A gear is a generic term for a contrivance whose function is to communicate motion from one machine or part to another. They were earlier referred to as a “toothed wheel”. Later the name changed to “gear wheels” and finally “gears”. It is among the oldest devices invented by man. In about 2600 BC, a chariot made by the Chinese was incorporated with a complex series of gears. Aristotle, in 400 BC, mentioned gears in his writing as a very common device. Later, in AD 1500, Leonardo da Vinci designed many instruments where different kinds of gears were used.
Although different kinds of mechanical power transmission devices (belt-pulley, chain drive, ...