Interface - The Journal of Wheel/Rail Interaction

WHEEL NOISE

Tuning Mass Dampers to Reduce Squeal (continued)

At the RET, the following steps were taken:

— The space between the wheel and bogie and the nearest component was analyzed to ensure that there was enough space to mount absorbers on the wheel.

— Noise measurements were conducted in curves, where noise was most disturbing, to determine the frequencies and to verify that they were emitted from the wheel.

— Laboratory tests were done on the wheel and bogie to determine the structural resonance of the wheel (resilient or monoblock).

— Field measurements and laboratory tests were compared to identify similarities and to verify that the radiating noise was not coming from another source.

— A (bolt-on type) prototype system was designed and lab tested for frequency damping and noise reduction.

— Finite element analysis was conducted to ensure that modifications associated with the tuned mass damper did not negatively impact the performance of the manufactured wheel.

— Analysis was done to define whether it was necessary to equip one bogie or an entire tram with sound-absorbing dampers.

— Follow-up wayside or onboard sound measurements were made (at the same locations) to verify that the dampers performed as expected.

After a test/development program on an urban rail system is complete, the tram system's engineers must decide whether to equip a limited number of vehicles with mass dampers or to equip the entire fleet. The RET elected to equip the entire fleet of 60 (three-bogie) vehicles. The retrofit work was done as tyres on the vehicles were replaced over a one-year period.

While the complexity of wheel/rail interaction makes it difficult to predict results on urban rail systems, in general, mass dampers have been effectively implemented on tram systems in Amsterdam, Stuttgart, Orléans, Bielefeld, Berlin and on several of the Swiss Mountain Railways. Wayside measurements taken on the Rotterdam RET indicate that noise levels on the CITADIS™ vehicles equipped with tuned mass dampers were reduced by 15 - 35 dB(A).

Paul Kampfraath is Managing Director of KAMPA

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