Steering and tyre performance tests, detailing the effects of dampers and tyre wear on ride quality.
| Identifier | ExFiles\Box 11\2\ 02-page217 | |
| Date | 26th April 1929 | |
| To Hs. {Lord Ernest Hives - Chair} and Rm. {William Robotham - Chief Engineer} From G.W.H. Hotel de France Chateauroux(French test region) Indre 65 26/4/29 STEERING TEST UNDER THE FOLLOWING CONDITIONS Rear dampers I00 lbs L and I00 lbs HP. Front dampers 80 lbs L and 80 lbs HP. Front SILENT TREAD tyres 40 lbs sq. inch pressure; Rear TRACTION TREAD tyres 35 lbs sq. inch pressure. Friction in steering taken at wheel 7 lbs. (1500 LBS ON BALL ENDS) Under these conditions the deggles are reduced by 30% generally, shocks of rapid movement of the steering wheel are reduced by 75%. The jellying period 60 -65 M.P.H. is noticable. The oscilation of the steering wheel during this period is short but rapid.(The amount of jellying movement is less by 80% than what was seen in Derby.) At speeds up to 60 M.P.H. there is very little movement of the wheel, above the period the oscilations are more noticable but the wheel can be held quite steady by one hand and the steering is safe. This setting of the front dampers is too much the frame is disterting instead of a full movement of the dampers. At speeds of 30 M.P.H. there is a series of shudders going through the frame, this applies also but reduced at 20 M.P.H. The steering wheel at these speeds is perfectly steady. At speeds of I0 to 20 MPH the steering is on the heavy side. TEST ON TYRES AND THEIR EFFECTS We have reported to you the effect that tyres have on joggles, (ie)a worn tyre decreasing them. We would now like to point out how the wearing of tyres affects the riding of the car at speeds up to 30 M.P.H. We reported that our car at slow speeds rode like a truck. This was a feature that one did not notice or realize at the begining of the I0,000 miles test. We have since found out and proved with worn tyres(ie the tread worn off) the riding of the car becomes hard although the tyres pressures are kept the same. This is due to the fact that the periodicy of the road springs is not quick enough to respond to the wavy condition of the road surface, thus, there are continually moments when the springs are in a compressed condition and cannent respond to the slight ridges of the road surface. This fault is overcome considerably; not wholey, by tyres that have a good tread. The extra rubber supplying the elasticity that the springs cannot cope with. The difference between smooth worn tyres and new tyres gives a 25% difference in the riding qualities of the car at speeds up to; 30 MPH. We have tried our car at these speeds with and without dampers fitted. The feeling with new tyres and no dampers is that the car is riding at times hard and produces small shocks Throughout the car certainly felt mess in the front seats than in the rear. With tyres that are worn these shocks and the general riding of the car is increased considerably, so much that a customer would have a right to say the riding was hard. This is not due to stiffness of road springs, the car floats up and down with any unevenness of the road surface. We have come to the conclusion that to have dynamic restriction in the dampers is wrong and we have proved it's value is not benifical for high speed work. More so on the rear than the front. | ||
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).