Steam Engine: Pistons & Rods

The engine is directly coupled to the propeller by the crankshaft. As a three-cylinder, triple-expansion, double-acting steam engine, double-acting means that steam pushes the piston both down and up. Therefore, every motion produces a force on the crankshaft and thus the propeller.

This is done by using piston rods that push connecting rods. The large-diameter piston rods are attached to the pistons above. As the pistons are driven up and down by expanding steam, the piston rods push the connecting rods that turn the crankshaft which rotates the propeller to drive the ship forward.