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Aviation History
1911
1911 - 0023.PDF
JANUARY 14, 1911. P§ST] INTERIM REPORT OF THE GOVERNMENT FLIGHT OFFICE AND OFFICIAL RESULTS OF THE ALEXANDER COMPETITION. THE second Blue Book on Aeronautics, which forms an interim report of the Advisory Committee for Aeronautics on the work for the year 1910-1911, mainly deals with the Alexander Prize Competition for Flight Engines. In the Autumn of 1909 Mr. Patrick V. Alexander offered a prize of ^1,000 for the best motor for aeronautical purposes which should satisfy certain conditions, the most important of those being that it should pass a satisfactory endurance test. Originally the prize was offered under the joint auspices of four bodies, including the Royal Automobile Club, Royal Aero Club, The Aeronautical Society, and the Aerial League. Subsequently, however, and so far as we are aware without any formal notice of such limitation, the trial was held under the sole auspices of the Aerial League, for which body the actual tests were carried out by the authorities of the Government Flight Office at Bushey House. The appearance of the results of the tests in the form of an appendix to the above mentioned interim report is the first official notice that has been issued on the subject since the original terms of the trial were made known. Six firms originally entered their motors for trial, three only actually competed. The prize was withheld from award on the grounds that no competitor fulfilled the conditions. Of the three competitors the Wolseley Co. and the Humber Co. both suffered mishaps to their engines that placed them definitely out of the competition. The Green engine, however, completed the required twenty-four hours continuous test, but only approximately developed 31/5-b.h.p. during this period, whereas the authorities interpret the regulations to specify the necessity of developing 35-h.p. If Messrs. Green's Motor Patent Synd., Ltd., feel any dissatisfac tion at not having the performance of their engine recognised in a more substantial manner, they would appear to have some prima facie cause for discontent, for it is certainly open to argument that the rules do or do not imply that the competing engine shall be dis qualified if it does not develop 35-h.p. The clauses affecting the question are as follows :— Horse-power.—The motor to be designed to give 35-b.h.p. The machine will be required to reach this b.h.p. on a preliminary run. Test under constant brake moment.—Before the commence ment of the test the maker will be required to declare the speed at which the motor will develop 35-b.h.p. The tests will be made at a constant brake moment calculated from the h.p. and this declared speed. It is, of course, perfectly clear that the engine has to show itself capable of developing 35-h.p., and that the conditions under which k will have to work during the trial will be such as are based on the assumption that it can develop 35-h.p. The mere fact, however, that it is prominently specified that the power in question must be developed on a preliminary run at any rate leaves it open to the implication that the exact value would not be insisted upon during the entire 24 hours test. It is a matter, of course, on which the authorities reserve the right of final decision, but inasmuch as the prize was presumably intended to encourage manufacturers of flight engines, and inasmuch as no one has received that material assistance therefrom, it would seem to be only fair to give this one firm at any rate full credit for what they did. It did not need the Alexander Competition to show that flight engines are not altogether so invariably satisfactory as we feel perfectly confident they will become when the makers have had a little more time to grapple with the difficult problem involved. On the other hand, these very same engines, and we may add particularly the Green engine, have distinctly furthered the progress of aviation in England, so that behind this academic turning down of the motor in question by the authorities controlling the trial, there still stands out the altogether more important practical fact the Green engine has done and is doing thoroughly good work on actual flying machines and has incidentally just carried off the British Michelin Cup. So much at any rate for the attitude of the Aerial League and its interpretation of encourage ment towards British industries ; what the generous donor of the prize thinks about the matter may be best judged from the fact tint he has presented the makers with a cheque for £200. Balow we give the official results of the trial of the Green engine :— Description of Engine. General..