86 SOME COMPARISONS RELATING TO 



ship with Parsons Drive, Taken from Sir Charles Parsons' Paper of March 13, 1913." That 

 is all I can do. The fact that the battleship is large is no reason why it should be more desir- 

 able to make it suitable for good economy at cruising speed than if it were smaller. We 

 might assume that it was also desirable tO' put these various arrangements in the California 

 in order to give her economy at the cruising speed. I used that simply as an illustration. I 

 think the comparison as to the details of the number of parts is amply justified. 



Another speaker has mentioned the question of the percentage of loss in electrical appa- 

 ratus. He makes it sum up to 14 per cent, but in point of fact the actual electrical losses 

 by test of the apparatus on the Jupiter are only 8 per cent. I have seen a motor generator 

 set, where it was taking power as a motor and driving a generator, give an efficiency of 94 

 per cent, that is only 6 per cent loss in the motor and generator, including the bearings and 

 the windage, so that 14 per cent for an electrical transmission on a large scale is a little 

 strong. 



The comparisons of the Jupiter and Cyclops have been brought up. The questions 

 which this gentleman has asked I also asked the Department to explain to me when I was 

 getting material for the paper, but I did not get any more satisfactory reply than he did. A 

 comparison of that sort, based on some reports of coal consumption, is not a comparison 

 at all. It may be affected by many conditions. In point of fact, the comparison between 

 the Jupiter and Cyclops as shown in the paper of Lieutenant Robinson has an opposite 

 characteristic from that which you would expect. It shows the ships coming nearer to- 

 gether as they go to heavier loads, and a large advantage of the Jupiter at light loads as 

 against the Cyclops at light loads. The probability is, if you had a true comparison, you 

 would find that the curves, instead of converging, would separate as the load went up. How 

 they stand in relation to each other is something we cannot prove. 



I will later touch on the subject of the relation of turbines to reciprocating engines, but 

 will pass that for the moment. 



As to the question of the propellers on the Jupiter and Cyclops, the record of indi- 

 cated horse-power to shaft horse-power measured shows an advantage from the Jupiter's 

 propellers. When the Jupiter's propellers were designed I sent a drawing of the propellers, 

 which I received from Washington, to Philadelphia to Mr. Metten, and asked him how they 

 compared with the Cyclops propellers and how he thought the efficiency would compare. 

 He said he thought the propeller was a very good one and it was almost equivalent in design 

 to that of the Cyclops, but, since it ran at a speed something higher than that of the Cyclops 

 — something like 12 per cent — he thought the efficiency would be 1 or 2 per cent worse than 

 the efficiency of the Cyclops propeller. I think probably the Jupiter does show a better 

 propeller efficiency, and that it is largely due to the fact that when the Jupiter's trials were run 

 she was in quite a seaway and her propellers were held at an absolutely constant speed going 

 into the water and out of it again without shock, and with a perfectly uniform rotative 

 effort I should consider that condition favorable to the propeller. 



I think it will be shown in geared ships that the same advantage will be accomplished. 

 When they come to run big, slow-speed propellers, with steady rotation, they will be sur- 

 prised at the results obtained. I have studied the torque diagrams of engines somewhat in 

 connection with the running of alternators in parallel and in connection with various elec- 

 trical problems, and there are quite big variations. These variations in speed, if applied to 

 the grip of the propeller blade on the water, must affect it. There must be a great advantage 

 in a propeller which does not race, which rises to the surface of the water without change 



