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).
The effectiveness of hydraulic shock absorbers in eliminating high-speed steering wobbles.
| Identifier | ExFiles\Box 42\1\ Scan034 | |
| Date | 9th February 1926 | |
| COPY OF EXPERIMENTAL REPORT. REFERENCE Hs{Lord Ernest Hives - Chair}/RM{William Robotham - Chief Engineer}3/LG9.2.26. R.H. HYDRAULIC SHOCK ABSORBERS. We have carried out a series of tests to determine the benefit we are likely to obtain from the new R.H. hydraulic shock absorbers when used as a preventative for high speed steering wobbles. We find that with high pressure tyres, the hydraulic shock absorbers will eliminate all high speed wobbles likely to be encountered under the prevailing system of balanced wheels. We have a car which is singularly bad for wobbles, and with the well-base wheel and tyres could not be driven without this phenomenon being experienced unless the front tyre pressures exceeded 50 lbs/sq.in. With the hydraulic shock absorbers, however, the tyre pressures were lowered to 30 lbs/sq.in. without wobbles being set up. When the shock absorbers were disconnected violent wobbles took place with these tyre pressures. Though the new hydraulic dampers would appear to make the use of the semi-balloon well-base tyre quite practicable, we should like to point out that from our experience so far, this type of tyre is definitely more susceptible to high speed wobbles than the straight-sided Dunlop cord, the two main reasons being that it has a more effective non-skid tread and is a larger section. We carried out further tests with 6.25" balloon tyres inflated to 25 lbs/sq.in. We found that the Hydraulic dampers would cope with the wobbles set up by these tyres. We then tried 7.25" tyres at 20 lbs/sq.in. We found that we were unable to eliminate the wobbles produced by these tyres. As a matter of fact the violence of the wobbles was only slightly reduced by the dampers. This confirms our previous experience with these particular tyres, either the wobble is eliminated or it is present in a violent form. All the wheels in these tests were balanced and the shock absorbers loading was 150 lbs. on the ball end upwards, and 30 lbs. downwards. We have yet to make careful comparative tests for riding comfort. We still believe, however, that we shall gain more from the reduced tyre pressures than we shall lose from the heavy shock absorber damping employed. We are trying to see to what extent the loading employed can be reduced without decreasing the efficiency of the dampers. Hs{Lord Ernest Hives - Chair}/W.A. Robotham. | ||