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).
Wheel wobble, conical precession, and the effects of tyre pressure and axle geometry.
| Identifier | ExFiles\Box 28\4\ Scan363 | |
| Date | 1st August 1925 | |
| R.R. 493a (50 H) (D.D. 31. 12-6-25) J.H.D. EXPERIMENTAL REPORT. -2- Expl. No. REF: Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG31 8. 25. always be the greatest in the immediate vicinity of this one road speed. In practice the period of [strikethrough] the most violent wobble varied from 66 to 48 m.p.h., varying the tyre pressure from 60 to 35 lbs/sq.in. This seems to indicate that the transverse period of the axle is of far greater importance than conical precession. Distance from king pin to wheel plane. Healey definitely states that from his theory of conical precession, a wobble which occurred at 25 m.p.h., when the plane of the wheel is that of the king pin, should occur at 50 m.p.h. with the wheel moved 6" out of centre point. Our recent test with the Michelin disc wheels and vertical pivot axle have almost exactly reproduced these conditions with the exception that the distance moved from centre point was 5 1/4". We found that while the intensity of the wobble was altered, its period occurred for all practical purposes at the same road speed. With regard to the model, a sketch of which you have sent to us. We suppose the object is to ascertain the angular velocity of the wheel at which a conical precession will take place about the fixed point. We suggest that we make the distance from the anchoring point to the plane of the wheel variable to see whether altering this dimension affects the system in the manner expected. The model should tell us if a conical precession is possible under these conditions. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||