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 vehicle dynamics, focusing on lateral and rotary acceleration, and the causes and variations of wheel wobble.
| Identifier | ExFiles\Box 170\3\ img044 | |
| Date | 14th July 1933 guessed | |
| -15- One can see therefore from the observed cycle :- 1. A maximum lateral acceleration of the car at about A' and C' followed by a maximum displacement of the car less than 90° later. The car is therefore probably rocking at slightly less than its natural frequency. 2. A maximum rotary acceleration of the wheels some here between A' and B', and again somewhere between C' and D' followed by corresponding displacement of the wheels of their extreme wobble positions, after more than 90° of phase. Suitable conditions exist therefore for feeding energy both into the car motion and the wobble, provided that the motion is first detonated by artificially either deflecting the wheels or rocking the car, and provided also that there is a source of energy in the forward motion of the car. We have no means of accurately measuring the energy consumed, but know that compared with true shimmy it is extremely small, since it can be damped out easily by pressing the palm of the hand against the steering wheel or by otherwise applying friction. Also the slowing down of the drums is only appreciable when running with a very violent wobble at low speeds. Variation of Wobble. 1. If the drag link is removed a very violent wobble can be set up at about 150 cycles per minute the car rocking about an approximately horizontal axis above the centre of gravity thus:- | ||