Pullback motor

A patent for them was granted to Bertrand 'Fred' Francis in 1952 as a keyless clockwork 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.

The K'Nex construction toy has such a motor, as have some later Meccano sets.

These are bulky and less powerful but require little manufacturing sophistication: coil springs, although apparently simple, demand a highly developed steel metallurgy.