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 causes and testing of high-speed steering wobbles, or 'shimmy'.
| Identifier | WestWitteringFiles\O\2January1926-March1926\ Scan74 | |
| Date | 1st February 1926 | |
| Expl: Report. Expl: No. 457 Ref. Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LCG.2.26 To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to CJ. BJ. c. to RG.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} c. to DA.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} HIGH SPEED WOBBLES. We believe that the extent of the variations which can exist between different cars of the same type with regard to high speed steering wobbles, are not fully realised. Once a car has had a violent attack of 'shimmy', it is always more susceptible to a recurrence of the phenomenon. We have an excellent example of this in the Experimental Dept. at present. The car upon which we have carried out all our wobble tests up to the present will wobble on the slightest provocation. With Dunlop straight sided cord tyres at 45 lbs/sq.in. (no shock absorbers) and carefully balanced wheels, we can actually experience quite a violent wobble on this car whereas we have the greatest difficulty in finding any standard car which will shew the least signs of a wobble under these conditions. We have already demonstrated in our tests the extent to which tyres vary due to unavoidable manufacturing limitations. It is very difficult to explain adequately the reason for the way cars become 'immoculated' with wobbling tendencies. It appears to be due mainly to the cumulative effect of the increased freedom of the parts concerned due to the violent movements that they undergo. Re-fitting spring shackles as an example, will improve a bad car slightly. We therefore consider that it is most necessary to try the maximum number of cars, or a particularly bad car, contd:- | ||