This elastic band powered model is entirely freelance. It started as a basic trapezium shaped frame with which to test the mechanics. Having found a design that works a seat, engine casing and (dummy) steering wheel were added.
The rear axle has a ratchet fixed to it. A 57-tooth gear wheel is loose on the axle and this is meshed with a 19-tooth pinion which is journalled in a short coupling on the axle. An angle bracket, loosely bolted to the gear wheel, engages with the ratchet, there being not enough ground clearance for a pawl. This provides the model with a freewheel (as on a bicycle).
The elastic band used is one of the large red ones discarded by the postman. Winding the wheels back winds up the elastic band, which is stretched between a small fork piece on the same shaft as the pinion and a pin at the front of the chassis.