CONTROLLING SUSPENSION

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CONTROLLING SUSPENSION

THE laminated spring, which is still the standard method of suspension on most motor vehicles, has a number of advantages, but is incapable of dealing satisfactorily with all the demands made on it. For ideal suspension one would need a supple spring at low speeds, and a stiff one at high speeds more especially on sports cars where fast cornering is indulged in. The physical properties, that is, the size and thickness of the leaves and the amount of friction between them determine whether the spring is flexible or stiff, so that the springs only provide for one set of conditions, and it was not until the invention of the “shock-absorber,” which is of course simply a device for adding any desired amount of damping to that inherent in the spring, that the modern era of comfortable riding began. Even when shock absorbers are available one finds it necessary to tighten them up for fast running

to an extent which makes for harshness at low speeds. The perfection of the Andre Telec.ontrol system, which allows the shock-absorbers to be adjusted to conditions when the car is actually in motion makes it possible to have perfect comfort at all speeds. An early form of Telecontrol utilised a modification of the Hartford friction disc shock absorber, a lever on a quickthread forcing the elements into Close contact, but some trouble was

experienced with stretching cables and carelessly fitted outer casings.

The Hydro-Telecontrol, as the new type is called, is free from these disadvantages. . The mechanism of the Telecontrol is similar to that of an. internal expanding brake, one arm carrying the drum. and the other two shoes faced with friction material which are

forced against the drum by an expanding rubber bag, which in turn is expanded by fluid pressure from the control cylinders. These cylinders are mounted on the dash or the steering column. Turning the hand-wheel screws down a piston inside the cylinder, forcing

liquid along copper pipes to the shock absorbers. A pressure guag e shows what pressure is being exerted. One cylinder can operate all four shock absorbers, but on a sports car where front and rear shock absorbers may need different pressures, two controls are usually fitted. One great advantage of hydraulic control is that the pressure exerted on all the shock absorbers operated by the same control is equalised. For test purposes a set of Tele controls were fitted to a four-seater ” 90 ” Talbot. This car had for merly been fitted with a set of normal Hartfords, and after considerable experiment it had been found possi

ble to get a setting where the front pair could be left at a constant setting, the rear pair needing an extra turn for really hard driving. We did not expect to find a great deal of benefit from the Telecontrols therefore and were surprised by the result of the test. For London with the controls reading at 0-25 lbs. suspension was as good as in any touring saloon, while an increase to 50 lbs. all round sufficed for normal touring purposes. With the ready adjustment available, one is not’ tempted to keep the suspension hard, which must save such articles as headlamps and mudguards a good deal of un necessary vibration when travelling fairly slowly over rough ground. 100-120 lbs. was sufficient to make the car completely stable on any

corner, so that with the maximum pressure of 200 lbs. the Telecontrols should be capable of stabilising any car. We were rather sur prised to find that the front shock absorbers required little more pressure, perhaps 25 lbs. more than tne rear ones, at full speed. This can be attributed to the good weight-distribution of the Talbot, for on some cars experimented on, the front shock absorbers had to be tighte,ned up almost solid before one could overcome that sickening ” diggingin ” feeling at high speeds. Hydro-Telecontrol shock absorbers cost either £6 or £7 10s. per pair, depending on the size of the car. This price includes dash control, indicator and the necessary connections and pipes. The maker’s

address is T. B. Andre & Co., Victoria Gardens, Notting Hill Gate, London, W.11 .