46 DISCUSSION ON MAY MEETING PAPERS. 



designs built and completed here were somewhat complicated as compared with those suc- 

 cessfully in operation, practically all of which were of the single-reduction tjqje. 



With regard to the destroyer Wadsworth, referred to on page 14, the informa- 

 tion regarding this installation is not quite correct. The two sets of geared-turbine ma- 

 chinery were designed to develop 17,500 shaft horse-power, with propeller revolutions of 

 450 per minute, corresjKinding to a speed of 30 knots for the vessel. The horse-power 

 transmitted by the four pinions is not equal, and whilst each high-pressure pinion trans- 

 mits about 4,000 shaft horse-power, each low-pressure pinion transmits the remainder, 

 about 4,750 shaft horse-power. 



Full particulars of this vessel, together with complete trial data records, were pub- 

 lished in the Journal of the American Society of Naval Engineers, volume 27, 1915, pages 

 640 to 662. During the standardization trials the vessel attained a mean speed of 31.64 

 knots during five runs across the measured mile, with propeller revolutions of 486 per 

 minute and shaft horse-power of 18,005. 



With regard to the author's figures outlining a table of tooth pressures for various 

 types of gearing, it seems to me that these figures should be used with caution. I have 

 looked up a number of papers on gearing and the empirical formula, where pressure in 

 pounds per inch of tooth face divided by the square root of the pinion diameter is a con- 

 stant was introduced by Sir Charles Parsons and his associates, Mr. R. J. Walker and Mr. 

 S. S. Cook. 



Reference was made to this method of treating problems in gearing during the dis- 

 cussion of Mr. R. J. Walker's paper on "The Application of Geared Turbines to Mer- 

 chant Ships," before the Northeast Coast Institution of Engineers and Shipbuilders, 

 December 19, 1919. 



Engineer Commander H. B. Tostevin, D. S. O., R. N., also made use of this formula 

 in a table of gear proportions for naval vessels in his paper, "Experience and Practice in 

 Mechanical Reduction Gears in Warships," before the Institution of Naval Architects, 

 March 26, 1920. 



More recently, Mr. R. J. Walker and Mr. S. S. Cook have thrown further light on 

 this subject, and the particulars of actual data given in their paper, "Mechanical Gears, 

 of Double Reduction, for Merchant Ships," before the Institution of Naval Architects, 

 March 19, 1921, are most valuable. 



I should like to mention that it is the practice of the Parsons Marine Steam Turbine 

 Co., Ltd., to make the load per inch of tooth face directly proportional to the diameter of 

 the pinion for sizes up to 10-inch P. C. D., and for larger pinions the load is proportional 

 to the square root of pinion diameter. 



With designs prepared in connection with my own work, I have suggested that for 



P 



pinions up to 8-inch P. C. D., the value of the constant — may vary between 60 and 65 



P 



for maximum loads, and for larger sizes of pinions the constant , — should be 170 for 



maximum loads. 



The proportions of the gear teeth, and the helical angle, should also be given consider- 

 ation in connection with using constants of this nature. 



The foregoing constants apply to installations which are operated at full power for 



