Clutch is a mechanism which enables the rotary motion of one shaft to be transmitted, when desired, to a second shaft the axis of which is coincident with that of first. Clutch is used to engage or disengage the engine to the transmission or gear box.

1. CLUTCH
Prepared by:
Sagar Joshi

2. WHAT IS CLUTCH?
 Clutch is a mechanism which enables the rotary
motion of one shaft to be transmitted, when
desired, to a second shaft the axis of which is
coincident with that of first.
 Clutch is used to engage or disengage the engine
to the transmission or gear box.

3. WHAT IS CLUTCH?
 When the clutch is in engaged position, the engine
power or rotary motion of engine crankshaft is
transmitted to gear box and then to wheels.
 When clutch is disengaged, the engine power does
not reach to gear box (and to wheels) although
engine is running.

4. WHAT IS CLUTCH?
 Clutch is also used to allow shifting or changing of
gears when vehicle is running.
 For shifting gears, clutch is first disengaged then
gear is shifted and then clutch is engaged.
 Clutch has to be disengaged to stop the vehicle and
also at the time of idling.

5. PRINCIPLE OF CLUTCH
 It operates on the principle of friction.
 When two surfaces are brought in contact and are
held against each other due to friction between
them, they can be used to transmit power.
 If one is rotated, then other also rotates.
 One surface is connected to engine and other to
the transmission system of automobile.

6. PRINCIPLE OF CLUTCH

7. REQUIREMENTS OF CLUTCH
(1)Torque transmission
(2)Gradual engagement
(3)Heat dissipation
(4)Dynamic balancing
(5)Vibration damping
(6)Size
(7)Inertia
(8)Clutch free pedal play
(9)Ease of operation

8. CLASSIFICATION OF CLUTCH

9. SINGLE PLATE CLUTCH

10. SINGLE PLATE CLUTCH
 A single plate is commonly used in cars and light
vehicles.
 It has only one clutch plate which is mounted on the
splines of the clutch shaft.
 A flywheel is mounted on the crankshaft of the
engine.
 A pressure plate is connected to the flywheel
through the bolts and clutch springs.
 It is free to slide on the clutch shaft with the
movement of clutch pedal.
 When clutch is in engaged position, the clutch plate
remains gripped between flywheel and pressure
plate.

11. SINGLE PLATE CLUTCH
 Friction linings are provided on both the sides of
clutch plate.
 On one side clutch plate is in touch with flywheel
and on other side with pressure plate.
 Due to friction on both sides, the clutch plate
revolves with engine flywheel.
 Therefore, clutch transmits engine power to clutch
shaft.
 Clutch shaft is connected to transmission (or gear
box) of automobile.
 Thus, clutch transmits power from engine to
transmission system which inturn rotates wheels of
engine.

12. SINGLE PLATE CLUTCH
 When the clutch plate is to be disengaged, the
clutch pedal is pressed.
 Because of this pressure plate moves back and
clutch plate is disengaged from flywheel.
 Thus, clutch shaft stops rotating even if engine
flywheel is rotating.
 In this position, power does not reach the wheels
and vehicle also stops running.

13. SINGLE PLATE CLUTCH
 Advantages:
a) With this type of clutch gear changing is easier
than with the cone clutch, because pedal
movement required is less in this case.
b) It is more reliable. (Avoids the problem of binding
of cones)
 Disadvantages:
a) The greater force is required to disengage the
clutch.

14. MULTI PLATE CLUTCH

15. MULTI PLATE CLUTCH
 Multi-plate clutch consists of more than one clutch
plates contrary to single plate clutch which consists
of only one plate.
 Due to increased number of friction surfaces, a multi-
plate clutch can transmit large torque.
 Therefore, it is used in racing cars and heavy motor
vehicles witch have high engine power.
 The clutch plates are alternatively fitted with engine
shaft and the shaft of gear box.
 The plates are firmly held by the force of coil springs
and they assembled in a drum.

16. MULTI PLATE CLUTCH
 One plate slides in the grooves on the flywheel and
the next plate slides on spines provided on pressure
plate.
 Thus, each alternate plate slides in grooves on the
flywheel and the other on splines of pressure plate.
 If we take two consecutive plates, then one has inner
and other has outer splines.

17. MULTI PLATE CLUTCH
 When the clutch pedal is pressed, the pressure
plate moves back against the force of coil spring,
hence the clutch plates are disengaged and
engine flywheel and gear box are decoupled.
 However, when clutch pedal is not pressed the
clutch remain in engaged position and the power
can be transmitted from engine flywheel to the
gear box.

18. CONE CLUTCH

19. CONE CLUTCH
 In this type of the contact surface are in the forms of
cones.
 In the engaged position, the male cone is fully inside
the female cone so that the friction faces are in the
complete contact.
 This is done by means of springs which keep the male
cone pressed all the time.
 When the clutch is engaged, the torque is transmitted
from the engine via flywheel and male cone to splined
gear box shaft.
 For disengaging the clutch the male cone is pulled out
by means of the lower system operated through the
clutch pedal thereby separating the contact surface.

20. CONE CLUTCH
 Advantages:
a) Less force is required to disengage the clutch.
 Disadvantage:
a) If the angle of cone is made smaller than about 20°
the male cone tends to bind or join in the female
cone and it becomes difficult to disengage the clutch.
b) A small amount of wear on the cone surface in a
considerable amount of the axial movement of the
male cone for which it will be difficult to allow.

