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

Calculating the gear ratio in a planetary gear reducer is much less intuitive since it is dependent upon the number of teeth of sunlight and ring gears. The planet gears become idlers and don’t affect the apparatus ratio. The planetary equipment ratio equals the sum of the number of teeth on sunlight and ring equipment divided by the number of teeth on the sun gear. For instance, a planetary arranged with a 12-tooth sun gear and 72-tooth ring gear has a equipment 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 needed, additional planetary stages may be used.

If a pinion equipment and its mating gear have the same quantity of teeth, no reduction occurs and the gear ratio is 1:1. The gear is named an idler and its primary function is to improve the direction of rotation rather than decrease the speed or boost the torque.

Parallel shaft gearboxes often contain multiple gear models thereby increasing the apparatus reduction. The total gear reduction (ratio) depends upon multiplying each individual equipment ratio from each equipment set stage. If a gearbox contains 3:1, 4:1 and 5:1 gear Planetary Wheel Drive pieces, the full total ratio is 60:1 (3 x 4 x 5 = 60). In our example above, the 3,450 rpm electric engine would have its quickness reduced 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).