mathematics.

I will readily admit when I am wrong, as I demonstrated elsewhere in the thread.

I will not admit I am wrong, just because someone says I am. All you have to do is demonstrate what is wrong with my analysis, and that means you have to look at and discount the data I have provided. Since you are unable to do that, I take what you say with a grain of salt.

I will certainly obtain a copy of the book in question, so there is no reason to keep saying it. I actually try to increase my knowledge base, rather than some around here who think that one analysis is the final word.

rydaddy

It is not the higher tensioned spokes that make dished wheel weaker. It is the looser side. Higher tension is more desireable because it will cause a higher force to slacken a spoke, therefore it is stronger. If both sides are more balanced, the overall system will be stronger. Elevated tension is desireable (to a point).

Shimagnolo

I am not going to spend the time to act as an intermediary to provide someone information from a book they could pick up and read for themselves.
If you choose to stay ignorant of the best single source of information on this topic, that is not my problem.

Doug64

Hi guys,

What a discussion! It got me to wondering what are we really talking about. I went out and measured the flange width (outside to outside)Shimano LX hub on my wife's touring bike, and the flange width on my Tiagra rear hub. The LX = 58mm and the Tiagra=56mm. I could have been off a little, maybe +- 0.5mm. It seems like most of the difference between the 135 and 130mm dropouts is taken up by spacers not in the width of the hub. That is the point I think rydaddy made back at the beginning; a lot depends on the difference in the width between flanges. At this point I think 2mm is almost to the point of being academic as far as actual perfomance is concerned. I'm also thinking that the wider drop outs on Mountain and touring bikes are to facilitate the use of wider tires ( and maybe the wider bb shell, 68mm vs. 72mm), not necessarily provide a stronger wheel.

FYI I'm probably going with Ultegra 36 spoke hubs, Mavic 719 rims, and Wheelsmith straight guage 2.0mm spokes.

dahoyle

Obviously, you are somewhat deficient in reading skills, as well as analytical thinking. I specifically said I would pick up the book. I want to know what makes you qualified to judge what is the single best source of information. I have yet to hear any of your qualifications. Seriously, what engineering background do you have to provide a peer review on the work.

I didn't ask you to quote from the book, and in fact specifically requested that you come up with something new and refreshing. It is obvious that you cannot, and cannot do anything except quote from a book that you barely comprehend. You have not added one thing to the discussion.

dahoyle

No, 2 millimeters is certainly not academic, when it comes to the dish on a rear wheel. It is in fact, rather considerable, if it is on the drive side.

You may well be correct on why the hub width is more, on a mountain bike, but that doesn't mean there is no strength benefit. Tandem hubs have been growing for a long time, so that on the extreme end, they are now 160mm. This is to allow as wide a spacing as possible on the hub flanges, and still fit the optional drum brake and 10 speed cassettes.

Retro Grouch 

Please explain how you separate the two.

Hydrated

Guys... come on fer cryin' out loud. Dahoyle is obviously just some guy who is good at using Google to find websites with technical explanations. And you're all letting him get your goat.

And Dahoyle... we REAL engineers (I have a master's degree in engineering) don't waste our time debunking hacks who refuse to open their minds to another potential explanation.

To sum it all up:

dahoyle

Again, there is the argument about the slackened spoke, and again, I will reiterate the fact. A spoke cannot go slack without a deflection of the rim, in the case of this discussion about a dished hub, we are generally discussing a lateral deflection on the drive side. The steep angle on the drive side, creates a weakness all by itself.

By your explanation, all that would be required to make a stronger rear wheel would be to bring the non drive in closer to center, thereby allowing more equal tension. That is not what they do. They move the drive side out as far as possible, to obtain the best angle possible, thereby reducing, as much as possible, the likelihood of the failure.

Please explain why almost all spoke failures on a rear wheel occur on the drive side. I'll give you a clue. The ultimate tension strength of the spoke was surpassed, because of the increased load placed on the drive side by the increased tension placed on that side to maintain equilibrium, and the decreased ability of the spoke to respond to a load that is created by the poor angle. I am not going to go back into it, I have already provided data that demonstrates this principal. Please feel free to go back and read the charts. Before it reaches the point where it actually snaps, it might get to a point where it stretches, and does not return to it's original shape, and presto, you have your slack spoke. The cause, obviously the elevated tension on the drive side spoke.

dahoyle

No, it is actually pretty difficult to find real scientific data on the internet. It took quite some time to find something which supported the point I was trying to get across that I thought they might be able to comprehend. All things considered, it was rather pointless, since they were all so sure of their mental superiority(they read a book once) that none of them actually looked at it.

Retro Grouch 

On the other hand, it shouldn't take too much engineering time to explain to a dumb bike mechanic from Missouri how you separate spoke braceing angle and spoke tension.

dahoyle

You can't separate them. The point I was trying to make, is that it isn't the difference between left and right, it is the elevated tension on the drive side which creates problems. The increased tension is obviously in response to the reduced bracing angle. Careful here, you are coming very close to supporting my argument without knowing it.

Retro Grouch 

Cool, then how about this: Almost as soon as 8-speed cassettes came out I started encountering wheels with broken NDS spokes. They were much, much more frequent than broken drive side spokes. If the braceing angle were the end-all determining factor, I'd expect to see DS spokes breaking first. As I indicated previously, that wasn't the case in real life. I attributed the spoke failures to too little tension on the non-drive side. I increased the tension on the whole wheel and solved the problem.

I assume the 135 mm mountain bike dropout spacing was a response by the manufacturers to this problem.

rydaddy

DS spokes break because the wheel was poorly built to begin with. And they do not break because they are stressed to ultimate. That's just not true. It's due to fatigue, as a result of a poor build. The NDS spokes break more commonly because they go through more severe load cycles of loading and unloading.

Read the book.

urbanknight

Post #48 makes much sense to me, but I think there's more to it.

Not to disagree with Retro on which spokes are more prone to breaking, but there was an argument about that a while back that inspired me to make a thread. To my surprise, the responses showed more drive side spokes broken than NDS. (The poll allowed multiple selections)
https://www.bikeforums.net/showthread...ighlight=spoke
It does baffle me a bit, because I believe spokes are strong enough that excessive tension would make the rim fail long before the spoke could.

I changed my career path from mechanical engineering to music education, so I'll STFU and just read for a while.

Shimagnolo

A diploma from Purdue with a double major in engineering.
Are we done with the locker room comparisons now?

Retro Grouch 

Well, keep in mind that the frequent failures that I was speaking of happened around 10 years ago. I'm thinking manufacturers have responded by revising their methods since then.

Wheel failure modes seem to me to be changing. I'm seeing more rim failures and lots more hub failures than I used to in the mid 90's. I attribute them to the greater spoke tensions used today on even high spoke count wheels.

dahoyle

all that education, and not able to offer anything, I seriously doubt it.

If that is true, you should get your money back.

dahoyle

Please chime in any time. You are apparently one of the few here who actually can read and think for yourself.