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 wheel shimmy, detailing its principal movements and effects on the chassis and steering system.
| Identifier | ExFiles\Box 29\1\ Scan101 | |
| Date | 8th October 1925 guessed | |
| contd :- -4- 'comfort' tyres 880 X 160 mm; at 1.5 klgms. (21.4 lbs/sq.in.) inflation pressure, enabled us to announce the following. The wheel shimmy started on dry and even ground at a critical speed of 80 to 85 kilometers per hr. It could be resolved into two principal movements of the same periodicity, 1/10 to 1/12 of a sec. (a) Wobbling or oscillation of the front wheels on the pivots during which the whole of the wheels, levers, steering rods play the part of a scale having for their beam, the steering rods, for knife edges the axle pivots, and for the scale pans the wheels. (b) The bounding or vibration of the front axle about the axis AV-AR during which one of the tyres strikes the ground being deflected inwards while the other tends to leave it. See graph No.3. In this movement there seems to be resonance between the period of vibration of the tyre and that of the springs. We have however been unable to prove this. When shimmy starts, the chassis is shaken violently - the radiator cap seems to be rapidly moved to the right and left. The movement sometimes attains such a large amplitude that owing to the/reversibility of the steering, it is felt upon the steering wheel. The amplitude of the wobble, which is initially feeble, grows rapidly and sometimes attains, when the ground permits it, that is to say when inequalities do not destroy the periodicity, an amplitude likely to cause fractures in the steering system. We have been able to take a copy of contd : | ||