Friction motor

A friction motor is a simple mechanism to propel toy cars, trucks, trains, action figures and similar toys. The motor consists of a large flywheel which is connected to the drive wheels of the toy via a very low gear ratio, so that the flywheel revolves faster. The flywheel's axis is perpendicular to the direction in which the toy faces and moves. When the toy is pushed forward, the drive wheels engage the flywheel. Pushing the vehicle forward repeatedly spins this flywheel up to speed. When let go, the flywheel drives the vehicle forward. The flywheel stores the kinetic energy of the initial acceleration and propels the toy after it is released.