Single Plate Clutch – Parts, Diagram, Working, Advantages

Introduction to Single Plate Clutch : 

Clutch lies in between the flywheel the gearbox, allows the engine power to be disconnected from the transmission to free it from the torque (turning effort) when gears are engaged or changed.

Single plate Clutch is the most common type of clutch used in motor vehicles. It consists of only one clutch plate, mounted on the splines of the clutch shaft.

The flywheel is mounted on the engine crankshaft and rotates with it. The pressure plate is bolted to the flywheel through clutch springs and is free to slide on the clutch shaft when the clutch pedal is operated.

When the clutch is engaged the clutch plate is gripped between the flywheel and the pressure plate. The friction linings are on both sides of the clutch plate.

Due to the friction between the flywheel, clutch plate and pressure plate, the clutch plate revolves with the flywheel. As the clutch plate revolves, the clutch shaft also revolves.

Functions of clutch:

i) A clutch is a device used to transmit the rotary motion of one shaft to the other shaft when desired.
ii) A clutch is a device used for engaging and disengaging the engine crankshaft instantaneously
when desired by the driver.
iii) A clutch is a device used to deliver power to machines partially or fully loaded.

Clutch Parts :

In general, a Clutch consists of three members, and those are:

  • Driving Members
  • Driven Members
  • Operating Members
single plate clutch diagram
single plate clutch diagram

Driving members:

It is consists of a flywheel mounted on the engine crankshaft. The flywheel is bolted to a cover that carries a pressure plate or driving disc, pressure springs, and release levers. Thus the entire assembly of the flywheel and the cover rotate all the time. The clutch housing and the cover provided with openings dissipate the heat generated by the friction during the clutch operation. 

(i) Flywheel:

The flywheel is the mounting surface for the clutch. The flywheel rotates as the engine crankshaft rotates. The friction or pressure plate bolts to the flywheel face. The clutch disc is clamped and held against the flywheel by the spring action of the pressure plate. The face of the flywheel is precision machined to a smooth surface. The face of the flywheel that touches the clutch disc is made of iron. Even if the flywheel were aluminum, the face is iron because it wears well and dissipates heat better. A pilot bearing or bush bearing supports the spigot end of the clutch shaft which is also housed in the flywheel. It is also the second driving member.

(ii) Pilot Bearing:

The pilot bearing or bushing is pressed into the end of the crankshaft to support the end of the transmission input shaft. The pilot bearing is a solid bronze bushing, but it also may be a roller or ball bearing. The end of the transmission input shaft has a small journal machined on its end. This journal slides inside the pilot bearing. The pilot bearing prevents the
transmission shaft and clutch disc from wobbling up and down when the clutch is released. It also assists the input shaft center of the disc on the flywheel.

Driven members:

It is consists of a disc or plate, called the clutch plate. It is free to slide lengthwise on the splines of the clutch shaft. It carries friction materials on both of its surfaces. When it gripes between the flywheel and the pressure plate, it rotates the clutch shaft through the splines.

Pressure clutch plate :

Constructional details

clutch plate
clutch plate

It consists of a steel plate with a splined central hub. Annular friction facing is attached to the steel plates by rivets. Special resins are also used to bind the friction facing. The curved cushioning spring segments are attached rigidly to the center plate and friction facings are riveted to these springs. Centre hub-assembly consists of a splined hub with radially placed slots in the flange of the hub. There are similar types of slots in each of the two plates situated on either side of the hub flange.

Different materials used for clutch lining:

1. Leather
2. Cork
3. Fabric
4. Asbestos
5. Reybestos and Ferodo
6. Non- asbestos clutch lining material

1. It should have a good anti-fading characteristic
2. It should have a longer life.
3. It should be nonpolluting.
4. It should have a lesser cost

State the location and function of Torsion damper spring and pressure spring in a single plate dry disc clutch.

Torsion damper spring:

  • Location: They are small coil springs located between the clutch disc splined hub and the friction disc assembly.
  • Function: These springs provide a flexible torsional connection between the center hub flange and side plates which are riveted to the main clutch plate.

Pressure Spring:

  • Location: These are helical springs located between the clutch cover and pressure plate in the clutch assembly.
  • Function: When your foot is off the pedal, the springs push the pressure plate against the clutch disc, which in turn presses against the flywheel. This locks the engine to the transmission input shaft, causing them to spin at the same speed.

(v) Clutch cover assembly:

The clutch cover assembly is bolted to the flywheel. It consists of a pressure plate, release lever mechanism clutch cover, and pressure springs. The figure shows the view of the clutch cover assembly. In general, the clutch plate revolves with the flywheel. But when the clutch is disengaged, the flywheel, as well as the pressure plates, will be forced to rotate independently from the driven plate and driving shaft. The release mechanism is used to release the clutch. The pressure plate is backed by a number of coil springs and housed with them in a pressed-steel cover bolted to the flywheel. The springs push the pressure plate against the cover.

