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 wobbles, testing the effects of tyre pressure, wheel gather, and steering tube springs.
| Identifier | ExFiles\Box 28\4\ Scan281 | |
| Date | 12th June 1925 | |
| R.R. 488a (50 M) (D.{John DeLooze - Company Secretary} D.{John DeLooze - Company Secretary} 31. 12-6-25) J.H.D. EXPERIMENTAL REPORT. -3- Expl. No. REF. Hs{Lord Ernest Hives - Chair}/Rml/LG17. 8. 25. In addition, the rotational moment of inertia of the balloon tyre and wheel is 15% less than the standard straight sided tyre and wheel. If therefore gyroscopic forces enter into the problem, the balloon tyre has an advantage here. If, however, by some alteration to the chassis, the period of the wobble with high pressure tyres was reduced, the wobble would be almost certainly worse from the customers point of view. EXPERIMENTS ON HIGH SPEED WOBBLES. We have carried out the following tests :- (a) Tyre pressures. Very marked effect on wobbles. An almost uncontrollable wobble with 35 lbs/sq.in. tyres can be reduced to almost negligible proportion by increasing pressure to 60 lbs/sq.in. (b) Wheel gather. Experiments first carried out with 4½° backward lean on the pivots showed that toe-in over .5" produced and augmented wobbles. Subsequent experiments with standard pivot lean have reduced the effect of toe-in so that it is difficult to say definitely that 1" toe-in makes wobbles much worse than with parallel wheels. Toe-out under these conditions, however, definitely improves matters slightly. (c) Side steering tube springs. Weak side steering tube springs are a definite improvement. They do not allow wobbles to build up, and when the car is wobbling the driver is hardly conscious of the fact as the shocks reach him in a very reduced form. The actual contd:- | ||