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Aviation History
1938
1938 - 1676.PDF
534 FLIGHT. JUNE 9, 1938. driven models on German and Swedish lines are slowly gain- ing favour, but •flying scale and petro models, and ultra-light- weights are almost unknown. Coming Events June 12: Western Cup contest for Wakefield types, at Fairey's Great West Aerodrome. June 19, from 11 a.m. until dusk: "Northern Heights" Gala Meeting (programme giving details of popular contests obtainable for 4d. post paid from Mr. C. A. Rippon, 58, Hampden Way, Southgate, London, N.14),-and S.M.A.E. contest for Women's Trophy presented by Mrs. A. P. Thurston, both at Fairey's. June 26: S.M.A.E. seaplane contest for Lady Shelley Cup, S.M.A.E flying-boat contest for White Cup, and N. Kent Model Airl craft Society's open flying-boat contest for Roberts Trophy all at Danson Park, Welling. ' July 3: the team "of 6 to represent Great Britain in the Wakefield contest will be chosen in eliminating trials at Fairey's. . " • * • ." " 4: In their latest Premier Guide, Premier Aeromqdel Supplies,. 2a, Hornsey Rise, London, N.19, combine a price list witfc much sound advice on model construction. Several new designs are ofiered in the form of blue-prints and kits qf materials. •-"' FOR SPEEDY SHEET-CUTTING Details of the Desoutter nibbler DIRECTIONOF CUTTING PLAN >#= ="-*.-. .VIEW OF ' / iV^.PUNCH AN unusually interesting production tool is announced.Desoutter Bros., Ltd., The Hyde, Hendon, are in pro- duction with a portable pneumatic nibbler that weighs 2 lb. only, and will cut up to 18-gauge duralumin and 20-gauge steel at 10ft. per minute. In the past, it is claimed, the only nibbling machines available have been large power-driven tools taking up a lot of floor space and usable only when the work could be taken to the tool. , This tool—which looks so simple yet has taken twelve months' hard work to perfect—was actually developed for ser- vice and repair work in the field of metal-skinned aircraft. Because of its extremely compact design it can start cutting anywhere in a sheet of any size or shape by introducing the head through a iin. hole. Thus it could be used to cut out a damaged section of a leading edge in position, to cut holes for a petrol-tank filler, or to cut out inspection holes. > . The secret of the Desoutter nibbler is the design of ihe-i punch and the neck-frame joining the die-holder to the body." of the tool. Patents have been applied for to cover these points. The punch is crescent-shaped, and takes 20 cuts to the inch. It is reciprocated by a vane-type pneumatic motor. Both punch and die are easily and cheaply replaceable. Because this tool cuts by nibbling out a slot in the sheet, in which the neck-frame of the tool runs, the metal does not have to be parted (as in a shear), and so the nibbler cuts without any deformation of the sheet. Owing to the shape of the punch the "nibbles" overlap and thus produce an exceptionally smooth finish, without any burrs. - I The nibbler can be used freehand, or to cut inside or out- side a template,. The minimum radius of cut is lin! It' can also be used with a simple and ingenious radius-arm attach- ment for cutting a truly circular hole from • a centre. A iin. hole is drilled at the centre of the circle, aad« a iin. hole anywhere between the centre and the circumfer- ence. The sliding pin on the radius arm goes into the Jin. hole, and the head of the nibbler into the iin. hole. The tool is started, and is made to cut outwards until the stop comes "up against the sliding pin; thereafter the tool "walks" round the circumference of the circle. To hold the centre portion steady when the cut is nearly completed two little clamps are used across the nibbled slot. . • — •>.: CORD-BAKELITE AIRSCREW BLADES THE development of solid and hollow airscrew. blades ofsynthetic resin has been proceeding at the De Havilland airscrew factory at Edgware since 1936. Solid blades have been machined from the block, one of the more successful materials employed being Bakelite reinforced with special fabric. Interesting comparative experiments are also being carried out with woods compressed and impregnated with phenolic resin. More recently, hollow blades have been moulded in Bakelite reinforced with cord. Sectionised examples were exhibited at the R.Ae.S. Wilbur Wright lecture (the concluding section of which is reported on. pages 568e-568g of this issue). An important feature is that the cords lie longitudinally, simulating very closely the grain flow in duralumin blades, particularly at the root flange where the blade is held against centrifugal load. The material employed has a tensile strength of about 35,000 lb /sq. in. and a shear strength in the direction of the cords of about 6,000 Ib./sq. in., while a shear strength approxi- mately four times this value is obtained transversely to the cords such as across the root flange. High resistance to fatigue and high internal damping characteristics — noteworthy advantages for airscrew construction—are claimed. Rela- tively low weight is another advantage; . the specific gravity is approximately one half that of duralumin. The Young's modulus figure is approximately 3.5x10* lb./sq. in. At the present time the De Havilland .Co. is developing a. 5,000-size airscrew with corded Bakelite "blades which is to be delivered to" the Air Ministry for tests. In this project Bakelite, Ltd. (who, of conrse, are pioneers in plastics), are co-operating.
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