Darda model car powered by a pullback motor

A pullback motor (also ''pull back'' or ''pull-back'') is a simple

clockwork motor Clockwork refers to the inner workings of either mechanical devices called clocks and watches (where it is also called the movement) or other mechanisms that work similarly, using a series of gears driven by a spring or weight. A clockwork mec ...

used in

toy car A model car, or toy car, is a Physical model, miniature representation of an automobile. Other miniature motor vehicles, such as trucks, buses, or even ATVs, etc. are often included in this general category. Because many miniature vehicles were ...

s. A patent for them was granted to Bertrand 'Fred' Francis in 1952 as a keyless clockwork motor. Pulling the car ''backward'' (hence the name) winds up an internal spiral spring; a flat spiral rather than a

helical Helical may refer to: * Helix, the mathematical concept for the shape * Helical engine, a proposed spacecraft propulsion drive * Helical spring, a coilspring * Helical plc, a British property company, once a maker of steel bar stock * Helicoil A t ...

coil spring A selection of conical coil springs The most common type of spring is the coil spring, which is made out of a long piece of metal that is wound around itself. Coil springs were in use in Roman times, evidence of this can be found in bronze Fib ...

. 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 A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...

ratchet Ratchet may refer to: Devices * Ratchet (device), a mechanical device that allows movement in only one direction * Ratchet, metonomic name for a socket wrench incorporating a ratcheting device * Ratchet (instrument), a music instrument and a ...

and the car then rolls freely onward. Often the clutch mechanism is geared so that the pullback distance needed to wind the spring is less than the distance the spring is engaged propelling forward. Most of these cars are otherwise free-rolling. Winding them up requires them to be pushed downwards, engaging the clutch. As the motor is only engaged for winding while held down, the complete winding must be completed in one pass, unlike the

flywheel 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 rev ...

. Some motors have an internal

one-way clutch One-way or one way may refer to: * One-way traffic, a street either facilitating only one-way traffic, or designed to direct vehicles to move in one direction *One-way travel, a trip that does not return to its origin Music *One Way (American ba ...

that allows winding with a back-and-forth motion. 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. This is pre-wound, then releases automatically when shunted from behind. This allows

relay race A relay race is a racing competition where members of a team take turns completing parts of Race track, racecourse or performing a certain action. Relay races take the form of professional races and amateur games. Relay races are common in runni ...

s to be set up with multiple cars. A few pullback motors are used in toys other than cars. The

K'Nex K'Nex is a construction toy system founded by Joel Glickman. It was first introduced in America in 1992. K'Nex is designed and produced by K'Nex Industries Inc. of Hatfield, Pennsylvania. K'Nex was purchased by Florida-based company Basic Fun ...

construction toy has such a motor, as have some later

Meccano Meccano is a brand of scale model, model construction system created in 1898 by Frank Hornby in Liverpool, England. The system consists of reusable metal strips, plates, Structural steel#Common structural shapes, angle girders, wheels, axles and ...

sets. The very simplest of these motors may use a stretched

rubber band A rubber band (also known as an elastic band, gum band or lacky band) is a loop of rubber, usually ring or oval shaped, and commonly used to hold multiple objects together. The rubber band was patented in England on March 17, 1845 by Stephen P ...

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 Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys. Metallurgy encompasses both the sc ...

. For this reason, these toys are usually home- or crafts made.

References

Toy cars and trucks Mechanical toys {{toy-stub