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Aviation History
1911
1911 - 0234.PDF
|p]CHT] elastic motor gives an average working torque of 2'75 ozs. at 2 ins. radius, we will work to that torque (don't mix it up with the pull of the elastic yet). We will stretch the elastic three times. Working from curve III, since -J in. square equals four strands of x'e in- square and gives a pull of 29 ozs. when the stretch = 3, sixteen strands of TV in. square (or its equiva lent cross section) will give us 116 ozs. pull under the same conditions. Notice in passing that this is a good big pull for the frame and the various bearings. As we are working to average torque, we must at this stage work to average pull, taking curve III as a straight line, the average pull is half the above amount, viz., 58 ozs. and since we have two winding drums to serve we must take half of this again to find the diameter. therefore, where x = the radius of the drum required to give the torque from this pull :— 2-7S x 2 ins. = 29, _ 2#7S x 2 29~~ x = -19 (in.). So each winding-drum must be (say) -4 of an inch in diameter. As the elastic is stretched from 1 ft. to 3ft. there is 2 ft. of silk (" thread " is hardly strong enough for nearly 8 lbs. pull) to wind on the drum. Then— 2<t (inches) - •,'•;•." = Revolutions 2 x '19 x T = 20. Revolutions of the propellers. And that is all you can get. From the figures given in FLIGHT, NO. 38, this skein of •elastic used as a twisted elastic motor would have given 145 revs, and the same torque, i.e., it would have stored up three and a half times (there are two propellers used) the power, and as there is nothing like the same amount of machinery about it, its plant efficiency would have been higher, an important point in flying where the motor always has to lift its own weight. There is no need to work out any further dimensions, but I would point out that there are twelve bearings, four of which have to work under a pressure of nearly 4 lbs., and for which the ordinary ball-thrust bearing is not suitable. I do not agree that the " same power and revolutions " is ensured to each propeller; on the contrary, as they cannot be wound up together (by one person) and must not be wound up separately, unless they are geared together, I don't see how they are to be wound up at all, unless some key that temporarily gears them together is used. The guide pulleys would have to be provided with some kind of feed, or they would not travel along the winding- drums. Tf some such drums could be used, they ought to be conical, and thus keep the torque constant ; as it would be necessary to start winding at the base and wind down to the apex, they must be provided with a helical groove to carry the silk, and so on. I have dealt thus fully with this particular suggestion as I wish to illustrate the point that even ingenious model- makers are often in too much of a hurry to " see the wheels go round," and should spend more time in making a few quantitative tests, such as the four curves given above, before trying to design the finished article ; and that a record of such tests by others would be very useful to all similar workers. I must apologise to " Buitre" for using him thus, but it is not all my fault; his idea was, as I said, attractive, so much so that I have to thank him for the pleasure and in struction I have derived in finding out what it would do. Earl's Court. W. LANGDON-DAVIES. Model Propellers. 1115] In answer to Mr. Batho, I think if he tried a geared motor with the elastic (advertised in FLIGHT, January 21st , it would run at a higher speed. But, of course, it might be that the propeller is not set at the right pitch. Limpsfield. D. A. HANSARD. MARCH I8, 1911. IMPORTS AND EXPORTS, 1910-11. AEROPLANES, airships, balloons and parts thereof (not shown separately before 1910). January... February Imports. 1910. 1911. £ £ 2,516 1,196 437 3,129 Exports. Re-Exportation 1910. 1911. 1910. 1911. £ £ £ £ 750 1,088 550 Nil 2,950 1,786 — — 2,953 4,325 3,7oo 2,874 550 Aeronautical Patents Published. Applied for in 1910. Published March 16th, 1911. 2,247. J' KNAPP. Balloon envelopes. 4,042. H. AND H. A. SANDERS. Aeroplanes, &c. 6,689. W. H. SAYKKS AND W. R. DING. Securing lateral stability in aeroplanes. 19,204. W. W. GIBSON AND D. W. HANBURY. Flying machines 20,951. A. H. BAILY AND — CLEVELAND. Flying machines. "FLIGHT" ART PAPER EDITION. IN response to numerous requests, the publishers of FLIGHT have arranged to print a limited number of copies each week upon art paper, thereby enabling the high quality of the illustrations and matter to be fully appreciated. These can only be supplied by subscription, the annual charge, post free, being : United Kingdom, 15.?. ; Abroad, 20.T. Present subscribers can secure these copies by paying the difference pro rata of their unexpired subscriptions. Application should be made to the PUBLISHER, 44, ST. MARTIN'S LANE, W.C. DIARY OF COMING EVENTS. British General Events. Mar. 24-April 1 Olympia Aero Show. June 23 .. Gordon-Bennett Aviation Cup Contest. July 22 .. Daily Mail Round England Contest. Oct. 31 .. Close of British Michelin Cup. Foreign Fixtures. April 9-21 .. German Circuit—Ulm, Frankfort, Friburg, Strasburg, Carlsruhe, Mannheim, Wiesbaden (1016J. April 16 . Dresden Meeting. April 27-May 16 German National Circuit—Aix-la-Chapelle, Cologne, Essen, Bielefeld, Brunswick, Berlin(975). May .. Paris—Bordeaux—Paris. June 4-30 .. European Circuit—Paris,'Berlin, Brussels, London, Paris. June 4-12 .. Johanniithal National Meeting. June 6-11 .. Rome Circuit. June 12-18 Rome-Turin race. PRINCIPAL CONTENTS. •—— PAGB The Coming Show 216 The Bristol Biplane (Military Type) 217 Army and Aeronautics.. .. .. .. .. .. .. .. .. 220 Royal Aero Club Notes 221 Progress of Flight About the Country .. .. .. .. .. .. 222 British Notes of the Week 3 From the British Flying Grounds 224 Hendon-Brooklands-Hendon 7 Foreign Aviation News .. .. 8 New Speed Records .. .. .. .. .. .. .. .. .. 230 German Pilot Aviators 23 Clarkson Aerocar .. 1 Problems Relating to Aircraft .. .. .. .. .. .. .. 232 Correspondence .. .. .. .. .. .. .. .. .. « 234 FLIGHT. 44, ST. MARTIN'S LANE, LONDON, W.C. Telegraphic address: Truditur, London. Telephone: 1828 Gerrard. SUBSCRIPTION RATES. FLIGHT will be forwarded, post free, to any part of the world at the following rates:— UNITED KINGDOM. ABROAD. s. d. 3 Months, Post Free 6 „ 3 Months, Post Free 6 „ s. d. 2 9 5 6 Cheques and Post Office Orders should be made payable to the Proprietors of FLIGHT, 44, St. Martin's Lane, W.C., and crossed London and County Bank, otherwise no responsibility will be accepted. Should any difficulty be experienced in procuring FLIGHT from local newsvendors, intending readers can obtain each issue direct from the Publishing Office, by forwarding remittance as above. 236
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