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).
Causes and potential solutions for high-speed steering wobbles.
| Identifier | ExFiles\Box 29\1\ Scan003 | |
| Date | 1st September 1925 | |
| To BY.{R.W. Bailey - Chief Engineer} from R.{Sir Henry Royce} c. to CJ. BJ. c. to PN.{Mr Northey} CWB. c. to Hs.{Lord Ernest Hives - Chair} DA.{Bernard Day - Chassis Design} +457 R1/M1.9.25. X.457 X.8430 X.8520 STEERING - HIGH SPEED WOBBLES. Many thanks for your suggestion that inertia damping might be used in connection with high speed wobbles. Certainly we had never thought of this, but I fear that to get any effect would entail the use of too much dead weight either upon the axle, or upon the front end of the car. Moreover one feels as though we have ultimately got to find some way of avoiding the tramping period as a period within reach of the speed of the car and the revs. of the wheel. If you still think your idea of inertia damping practical, I shall be pleased if you will arrange one or two small experiments to find out its value. Apparently the situation has not altered very much this last few days, and as it stands it appears that whenever the wheel rev. matches the tramping speed, and there is any out of balance, tramping and wobble occurs. The system oscillating appears to be fed once in every road wheel rev. and that the oscillating system is only fed when it coincides with the road wheel speed. This is very mysterious, and perhaps can only be accounted for by the fact that the road wheel, if fairly good balance to begin with, gets more out of balance. We cannot find any reason for a gyrostatic period. We were almost expecting to find some gyrostatic period which was one to one with the road wheel, and which had been rendered one to one by the addition of the brake drums, or added weight, but we can now only conclude that the additional weight has so reduced the tramping speed as to bring it within reach of the speed of the car. There are still some very feeble links in the chain of theories and experimental results, but so far as we can trace no gyrostatic period anywhere near one to one. We are however convinced without a doubt that the tramping acts gyrostatically to set up the wobble around the steering pivots, that this same gyrostatic transmission takes place in all cars at all speeds when a criss cross change of the axis takes place, such as in following over hillock, or in dropping into a single pothole, and worst of all when there is a pothole one side and contd :- | ||