BATTLESHIPS. EXPERIENCE GAINED ON THE JUPITER. 205 



I strongly recommend all interested in this subject to read Lieutenant Robinson's papers 

 in the Journal of the American Society of Naval Engineers for November, 1913, and May, 

 1914, which deal largely with the Jupiter, and in one of them the author specially refers to 

 the question of personnel, which is a vital factor in the ultimate success of this form of 

 drive. 



Lieutenant Robinson, his brother officers and mechanics are to be heartily congratu- 

 lated on the great success they have achieved with the pioneer installation of electric motors 

 for propelling a large ocean-going vessel. 



Mr. Wentworth (Communicated) : — Mr. Lovekin, following me in this discussion, 

 took the stand of doubting my hurried figures as to the efficiency of the turbo-electric plant 

 described by Lieutenant Robinson. I have confidence, as we all should, that data presented 

 before such a Society as this should be as carefully prepared as possible. The following sub- 

 stantiates the statement made on the floor. 



Efficiency at 1.66 pounds of coal per horse-power hour (48-hour test) : 



33,000 X 60 = 1,980,000 foot-pounds per horse-power hour 

 divided by — 



14,000 X 1.66 X 778 = 18,080,000 foot-pounds per horse-power hour in fuel used. 



1,980,000 -=- 18,080,000 = 10.95 

 per cent actual efficiency based on Mr. Robinson's figures. 



Efficiency based on 2.50 pounds of coal per horse-power hour (24-hour test) : 



33,000 X 60 1,980,000 _ ^ 



14,000X2.50X778 ~ 27,200,000 - ^-^ P^r cent efficiency. 



Allowing a calorific value of 14,000 for the coal used, the efficiency on the discussed 

 plant would run from 11 to 7 per cent. If the coal were higher grade the efficiency ranges 

 would be less and greater with inferior grades of coal. 



Assuming that the vessel in question had been equipped with oil-burning boilers and as- 

 suming that the figures presented in the paper of the writers on the oil engine to be correct, 

 1 pound of oil in the oil engine would do the work of from 3.50 to 5 pounds of oil in a turbo- 

 electric plant similar to the one described. This comparison is more favorable than the one 

 made on the floor, where 1 pound of oil in the oil engine was only considered to be equal to 

 3 pounds of oil in the turbo-electric plant. 



This is a small matter to bring up, but the writer has endeavored to always take care in 

 making statements of an engineering nature and to confine himself to such statements as he 

 could show figures to substantiate. 



The Chairman: — It is unfortunate that the author of this most interesting paper is 

 not present. Members were rather reluctant to begin this discussion, but seem to have gotten 

 a good headway after beginning. 



The resolution offered by Mr. Lovekin, while undoubtedly sympathetically received by 

 most of us, is of a character the Chair will not put as a motion at this time, because chair- 

 men are very reluctant to set precedents. But we can most heartily — we have already done 

 so, in fact; and I am sure we will do it again — express our great appreciation of the work 

 done by Mr. Emmet in making possible what I cannot help but feel is an epoch-making per- 

 formance in marine propulsion. I am very kindly disposed to all three methods of propul- 

 sion, but in the brief period during which this particular method has been under trial, I have 



