Appendix C
Engine and motor detail
The main diesel generator sets and propulsion motors of the similar WWII Fleet Submarine of the Gato, Balao and Tench classes.
1. General Motors V-16 type. There were two engine designs in this category, the 16-278A and 16-248. Each engine had two banks of 8 cylinders, each arranged in a V-design with 40 degrees between banks. Each engine was rated at 1600 BHP at 750 rpm. Both engines were equipped with mechanical or solid type injection and had a inflow valve and port system of scavenging. 2 cycle. Main Propulsion Dieselise, NAVPERS 16161
OR
2. Fairbanks-Morse opposed piston type, Model 38D 8 1/8. This model number included two engines, one a 10-cylinder and the other a 9-cylinder engine, 2 cycle.. Both engines were rated at 1600 bhp at 720 rpm. Main Propulsion Diesels, Navpers 16161
The rating of these engines was apparently modified to suit snorkelling. This reduced the surface rating from 5400 shp to 4610 shp. Alden reports 4610 shp for all snorkel submarines but only specifically says for the Loon SSG conversion, "Rated 4160 shp surfaced after installation of snorkel" - max surface speed 17/18 knots". See anecdote Appendix E.
The Main generators were rated at approximately 2650 amperes at 415 volts and 1100 kilowatts. Submarine Electrical Installations, Navpers 16162. That is a total of 10,600 amps at 415 volts.
Main motors used in a gear drive installation were classed as high-speed motors and each was rated for continuous duty at approximately 1370 hp, 415 volts, 2600 amperes, and 1300 rpm. On the latest classes of submarines main motors and reduction gears have been replaced by two 2700-hp double armature motors, directly connected to propeller shafts, one to the starboard and on to the port shaft. Submarine Electrical Installations, Navpers 16162
4 x 1100 kW = 4400 kW electrical output from generators to the motors - .5400 shp x 746 = 4028 kW motor output to shafts
Therefore efficiency of the motors is 4028/4400 = 91.6%. The efficiency would have dropped when the motors were overloaded as in GII.
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