Editing Crosshead (section)

==Overview==
On smaller engines, the [[connecting rod]] links the [[piston]] and the [[crankshaft]] directly, but this transmits sideways forces to the piston, since the [[crankpin]] (and thus the direction the force is applied) moves from side to side with the rotary motion of the crank. These transverse forces are tolerable in a relatively small engine. A larger engine's much greater forces would cause an intolerable degree of wear on the piston and [[cylinder (engine)|cylinder]], as well as increasing overall friction in the engine.

A [[piston rod]] is attached to the piston and links it to the crosshead, which is a large casting sliding in [[crosshead guide]]s (UK: ''slidebar''), allowing it only to move in the same direction as the piston travel. The crosshead also houses the [[gudgeon pin]] (US: ''wristpin'') on which the small end of the connecting rod pivots. In this way, the transverse forces are applied only to the crosshead and its bearings, not to the piston itself.