Camshaft

A camshaft is a rotating shaft fitted with a row of shaped lobes, called cams, that convert the shaft's continuous rotary motion into the back-and-forth reciprocating motion of a follower riding against each cam, a conversion used today to open and close the intake and exhaust valves of a piston engine in precise timing with the engine's rotation. The earliest known mechanisms using a cam in this way are trip hammers driven by a rotating shaft with lobes that lift and release a hammer, evidence for which survives in China from the Han dynasty and which had become widespread there by the medieval period. The camshaft as a distinct mechanical component was formally described far later by the Artuqid engineer Ismail al-Jazari in 1206, and it entered automobile engines in the early twentieth century, with the 1902 Maudslay and 1903 Marr Auto Car among the first cars to use an overhead camshaft design.