ELECTRIC PROPULSION OF A BATTLESHIP. 83 



geared turbine and his electric propulsion, why he did not show the last slide shown on the 

 screen (Plate 42), instead of the most complicated one shown by Sir Charles Parsons, 

 as the two were published in the same paper. I understand, however, that Sir Charles Parsons 

 did not advocate seriously the arrangement of geared turbines shown in Mr. Emmet's 

 papers. It was only a suggestion. 



The question in regard to having only two turbines, or a number of turbines, is one 

 worthy of consideration. It is not always by reducing the number of parts that we get the 

 best results. The officers of the Navy, I think, will bear out the statement that when they 

 come to their periodical overhauling and lifting the cases of the turbines — which is required 

 by the regulations — that they would rather lift four or eight small casings than two large ones. 

 It is true that the piping on the electrically driven battleship will probably be simpler than that 

 of a battleship fitted with the geared turbines. Mr. Emmet does not, however, mention that 

 in place of the extra piping he has electric wiring. I have heard remarks about the Jupiter's 

 outfit being simple — you get aboard this ship and see very little. However, all the wiring is 

 encased in conduits and is out of sight; if this were exposed to view a different impression 

 might be had. 



The question of economy is one which has been considered very seriously in the Navy 

 lately, and rightly so. In comparing his proposed ship to others in regard to this point, 

 Mr. Emmet makes no reference to one of the Navy's latest ships, namely, the destroyer 

 Wadsworth. The economy shown by her geared turbines is remarkable, and although we 

 cannot compare the Wadsworth with a battleship on the basis of water consumption, per 

 effective horse-power, or poimds of fuel per knot, we can, however, compare the water con- 

 sumption per shaft horse-power, and in this case the electric outfit would be inferior. Pro- 

 vided that the geared turbines were fitted with propellers as efficient as the electrical pro- 

 pelled ship (and I can see no reason why this could not be done), the water or fuel con- 

 sumption per knot would be far superior, in favor of the geared turbine. 



Mr. Ernest H. B. Anderson, Member: — Mr. Emmet's paper is most interesting, but 

 he is dreadfully hard on the designers of ordinary reciprocating engines, all of whom are 

 highly experienced men in the profession. The author informs us that an installation of elec- 

 tric motors for ship propulsion is best suited for large high-speed vessels, but I do not think 

 this method of propelling vessels will ever become popular, and any large installations will 

 really be of an experimental nature. The danger from damp and the constant presence of 

 salt, such as exists on board ship in all the engine-rooms, will be a continual source of anxi- 

 ety to the engineers. 



If the U. S. S. Jupiter does give a water rate of 11 pounds per shaft horse-power per 

 hour for the turbines only at full power and shows a good propulsive coefficient at this speed, 

 then it is a splendid performance, but it is very unfortunate that the steam consumption for 

 "turbines only" was not measured during the official trials of this vessel. 



My experience of steam consumption) measurements in terms of shaft horse-power 

 obtained from torsion meters shows that the data are rather unreliable, and if a true relation 

 between the quantity of steam supplied to a turbine and the propeller output in terms of 

 speed is desired, then the calculations should be on a basis of steam consumption in pounds 

 per knot run. 



I have plotted the coal consumption data of the Jupiter recorded on the official trials 

 with that of six other similar colliers which have twin-screw reciprocating engines, and the 

 results show in favor of the reciprocating engine ships (see Figs. 1 and 2, Plate 41). 



