On the surface, it may appear 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” specifically refers to the velocity of the rotary machine; the rotational velocity of the rotary machine is certainly “reduced” by dividing it by a equipment ratio higher than 1:1. A 
gear ratio greater than 1:1 is usually achieved whenever a smaller gear (reduced size) with fewer number of tooth meshes and drives a more substantial gear with greater quantity of teeth.
Gear reduction gets the opposite effect on torque. The rotary machine’s result torque is increased by multiplying the torque by the gear ratio, less some effectiveness losses.
While in many applications gear reduction reduces speed and raises torque, in additional applications gear decrease is used to improve velocity and reduce torque. Generators in wind turbines use gear reduction in this fashion to convert a relatively slow turbine blade quickness to a high speed capable of producing electricity. These applications use gearboxes that are assembled opposite of these in applications that decrease acceleration and increase torque.
How is gear reduction achieved? Many reducer types are capable of attaining gear reduction including, but not limited to, parallel shaft, planetary and right-angle worm gearboxes. In parallel shaft gearboxes (or reducers), a pinion equipment with a certain number of teeth meshes and drives a larger gear with a greater number of teeth. The “decrease” or gear ratio is calculated by dividing the number of the teeth on the large gear by the number of teeth on the tiny gear. For instance, if an electric motor drives a 13-tooth pinion gear that meshes with a 65-tooth gear, a reduction of 5:1 is achieved (65 / 13 = 5). If the electric motor speed is definitely 3,450 rpm, the gearbox reduces this velocity by five times to 690 rpm. If the electric motor torque is certainly 10 lb-in, the gearbox raises this torque by one factor of five to 50 lb-in (before subtracting out gearbox performance losses).
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 gear set stage. If a gearbox consists of 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 swiftness 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).
If a pinion equipment and its mating equipment have the same quantity of teeth, no decrease occurs and the apparatus ratio is 1:1. The apparatus is called an idler and its own principal function is to change the path of rotation instead of decrease the speed or boost the torque.
Calculating the gear ratio in a planetary equipment reducer is less intuitive as it is dependent on the amount of teeth of the sun and ring 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 amount of teeth on the sun gear. For instance, a planetary arranged with a 12-tooth sun gear and 72-tooth ring gear has a equipment 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 needed, additional planetary stages may be used.
The gear decrease in a right-angle worm drive would depend 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).
Whenever a rotary machine such as for example an engine or electric engine cannot provide the desired output swiftness or torque, a equipment reducer may provide a good solution. Parallel shaft, planetary, right-position worm drives are normal gearbox types for achieving gear reduction.