An introduction to gear trains and their working
Here I am going to discuss about the gear trains and their working principle. Gear is a basic element which is used to transmit power from one shaft to another. In this section the important types of gear trains are descibed.
Introduction
Today, a lot of automobiles, machines and prime movers have increasingly manufactured by several mechanical industries. The main part in these field is a gear whose application is tremendous. Thus as mechanical and automobile engineers need the knowledge of gears technology to implement in their design process. The gears are used with many components together with engines. The basics of gear and gear trains are given below:
Gear train - Definition:
If more than two gears are arranged to transmit power, such arrangement is called as gear train. The types of gear train are given below:
- Simple gear train
- Compound gear train
- Reverted gear train
- Epicyclic gear train
Simple Gear Train:
If there is only one gear mounted on each shaft, the gear train is known as simple gear train. that is, each shaft has only one gear.
Usually when two gears mate, they rotate opposite to each other. When we use three gears each mounted on separate shaft, the direction of rotation of the last gear will be same as that of the direction of rotation of first gear. Suppose the number of gears are increased to four the direction of rotation of first and last gear will be opposite to each other. A typical simple gear train is shown in the figure 1.
So from above we can conclude that in a simple gear train, if the no of gears is odd then the direction of rotation of first and last gear will be the same, it it is even, direction of rotation will be opposite.
The speed ratio is given by, (N1/N2) = -(T2/T1), where, N1 is the speed of the driver, N2 is the speed of driven gear, T1 is the no of teeth on driver gear and T2 is the no of teeth on driven gear.
Compund Gear Train:
If there is more than one gear on a shaft, the gear train is said to be compound gear train. Here speed of rotation of the gears mounted on a shaft will the same and also the direction. By using this arrangement, the power will be transmitted to the shaft which is placed not in the row. The system is compact here. Also we can reduce the size of the gears using this arrangement. This is illustrated in the Figure 2.
Reverted Gear Train:
If the axes of driver shaft and driven shaft is co-axial, then the gear train is termed as reverted gear train. This is kind of compound gear train. This is illustrated in the figure 3. So reverted gear train may be called as a compund gear train but all compound gear train can not be a reverted gear train. This reverted technology is very much useful when the power is to be transmitted within the less space.
Epicyclic Gear Train:
This is important gear train compared the said above. In this case, One of the gear is rotating over and around another gear. Epi means over, Cyclic means around. There is an arm connecting such two gears. This gear train finds great application in various field. This is illustrated in the figure 4.
Applications:
Gears are applied in various services and products. We can not imagine the world without them. Some of the applications are listed below:
Conclusion:
These are the impotant gear trains used for various purposes. Epicyclic gear train is used in different places where the sun and planet arrangement is needed. Finding the suitable gear train is a challange task to the design Engineers.
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