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 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 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 originally a ...

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

coil spring A tension coil spring A coil spring is a mechanical device that typically is used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces. It is made of an elastic material formed into the ...

. 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 allows an output shaft to be disconnected from a rotating input shaft. The clutch's input shaft is typically attached to a motor, while the clutch's output shaft is connected to the mechanism that does th ...

ratchet Ratchet may refer to: Devices * Ratchet (device), a mechanical device that allows movement in only one direction * Ratchet effect in sociology and economics * Ratchet, metonymic name for a socket wrench incorporating a ratcheting device * Ratc ...

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. Some motors have an internal one-way clutch 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 racecourse or performing a certain action. Relay races take the form of professional races and amateur games. Relay races are common in running, oriente ...

s 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 Meccano is a brand of construction set created in 1898 by Frank Hornby in Liverpool, England. The system consists of reusable metal strips, plates, angle girders, wheels, axles and gears, and plastic parts that are connected using nuts and ...

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

rubber band A rubber band (also known as an elastic, 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 Perry ...

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 ...

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

References

Toy cars and trucks Mechanical toys {{toy-stub