Presentation about groan noise in braking systems

A relatively standard brake system used on a metro vehicle showed abnormal noise and vibrations in service. Beyond passenger’s annoyance, this led to unacceptable failures in service, rising cracks in the brake calliper levers and a premature wear of brake pads. Although no similar problems appeared during test benches performed by the manufacturer before and after the problem was discovered, a reinforced version of the levers solved the structural problem leaving nevertheless unchanged high noise and vibration effects during braking. Several pads were tested without success. The paper shows how the problem was solved by means of a dynamic analysis of all the components involved (wheelset, brake unit, bogie frame) and a following minor redesign of a component. The impact on the existing fleet in terms of retrofit costs and times in described as well, showing that the proposed solutions are very effective and affordable.