WHEEL PROFILING: Emotec has retrofitted a lathing capability to a tram wheel profiling machine, which along with a modern computer control system has reduced the time taken to reprofile the four wheels on a bogie from a day to 2 h.

Zürich transport operator VBZ called in Swiss engineering firm Emotec as part of its preparations for the introduction of low-floor trams which have smaller wheels requiring more frequent reprofiling.

The Oerlikon depot had a wheel profiling machine supplied by Kellenberger in 1991, but this used a form grinding wheel which could be time-consuming when compensating for heavy wear and required changing to accommodate different vehicle wheel diameters. After 20 years the control unit was also becoming expensive to maintain.

Turning tram wheels on a lathe prior to grinding has become viable with the advent of specialised tools and powerful computer control systems, and Emotec found this capability could be added to the existing machine. As well as much shorter machining times, this provides the ability to reprofile the flange and the back of the wheel. The control system also provides the option to machine different tyre profiles without adapting the tools.