Electric and diesel locomotives’ top speeds are governed by gear ratios and safe operations, like this Union Pacific westbound near Franklin Grove, Ill.
Brian Schmidt
Q What determines the theoretical top speed of a diesel locomotive? Is it the gear ratio? What other factors enter in? – Mike Pedersen, North Berwick, Maine
A The maximum speed is a function of the gear ratio on a diesel or electric locomotive. The reason is that the traction motor armature has a maximum allowable revolutions per minute rating, above which mechanical stresses could damage or destroy it.
Since the armature is connected to the wheels by a fixed gear ratio, the maximum revolutions per minute can be translated to a maximum speed in miles per hour, with a factor of safety added, of course. – Walter Rosenberger, research and testing operations engineer, Norfolk Southern
