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).
Investigating the cause of a high-speed steering wobble.
| Identifier | WestWitteringFiles\S\June1928-August1928\ Scan116 | |
| Date | 21th August 1928 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c.c. to BJ. Wor.{Arthur Wormald - General Works Manager} c.c. to E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} c.c. to EY. ORIGINAL Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG21.8.28. 12-C-4 - STEERING. X5430 X5820 X457 We tried this car as soon as it returned from WW: We found that it had a normal incipient high speed wobble from 56 m.p.h. upwards. The wobble was intermittent and so did not build up to any extent. As far as we could see the frame was going forward of the X shaped member to a certain extent, but the movement was exaggerated owing to the body being fully isolated and rather flexible. We checked the tyre pressures. They were 23 lbs/sq.in. all round. We attribute the wobble to :- (1) Low tyre pressure. As soon as we raised the tyre pressures to 35 lbs/sq.in. all signs of the wobble vanished. (2) Small dia. wheels. Although we have run 20 HP. front tyres at this pressure previous we have never had wobbles with balanced wheels. We anticipated that the 19" rims would be bad for wobbles for two reasons : (1) Reduced rotational moment of inertia of the wheel. We had exactly the same trouble with 6" tyres on the 40/50 and so had to go to 6.75". Recently we have proved on the 40/50 that Rapsons 6.75" tyres with heavy deflector tubes are less prone to wobble than the Dunlops. (2) The wobble is in step with the wheel rev. contd :- | ||