SOME COMPARISONS RELATING TO ELECTRIC PROPULSION OF A 



BATTLESHIP. 



By W. L. R. Emmet, Esq., Member of Council. 



[Read at the twenty-third general meeting of the Society of Naval Architects and Marine Engineers, held in 



New York, November 18 and 19, 1915.] 



The Navy Department of the United States has awarded to the General Elec- 

 tric Company of Schenectady, N. Y., a contract for electric propelling machinery 

 for the new battleship California, which is being built at the New York Navy Yard. 

 This ship is of the largest and most powerful class which has been adopted by the 

 United States. Her displacement is 32,000 tons and her maximum speed is to be 

 about 22 knots, requiring about 37,000 shaft horse-power. The contract with the 

 General Electric Company covers two turbine-driven generating units, four propel- 

 ling motors (one for each shaft), switching apparatus, cables, instruments, etc., 

 two turbine-driven exciting units, and a complete equipment of condensing auxil- 

 iaries and ventilating blowers, all driven by motors from the exciting units. In 

 fact it covers practically the entire engine-room equipment except the main con- 

 densers. 



Each of the auxiliary units is of 300 kilowatts capacity with a 240-volt di- 

 rect-current generator geared to a high-speed, non-condensing turbine. These 

 turbines will exhaust into the heaters, into the main turbines, or both. 



The motors which drive the auxiliaries will be designed for a considerable 

 range of speed variation so that the auxiliaries will be adaptable to economical 

 conditions at different speeds of the ship. 



The award of this contract was the result of a very long campaign of education 

 which has been conducted by the writer in which the equipment of the collier Jupi- 

 ter has been an incident. The writer has from the first maintained that the proper 

 field for electric propulsion was in ships of high power and in ships where economy 

 at widely varying speeds was important. 



The Jupiter has now been in commission for two years and has proved an un- 

 qualified success. The steam consumption of the main drive with igo pounds pres- 

 sure, dry steam, and 28.5 inches vacuum is 11 pounds per horse-power hour deliv- 

 ered to the propeller shafts, which is at least 30 per cent better than is done by re- 

 ciprocating engines in ships of the class. There is also evidence of further saving 

 in the Jupiter, incident to the fact that her large low-speed propellers are turned 

 with a perfectly uniform angular motion and with entire freedom from racing, 

 conditions heretofore unknown with such propellers. 



