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November, 1909 TAe Marine Review 441 Experimental Spur-Wheel Reduction- Gear for High Speed Steam Turbines Introductory. BOUT six years ago, Rear Admiral George W. Melville, ex-engineer in chief, United States navy, and John H, Macalpine, consulting engineers, un- dertook at my request a thorough in- vestigation of the then existing status of the steam turbine as applied to the _ propulsion of ships, and the probabilities of its becoming the ultimate successor of the highly developed types of recip- rocating engines commonly used for that purpose. The data gathered in the course of the investigation and the' conclusions drawn therefrom, were embodied in an exhausting and interesting report which was delivered to me by its authors in May, 1904. Because of the universally recognized high -- standing of Admiral Melville and his as- sociate as. authorities in matters pertaining to marine architecture and engineering, and because the report was such a complete, temperate and logical exposition of the marine steam turbine situation at that time, I considered that the information collected was of more than passing. personal interest, and I had a limited number of copies of the report printed for private circulation, in order that others might benefit by a plain dispassionate statement of fact, stripped of the fanciful embellishments with which' a novel departure from established lines of practice is apt to be adorned unconsciously by over-en- thusiastic advocates. The report of May, 1904, was not of a very encouraging nature, but in the few years that have intervened, there have been developments which effect 4 radical change in the situation existing at that time. This original report has been incorporated as a supplement to the accompanying description of certain in- teresting and important work that has been carried out by The Westinghouse Machine Co, at East Pittsburg, .Pa., under the direction of Messrs. Melville and Macalpine, and by comparison, it gives one a vivid impression of the Tapidity with which history is made in the engineering art. The most significant statement in the report of May, 1904, is to be found in the conclusion. "If one could devise a means of rec- onciling, in a practical manner, the neces- sary high speed of. revolution of the turbine with the comparatively low rate of revolution required by an efficient It reads as follows:-- -- propeller, the problem woutd be solved, dnd the turbine would practically wipe out the reciprocating engine for the pro- pulsion of ships. The solution -of this problem would be a _ stroke of great genius." There could be no greater tribute: to the far-seeing and well-balanced judg- ment of the authors of this report, than the fact that nearly five years later this identical sentiment was publicly voiced © not only by James Denny, of Denny & Brothers, Dumbarton, Scotland, the old- est and most experienced builders of turbine-propelled vessels in the world, and the most consistent advocates of the system, but also by the Honorable Charles Algernon Parsons himself, by whose brilliant creative imagination, the basic idea of the modern marine tur- bine was conceived, and by whose cou- rageous initiative it was made an ac- complished fact. James Denny Voices Same Sentiment. The parallelism of thought is so un- usually striking that I quote the utter- ances of Mr. Parsons and Mr. Denny verbatim, as reported. Mr. Parsons, in concluding his James Watt anniversa lecturs, delivered at Greenock, Scotland, on Jan. 15 of the present year, said :-- "We might naturally speculate as to the future, and inquire if there is a possibility of the turbine being con- structed to run more slowly, and with- out loss of economy, or whether the propeller can be modified to allow of higher speeds of revolution, Or, again, may the solution be found in reverting to some description of gearing--not the primitive wooden spur gearing of half a century ago, but to steel gearing cut by modern machinery with extreme acu--- racy and running in an oil bath, heli- cal tooth gearing or chain gearing, or again, some form of electrical or hyd- raulic gearing? These are questions which are receiving attention in some quarters at the present time, and if a satisfactory solution can be found, then the field of the turbine at sea will be further extended." Mr. Denny, in his presidential address to the Institution of Marine Engineers, in "Britain, on Oct. 5, 1908, said: "Tt has frequently been suggested that if some inspired engineer would evolve a system of gearing that would be last- ing and reliable, not too motsy, and would not absorb in friction more than say, 10 per cent of the power, turbine engines would be capable of application to any speed of vessel, and to any size of propeller; you would then have a high-speed turbine and a low-speed pro--- peller, which is the ideat condition for marine propulsion." Solving the Problem. The problem first recognized by Messrs. Melville and Macalpine, and the importance of which has since been ad- mitted by Mr. Denny and Mr. Parsons, has been solved. It has been solved by Messrs. Melville and Macalpine them- selves, so that by one of the amusing freaks of fate, the compliment to the then unknown 'solver, implied in the last sentence of the paragraph quoted from their report of May, 1904, comes back to rest upon its unsuspecting makers. ' The desired end has been accomplished by means of a reduction gear, which makes possible any reasonable speed ratio between the turbine shaft and the propeller shaft. It was no easy task to design a system of gearing that will operate quietly and without destructive wear at the speeds common to steam turbines of the highest efficiency, and at the same time be capable of trans- mitting thousands of horsepower. The details of the design that has proven it- self capable of fulfilling these require- ments, are fully set forth in the able ard comprehensive article reprinted from Engineering (London, Sept. 17, 1909), which is based on data supplied by Messrs. Melville and Macalpine. How- ever, a few additional words of a non- - technical character, generally descriptive of the gear, and indicative of its sig- nificance as a factor in marine construc- tion, will not be out of place. Description of the Gear. The teeth of the gears are helical, that is to say they do not run straight across the face of the wheel parallel to the axis, as in the case of ordinary spur gears, but they are cut in the form of a steep spiral, like an exaggerated screw thread. This construction allows the teeth to roll into contact without shock or jar. If there were only a single gear on each shaft this helical form of tooth would cause an objectionable end thrust. As the gears must be very wide to transmit the enormous powers required in marine service two gears, each of half the required width, are placed on each shaft, with the spirals of