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).
Tests conducted to understand and mitigate high-speed steering wobbles.
| Identifier | ExFiles\Box 29\1\ Scan166 | |
| Date | 12th June 1925 | |
| R.R. 498A (50 H) (D.D. 31. 12-6-25) J.H.D. EXPERIMENTAL REPORT. Expl. No. +457 REF: Rm{William Robotham - Chief Engineer}1/LGS.12.25. 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} EY. c. to Wor.{Arthur Wormald - General Works Manager} HIGH SPEED STEERING WOBBLES. X8430 We have carried out further tests to ascertain the effect of bringing the plane of the wheel in proximity to the plane of the pivot pin. In order to do this we arranged special hubs to take Michelin disc wheels, and obtained special disc wheels to take balloon tyres so that we could obtain wobbles without resorting to out of balance (see attached sketch) These wheels necessitated new steering arms, but the alteration necessary only affected the steering on considerable locks quite outside the range of a normal wobble. With the present pivots we were able to bring the plane of the wheel within 1.00" of that of the pivot pin. This gave a tyre contact of 1.597" inside centre point (see sketch). The tests were carried out with 6.75" balloon tyres at 20 lbs/sq.in. inflation pressure. The pivots were fitted up to N.sch.1896. No front shock absorbers were fitted. We found that with the wheels fitted up in the normal manner (i.e. dished in) and carefully balanced we could obtain violent wobbles from 45 m.p.h. upwards. We could not drive through the wobbles. These wobbles were quite as bad as we should expect to get with standard arrangement of wheel and pivot. We then reversed the wheels so that they were dished out. This made the plane of the wheel about 5.7" from the plane of the pivot pin, and the tyre contact about 3" outside centre point. contd :- | ||