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).
Analysis of shock absorber performance issues under different loads, temperatures, and oil viscosity.
| Identifier | ExFiles\Box 28\1\ Scan262 | |
| Date | 11th August 1931 guessed | |
| Messrs. Luvax Ltd. Acton, W.3. -2- Diagrams 3 and 4 show that overthe high frequency small amplitude movements, the maximum load of the ball end is reduced by about 25% and the mean load is only about 25% of what it should be. In our experience this means that the shock absorber is not replenishing fully. Oil is lost past the working clearance of the rotor and also in the case of the small amplitude high frequency movements it is working with only an emulsion of air and oil which again detracts from its effectiveness. However, a low pressure load of 12 lbs. ball pin does not interest us and in order that the shock absorber shall be able to cope with fast driving, we consider that it should be effective giving 100 lbs. upward and downward ball pin load as a minimum. Diagrams 5, 6 and 7 show the disastrous effect of increasing the load by this amount on the high pressure and the low pressure side, when working over a 4" stroke. We are inclined to think that this result is brought about by the fact that under these high pressures the thick oil is forced past the working clearances of the rotor but the replenishing valves are inadequate to cope with the amount lost each stroke, the result being that the shock absorber is totally ineffective over 50% of the stroke. Curve 8 shows the effect of increasing the temperature of the shock absorber, or in other words reducing the viscosity of the oil. Apparently the replenishing valves are more effective when the oil is thin, but under these conditions so much oil escapes past the rotor that the maximum pressure is never reached. Curves 9 and 10 show the light loads over the small stroke at normal temperatures, but it will be observed that practically speaking the shock absorber is doing no work. | ||