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Aviation History
1937
1937 - 2182.PDF
Light Work AN ingenious light-operated electrical relay has lately been produced. Selenium and photo-electric cells have been in use for several years for bringing various kinds of lighting system into action at sundown, but, in most cases, these entail the additional help of costly and delicate equipment which needs fairly frequent attention. The new Chilowski light relay operates on a photo-chemical principle depending upon the electrolysis of dilute hydrochloric acid. If a glass container is filled with equal volumes of hydrogen and chlorine gas and exposed to sunlight, the gases combine instantly (or with a slight delay, depending upon the intensity of the light). In darkness no combination occurs. In the glass container which forms the basic part of the Chilowski instrument, electrolysis ot the dilute acid produces the hydrogen and chlorine. On the production of the gases pres sure is increased, thereby operating a switch through the agency of a flexible portion of the container (or, alternatively, by moving a mercury column) and automatically lighting, say, the parking lamp of a car. Should the gases now be exposed to sunlight they combine to form hydrochloric acid gas, which at once redissolves in the aqueous acid solution, so releasing the pressure and operating the switch to put out the light. This simple device, which should have applications in aeronautics, has been produced complete as a disc two inches in diameter and half an inch in width, the weight being inly two ounces. The French firm Soci6te Tubest of Fere-en- Tardenois aie developing this patented relay, while Inter national Technical Developments, Ltd., of Thames House, London, S.W.i, are watching their interests in this country. Alloys and the Atlantic IT may truly be said that the Short Empire Caledonia, of Atlantic fame, is a light alloy flying boat, for apart from many tons of aluminium alloys in the form of extrusions, tubes, rod and so on, no less than about eight tons of light alloy sheet are used in the construction of each Empire-type boat b FLIGHT. AUGUST 5, 1937. THE KING'S ENVOY One of the first flying views of the specially prepared Airspeed Envoy (two Arm- strong Siddeley Cheetah Xs) which is maintained for the transport of Royalty and State personages. The top speed is over 200 m.p.h. It is obvious that one of the main con siderations in choos ing materials for such duty is resist ance to corrosion by marine atmospheres. The '' Alclad '' al loys manufactured by the Northern Aluminium Com pany, Ltd., were selected for the sheet and strip ap plications. These included the stressed-skin cover ing for all hull, wing and float surfaces with the exception of parts of the con trol surfaces, and rolled sections tor ribs, hull stringers and frames, etc. The characteristics and mechanical properties of these alloys may prove jf interest. In the first place, the high corrosion resistance is stated to be due to the composite natute of the sheet, consisting as it does of a strong alloy core coated with aluminium ot high purity, over 99.7 per cent. This coating exercises an electrolytic protection, as in the case of zinc on galvanised articles, and as the pure aluminium is electro negative to the core the latter is shielded from attack in the presence of electrolytes at the expense of the coating. As the latter, however, is high-purity metal which, as is will known, has superior natural resistance to corrosion, the loss is extremely small and the life of the sheet is greatly extended. From this property emerges a fact which is not generally appreciated, namely, that the protective influence, being electrolytic and not mechanical, has its effect on cut edges and alloy rivets, etc., which may be in contact with it. Another important advantage claimed for the "Alclad" alloys from a works point of view is its superior forming properties as compared with " straight" alloys. The coating, being in the soft state and having a definite diffusion zone at its junction with the core, provides a surface of graded elonga tion which greatly facilitates working. In the Short Empire boats two " Alclad " alloys were used, " Alciad " NA 17ST to specification L.38 and " Alclad " NA 24ST to -specification DTD.275, the mechanical properties as required by specification being as follows :— " Alclad " NA 17ST. " Alclad " NA 24ST. 0.1 per cent. Proof Stress tons/sq. in. 13.5 Ultimate Tensile Stress tons/sq in. 24 Elongation per cent, on 2in. 15 Major-Gen. Sir William. Boyce [FLIGHT regrets to record the death of Major-General Sir f William G. Bertram Boyce, K.C.M.G., C.B., D.S.O., who has been a member of the Rolls-Royce directorate since 1933' 16 26 15 ARTFUL DODGER The latest armour- decked bomb-target boat built by the British Power Boat Co. It can be con trolled by radio.
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