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 suspension and shock damper issues, particularly concerning noise, efficiency, and component deflection.
| Identifier | WestWitteringFiles\V\December1930-February1931\ Scan002 | |
| Date | 2nd December 1930 | |
| -2- enormously in the last few years are average speed and road surfaces, the latter particularly now giving us waves or undulations instead of pot-holes and so requiring different treatment. (b) The universal use of the closed car has increased our troubles due to shock absorber noise. Dampers which are quiet with test bodies or certain types of coach-work become clearly audible on other coachwork. We can say that our service difficulties with regard to inefficiency have been negligible, but with regard to noise, considerable. PRESENT REQUIREMENTS. SUSPENSION. We attach a series of indicator diagrams of the existing Phantom II and 20 HP. dampers. It will be observed that the efficiency of the damper varies from about 50% at high frequency one inch oscillations to 90% at low frequency large oscillations. The cushioning at small amplitudes, that gives us the soft low speed ride, is very clearly indicated. As we are working with a steam engine indicator having a .5" dia. piston with a .400 stroke we lose a small portion of the 1" stroke diagram operating the indicator (15% approx.) We have allowed for this in calculating the hydraulic efficiency though it is not shewn on the diagrams. We attribute the shape of these one inch stroke diagrams to - (1) Deflection of the shock damper lever and shaft, a separate analysis of which we attach. It will be noted that our latest section lever is an improvement. The proposed shorter lever should be still better. (2) Deflection of the shock damper, cylinder, and leakage past the piston. The cylinder only goes out .003 - .004 on the dia. under normal loads measured by a clock on the outside of the case. (3) Emulsification of the oil due to air content. This is indicated by the fact that the efficiency of the damper falls as soon as the air vent is closed. Whilst this characteristic of the damper is desirable for a soft low speed ride, for which it was originally designed, it is not ideal for - (a) Prevention of Pitching. We find that we get better results with a | ||