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 amplitude of wheel wobble, comparing balloon tyres with high-pressure tyres.
| Identifier | ExFiles\Box 28\4\ Scan346 | |
| Date | 1st August 1925 | |
| R.R. 493A (50m) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. -3- Expl. No. REF: Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG25. 8.25 the wobble dies out. We carried out a test with the Chronograph to ascer- tain the respective amplitude of the two sets of wobbles which we were investigating in the tests with the hydraulic dampers. We found that while a wobble with balloon tyres would have an average amplitude of about 14° to 15°, that with high pressure tyres it would not have an amplitude above 7° to 8°. We do not mean by this that the amplitude of the wobble with high pressure tyres cannot exceed 8°. What we mean to infer is that we can get continuous high speed wobbles with high pressure tyres with amplitudes of about 8°, whereas the same sort of wobble with balloon tyres, whilst naturally occurring at a lower speed, also must have a larger amplitude. Under exceptional conditions with high pressure tyres we have had a wobble build up to an amplitude of 15°. This has only occurred on four or five occasions and in every case the brakes have been applied. A case in point was the one we quoted where the wheels left the ground for 10 ft. in turn. It appears to us that owing to the greater amplitude of the wobble with low pressure tyres, it is easier to damp out because we have more movement to deal with. On the other hand, there is always the fact that with high pressure tyres we have a definite out of balance force of 1 lb. being rotated at high speeds tending to produce wobbles - the low pressure on the other hand being in balance. We are improving the Houdaille shock absorbers and are repeating our tests. contd :- | ||