Abstract: A new problem is faced by a new developed loco- motive. Line test result of C0—C0 axle locomotive indicates that the locomotive has good lateral and curve negotiating performance, but its vertical vibration acceleration reaches a high level. However regular dynamic analysis shows that its dynamical performance should be very well. According to the special phenomena, detail dynamical calculation on this locomotive is carried out. The cause of the problem is found through fre-quency analysis. The special phenomenon of high vertical vibrate is caused by a new dynamics phenomenon that is ig-nored for a long time in railway vehicles researches. The new dynamics phenomenon is the longitudinal vibration of wheelset, and it is one of the important reasons of wheel treads abnormal wears, wheel treads spalling.

Key words: Acceleration, Dynamics, Locomotive, Radial bogie, Vertical vibration