The gear reduction in a right-angle worm drive is dependent on the number of threads or “starts” on the worm and the number of teeth on the mating worm wheel. If the worm has two starts and the mating worm wheel offers 50 teeth, the resulting gear ratio is 25:1 (50 / 2 = 25).

Calculating the gear ratio in a planetary gear reducer is less intuitive since it is dependent upon the amount of teeth of sunlight and band gears. The earth gears become idlers and don’t affect the gear ratio. The planetary gear ratio Planetary Wheel Drive equals the sum of the number of teeth on sunlight and ring equipment divided by the amount of teeth on sunlight gear. For example, a planetary arranged with a 12-tooth sun gear and 72-tooth ring gear has a gear ratio of 7:1 ([12 + 72]/12 = 7). Planetary gear models can perform ratios from about 3:1 to about 11:1. If more gear reduction is necessary, additional planetary stages may be used.

If a pinion equipment and its mating gear have the same amount of teeth, no reduction occurs and the apparatus ratio is 1:1. The gear is called an idler and its major function is to change the direction of rotation rather than decrease the speed or raise the torque.

Parallel shaft gearboxes many times contain multiple gear pieces thereby increasing the gear reduction. The full total gear reduction (ratio) is determined by multiplying each individual gear ratio from each equipment set stage. If a gearbox includes 3:1, 4:1 and 5:1 gear units, the full total ratio is 60:1 (3 x 4 x 5 = 60). Inside our example above, the 3,450 rpm electric engine would have its quickness reduced to 57.5 rpm by using a 60:1 gearbox. The 10 lb-in electric engine torque would be risen to 600 lb-in (before performance losses).