Dunlop Air Springing System
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DETAILS of the Dunlop Pneuride pneumatic suspension system were released on Wednesday. The major advantage of employing air as a suspension medium is that the spring stiffness or rate can be controlled, increasing with deflection rather than remaining constant, as in other more
conventional forms of springing. In the Dunlop system, full benefit has been taken of this characteristic, to provide a low-rate spring for small movement, whilst allowing a higher rate for larger deflections, thus avoiding the build-up of resonant oscillations in the system.
Flexible air 'springs of con volutedbellows formation are used in the place of the normal springs, with a levelling valve to each spring which automatically compensates for variation in vehicle loading. Conventional dampers are retained,
Each air spring is made of rubber and nylon cord using methods proved in tyre manufacture, whereas the levelling valve has been evolved specifically to meet the requirements of the pneumatic suspension. Maximum working inflation pressure of the air springs is normally 100 p.s.i., but in practice pressures above 80 psi. are rarely required and readily provided by the vehicle compressor. With lighter vehicles a replenishable container may be used. The air supply necessary is in fact small as, by reason of a delay device, air is admitted only when the loading is increased.
Not only does the Pneuride suspension offer increased efficiency, but also a reduction in maintenance and replacement costs. When it is combined with rubber-bushed radius arms locating the axles, lubrication is entirely eliminated. Furthermore, as the system provides a consistently soft and controlled suspension, additional loads on the tyres are minimized.
Applied to heavy commercial vehicles, the possibilities of the new suspension will be readily apparent because of the wide variation in load to which such vehicles are subject. The constant ride and controlled height characteristics of the system under all conditions of loading should also be of advantage in light vehicle construction.