I think you could probably weld an axle, hub, and cassette assembly right onto the input shaft of the machine and put your mountain bike right on there. The spinning blades of the shredder should provide enough inertia to act as a flywheel once you get the thing up to operating rpms. I think an electric motor, solar panel, and a bunch of car batteries would help too, or else you may have to feed it so slowly that it wouldn't be practical, depending on how strong or how patient you are.
