The gear reduction 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 has 50 teeth, the resulting gear 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 amount of teeth of the sun and ring gears. The earth gears become idlers , nor affect the apparatus ratio. The planetary equipment ratio equals the sum of the number 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 gear ratio of 7:1 ([12 + 72]/12 = 7). Planetary gear units 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 gear have the same number of teeth, no decrease occurs and the gear ratio is 1:1. The gear is named an idler and its major function is to improve the path of rotation rather than reduce the speed or Planetary Wheel Drive increase the torque.
Parallel shaft gearboxes often contain multiple gear units thereby increasing the gear reduction. The total gear reduction (ratio) is determined by multiplying each individual gear ratio from each gear arranged stage. If a gearbox includes 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 rate reduced to 57.5 rpm by utilizing a 60:1 gearbox. The 10 lb-in electric motor torque would be risen to 600 lb-in (before performance losses).