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).
Technical memorandum discussing steering geometry, wheel wobble, and potential solutions to reduce road shocks.
| Identifier | WestWitteringFiles\S\March1928-May1928\ Scan086 | |
| Date | 2nd April 1928 guessed | |
| contd :- -2- violently, does not lead us to suppose that parallel moving wheels are a certain cure from our present troubles. We think that the Lancia steering with balloon tyres is very far from perfect. The only means that we know of at present to reduce road shocks and the tendency for an incipient wobble, is to push the plane of the wheels still further from the plane of the king pins. At the moment we are 1.26" out of centre point with 13/1 overall ratio. If we use a 16/1 overall ratio we should be able to go to 1.76" out of centre point without any possibility of one front brake only in action causing an unpleasantly powerful pull on the drivers' hand (at present trouble in this direction is non-existent). Mon. Sensaud de Lavaud has written and elaborate and exhaustive mathematical treatise on Shimmy and Road Reactions and though we do not agree with some of his reasoning and deductions, his three most emphatic points are :- To reduce the chance of wobbles : (1) The steering must be reversible and incorporate some flexibility therein (weak s.s. tube springs). (2) Pushing the plane of the wheel further from the plane of the king pin reduces the chance of wobbles. (3) Big cars are very sensitive to pivot lean and a slight variation can cause Shimmy to build up. We think M.{Mr Moon / Mr Moore} De Lavaud probably got his facts from the Michelin Co. and made his theories fit in, but the information confirms our results. We propose to try a test with pivots giving a wheel plane .5" further f- | ||