Engine Room Telegraph
The B-2 or aft engine room contains a back-up duplicate of all critical machinery (generator, air compressor, fire pump, switchboard) plus the main propulsion engine. You can count the eight cylinders of the 550 horsepower supercharged Atlas Imperial diesel engine. It is a direct reversible engine; meaning there is no clutch or reverse gear. To reverse, the engine must be stopped, the cam reversed, and the engine restarted, sending the crankshaft in the opposite direction. Compressed air starts and reverses the engine. Ships cruising speed was 10 knots. A reduction gear under the step-up spins the propeller shaft at about one third the speed of the engine. Note the brass disc with the pointer behind the ladder that is the engineer’s end of the engine room telegraph you saw in the wheelhouse.