132 ELECTRIC PROPULSION OF SHIPS. 



that the mechanical gear offers a better solution of the speed-reduction problem than the elec- 

 trical. It is far lighter, cheaper and more efficient. I note that a new vessel for the Ham- 

 burg-American Line (the Havelland) is being equipped with such an installation. It may be 

 pointed out, however, that there may be special reasons for making this selection. 



In connection with the use of high-speed Diesel engines, two of the oldest and most ex- 

 perienced builders of m.arine Diesel engines do not advocate this application, although they 

 build high-speed engines. 



Referring to page 118, we estimate that the fuel consumption of the Diesel electric will 

 be from 12 to 15 per cent more than the direct drive, and that the propulsive efficiencies will 

 be approximately equal. 



In the general summary, page 118, the author states that the Diesel electric weighs less 

 and costs less than any other type, which, as pointed out above, does not agree with our data. 



On page 119 the author states that geared turbines are better for destroyers and scouts 

 than electric drive. Since the former type of machine is superior for such vessels, it is not 

 clear to me why this superiority disappears when it comes to battleships and battle cruisers. 

 The following seems to be established: 



1. The electric-drive machinery weighs from 75 to 100 per cent more than the corre- 

 sponding geared turbines and costs about in the same proportion. 



2. The steam consumption of the electric drive is from 4 to 8 per cent more at full 

 speed, the boilers and auxiliaries being heavier to a slightly less extent. 



To offset these, the advantages claimed for the electric machinery do not seem to be 

 very substantial. The above are measurable and tangible advantages for the geared tur- 

 bine, which are opposed to a niunber of rather intangible ones for the electric drive, which 

 to me do not seem to be of equal importance. 



In this connection it is interesting to note that the British battle cruiser Hood is equipped 

 with geared turbines which develop 150,000 horse-power. The machinery of this vessel has 

 been a marked success. It would be of special interest to compare the machinery of this vessel 

 with the electrically driven machinery of our vessels. 



As noted in the beginning, the essence of this paper is electric drive. Electric-drive ma- 

 chinery is a splendid engineering achievement, and its mechanical operation is, without doubt, 

 superior to mechanical gearing. The absence of meshing teeth and the smooth, flexible oper- 

 ation appeal to the engineer. However, these features are not the chief ones in deciding the 

 type of transmission. The selection of the best type is largely a matter of economics. We 

 must be guided by comparative data and statistics as to first cost, weight, fuel consumption, 

 cost of operation, etc. These hard, cold facts will largely decide the best type. 



I have made a great many investigations and comparisons of these transmissions, and so 

 far the results have always shown the mechanical-gear machinery to be superior to the elec- 

 tric. In fact, the advantage has been foimd to be very large, so much so that the elimination 

 of electric transmission except in special cases is indicated. 



Personally, and as an engineer, I like the operation of electric transmission and will ad- 

 vocate its use whenever it is warranted. I am not opposed to electric drive, but I am opposed 

 to attributing to it advantages which it does not possess. 



In closing, I may say that American ships must have the most economic type of ma- 

 chinery so as to meet competition, and our purpose in the analysis and selection of machinery 

 should be the accomplishment of this end. 



