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Aviation History
1921
1921 - 0156.PDF
MARCH 3, iQ2t CAMBRIDGE UNIVERSITY AERONAUTICAL SOCIETY (OFFICIAL ORGAN " FLIGHT '») '" ^" v r /" ON February 9 a Paper was read by Mr. A. J. Rowledge entitled:— The Napier " Lion " Aero Engine In his introduction the lecturer stated the reasons and considerations which led to the "Lion" being designed as a " triple-four," with the central block vertical and the other two making an angle with it of 60 degrees. The short four-throw crankshaft particularly is a simple job, and although fairly light gives good rigidity. High compression was chosen because the requirements at the time of designing were an engine which would develop at least 300 h.p. at 10,000 ft. Mr. Rowledge then gave a brief description of the engine, but as a full detailed description was published in FLIGHT of March 27, 1919, we think it unnecessary to publish this part of his paper. Performance.—The nominal h.p. of the engine is 450 at 2,000 r.p.m. The actual power is 480 b.h.p. at 2,000 r.p.m. and 510 h.p. at 2,200 r.p.m. These figures were attained with a fuel consisting of 20 per cent, benzole with Aviation spirit. The brake mean effective pressure exceeds 130 lbs./ sq. in. In a recent Government test an engine ran for one hour, developing 530 b.h.p. at 2,210 r.p.m. and one hour at 490 b.h.p. at 2,025 r.p.m. Curves were then shown of petrol consumption, and the lecturer said that on long runs at rather high cruising power it had been found possible to attain a combined fuel and oil consumption of less than •5 lb. per b.h.p. hour. The total swept volume of the engine is 1,461 cu. ins., and at 2,000 r.p.m. 1 h.p. is developed for every 3*03 cu. ins. An oil consumption curve showed the valuable characteristic that the consumption is high at nigh power, and low at low power, which results in practice in an extremely low oil consumption. The heat lost to the jackets less the heat directly radiated by the engine at normal revs, is approximately 9,500 B.T.U. per minute, and this amount has to be dissipated by the radiator. The rate of water flow from the engine is • 75 gallon per minute at this speed. The weight of the engine with airscrew boss and haad- turning gear complete is 890 lbs. The weight of the complete installation, including exhaust pipes, propeller, radiator, water, cowling, the part of the aeroplane structure carrying the engine, fuel and oil tanks—in fact the whole weight of the power plant, less fuel and oil, in service, comes out at between 1,480 and 1,580 lbs., or 3-08 to 3-28 lbs./h.p. at normal revs. The fuel consumption depends very much on circumstances. In a passenger service, where speed is essential, the consumption in practice is between 20 and 25 gallons per hour. This obtains with a machine weighing 6,730 lbs. and flying at 100 m.p.h. At Martlesham the petrol consumption of one of these engines was 14-2 gallons per hour, the machine weighing 4,900 lbs. and cruising at 82 m.p.h. The fuel consumption for racing purposes might be over 30 gallons per hour. These figures also hold with the low compression engine. For commercial work with machines weighing 15 lbs./h.p. and flying mostly at low altitudes, the low compression engines give better service and nearly the same performance. The maximum b.h.p. of the low compression engine is about 7 per cent, less and the h.p. at climbing speeds 5 per cent, less than that developed by the high compression engines. The influence of weight j'b.h.p.—This is an important matter as regards cost of a commercial service. Assume that the flying qualities of the machine vary as the weight per b.h.p The structure weight of an aeroplane is a definite proportion of the total flying weight. Let A = total weight of power unit with fuel, B = total weight of structure, C = useful load, W = total flying weight, a = weight of power plant per b.h.p., b = structure weight per b.h.p., c = useful load per b.h.p., and w — total flying weight per b.h.p. Then A + B + C = W and a + b • • c = w. Taking the D.H. 18, the figures become :— A + B + C = 2,414 + 2,850 -f 1,470 = 6,730 ; or a+b + c = w = 5-36 + 6-33 + 3-26 = 14-05 If the weight of the power plant be increased by J lb./b.h.p the useful load must be decreased by the same amount, and becomes 2-76 lb./b.h.p. To carry the same load, the total flying weight has to be increased over 18 per cent, and the b.h.p. by a similar amount. In a high-performance machine or one doing long journeys, this point becomes much more important. Finally the lecturer called attention to some general considerations of small bulk to give low head resistance, and pointed out how the " Lion " scored owing to the disposition of the cylinders in W formation. He also showed slide* of various installations of the "Lion," and lastly some slides of the new Napier " Cub." THE ROYAL AERONAUTICAL SOCIETY Lectures.—At the last meeting of the present session on March 17, Capt. D. Nicolson, M.I.N.A., Associate Fellow, will read a paper on " Flying Boat Construction." Notices to Members.—Notices of the Annual General Meeting, which is to be held at 5 p.m. on Thursday, March 31, are now being posted to all voting members, and should be in their hands by Monday, the 28th, at the latest. Besides "the notice a copy of the present Rules, together with the Council's proposed amendments, and a card of membership, are enclosed in each envelope. The Council's proposed regulations for the examina;ion of candi- dates for Associate Fellowship will be sent with the Council Election ballot papers on or before March 21. The Council's Annual Report and Accounts will be found in the March issue of the Journal. Manchester Association of Engineers.—At the request of the Manchester Association of Engineers, it has been arranged for the Chairman (Air Commodore H. R. M. Brooke-Popham, C.B., C.M.G., D.S.O., A.F.C.) to read a paper on " Some Problems in the Design and Operation of Aircraft " before the members of that body at 7 p.m., on March 2. Donations.—The Council desire to acknowledge with grateful thanks the gift of a set of lantern slides from Messrs. Vickers, Ltd., which will be added to the loan collection of the Society. W. LOCKWOOD MARSH, • • , Secretary •'••"•""•• •••*•'••» m m Round Denmark ON Saturday last, two Danish naval aeroplanes are reported to have made a complete flight, the first, round Denmark in 11 hours. The distance is about fxx> miles. INSTITUTION OF AERONAUTICAL ENGINEERS Council Meetings.—The Council met on February 14, and February 21. Elections.—Pilots: J. Whitworth Jones, F. H. Solomon. Associate : John Williamson. General Meeting.—The General Meeting for the presentation of the Council's Report and Balance Sheet for the year 1920 will take place, at 8 p.m., at the Royal Society of Arts, on March 15. Lecture.—The next lecture will take place at 8.30 p.m at the Royal Society of Arts, on Tuesday, March 15, when Dr. A. P. Thurston, M.I.Ae.E. (Hons.), A.M.I.Mech.E.. will read his paper entitled, " Some Points in Aircraft Stru< tural Design." Members who would like to receive an advance copy of the paper, with a view to taking part in the discussion, should notify the Secretary.DOUGLAS SHAW, • —~ • Secretary B K K X An R.N. Armoured Car Lodge IT is intended to found a Masonic lodge among tbe officers, petty officers and ratings who served during the War in the Royal Naval Armoured Car Division. Will those who are interested in the project, and particularly those who are Freemasons and would like to becoiw founders, communicate with Lieut.-Commander W. Whittall, 14, Elm Bank Mansions, Barnes, S.W. 13 ? Air Force Costs IN written answers in Parliament last week, the Secretary of State for War gave the following figures as the estimated monthly cost of the Air Force at present in the plact* named :—Ireland, £33,000 ; Mesopotamia, £73,000 ; Palesttm £23,000 ; Constantinople, £3,000. 156
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