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Aviation History
1934
1934 - 1216.PDF
1218 FLIGHT. NOVEMBER 15, 1934. aDility and economical cost of operationare two of its best recommendations. It is a seven-cylinder single-row radialavailable in direct drive, geared and/or supercharged forms. The seven cylindersare arranged round a barrel-type crank case which supports a one-piece balanced crankshaft, the -connecting-rod assembly-being of the split master rod and plain auxiliary rod type. Cylinders are inter-changeable with those fitted to the "Jaguar," with steel barrels machinedfrom forgings screwed into aluminium alloy heads. THE BRISTOL AEROPLANE COMPANY, LTD. NINE-CYLINDER radial engines havefor long been the speciality of the Bristol Company. The company's namewas made famous by the '' J upiter '' engine. This type was succeeded by the"Pegasus" which, like its forerunner, is enjoying widespread popularity.In the company's current programme there is, in addition to the Series II" Pegasus " tyrrs, a new range of engines known as the "Mercury" VI, "Pega-sus " III and " Pegasus " IV, which will be in full production in 1935. Themarked increase in performance obtained with these engines is due to the use ofthe high-octane fuel. An increase of about 15 per cent, in power output, withimproved fuel economy under cruising conditions, has been obtained. Otheroutstanding features are the complete range of accessories, provision of auxi-liary drives for special items of aircraft equipment, choice of three gear ratios foreach engine, and the standardisation of controllable pitch airscrews. On the cylinders, the barrels of whichare of hardened alloy steel, ample cool- ing area has been provided to ensurea generous margin of cooling for the conditions imposed by high power outputin low-drag cowlings. Sodium cooled exhaust valves have been standardised.The crankshaft and connecting rod assembly have been re-designed to copewith the higher engine speeds and im- proved materials have been used. In itsnew form the crankshaft is surface hardened all over, and, as a result ofthe exceptionally hard bearing surface provided by this treatment, togetherwith the higher fatigue range afforded by the new material, the life of thisdurable component is further prolonged Full skirted forged pistons have alsobeen standardised. The introduction of surface-hardened cylinder barrels andmodifications to the piston Ting design ensure that oil consumption is main-tained at a low level despite the increased speeds of rotation of the engines. Thecarburetters incorporate a delayed-action pump permitting positive and rapidacceleration to be obtained with economical tuning for cruising, and aslow running cut-out to prevent a hot engine continuing to '' slow run'' afterswitching off. A boost control of the automatic servo type is employed. Although the standard reduction gearratio for all engines is 0.5, the "Mer- cury " VI may have .666 or .572 ratios,and the '' Pegasus'' III and IV may have .572 or .444 ratios if desired. Provi-sion is made for fitting Hamilton V.P. air-screws. The 605 h.p. "Mercury" VIS is thesmallest engine of the new series, being intended for use in high-speed fightingaircraft. Normal pressure is maintained in the induction system up to 15,500 ft.Exceptionally high power for take off and climb is offered by "Pegasus" III.The maximum power is 775 h.p. The "Pegasus" IV, which is superchargedup to 15,000 ft., gives 710 h.p. at that height. Lately the company has produceda very successful compression ignition A sectioned view of the Bristol" Pegasus " 9-cyl. radial of some 600 h.p. engine- the "Phoenix" and the'' Aquila '' and '' Perseus '' sleeve-valve types. These engines are of 15.6litres and 24.8 litres capacity re- spectively, and are intended for civil use,although military versions are being developed. Hamilton V.P. airscrews maybe used. The chief advantages of the sleeve-valve engine are ease of manufac-ture and maintenance, low fuel con- sumption, and the ability to run at highcompression ratios with any fuel of given octane number. Although the manufacturers haveevery confidence in the great possibilities of these sleeve-valve engines, it is onlyin accordance with their usual policy that they require development to becomplete before putting them on the market. The Bristol " Aquila " sleeve valve engine is a smallerversion of the " Perseus '.' shown on the right. A rear view of the Bristol "Perseus" sleevevalve radial, which is rated at 520 h.p.
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