I worked in a nuclear power plant for a number of years, doing engineering surveillance testing of many different systems. One of my favorites was the EDG, emergency diesel generators. These were Fairbanks-Morse 10 cyl, 20 piston, vertically opposed two strokes. Bore about 18 inches, connecting rod about 4 feet long. Single centrally located crankshaft. My understanding that this engine, or similar, was common in marine propulsion applications.
It was designed and tested to go from zero to 3 megawatts in under 10 seconds. 900 rpm IRRC. Standing next to one when they lit it off was an experience. Even with hearing protection, the engine sound and rush of air into the "bunker" through the missile protected louvers was overwhelming.
The engines were always on a constantly heated lube oil recirc system. They were air started, with redundant air start banks, and each one (there were 4)had a standby luger diesel to run an air compressor to recharge the starting banks should the primary electric compressors fail. There was even a hand crank to start the luger should that engine's battery start fail.
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