The power is usually transmitted by a roller chain, also known as a drive
chain or transmission chain, which passes over a sprocket gear, with the teeth of the gear meshing with the holes in the chain links. When the gear is rotated, the chain is tugged, giving the system mechanical force. The
Morse chain, invented by the Morse Chain Company of Ithaca, New York, is another form of the drive chain. This has
teeth that are reversed.
The Polybolos, described by the Greek engineer Philon of Byzantium, has the earliest known application of a chain drive.
Two flat-linked chains are attached to a hollow shaft, which would roll back and forth until the magazine was empty, automatically firing the machine's arrows.
The Greek layout marks the start of the history of the chain drive because 'no earlier example of such a recorder is known, and none as the complex is known until the 16th century,' despite the fact that the chains 'did not transmit power from shaft to shaft, and thus they were not in the direct line of ancestry of the
chain-drive proper.'
It was here that the flat-link chain, which is frequently credited to Leonardo da Vinci, first appeared.' Su Song
(1020-1101 AD), a medieval Chinese polymath mathematician and astronomer, depicted the first continuous and endless chain drive in his written horological treatise, which he used to operate the armillary sphere of his astronomical clock tower, which is the first astronomical clock, and also the clock jack figures, which mechanically pound gongs and drums to display the time of day.
The chain drive transformed rotational motion to recliner motion and was powered by
Su's water clock tank with waterwheel, both of which served as a huge gear.
