From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Article detailing a new system where hydraulic shock absorber settings are varied by vehicle speed and manual control.
| Identifier | ExFiles\Box 87\3\ scan0139 | |
| Date | 19th February 1935 | |
| NEW SYSTEM IN WHICH THE SETTING OF HYDRAULIC SHOCK ABSORBERS IS VARIED BY SPEED & MANUAL CONTROL The new Bentley steering column, showing the small lever at the bottom by means of which the driver can regulate the damping effect of the four hydraulic shock absorbers between wide limits. A ROAD-SPRING damping system, the action of which is automatically variable in respect of speed but can also be controlled by the driver, is now standardized on the 3½-litre Bentley chassis. It comprises four hydraulic shock absorbers with a novel oil-pressure control, and the general design is the same as in the system employed in the 20-25 h.p. and 40-50 h.p. Rolls-Royce models. This important addition to Bentley equipment is made without any increase in prices. In the course of a road trial extending over 100 miles we gave the new suspension a thorough test on road surfaces of all types and at speeds extending up to a maximum of 90 m.p.h. The driver's control, as shown in a photograph reproduced, takes the form of a small lever just above the steering wheel, which can readily be moved between limits marked "minimum" and "maximum". With the lever in the minimum position the damping action is reduced to a setting which is admirably suited to moderate speeds on rough roads. For example, the deplorable surface of the road between Woking and Staines (via Chertsey) was covered at 40-45 m.p.h. with the minimum setting in use; there was an entire absence of vibration or judder, the car riding easily and comfortably throughout. As an experiment, we ran up to a very high speed while leaving the control in the position which gives a minimum of damping. This test brought out a very important feature of the new system, namely, an automatic increase in the damping as the speed rises, which occurs irrespective of the location of the hand control. Consequently, the car does not tend to become unstable if a lazy driver forgets to regulate the system. On the other hand, the control enables a more powerful check upon spring action to be obtained throughout the speed range, so providing an enhanced steadying effect for fast cornering or for high speeds on a rippled main road. One can, perhaps, best describe the device as an over-riding control which enables the driver to emphasize the automatic increase of damping with speeds in accordance with road conditions or personal inclinations. An outstanding feature of the system is the rapidity with which it responds to the control. In consequence, a change in damping can be effected as speedily as alterations in road surface are encountered on a fast car. The Bentley steering gear is delightfully sensitive and is fairly high geared, so enabling the car to be handled with speed and precision. Naturally, these characteristics imply a directness and lack of friction which result in a slight tendency to wheel kick at speed. Here, again, the new control is of value, as an increase in damping reduces front-axle movements and so steadies the steering effectively for fast cruising. Detailed drawings of the patent cannot be disclosed, but the principle employed may be explained as follows:-An oil pump, driven from a shaft in the gearbox, creates hydraulic pressure. By means of piping, this pressure is applied to diaphragms which are used to load the by-pass valves of the shock absorbers. Consequently, as the speed of the car increases the pressure rises and the damping effect of the shock absorbers is augmented. The driver's control is coupled to a by-pass on the oil-pump circuit, so altering the hydraulic loading throughout the speed range. Thus, although the damping effect still increases with the road speed, it can be either reduced or increased throughout the range by means of the small lever on the steering column. The shock absorbers are connected to the front axle by stiff triangulated links, so also serving as radius arms. "The Motor" Feb. 19, 1935 | ||