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Aviation History
1922
1922 - 0790.PDF
even on the point of silence. With a knowledge of the fact that many parts of an air-cooled cylinder can now be safely boxed inside the crank-case, certain valve-gear details can be enclosed and can run in the normal lubricating system. With such an arrangement the author had secured silence in quantity production quite equal to any of the water-cooled engines of a similar size, and this silence has been maintained for upwards of 10,000 miles in a manner quite equal to water-cooled practice. In aircraft work in particular is water-cooling undesirable. The radiator is heavy but flimsy, there are the none too reliable flexible water joints, the dozens of points of possible leakage, etc., etc. The eventual coohng of the oil after it has collected the heat from the hot internal parts ought to provide no diffi culties in aji instance where velocity is high. The conditions of cooling oil and cooling water are very different, and have to .be attacked from quite different stand points. The fundamental differences are that whilst water will flow practically equally whether hot or cold, oil has viscosity varying very greatly with even small temperature differences. Thus oil cannot be effectively cooled by passing it through a long pipe either finned or otherwise, as the oil coming in contact with the walls of the pipe thickens and forms an excellent insulator for the hot core of oil flowing rapidly down the centre of the pipe. A large radiated oil tank exposed to the air currents available is even worse for similar reasons. One successful method is to form a radiator consisting of a length of pipe coiled in the manner of a simple spring. The oil is passed through this at a high velocity, and as the hottest, and consequently most viscous, oil passes through at the highest velocity it is flung by centrifugal force to the outer ring of the circle, and thus against the walls of the ring of tubing. Another system is to use tubes like ordinary radiator tubes, and to insert in these a close-fitting spiral, like a cork screw, slid into a pipe carried the whole length of the tubes, thus imparting a circular motion to the oil. The author said that his experience was that the walls of the crank-case form the best medium. These can have ribs cast upon them, and the oil can be projected by force against the inner walls, this being readily performed by the crankshaft and other rapidly moving parts within the crank-case. In the case of an air and oil-cooled aircraft engine of the radial type the majority of the cylinder barrel could be submerged into the crank-chamber, leaving a natural sump and enabling bulk oil in circulation to be used instead of the m H The International Air Congress, London, 1923 A STRONG Executive Committee under the chairmanship of Maj.-Gen. Sir F. H. Sykes, G.B.E., K.C.B., C.M.G., M.P., has taken in hand the organisation of the International Air Congress which is to be held in London from June 25 to 30 next year. National Committees have been formed in several countries to prepare lists of names for membership of the Congress, and in other countries lists are being obtained through the Aero Clubs or other representative bodies. Membership is limited to those countries which are members of the Federation Aeronautique Internationale or signatories of the International Air Convention. The subscription is to be £1 (or its equivalent in foreign currencies) for a Member DECEMBER 28, 1922 usual method." The crank-case could be formed with radial ribs, and could conveniently be used as the streamline nose- piece to the aeroplane ; tlius the whole unit would be self- contained both as regards its internal and external cooling, and it should show a high degree of accessibility. With a vertical or V-type air and oil-cooled engine a small separate oil-cooling radiator would probably have to be placed in some exposed position, but the many other advantages of air-cooling, with its added accessibility, reduction in weight and freedom from narrow temperature limitations, would still be obtained. The extent to which oil or internal cooling can be utilised is by no means obvious, but that it does form an integral part in the effective cooling system of any high-duty engine there can be no possible doubt. The author regretted he was unable to give any figures as to the amount of heat that is dissipated from the walls of a crank-case, but he had taken many readings of crank-case temperatures, and these have thrown much light upon the heat-radiating capacity of such. A normal water-cooled aircraft engine of 250 nominal b.h.p. did not attain its maximum crank-case temperature until it had been running for 1J hours on full load. Its temperature was then 270° F., and it was not provided with any means of cooling the oil. The superficial area of the crank-case was approximately 17 sq. ft., and attention is directed to the possibilities of heat radiation from such a surface at the temperature indicated. The immersing of the greater part of the cylinder barrel in the crank-case added from 5 to 20 per cent, more heat to the oil, according to the amount immersed. The author stated that oil-cooling possesses great advan tages when used in connection with road vehicles in elimi nating noise. The more the air-cooled cylinder barrel is inserted into the crank-case the more are the conditions of a water-cooled engine obtained as regards type and volume of sound. In concluding, the author pointed out that it is not seriously suggested that oil-cooling can be a complete and effective system as opposed to either of the two systems in_ common use. Its greatest advantages are found in connection with the simpler system of air-cooling, where it can assist to an extent as high as 30 or 40 per cent Even in existing engines a few simple modifications to the lubricating system can improve the effectiveness of the cooling to quite a considerable extent, and the author thought the possibility of improvement by these means justified these notes. H H and 10s. for an Associate Member, who must be a member of the family of a Member. The papers to be read are divided into four groups, which will hold sessions simultaneously, and will cover every aspect of the subject, from fundamental scientific problems to such matters as passport regulations and the organisation of an aerial transport company. The Air Ministry have arranged to hold the Royal Air Force Pageant on June 30, the final day of the Congress. Mr. C. V. Allen having resigned, Lieut.-Col. W. Lockwood Marsh, the Technical Secretary, has been appointed General Secretary of the Congress, the official address of which is—c/o The Royal Aeronautical Society, 7, Albemarle Street, London, W. 1, England. » m H H H A D.H.9b, with Rolls-Royce " Eagle " engine, remodelled by the Aircraft Disposal Company. 790
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