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 wheel swing, tire tread effects, and potential steering system improvements.
| Identifier | ExFiles\Box 29\1\ Scan197 | |
| Date | 23th February 1926 | |
| Oy6-E-22326 -3- February 23, 1926. you do not attempt to explain why it goes on swinging outwards. It seems to me the explanation is the same as that of the improvement affected by flat tire treads. Namely the natural conical movement of a wheel with a round-section tire when it meets the road at an angle. I have tried to show this in attached sketch. In a flat-tread tire this wrench from inward-pointing to outward-pointing would be considerably less. In fact if the tread were perfectly flat the only turning effect would be due to the castoring action of the wheels. This might be quite a lot though because one imagines that by the time the wheel has reached the straight-ahead position it is pretty nearly leaving the ground again on the next jump. It would account for the shimmy on the Lancia-Lambda. (What a filthy little thing that is. Saw one at the Salon in November.) From your observations it would be interesting to work out what gyro-static effect there would be tending to turn the wheel from the inward to the outward position. (Am going to try it.) Possibilities. I imagine that since the complaint is so widespread one can assume that something fairly radical is necessary to cure it. With due hesitation I offer the following suggestions:- (1) Hydraulic steering, as above. (2) A front axle of the live axle type, as sketch, having a flywheel on the inner end of each live axle running backwards at say 6 times the speed of the wheel and of 1/6th the moment of inertia of the wheel. This would neutralize the gyrostatic rocking effect produced in the axle by precession of the wheel in contact with the ground. (3) Apparently the cross-steering tube is the nigger in the woodpile. An equalizing mechanism in the steering gear might do the trick. (Perhaps this is only possible with dished wheels and vertical pivots in the plane of the wheel, as otherwise with "cambered" front wheels they would tend to run "toeing-out" and might scrub the tires.) | ||