The gear reduction in a right-angle worm drive is dependent on the number of threads or “starts” on the worm and the number of teeth on the mating worm wheel. If the worm has two begins and the mating worm wheel provides 50 teeth, the resulting equipment ratio is 25:1 (50 / 2 = 25).

Calculating the apparatus ratio in a planetary gear reducer is much less intuitive as it is dependent upon the number of teeth of sunlight and ring gears. The planet gears act as idlers and don’t affect the gear ratio. The planetary equipment ratio equals the sum of the amount of teeth on the sun and ring gear divided by the number of teeth on sunlight gear. For instance, a planetary established with a 12-tooth sun gear and 72-tooth ring gear has a gear ratio of 7:1 ([12 + 72]/12 = 7). Planetary gear sets can achieve ratios from about 3:1 to about 11:1. If more equipment reduction is necessary, additional planetary stages may be used.

If a pinion equipment and its mating gear have the same number of teeth, no decrease occurs and the apparatus ratio is 1:1. The gear is named an idler and its major function is to change the path of rotation instead of Planetary Wheel Drive reduce the speed or boost the torque.

Parallel shaft gearboxes many times contain multiple gear models thereby increasing the apparatus reduction. The total gear decrease (ratio) is determined by multiplying each individual gear ratio from each equipment arranged stage. If a gearbox consists of 3:1, 4:1 and 5:1 gear pieces, the full total ratio is 60:1 (3 x 4 x 5 = 60). In our example above, the 3,450 rpm electric electric motor would have its quickness decreased to 57.5 rpm by utilizing a 60:1 gearbox. The 10 lb-in electric engine torque would be increased to 600 lb-in (before effectiveness losses).