I know I'm missing something, but after participating in this thread:
http://www.bikeforums.net/showthread.php?t=487629
I was left with the impression that the problem with shaft drives is that they lose efficiency by having to transfer energy at right angles at each end of the shaft. (Simply put.)
The advantages seem to have mostly to do with ease of maintenance, coping with difficult environmental/weather conditions, reduced failure rate, easier to deal with on commuting bikes, etc. Possibly also less vibration and a quieter bike.
Yet, the consensus seems to be that there just can't be any shaft drive that will approach the same efficiency as a chain or belt drive for bicycle drive-trains, due to the 'angle' problem.
Yesterday while channel surfing I came across an old western, a crowd scene at a rail yard. Something about it caught my eye, but I wasn't sure what.
I realized what it was this morning. To wit:
Train Wheels Rigged
Looking at this animation, why not a transmission in which the front wheel shown here is the crankarm-wheel and the back wheel is flywheel (or whatever the correct term is) driving an IGH?
Is there something inherently even less efficient about this motion, or something about it that makes it unsuitable for a two-wheeled vehicle?
I know it's probably a silly question, but I'd like to know why.