The purpose of this work is to investigate the possible causes of wheel squeal on Roslagsbanan, a

narrow gauge (891mm) suburban railway system in Stockholm, Sweden. Simulation of the dynamic behaviour of vehicles negotiating curves was carried out by means of the Swedish multibody simulation software GENSYS [1].

Wheel squeal may arise due to insufficient radial steering capability of the vehicles in curves causing too high levels of creep (relative sliding) in the wheel/rail-contact. Based on this theory, an advanced model of the creep-creep force relation was introduced. In this model the creep force decreases after creep reaches a certain level, called critical creep. It is believed that wheel squeal occurs after the creep level exceeded the critical creep value.

Measured rail profiles of the curve together with measured wheel profiles were used as wheel/rail geometry input data. Other interesting parameters for the simulations, such as friction coefficient, primary suspension stiffness and damping, vehicle speed, braking/acceleration were varied and their effects on the outcome were tested.

Worn wheels on newly grinded and worn rails under dry conditions are most likely to generate curve squeal. We believe the long term solution for Roslagsbanan is to grind the rail profiles into a shape more similar to the 50E3 with inclination 1/40. This will give a more even wheel wear over the whole wheel surface. However, curves below ca 300 m cannot be negotiated without wheel squeal, why all

curves on the track tighter than ca 300 m have to be lubricated.