AnkleWork

He said that in a conventional tensioned spoke bicycle wheel the hub stands on the lower spokes. Then he shucked and jived claiming that reduced tension is compression which absurdly defies structural engineering. He never came off the "hub stands on the lower spokes" error or any of his other mistakes. His propensity to turn small mis-statements into enduring large errors out-lived him.

Ghrumpy

I know what he said, I have the book sitting right next to me. And I agree that he could hardly admit to be wrong. That's indeed the unfortunate part of his legacy. We're not bound by that though.

I'm not defending the "standing on its spokes" claim. It didn't sit right with me when I first read it 25 years ago, and it still doesn't. I am trying to contextualize it as first as a too-single-minded attempt to refute the "hanging" theory, and second, as a functional metaphor in what is basically a non-engineering text. Metaphors are inherently inaccurate, so is a bad one an "error," or just a bad metaphor?

In case you're wondering why I would bother to try to contextualize it, it's because continuing to bust Jobst's chops for getting something "wrong" is just playing the same game he did and trying to beat him at it. Not really a fair fight at this point, since he's no longer around to answer for himself. I not interested in that game. I'm interested in the wheel. I'd be very interested in your explanation of what's happening in the wheel, if you'd care to give one. Doesn't have to be yours originally.

Kontact

I agree with your take on this. My reaction after reading that section was similar - Brandt was making a point by illustrating how even the reductio ad absurdum could be shown to be true. But very few people understand the point he was making about how the hub was no more hanging as it was standing on the spokes. Sometimes the things he wrote were for people who's minds were working at a similar level, and not as an intro to physics for those who are looking to be spoon fed the literal truth.

AnkleWork

Jobst reincarnated continuing the shuck and jive? His explicit errors endure.

ThermionicScott 

Are you "jim beam" reincarnated? All name-calling, no superior explanations.

AnkleWork

And the spin continues. A simple free body diagram of the hub reveals everything -- that the hub hangs from the upper spokes. That's why joBSt never produced one.

AnkleWork

You don't accept the superior explanations which have been presented repeatedly. Where's the name calling? Please quote (your post excluded).

ThermionicScott 

Is that first sentence supposed to be a question? If you can get over being triggered by Jobst's use of language, spoke tension measurements of loaded wheels generally back up his explanation. A model is only good to the extent that it accurately reflects reality...

Ghrumpy

What is this, the "Argument Clinic"? It's funny when Monty Python does it, but that's because it's SATIRE.

I said the hub neither hangs from nor stands on its spokes. If you can't bother to actually read or respond to what I've written, I'm not going to waste my time. So with all due respect, I'm done with you on this topic unless you provide a "superior explanation." That doesn't mean simply asserting an opposite view. That is not providing anything but your belief. Explain it. Then we can talk.

Kontact

Like this one? Why aren't the highest tensions on the top spokes?




It isn't "spin". Brandt was making a point about how a pre-tensioned structure, like a wheel or pre-stressed concrete bridge, actually works. He does not say "the hub stands on its spokes", he said "the wheel stands on its spokes." And maybe that's why people get so confused about the point he is making about how the change in tension from weight never makes the hub dangle because all the spokes maintain positive tension, which means hub never has the opportunity to hang from anything. When the wheel is weighted, the structure acts identically to a solid wheel - it compresses on the bottom. And that has practical considerations when it comes to wheel design that the "hangin' from the spokes" perspective does not.

If you want to read the actual text, go to page 47:
https://caravan.hobby.ru/materiel/Bic...bst_Brandt.pdf

AnkleWork

Because it is a tension stayed structure. The tension in the red spokes net-out. The load on the hub is transmitted to the rim via the top spokes. There's a good reason you don't want to see a FBD of the hub.

Also, there must be a reason you use the extreme case of a wheel with four completely slack spokes rather than a proper wheel.

noglider 

Jeez, man, give it a rest. You don't like the terms he used, but I think he knew where the forces were.

AnkleWork

If you would study engineering a little, you would find that distorting the correct language destroys meaning. Try designing reinforced concrete structures without a firm grasp of the concepts of tension and compression. Also, there's little room for arrogance in engineering. Maybe that's why Jobst was relegated to over-analyzing what most of the industry considers a child's toy.

Kontact

That particular diagram (which I did not create) shows a load that is crushing the wheel. The interesting thing is how the highest spoke loads aren't directly above the hub.

I think you're getting too wound up in the semantics to appreciate the fact that the change in load on a bicycle wheel is, in fact, seen as compression on the bottom of the structure, rather than an increase in top spoke tension.

noglider 

The man is dead, and he's still making you angry? Hey, you got your revenge. What more do you want?

noglider 

And you don't know what I've studied, do you?

AnkleWork

Is it "semantics" to misrepresent simple truths? The compression is only in the rim. The values listed in your diagram all show tension in the spokes.

AnkleWork

Haw! At least I know what you have not studied.


That's your filter, so you should own it rather than projecting it onto others. Funny how direct factual statements are frequently perceived as anger. And, what revenge, exactly? (Not a rhetorical question.)

Jobst's public errors live on and on as long as people repeat them. Truth always has to be rediscovered and reborn (and argued against).

Kontact

And? The compression in the rims causes the spoke tension to change. Tire pressure causes the spoke tension to change.

Are you under the impression that spoke tensions remain static as the wheel rolls?

AnkleWork

Your attempted explanations don't address Jobst's falsehoods and I'm not inclined to school you. There are specific rebuttals to Jobst, as well as generalized analyses for tension stayed structures, both based on correct engineering principles available online and elsewhere if you care to look at them.

Kontact

Allow me to provide a response just as illuminating as yours:

You're wrong.


Why post on a discussion forum if you aren't capable of politely discussing something?

AnkleWork

I have consistently rebutted Jobst's claims (often repeated by others) that the hub of a conventional bicycle wheel "stands on the spokes", and that reduced tension in the spokes is "compression." Not sure why you continue to introduce other, irrelevant claims (e.g. that spoke tension does not change as the wheel rolls) as they do not support your argument, but hey, it's your time and effort.

AnkleWork

(Shhh. I can hear your feet stomping.)
Care to point out my impoliteness? It's just your filter. But I do apologize to all the true believers here for impugning your belief system.

Kontact

I suppose I could, but I'm not inclined to school you.

Kontact

I have no idea what arguments you've made elsewhere. Should I?

I'm not making any claims as much as trying to decode your abstruse "explanations". Between the responses on this thread on PMs I've received, I don't think anyone has found your arguments reasonable.


I would suggest that if you actually want to promulgate your point of view, you're going to need to actually offer cogent, specific explanations and rebuttals without reference to unseen prior threads and without the vague put downs. All of that stuff just makes it sound like you are BSing rather than speaking from any sort of expertise or logic.