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Aviation History
1950
1950 - 1501.PDF
Jk. FLIGHT, 10 August 1950 '., 171 RESEARCH^ INTO RUBBER\ Aircraft-component Investigations at the New Technical and Scientific Headquarters of the Dunlop World Organization AS briefly reported in our issue of June 15th, the aeyrscientific establishment known by the title oi theDunlop Research Centre was formally opened on June 7th by Sir Lawrence Bragg, Cavendish Professor of Experimental Physics, Cambridge University. Plans for a central scientific organization were con- sidered by Dunlops before the war, but had necessarily to be deferred ; later, in the light of the company's war- time research and development experience, it became obvious that the original proposals required modification and extension. In general, the new Research Centre can be regarded as the fruit of this experience and planning. The original intention was to erect an entirely new group of buildings, but conditions at the end of the war made this impracticable, and it was fortunate that part of the shadow factory at Castle Bromwich became available. The administration building, power-house and an area of land were taken over; the administration building has been almost completely reconstructed to house the main labora- tories ; the power-hous.e building has been adapted, with considerable extension, to form a pilot plant building; and a new engineering services building has been erected. The total area of the Research Centre site amounts to nearly eight acres, of which about two acres are built on, so that there is considerable room for expansion. The extraordinary properties of rubber and rubber-like materials are associated with many branches of science, of which the most important are, perhaps, chemistry, physics, engineering and mathematics. As a consequence, the Dunlop Research Centre comprises a great variety of laboratories and a large number of scientific specialists, which make it probably unique in these respects among British commercial research organizations. On the occasion of the official opening ceremony we were able to make an exhaustive tour of the Research Centre, and most instructive it proved to be, particularly as regards those items which have a direct application to aeronautical practice. Some of the latest work.done in the field of adhesives and bonding technique has been concerned with the suc- cessful bonding of rubber, both to aluminium alloys and magnesium. Perspex is another material to which rubber has been bonded, and, furthermore, we were able to see a specimen section of laminated multi-ply sandwich, the alternate layers of which were rubber and wood. Rubber- metal bonding is also used in the couplings which Dunlop have developed for transmitting high mechanical power whilst both insulating the driving motor from shock and operating under considerable angular misalignment. The use of electrically conductive tyres on aircraft is not new, but the method whereby the property of con- duction is achieved may not be widely known. n brief, rubber can be rendered conductive (as can Bakelite and other resins and polymers) by the incorporation of forms of carbon-black which, owing to their crystal structure, tend to aggregate into chain-like groups. The degree of con- ductivity is considerable, being about a thousand times greater than that of tap-water. The actual properties are dependent both on the type of carbon-black and the type of polymer used, but do not significantly alter the normal wear resistance, extensibility, and other characteristics of the material. Mounted on floor rails, the cotd chamber can be moved intoposition beneath the pneumatically actuated tyre-impacting unit. In the larger sizes of aircraft the use of bogie under- caniagfes is now becoming fashionable, but such units do involve limitations in tractability. This was clearly illus- trated by an exhibit in one of the laboratories at the Research Centre. If the several wheels of each under- carriage leg freely rotate around a common axle, no prob- lems arise ; if, on the other hand, a tandem arrangement is adopted, it is equivalent to a bicycle or motor car with- out steering gear, i.e., the undercarriage exhibits a strong tendency to go straight ahead. In order to make a rolling tyre drift off its straight path, a force (known as the corner- ing force) -must be applied at right angles to the plane of the wheel. In addition, a couple or torque is required to maintain the original plane of rotation. Because of the disposition of the wheels in a tandem bogie undercarriage (and, too, because of the cornering properties of the tyres) there exists a related critical radius of turn, below which it is impossible to turn the aircraft without swivelling about the centre of one undercarriage and thus imposing a very high loading on the main leg. A double-walled soundproof acoustics laboratory is pro- vided for study of the allied qualities of noise and vibration. An electronic sound-level meter and sound analyser are used to assess the loudness and composition of the noise, whilst a vibration-meter and its analyser measure the acceleration, velocity, displacement and frequency com- ponents of the main vibrating parts. Waveforms, both of noise and vibration, can be examined on cathode-ray oscilloscopes, and can be compared for linking associated features, so that the origin of the disturbance may be traced. Vibrating parts on rotating members can be examined by a stroboscope, and instantaneous photographs of the relative positions of moving parts can be taken with the aid of a microflash unit coupled to the stroboscope. One of the devices evolved by Dunlop for the reduction of vibration in aircraft equipment is the Equiflexible mounting, the chief feature of which is that it will function at any angle. The mounting consists of three rubber elliptical springs, which, on the demonstration unit shown, were pyramidally arranged to support a metal weight of 1 lb; although the base of the mounting was severely
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