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).
Page of recommendations for designers on how to eliminate steering shimmy and improve vehicle stability.
| Identifier | ExFiles\Box 29\1\ Scan121 | |
| Date | 8th October 1925 guessed | |
| contd :- -24- in the steering. At the critical speed of the car (52 to 55 mph) it is possible to see clearly the independent spring of each wheel take up any position and remain there without moving while the wheels turn about their pivots. (6) In waiting for a steering to be evolved without shimmy the following ideas may be taken from our tests which may assist designers. (a) Reduce to the minimum the unsprung weight on the front. We have measured this deformation at 600 revs. per min. in making tests on out of balance with the front of the car suspended. (b) Make the steering with the minimum of back lash and with automatic compensation for wear. (c) Employ rigid connections (levers, steering tubes and arms etc. whose stiffness might be increased 20 to 25%), (d) Make the pivot axis coincide with the plane of the wheel. Very light steering will then be obtained which will compensate for the increased steering effort produced by balloon tyres. It will reduce (perhaps even suppress) shimmy. A wheel angle with the vertical of 3º and a castor of 6 to 8º will be necessary to give stability to the steering. (e) Balance the wheels carefully, dynamically if possible Make the chassis as rigid as possible. (f) Use springs of weak flexibility on the front axle to avoid resonance with the tyre and to improve in this way the suspension. We consider that this point should be gone over again. -------------------- contd :- | ||