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).
The results of tests on high-speed steering wobbles using different tyre pressures and damping.
| Identifier | ExFiles\Box 28\4\ Scan345 | |
| Date | 1st August 1925 | |
| R.R. 493A (50m) (D.B. 175 25-9-24) J.H.D. -2- Expl. No. REF. Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG25. 8. 25. EXPERIMENTAL REPORT. TEST A.{Mr Adams} We found that without making the steering unduly heavy (8 to 10 lbs. at the steering wheel rim suffices to turn the road wheels at a fair speed with the axle jacked up, the shock absorbers being warm), we could entirely eliminate high speed wobbles with balloon tyres. On fitting high pressure tyres, however, we found that the damping effect was not nearly so marked. In this case quite appreciable high speed wobbles built up; we should say that the improvement due to the hydraulic damping was no more than 40% to 50%. TEST B. The results of this experiment closely followed those of Test A.{Mr Adams} High speed wobbles with high pressure tyres were reduced in violence by 50%. With low pressure tyres the elimination of wobbles was not quite complete, the steering having a tendency to oscillate on a rough road at a critical speed where wobbles would have normally taken place. Wobbles would not build up however. These results confirm what we have previously ascertained with friction damping i.e., that the true high speed steering wobble is much more difficult to eliminate entirely than the relatively low speed 'high speed steering wobble' brought about by balloon tyres. We offer the following explanation :- Wobbles as far as we have measured them, appear to require a certain minimum amplitude which must be maintained if they are to continue. The amplitude may increase under exceptional conditions but if it falls below a certain minimum contd:- | ||