202 THE APPLICABILITY OF ELECTRICAL PROPULSION TO 



Suppose your steam plant has an efficiency of 14 per cent, do you not lose 10 per cent of 

 this, owing to the extra machinery interposed ? Then, again, do you not lose around another 

 10 per cent on account of the interest charges on this extra plant? I think you do. Then, 

 again, where your steam-engine efficiency is limited to around 12 per cent, is it not possible 

 to build a reciprocating oil engine in which the efficiency (based on brake horse-power) 

 shall be over 36 per cent, and perhaps over 40 per cent? I think this will be found to be 

 true, if thoroughly investigated. By that I mean, analyze your fuel, get your British ther- 

 mal units, multiply your British thermal units by 778, and get your foot-pounds of energy 

 in one pound of coal, then divide these foot-pounds by 60X33,000; that will give you the 

 horse-power hour that you can get out of 1 pound of oil for 100 per cent efficiency, and you 

 will find you will have to use perhaps 2.5 pounds of oil to get the work that you figure out 

 from 1 pound of oil (this is for an oil engine 40 per cent efficient). 



What can the constructor and ordnance expert not do with this saving in fuel weight 

 and machinery weight, or what can the tactician not do with this increased radius of opera- 

 tion? The solution of the problem of coaling at sea shows up the advantage of fuel econ- 

 omy in that connection. 



Is it worthy of the engineer to waste his time and to spend such amounts in unneces- 

 sary machinery for a gain of fractional percentages in efficiency, and disregard the possibility 

 of an increase of 300 per cent in efficiency coupled with a corresponding increase in either 

 speed, steaming radius, or offensive and defensive qualities, or a happy combination of these 

 three factors producing a better all-round battleship ? 



Mr. Luther D. Lovekin^ Member: — I have taken quite an interest in this proposition 

 of electric drive during the last year. I have sympathized with Mr. Emmet very much in the 

 past five years in his efforts in the direction of introducing the electrical propulsion for bat- 

 tleships, and I congratulate him now on the success which he has thus far achieved. Re- 

 cently I have had occasion to engineer some vessels, one of them about 8,000 horse-power, 

 and one of much larger power. I investigated the geared turbine proposition, one of which 

 we are building, using oil fuel. I also investigated the oil-engine proposition, and last, but 

 not least, the electric drive. The oil engine has many disadvantages, contrary to the state- 

 ments of the previous speaker. We know that an oil engine runs at about J^ pound of oil 

 per horse-power, and we also know that we have geared turbines now that can go on 1 pound 

 of oil per horse-power, for all purposes, so that there is hardly a ratio of three to one. With 

 the electric drive we can do equally well. 



As regards the efficiency, I have not gone into that question very deeply, but I know it 

 is more than 1 1 per cent, or we would not be using it. The great advantage that we found 

 in the electric drive for high powers over others was in the high propulsive efficiency we could 

 get. 



In Mr. Robinson's paper, where he refers to the advantages due to the use of twin 

 screws, exception might be taken to the statement of twin screws being used on battleships of 

 large power, but inasmuch as I have had occasion quite recently to design an installation of 

 power in which 45,000 brake horse-power could be used on one screw, and yet retain its effi- 

 ciency, I think that for our Navy, at least, we can count on twin screws being entirely 

 within reason. There is no doubt about our being able to use twin screws for a battleship of 

 at least 90,000 brake horse-power. Of this I am positive. 



As regards fuel consumption, I feel safe in stating that we can get along with less 



