Elastokinematic Analysis of Compound Crank Axle Suspensions

In the present paper a theoretical model for the analysis of compound crank axle is presented. It is based on the set of equilibrium, constitutive and congruence equations of the axle; to this aim, the cross-member is described by its stiffness matrix, the longitudinal arms are assumed as rigid and the bearing which connects the axle to the body as ideal. For this configuration, a closed form solution for the elastokinematic analysis is obtained in the small displacements field, for the pure roll condition. This can be summarized by the knowledge of the position, in a 3D space, of the instantaneous axis of rotation of each wheel; it is shown how the instantaneous axis of rotation is determined by both the axle geometry and the stiffness properties of the cross member. An iterative procedure has been also developed for the large displacement analysis. Results, in terms of camber and toe angle alteration, are discussed in comparison with those obtained by finite element analyses.