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Aviation History
1937
1937 - 1298.PDF
.488 FLIGHT. MAY 13, 1937, eoToa. SOMETHING NEW IN HYDRAULICS SHOWN as a working demonstration model at last Sunday's R.Ae.S. Garden Party was an interesting item of equipment that is among the aero accessories which Tecalemit, Ltd., will shortly be turning out from their ad ditional factory premises. It is a hydraulic pump intended primarily for the operation of gun turrets, retractable under carriages and other gear, and is equally well suited for use as a hydraulic motor at the " dis tant " end of the transmission line. It will also function perfectly well as a pneumatic system, when it is particularly useful for portable tool operation. The pump is claimed to combine very high pressures and a large delivery with exceptionally high volumetric efficiency, and, except for the bearings, no parts are in frictional contact. An '' area seal " of a substantial size makes it possible to secure high pressures while retaining a definite clearance between moving surfaces. As with a great many inventions that are delightfully simple in action, ease of description goes in inverse ratio. However, from the drawing it will be seen that the driving shaft carries a rotor, in recesses of which are pivotally mounted blades. These blades are kept in one plane during movement of the rotor by a train of lightly loaded gears. Machined in the face of the rotor is an annular groove which forms the working chamber of the pump. The recesses for the blades are machined into the outer periphery of the rotor, thus providing the '' area seal'' between rotor and blades as opposed to the line-contact seal provided by most blade pumps. In the rotor groove, but fixed in relation to the pump body, is a fixed abutment, which is at all times sealed by the rotor and isolates the inlet and outlet ports. The blades are so shaped that as they revolve they are completely withdrawn into the rotor when they are passing the abutment. ABUTMENT End and side elevations of the new Tecalemit pump. Fluid is induced from the inlet port (assuming clockwise rota tion) by the downward movement of blade A until blade B makes seal with the outer ring of the groove, when the latter blade takes up the suction. At this point fluid will be trapped between blades A and B until blade A breaks seal, when the fluid is ejected by blade B at the outlet port. When the pump is full the action is continuous, without the slightest pulsation at any speed or pressure. The rotor carries blades on each side so that end loads are eliminated. Further, the loads on the blade delivering under pressure are also equally divided on either side of the axis of the blades. In the form illustrated the pump is capable of delivering oil at over 8 galls, /min. at half normal engine speeds, and at a pressure in excess of 1,000 lb./sq. in. if required. An interesting development of this mechanism is a four- bladed pump with two fixed abutments; it has two independent inlet and outlet connections for operating two separate installa tions such as twin gun turrets, or one turret and undercarriage. The size is approximately the same as for the single-outlet pump. Further details are obtainable from Tecalemit, Ltd., Great West Road, Brentford, Middlesex. Neoprene—a Material with Possibilities A SHORT time ago a new and interesting synthetic com pound with rubber-like properties was introduced by the I.C.I., Ltd., and although many months of development have already passed, the product, Neoprene, is still in its infancy so far as its possible applications are concerned. The preparation is not complicated, and, for the benefit of the analytically minded, may be said to depend upon the polymerisation of acetylene produced from calcium carbide and water followed by treat ment of the vinyl acetylene so formed with hydrochloric acid and further polymerisation. At a recent exhibition of the possibilities of Neoprene some characteristics were impressively demonstrated experimentally. Pairs of discs, one of rubber and one of Neoprene, had been suspended in various liquids, including water, petrols and oils, while graduated glass tubes with rubber and Neoprene con nections contained the same liquids. In each case the unusual resistance of Neoprene to these mediums was clearly visible by reason of its having remained practically unaltered beside its swelled and distorted rubber counterpart. Sample gloves, boots, hoses, cable coverings, buckets, jointing and gasket materia], tyres and coloured products were also shown. The compound is not intended to compete with natural rub ber (at the moment it costs nearly three times as much), but it is claimed, apparently with justification, that in the event of a shortage of raw materials it could be substituted with equal, or greater, success. Neoprene cannot be vulcanised to hard rubber, but forms an interesting flexible ebonite by admixture with natural rubber. It is claimed that resistance to oils, heat, gas permeability, ozone, ageing, flex cracking, water absorption and shock and vibration is better than that of rubber. It is further claimed that Neoprene is more easily milled, extruded or calendered. There are many applications of the compound both to aero plane and engine. Longer life could be expected from washers, glands, ignition screening and suspension blocks made from it, and flame-resisting tyres, cabin fittings, piping and cable covering are possibilities. Very favourable properties are also offered for use in the pulsing leading-edge type de-icer. Various publications on the subject of Neoprene, its produc tion and application, and information on the facilities for rub ber research offered in the laboratories can be obtained from I.C.I., Ltd., Thames House, Millbank, London, S.W.i. Some aircraft small parts in Neoprene. Novel Memento AT the stone-laying ceremony at the new offices of Hepworth and Grandage, Ltd., the Bradford piston and ring special ists, a customer of thirty years ago, Mr. George Burrow, presented Mr. George Hepworth (joint managing director) with a gudgeon-pin that formed part of his first order. The firm's history during that thirty years was described by the chair man, Mr. G. R. Hall Caine, C.B.E., M.P.
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