Centrifugal Clutch: Principle, Construction, Working, Advantages and Disadvantages with Application

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Hello guys…

In this article we are going to discuss about
centrifugal clutch. We all aware about the word “ Centrifugal ”. People who
don’t know about this word or haven’t heard this word yet, don’t feel panic. We
will discuss these thing from basic so any one can understand about it
easily.

Before discussing about centrifugal clutch, we should know
about clutch. If you learn basic idea of clutch, trust me you can easily
understand about any type of clutch and if you are a mechanic, you can choose the best
one according to your requirement.
Let’s learn it with an example. Suppose you are driving a
car and suddenly you need to move car on a hill. At this point you need to
shift higher gear which can achieve higher torque. If you directly shift your car gear lever to change the gear, you will definitely feel some shocks and sometime
it can also damage car gear and car too. Guess why this happen??
When you shift gear
of your car, the gearbox is in running position. The machine found difficultly
to shift from one gear to another during running condition due to improper
alignment and inertia of running as well as stable gear.  If we can disengage the gearbox from engine
by some mean in running condition, we can easily shift gears. So for proper
working of any vehicle we need a device which can engage and disengage the
transmission shaft or gearbox from engine shaft when we needed or according to
the operating condition. This device is known as clutch.
This is basic idea behind any clutch. Now let’s we will
discuss about the word “centrifugal”.

What is centrifugal or centrifugal force?

Lets learn with an example. Have you ever ride on marry go
round? If yes, you remembered that When the wheel of marry go round move faster
you have to hold railing tightly. It is to create balance between two forces
acting on the body due to rotation. When any particle moves in circular path
two force act on it. The first one is real force which directed towards the
center and keep the object on path. The other one is centrifugal which is
apparent one and directed towards outside the line of center. These both forces
are in balanced condition which is required for proper rotation of a body.

Centrifugal clutch:

Principle:

Now you are aware about both term centrifugal and clutch. A
device which is used to engage and disengage driving and driven shaft known as
clutch. A simple basic clutch has two plates, the first one is connected with
driving shaft or flywheel of engine and the other one is with driven shaft.
These shaft remains in contact in primary condition and transfer torque from
driving member to driven member through friction. The initial force due to
which these both plates remains in contact achieve by springs. When the driver
press the clutch pedal, both these plates loose its contact and at this point
clutch is in disengage position. At this point no power is transfer from
driving member to driven member until the driver release the clutch pedal.
All friction clutch works on same principle. In centrifugal
clutch the initial force which are used to engage the clutch is achieve by
centrifugal action or centrifugal force. This centrifugal force automatically
engage the clutch at a predefine speed and disengage it when the engine slow
down below a limit.

Till now We have learnt about basic idea of centrifugal
clutch. We will learn about construction and practical working of this clutch
in later portion of this article.

Construction:

The centrifugal clutch consists following parts. I highly
recommend to read the below diagram during reading about its construction.

Spider or Guide:

Spider or guide is works as one of the pressure plate of
simple clutch. It is connected to the driving shaft of engine. It is called
guide way because it hold the shoe and guide its movement. The initial position
of shoe in the guide is controlled by the springs.

Drum:

Drum act like the another pressure plate of a simple clutch.
It is connected with the driven member and rotate with it. Drum does not
directly connected with the guide or shoe.

Shoe:

Shoe is major part of centrifugal clutch. It act like
engaging member of guide and drum during running condition. When the driving
shaft rotate, it makes rotate the shoe which are free to move in guide. Due to
rotation a centrifugal action works on it which force it outward and connect
with drum. 

Springs:

Springs are controlling element of this type of clutch. Each
shoe require one spring. The shoe are connected with the guide through these
springs. It hold the shoe at its initial position unlit driving member achieve
the required speed at which the centrifugal force can overcome spring force. If
we want to change the engaging speed of the clutch, we simply change these
springs with higher spring indexed springs.

Friction Lining:

The outer face of the shoe which is going to connect with
drum is equipped with friction lining. These lining play the same role which
friction plate play in simple clutch. It is used to transmit torque from
driving member to driven member and also avoid direct contact of shoe through
drum which reduce wear and tear of shoe.

Working:

Now you have understand purpose and construction of
centrifugal clutch. I think you have also got the idea of its working. We can
summarize it in following point.
  • At the initial condition when the engine is off the shoe are
    not connected with the drum.
  • As the engine start, the Spider or Guide attached with
    engine shaft start to rotate.
  • The shoe connected with the spider also rotate with it and
    felt some centrifugal action. This centrifugal force makes shoe to slide in the
    direction of circumference.
  • At low speed, the centrifugal force is too low to
    overcome the spring force which tend to bound the shoe inside the guide.
  • As the speed increases the shoe move outside and make a
    contact with drum. The friction lining between shoe and drum start to transfer
    torque from engine to drum.  
  • Now the drum start to rotate and as the speed of engine
    increase, it will increase the centrifugal force and also the efficiency of
    torque transmission through centrifugal action.
  • When the engine speed decrease, will decrease the
    centrifugal action which remove the contact of drum and shoe and disengage the
    clutch.
  • Thus this is an automatically speed
    operated clutch. The operating speed of clutch can be maintained by replacing
    spring.
For clear picture of its working, watch this video. 

Advantages:

  • It is low in price.
  • Easy to operate.
  • It doesn’t require any separate control
    mechanism like clutch pedal etc.
  • The engaging speed can be
    preciously controlled by selecting springs.
  • It is used for automating
    transmission in which the driver first select gear and then press the
    accelerator pedal.
  • It requires less maintenance. 

Disadvantages:

  • Power transmission is limited due
    to slippage.
  • It cannot used to transmit high
    amount of torque.
  • The power transmission or speed
    regulation is totally depended on controlling speed.
  • Overheating problem due to quick
    engagement during running condition.

Application:

  • It is used in chain saw, lawn
    mower etc.
  • It is used in textile industries.
This is all about centrifugal clutch principle, parts, construction, working, advantages, disadvantages and application. If you have any query regarding this article, ask by commenting. If you like this article, don’t forget to share it on social network. Subscribe our website for more informative articles.

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