The gear reduction in a right-angle worm drive would depend 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 starts and the mating worm wheel offers 50 tooth, the resulting equipment ratio is 25:1 (50 / 2 = 25).
Calculating the apparatus ratio in a planetary gear reducer is less intuitive as it is dependent upon the amount of teeth of sunlight and ring gears. The earth gears become idlers , nor affect the gear ratio. The planetary equipment 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 example, a planetary established 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 gear reduction is necessary, additional planetary stages may be used.
If a pinion gear and its mating equipment have the same amount of teeth, no reduction occurs and the apparatus ratio is 1:1. The apparatus is named an idler and its main function is to change the direction of rotation instead of reduce the speed or raise the torque.
Parallel shaft gearboxes often contain multiple gear pieces thereby increasing the gear reduction. The full total gear reduction (ratio) depends upon multiplying each individual gear ratio from each equipment established stage. If a gearbox contains 3:1, 4:1 and 5:1 gear units, the total ratio is 60:1 (3 x 4 x 5 = 60). Inside our example above, the 3,450 rpm electric engine would have its acceleration decreased to 57.5 rpm by Planetary Wheel Drive utilizing a 60:1 gearbox. The 10 lb-in electric engine torque would be risen to 600 lb-in (before effectiveness losses).