The simplest examples of wind-up toys are ones that use turning handles. Clockwork toys work on a similar principle to that of a spring. A steel coil is wound up with a key and then released. A balance wheel is used to control the speed of release and ensure that the rate of relaxation is uniform. This results in a consistent release of energy. Cogwheels are used to convert the energy into movement.
From the late 17th century, French craftsmen made materials such as silver. In the 19th and early 20th century, there were expensive clockwork toys, such as walking dolls, but there were also mass produced tin toys.
Some wind up toys use friction to make them move. A central wheel (the friction wheel) is wound up by pushing the rear wheels of the toy backwards or forwards against a flat surface. When the toy is placed on the ground the friction wheel provides momentum to the other wheels to move the toy.