How does a pull-back car work? Illustrated teardown

Pull-back toy cars use a cleverly engineered system of gears and a spiral spring to store and release energy. When a child pulls the car backward, gears with different sizes work together to wind up the internal spiral spring, with smaller gears providing mechanical advantage to make winding easier. Upon release, the wound spring converts its stored energy into rotational movement that propels the car forward at high speed—a mechanism invented by Darda in 1970 that replaced earlier toys requiring manual key winding.