—This engine has four separately mounted cast steel cylinders, machined inside and out, of 105 mm. bore, with a stroke • f 120 mm. The water jacket consists of a thin copper helmet, the joint with the cylinder at its lowest end being by a rubber ring fitting into a groove in the cylinder, so that the expansions of cylinder and helmet are independent. The cylinders are mounted on an aluminium crank-case, the holding-down bolts being carried through to serve as supports for the crank-shaft bearings. Valves.—The valves are of the mushroom spring-closed type, in detachable cases. Each valve is enclosed within a small dome, having an orifice through which the valve is actuated by the end of a short tappet pin. The cam-shaft is carried in bearings in a small oil-tight horizontal casing, divided into halves, and is rotated by an encased vertical spindle situated in front of the engine. This spindle is driven by a pair of worm-wheels from the crank-shaft. The rocking levers are pivoted in extensions of the cam-shaft case, their striking ends being provided with adjusting screws, and the ends operated by the cams with rollers. Carburettor.—This has no float chamber, and its action is inde pendent of the inclination of the engine. It is of the single jet type, and has automatic air control. Ignition.—The ignition is by high-tension magneto. Cooling.—The engine is water-cooled, the circulation being effected by a gear pump. Lubrication.—The main oil channel is cast solid with the crank- case, and from this oil is forced by a small gear pump through leads at right angles communicating directly with each of the hollow columns through which the holding-down bolts pass, and thence to the main bearings and crank-shaft, the latter being hollow. By this system the use of separate pipes is dispensed with. Bearings.—The crank-shaft is provided with bearings between each throw, and is slightly offset from the centre line of the cylinders. The ball race is designed to be used with either a propeller or a tractor. Weight as defined in Regulation 4.—219 lbs. Results of Trials. 24 hours' endurance test.—The erection of the engine was com menced on October 5th, but, owing to unavoidable delay, the preliminary run was not made until October 17th. The endurance test was commenced at 10.30 a.m. on October 18th. The engine did not run very satisfactorily during the first hour, owing to difficulties with the ignition, and after one hour's run a stop of ten minutes was made, during which new sparking plugs were fitted. Oa re-starting, the engine ran much bstter, and continued making approximately 3i"5-b.h.p. at 1,213 revolutions per minute, until the completion of the 24 hours' run on October 19th. The only attention to the engine during this period was the addition of 42 pints of oil 17 hours after the commencement of the triaJ, and an additional 21 pints 22 hours after the commencement of the trial. Other tests.—The maximum h.p. which could be maintained for seven minutes was determined on the same day without any over hauling of the engine, with the exception of grinding in the valves. The horse-power obained was 36-4 at 1,390 revolutions per minute. To test the effect of the gyroscopic action of the propeller a couple of 50 foot-pounds in a vertical plane was applied to the motor shaft for three minutes while the engine was running, but no effect on the speed and torque could be detected. To determine whether the engine would work satisfactorily when tilted about an axis transverse to the shaft, two runs of an hour each were made on the engine when tilted at an angle of 15°, first one end, and then the other end, being uppermost. The com petitors did not wish to run their engine at full load during this test, and maintained the b.h.p. at approximately 18 throughout both trials. The engine ran steadily in both cases, but it was noticed that the exhaust was decidedly smoky, apparently indicating over-lubrication. The general steadiness and freedom from vibration of the engine when running were so marked that it was not considered necessary to test it when running and placed on elastic supports. On the completion of the trials the engine was dismantled, and the working parts thoroughly examined. Very little wear could be detected in the crank-shaft and connecting-rod bearings, and the state of the cylinders and valves appeared to be quite satisfactory. The ball races of the thrust bearing at the propeller end of the cmnk -shaft were, however, considerably worn. In the crank-shaft bearings one of the aluminium caps was cracked right through for about one-third of its length. It was not certain that this crack had originated during the National Physical Laboratory tests, as there was some evidence that it existed before these trials began, but it appeared probable that the crack had become larger during the tests. In the case of one of the connecting-rods, it was found that the slerre inside the small end of the rod had rotated, so that 23 C 2
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