On the surface, it may seem that gears are being “reduced” in quantity or size, which is partially true. When a rotary machine such as for example an engine or electrical motor needs the output speed decreased and/or torque improved, gears are commonly used to accomplish the required result. Gear “reduction” particularly refers to the quickness of the rotary machine; the rotational rate of the rotary machine is usually “decreased” by dividing it by a gear ratio greater than 1:1. A gear ratio higher than 1:1 is usually achieved whenever a smaller gear (decreased size) with fewer number of tooth meshes and drives a more substantial gear with greater amount of teeth.
Gear reduction has the opposite influence on torque. The rotary machine’s output torque is improved by multiplying the torque by the gear ratio, less some efficiency losses.
While in many applications gear reduction reduces speed and boosts torque, in various other applications gear reduction is used to increase velocity and reduce torque. Generators in wind generators use gear decrease in this manner to convert a relatively slow turbine blade quickness to a high speed capable of generating electricity. These applications make use of gearboxes that are assembled reverse of these in applications that decrease quickness and increase torque.
How is gear decrease achieved? Many reducer types can handle attaining gear decrease including, but not limited by, parallel shaft, planetary and right-position worm gearboxes. In parallel shaft gearboxes (or reducers), a pinion gear with a specific number of the teeth meshes and drives a larger gear with a lot more teeth. The “decrease” or equipment ratio is usually calculated by dividing the amount of tooth on the large gear by the amount of teeth on the tiny gear. For example, if a power motor drives a 13-tooth pinion equipment that meshes with a 65-tooth gear, a reduction of 5:1 is certainly achieved (65 / 13 = 5). If the electrical motor speed can be 3,450 rpm, the gearbox reduces this swiftness by five 
occasions to 690 rpm. If the engine torque can be 10 lb-in, the gearbox increases this torque by one factor of five to 50 lb-in (before subtracting out gearbox efficiency losses).
Parallel shaft gearboxes often contain multiple gear pieces thereby increasing the gear reduction. The full total gear decrease (ratio) depends upon multiplying each individual gear ratio from each gear arranged stage. If a gearbox contains 3:1, 4:1 and 5:1 gear units, 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 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 efficiency losses).
If a pinion equipment and its mating gear have the same quantity of teeth, no reduction occurs and the gear ratio is 1:1. The apparatus is named an idler and its own main function is to change the direction of rotation rather than decrease the speed or raise the torque.
Calculating the apparatus ratio in a planetary equipment reducer is much less intuitive as it is dependent upon the number of teeth of the sun and ring gears. The planet gears become idlers and do not affect the apparatus ratio. The planetary gear ratio equals the sum of the number of teeth on the sun and ring gear divided by the number of teeth on the sun 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 pieces can perform ratios from about 3:1 to about 11:1. If more gear reduction is necessary, additional planetary stages may be used.
The gear reduction in a right-angle worm drive would depend 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 begins and the mating worm wheel offers 50 teeth, the resulting gear ratio is 25:1 (50 / 2 = 25).
When a rotary machine such as an engine or electric engine cannot supply the desired output velocity or torque, a equipment reducer may provide a great choice. Parallel shaft, planetary, right-position worm drives are normal gearbox types for achieving gear reduction.