124 ELECTRIC PROPULSION OF SHIPS. 



do not think there is much to wear out in an electrical ship, so far as the electrical apparatus 

 is concerned. You might have to replace a bearing occasionally, but normally, electrical ap- 

 paratus of that type is virtually everlasting. In other forms of drive it is not always so. 



Another matter that I would take excepti on to, or at least state a little differently, is the 

 matter of the efficiency of the synchronous motor, as compared with the induction motor. We 

 have applied synchronous motors to several ships and what Mr. Thau says is in a way justi- 

 fied, because if you waste enough power on excitation, you may equalize the differences 

 which exist between the efficiency of the two systems, but my idea of the electrical drive is a 

 little different from anything that has ever been actually produced, because I would like to 

 see the ship equipped with sufficient means for making electricity for auxiliary purposes, and 

 if all the auxiliary operations in a ship were done electrically, and your electric power is 

 made efficiently, the excitation would be secured at a very low cost. 



If power is obtained of proper efficiency for excitation in connection with other auxili- 

 ary purposes, in the case of the synchronous motor it will be something like 3 per cent better 

 than the induction motor, and the apparatus will be materially lighter. 



Another point is that the synchronous motor apparatus has an air gap on the order of 

 three or four times as much as that which is practicable with the induction motor. 



Furthermore, the synchronous motor can be made with removable poles, so, without dis- 

 turbing the position of the machinery itself, you can take off a pole, get at the windings of 

 the stator, and replace the windings without removing or lifting anything, and such operations 

 are very simple and easy. The synchronous motor is of rather simpler mechanism than the 

 induction motor, because there are simple solenoids for field windings, the movable parts ; in 

 other words, there is a more easily repaired structure. 



As to some of the remarks about the Diesel electric, I do not pretend to know much 

 about Diesel engines or the possibilities of electric drive with them, but I am very much inter- 

 ested, or should be, being an electric man. I would like to push the Diesel electric along if 

 it is a good thing, and for the sake of bringing out discussion I want to state that certain 

 people, who are well informed in the Diesel engine business, have given me the impression 

 that the records to date indicate that the slow-speed Diesel engines were rather more prac- 

 ticable than the high speed. I do not see any very inherent reason why the high-speed Diesel 

 engine might not be made good, but combustion takes time and it may be that there is some- 

 thing in this point. 



I do not think I could quite agree there with Mr. Thau's statement that the alternating 

 current Diesel electric drive is out of it. I would not go so far as to say that, although I 

 might possibly agree with him if I really gave more thought to the thing, and had his reasons. 



One other thing which has not been mentioned in this paper is the advantage afforded 

 by interchange ability in electrical ship installations. On board the Maryland, the other day, 

 we ran at 19 knots with one generator, a 21 -knot ship; we ran 17 knots with only one gen- 

 erator and two motors. I say two motors — I mean two propellers trailing. I think this is very 

 valuable. In a passenger ship with two turbines designed to run 22 knots, you could run at 

 18 knots with one generator. That is very desirable in many merchant ships — to be able to 

 run economically at lower speed. 



Another matter which Mr. Thau has not mentioned is the advantage afforded in war- 

 ships of the change of ratio in the electrical motors. That is done in existing warships. I have 

 heard statements to the effect that the Teimessee gained nothing through that change of 

 poles. I do not understand the cause for that. The question was raised on board the Mary- 



