David Bean wrote:
>
> My '57 BMW motorcycle's gearbox uses a similar size shaft
> with woodruff key to drive the whole thing and that held up
> pretty well. That's somewhat more torque than a human can muster...
Are you sure? Jobst Brandt, who has designed automotive parts and knows how to run the numbers, says a man puts more strain on some drivetrain parts than a motorcycle. The BMW obviously generates more horsepower but at a rotational speed (rpm) very much higher. A human generates maximum torque at zero rpm.
There are other reasons too (besides magnitude of the torque) why a woodruff key might work better on a motorcycle gearbox than on a bicycle crank. I doubt any of us have the engineering ability to answer this question reliably, or are willing to put the work into doing so even if so equipped.
So I'm not saying you're wrong, only that it's not so obvious, and it's probably effectively unknowable. I will say this though - many of the old designs that fell by the wayside did so because they didn't hold up in actual use.
Mark Bulgier
Seattle WA USA