Analysis of the Shimmy Phenomenon

The shimmy phenomenon has been treated as a non-linear problem which is solved using the method of equivalent linearization and also with the aid of an analogue computer. Three non-linear elements are considered: the tyre characteristics, the Coulomb friction in the king-pin bearings, and clearance in the wheel bearings. The theory is substantiated by experiments with a test vehicle and a mechanical model. Two different kinds of shimmy appear to exist, one originating from the tyre elasticity and the other from the gyroscopic coupling. Results showing the effect of changing a number of important parameters on the shimmy phenomenon are presented.