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Aviation History
1932
1932 - 1094.PDF
FLIGHT, OCTOBER 27, 1932 Fig. 1, WELDING TOOL IN USE : The method of connection to the welder is shown, and the general compactness will be noted. Shot Welding IN modern aircraft practice, riveting is the pre dominant method of fabricating metal assemblies— at any rate so far as the British industry is con cerned. Most of the steels used to-day are readily weldable, so that the reason for the preference for riveting is less valid than it was some years ago. Probably this is because, hitherto, the designer has felt able to place greater reliance on riveted than on welded structures. Ordinary welding, though it can give joints of great strength when ideal conditions obtain, is more or less a matter of craftsmanship, and there is no ready, non destructive means of determining whether any individual weld is a good one. On the other hand, riveting is, for Fig. 2, HAND WELDING TONGS : The appearance of the shot welds can be seen. 1014 all practical purposes, perfectly reliable ; though it js naturally impossible to indicate the exact condition of every rivet in a long run, ordinary testing methods can ensure results in which complete confidence can be placed. Another objection sometimes urged against welding is that prolonged heating of any kind is often undesirable in fabrication, the more so with alloy steels of the kind used in aircraft construction. Thus, in the interests of safety and caution, present-day practice tends almost entirely to the use of the riveted joint. Yet welding has much to recommend it. It demands no punching or drilling of plates—processes that, relatively expensive, induce in certain circumstances local weakness ; that being so, a welding process that overcame the existing objections slfould go far to simplify manufacturing problems. The ideal of controlled welding seems to have been realised in the shot-welding process, demonstra tions of which have recently been given to the industry in this country by the Pressed Steel Company of Great Britain, Ltd., of Cowley. It introduces many features new to welding techni que, and its possible influence on fabrication practice may well be great. Briefly, shot welding is a form of electric-resistance welding in which the time of current applica tion has been reduced to (he shortest possible for causing com plete fusion of the metal ; and these short welds are not merely automatically ensured, but are supervised by an automatic weld- recorder that maintains a con tinuous watch on the conditions of welding. Good welding is determined by three main factors: proper pres sure on the electrodes, proper voltage-current relations, and proper time of current applica tion. In the shot-welding
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