Simple Gear Train- Explanation, Examples, Advantages, Disadvantages and Applications

Simple gear train is a gear combination of two or more gears in which only one gear is present in each shaft.
Simple gear train can consist of two, three, four or more gears with one gear in each shaft.
Every simple gear train has a driver gear and a driven gear. The driver gear is connected to a motor or crank which causes the rotation of the driven gear.
In simple gear train, when the distance between the two shafts is small, the two gears are made to mesh with each other to transit motion from one shaft to other.

When there are more than two gears in gear shaft, the intermediate gears change the direction of rotation of driven gear. Therefore they are known as idler gears.

# When number of intermediate gears are even, the driven gear rotates in opposite direction of the driver gear.
# When number of intermediate gears are odd, the driven gear rotates in same direction of the driver gear.

Now we will see the speed ratio calculation of simple gear train with two, three and four gears.

First let us see the speed ratio calculation of simple gear train with two gears.
This is the diagram of simple gear train with two gears.

The bigger gear is gear 1 and is the driving gear and the smaller gear is gear 2 and is the driven gear.

Now, let us see what speed ratio in simple gear train means.
Speed Ratio is the ratio of the speed of the driver gear to the speed of the driven gear.

Let, 

N1 = Speed of gear 1 in r.p.m.
N2 = Speed of gear 2 in r.p.m.
T1 = Number of teeth in gear 1.
T2 = Number of teeth in gear 2

Now, let us see the speed ratio calculation of simple gear train with three gears.
This is the diagram of simple gear train with three gears.

Now, let us seethe elements that make up thesimple gear train with three gears:-

1) Driver Gear (Gear 1): This is the gear that is connected to the power source. This gear is also called input gear which is conneccted to a input shaft and gets power from it.

2) Driven Gear (Gear 3): It is the output gear in the gear train. This gear is mounted on the output shaft to transmit power.
This gear is always kept at the end of the all the gears in the arrangement.

3) Idler Gear (Gear 2): This gear is always present in betwwen the driver gear and driven gear. Idler gear are also called intermediate gears.
These gears are used to change the rotation of the output shaft.
There can be more than one idler gears in the arrangement based on the length of the shaft.

Now multiplying 1 and 2, we get

Train Value:-
Train Value is the reciprocal of Speed Ratio.

Examples of Simple Gear Train:

Bicycle:- The sprockets and chain on a bicycle are an example of a simple gear train.
Analog Clocks:- The traditional analog clocks use simple gear trains to transmit motion.

Advantages Of Simple Gear Train:-

1) Simple gear train transfers large amount of power without a slip unlike other means of power transmissio like belt drives.
2) Simple gear trains an be used to transfer power to a larger distance.

Disadvantages Of Simple Gear Train:-

1) Simple gear train cannot provide highergear ratios in a small space or when shafts are distant as compared to a compund gear train
2) The cost ofsimple gear train is more than chain drive ora belt drive which are used to produce similar power output.
3) Lubrications of gear teeth are necessary for smooth functioning.

Applications Of Simple Gear Train:-

1) It is used in automobile gearboxes.
2) It is also used in heavy duty presses and lathe machines.
3) In various ‘all wheel drive off road vehicles’, it serves as a differential when switching between rear-wheel drive and front wheel-drive.

Difference Between Simple Gear Train and Compound Gear Train:

Simple Gear Train	Compund Gear Train
There is only one gear in each shaft.	There aremore than one gear in each shaft.
The gear ratio depends upon the input and the output gears only and not on the interediate gears.	The gear ratio depend on the input and output gears as well as the intermediate gears.
It is difficult to obtain a higher gear ratio	Higher gear ratio can be achied easily.
The intermediate gears can be idle gear only.	The intermediate gears can be idle orcompound gears.