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 control of B.V. front dampers, evaluating the effectiveness of a bellows control system.
| Identifier | ExFiles\Box 99\3\ scan0166 | |
| Date | 15th August 1939 | |
| To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale} c. DA.{Bernard Day - Chassis Design} c. Mx.{John H Maddocks - Chief Proving Officer} c. Da{Bernard Day - Chassis Design}/DB.{Donald Bastow - Suspensions} c. Rm{William Robotham - Chief Engineer}/INW. c. Rm{William Robotham - Chief Engineer}/FD.{Frank Dodd - Bodies} 442 Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale}2/WH.15.8.39. CONTROL OF B.V. FRONT DAMPERS. It has been suggested that certain of our newer experimental cars should have "bellows control" of the front dampers, that is, a system of varying the spring load on the blow off valve from the driver's seat. The object of this report is to show why this system cannot be of any assistance in preventing excessive movement of the car thus fitted, in the present circumstances, and to suggest a better one. The present setting of the front dampers on B.V. production is 110 lbs., 3 secs. leak. Formerly it was 125 lbs., 1 1/2 secs. leak. With the present settings, when the oil is warm in the damper, the main valve does not open when the car is just pitching or bouncing unless the stroke of the front suspension exceeds 4". Now the maximum stroke, metal to metal, is only 6" and the normal stroke on rough roads is some 3" to 4". The stroke, buffer to buffer, is 3" and in towns the movement is unlikely to exceed 2". The indicator diagrams Figs. 1 and 2 show fairly clearly that with a 3 second leak the valve does not open unless the stroke reaches 4" when set at 110 lbs. (production setting). Fig. 2 shows that the valve would not open even at 150 lbs. setting if the front end was bouncing from metal stop to metal stop. A car could hardly be said to be riding comfortably if the stroke exceeded 3" even at high speed. We have tried controllable valves in the front dampers of various cars and nobody has been able to say that car movement can be reduced by putting pressure on the bellows. The ride records, Figs. 3 and 4, bear this out, the small differences between them are probably due to instrument or tracing errors rather than shock damper settings. We changed from 1 1/2 seconds leak to 3 seconds leak on B.V. in order to check pitching with hot dampers. With the original system of bellows control we did not use any leak at all, but this was found to be rather harsh and frequently leaks were added to satisfy individual customers. On P.III | ||