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).
Tests conducted to understand high-speed wheel wobble on tyres.
| Identifier | ExFiles\Box 29\1\ Scan053 | |
| Date | 15th September 1925 | |
| R.R. 493a (50 H) (D.D. 21. 12-6-25) J.H.L. -3- Exptl. No. REF: Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG15.9.25. EXPERIMENTAL REPORT. on the tyres, the wobbles instantly vanished completely. This was with balanced tyres. We repeated the test with 1 lb. out of balance on one wheel, we could still 'kill' the wobble. We tried pouring water on one wheel only, this had exactly the same result as long as plenty of water was kept on the tyre. We made a second test in which we lifted the axle clear of the drums when it was wobbling violently, the moment the tyres left the drums the wobble died out. We could not maintain the slightest wobble in the air with 1 lb. out of balance on one wheel. For these tests a standard Phantom car was used with standard pivot lean and 7.25 balloon tyres at 20 lbs/sq.in. (c) From the previous tests, indications have been given that the gyrostatic couple caused by turning the rotating wheel through an angle is of relatively small importance compared to the reaction of the ground while conical precession is non-existant. We carrIed out a further test in which we observed the wobble by means of the oscilloscope. We noted that all the angular movement of the wheel about the king pin appeared to take place at the top and bottom of the criss cross bounce i.e., when the observed wheels WERE [handwritten correction 'WAS' above] in contact with the ground, and when the other wheel was in contact with the ground. When the wheel was rising and falling it did not appear to turn. We therefore have to modify our theories of the high speed wobble to a certain extent. We still believe that the criss cross period of the axle and the tyre are of primary importance as they dictate the speed at which the wobble contd:- | ||