Gear Box

Spur Gears

Tooth profiles is straight and parallel to the shaft axes. The most widely used gears in machines. Manufacturing of these gears is less complicated than the other gear tooth profiles. When the two gears are meshed, then the larger one called “Gear” and the smaller one is called “Pinion”.

Helical Gears

This gears also used for the parallel shaft connection, but the gear tooth is inclined as helices.  These helical gears can be available in both left-hand helix right-hand helix. Since the teeth are at helical angle, the length and contact area is more and thereby can take more load.

Bevel Gears

Bevel gears are used if the shafts axis is intersected. Tooth profile is on its conical surface.

Worm Gears

Worm and worm wheel is used where speed reduction ratio is high. Example 40 rounds of worm will give 1 round of worm wheel 40:1.  It can take very high torque compared to all other types of gears. The drive in this system is Irreversible. However if the helix angle on worm and worm wheel is less, then the drive can be reversed. In this case the speed ratio is 1:40. 

Spiral Gears

Spiral gears have curved tooth profile. The Spiral bevel Gears can be used to connect the shafts which are parallel and intersecting as well. This gear is mostly used in automobile differential system .

Rack and pinion

The Rack is a straight bar with the gear tooth on its longitudinal surface. The Pinion is a spur gear meshed with it. Rack and pinion gears are used to convert the linear motion into the rotary motion and vice versa.

Planetary Gears (Epicyclic gearing)

Planetary gearbox consists multiple numbers of gears.The center one is called the Sun gear, and the other gears around this sun gear are called the Planetary gears. The outer ring with the internal gear teeth is called the Ring Gear. This complete assembly is called planetary gearbox or epicyclic gearbox. This is an automatic gear transmission system mostly in automobiles.

Types of Gearbox

1. Sliding mesh gearbox
2. Constant-mesh gearbox
3. Synchromesh gearbox
4. Epicyclic gearbox

Sliding mesh type gearbox

Constant Mesh Gearbox

Synchromesh GearBox

Epicyclic GearBox

Types of Gear trains:

• Simple Gear Train
• Compound Gear Trains
• Reverted gear Trains
• Epicyclic Gear Trains(or) planetary gear trains

• Simple epicyclic gear trains
• Compound epicyclic gear trains

Simple Gear Train

A simple gear train consists of only one gear on each shaft. The gear 1 is transmitting the motion to the gear 2. So the transmitting gear 1 called the driver, and the receiving gear 2 is called the driven.When two gears are meshing externally, the direction of rotation of both the gears are in opposite direction. If  the distance between the two shafts is large, then, an intermediate gear is introduced in between two gears called the idle gear. Now the direction of rotation of extreme two gears are same. Speed ratio is not affected.

Compound Gear Train

In the above simple gear train, there will be only one gear on the shaft, if there are two gears on the same shaft then it will be the compound gear train. Following is the schematic representation of the compound gear train.The compound gear train is used where the distance between the two shafts has to be bridged by the intermediate gears and to maintain the speed ratio.

Reverted Gear Train

A Reverted Gear Train is also quite similar to the compound gear train, but when the driver and driven shaft are co-axial then it is called as Reverted Gear Train. 

In the Reverted gear train the motion of the driver gear (first) and the driven gear (Last), are in the same direction.

Epicyclic gear trains (or) Planetary gear trains:

•        Simple epicyclic gear trains
•        Compound epicyclic gear trains

Simple epicyclic gear trains

There is only one Gear on each shaft in simple epicyclic (or) Planetary gear trains. In this, the gear B rolls around the stationery gear A as arm C revolves.

Compound Epicyclic gear trains

Compound epicyclic gear train consists of many gears.

D= Sun Gear placed on centre position

B-C = Planet Gears are placed around sun gear.

A = Ring Gear