Cross-head

The crosshead is a sliding block between the piston rod and the connecting rod in a two-stroke crosshead engine, guided by vertical guide shoes that take the side thrust from the connecting-rod angle. This keeps the piston rod moving in a straight line and absorbs the transverse load that, in a trunk-piston engine, the piston skirt and liner would carry. The crosshead pin runs in a heavily loaded bearing fed by forced oil, often at higher pressure than the rest of the system because the oscillating pin never forms a full rotating film. The arrangement separates the combustion space from the crankcase, letting two-stroke engines burn high-sulfur residual fuel without contaminating the crankcase oil.