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Aviation History
1951
1951 - 0261.PDF
FLIGHT, 8 February 1951 163 FOR SAFETY in CONTROLS Preventing Risk of Incorrect Assembly of Chain-and-Cable System T^VERYONE concerned with aircraft design and maintenance-L/ is aware of the dangers of control-reversal inherent in assembly of sprocket-and-chain systems of actuation and of thevarious measures which have been taken, officially and unofficially, to guard against them. Briefly, there are four pitfalls, and they lie in the risk of: —(1) Connecting the wrong ends of operating cables of the same system. #(2) Connecting ends of operating cables belonging todifferent systems. (3) Reversing the chain end to end on its sprocket.(4) Allowing the chain to gear on the wrong face where two sprockets are operated by the same chain.The established practice for dealing with eventualities (1) and (2) is the use of non-interchangeable connectors, but this failsto cover (3) and (4). Existing regulations stipulate that all sprockets should be pro-vided with a close-fitting guard to prevent the chain riding the sprocket, and this requirement is fully met in the arrangementshown. A standard chain could be accommodated in four dif- ferent positions on the wheel by virtue of its ability to gear ontwo faces and its reversibility end to end; but with the chain designed as in Fig. 1, in conjunction with (a) a shroud onthe sprocket -and (b) the chain guard, only one position is possible, as shown in Fig. 2. An attempt at assembly in anyother way will cause the chain to fou! in a manner that will be immediately apparent and, indeed, make the control totallyunworkable. At the same time, the ability of the chain to gear on bothfaces is not sacrificed. Such a requirement can arise when more intermediate sprockets are to be operated or toothedjockeys are used, and the required direction of rotation is not the Fig. I. One of the extended plates whi the basis of the system. The large hole in the plate is for lightening purposes. GUARD NON- INTERCHANGEABLE CONNECTORS NON-INTERCHANGEABLE, CONNECTORS e^_a "'- Illustrated here is a method which the Renold and CoventryChain Co., Ltd. (28 Deansgate, Manchester, 3), has submitted for S.B.A.C. standardization and which, in conjunction with theuse of non-interchangeable connectors, effectively guards against all four contingencies. Fig. 1 shows the design of the chain. It consists of standardparts, except that extended outer plates are arranged at appro- priate intervals, preferably of four pitches. The weight aspectis observed by placing the extended plates on one side of the chain only, making the extension as small as possible andproviding it with a lightening hole. Fig. 2 illustrates the principle of operation. The aim inthe first place is to prevent end-to-end reversal of the chain. This is achieved, first, by providing a shroud on one side ofthe wheel and, secondly, by making use of the chain guard. ! INCORRECT CORRECT *—WHEEL'X" • 2. llluTtrations>#*ttfeyihr\e>:ases of rrect assembly, showing how the extension- would foul either the guard (A and C) or The shroud on the sprocket (B). At D the correct and only possible assembly is shown ; it is seen in side elevation immediately above. Fig. 3 (left). This view shows how, by an appropriate arrangement of guards, the chain can be used with jockey-sprocket or similar layouts. same for all points. This case is illustrated in Fig. 3 wherethe arrangements at wheel " Y" are as in Fig. 2 but where wheel " X " is required to rotate in the opposite direction andmust, consequently, gear with the other side of the chain. The chain can be placed only on the underside of that wheel. The complete system thus involves four features, viz., theirreversible chain, the guard in compliance with standing regulations, the shroud on the sprockets and, finally, non-interchangeable connectors in accordance with present practice. The Renold and Coventry Chain Co. state that although theyhave acquired the Raddings and Pearse chain patent (recently referred to in Flight), the design which they have submitted tothe S.B.A.C. embodies a feature not covered by this patent. In order to make their system freely available to the aircraftindustry they have not applied for a patent. SUCCESSFUL APPBENTICES AT BROUGH THE twentieth annual presentation of apprentice bonusawards took place at Brough recently, when over 180 apprentices at Blackburn and General Aircraft, Ltd., saw J. W. Headley receive the S.B.A.C. Certificate of Apprenticeship. Mr. J. Hall, the company's development engineer, presided and Mr. T. Bancroft, general works manager, presented over £120 in awards to the 74 successful trainees. Amongst those present were Mr. T. A. Wolstenholme, apprentice-supervisor, and Mr. Walker, principal of the Hull Technical College, together with some of his colleagues who instruct at evening classes and on the Diploma Course in Aeronautics. Results in the Diploma Course were notable, inasmuch as 12 out of 13 students were successful and, of these, eight obtained distinctions in one or more subjects. The most out- standing student was David Needham, who is now studying for the Diploma of the College" of Aeronautics, Cranfield; in his examination he obtained six distinctions and was awarded the Higher National Diploma Prize of the Institution of MechanicalEngineers. A total of 117 apprentices attended evening classes, and 63per cent were successful in their examinations. C. Rodgers obtained his Higher National Certificate and eleven apprenticesobtained their Ordinary National Certificate, whilst M. V. Brignall headed the Merit List. MR. W. E. GOUGH MEMBERS of technical staffs on the engine side of theindustry, in particular, will be sorry to learn of the death of Mr. W. E. Gough, A.M.I.E.E., who was well known tomany of them by virtue of his work on the aircraft-magneto design staff of the British Thomson-Houston Co., Ltd. After serving in the First World War, Mr. Gough joined themain B.T-H. works at Rugby as an apprentice, and in 1922 went to their magneto works at Coventry, where he began thespecialization in aircraft-engine ignition which continued up to the time of his death. He was 50 years of age.
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