284 ELECTRIC PROPULSION OF MERCHANT SHIPS. 



space saved. The amount of room taken by the motor in the stern would be very close to 

 that saved in the engine-room; besides, there is no provision for ventilation of the motor 

 room. I have been informed by Mr. W. W. Smith, chief engineer of the Federal Ship- 

 building Company, that he had investigated the question of using the electric propulsion 

 for this class of ships, and it was found that this means of propulsion required more room 

 and was heavier than either the geared turbine or the reciprocating engine. The generator 

 being placed above the boilers, as shown, would be very impracticable for four reasons : — 

 First, the space above the boilers would be very cramped; second, the engine-room would 

 be considerably hotter; third, the auxiliaries would be on a different level from the oper- 

 ating platform, which is very undesirable. This has been experienced in many vessels 

 that have had such an arrangement. Fourth, the difficulty of providing proper foundations 

 for the turbine and gears. Very few engineers, if any, would care to go to sea in charge 

 of an electric propelled vessel without some means of commtmication between the motor 

 and the engine-room. Although a shaft tunnel is unnecessary, it would be necessary, or 

 at least most desirable, tO' have an alley-way for carrying the electric cables, as these must 

 be protected from damage by freight or water that may get into the cargo space. Further- 

 more, this alley-way should be large enough for a man to pass through and be able to re- 

 pair the cables while the vessel is at sea, or partly loaded, without shifting the cargo. 



On page 278, third paragraph, it is stated that the motor would be self-lubricating and 

 only occasional inspection would be necessary. This might be the case, but I would consider 

 it very risky to leave this compartment with only occasional inspection, for if any trouble 

 occurred, it would very likely be between inspections and might result in a general disability 

 before it is discovered. It is true that auxiliary machinery, such as the steering engine, is 

 placed at the stern, and only occasional inspection is given; however, the difference in 

 importance between a part of the main propelling machinery and the steering engine is 

 considerable. 



I do not believe that any greater economy can be obtained with the electric propulsion 

 than with the geared turbine. If it is advisable to use electric-driven auxiliaries, which I 

 doubt very much, there is no reason why this type should not be used with the geared- 

 turbine outfit and the same economy be obtained. 



Regarding the reliability, I can, see no advantage in the arrangement suggested in this 

 paper for' operating vessels with the main generating unit out of service. Having a motor 

 generator set or rotary converter arranged so that the power of the auxiliary generators 

 could be delivered to the main, motor would be quite expensive, especially for a piece of 

 machinery that would be lying idle most of the time. Besides, the auxiliary generators 

 would have to be considerably larger than would be necessary for the operation of the aux- 

 iliaries. Trouble at sea with reciprocating engines and their remedies are too well known 

 to be dealt with in this paper. We know that, as far as reliability is concerned, this engine 

 is as good as any. With the geared turbine of the cross-compound type, reliability is as- 

 sured without carrying any spare machinery. There are cases on record where one of the 

 turbines or its pinion has given trouble and was disconnected. While steaming with on,6 

 turbine a speed of 9 knots was obtained, while the speed obtained with both turbines in 

 operation was about 11)4 knots. 



If any water should get into the engine-room and on the electric machinery, the chances 

 of trouble are considerable. Although this has been denied on several occasions by advo- 



