Centrifugal Clutch

What is a Centrifugal Clutch?

Centrifugal clutches are mechanical devices designed to transfer the rotational power
from an engine to a transmission in a vehicle in order to facilitate gear changes. The
engine's rotation generates centrifugal force, which is used to engage and disengage the
clutch.

Small engines like those in go-karts, mini bikes, underbones, chainsaws, mopeds, and
lawnmowers frequently employ this kind of clutch. Due to its simplicity, dependability,
and low maintenance requirements, the centrifugal clutch is ideally suited for these
applications.

In response to the engine speed changing between acceleration and deceleration, this
system automatically engages and disengages the transmission to assist with smooth
acceleration and deceleration.

The vehicle's clutch paddle is not necessary in this type of system in order to shift the
clutch. An engine can be started or stopped by a driver without shifting up or down in
gear. When moving at high speed, the centrifugal clutch is more effective.

Read Also: What is a Single Plate Clutch? Diagram, Parts, Working & Applications

Parts of Centrifugal Clutch

The following are the centrifugal clutch's primary components:

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#1 Drum

A drum is an outer part of the clutch that rotates in conjunction with the crankshaft of
the engine. The drum encloses every component of the clutch, including the guides,
sliding shoes, springs, friction lining, and others. The drum is connected to the driven
shaft of the belt, chain, or transmission system.

#2 Clutch Basket

As the name suggests, the clutch basket is a stationary part of the clutch system that
holds clutch plates until they are needed.

#3 Clutch Plates

From the engine to the transmission, the clutch plate acts as a friction disc to transmit
the power from the engine to the transmission.

#4 Springs

A clutch plate is held in place by a clutch spring that applies pressure and helps keep
the clutch plates engaged with each other. Spring is typically used at slower speeds.
Each shoe has a spring attached to it.

#5 Shoe

When the clutch is engaged, the shoe is a component that is attached to the weights, and
it is in contact with the clutch basket when the clutch is engaged. Shoes are a potential
source of friction. The shoe is attached between the guides and functions primarily as a
sliding object. The shoes used to slide in guideways. It has a friction lining at the very
end.

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#6 Friction Lining

A component of the sliding shoes is the friction lining. The friction lining operates on
the same logic as a basic clutch's friction plate. This friction lining can be attached to the
outermost portion of shoes.

An inner friction lining transfers torque, making the drum's inner surface more gripped.
The sliding shoes and the drum are kept from coming into direct contact. By doing this,
the sliding shoes experience less wear and tear.

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#7 Spider

The spider is mounted to either the driver (engine) shaft or the motor shaft. Since there
is an equal distance between each spider, there is also an equal distance between each
guide.

As an illustration, if three guides are present, the next guide is 90 degrees away from
the first guide.

The shoes are kept in between these guides to absorb the friction, and each guide has a
spring to disengage the clutch.

#8 Weights

The clutch is engaged by weights, which are parts that are fastened to the drum. The
weights move outward as the engine speed rises due to centrifugal force and make
contact with the clutch basket, engaging the clutch.

#9 Key

The clutch is connected to the engine crankshaft by a key, enabling it to rotate with the
engine, and is another crucial component.

Read Also: How does a Multi Plate Clutch work? Diagram, Parts, and Uses [PDF]

Working Principle of Centrifugal Clutch

A centrifugal clutch works by engaging the clutch with centrifugal force. A weight
attached to the clutch shoes moves outward as the engine spins, making contact
between the shoes and the clutch drum.

An engine's power is transferred to the driven shaft through this engagement. In

situations where the engine speed drops, the weights move inward, disengaging the
clutch and allowing the engine to stop without stalling.

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Working of Centrifugal Clutch

Centrifugal clutches are automatic clutches that engage and disengage power
transmission based on engine speed. In order to operate the clutch mechanism,
centrifugal force is used.

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Clutch shoes and clutch drums are the two main parts of the clutch. The clutch shoes
are attached to the engine's crankshaft and have a pin that allows them to pivot freely.
Typically, the driven shaft is connected to the clutch drum.

When the engine's RPM increases, the rotating clutch shoes move outward due to
centrifugal force. As a result of this motion, the clutch shoes come into contact with the
clutch drum's inner surface.

During contact between the shoes and drum, friction is generated, which causes the
clutch drum to spin, transferring power from the engine to the shaft. A decrease in
engine RPM lowers centrifugal force, which disengages clutch shoes and stops power
transmission.

