DISCUSSION ON MAY MEETING PAPERS. 53 



As brought out in the papers and in the discussion there is a difference of opinion as to 

 the relative economy of the two types of machinery, not on the score of fuel consumption, 

 but of the operating costs, and at the present time, with the high cost and the limitation in 

 power of the Diesel engine, both types of machinery have their proper fields ; for one service 

 it will be found that the Diesel engine is more adaptable, and for other services the reduc- 

 tion gear will give the best results. It is advisable, before settling the type of machinery, to 

 take into consideration all the circumstances and to select that which furnishes the 

 best results. 



Mr. Fernald, in his paper, remarks that Great Britain and Scandinavia have, for the past 

 few years, swung over to the motor ship almost exclusively. So far as Great Britain is 

 concerned, this is not an altogether fair remark. According to the Shipbuilding and Ship- 

 ping Record of April 21, the following is the proportion of steam and motor ships building 

 in Great Britain and the United States, on March 31, 1921 : 



Description. Gross tonnage. No. of ships. 



Great Britain Steamers 3,530,364 794 



Motor ships 263,180 66 



United States Steamers 1,048,914 142 



Motor ships 34,232 8 



Mr. Smith states that the oil consumption for the two-cycle Diesel quoted in Table I 

 is 0.515 pound of fuel oil per shaft horse-power, which is correct for all purposes, but the 

 actual figure used in the calculations was 0.42 pound of oil per shaft horse-power for the 

 main engine. The remainder is for auxiliary purposes — heating cargo oil, running cargo 

 pumps and allowance for bad weather. 



Regarding the use of the gravity system for lubricating oil, it is believed that this is 

 the best installation and that it is now generally adopted. Those who have had experience 

 with both systems prefer the gravity system. 



Mr. Clark's contribution is particularly interesting, and the results of the test on efficiency 

 by the Westinghouse Company, though taken in an entirely different manner, generally con- 

 firm the test made by the Falk Company. 



In reply to Mr. Atkinson's remarks, as will be seen from the curve sheet, Fig. 4, Plate 8, 

 the gears were run up to full speed or 450 revolutions per minute with the full-power tooth 

 pressure and bearing loads, the results being shown on the top curve. 



Mr. Anderson takes exception to the statement in the first paragraph of the paper, but 

 the discussion on gears was intended mainly for those built in the United States. The author 

 was unable to obtain first hand information on other gearing, and it would, no doubt, be 

 interesting to all concerned if Mr. Anderson would furnish particulars of gearing data he 

 may be able to obtain for gears built in Great Britain, including length of operation. The 

 author is at one with Mr. Anderson on the subject of single-reduction gears, and would pre- 

 fer these instead of double-reduction gears, wherever the circumstances allow. 



In regard to the formulae for tooth pressures, it does not seem very material whether 



P P 



-yr or / — is used, providing the constant is properly selected. It is believed that the figures 



given are fairly conservative and would produce good results with properly constructed gears. 

 The following lantern slides were shown at the meeting : 



