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 gear beliefs, the causes of 'rubbery' steering, and Dubonnet suspensions.
| Identifier | ExFiles\Box 170\3\ img026 | |
| Date | 26th March 1936 guessed | |
| -3- (5) We arrive at two conclusions, contrary to the general beliefs, that steering gears should be rigid and that soft engine mounts have caused steering trouble. We find that many steerings can be improved by increased flexibility and that engine mounts are tuned too fast for best results. Also that engine frequency on its mounts and flap frequency of the front wheels should be equal or nearly so, to give freedom from wheel fight. (6) "Rubbery" Steerings. The feeling of a rubbery steering does not necessarily depend on the flexibility of the steering mechanism. All of the following factors appear to lead to complaints of a rubbery steering :- (a) Excessive caster (because of increased torque about kingpin in side winds on cambered roads). (b) Excessive friction in steering (because in combination with flexibility this gives an actual lost motion at the steering wheel). (c) Strong understeer or strong oversteer in handling. (Because in both cases there is a sense of sluggish response in handling. (d) Excessive front stabilizer. (because by heavily loading the outer front wheel on turns it increases the self-straightening torque of the front tyre). (7) Dubonnet Suspensions. All of these approximately double the moment of inertia of the masses swinging about the kingpins, as compared with wishbone or front axle. Therefore for a given natural flap frequency the steering mechanism must be twice as stiff. And this increased stiffness gives a proportionate benefit in precision of handling. The demand on these tyres is therefore for a stiff steering hook up; otherwise they will show wobble tendencies. I believe that the steadier steering often shown by wheels with increased offset on axles and wishbones is chiefly due to increasing the moment of inertia round the kingpins and therefore lowering the flap frequency. | ||