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).
Wraith steering characteristics, over-steer, under-steer, and investigations on a skid pan.
| Identifier | ExFiles\Box 9\7\ 07-page097 | |
| Date | 17th December 1937 | |
| To By.{R.W. Bailey - Chief Engineer} from RM{William Robotham - Chief Engineer}/ISV. c. Hs.{Lord Ernest Hives - Chair} c. Da.{Bernard Day - Chassis Design} c. Ev.{Ivan Evernden - coachwork} c. Da{Bernard Day - Chassis Design}/Hdy.{William Hardy} 8 650 WRAITH STEERING CHARACTERISTICS. AND INVESTIGATIONS ON SKID PAN. The first Wraith sent to France, 26.G.VI, showed that the new chassis had a steering so much lighter than the Phantom III and selectively and directional control so much better than the 25/30 that no adverse comment was raised against it in the early reports. On the other Wraith cars at Derby the steering was likewise accepted without comment simply because it was so much better than any previous R.R. production. Careful observation of the behaviour of 26.G.VI by RM{William Robotham - Chief Engineer}/Les.{Ivan A. Leslie} during his visit to Chateauroux led him to complain of a slight tendency to over-steer on straight roads when front and rear tyres were equally inflated to 30 lbs/sq.in. The front tyres were, therefore, run at 25 lbs/sq.in. which improved the directional control on straight roads, although the car still over-steered on corners. The lower front tyre pressures made the steering heavy and this was objected to. To overcome this the castor angle was reduced from 1 1/2° to 1/2°, the car used for this test being 27.G.VI. The steering was then very light and pleasant with 25 lbs/sq.in. front tyre pressure. The reduced load in the steering linkage enabled softer springs to be used in the side steering tube without increasing the sponge in the steering. This eliminated the slight joggles which had been experienced on all the Wraith cars. The car now appeared to under-steer on the straight and over-steer on corners, and with the very light steering it was difficult for the driver to feel the change of characteristics on entering a corner. The result was that car would frequently follow a sharper curve than anticipated by the driver, who would unexpectedly find himself on the wrong side of the road. | ||