Previously hidden from view because it had been glued face-down on another page, the drawing clearly shows a bicycle, complete with pedals, a chain-drive and sprocket wheels.
This was changed to drive by friction pulleys with the sprocket wheels maintaining the synchrony when it was found that this caused less damage to the tapes.
No sprocket wheel is employed; in stead, the film is pulled by, and wound onto the drum that always rotates the same angular amount for next picture frame.