In this investigation, hunting stability of new-type independently rotating wheelset (IRW) which has negative tread conicity for improving curving performance is discussed. To this end, equations of motion of IRW with negative tread conicity are derived and used for the stability analysis. It is demonstrated that unstable hunting motion occurs in this type of wheelset and the hunting frequency decreases as the speed increases, which is totally different characteristics from those of the conventional wheelset. The cause of such unique vibration characteristics are investigated from an energy point of view, and the effect of coupling terms resulting from the wheel/rail creep forces on the stability of the hunting motion is discussed using the equations of motion in a block diagram form. Furthermore, hunting stability of one-axle IRW truck with negative tread conicity is discussed. It is presented that the truck hunting motion can be stabilized by adequate choices of primary suspensions.
