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Aviation History
1926
1926 - 0237.PDF
APRIL 8, 1926 THE S1DDELEY "JAGUAR'S" 17,000 MILES A Triumph for the Air-Cooled Engine THE wonderful performance of the Armstrong-Siddeley" Jaguar" engine, which Mr. Alan Cobham used on his London-Cape Town-London flight, has undoubtedly empha-sised the remarkable advance that has been made of late in the design of the air-cooled engine. In fact, there arenow many people who are of the opinion that the air-cooled engine is the engine of the future as far as aircraft are con-cerned—and recent performances of this type of engine have certainly demonstrated that many of the objections asso-ciated with it are unfounded, and that it is well able to hold its own in competition with its water-cooled rival. This isan important point, for, of course, under certain conditions the air-cooled engine possesses considerable advantages. When Mr. Cobham's " Jaguar " was stripped down andmeasured up by the Aircraft Inspection Department of the Air Ministry, the greatest amount of wear discovered in anypart was but 0-002 in.—the thickness of a hair, in fact. In such vital parts of the engine as the pistons, piston rings,gudgeon pins, cylinders, master rings and bushes, crankshaft, plexity of the problem that faces the aero engineer beginsto be realised. To this must be added the fact that there is a constant call for still more power, coupled with a demandfor a reduction in weight, an achievement which in the case of the " Jaguar " engine enabled Cobham to take off from someof the high altitude African aerodromes where previous attempts had met with disaster. The report of the official A.I.D. inspection of Armstrong-Siddeley " Jaguar" engine No. 8010, used by Alan Cobham in the D.H.50 is as follows :—. Pistons.—No wear. All gudgeon pin bosses O.K.Grooves.—O.K. No cracks. No wear on diameters. Piston rings and scraper rings.—No wear and still within limitsof strength. Gudgeon pins.—O.K. to limits. No traceable wear.Gudgeon pin bushes.—Bores O.K. No wear. Outside diameter worn from 0-000£ in. to 0-002 in.Cylinders.—No wear. Inlet valves.—Seats very good. Stem diameter no wear. 17,000 MILES AND FIT FOR MORE : The component parts of the Siddeley "Jaguar " engine used by Mr. Alan Cobham on his 17,000-mile flight from London to Cape Town and back laid out for inspection by the A.I.D. The latter's report, given in the accompanying article, shows that the engine is in remarkably good condition, and that the amount of wear is " infinitesimal." crankshaft bearings, anchor pins and tappet rollers, it wasimpossible to detect any wear whatever, while in many other parts the production limits for a new engine were not evenexceeded. An examination of the engine parts, which we were able toinspect the other day, bears out the A.I.D. official report, which accompanies this article. The freeness of the cylinderheads from carbon deposit is a notable tribute to the efficiency of aircooling, as is the excellent condition of the valves andvalve seats. That fundamentally vital part, the white metal lining of the master ring, is in perfect condition, while thewonderful appearance of the pistons and the excellent fit and condition of the rings are prominent points. These results would have been remarkable enough for aseries of straight flights in Europe, but when it is remembered that the engine which was hauling a. load of 4,400 lbs. wasdeluged for hours in African rain and sandstorms, and was frequently pegged out for the night under almost barbaricconditions, the infinitesimal amount of wear that is shown in the report is little short of miraculous. It proves, of course,the tremendous strides that have been made not only in the designing of the parts themselves and in the provision madefor their protection and lubrication, but also the advance that has been made in the selection and treatment of the mostsuitable material. Furthermore, when it is remembered that the modernaero engine may be called upon to operate in temperatures varying from 115° F. to 90° below freezing point, the com- Exhaust valves.—Seats very good. Three valve stems'only show wear of 0-00J in., and this only on a period of half length.Inlets guides.—Two valve guides worn. Rest O.K. Exhaust guides.—Two valve guides worn. Rest O.K.Master ring.—No traceable wear. Master ring bushes.—Diameter of bushes O.K.Auxiliary connecting rods.—Eleven O.K. No wear. One oval in large bore by 0-00025 in.Anchor pins.—These are O.K. No wear. Anchor pin bushes.—Inside diameters O.K. Outside diameters worn 0-0005 in.Crankshaft.—No wear. Tappets and guides.—No wear.Tappet rollers.—O.K. Tappet roller pins. —Wear 0-0002 in.Main crankshaft bearings.—Condition excellent. No wear on races. Wear on rollers 0-00025 in.Mote.—The engine, when tested on the bench at the conclusion of the flight, was found to be in perfect runningorder, and showed no loss in power throughout the range of the power curve. The fuel consumption varied between 0-56 to 0-58 pintper brake horse-power per hour and the oil consumption was 6 pints per hour. As will be seen from the above figures the engine is inremarkable condition, and the amount of wear that has taken place is infinitesimal. 205
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