The gear reduction in a right-angle worm drive is dependent on the amount of threads or “starts” on the worm and the amount of teeth on the mating worm wheel. If the worm has two begins 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 equipment reducer is much less intuitive since it is dependent upon the amount of teeth of sunlight and band gears. The earth gears act as idlers , nor affect the gear ratio. The planetary gear ratio equals the sum of the amount of teeth on sunlight and ring gear divided by the amount of teeth on the sun gear. For instance, a planetary set with a 12-tooth sun gear and 72-tooth ring gear has a equipment ratio of 7:1 ([12 + 72]/12 = 7). Planetary gear units can perform ratios from about 3:1 to about 11:1. If more equipment reduction is necessary, additional planetary stages may be used.
If a pinion gear and its mating gear have the same number of teeth, no decrease occurs and the gear ratio is 1:1. The gear is called an idler and its own main function is to change the path of rotation instead of decrease the speed or increase the torque.
Parallel shaft gearboxes many times contain multiple gear models thereby increasing the gear reduction. The full total gear reduction (ratio) is determined by multiplying each individual equipment ratio from each equipment established stage. If a gearbox Planetary Wheel Drive contains 3:1, 4:1 and 5:1 gear sets, the total ratio is 60:1 (3 x 4 x 5 = 60). In our example above, the 3,450 rpm 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 performance losses).