in China, and they were widespread by the medieval period.

Camshafts were first described by Ismail al-Jazari in 1206. Once the rotative version of the steam engine was developed in the late 18th century, the operation of the valve gear was usually by an eccentric, which turned the rotation of the crankshaft into reciprocating motion of the valve gear, normally a slide valve. Camshafts more like those seen