ELECTRIC PROPULSION OF SHIPS. 135 



Mk. Ernest H. B. Anderson, Member: — This paper has resulted in bringing out 

 many interesting points during its discussion, 1:)ut it seems to me that Mr. Thau has given 

 the Society no definite information regarding the fuel consumption performance of steam 

 electric-geared vessels. 



There must be a great deal of data available, and there is too much doubt about the fuel 

 consumption performance of such ships; this applies to naval vessels and also to ships of the 

 merchant marine. 



For instance, there are eleven freighters Wihich are having the original mechanical geared 

 turbines replaced by electric gearing. The first of these, the Eclipse, has completed a voyage 

 of 26,000 miles and, as far as one can learn, the machinery worked splendidly throughout 

 the voyage, but nothing reliable has been published regarding the fuel consumption. Com- 

 petent authorities who have had an opportunity of studying the "engine-room log" state 

 that the oil fuel consumed by the main engines and auxiliary machinery averaged about 1.30 

 pounds per S. H. P. per hour. Further, it should not be overlooked that the boilers were 

 equipped with superheaters giving 200° F., and in view of this the reported performance of the 

 machinery is poor. 



A double-reduction geared steam-turbine vessel operating under the same conditions has 

 a fuel consumption of 0.90 pound of oil per S. H. P. per hour for all purposes. 



It seems to me that the builders of the electrical machinery in these freighters did not 

 quite do justice to the system they were advocating, for it was necessary to increase the revo- 

 lutions of the propeller from 90 to 100 per minute, which is hardly suitable for a freighter 

 of 16,000 tons, displacement and sea speed of 10.50 knots. Shaft revolutions of 75 to 80 

 would have ensured a much better performance, but to accomplish this mechanical gearing 

 of the single-reduction type would require to be ari'anged between the propelling motor and 

 line shafting. This arrangement was adopted by Llungstrom in the vessels Mjolner and 

 Wulsty Castle, where two motors are in parallel, each driving a pinion in mesh with one 

 gear wheel. 



Dealing with warships, in view of the great interest taken in the machinery installa- 

 tions of the battleships New Mexico and Idaho, Nos. 40 and 42, respectively, Plate 23 shows 

 a plan view of the propelling machinery, and it will be seen that the engine-room spaces in 

 these two ships are alike, but the propeller revolutions at the designed power and speed in the 

 New Mexico are 170 per minute, whereas in the Idaho they are 240 per minute. Needless 

 to say, the slow-turning propellers of the former have a considerable advantage over the latter. 



Whilst bids for battleships Nos. 40, 41 and 42 were in hand during 1914, geared-turbine 

 machinery was making rapid progress, and we submitted alternative proposals with this type 

 to the shipbuilders, and two firms offered to build these battleships with geared turbines driv- 

 ing four shafts, as shown on Plate 24. 



Battleships Nos. 43 and 44, Tennessee and CaHfornia, were designed during 1915, hav- 

 ing a four-shaft arrangement of "electric gearing" for the propelling equipment, in which the 

 machinery arrangement is absolutely novel as compared with all previous battleships. 



We submitted alternative propositions to the Navy Department, but it is almost impos- 

 sible to install or arrange mechanical geared steam-turbine machinery in spaces specially de- 

 signed to suit "electric gearing." 



Plate 25 shows a plan view of the Tennessee and California arrangement of machinery 

 and a proposal having twin screws, driven by two sets of Parsons single-reduction geared 

 steam turbines. The revolutions of the electric-geared ships are 170 per minute, whereas 

 in the twin-screw turbine proposal they are 125 per minute. 



