40 DISCUSSION ON MAY MEETING PAPERS. 



electrically, simplifying valve and operating gear. Maneuvering air bottles, air compressors, 

 reverse mechanism and much other mechanical complication are eliminated. 



4. No Propeller Racing. — Engines run at constant speed and motor speed under con- 

 trol in rough seas. No vibration transmitted to engine. 



5. Fewer Auxiliaries. — Only one auxiliary generating set required, if any. With elec- 

 tric starting, no starting, air tanks or compressors required. 



6. Flexibility. — Efficient operation at all speeds — at reduced speed only enough engines 

 operated to supply the required power. 



7. Space Savings. — Machinery space 25 to 30 per cent less, due to small moderate speed 

 engines. 



8. Weight Saving. — Diesel electric weight considerably less per horse-power than direct 

 Diesel. 



9. Single Screw. — Single-screw construction can be used, reducing hull cost and increas- 

 ing propeller efficiency. 



10. No Shaft Tunnel. — With engine amidships and motor in stem, shafting and 

 tunnels are eliminated; saves weight and gives undivided cargo space. 



11. Bridge Control. — Duplicate control station may be located in the pilot house; of 

 great value for certain classes of ships for particular service. 



12. Special Cases. — Diesel electric drive has particular advantages in double-ended 

 ferries, tugboats, yachts, self-propelled barges, fishing trawlers, fire-boats, submarines, etc. 



Mr. W. J. Flanders and Mr. E. F. Clark, Visitors: — In connection with the third 

 paragraph of the paper by Mr. Warriner we would like to call attention to Mr. Hodgkin- 

 son's closure of the discussion of his paper presented before this society at its Philadelphia 

 meeting, November 14, 1918, in which he states : 



"I think there can be no doubt but that the present great expansion in the adoption 

 of high-speed gearing, whether for shipboard or land use, was pioneered by Melville and 

 Macalpine. Their first large reduction gear was tested in 1909, the patents having been 

 applied for in 1907. The result of their work was published quite generally and was com- 

 mon knowledge both in Europe and the U. S. A. at the time of the Vespasian in 1910. Sir 

 Chas. A. Parsons had experimented with gearing previous to this, but we learn from the 

 Transactions of the Institute of Engineers and Shipbuilders in Scotland, vol. 44, page 216, 

 that he had given up hope of success." 



In regard to the development of marine gears one must agree that it was too rapid for 

 best results, but it is to be feared that the bad results obtained in certain cases were due 

 to oversight rather than lack of proper knowledge of the requirements. 



The oil must, of course, be of good quality, but a viscosity of 450 seconds at the ac- 

 tual running temperature seems to be higher than is desirable. The gear teeth as well as 

 the bearings will generate more heat with oil of low temperature and high viscosity than 

 they will with the higher temperature with the correspondingly lower viscosity. As the 

 frictional loss will vary very nearly as the viscosity, it is obvious that this viscosity should 

 be kept as low as possible consistent with safe operation, and there does not seem to be 

 any reason to doubt that, with properly designed gears accurately cut, viscosities as low as 

 200 seconds Saybolt under actual rtmning conditions should be employed. 



I think everybody will agree with the author that a ship is generally quite flexible and 

 that it is practically impossible to design a gear casing which will not be affected by the 

 movements of the ship's hull. A casing which could be actually supported on only three 



