How to make apparent wind work for you?

How does a wind up car work in a diagram if possible for school we need to make a car and my and my friend want to do a wind up car so does anyone know how to make one?

• Answer:

  Wind up cars work a lot like a wind up clock except with far fewer gears. The spring spins an axle with a large gear on it. That gear drives a much smaller one on another axle that's attached to the wheels. A fancy wind-up will have a speed regulator of some sort (often nothing more than a couple of paddles driven by an intermediary gear. I'd recommend you drop by a local department store and buy a wind up car then take it apart. You'd learn (or be able to figure out) how to prevent the spring from unwinding when you don't want it to (some kind of pawl against the gear teeth). You'd also learn that you better have the car aimed properly before you take off because stopping that spring powered motor isn't going to be easy (maybe not even possible) once you unleash it. Cheers