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).
Analysis of steering shimmy, the role of suspension components, and the effect of shock absorbers.
| Identifier | ExFiles\Box 29\1\ Scan115 | |
| Date | 8th October 1925 guessed | |
| contd :- -18- (1) The extremity of the pendulum lever. (2) The ball joint on the side steering arm. (3) Front spring shackles are in a straight line and occupy such a position that the arc of displacement of the ball joints when the springs are compressed or extended, are reasonably coincident (see graph 1.) In cases where the opposite occurs we have proved that shimmy starts itself more easily and that re-actions on the steering are more violent. We were able to take measurements of coincidence of arcs in the following fashion. [handwritten: Description of tool omitted] In the case of the conditions enumerated above i.e. of rating and flexibility, springs maintain shimmy or contribute to maintain its intensity. In the first case their action is comparable to that of an electric pendulum whose movement is maintained by impulses constant but feeble. In the second the phenomenon is analogous to that of a suspension bridge where the rhythmical impulses of a marching troop can smash the suspension cables. We have made tests with springs blocked up without eliminating shimmy - its violence increased considerably. (see diagram - test 21.) The critical speed diminishes and the period of oscillation increases to 15/100 ins. [handwritten: ths.] instead of 10/100 ins. [handwritten: ths.] per second. Good shock absorbers reduce shimmy and its action on the steering wheel. It is essential that they should act without lag. Conclusions. On cars which do actually employ weak springs, fit shock absorbers (see graphs.) contd :- | ||