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).
Steering and tyre performance tests conducted in France.
| Identifier | WestWitteringFiles\T\2January1929-June1929\ Scan205 | |
| Date | 26th April 1929 | |
| To Hs.{Lord Ernest Hives - Chair} and Rn.{Mr Robinson} from G.W.H. C O P Y. Hotel de France, Chateauroux, Indre, France. STEERING TEST UNDER THE FOLLOWING CONDITIONS Rear dampers 100 lbs. L. and 100 lbs. H.F. Front dampers 80 lbs. L. and 80 lbs. H.F. Front silent tread tyres 40 lbs/sq.in. pressure. Rear traction tread tyres 35 lbs/sq.in. pressure. Friction in steering taken at wheel 7 lbs. (1500 lbs. on ball ends.) Under these conditions the joggles are reduced by 30% generally, shocks or rapid movement of steering wheel are reduced by 75%. The jellying period 60/65 m.p.h. is noticeable. The oscillation 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 speed, the oscillations are more noticeable 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 distorting 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 10 to 20 m.p.h. 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 i.e., 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 realise at the beginning of the 10,000 miles test. We have since found out and proved that worn tyres (i.e. 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 periodicity of the road springs is not quick enough to respond to the wavy condition of the road surface, thus, there are continually movements when the springs are in a compressed condition and cannot respond to the slight ridges of the road surface. This fault is overcome considerably, not wholly, 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 m.p.h. We have tried our car at these speeds with and without dampers fitted. The feeling with new tyres contd:- | ||