Clutch, How does it work ?

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Have you, ever wondered what is happening inside a car, when you press the clutch pedal

Or, why, do you need, to press the clutch pedal before you shift gears in a manual transmission car

This, video gives you, logical answers to these questions

At the end of the video we will, also understand the crucial role played, by the clutch in an uphill start

To, understand the need for a Clutch let's first understand the anatomy of an internal combustion engine car

Internal combustion engines have a very limited torque band


Due to this reason in order to efficiently vary the speed of the drive wheels

internal combustion engine cars need a transmission system

The use of this transmission makes sure that the engine is working within its optimum rpm range and by changing gear

According to the driving conditions the transmission helps to control the drive wheel speeds

In a manual transmission car making these gear changes is not an easy task to have a smooth gear change with a

Manual transmission the engine power flow to the transmission has to be discontinued

However it is not practical to turn off the engine just for this gear change

The clutch is used for this purpose

in short the clutch is a mechanism to disconnect the flow of power to the transmission without turning the engine off

Let's understand how it works

The main part of the clutch consists of a disc coated with high friction material on both sides a

simplified clutch disc is shown here this disc sits on the flywheel if

An external force presses against the clutch disc the clutch disc also will turn with the flywheel due to the frictional force

The input shaft of the transmission is connected to the disc

So that when an external force is applied to the disc the engine power will get transmitted to the transmission system

This external force is provided by a Pressure plate spring system

Cover of this system is attached firmly to the flywheel

So the pressure plate will firmly press onto the friction clutch disc and the engine power will be transmitted to the transmission system

But this is the case in normal driving so how is the power disengagement done with the clutch

For the disengagement purpose a special kind of spring is introduced in the pressure plate

Assembly, this spring is known as a diaphragm spring

To understand this diaphragm spring better, assume that the diaphragm spring motion is fixed around

This circle in this case if you press the center portion of the spring as shown

the outer portion should move in the opposite direction

The diaphragm spring sits between the pressure plate and the cover

To understand this configuration better let's take a cross-section of the assembly

the outer portion of the diaphragm spring is connected to the pressure disc

This means if you press the inner portion as shown the pressure disc will move away from the friction disk

thus the power flow will discontinue to the transmission

This is exactly what happens when you press the clutch pedal

A hydraulic system transfers the clutch motion to the center of the diaphragm spring

When the diaphragm spring is pressed the power flow is discontinued?

During this time you can make a gear change the clutch pedal is released after the gear change and the power flow continues again

This is how a clutch works

In an actual clutch you can see a few coil springs on the clutch disc what's the purpose of these springs

These are used to smooth out the fluctuations and vibrations from the engine power output

It is clear that the hub and disc are not directly connected

The engine power first reaches the disk then it transfers to the springs and finally to the output hub

This means that the springs will dampen out most of the power flow

Fluctuations from the engine and the motion transferred to the vehicle will be much smoother

Now, let's explore an extremely important and difficult task in driving cars with manual transmission starting from uphill

Even in a car without a handbrake you can use this clutch technique to start, while pointing uphill

In an uphill start initially both the brake and clutch pedal are pressed, while the engine is running

Now, release the clutch pedal partially until you feel the clutch bite

The clutch bite can be experienced at. Your foot it may feel like the engine is shivering at

This point even if you release the brake pedal you can see the vehicle will not roll the

Partially released clutch acts like a brake now You can press the gas pedal and the car will move forward

The big question here is how does the partially release clutch act like a break

This break phenomenon is nothing but a game of force balanced in a perfectly forced balanced condition the vehicle

Wheels will not be able to roll and the gravitational pull will be the same as static frictional force at the wheels

The vehicle wheels are prevented from rolling by another force balance

Force balance between the engine forward force and the same static frictional force

When you partially release the clutch and it balances for the clutch bite you are unknowingly doing all these force balances

When these forces are in perfect balance the wheels the transmission system and the clutch disk will not be able to spin

This is how the clutch bite acts as a brake but remember the frictional force between the rubbing surfaces

Produces the engine forward force in this case this will result in wear and tear of the friction material on the clutch disc

We hope this video will enable you to be a better engineer and a better driver

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