Theoretical question about double drivetrain (both-sides drive) If one were to take a single-speed flip-flop hub, and fit two identical freewheels, and couple them to two identical chainrings (i.e. two drive-side cranks, one on each side of the bike), you would have the world's heaviest and least efficient fixed-gear drivetrain. One freewheel coasts while the other drives. (The left-hand pedal would have to be fitted with a right-handed axle, and thread-lock used to prevent it unscrewing due to precession.)

Why anybody would want to do it is beyond me, but I am certain that this would work.

Now, bear with me here...

What if one were to do the same thing, but with a slightly larger chainring on the drive side, and a slightly larger freewheel on the non-drive side? (Obviously magic ratios would have to be selected for identical chain lengths.)

Would this provide a long gear for high top speed, yet provide a shorter gear for less strenuous leg-braking? Or would the freewheels somehow skip and bind?
After thinking about this for awhile, I think this would work, albeit somewhat clumsily. It would operate similar to a retro-direct, except with no reversing for the second freewheel. You would have to use good quality freewheels to avoid having both of them engaging together and binding.

To answer a commenter Blam:


  Just how would you expect it to magically shift grears? The are both attached to the same axle. 


The two freewheels being engaged in opposite directions would result in only a single freewheel being engaged at a time. He wouldn't be able to 'change' gears, going forward, but would see a different torque profile when slowing down compared to when going forward.