Thanks for the animation. And by moving the front pulley up and down, one changes the gearing.

A lot of the drive could be done with a typical offset crankshaft, but this funky drive system probably gives it more or less constant linear drive motion, as well as producing power through a full half stroke (which is then picked up by the opposite side).

There will be some parasitic loss with all the bearings, as well as the ratcheting mechanism on the rear spools.