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).
Steering geometry and the damped pendulum lever to address high and low-speed wobbles and shimmy.
| Identifier | ExFiles\Box 17\3\ Scan130 | |
| Date | 14th March 1927 | |
| Y7430 To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} c. to BJ. Wor.{Arthur Wormald - General Works Manager} c. to RG.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} c. to DA.{Bernard Day - Chassis Design} STEERING. 4457 With reference to R3/MS.3.27. (1) EAC.Vll GEOMETRY. From our tests on this chassis, we do believe that on a big car capable of high speeds, geometry is important if high speed wobbles and joggles are to be avoided. If the paths of the side steering tube and axle are almost coincident, the wheels are being perpetually steered slightly from side to side on a poor or undulating surface. This is an incentive to 'shimmy'. We have had excellent geometry on all Phantoms so far. We consider that we have improved EAC.Vll steering by reverting as far as possible to the conditions that we had on 'V' series. (2) DAMPED PENDULUM LEVER. We have definitely established that weak side steering tube springs increase low speed wobbles but reduce high speed wobbles. In the limit, we have shewn on our drum tests that without a side steering tube (equivalent to infinitely weak side steering tube springs) it is absolutely impossible to produce shimmy. The damper pendulum lever friction reduces low speed wobbles because in effect it stiffens up the side steering tube springs. For the same reason it increases the violence of high speed wobbles. In every test we have conducted, if we utilize the damping in this pendulum lever on a car that will wobble we augment this trouble. contd :- | ||