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Aviation History
1938
1938 - 2404.PDF
h FLIGHT AUGUST 25, 1938. INCREASING AIRSCREW PRODUCTION The Hordern-Richmond Factory : A New Type of Finish : Design Considerations FOR some reason or other no great interest is ever taken, at least by those outside design offices, in the normal type of airscrew. To the ordinary person it is either '' right " or " wrong.'' Because it must be properly understood for successful operation, the variable- pitch type of airscrew is taken a little more seriously. Nevertheless, the normal wooden fixed-pitch airscrew is likely to be used for a very long time to come, at least in the smaller civil classes, and, in any case, there is always likely to be a considerable demand for detachable wooden blades which can be used with v.p. hubs. In previous years one company has been able to deal with practically all this kind of work, but now it seems that the Air Ministry and individual manufacturers may find good use for the products of other airscrew factories. Quite recently—actually in January of this year—Hordern- Richmond Aircraft opened a new factory at Chesham. The nucleus here can be considered as being the erstwhile Lang Propellers, a company which had its works at Peterborough, and Mr. A. A. D. Lang is on the board of directors. Mr. Lang, incidentally, has been in the airscrew business since 1913. As designer, Hordern-Richmond Aircraft have the ser vices of Mr. Tony Fletcher, who, though previously and primarily concerned with aircraft as a whole, has always been particularly interested in the design of airscrews. Mr. Fletcher's basic, and so far very satisfactory, idea is to design airscrews for maximum efficiency at a machine's cruising rather than maximum speed. It has been found in practice that by using this speed as, so to speak, the datum point, a considerable improvement can be obtained in the take-off, climb, and cruising performance, while the loss of speed at full throttle in level flights forms such a small per centage that it is of little importance except for racing pur poses. Several civil machines have been fitted recently with H-R designs, and the results have certainly proved Mr. Fletcher's contentions. Among these have been the Tipsy two-seater, the Miles Monarch, and, of course, the Hordern- Richmond Autoplane. The most interesting part of the equipment at the Chesham FOR some considerable time Luton Aircraft have been at work on the development of a two-seater machine which will be known as the Luton Major and may be considered in a general way as being a development of the Minor. The pro totype machine is now very nearly finished and will presently be ready for its first test flights. Some slight stress is laid on the period during which the Major has been in process of de velopment because the makers want it to be understood that 2he machine has not been hurriedly designed simply to meet C.A.G. requirements. However, in the new circumstances, arrangements are now being made for quantity manufacture at Gerrard's Cross. The Major is a high-wing tandem-seater cabin mono plane, this arrangement having been chosen to provide stability and good general flying qualities as well as a good field of view from the pilot's seat. A normal range of instru ments, following Air Ministry requirements, is arranged in a detachable shock-insulated panel. The wings are foldable by a simple system is which there are no flapped parts to deal with, and no controls to discon nect—each wing being released by the removal of a single pin, and is automatically self-locking in the folded position. Al though the machine is to be produced in cabin form, the top part of the sides may be removed or partially opened for fine- weather flying. Full normal dual is provided and fore and aft trimming is done by means of a tab on the elevator. The split-axle type of undercarriage may, as an alternative, be replaced by some form of tricycle gear. The wheels are fitted with brakes, which are differentially operated from the rudder bar for manoeuvring on the ground. For the moment at least, the production Majors will be fitted with Walter Mikron engines, but alternative British units are at present being developed, and the machine has been designed to take any engine of similar power. Ease of construction and, consequently, of maintenance, has been chiefly considered in the design of the airframe, which is built up mainly of spruce and plywood with the engine mount ing, undercarriage, lift struts and main stress-carrying mem bers in the fuselage of steel tube. factory is that for manufacturing airscrews with the new resin finish developed by the B.T.H. company. This finish has been accepted by the Air Ministry as an alternative to the better-known Schwartz finish, and Hordern-Richmond Aircraft are expecting some useful orders. The equipment for pro ducing this tough, non-brittle finish is fairly expensive, since it involves the use of a press. The finish, as such, appears before application as a resin- soaked stocking designed to fit each particular blade. The blade is first dipped in resin, the stocking is slid on and covered with a rubber sheath, and the blade is then surrounded by fine shot in the press and left there for twenty minutes at a temperature of 8o° F. or so. When the airscrew is taken out the fabric of the stocking is, with the resin, part and parcel of the blade, and the surface is then smoothed down before an additional area pi resin is applied to the leading edge. Manufacturing Methods For the airscrews the company uses birch, which, after tests at Farnborough, is now considered as a suitable and much more easily obtainable substitute for mahogany and walnut. The airscrews are built up in the usual way from a number of shaped sections which are glued together, the whole being roughly shaped and then left for twenty-four hours so that any warping may take place before being finished. Needless to say, the secret of airscrew manufacture, apart from the original design work involved, lies in accuracy of workmanship, and, judging by the results, it appears that Hordern-Richmond Aircraft have succeeded in collecting a very good group of craftsmen. A not usually appreciated point of interest in airscrew manu facture is that concerned with the seasoning of the original planks. When these arrive at the factory they usually have a water-content of 16 per cent., and they are then stored for a period of days in a specially ventilated room until this con tent has been reduced to about 12 per cent. For Air Ministry orders this period must be 28 days, but one of 10 days is adequate for normal purposes. Before use samples from each plank are tested for water-content and for strength. There after, considerable care is necessary to make sure that the grain is correct for each section used. The preliminary specification and performance figures are :— All-up weight, 1,030 lb.; weight empty, 600 lb.; maximum speed, 100 m.p.h.; cruising speed, 85 m.p.h.; stalling speed, 30 m.p.h.; and cruising range, 320 miles. The provisional price, in fully equipped form, is £525. ANOTHER C.A.G. RECRUIT
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