The Portland - Engine Room

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Two identical engines drive the stern wheel on each side of the vessel. The port (left) engine is shown with the upper silver pipe delivering the steam to both ends of the cylinder. Valves at each end inject the steam so the piston is driven in both directions (double-acting). The pistons are 26 inches in diameter with a stroke of 108 inches. The two engines together produce 1800 horsepower. The energy from the piston is transmitted through the connecting rod out the back of the cylinder to the pitman arm that reaches through the aft bulkhead to the crank at the wheel. The long rods inboard of the pitman arm operate the valves at each end of the cylinder controlling the timing and direction of each stroke. On top of the joints in this system are small glass containers filled with oil. When the lever on their top is vertical they are opened and lubricate these joints by gravity and capillary action. The steam is used once and is exhausted into the big white colored pipe below the input. It then is taken back to a set of heat exchangers that use it to pre-heat the fresh water going into the boiler.

Inboard of the engines are two green water pumps that deliver the water to the boiler. This was originally river water but is now taken from two 10,000-gallon onboard tanks filled with city water to help keep the system clean. Forward of these pumps the round white unit is the old DC generator. This has been replaced by a diesel one and all the wiring has been replaced for AC current. Outboard of the DC generator on the port side is a small black pump used for potable water; on the starboard side is a red pump (not visible) that feeds the fire suppression system. All of these units are steam driven.