Pullback motor

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A pullback motor (also pull back 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 (hence the name) winds up an internal spiral spring; a flat spiral rather than a helical coil spring. When released, the 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 use such a mechanism for their Stop'n'Go motor.[4] This is pre-wound, then releases automatically when shunted from behind. This allows relay races to be set up with multiple cars.

A few pullback motors are used in toys other than cars. The K'Nex construction toy has such a motor, as have some later Meccano sets.

The very simplest of these motors may use a stretched rubber band as a linear spring, rather than a coil spring. These are bulky and less powerful but require little manufacturing sophistication: coil springs, although apparently simple, demand a highly developed steel metallurgy. For this reason these toys are usually home- or crafts-made.

References[edit]

  1. ^ May, James (2009). Toy Stories. London: Conway. p. 175. ISBN 9781844861071.
  2. ^ US 2795294, "Keyless device for winding up clockwork mechanism", issued 11 June 1957 
  3. ^ a b c "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.