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Aviation History
1922
1922 - 0057.PDF
JANUARY 26, 1922 " Messrs. Rolls-Royce have introduced into the ' Condor ' engine an interesting development comprising a bush which serves as a sort of universal joint. This bush, which is first fitted to the engine bearer tubes, has a spherical portion over which the actual engine feet are bolted. A close working fit obtains between the bush and the engine foot, so that should the bearers for any reason be thrown out of alignment or distorted temporarily by landing shocks, etc., the undue stressing of the crankcase which would occur if the feet were rigidly fixed, is obviated. Another feature of the same system is that provision is made for any longitudinal expan sion of the crankcase by leaving the two bushes for the rear engine feet free to slide along the bearer tube, while the two front bushes remain fixed to the bearers." The lecturer expressed the opinion that there is an inex plicable lack of uniformity in the types of engine controls . Positive-acting rod types are the most satisfactory, especially when the details are well designed and made. Controls should all be marked clearly to indicate their purpose and direction of operation. Even then the different levers should be quite distinctive either by position or shape. Oil systems are usually of a simple character, and the lecturer confined himself to calling attention to the impor tance of fixing the oil tank above the pump to guard against failure due to suction leaks. The question of water-cooling systems is one of very great importance, and was dealt with at considerable length by the lecturer. After pointing out the difficulty of deter mining originally the size of radiator for any particular machine, owing to the many variables encountered, General Bagnall-Wild gave the following table, based upon numerous tests carried out. The atmospheric temperature is taken to be that of the average English summer conditions, i.e., 23° C. :- A B Altitude Temp. Atmos. Boiling in feet. Fall. Temp. Point. °C. (Assumed °C). (Approx. °C). 00 23 100 2,000 3 20 98 4,000 6-4 16-6 6 6,000 9-4 I3"6 94 8,000 13 10 2 10,000 16-4 6.6 89-6 Cowling is, the General stated, a much more difficult matter. With an air speed of 60 m.p.h. and the engine fully exposed, between 44 and 55 percent, of the water-jacket heat can be dissipated by the engine itself. For efficient cooling it has been found that the exposed engine would require a rate of water circulation per 100 h.p. of n gallons per minute, while the cowled engine would require 22 gallons per minute. As engine water pumps cannot, of course, be designed to meet both of these conditions, a minimum of 15 gallons per minute is now specified for service aircraft. While dealing with the question of petrol systems and tank-disposition, the lecturer mentioned how these may affect the problem of fire risk. There are, however, other safe guards against fire which were indicated at some length. This important subject has been dealt with by the Fire Preventions Committee, and a summary of the recommendations made by this committee, which were recently published and endorsed by the Air Ministry, was given by the lecturer. They are now made a condition in all new service aircraft. One very important item in the running of commercial aircraft is the accessibility of its engine for inspection and adjustment. This subject was very ably handled by the lecturer, who called attention to a number of details which affect the accessibility of an engine and the ease with which it can be " got at." He also suggested that in multi-engined machines it would be advisable if the designer gave the matter of easy removal careful consideration. It might be possible, he said, so to arrange the design that, with suitable ground equipment, the engine could be drawn along its bearers on to the ground apparatus sufficiently far to enable it to bs picked up by a lifting gear. We believe that, as a matter of fact, some such system is already adopted by Vickers for use with the " Vimys " at their Weybridge works. In conclusion. Gen. Bagnall-Wild turned his attention to the question of engine starting and ignition systems. He dealt with the various forms of starting gear now in use, and concluded by saying :— " It is my view that in future we must concentrate on the <J> <•> Retailers and Commercial Aviation IT should be helpful that the Incorporated Association of Retail Distributors are interested in the Air Conference next month. At a meeting last week the Council appointed auxiliary engine starter, with which promising results are already in sight. Briefly, the system now in use consists of a small air-cooled two-cylinder unit, one cylinder serving only as a pump and connected by a distributor valve to each of the main engine cylinders in turn. The pressure developed is sufficient within a few seconds to start up the auxiliary engine and to turn the main engine, filling the cylinders at the same time with a suitable explosive mixture, the auxiliary engine pumping cylinder being fed from the small engine carburettor." The Discussion The Chairman, Col. O'Gorman, then called upon Mr. Handley Page to open the discussion. This Mr. Handley Page did by first thanking Gen. Bagnall-Wild for a very solid contribution to aeronautical science by his valuable paper. Regarding the question of co-operation between engine designers and aircraft designers, he pointed out that during the War this was a matter of some difficulty, not to say impossibility. To take one example, his own firm was developing the large twin-engined machine, while Rolls- Royces were developing their engine, with which the H.P. machine was to be fitted. Yet so secret was the work of each considered that they were absolutely forbidden to communicate with Rolls-Royces at all. Even now it was a matter of some difficulty to attain the necessary co-operation. Personally he considered the engine the bugbear of aircraft design. What he would like to see, in order to render possible direct-gravity petrol feed, was an engine running with its cylinders turned downwards instead of upwards, which would bring the carburettor low down and also have other advantages. He thought that the ideal for multi-engined machines would be air-cooled engines with gravity feed. Capt. Wilkinson said that as Mr. Handley Page had stated that he considered the engine the bugbear of the aircraft designer, he (Capt. Wilkinson) would say that he considered the aeroplane the bugbear of the engine designer. He would suggest that a great deal might be done if aircraft designers would get together and agree upon a few simple standard mountings and attachments, and thought that it should be possible to standardise, say, three different mountings for each type of engine, so as to suit all types of machines. Gen. Sir Sefton Brancker said that first of all he would like to congratulate the Air Ministry on their choice of a new D. of R. (Gen. Bagnall-Wild), and then stated that personally he was all for the air-cooled engine. It seemed to him stupid to carry gallons of water about which was always either freezing or boiling when you did not want it to, and which meant extra complication, when already there was all around you an excellent medium for cooling in the simplest possible manner. He called attention to the fact that of the engines used in the East during the War, the one which always seemed happy and never gave any trouble due to cooling problems was the old air-cooled R.A.F. 4A. With regard to the lecturer's suggestion that it should be possible to change the engine in a very short time and so avoid trans ferring the cargo or passengers to another machine during a long voyage, he thought this was a most excellent idea and quite an original one, as far as he was aware. He did not see why, if designers applied themselves to the problem, it should not be possible to change an engine for a fresh one in about 10 minutes. As regards commercial machines, he would plead for simplicity and strength, even at the expense of a certain amount of weight. Wing-Comdr. Briggs also pleaded for close co-operation between engine and aircraft designers, and said that he had found that exhaust manifolds were a source of trouble. Maj. Heckstall-Smith thought it would be very helpful to people who, like himself, did not have ready access to such statistics, if tables of accidents and their causes were made available. Maj. Wimperis said he would like to pay a tribute to the work done by the late Maj. Norman in experimenting with fire prevention. This work had been of an extremely hazard ous nature, and no one could realise the value of the work done, and the courage and determination necessary for carry ing it out. He called attention to a statement in the lecturer's paper which mentioned the placing of the petrol tank as far aft as possible. This placing would, he thought, tend to prevent the necessary minimum head of 18 in. from being maintained during a steep chmb. He also stated that it had been found that in certain cases, if the hand-starter magneto was near the compass, the latter was upset. <5> <$> Mr. T. Ernest Jackson, secretary, to represent the Association at the Conference, who will report upon the position of civil aviation and the transport of merchandise by air, as he may view it after the two days' sitting at the Guildhall. 57
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