The gear decrease in a right-angle worm drive is dependent 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 begins and the mating worm wheel provides 50 tooth, 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 on the number of teeth of the sun and ring gears. The earth gears become idlers , nor affect the gear ratio. The planetary gear ratio equals the sum of the number of teeth on sunlight and ring gear divided by the number of teeth on the sun gear. For example, 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 pieces can achieve ratios from about 3:1 to about 11:1. If more gear reduction is necessary, additional planetary stages can be used.
If a pinion equipment and its mating equipment have the same quantity of teeth, no reduction occurs and the gear ratio is 1:1. The gear is called an idler and its principal function is to improve the direction 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 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 models, the total ratio is 60:1 (3 x 4 x 5 = 60). Inside our example above, the 3,450 rpm electric motor would have its swiftness decreased to 57.5 rpm by using a 60:1 gearbox. The 10 lb-in electric engine torque would be increased to 600 lb-in (before performance Planetary Wheel Drive losses).