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 document detailing the causes and types of oscillation and wobbling in a vehicle.
| Identifier | ExFiles\Box 170\3\ img029 | |
| Date | 5th June 1935 guessed | |
| -2- controlling oscillation. 2. An oscillation of a second part out of phase with the first. This need not be very close to the natural frequency of the second part, but if greatly different the oscillation will not build up. 3. Some instantaneous form of disturbance which will serve to "detonate" the oscillation. 4. An external source of energy, in these cases the forward motion of the car. For example : 1. In shimmy the first oscillation is tramp of the wheels. The second is wobbling of the wheels about the kingpins. The detonation is generally the wheel unbalance, or eccentricity, but, with perfectly balanced wheels may be a single bump in the road. The source of energy is forward motion of the car. Once the cycle is started, the wheel wobble feed back energy into the tramp, and itself derives energy, through its tires from the forward motion. The oscillation builds up to a maximum amplitude determined by the damping. 2. In "wobble" as commonly encountered the controlling oscillation is the rocking of the car about an inclined axis passing roughly through the lower edge of the windshield and through the centre of the rear axle. The natural frequency of the car about this axis is, in the cases examined, 360 to 380 cycles per minute and this is the approximate frequency of the wobble. The secondary oscillation is wobbling of the wheels, which through tyre characteristics, feeds energy into itself and also into the rocking of the car. The detonation may consist of an isolated road bum, a snatch at the steering wheel, or even such small effects as run-out of tires. Other forms of wobble have been observed and are described later. For each form we have a different rocking axis of the car and a different rocking frequency, and the wheel motion must in some way be "tuned" to more or less match the rocking frequency of the car. | ||