Modern Motoring

Northern Advocate, 18 March 1939, Page 6 (Supplement)

Modern Motoring

New Suspension System

Some time ago there was described in. these columns a motor-car suspension system by inflated rubber bags, which had been developed by a prominent American tyre manufacturer. At the time, it was mentioned that engineers throughout the world are paying far more attention to springing than to any other part of the car, and that the arrangement described was entirely in accord with the present trend, which is to get away from leaf springs, if possible. Details of another new springing system which also uses rubber, although not in the shape of inflated bags, have been received from England. This has been designed for independent springing front and rear, and is exceedingly simple in its details. How it will behave in practice remains to be seen. Each wheel is carried by a longitudinal radius arm attached to the chassis on a fulcrum point a short distance from one end, while the other extremity is: attached to the wheel hub. Surrounding the fulcrum is a large disc of rubber compressed to give a frictional) grip between two metal discs with lips turned in, one disc being attached to the radius arm and the other the the chassis frame. The whole assembly is held together by a lateral bolt, whose nut can be turned down or slackened in order to vary the grip of the rubber between the discs. As the road wheel moves up and down, the radius arm creates a torsional resistance in the rubber disc.

Additional Aid The whole task of providing a soft spring action, however, is not left to the rubber disc in torsion, but rubber in compression is used as well. At some other point on the radium arm, either in front of the fulcrum or behind it, is placed a cylindrical rubber pad contained in telescopic metal sheaths. As the road wheel moves upward, this rubber pad is compressed. Because the pad is anchored to both the radius arm and the chassis frame,

movement of the road wheel downward places it in tension. The metal sheathing surrounding this pad is so arranged that compression of the rubber up to a certain point is unrestricted, hut beyond that point the rubber pad expands sufficiently to fill the diameter of the sheathing so that further compression is impossible. This pad, therefore, tends to act as a check cn excessive spring movement in just the same manner as the ordinary hydraulic shock absorber applied to leaf springs.

In support of the idea of using rubber in this fashion for suspension can be cited the manner in which rubber is largely used in cars for absorbing shocks and vibration in other directions —in flexible engine supports, for instance. Pros and Cons The new scheme has some favourable features of which the absence of noise and the elimination of oiling points, save possibly one on each of the fulcrums, are obvious. On the other hand, some trouble may be experienced in using longitudinal radium arms as the twisting forces imposed on them by the tendency of a car to roll on corners are great. Radium arms used in this fashion on other springing systems have not proved too successful for this reason. Nevertheless, the invention is an interesting one, showing the tendency of the present day.. Rubber, properly applied, should be a splendid medium for springing, because it can be manufactured in almost any degree of “sponginess,” and thus the designer has at his hand a far wider latitude in the control of his springing medium than he has with leaf springs. Furthermore, there are processes in the vulcanising of rubber now known which render it practically impervious to outside deteriorating influences such as weather. .

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