Challenge to Hydraulic Dampers
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D UBBER is employed as the damping
medium in a shock absorber developed by the staff of the Rubber and Plastics Research Association. Examples of vehicle-suspension dampers based on this new principle were shown at the International Engineering Exhibition on Tuesday by the Department of Scientific and Industrial Research.
Operation of the damper is based on a variation of the principle that energy is lost when rubber is deformed. The R.A.P.R.A. system utilizes the energy which would otherwise be lost when a flat rubber pad is indented, doing this by means of metal rollers which roll under compression over the rubber. When designed as a telescopic damper, an inner metal plate has rubber pads bonded to its top and bottom faces and slides inside an outer metal casing which has rubber on its inner surfaces. Between the two sets of pads, metal rollers, in frames but free to rotate, are interposed. As the inner member moves relative to the casing the indentation of the pads by the rollers uses up energy. In addition to the telescopic device, a rotary, lever-type damper has been produced.
There are a number of inherent advantages of the R.A.P.R.A. dampers over conventional hydraulic units including no sealing, longer life, better performance under shock loads and simplicity of design. Tests carried out on cars are said to have shown that even at the prototype stage the damper compares favourably with a conventional hydraulic shock absorber. Five British rubber manufacturers have been granted licences under the R.A.P.R.A. patents. Four are Redfern's Rubber Works Ltd., Peradin Rubber Co. Ltd., Avon India Rubber Co. Ltd., and Rubber Bonders Ltd., the fifth does not wish its name to be published.