Abstract
The oscillation of castored wheels is familiar in many situations, e.g. the steered wheels of motor cars, motorcycles, aircraft landing gear, caravans and trailers. The subject is well documented, with explanations usually in terms of tyre behaviour, yet none of these theories can explain the oscillation of the simplest castor—that on a tea trolley, which has no tyre. Nor are these theories applicable to the case of motorcycle stability. It seems that tyre deformation is but one instance of a more general property causing instability, namely the ability of the contact patch to move laterally relative to the steering axis. A simple theory covering these cases is presented here, and an understanding of the mechanism is possible from an energy diagram.
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