Promising Rubber Suspension System
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THE employment of rubber in vehicle suspension systems has oftdri been attempted in the -past, but not always with complete success, chiefly on account of the wide discrepancy between the elastic properties of rubber and the rigidity of the elements suspended. Rubber needs a certain amount of space for its expansion and contraction, but this cannot always be arranged, satisfactorily.
In the Neidhart system, now under commercial development in Switzerland by Rosta-Werk, Ernst Rohr (Hunzenschwil), the makers claim to have overcome disadvantages inherent in previous designs.
The principle employed in this arrangement, now known as the Rosta system, is simple. In the interior of a square-section steel tube a second square-section tube is Mounted at an allele of 45° in relation to the outer onc.% Elements of special rubber are arranged in the space between the two tubes, the rubber being introdIfe'ed under pressure. The container tube is attached to the chassis and the inner one, which can oscillate, is linked to the axle by an arm.
Road-wheel movements and shocks are taken up by torsion in the four rubber elements that fill the angles of the container tube. After a. second or third oscillation, movement is so slight as to have no effect at all upon the mass suspended.
Moreover, the heat generated by deforming the rubber constitutes an energy potential which, on release, is transformed into kinetic energy. The loss of heat resulting from this allows the rubber to provide a certain braking effect, so that the device combines the work of a shock-absorber with that of a main spring.
Demonstrations were given recently by the Rosta concern in their works at Hunzenschwil and a graph registered the difference between oscillations in normal steel spring suspension and those in the new rubber block one. Not only did these oscillations diminish far more rapidly when rubber was used, but overloading did not appear to have nearly so great an effect.
The system is certainly interesting. but its behaviour under really long service in heavy-duty vehicles remains yet to be seen