trail wrote:
Benv wrote:
ST: "But does it shift and does it work under load?"
Well they showed how it can shift, and is seems plausible.
Plausible != good. Demonstrating it under no load at maybe 30 rpm doesn't convince me it's a good idea that would work at 1500W and 120 rpm.
Don't get me wrong, the shifting mechanism is ingenious, but horrendously complicated and at high risk of spectacular failure.
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And I understand the concern about torque/force getting concentrated on just 1-2 rollers vs the load-spreading of a chain. But I don't understand the notion in this thread that it's like this really confounding problem to material science and mechanical engineering. Humans aren't *that* strong, even with the leverage of a crank arm/pinion. And steel is really, really strong.
A back of the envelope calculation of the force an average rider standing on the cranks would put through a single deep groove ball bearing gives a number well in excess of the C0 (static load rating) of the size of bearings they're using. That's for bearings that have had decades of material science and manufacturing technology development. Steel is strong, sure, but the point loads will kill it. Humans don't output lots of power, but due to the low speeds we can output extremely high torque. A big chunk of steel would do it (as has been proven with bevel gear shaft drive bikes), but not a ball bearing system.
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It's plausibly efficient. And I really like that it can be protected and kept clean, vs. chains which are always in the process of getting dirty when ridden.
I disagree with the efficiency claims, there are still sliding faces in contact. And it would be just as feasible (and race-illegal) to put a cover over a derailleur chain system to protect it.