The gear decrease in a right-angle worm drive would depend on the amount 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 the teeth, the resulting gear ratio is 25:1 (50 / 2 = 25).
Calculating the gear ratio in a planetary equipment reducer is less intuitive as it is dependent upon the number of teeth of sunlight and ring gears. The earth gears act as idlers , nor affect the apparatus 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 set with a 12-tooth sun gear and 72-tooth ring gear Planetary Wheel Drive includes a equipment ratio of 7:1 ([12 + 72]/12 = 7). Planetary gear pieces can achieve ratios from about 3:1 to about 11:1. If more gear reduction is needed, additional planetary stages may be used.
If a pinion gear 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 main function is to change the path of rotation rather than reduce the speed or raise the torque.
Parallel shaft gearboxes often contain multiple gear pieces thereby increasing the gear reduction. The total gear decrease (ratio) is determined by multiplying each individual gear ratio from each gear established stage. If a gearbox includes 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 engine would have its velocity reduced to 57.5 rpm by utilizing a 60:1 gearbox. The 10 lb-in electric electric motor torque would be increased to 600 lb-in (before effectiveness losses).