52 DISCUSSION ON MAY MEETING PAPERS. 



Mr. Dickinson, of the General Electric Company, has misinterpreted the meaning of the 

 authors in reference to the importance of electrically driven auxiHaries for motor ships, espe- 

 cially in regard to deck machinery. The individual Diesel drive for the winches, as sug- 

 gested by Mr. Dickinson, would no doubt be the most efficient arrangement if such were prac- 

 ticable, as there would be no electrical losses involved. In a motor ship, however, the elec- 

 trical link is necessary to make the power of the auxiliary engines, primarily an accessory to 

 the main engine, available for deck use. This does not imply, as we are led to suppose, that 

 the electrical system, per se, is accountable for the low port consumption with a motor ship, 

 as by replacing the auxiliary Diesel sets by a steam-driven set this oil consumption in port 

 will be more than trebled. Mr. Dickinson's strong defense of the Diesel-electric drive can 

 readily be understood, but the Diesel-electric drive, which is quite a parallel case to the 

 steam-electric, runs contra to the history of all engineering development, which shows that 

 efficiency, simplicity and cost are the deciding factors. The electric drive is deficient in each 

 respect, and the fact that twelve of the Shipping Board's geared-turbine vessels are being 

 changed over to turbo-electric drive is due to good salesmanship and not good engineering. 

 The first of these installations has been in service since November, 1920, and has steamed 

 approximately 20,000 miles with the electric drive, during which her logs show that she 

 actually consumed 10 per cent more fuel than when equipped with her original geared tur- 

 bines, which, by the way, operated with 50 degrees superheat while the turbo-electric drive 

 operated under 200 degrees superheat. 



Mr. Warriner's figures for a motor-driven ore ship are of particular interest on account 

 of being of two-cycle design, and we presume are based on the Cubore installation. It again 

 furnishes an illustration of the superiority of the four-cycle engine, had such been used in 

 the comparison. By replacing the two-cycle engines with four-cycle of same cylinder dimen- 

 sions as the motor ship William Penn, but of eight cylinders each, the normal shaft horse- 

 power would be increased 7 per cent and the total weight of machinery, including boiler, 

 reduced at least 100 tons, since the total installation without boiler for the four-cycle will 

 be 1,050 tons. The fuel consumption per day becomes 19 tons instead of 24 tons, with a 

 corresponding increase in cargo capacity of 140 tons. Accordingly, the total increased cargo 

 carrying capacity will be 240 tons more than with the two-cycle vessel. Using the same basis 

 of comparison as used by the authors in their comparison, the cost of crew per day for the 

 motor ship becomes 12.3, with repairs and provisions same as for the steamer. The cost of 

 fuel is reduced to 6.48, giving a total operating cost per day of 89.56 compared with the 96.38 

 for the particular two-cycle installation. The four-cycle will be seen to be better than any of 

 the three other drives used by Mr. Warriner in his comparison. It can be safely stated that 

 on the long trade routes the large direct-driven motor ship, where proper care is made as 

 to proven types, will show a greater earning capacity on the investment over all other drives, 

 irrespective of variations in freight rates and fuel prices. 



Mr. Warriner : — I wish to thank the members who have taken part in the discussion 

 for their very interesting contributions. 



Owing to the nature of the two papers, these have resolved themselves somewhat into a 

 debate of Diesel vs. reduction gears; it was not, however, the intention in writing the paper 

 to make out a case for the reduction gear at the expense of the Diesel engine and, personally, 

 I am very much in favor of the Diesel engine because it means economy in fuel consump- 

 tion, and economy is the goal that engineers are always striving for. 



