VIBRATION.

Auckland Star, Volume LXIV, Issue 25, 31 January 1933, Page 14

VIBRATION.

ENEMY BEING OVERCOME. fr INCREASED USE OF RUBBER. Vibration, one of the greatest enemies of the car designer, is being slowly but surely conquered. Vibration is capable of breaking the staunchest components of both chassis and body. The effects of vibration are as varied as they are elusive. The gradual shaking loose of a nut may have hundreds of serious consequences. Fatigue will wear down the resistance of strong castings. And there are numberless other points in combating the evil which have to be considered by the creators of the modern car. They have succeeded to a remarkable degree. Road shocks and engine vibration are the two primary enemies. Let us analyse the latter first. The internal combustion engine, in principle, Is an atrocity from the standpoint of perfect engineering. Instead of a steady flow of power, which is the ideal —and is exemplified, for instance, in the turbine —it gives a series of explosive jolts to the pistons at the rate of thousands per minute. Despite the vast improvements which have been made in the smooth running of the petrol engine, it is still the worst offender as a source of vibration. Perfect balance is impossible, but the counter-balancing and stiffening „of as many moving parts as possible has cut down this to a large extent. Absorption by Rubber. Realising the impossibility of eliminating the vibration, engineers have turned their attention in another direction, and are aiming at its absorption; and in this rubber is being used to an ever-increasing degree. The bearers holding the engine in the frame are now insulated with rubber blocks in practically all new models, while others are mounted on springs, to take up the vibration that would otherwise be transferred to the frame and body-work. Another ingenious new development is that of suspending the engine unit at two points only—under the gear-box and high up in front of the cylinder block. this system the engine is free to move in relation to the frame, although the movement is confined to a small space by a leaf spring connected with the frame. Flexible Connections. When the engine is started it can be seen shaking under the stress of th<> moving parts. The use of flexible petrol pipes and allowance for the slight movement in other controls and connections is, of course, necessary, but it is worth while. A four thus fitted, a writer in an exchange claims, gives the same vibrationless running as a six or eight cylinder engine.

1 The basic cause of road shocks, the other main source of vibration, is obviously the road, but confining ourselves to the methods of minimising vibration on the car itself, we have the tyres and springs. Larger section lowpressure tyres have made a big improvement in recent years, and so has suspension generally. Softer Springs. In springs a compromise has to be effected between flexibility and stability. If springs are too hard the and the car suffer accordingly, but if they are too soft the vehicle sways dangerously on corners and will not hold the road at speed, owing to continued bouncing after hitting a bump or spoondrain. The universal adoption of shock absorbers has enabled the use of softer springs, as. it damps out the rebounds, but a sacrifice still has to be made for the sake of roadholding. This means a shaking for tho body, which often results in loosened joints, squeaks, rattling windows, ill-fitting doors, cracked pannelling, and other common ailments. Rubber again comes to tho rescue in the shape of buffer washers between the body and the chassis and between various parts of the body, minimising, if not eliminating, these ailments.