50 DISCUSSION ON MAY MEETING PAPERS. 



weight of machinery, therefore, including spares, engineer's stores and water in the sys- 

 tem, is thereby reduced by using the proper installation from 795 tons to 540 tons. Also, 

 the fuel oil consiunption is reduced from 13j4 tons to 9j^ tons per day, as actually ob- 

 tained on the motor ship Oregon. For the motor ship the cargo-carrying capacity, both cubic 

 and deadweight, will be correspondingly increased, which taken with the decreased cost 

 of machinery will show a decided economical advantage for the motor ship over the steam 

 vessels for the particular route in question. Mr. Femald has failed to take cognizance of 

 the fact that the twin Diesel vessel will have a better propulsive efficiency than the single- 

 screw vessel, due to the revolutions assumed for the latter. The results arrived at by 

 him are therefore incorrect and extremely misleading. 



Messrs. Smith and Dalcher, of the Federal Shipbuilding Company, have also investi- 

 gated what advantages there may be in the motor ship and have furnished an estimated 

 comparison by them of a vessel with geared turbines and Diesel engines. From the data 

 (given, the Diesel installation is apparently based on an experimental engine, which 

 is unusually heavy for the power. The shaft horse-power estimated as required for the motor 

 ship is about right, but the power used for the geared-turbine vessel is considered too small, 

 due to the high turns of 90 revolutions per minute employed for the single screw, and which 

 should not exceed 75 revolutions per minute for the particular conditions if the propulsive 

 efficiency of the two vessels is to be kept the same. Had B. & W. engines, type 6-275 (erro- 

 neously used in Mr. Femald's comparison, and exactly suitable for the present vessel) been 

 employed, the machinery would have been reduced from 1,052 tons, as given in Mr. Dal- 

 cher's figures, to 795 tons, or a saving of about 25 per cent. Mr. Dalcher has used 0.35 

 pound of fuel oil per indicated horse-power, all purposes at sea, giving 14.55 tons per day. 

 If this is corrected to 0.31 pound, as obtained on B. & W. vessels, the consumption per day 

 is reduced to 13 tons. Had a more suitable Diesel-engine installation been selected for the 

 comparison, the 19 per cent net earnings per year on the initial investment, as given, would 

 have been very greatly improved and would conform more with the figures of the authors 

 in their comparison. 



Referring to Mr. Huskisson, of the Vickers Company, it was not the intention to criti- 

 cise the Vickers engine in particular, which is known to be of fairly high compression and 

 is about the only marine engine of the solid injection type to date that has met with any 

 degree of success for marine purposes. As to the Vickers engine being entirely free from the 

 troubles enumerated, reference is invited to some comments by Mr. David P. Peel regarding 

 his experience with Vickers submarine engines, in which he discusses the smoking and knock- 

 ing in cylinders. This is to be found in the Transactions of the Institute of Marine 

 Engineers, volume 31, February, 1920, pages 566-572. The authors can also speak from 

 experience gained with a four-cylinder 500 horse-power experimental engine of this type, 

 and the company with whom they are associated is building very satisfactory solid injec- 

 tion stationary engines for lower powers. It should be pointed out that Vickers' experience 

 has been mostly with submarine work, and, to the knowledge of the authors, they have 

 only three merchant vessels in operation, which are of comparatively small power. Subma- 

 rine engines are operated only for short periods at full power and frequently come into 

 special bases prepared for their overhaul, while merchant motor ships must operate a long 

 time at full power and away from home without any special attention. We fail to see 

 wherein the accident cited by Mr. Huskisson as occurring to an ex-German vessel has any 

 logical bearing on the matter in the absence of trouble of this kind with standard air-injec- 

 tion engines. 



