DISCUSSION ON MAY MEETING PAPERS. 21 



in the two units. The thrusts are not loaded, but these are not a part of the gears, and as 

 they are only located in tlie casing for convenience of manufacture they should not be in- 

 cluded in the gear losses. The results are corrected for motor efficiency. The oil service 

 and lubrication are the same as for actual service. 



In the case of the destroyer gears a number of tests were run with various loads and 

 speeds so as to obtain a curve for the efficiency over a range of speeds and powers. The 

 curves for the actual tests are shown for one-quarter, one-half, three-quarters and full power 

 torque, each over a range of speeds (see Fig. 4, Rate 8), and from these further curves have 

 been developed showing the efficiency at various speeds, powers and revolutions at which 

 the machinery would work in the ship, Fig. 5, Plate 8. It will be seen that the maximum effi- 

 ciency is 98.3 per cent at full torque and about one-half speed. In a ship, however, this 

 condition is not used and the maximum efficiency is only 97.3 per cent. The bearings of 

 these sets are very ample and account for the major part of the friction loss. Further ex- 

 periments were made with shortened bearings and showed a gain in efficiency, but the curves 

 are given for the actual gears as installed. 



A summary of other tests is contained in Plate 9. 



Test No. 2 was made on units of single reduction gears for the passenger ships for the 

 U. S. Shipping Board. These units were designed for a normal horse-power of 10,000, but 

 the test was made at 12,000 shaft horse-power as shown with a gear efficiency of 98.1 per cent. 



Test No. 3 was made on units for passenger ships similar to No. 2, but designed for 

 12,000 shaft horse-power. These were made at a later date and the improvement is shown 

 by the increased efficiency. 



The fourth test was made on a pair of double reduction gears with compound turbines 

 and was carried on continuously for eleven days. The conditions were maintained very nearly 

 constant and the efficiency, 96.8 per cent, is very good for this type of machine. 



Column 5, Plate 9, is for a similar set of gears with improved bearings, an arrangement 

 which resulted in increasing the efficiency to 97.3 per cent. 



The author is indebted to Mr. P. C. Day for the information on these reduction gear 

 tests and to the Falk Company for permission to use them ; also to the DeLaval Company, 

 Westinghouse Manufacturing Company and the General Electric Company for the informa- 

 tion and data furnished by them. 



DISCUSSION. 



The Chairman : — Gentlemen, I think it is sufficient for me to say that you have been 

 favored with the presentation of two papers as simple, as complete and as understandable 

 as any papers that have been heretofore presented on these same subjects. 



The field is open to you all now for discussion. You can discuss both papers at once 

 if you please, and it is advisable for the speakers to come to the front, in order that they 

 may be more easily and readily understood in all parts of the hall. The floor is open. 



