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Aviation History
1957
1957 - 0206.PDF
208 FLIGHT, 15 Fdmtary 1957 "HOT ENDS" Gas Turbine Component Manufacture by Briggs Motor Bodies, Ltd. r — ALTHOUGH Briggs Motor Bodies, Ltd., have been regularA\ exhibitors at the S.B.A.C. Exhibition since the war, the •*- -•>• extent to which these well known automobile-industrysuppliers are involved with the supply of aircraft gas-turbine components is not, perhaps, generally realized. In point of fact,the company manufactures a very large percentage of British gas- turbine "hot ends". A transition from mass-produced car bodies to the manufactureof high-precision gas-turbine components is far less drastic than would at first appear. Both involve the pressing and forming ofsteel sheet and (mainly) assembly by welding, to a very high standard of accuracy. In this sense, the work is far more closelyrelated to automobile practice than it is to the traditional products of either the aero-engine or the airframe producers. Although Briggs Motor Bodies, Ltd., were in the Merlin pro-duction group during the war, the present activities had their origin in 1949, when Rolls-Royce, Ltd., called upon the com-pany's vast experience of sheet-metal work to help in the production of the Avon nozzle-box panel. This initial connectionwas consolidated in 1951, when the Ministry of Supply brought the company into the re-armament programme—particularlywith the super-priority Rolls-Royce Avon and Armstrong Siddeley Sapphire and Double Mamba.To accommodate the work, some 250,000 sq ft of the former Cunliffe-Owen Aircraft factory at Eastleigh Airport were leasedfrom the M.o.S. and largely equipped by a capital assistance agreement with the Ministry. Key personnel came from themain Briggs works at Dagenham, but most of the labour had to be recruited locally in the Southampton area-—which must havebeen quite a task in competition with the established local aircraft companies, also embarked upon the super-priority programme. Representative examples of "hot end" components made at Eastleigh: they include an Avon RA.7R reheat jet-pipe; Avon 100 series com- bustion chamber parts; a Sapphire annular combustion chamber and a secondary air tube plate assembly; Mamba and Sapphire bearing housings; a Mamba outlet branch exhaust; a Sapphire exhaust cone assembly; and Sapphire and Double Mamba oil tanks. By following through from the initial impetus of the rearma-ment programme Briggs have built up, in six short years, an unsurpassed "know-how" in the manufacture of this very newtype of component. The result is that, even though the aircraft programme has passed its zenith and is being increasingly rapidlyrun down, so many engine manufacturers have now come in of their own volition that there is no shortage of work. Today, onecan see on the floor at Eastleigh, in addition to the original variety of Armstrong Siddeley and Rolls-Royce components,parts for Blackburn and General Aircraft Turbomeca engines, for several Bristol types, and for the Napier Eland and Gazelle. Inthe last two cases there is, perhaps, a subtle compliment implied in the fact that the principal components are the "difficult"bifurcated jet pipes. Since the aero-engine work was started there has been amarked progressive change in its character, owing to the advances in gas-turbine design. Originally it largely consisted of whatis colloquially known as "canware"; that is to say, the can-like individual combustion chambers. This type of part is evolved bya lengthy process of deep-drawing operations on presses—per- haps as many as nine passes, with frequent heat treatments.This form of chamber was made for the Derwent, Avon and Double Mamba. The true annular combustion chamber of the (Upper left). Three examples of "canware": Left to right: Double Mimba (twelve per engine), Avon 100 series (eight) and Derwent (nine). (Upper right). This Armstrong Siddeley annular inner flame-tube is representative of the second stage of combustion chamber development. The spot-welded crimped rings are the "sine-wave cooling" air inlets. (Lower left). Typical exhaust-cone assemblies—I. to r. special Avon cone tor the Comet; an early Sapphire unit, with the outer casing which protects the Alfol lagging; and a standard Avon cone. (Lower right): Cranked exhaust cone for the Double Mamba—a compact assembly which belies the skill and intricacy of its manufacture.
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