A crosshead (or crosshead bearing) is a bearing used in large reciprocating engines, whether internal combustion engines or steam engines. Usage On smaller engines the connecting rod links the piston and the crank directly, but this transmits transverse 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 smaller engine; a larger engine's much greater forces… (More on Crosshead)