Abstract
The historical background of the automobile shimmy problem is outlined. The behaviour of a suspension and steering system is predicted using a one-term harmonic approximation to the solution of the simplified equations of motion of the system. These equations include the effects of the nonlinear variation of the tyre aligning torque with applied slip angle and of the relaxation properties of the tyre. The unstable frequency regions of the steering system are predicted with and without coupling of the steering and vertical suspension motions. An estimate of the level of damping required to suppress the shimmy motion is made.
An apparatus for the determination of the relevant tyre properties is described. The experimental results obtained for the behaviour of a laboratory suspension unit are compared with those predicted theoretically and the agreement is found to be reasonable.
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