Connecting rod

The connecting rod links the piston, or in a crosshead engine the crosshead, to the crankshaft crankpin, converting reciprocating motion into rotation. The small end carries the gudgeon pin or crosshead pin; the big end is split and bolted around the crankpin journal bearing. Forged alloy steel is standard. The rod transmits gas and inertia loads in tension and compression and houses a drilled oil passage feeding the small-end bush and, in many designs, the piston cooling oil. Big-end bolt elongation is set by hydraulic tensioning to a controlled value, since bolt failure releases the rod through the crankcase.