Many bevel- gear units are employed in traveling drives of large industrial bridge cranes all over the world, as they form
compact packages with couplings, brakes and electric motors other gear units do not allow for. In a number of drives,
frequent failures of the bevel gear pose a difficult problem for maintenance, and have raised unclosed discussions about
the necessary service or application factor. According to some standards, these drives require gear unit service factors as
high as 3.0. This paper focuses on the origin of the troubles, with an insight on the dynamics of the gear train. Attention is
also given, in such failures, to the influence of variable-speed controllers of electric motors. The theoretical analysis is
backed by real industrial case studies, taken from the author’s recent experiences.