Pullback motor

A Darda model car powered by a pullback motor

A pullback motor (also pull back, pull back and go or pull-back) is a simple clockwork motor used in toy cars. A patent for them was granted to Bertrand 'Fred' Francis in 1952 as a keyless clockwork motor.^[1][2]

Pulling the car backward winds up an internal spiral spring; a flat spiral rather than a helical coil spring. When released, the toy car is propelled forward by the spring. When the spring has unwound and the car is moving, the motor is disengaged by a clutch or ratchet and the car then rolls freely onward.^[3] Most of these cars are otherwise free-rolling. Winding them up requires them to be pushed downwards, engaging the clutch.^[3] As the motor is only engaged for winding while held down, the complete winding must be completed in one pass, unlike the flywheel motor. Some motors have an internal one-way clutch that allows winding with a back-and-forth motion.^[3]

Some pullback motors, usually intended for racing in pairs, have used a catch and release mechanism to retain their springs. These may be wound separately, then launched together by releasing their spring triggers. Darda toys use such a mechanism for their Stop'n'Go motor.^[4]

References

1. May, James (2009). Toy Stories. London: Conway. p. 175. ISBN 9781844861071.
2. US 2795294, Francis, Bertram F., "Keyless device for winding up clockwork mechanism", published 1957-06-11 
3. "Darda standard Mega-motor". onlytoys.com. Archived from the original on 2003-04-23.
4. "Darda Stop'n'Go replacement motor". onlytoys.com. Archived from the original on 2010-08-29.