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• Clutch is a mechanical device that facilitates
transmission of power and motion from one
component (the driving member) to another (the
driven member) when engaged, with a provision
for disengagement whenever required.
• In the simplest application, clutches connect and
disconnect two rotating coaxial shafts. One shaft
is attached to a power unit (the driving member)
while the other shaft (the driven member)
provides output power for work. The motions
involved are rotary in nature.
• A clutch is designed with the following
– Allow the vehicle to come to a stop while the
transmission remains in gear
– Allow the driver to smoothly take off from a dead
– Allow the driver to smoothly change gears
– Must be able to transmit power and torque
Types Of Clutch
Types of Clutch
1. WET CLUTCH : Wet clutch is immersed in a cooling lubricating
fluid which also keeps the surfaces clean and gives smoother
performance and longer life. Wet clutches, however, tend to
lose some energy to the liquid.
2. DRY CLUTCH : Dry clutch, as the name implies, is not bathed in
fluid and runs dry.
• Clutch disengaged (Clutch pedal pressed)
The clutch is disengaged when
– Starting the engine
– Shifting the gear
– Stopping the vehicle and
– Idling the engine
• Clutch engaged
– Clutch pedal is released
Bolted to Crank shaft
(friction disk) splined to transmission
allows to push on
Bolted to flywheel – Applies the
spring force to clamp the friction
disk to the flywheel
(clutch fork) pushes T/O bearing
to release rotating clutch
Pilot bushing or bearing in center
of flywheel or crankshaft, supports
the end of input shaft
Construction of Automotive Single Plate Clutch
Single Plate Clutch
• Working- The diagram shows the pressure plate
pulled back by the release levers against the
compression springs; so that the friction linings
on the clutch plate are free of flywheel and
pressure plate. The flywheel rotates without
driving the clutch plate and hence the shaft.
• When the pressure of the thrust race is released
the compression springs are free to move the
pressure plate to the left bringing it in contact
with the clutch plate.
• The pressure plate moves to the left, sliding the
clutch plate on its splined hub, along the driven
shaft until the friction lining touches the
• The compression springs now cause the linings
to be gripped between the pressure plate and
the flywheel and the friction between the linings
and flywheel and pressure plate causes the
clutch plate to revolve, turning the driven shaft.
– Attached to the crankshaft
– Mass is used to store energy
– Has a machined surface on
which the clutch disc
– Has a ring gear on its
– Pressure plate is bolted to
Clutch disc (Friction Disc)
– Lined on both sides with a friction lining (similar to brake
pads). Various materials have been used for the disc friction
facings, including asbestos in the past. Modern clutches
typically use a compound organic resin with copper wire
facing or a ceramic material. Coefficient of friction of friction
disc surface is 0.35 for organic and 0.25 for ceramic. Ceramic
materials are typically used in heavy applications such as
trucks carrying large loads or racing
– Hub is connected to the input shaft of the transmission with
– Friction linings are separated by springs
• These springs allow the linings to “slip” while engaging
– Friction linings are connected to the central hub by torsional
dampening springs which help to dampen the shock and
isolate engine vibrations
• Torsional springs
– Can be spring or rubber
– Dampen power impulses from crankshaft
Have pins to limit amount of twist.
Springs try to keep it centered between pins.
• Cushion springs
– Waved metal between clutch halves
– Dampen clutch engagement
– Applies pressure to the clutch disc by ‘squeezing’ the clutch disc
between itself and the flywheel
– Allow the clutch disc to release when vehicle is stopped or
driver is shifting gear
A clutch linkage mechanism uses levers and rods to
transfer motion from the clutch pedal to the clutch fork.
When the pedal is pressed, a pushrod pushes the bell
crank and the bell crank reverses the forward movement
of the clutch pedal. The other end of the bell crank is
connected to the release rod. The release rod transfers
bell crank movement to the clutch fork. It also provides a
method of adjustment for the clutch.
– Right amount of
movement and direction
without too much pedal
– Less Wear
– Spring to pull T/O bearing
– Has to be lubricated
• No complicated linkage
The clutch cable mechanism uses a steel cable
inside a flexible housing to transfer pedal
movement to the clutch fork. The cable is usually
fastened to the upper end of the clutch pedal, with
the other end of the cable connecting to the clutch
fork. The cable housing is mounted in a stationary
position. This allows the cable to slide inside the
housing whenever the clutch pedal is moved. One
end of the clutch cable housing has a threaded
sleeve for clutch adjustment
• No complicated linkage
• Can easily control
with piston sizes
Servicing is similar to hydraulic brakes
Multi Plate Clutch
• Multi plate clutch is used when
– large torque is to be transmitted e.g. Heavy
vehicles and machine tools
– compact construction is required e.g. scooters and
• When a great amount of torque is to be transmitted, instead of single
plate a number of friction plates are employed. This increases the
number of mating friction surfaces, hence it is called multiplate clutch.
• These clutches are used in heavy commercial vehicles, racing cars and
motor cycles for transmitting high torque.
• In this friction rings are splined on their outer circumferences to mate
with corresponding splines on the bore of the housing and are free to
slide on the splines. The friction material therefore rotates with the
housing and engine shafts.
• Discs or plates are free to slide on the splines on the driven shaft and
rotate with it.
• The disc on the right can be moved to the right against a powerful
spring which, when the actuating force is removed, presses the disc
into contact with friction rings.
• Torque is therefore transmitted between the engine shaft and the
Multi Plate Clutch
It consists of a flywheel and a cone mounted on driving and
driven shafts respectively.
The shape of the side of the flywheel facing the cone is as
to accommodate the cone readily when the clutch is
The surfaces of contact are lined with the friction lining
(Asbestos, leather etc.).
The cone can be disengaged from flywheel by mechanism
which operates in the groove of the cone.
Maximum torque transmitted (T) = μWrm cosecα
α = semi-apex angle of
Only one pair of driving
surfaces is possible, n =1
• NOT used in automobiles
• The only advantage of this clutch is that the
normal force acting on the friction surfaces is
greater than the axial force, as compared to the
single plate clutch in which the normal force
acting the friction surfaces is equal to the axial
• The cone clutch is practically obsolete, due to the
– If the cone angle is made smaller than 20°, the cones
tend to bind and it is difficult to disengage the clutch.
– A small amount of wear on the cone surfaces results
in a considerable amount of the axial movement of
the cone which is difficult to compensate
Total friction torque (T) = nµR(F-P)
• The faster the RPM, more is the force on
Clutch Safety Switch
• Prevents from cranking with clutch engaged