In this paper it is shown that under certain assumptions the equations of motion derived on the basis of the linear creep theory can be solved analytically for a wheelset elastically suspended to a fixed mass and for two wheelsets elastically suspended to each other. In both instances an algebraic equation is derived for the critical speed of wheelset hunting.
The analysis leads to a clearer understanding of the stabilising functions performed by the various suspension elements and shows that the stabilising action of the axle-box suspension is a function of the so-called resultant constraining moment kr which is determined by the in-series action of the yaw constraint 2kb2 and the constraining moment of the lateral suspension 2kta2. The analysis is extended to bogies using direct coupling links between the wheelsets. The effect of viscous constraints on stability is analysed by means of eigenvalue programmes. Furthermore, the stabilising effect of the constraints acting between bogie and vehicle body obtained from the secondary suspension are discussed.
Design directives are outlined to optimise hunting stability and curving ability.