Clutch plate Assembly
Clutch plate Assembly

Operating members:

It is consists of a foot pedal, linkage, release or throw-out bearing, release levers, and the springs necessary to ensure the proper operating of the clutch. 

(vi) Release mechanism:

The clutch levers are pivoted on pins in the clutch cover. Their outer ends are located and positioned on pressure plate legs and inner ends are projecting towards the clutch shaft. A careful and accurate adjustment of the release mechanism is one of the most important factors of governing the performance of a clutch assembly.

(vii) Withdrawal force and rearing:

The withdrawal force carrying the bearings is pivoted on a ball-mounted fulcrum in the clutch outer casing. The bearing is generally facing the inner end of the toggle lever. The other end of the force is connected to the clutch pedal by means of rods and levers.

(viii) Primary or clutch shaft:

The clutch plate is assembled on a splined shaft that carries the rotary motion to the transmission. This shaft is called the clutch shaft, or transmission input shaft. It is also known as the driving shaft of a gearbox. One end of the clutch shaft is attached to the crankshaft or flywheel and the other end is, connected to the gearbox or forms a part of the gearbox.

Types of Single Plate Clutch:

  • Coil Spring Type Single Plate Clutch
  • Diaphragm Spring Type Single Plate Clutch

Single plate Clutch Working:

A single disc or plate clutch as shown in figure, consist of a clutch plate whose both sides are faced with the friction material (usually ferrodo). It is mounted on the hub which is free to move axially along the splines of the driven shaft. The pressure plate is mounted inside the clutch body which is bolted to the flywheel. Both the pressure plate and the flywheel rotate with the engine crankshaft or the driving shaft. The pressure plate pushes the clutch plate towards the flywheel by a set of strong spring which are arranged radially inside the body. The three levers (also known as release levers or fingers) are carried on the pivots suspended from the case of the body. These are arranged in such a manner so that the pressure plate moves away from the flywheel by the inward movement of a thrust bearing. The bearing is mounted upon the forked shaft and moves forward when the clutch pedal is pressed.

Disengaging the clutch:

When the clutch pedal is pressed down, it’s linkage forces the thrust bearing to move towards the flywheels and pressing the pressure plate away from the flywheel thereby the compression springs are compressed. This action removes the pressure from the clutch plate and the driving shaft comes to a stationary position.

Engaging the clutch:

On the other hand, when the foot is taken off from the clutch pedal, the thrust bearing moves back by levers this action allows the springs to extend, and thus the pressure plate pushes the clutch plate back towards the flywheel. The clutch is
engaged and power is transmitted from engine to gearbox.

Single plate Clutch Working 
Single plate Clutch Working

Single Plate Clutch animation :

Difference Between Single Plate Clutch and Multi-Plate Clutch : 

Sr. no.Single Plate clutchMulti-plate clutch
1.It consists of only one clutch plate.It consists of two or more number of clutch plates.
2.The number of pairs of friction surfaces in contact are two.The number of pairs of friction surfaces in contact are more than two.
3.It does not ensure smooth engagement.It ensures a smooth and gradual engagement.
4.It requires more space.It requires less space.
5.For the same power transmission, larger in size.For the same power transmission, smaller in size.
6.For the same size, torque transmission capacity is less.For same size, torque transmission capacity is
7.Frictional power loss is less.Since it has number of friction plates instead of single, frictional power loss is more.
8.Application- Trucks, Jeeps, cars etc.Application- Two-wheelers, racing cars, some heavy-duty trucks.

Advantages of Single Plate Clutch :

Single plate clutch advantages are as follows : 

  1. Single plate clutch is smooth in operation i.e engagement and disengagement of clutch is smooth.
  2. Very less slip occurs in its operation. Slip only occurs during the engagement of clutch and after that no slipping occurs and functioning becomes very smooth.
  3. Very less heat is generated as only one clutch plate is used.
  4. The operation in this type of clutch is very fast.
  5. It makes easy to change gears than a cone type.
  6. It is reliable than a cone clutch.

Disadvantages of Single Plate Clutch :

Single plate clutch disadvantages are as follows : 

  1. It requires more force to release.
  2. The space required to accommodate the clutch is more as compared to the multi-plate clutch.
  3. The capacity of torque transmission is less.
  4. The size of this clutch is big even for less torque transmission.
  5. Chance of tear wear is high in single plate clutches.

Applications Of Single Plate Clutch : 

Single plate clutch applications are as follows :

  1. Single plate clutches are used in Buses, Trucks, and cars, etc. ( Ashok Leyland. , Flat – 1100,  Truck )
  2. Single plate clutches used where large radial space is available.
  3. As sufficient surface area is available for the heat dissipation in Single plate clutches, no cooling oil is required. Therefore, single plate clutches are dry type.

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Sachin Thorat

Sachin is a B-TECH graduate in Mechanical Engineering from a reputed Engineering college. Currently, he is working in the sheet metal industry as a designer. Additionally, he has interested in Product Design, Animation, and Project design. He also likes to write articles related to the mechanical engineering field and tries to motivate other mechanical engineering students by his innovative project ideas, design, models and videos.

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