In this article, we shall learn the different types of gear trains. We have also provided a PDF download link for the same. When sometimes two or more gears are made to mess with each other to transmit power from one shaft to another such combination is called gear trains.

## Types of Gear trains

We have generally 4-types of trains which are as follows

- Simple Gear Train
- Compound Gear Trains
- Reverted gear Trains
- Epicyclic Gear Trains

## Simple Gear Trains

When there is only one gear fitted on each shaft, then this type of gearing system is named **Simple gear train.**

#### Speed Ratio/Velocity Ratio

It is the ratio of the speed of the driver’s gears to the speed of the driven gears. The ratio speed of any pair of gears is the inverse of the teeth.

Let consider,

- n1= Speed of gear 1 in RPM
- n2= Speed of gear 2 in RPM
- T1= Number of teeth in gear 1
- T2= Number of teeth in gear 2

In the case of a simple gear train, the speed ratio is

**(n1/n2)=(T2/T1)**

Then another important factor you should know about and that is Train Value.

#### Train Value

It is the ratio of the speed of the driven gears to the speed of the driver gears that is known as the training value.

The train value of simple gear train is

**n1/n2/=T1/T2**

It may be noted that when the number of intermediate gears is odd the motion of both the drive gear and driven gear have the same direction of motion, but when the number of driver gear and driven gear is even then we see the opposite direction of motion between driver and driven gears.

## Compound Gear Trains

When we need a higher speed ratio or a much lower speed ratio then we need to use **compound gear trains**. In this case, each intermediate shaft has two gears rigidly fixed to it. Due to both gears being fitted on the same shaft, we can see the same speed in both gears.

#### Speed ratio for Compound Gear Trains

If there are six total gears then

- n1= Speed of gear 1 in RPM
- n2= Speed of gear 2 in RPM
- n3= Speed of gear 3 in RPM
- n4= Speed of gear 4 in RPM
- n5= Speed of gear 5 in RPM
- n6=Speed of gear 6 in RPM
- T1= No. of teeth of gear 1
- T2= No. of teeth of gear 2
- T3= No. of teeth of gear 3
- T4= No. of teeth of gear 4
- T5= No. of teeth of gear 5
- T6= No. of teeth of gear 6

The speed ratio would be

**(n1/n2*n3/n4*n5/n6)=(T2/T1*T4/T3*T6/T5)**

**(n1/n6)= (T2/T1*T4/T3*T6/T5)**

[As n2 and n3, n4 and n5 is on the same shaft so the rpm of both the gears are same, therefore, n2=n3, n4=n5]

## Reverted gear Trains

In the case of the **reverted gear train**, the driver and the last gear are Co-axial. This type of arrangement is used in clocks and in simple lathes where back gears are used to give a slow speed to the chuck.

The speed ratio for reverted trains is

(n4/n1)= (Product of the number of teeth on driving gears/product of the number of teeth on driven gears)

## Epicyclic Gear Trains

The epicyclic gear train is useful for transmitting a high-velocity ratio with a gear of moderate size and in less space. We use an epicyclic gear train in Wrist Watch.

#### Table of Motions for Epicyclic gear trains

Suppose an Epicyclic Gear Train has 2 gears (Gear A and Gear B) and an Arm (Arm C). Then the table of motion looks will look like this

Condition Of Motion | Arm C | Gear A | Gear B |
---|---|---|---|

The arm is fixed gear a rotates through the +1 revolution anticlockwise. | 0 | +1 | -Ta/Tb |

Arm fixed gear a rotates through +x revolution | 0 | +x | -x *Ta/Tb |

Add +y to all elements | +y | +y | +y |

Total Motion | +y | +x+y | y-x*Ta/Tb |

This table is the same for all the problems regarding epicyclic trains, we just need to calculate the value by solving these bolded equations.

## Gear Trains Working video

## FAQ

#### What Are The Types Of Gear Trains?

We have generally 4-types of trains, which are as follows

- Simple Gear Train
- Compound Gear Trains
- Reverted gear Trains
- Epicyclic Gear Trains

#### What Is A Compound Gear Train?

A compound train is a type of gear system that uses two or more sets of gears to transmit power between the input and output shafts. By dividing the train into multiple stages, the compound gear train can achieve a higher gear ratio, allowing for greater torque multiplication and speed reduction. This makes them ideal for use in heavy-duty applications, such as in locomotives and industrial machinery.

#### What Is Epicyclic Gear Trains?

Epicyclic gear trains, also known as planetary trains, are a type of gear system that utilizes a central sun gear, planetary gears, and a ring gear to transmit power between the input and output shafts. They offer a high level of torque multiplication and speed reduction, making them ideal for use in heavy-duty machinery, automotive transmissions, and aerospace applications.

#### What Is An Inverted Gear Train?

An inverted gear train is a type of gear system in which the input and output shafts are located parallel to each other but rotate in opposite directions. This is achieved by reversing the direction of rotation in one of the stages of the gear train. Inverted gear trains are commonly used in automotive and marine applications, where space is limited and a compact design is required.

## Conclusion

In conclusion, gear trains are an essential part of many mechanical systems, and their various types provide the ability to transfer and modify torque and speed in a precise and efficient manner. From simple gear trains to complex planetary gear trains, each type has its own unique advantages and disadvantages, making them suitable for different applications. Understanding the fundamentals of gear trains and their operation is crucial for engineers and designers to create effective and reliable mechanical systems.