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Aviation History
1924
1924 - 0625.PDF
SEPTEMBER 25, 1924 THE ENGINES USED IN THE COMPETITIONS IN view of the fact that, although the prizes at Lympne are to be awarded for certain performances of the machines, the real test will largely be one of engine power and engine reliability, inside the limits imposed by the 1,100 c.c. capacity permitted as a maximum, very considerable interest attaches to the engines employed in the various machines, as upon them will depend to a great extent the success of the tests. With the exception of the Bristol " Cherub," which has, as already announced in FLIGHT, passed its Air Ministry air worthiness tests, the engines used are largely of an experimental character, either having been evolved barely in time to be in the machines or having been converted from their original form to suit the special conditions obtaining in light 'plane work. There must, therefore, necessarily be a certain amount of speculation as to how this and that type will stand up to the extremely strenuous conditions of the competitions, and incidentally it would appear that any engine, whether it has already obtained its airworthiness certificate or not, which comes through the trials with flying colours will have demonstrated its suitability, and might, we think, be granted a certificate of some sort, even if the rules and regulations H E THE A.B.C. THE A.B.C. " Scorpion " light 'plane engine is manufactured by A.B.C. Motors of Walton-on-Thames, and is a modification of the A.B.C. car engine. It is of the flat twin type, air-cooled, and with a bore and stroke of 87-5 mm. by 91-5 mm. respectively. The aluminium crank-case is divided laterally, a spigoted joint being used. The two-throw crankshaft runs in ball bearings at the back and in roller bearings at the governing airworthiness tests are such as to preclude the Air Ministry from giving it the regulation certificate. It will be realised from the fact that machines will have to do at least 150 miles at full power in the high-speed tests, probably 300 miles or even 450 miles, and complete not less than 10 hours' flying during the week, not to mention repeated attempts at low-speed, take-off and pull-up, that the engines will by no means be having an easy time of it, and one of the greatest uncertainties, apart always from the question of weather, is how the engines will fare. There may easily be some surprises in store in this connection, and in a way this adds a certain amount of interest to the whole competition. Below we give a brief description of each of the four engines taking part. In the case of two of the engines it has been impossible to obtain from the manufacturers, in spite of repeated applications, particulars of bore, stroke, volume, weight, power output, etc.. as well as illustrations, although as regards the latter some idea of the outward appearance of the engines in question may be gathered from the photographs of machines in which the engines are shown in situ. "SCORPION" convert the " Scorpion " for aircraft work by merely crossing- over the push-rods, the inlet valves becoming exhaust valves and vice versa. It should be realised that the whole engine has been reversed compared with imposition in a car—i.e., the side which was front in the car becomes the back in the aeroplane, and the propeller is mounted where, in the car engine, the flywheel is. For aeroplane work, of course, no TWO VIEWS OF THE A.B.C. "SCORPION ": These photographs were taken while the first engine was being tested, and shows it with flywheel in place of the propeller fitted when the engine is used for aeroplane work. The induction pipes have also been rearranged. front. A short camshaft runs in one plain bearing and one ball bearing, and operates the overhead valves by push-rods and rockers. The cylinders have detachable heads containing the overhead valves and valve gear, and the heads are generously ribbed to provide good cooling. Owing to the fact that the cylinder speed of 3.000 r.p.m. and weighs about 93 lbs heads are perfectly symmetrical, it has been possible to sion ratio is 5 to 1. flywheel is fitted, although one is shown in the photographs. These, however, were taken on the test bench, and show the first converted engine while it was still run with the flywheel in place. The A.B.C. " Scorpion " develops about 30 b.h.p. at a The compres- H EI H E THE BRITISH ANZANI CONCERNING the special 1,100 c.c. engine developed by the British Anzani Engine Co. of Scrubb's Lane, Willesden, we have been unable to obtain any information whatever. In spite of repeated applications to the makers neither photo graphs nor particulars have been forthcoming, and we are, therefore, unable to do more than give a very brief account of the features of this engine, which we have seen fitted in several of the machines. The British Anzani engine is of the motor-cycle type— i.e., it is a vee-twin air-cooled engine, with overhead valves operated by push-rods and rockers. There are four valves to each cylinder, two inlets and two exhausts, so that the engine should prove verv efficient and should be capable of a considerable power output. In one or two of the machines in which it is used, it has been mounted " upside-down," the reason for this mounting being that a bettef view is obtained over the nose of the machine, while gravity feed to the car burettor is facilitated. The short induction pipes on the Anzani are doubtless designed for efficiency, but they neces sitate a very high carburettor position. When the engine is reversed the carburettor is brought down a considerable distance, and sufficient " head " is obtained. 625
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