On the surface, it could 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 reduced and/or torque increased, gears are commonly used to accomplish the required result. Gear “reduction” particularly refers to the velocity of the rotary machine; the rotational swiftness of the rotary machine is “decreased” by dividing it by a gear ratio higher than 1:1. A gear ratio higher than 1:1 is definitely achieved when a smaller gear (decreased size) with fewer quantity of teeth meshes and drives a more substantial gear with greater amount of teeth.
Gear reduction has the opposite effect on torque. The rotary machine’s output torque is improved by multiplying the torque by the apparatus ratio, less some performance losses.
While in many applications gear reduction reduces speed and boosts torque, in other applications gear decrease is used to increase swiftness and reduce torque. Generators in wind generators use gear reduction in this manner to convert a relatively slow turbine blade swiftness to a higher speed capable of producing electricity. These applications make use of gearboxes that are assembled opposing of these in applications that reduce acceleration and increase torque.
How is gear reduction achieved? Many reducer types can handle attaining gear reduction including, but not limited by, parallel shaft, planetary and right-position worm gearboxes. In parallel shaft gearboxes (or reducers), a pinion equipment with a particular number of teeth meshes and drives a more substantial gear with a greater number of teeth. The “decrease” or equipment ratio can be calculated by dividing the number of the teeth on the large equipment by the amount of teeth on the small gear. For instance, if a power motor drives a 13-tooth pinion equipment that meshes with a 65-tooth gear, a reduced amount of 5:1 is usually achieved (65 / 13 = 5). If the electric motor speed can be 3,450 rpm, the gearbox reduces this rate by five moments to 690 rpm. If the engine torque is definitely 10 lb-in, the gearbox increases this torque by one factor of five to 50 lb-in (before subtracting out gearbox performance losses).
Parallel shaft gearboxes often contain multiple gear sets thereby increasing the apparatus reduction. The total gear decrease (ratio) is determined by multiplying each individual gear ratio from each gear arranged stage. If a gearbox consists of 3:1, 4:1 and 5:1 gear pieces, the 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 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 number of teeth, no decrease occurs and the gear ratio is 1:1. The gear is called an idler and its principal function is to improve the path of rotation rather than reduce the speed or boost the torque.
Calculating the apparatus ratio in a planetary gear reducer is less intuitive since it is dependent on the amount of teeth of sunlight and ring gears. The earth gears become idlers and don’t affect the apparatus ratio. The planetary equipment ratio equals the sum of the number of teeth on the sun and ring equipment divided by the number of teeth on sunlight gear. For instance, a planetary set with a 12-tooth sun gear and 72-tooth ring gear includes a equipment ratio of 7:1 ([12 + 72]/12 = 7). Planetary gear sets 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 starts and the mating worm wheel has 50 the teeth, the resulting gear ratio is 25:1 (50 / 2 = 25).
Whenever a rotary machine such as an engine or electric engine cannot supply the desired output quickness or torque, a gear reducer may provide a great choice. Parallel shaft, planetary, right-angle worm drives are normal gearbox types for achieving gear reduction.