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 of and solutions for front-end wobble, identified as an 'epidemic' linked to out-of-balance tyres.
| Identifier | ExFiles\Box 28\4\ Scan310 | |
| Date | 1st August 1925 | |
| To Hs.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} c. to CJ. BJ. c. to PN.{Mr Northey} BY.{R.W. Bailey - Chief Engineer} EP.{G. Eric Platford - Chief Quality Engineer} STEERING. X.8430 X.457 +457 We have wired you today as follows :- "PROBABLY FRONT SHOCK DAMPERS MORE EFFECTIVE THAN "AT PRESENT REALISED. TO REDUCE CRISS CROSS "VIBRATIONS AXLE TEST NORMAL WITHOUT ANY AND "DOUBLE USUAL AMOUNTS". ROYCE+ I fear I have not made myself clear as regards con-demning out of balance tyres. So far as we have seen it would appear that the epidemic we are experiencing arises from firstly an attempt to use low pressure tyres on heavy high speed cars, and secondly, the Dunlop Co. sending out tyres which are badly out of balance. The latter is a temporary measure which ought to be rectified thoroughly, and at once. I am presuming that other first class makers of tyres have not been guilty of turning out the tyres which are badly out of balance, and therefore most cars have not experienced trouble except with balloon tyres. So far as wehave tested we have come to the conclusion that the phenomenon is most likely to be started by an out of balance wheel, that its periodicity as we anticipated coincides with the wheel revolution, and that the periodicity at which the wobble synchronises is that of the axle on the road - one end rising while the other falls, - and would therefore depend chiefly upon the tyre pressure and the weight of the ends of the axle - that is, including brakes, wheels, tyres etc. Also that the system probably obtains its energy by retarding the car due to its lateral movement just in thesame way as low speed wobbles obtain their energy. We know of no way to prevent or change the whole phenomenon except what has been described - i.e. (1) tyre pressure, (2) balance, and (3) more effective shock dampers. We can however prevent it being communicated to the driver's hand by making the steering slower, more irreversible, and using slightly more flexible springs between the steering and the road wheels. Unless the foregoing is proved unsound, it is only open to us to keep in the system as much damping friction as will permit of easy steering. At the moment this damping friction can be of 3 kinds - (1)on the pendulum lever, which as far as can be seen can be of no harm, (2) on the steering pivots, which would be always there, and might render the steering too heavy and sluggish, and (3) the hydraulic damper carried on the axle, which may act perfectly without serious objection, but is undesirable as it entails extra parts, and it also may prevent contd:- | ||