204 THE APPLICABILITY OF ELECTRICAL PROPULSION TO 



Mr. Ernest H. B. Anderson, Member: — I have read this paper with a great deal of 

 interest, and while the author puts forward a good case for the electric drive, yet it does not 

 seem to me that any great naval power can properly make an experiment using the electric 

 drive for the propelling machinery installation of a modern battleship, taking into consider- 

 ation the fact that only one of these electrical installations has yet been tried, and that on a 

 smaller vessel and with a very much simpler layout. 



As the author points out, there are many methods of ship propulsion, but for the larger 

 size of battleships and battleship cruisers, there are only two methods which are being seri- 

 ously considered : first, turbine machinery of the direct drive ; and second, high-speed tur- 

 bines and mechanical reduction gears. 



The former needs no comment, as it is general knowledge that there are turbine ma- 

 chinery installations of the direct-drive type now at sea which develop about 100,000 shaft 

 horse-power and drive large vessels at speeds in excess of 30 knots. 



The latter system is making equally as rapid progress as the direct-turbine drive in prac- 

 tically all classes of vessels, and there is now under construction geared turbine machinery of 

 which the horse-power to be transmitted through one line of shafting is equally as great as 

 that per shaft of the largest direct-drive turbine installations. 



Referring to the author's paper, I do not like the idea of using one generator in a bat- 

 tleship to supply current to four motors driving separate shafts for speeds up to 19 knots, 

 and I feel certain that, under regular battleship steaming conditions with the other vessels 

 of the fleet, such a scheme will be found impracticable. 



Independent control over each shaft is preferable, and this is obtained with an installa- 

 tion of high-speed turbines and gearing. 



Nothing is stated regarding the type of drive for the auxiliary machinery units used in 

 conjunction with the generating set, but it is presumed that those directly operated with the 

 main engines will be motor driven. 



I understand this type has not proven entirely satisfactory in power stations, unless 

 steam-driven sets are also installed for stand-by purposes, and on board ship the latest battle- 

 ships are now using steam turbines to drive the boiler-room blowers for the forced draft 

 system. 



As regards reliability, nothing but years of extended service will prove this, but it is 

 worthy of notice that the Jupiter has not been free from the somewhat regular accidents 

 common to every type of marine engine. 



Backing or astern turbines are not giving any trouble due to blade strips, and I have 

 not seen a case of a blade strip in any one of the four United States battleships which have 

 reaction turbines. 



As regards economy, the trial data of the Jupiter do not appear to show any special 

 gain either in the water measurements or in the coal consumption records. 



Dealing with the questions of space and weight, it is somewhat difficult to say any- 

 thing definite on these points until one has a case to consider, but I believe the new design 

 of motor proposed for a battleship will weigh considerably more than the type of motor in 

 the Jupiter. I believe any advantage in weight would be largely in favor of the all-gear tur- 

 bine drive. 



For a battleship of 33,000 shaft horse-power and 21 knots, the weight of the turbine 

 only for a four-shaft direct drive varies from 550 to 600 tons, and for a four-shaft all-gear 

 installation from 320 to 350 tons. 



