The gear decrease 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 starts and the mating worm wheel provides 50 the teeth, the resulting equipment ratio is 25:1 (50 / 2 = 25).
Calculating the apparatus ratio in a planetary equipment reducer is less intuitive as it is dependent upon the amount of teeth of sunlight and ring gears. The planet gears become idlers , nor affect the apparatus ratio. The planetary equipment ratio equals the sum of the number of teeth on the sun and ring equipment divided by the amount of teeth on the sun gear. For example, a planetary arranged with a 12-tooth sun gear and 72-tooth ring gear includes a gear 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 can be used.
If a pinion equipment and its mating equipment have the same quantity of teeth, no reduction occurs and the apparatus ratio is 1:1. The apparatus is called an idler and its own principal function is to change the direction of rotation rather than decrease the speed or boost the torque.
Parallel shaft gearboxes many times contain multiple gear sets thereby increasing the gear reduction. The full total gear reduction (ratio) is determined by multiplying each individual gear ratio from each equipment arranged stage. If a gearbox includes 3:1, 4:1 and 5:1 gear pieces, 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 quickness reduced to 57.5 rpm by Planetary Wheel Drive utilizing a 60:1 gearbox. The 10 lb-in electric motor torque would be increased to 600 lb-in (before efficiency losses).