NEW SUSPENSION SYSTEM

Press, Volume LXXV, Issue 22656, 10 March 1939, Page 16

NEW SUSPENSION SYSTEM

USE OF RUBBER FOR SPRINGING DETAILS OF ENGLISH INVENTION Some time ago there was described in these columns a motor-car suspensory system by inflated rubber bags, which has 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 to the chassis frame. The whole assembly is held together by a lateral bolt, whose nut can oe 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 radius 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, but 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 on excessive spring movement in just the same manner as the ordinary hydraulic shock absorber applied to leat springs. . , , u ■ 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 radius arms as the twisting forces imposed on them by the tendency of a car to roll on corners are great. Radius 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.

PLASTIC CAR BODIES

GERMAN DEVELOPMENT A noticeable feature of modern cars is the increasingly wide use being made of' plastic materials for the interior decoration of the coachwork. Typical of this tendency is the plastic instrument board which is to be seen in so many of the 1939 types. But in Europe, manufacturers are proposing to carry the use of plastics even further, and to build complete motor-car bodies of this material. The Auto-Union Company in Germany, for instance, nas taken out a number of patents covering a special method of doing this which are most interesting. The process consists of building a double-walled body ot plastics. The various components are manufactured separately and then assembled in a special jig, with applications of adhesive at the joints. All fittings and any necessary reinforcing pieces are then put into position, and the final step is to place the inner walls within the jig. The assembly is then ready for literally “cooking’" into one piece, and this is achieved by placing inside the body an inflatable bag or balloon. Steam or hot air is admitted to this bag through a suitable connexion, which then expands, and presses the members of the body assembly outwards against the jig. The outside portions of the jig have hollow passages into which the steam or hot air also is admitted, so that heat is applied to the assembly both from within and from without. At the completion of this “cooking,” the jig is dismantled, the balloon deflated and removed, and the body stands complete in one unit. While it is generally admitted that quite a strong and light motor-car body can be constructed in this way, the objection has been advanced that repairs in the event of an accident would be rather difficult, and that until some method is devised of successfully replacing- broken panels, the- plastic body must remain a theoretic possibility on designers’ drawing boards.

According to data collected by the National Safety Council of United States of America, the severity of motor accidents in that country, with its 29,500,000 automobiles, ascends with the rate of travel, in the following ratios. At speeds less than 20 miles an hour only one injury in 70 is fatal, at from 20 to 29 miles an hour, one injure accident in 45 is fatal, at from 30 to 39 miles an hour one in 37, at from 40 to 49 miles an hour one in 30, and at speeds exceeding 50 miles an hour one injury in every II accidents is fatal.