gear ratio

gear ratio (plural gear ratios)

1. The ratio of the speeds of rotation of two gears, such as any pair that mesh and, especially, the initial and final gears in a gear train (whose relationship incorporates all the intermediate ones).
   • 1962 October, “Beyond the Channel: Italy: New series of E646 electrics”, in Modern Railways, page 276:

     Two versions exist of the new locomotives, for passenger and for freight work respectively, the technical difference between the two lying in the gearing of the bogies; the passenger locomotives, in light green and pearl grey livery, have a 25:64 gear ratio to haul 12-coach, 450-ton trains at 87 m.p.h. on the level, and the freight locomotives, in the famiiar Italian brown livery, have a 20:69 gear ratio enabling them to move 1,500-ton freights on the level at a consistent 53 m.p.h., with a maximum of 68 m.p.h.