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).
High-speed steering wobbles, conical precession theory, and the effect of tyre pressures.
| Identifier | ExFiles\Box 28\4\ Scan362 | |
| Date | 31th August 1925 | |
| R.R. 495a (50 H) (D.D. 31, 12-6-25) J.H.D. 4457 EXPERIMENTAL REPORT. Expl. No. REF Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG31.8.25. To DA.{Bernard Day - Chassis Design} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} HIGH SPEED STEERING WOBBLES. c. to R.{Sir Henry Royce} With reference to your DA{Bernard Day - Chassis Design}1/M24.8.25. and subsequent note with regard to conical precession, personally we cannot quite follow Mr. Healey's reasoning on this subject. To our mind the analogy between a spinning top precessing about a point with unrestrained motion, and the movement of a wheel restrained by a pivot, and front axle restrained by springs, is rather remote. The idea of a conical precession without torque promiting forces of sufficient magnitude to influence materially the disturbance which takes place at the front of a car during a high speed wobble, does not seem to us to be feasible. In addition, we have the following practical results which seem to indicate that even if conical precession theory is correct, its disturbing influence is of entirely insignificant proportions compared with the causes of wobble with which we are dealing at the present time. Tyre pressures. We have carried out a number of tests on the effect of latering tyre pressures - Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}1/LG17.8.25. In these tests, the only variable in the system was the tyre pressure. Now all the moments of inertia of the system being fixed, if the theory of conical precession is worth considering, we should expect to find that all our wobbles appeared about one critical speed, and though the period might be extended, the intensity would contd :- | ||