A method of measuring transmission error in spur gears of 1:1 ratio

The transmission error of a pair of spur gears is detected by an optical method and recorded continuously as a function of time. Measurement of the alternating component of the error is repeatable within ?5 ? 10-5 in., and of the mean value within ?1 ? 10-4 in., at base circle radius, at any speed in the range 0-6000 rev min-1 and at any load within the capacity of the gears. Records are taken on photographic paper wrapped round a drum which rotates with one of the gears being tested. In this way the wavelength of record per cycle of tooth-engagement is made independent of speed and comparison of static and dynamic behaviour is facilitated. The method of measurement is applicable only to a pair of gears with the same number of teeth.