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 starts and the mating worm wheel offers 50 tooth, the resulting gear ratio is 25:1 (50 / 2 = 25).
Calculating the gear ratio in a planetary equipment reducer is less intuitive since it is dependent on the number of teeth of the sun and ring gears. The earth gears act as idlers and do not affect the apparatus ratio. The planetary gear ratio equals the sum of the amount of teeth on sunlight 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 equipment ratio of 7:1 ([12 + 72]/12 = 7). Planetary gear sets can perform 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 number of teeth, no decrease occurs and the apparatus ratio is 1:1. The apparatus is called an idler and its own main function is to improve the path of rotation rather than reduce the speed or boost the torque.
Parallel shaft gearboxes often contain multiple gear units Planetary Wheel Drive thereby increasing the apparatus reduction. The full total gear decrease (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 models, the total ratio is 60:1 (3 x 4 x 5 = 60). Inside our example above, the 3,450 rpm electric electric motor would have its velocity decreased to 57.5 rpm by utilizing a 60:1 gearbox. The 10 lb-in electric motor torque would be increased to 600 lb-in (before performance losses).