MechStuff

In my previous article, we learned about Single plate clutches, their working and applications.
Multi plate clutches are the most widely used amongst all the other clutches. And so today we will learn how multi plate clutch work, their advantages, disadvantages and their applications.

Parts in a multi plate clutch –

1. Input and output shafts –

Input shaft of clutches is the crankshaft of engines and it continuously rotates as you turn on the ignition.
Output shaft is connected further to gearbox and differential and it only rotates when the clutch is engaged.

2. Pressure plates –

Pressure plates are plates mounted on a splined shaft so that they can slide back and forth. Friction discs are bolted to the pressure plate. The sliding is controlled by the clutch pedal.

3. Friction discs –

Multiple friction discs having high coefficient of friction are bolted to pressure plates as well as mounted on the output shaft.

4. Spring and lever action mechanism –

The clutch pedal is connected to multiple levers to move the pressure plates backwards while spring is connected in series to expand back the position of plates i.e move the plates forward.

Here is a detailed article on how single plate clutch works & its parts with animation.

Working of Multi plate clutch –

To understand better, lets consider 2 cases –

Case A – Clutch is DISENGAGED.

1. When the clutch is disengaged, work is done by the human. Clutch pedal is PRESSED.
2. As the pedal movement is transferred via levers, work is done on spring & the pressure plates move back as shown in the image.
3. At this time, there is no contact between pressure plates and the friction discs and because of this, only input shaft rotates & vehicle does not move.

Case B – Clutch is ENGAGED.

1. When the clutched is engaged ,work is done by the spring by expanding itself. Clutch pedal is NOT pressed.
2. The spring deformation pushes the pressure plates forward. This exerts an axial force on the friction discs.
3. This generates a frictional force since the pressure plates are rotating while the friction plates aren’t. The friction then forces even the output shaft to rotate.
4. More the axial force, more the power transmission & vice versa.

Note :-

When the clutch pedal is partially pressed, only partial power/torque is transferred. This is called as slip condition. Foe example lets say, you have pressed the clutch pedal only little. So if the axial force by the spring on the friction discs is 50%, then the power transmission will also be 50%.

Advantages –

1. For same size of single plate clutch, multi-plate clutches can deliver significantly higher amount of power.
2. It has a very compact size.
3. Since they are small in size, they have low rotational inertia.

Disadvantages –

1. They heat up quickly.
2. The oil used for heat dissipation reduces the friction between plates. Hence this factor must always be considered while designing multi plate clutches and is sometimes compensated by adding an extra pair of friction discs.
3. Multi plate clutches have many parts. Hence if anything goes wrong, it takes time to identify, disassemble & troubleshoot the problem.

Applications –

The are used in a variety of applications.

1. Multi plate clutches are used in trucks, locomotive engines, ships, automobiles and industrial machines.
2. They are greatly found in drag racings as well as in F1 cars.
3. They are also used in heavy machinery such as excavators, crawlers, bulldozers & tanks!

If you liked this article you will definitely like my another article on Types of clutches! I’ve explained with diagrams and animations with their application.