By using this mechanism, the engine, and transmission will not stall, and wear and tear
will be reduced.

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Types of Centrifugal Clutch

Centrifugal clutches come in a variety of designs, such as:

#1 Drum Type

The most popular kind of centrifugal clutch is the drum-type clutch. The drum-type
centrifugal clutch consists of a housing that is shaped like a drum and houses the clutch
shoes of the machine, and it is attached to the shaft that receives the input from the
machine.

#2 Shoe Type

In this type of clutch, the input shaft of the machine is connected to a rotating plate on
which the clutch shoes are mounted. To engage the clutch, the shoes must come into
contact with the inner surface of the clutch drum after being pushed outward by
centrifugal force.

#3 Cone Type

The input and output shafts of the machine are connected to two cones that serve as the
input and output shafts of the cone clutch type.

The clutch shoes are situated between the cones; as the input shaft rotates, the shoes are
pushed outward and engage the clutch.

#4 Roller Type

Instead of shoes, this clutch engages the clutch using rollers. The rollers are mounted on
pins that are joined to the clutch drum.

The rollers are pushed outward as the input shaft rotates and make contact with the
clutch drum's inner surface to engage the clutch.

#5 Diaphragm Type

This kind of clutch engages the clutch using a flexible diaphragm. When the input shaft
spins, the diaphragm is drawn outward and contacts the clutch drum, which then
engages the clutch mechanism as a result.

Read Also: Different Types of Gearbox: Parts, Working, and Applications

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Advantages of Centrifugal Clutch

Utilizing a centrifugal clutch has the following benefits:

1. The design of centrifugal clutches is straightforward, and they require little

periodic maintenance.
2. Centrifugal clutches are extremely reliable and unlikely to malfunction due to
their straightforward design.
3. As the engine speed rises, the clutch automatically engages, enabling smooth
acceleration.
4. Centrifugal clutches are relatively affordable in comparison to other types of
clutches.
5. Since they don't need any adjustments or involve installation processes,
centrifugal clutches are simple to install.
6. Due to their lightweight, centrifugal clutches are perfect for small, portable
power equipment.
7. For uses where a simple, dependable, and low-maintenance clutch system is
needed, centrifugal clutches are a great choice.

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Disadvantages of Centrifugal Clutch

The following are some drawbacks of using a centrifugal clutch:

1. Centrifugal clutches are not appropriate for applications requiring a smooth

engagement at low speeds because they only engage at a specific engine RPM.
2. Because of their limited torque capacity, centrifugal clutches might not be
appropriate for heavy-duty applications.
3. Since centrifugal clutches are not adjustable, they might not be suitable for tasks
that consider precise clutch engagement control.
4. Centrifugal clutches lack the ability to slip, which is critical in some situations,
like those where the engine must keep running even when the transmission is
not engaged.
5. Because a centrifugal clutch's clutch engagement is based on engine RPM, it can
be difficult to use in situations where the engine speed changes frequently.
6. These clutches are inappropriate for some applications due to their constrained
speed range, torque capacity, adjustability, and slip capability.

Read Also: What is Cylinder Head? Parts, Functions, Types and Applications

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Application of Centrifugal Clutch

These applications frequently employ centrifugal clutches:

1. Go-karts frequently use centrifugal clutches because they offer smooth

acceleration and are easy to use.
2. Centrifugal clutches are quite often used in mini bikes due to their simplicity and
dependability.
3. Due to their simple operation and minimal maintenance needs, centrifugal
clutches are commonly used in lawnmowers.
4. Centrifugal clutches are used in certain agricultural machineries, such as tillers
and cultivators, for their reliable and smooth power transmission.
5. Due to their low-maintenance operation, centrifugal clutches are used in a
variety of small power equipment, including generators and pressure washers.
6. To provide a smooth power transmission, these clutches are used in some
industrial equipment, including conveyors and material handling systems.
7. For stable and low-maintenance operation, centrifugal clutches are used in
portable power tools like chainsaws and hedge trimmers.
8. Some motorized bicycles use centrifugal clutches to transmit power smoothly
and consistently.

Wrapping It Up
For small engine applications where a straightforward and dependable clutch system is
needed, centrifugal clutches are the best choice. They are also appropriate for RC model
cars and other portable power equipment where lightness and usability are key
considerations.

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