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 note listing the various factors that affect vehicle wobble.
Identifier | ExFiles\Box 170\3\ img065 | |
Date | 17th June 1931 | |
Wobble. (Supplementary Notes) June, 17, 1931. We know of many things which actually do affect wobble. (There are several others the effect of which is not yet definitely established). The list is as follows :- Wobble is affected by :- 1. Caster effect. This determines the amount of excitation. Increased caster also slightly raises the frequency. 2. Engine Mount. "Tuning" of the engine vitally affects wobble, and it is to be investigated next. 3. Moment of inertia about kingpin. Increased inertia encourages wobble and discourages shimy, hence more wobble tendency on 'bonnet', more shimy tendency on 'fentons'. 4. Stiffness of the whole steering mechanism. Increased stiffness discourages wobble, but possibly encourages shimy. 5. (2) and (4) above amount to saying that wobble is affected by the particular frequency of the wheels about the kingpins, increased within limits as the frequency is lowered. 6. Damping. Damping friction in kingpins reduces the amplitude of wobble for a given excitation and spreads the range of caster offset which may be used without wobble. 7. Speed. For any given caster there is a definite range of speed through which wobble may be produced and will continue when it is started. 8. Shock absorbers. Low orifice damping reduces wobble. This shows there is some movement in the suspension though this is small. 9. Road surface. High traction coefficient between road and tire encourages wobble. 10. Reversibility of steering gear. The effect is not predictable, sometimes increased reversibility encourages wobble, sometimes the reverse. Other factors of which the value is unknown 1. Offset before or behind kingpin. Theoretically weight behind kingpin (i.e. pusher type) increases | ||