# planetary wheel drive

The gear reduction in a right-angle worm drive would depend on the amount of threads or “starts” on the worm and the amount of teeth on the Planetary Wheel Drive mating worm wheel. If the worm has two begins and the mating worm wheel has 50 tooth, 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 band gears. The planet gears act as idlers and don’t affect the gear ratio. The planetary equipment ratio equals the sum of the number of teeth on sunlight and ring equipment divided by the number of teeth on sunlight gear. For instance, a planetary established with a 12-tooth sun gear and 72-tooth ring gear has 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 gear and its mating gear have the same number of teeth, no decrease occurs and the gear ratio is 1:1. The apparatus is called an idler and its primary 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 units thereby increasing the gear reduction. The total gear decrease (ratio) depends upon multiplying each individual equipment ratio from each equipment established stage. If a gearbox includes 3:1, 4:1 and 5:1 gear models, 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 acceleration decreased to 57.5 rpm by utilizing a 60:1 gearbox. The 10 lb-in electric electric motor torque would be risen to 600 lb-in (before efficiency losses).