http://www.fixedgeargallery.com/2005...eBikeCo-op.htm

pedaling forward, R freewheel engages. pedaling backward or resisting, the L freewheel engages (reverstically), effectively being fixed.

i don't think it would be possible to have two different gear ratios. both are going around and around all the time at the same rate--b/c they're connected at the cranks--but they're each trying to turn the wheel a different amount each time.

nope.