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 nature and causes of wheel wobble, including observations of tire marks on the road.
| Identifier | ExFiles\Box 28\4\ Scan315 | |
| Date | 21th August 1925 | |
| R.R. 493A (50m) (D.B. 175 25-9-24) J.H.D. -3- EXPERIMENTAL REPORT. Expl. No. REF Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG21.8.25. The amplitude is in excess of 8° as the instrument was set to record only those wobbles causing a greater angular movement of the wheel than this. We cannot see why the period of the wobble should coincide with the period of a wheel revolution, unless the wheel is out of balance. We therefore conclude that the small amount of out of balance of the wheel was sufficient to start the wobble at the road speed where the wheel revs. period coincides with the criss-cross period of the axle. Nature of a wobble. We are satisfied that whenever we get a high speed steering wobble the front axle vibrates in a criss-cross manner. We have observed a car wobbling by driving in front of it, each wheel can be actually seen to leave the ground in turn. After one particular violent wobble we examined the marks left on the tar-macadam surface of the road. These shewed clearly that during the worst part of the wobble each wheel was off the ground in turn for a considerable distance. We measured the distance between two consecutive points of contact between the tyre and the road. We found this to be from 7 to a max. of 10 ft. The marks left on the road were thus :- <diagram of tire marks with '10 FT.' dimension> Our explanation of the wobble is almost exactly that of Mr. Healey. The front axle has a criss-cross period of vibration. The frequency of this period is altered by :- | ||