The segment gear, as the name indicates, is actually a gear wheel. This gear wheel is composed of a large number of pieces, which are small parts of a circle. Segment gear is attached to the arms or housings of the water wheel.

The segment gear has a piece for receiving or communicating the reciprocating motion from or to a cogwheel. This gear also consists of a sector of a circular gear or ring. There are cogs on the periphery.