Gearboxes

Gearbox Casing Functions	Buyer's Guide	Classification of Gearboxes
Gearing Arrangement	Types of Gearboxes

Gear box is an essential equipment in a gear assembly. Gear Box is also known as Gear head, Gear reducer and Speed reducer. The fundamental principle of a gearbox is to transmit the cause of mechanical rotation between two shafts. In this order, there is a structural support present in between the two shafts. Generally, gearboxes are kept inside the casings. This helps the gearboxes in their structural support, provides protection and ensures in doing safe functioning. Normally, the gearboxes are designed in reducing the speed, but sometimes, a gearbox may be designed for speed enhancing duties. The shafts inside the gearboxes are placed for the purpose of accepting and delivering the machinery rotation. This machinery rotation (torque) is achieved in the form of splines that should be suitable to connect or join to another unit. The capacity of thrusting outward of the shafts will have been limited from the casing. The mechanical rotation which is generated by the engine is consumed through the gearbox. This in turn, is being converted into a force at the road surface. To accelerate the vehicle, the force which is being applied can be calculated as follows:

Applied force = Torque at the wheel * radius of the road wheel (including the tyre)

Types of Gearboxes
There are five types of gear boxes. These five types of gear boxes are as follows:

Automatic Gearboxes
For most of the Automatic Gearboxes, there is a selected set of possible gear ranges. The set selection often have a parking pawl features. This feature closes the output shaft of the transmission. Since 1950's, most of the cars which have sold in USA, equipped with Automatic gearboxes. But, in rest of the world, this trend has not been followed.
Semiautomatic Gearboxes
The semiautomatic Gearboxes are also known as clutch less manual transmissions or automated manual transmissions, e-gears, or paddle shift gearboxes. In semiautomatic gear boxes, there are sensors, processors and actuators. These things help in shifting the gears on the command of the drivers.
Manual Gearboxes
The history of manual gearboxes is very old. The traditional clutches are used in such kind of gearboxes. Each time, these gears are selected by electrically controlled motors. After the selection, these gears detach the clutches and the gears are shifted. Once the clutch gets free, it can be used again.
Marine Gearboxes
The drive is directly connected to the propeller in a traditional Marine gearbox. Marine gearboxes fulfill a multiple number of marine related purposes. To meet each and every purpose, these marine gears do also have a large number of different configurations and installation processes.
Shaft Mounted Gearboxes
Shaft mounted gearboxes are very closely and firmly design in size. These gears are directly mounted onto the driven shafts. This mounting process helps these gears in avoiding the use of coupling and base. In Shaft Mounted gears, there is no problem in the adjustment. The boxes of the gears are suitable for both forward and reverse motion.
Gear Motors
Gears motors are such type of motors which have a large reduction system. The gearbox is pertained into the motor. This type of integral arrangement is done in order to increase the mechanical rotational speed of the motor. But simultaneously, this arrangement reduces the output speed.

Functions of the Gearbox Casing

It provides structural support for the shaft bearings. This in turn helps in gear loading.
It transfers the reaction of mechanical rotation (torque) to the other supporting structure of the gearbox or drive elements.
It prevents the lubricant from spreading and also prevents the unwanted particals from coming inside.
It provides the safety provision and reduce the noise intensity.
It also reduces the amount of heat that generates due to the internal friction.
It increases the external and visual qualities of the gearbox.

To obtain the support-rigidity, safety and reliability in operations, the casings must be located, fitted and fastened properly to their foundations. Proper provision of ventilation should be ensured in these casings for removing out the heat which generates during the operations.

Buyers Guide (Selection Process of Gearboxes)
Before setting out the buying decision of a gearbox, the most important thing is to ensure about the requirements of the gearbox. The best selection of a gearbox gives the best outputs in fulfilling the requirements of the buyers. This kind of successful selection can be achieved by matching the requirements of the power transmission system with a particular range of gearboxes offered by the manufacturers. So, it is advisable for the buyers to have some knowledge regarding the system and available hardwares in the market. A buyers may do the following things before buying a gearbox:

Collect informations about the system.
Review those factors that influence the buying decision.
Prepare the limit of acceptance and ability of these factors.
Collect informations from different manufacturers for acquiring knowledge regarding gearboxes. The entire selection process of a gearbox can be enlisted through the following flow chart:

Classification of Gearboxes
Today, it is possible to obtain such kind of gearboxes which consist the characteristics of two or more than two kinds of different gearboxes. These kinds of gearboxes are called compound gearboxes. The speed ratio in such kinds of gearboxes is high because the respective speed ratios of each individual gear box within it are compounded. The classification of gearboxes is done on the basic of shaft orientation or speed ratio.

Gearing Arrangement for Gearbox
In the gearing arrangement for a gearbox, the various components are: cycloidal, worm, bevel, planetary, spur and helical.

Bevel gear is actually a gear wheel that is meshed with another bevel gear in such a way so that the shafts can form an angle, which is less than 180�.
Helical gears join shafts that are parallel. The involute teeth of the helical gears are cut at an angle to the axis of the rotation. If there are two mating helical gears in the gearing arrangement of the gearbox, then they must have equal helix angle but opposite hands.
In case of spur gears, they connect parallel shafts. They have curled teeth which are parallel to the shaft and may have either external or internal teeth.
The planetary gears may present in total number of two and they are present either on or inside a large gear. The intense gear ratio is possible due to these gears. When the intention is to turn the input in the same direction of the output, then these gears are used. Planetary gears can be designed along with a set of planetary cones or with a gear set.
Cycloidal gears are used in pair form and they are arranged in such a way so that the angle formed by them should be equal to180�. The reason behind the formation of 180� is to provide balance to the load and these gears are driven by many crank shafts. Multiple shafts are present for sharing the load and to enhance the twisting state firmness.
The worm gears are wrapped around a central axle and these have slant plane. This kind of gear consists one or more than one teeth and these teeth are present in the screwed thread form.