Originally Posted by
smashndash
I have not read the book. Only seen some snippets/debates online.
Don’t mean to turn this into a debate but:
“Other than its tension the bicycle wheel is the same as any other wheel such as a wooden wagon wheel. The spoke under the hub is shortened in compression by a load on the axle, while the upper spokes remain unaffected by the load.”
Maybe I’m just dumb but I don’t see a lack of tension as the same thing as compression. We don’t have to discuss this any further, but I think this could be fairly easily resolved if someone heavily loaded a wheel and then cut the spoke at the bottom, and nothing happened. If that spoke were truly a load bearing structure, then something would happen. Regardless, you’re right that this has been debated endlessly and there’s no resolving it.
There's a world of difference between a bicycle spoke which acts pretty much only in tension (there's even FiberFix Kevlar fiber replacement spokes and Spinergy makes spokes out of PBO fiber), and a wagon spoke which is a stiff structural member that can act in compression. Also, a big difference in the joint that the wagon wheel spoke was fastened to the rim with (good for compression, not so much tension). Bicycle spokes act in tension, and unless the are always under a bit of tension, they fail quickly. Wagon wheels had steel tires that were heated, put over the wooden rim, and then quenched. As they shrunk, they put all the wagon spokes in compression. So, that's the first thing: wagon wheels are a completely inapt comparison.
Lack of tension is not compression. If an unloaded wheel spoke has 100 kgf tension, it may be that the bottom three spokes on the wheel are loaded at, say 80-90kgf when under load. This just means that (for both wheels) 60-120kg of downward force, from the bottom spokes pulling down, is removed from the hub. The upward force of the remaining spokes is what supports you. One quibble I have with how Jobst explained it was that he said words to the effect that the top spokes don't increase their tension to support you. I would have said something like "There's a force balance on the unbalanced wheel where all the spokes pull evenly and the up and down forces even out. When the wheel is loaded, the spokes near where the wheel touches the ground are unloaded a bit. This means that some spokes aren't pulling down as much as in the unloaded wheel. The difference in force is what supports you. Note that it IS the force of the top spokes from which the hub (and bike) are suspended that is supporting your weight."
I agree with the poster above: Hambini is a technically smart guy that doesn't give enough of a ***k to explain things to others who differ even slightly, and he kind of takes the same approach as some politicians today to anyone who questions his infallibility. He expects his words to be taking without question. Undercuts his message, some of which is useful. If I had the exact problem that one of his videos addressed, I'd watch it. Otherwise, very tiring. Better things to do.