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How Do Gearboxes Work

Aug 15, 2017

                                                         How do Gearboxes Work?

All gearboxes work in a similar fashion. The directions the gears rotate are dependent on the input direction and orientation of 

the gears. For example, if the initial gear is rotating in a clockwise direction, the gear it engages will rotate counterclockwise. 

This continues down the line for multiple gears. The combination of different size gears and the number of teeth on each gear 

plays a significant role in the output torque and speed of the shaft. High gear ratios allow for more output torque and lower 

speeds, while lower gear ratios allow for higher output speed and less output torque. 

A planetary gearbox works relatively the same. A planetary gearbox system is constructed with three main components: a 

central sun gear, a planet carrier (carrying one or more planet gears) and an annulus (an outer ring). The central sun gear is 

orbited by planet gears (of the same size) mounted to the planet carrier. The planet gears are meshed with the sun gear 

while the outer rings teeth mesh with the planet gears. There are several configurations for a gearbox system. Typical 

configurations consist of three components: the input, the output and one stationary component. For example: one possible 

configuration is the sun gear as the input, the annulus as the output and the planet carrier remaining stationary. In this 

configuration, the input shaft rotates the sun gear, the planet gears rotate on their own axes, simultaneously applying a torque 

to the rotating planet carrier that in turn applies torque to the output shaft (which in this case is the annulus). The rate at which 

the gears rotate (gear ratio) is determined by the number of teeth in each gear. The torque (power output) is determined by 

both the number of teeth and by which component in the planetary system is stationary.

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