Steering tests, detailing issues with front dampers, shocks, and ride quality at different speeds.
| Identifier | ExFiles\Box 11\2\ 02-page239 | |
| Date | 5th May 1929 | |
| To Hs {Lord Ernest Hives - Chair} and Rm. {William Robotham - Chief Engineer} From G.W.H. X7941 Hotel de France Chateauroux(French test region) Indre 5/5/29 STEERING TESTS WITH THE FOLLOWING CONDITIONS LOAD ON THE CROSS STEERING TUBE 6.75LBS LEAN OF PIVOTS 2 1/2° TOE IN .125" FRONT TYRE PRESSURE 45 LBS UNDER RUNNING CONDITIONS. FRONT DAMPERS 60 LBS L AND 60 LBS HP. SELECTIVINESS UNDER THESE CONDITIONS IS NOT SO GOOD AT SPREDS OVER 50 M.P.H. SHOCKS ARE INCREASED. THE JELLYING PERIOD IS INCREASED. FRONT OF CAR BOUNCES TOO MUCH. You have raised the query " Why restrictions in the front dampers" and our answer is that we are not entirely satisfied with the combination. We will give our reason for this and should be very pleased if you will confirm or otherwise. We do not say that it is correct but observation and results rather confirm it. The front shock dampers have two features to perform. The main feature is riding smoothly and to obtain this, very little damping is really needed on the front of the car. The second feature is the effect on steering which the dampers control. The ideal damper required is one with a positive load immediately the lever is moved. There must be as little free movement as possible. This load must not be too great to spoil or make the riding hard at slow speeds. The load must rise very rapidly and should be even L and H pressure. The maximum load must deal with bumps at high speed when the full weight of the front of the car has to be dealt with. Joggles and shocks are caused by springing, castor action of pivots and side and cross steering tube loads. The best result with steering is obtained by heavy damping which controls the movement of the springs and in turn controls the castor action of the pivots but this would make the riding of the car hard generally. If we come to our actual tests say 60 lbs L and 60 lbs HP at medium speeds with no restrictions the results on a wavy road are poor, because there is not sufficient damping for the radial movement of the damper arm of say 1.5" either side, thus we get the pivot action lifting the front end due to the road spring movement which is conveyed to the steering in the form of joggles. To obtain the load for the small movement of the damper is difficult, if we are to maintain the riding qualities for high speed work, therefore we are at present in sympathy with using the restriction which gives us what we want at lower speeds. The restriction poundage plus the valve poundage gives us right amount for the maximum movement. We do not say that the restriction is ideal, a preferable way would be to use four valves, two to deal with the movement of the damper say 40% giving a load of round about 80 Lbs. | ||
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).