Steam Engine Crosshead

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The main bearing of a steam engine is designed to handle sideways forces from the connecting rod without transferring this load onto the piston or piston rod seals. This mechanism plays a crucial role in eliminating sideways pressure on the piston, allowing the connecting rod to move freely outside the cylinder. In long reciprocating engines and compressors, it prevents the piston from coming into contact with the cylinder walls due to its small bore-to-stroke ratio. If the piston was directly attached to the connecting rod like on trunk engines, the engine would stall due to the connecting rod hitting the cylinder walls. Consequently, the crosshead's longitudinal dimension must be precisely matched to the stroke of the engine to ensure smooth operation.