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Aviation History
1953
1953 - 0168.PDF
166 FLIGHT RESEARCH for INDUSTRY Varied Projects at Tiltman Langley's Redhill Laboratories IN spite of the present-day emphasis on large-scale research programmes measured in millions of pounds, there remains the need for research, investigation and development on a much smaller scale on particular problems. For the aviation industry, the private firm of Tiltman Langley, is one that performs such a function. Formed in 1947, after a three-year consultant partnership between A. Hesael Tiltman and Marcus Langley, both well known for many years in the aircraft industry, the organization provides design, testing and development facilities for Government- sponsored projects and for private ventures of both the firm itself and outside companies. A recent visit to Tiltman Langley's headquarters and labora tories at Redhill, Surrey, provided a glimpse of the varied work at present being carried out. As with almost any firm connected with the aircraft industry these days, much of what is being done cannot be described, for security reasons; even so, the remaining activities cover a wide field and are of much interest. Certain of the firm's work is connected with projects outside the aircraft industry, but the remainder, the major part, reflects directly the aeronautical background of the company's two founders. Of direct application to airline operation, the company's series of aircraft maintenance docks has been tailored to fit several types of aircraft. Those for the DC-3 and Ambassador were described in Flight of August 15th last. Mr. R. S. Carter, project engineer responsible for these docks, discussed further designs completed recently; these include those for the Viking, DC-4, Beverley and Britannia. At present, design work is proceeding on a proposed dock for use with Air France's Viscounts, which features, as do all docks in the firm's range, the "Keylock" system of structural assembly. This system was devised by Robert Building Inven tions, Ltd., of Newton Abbott—who perform the actual con struction and detail design of the docks—and was adopted by Tiltman Langley, who found it to give complete flexibility in design while preserving the chief advantages of prefabrication and interchangeability. The trend in the company's design of these maintenance docks is for the maximum simplification consistent with adequate servicing facilities. Present types thus favour a small number of movable rostrums wherever possible, rather than a more complicated fixed installation including office accommodation and the like. Wide Variety of Work From Mr. A. K. Clyde, assistant chief engineer, we heard first of the firm's approach to aircraft electrical systems. This favours the centralizing of subsidiary supplies, and the driving of alterna tors directly from the engine through a constant-speed drive, thus obviating the large number of invertors conventionally required to provide the subsidiary A.C. supplies, and effecting a consider able saving in weight. Recently produced and at present undergoing service trials is a portable cabin-air dryer, intended to prevent condensation inside a rapidly descending pressurized aircraft. The cylindrical con tainer (i2in diameter by nin high) houses a blower unit which draws air upwards and through a removable silica gel drying-cell, at the rate of 30 cu ft/min. Using 7 lb of silica gel, approximately half a pound of water can be absorbed before replacement of the drying cell, a colouring additive indicating when this procedure is necessary. Development is proceeding, also, on the applied use of the "gear type union" principle of coupling, to improve the poor accessibility so often prevalent in many accessories fitted to aircraft. This principle employs a ring nut with peripheral gear teeth, and a small pinion tool which meshes with these teeth. A high gear-ratio between pinion and nut is possible, and so considerable torque can be applied without the use of long spanners. Simple locking attachments can be provided. For pipe joints, this coupling is equally useful, enabling them to be tightened in normally inaccessible positions with very little twist on the pipes. From R.A.E., Farnborough, has come a development contract for an interesting vibrating table for test purposes, based on an original American idea, which features a mercury-filled rotor and a wide range of vibrating frequencies. For some time Tiltman Langley have been studying the problems of infinitely variable speed change in rotary trans mission, and of achieving this efficiently with high load-carrying capacity. In charge of this side of the firm's work is project engineer Mr. W. H. Mayall. Although hydraulic and electrical methods of speed variation have been considered, attention has been concentrated on mechanical friction types of transmission, for reasons of relative simplicity, low comparative weight, and general use in industrial applications. By testing commercial- type variable speed units, particularly the Hayes system, for the Ministry of Supply, Tiltman Langley have acquired practical experience of the problems to be solved in this connection. In addition, the transmission principle invented by Mr. J. J. Gerritsen (chief engineer of the company) is being actively developed, and designs based on this unit have been taken up by the Ministry of Supply and the Admiralty. The Gerritsen gear consists in principle of a number of hard steel balls rolling without slip between four coned hard steel surfaces. The balls are preloaded between the surfaces, in order to transmit power. By fixing two of the surfaces relative to each other, the rolling characteristics of the balls are determined. By choosing different surfaces, different types of rolling will be obtained, and consequently different types of gear ratios will be found. One particular possible application of this principle is extremely important. Although variable-speed gears are normally considered to provide variable output-speed from a fixed input, the problem of obtaining a fixed output-speed from a varying input cannot usually be solved without an external governor control. This problem is important in the generation of A.C. from an unavoid ably varying input, such as in A.C. generation from the main power plants of an aircraft. By using the centrifugal action of the revolving balls, the Gerritsen transmission can be designed to achieve immediate and automatic ratio adjustment on changes in input speed. The balls are thus acting not only as power trans mitters, but also as speed governors, and the response is immediate and without hunting. Concentric Flow-valve Another major application of the principle is in obtaining high reduction ratios, which problem is often encountered in small actuators, counters, servo mechanisms and light drives. Tiltman Langley believe that the Gerritsen gear can cover a broad field of applications for variable speed transmission in the lower power range, and further development work is continuing. On view in the firm's hangar at Redhill, also, was a specimen of the Tiltman Langley flow valve. The main feature of this valve is the concentric arrangement of the pipe connections, of the annular passage for the internal flow, of the main valve piston and of the pressure inlet jet facing the automatic flow. The only exception is the by-pass pipe, in which the control valve is situated. The annular passage around the main valve cylinder is maintained by webs or streamlined pillars between the cylinder and the outer casing. The cylinder has a spherical end at the inlet, through which a small central hole connects with the spherical-ended piston at the outlet. This piston chamber is by-passed by a small duct which re-enters at a low-pressure point situated near the main outlet. When this duct is closed, the piston is pushed to the closed position by the fluid entering at the pressure inlet jet, where the dynamic pressure due to flow velocity is added to the static pressure. When the by-pass is opened, therefore, the pressure in the piston chamber falls to such an extent that the static pressure on the front exposed area of the spherical end of the piston is able to push the piston back to the open position. Since the flow in the by-pass is very small, the main flow is virtually straight through the whole valve, and the pressure drop through the valve is, in fact, very little more than for a similar length of continuous pipe-line. The valve thus minimizes changes in fluid velocity and direction of flow, and also the space occupied around the pipe, and so gives low resistance with high velocities of flow and compact installa tions without elbow joints. The absence of glands makes it suitable for corrosive and inflammable fluids, and control is directly effected by manual, pneumatic, hydraulic or electric means. It can be designed for use at high or low temperatures and pressures. An important branch of the Tiltman Langley organization is the metallurgical section, headed by Dr. R. Hargreaves. Among the problems studied here are those connected with metal-joining methods other than riveting—such as glueing, welding, brazing and soldering. Soldering methods for aircraft construction are being investigated, and also the cold pressure-welding process as
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