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A gearbox, also known as a gear case or gear head, is a gear or a hydraulic system responsible for transmitting mechanical power from a prime mover (an engine or electric motor) into some form of useful output.
A gearbox is a set of gears for transmitting power from one rotating shaft to another. They are used in a wide range of industrial, automotive and home machinery application.
Gear heads are available in different sizes, capacities and speed ratios. Their main function is to convert the input provided by an electric motor into an output of lower RPM and higher torque.
Functions of a Gearbox
A gearbox is precisely bored to control gear and shaft alignment.
It is used as a housing/container for gear oil.
It is a metal casing for protecting gears and lubricant from water, dust and other contaminants.
There are a number of performance specifications which must be considered while choosing a gearbox for different industrial applications. Some of the important specifications are :
Gear ratio : The ratio may be specified as x : 1, where x is an integer.
Maximum input power
Maximum input speed
The Gearbox (Transmission)
Types of gearing:
Various types of gearing are used on a motor vehicle. The gearboxes employ one or more of the following:
1- Spur, teeth parallel to axis, used on sliding mesh.
2- Helical, teeth inclined to axis to form helix.
3- Double helical, two sets of opposing helical teeth.
4- Epicyclic or planetary, spur or helical gears rotating about centers which are not stationary.
Gear ratio (single gear train):
The gear ratio, or velocity ratio, between a pair of gear wheels is in inverse ratio to the number of teeth on each. Thus:
NB/NA = DA/DB= nA/nB
NB = NA (nA/nB)
NA= rev per min of gear A, nA = number of teeth on A
NB = rev per min of gear B, nB = number of teeth on B
DA = Diameter of gear A
DB = Diameter of gear B