21. DIAPHRAGM CLUTCH

22. DIAPHRAGM CLUTCH

23. DIAPHRAGM CLUTCH
 In the engaged position the spring pivots on the
inner pivot rings as it is held on the clutch cover so
that its outer rings contacts with the pressure plate.
 Again in this conical position the spring exerts
through pressure to keep the pressure plate in firm
contact with the clutch plate and flywheel.
 When the pedal is depressed the linkage moves
release bearing towards the flywheel to disengage
the clutch

24. DIAPHRAGM CLUTCH
 As the bearing contacts with inner position of the
conical springs it moves that position forward which
cause the link to move backward.
 This removes the pressure on the pressure plate
and release the clutch plate from contact with other
driving members.

25. DIAPHRAGM CLUTCH
 Advantages:
a) It is a more compact means of storing energy.
b) In case of coil spring the load deflection curve is
linear, so with the wear of clutch facing the springs
have less deflection due to which they would
apply less force against the clutch plate. While in
the case of diaphragm spring the load deflection
curve is non-linear. So due to wear of clutch facing
the force applied by spring increases. So even in
worn out condition of clutch force applied by the
spring is not less than that by new clutch.

26. SEMI CENTRIFUGAL CLUTCH

27. SEMI CENTRIFUGAL CLUTCH
 For small torque transmission the clutch spring may
be designed so that they have sufficient strength for
applying required amount of force and at the same
time are not so stiff to cause the strain to the driver
while disengaging.
 For high powered engines, the clutch spring
pressure required may be considerable and thus
the action of disengaging the clutch becomes
fatiguing to the driver.
 To avoid this trouble, for higher speeds, the
centrifugal assists system is applied which helps in
transmission of torque along with clutch spring.

28. SEMI CENTRIFUGAL CLUTCH
 Three hinged and weighted levers are arranged at
equal intervals.
 This lever is having a fulcrum at point A and is
hinged to pressure plate at B.
 The upper end of the lever is weighted at C.
 D is adjusting screw, with the help of which
maximum centrifugal force acting on the pressure
plate can be adjusted.
 At moderate speed the pressure of spring is
sufficient to transmit required torque.
 However at higher speeds the weight C due to the
centrifugal force moves about A as fulcrum thereby
pressing the pressure plate.

29. CENTRIFUGAL CLUTCH

30. CENTRIFUGAL CLUTCH
 This type of clutches operates automatically
depending on engine speed .
 The advantage of the centrifugal clutch is that no
separate clutch pedal is required.
 The engagement and disengagement of the clutch
is done only by centrifugal force.
 This makes driving operation very easy.
 As the speed increases, the weight A flies, B bell
crank lever operates and presses the plate C which
in turn presses plate D by means of springs and
clutch got engaged.
 Spring G is provided to disengage the clutch.
 The stop H limits the amount of centrifugal force.

31. ELECTROMAGNETIC CLUTCH

32. ELECTROMAGNETIC CLUTCH
 In this system the clutch is controlled by means electric
current supplied to the field windings in the flywheel.
 The fly wheel is attached with the field winding, which is
given electric current by means of battery, dynamo or
alternator.
 The construction feature of main components is almost
similar to the single plate clutch.
 When electric current is supplied to the windings the
flywheel will attract the pressure plate and clutch plate is
forced between pressure plate and flywheel resulting in
engagement.

33. ELECTROMAGNETIC CLUTCH
 When the supply to the winding is cut off the clutch
is disengaged by releasing the pressure plate due
to the force exerted by the helical springs or tension
springs.
 Electromagnetic clutch consists of a clutch release
switch.
 When then driver holds the gear lever to change
the gear, the switch is operated cutting off the
current to the winding which causes the clutch
disengaged.

34. HYDRAULIC CLUTCH

35. HYDRAULIC CLUTCH
 It consists of a cylinder with piston, control valve,
pump, accumulator and oil reservoir.
 The piston is connected to the clutch by a linkage.
 The pump is operated by the engine itself.
 The oil from the reservoir is pumped into the
accumulator tank.
 The accumulator tank is connected to the cylinder
through the control valve.
 The control valve is electrically controlled by a
switch in the gear lever.

36. HYDRAULIC CLUTCH
 When the driver holds the gear lever to change the
gears, the switch is operated to open the control
valve admitting the oil under pressure to the
cylinder.
 Due to the oil pressure, the piston moves causing
the clutch to be disengaged.
 As soon as the driver leaves the gear lever, the
switch is open which closes the control valve and
the clutch is engaged.

37. VACUUM CLUTCH

38. VACUUM CLUTCH
 The vacuum clutch is operated by the vacuum
existing in the engine manifold.
 It consists of a vacuum cylinder with piston,
solenoid operated valve, reservoir and a non-return
valve.
 The reservoir is connected to the engine manifold
through a non return valve.
 Vacuum cylinder is connected to the reservoir
through solenoid operated valve.
 The solenoid is operated from the battery and the
circuit incorporates a switch which is placed in the
gear lever. The switch is operated when the driver
holds the lever to change gears.

39. VACUUM CLUTCH
 In the normal operation, the switch in the gear lever
remains off, the solenoid operated valve remains in
its bottom position.
 In this positions the atmospheric pressure acts on
both the side of the vacuum cylinder, because the
vacuum cylinder is open, so also atmosphere
though a vent.
 When the driver holds the lever to change the gear,
the switch is closed; energizing the solenoid which
pulls the valve up.

40. VACUUM CLUTCH
 This connects one side of vacuum cylinder to the
reservoir.
 Due to the difference of pressure on the vacuum
cylinder piston, it moves.
 This movement of the piston is transmitted by a
linkage to the clutch, causing it to disengage. When
the driver is not operating the gear lever, the switch
is open and the clutch remains engaged due to the
force of springs.

41. DOG AND SPINE CLUTCH

42. DOG AND SPINE CLUTCH
 This type of clutch is used to lock two shafts
together or to lock a gear to a shaft.
 It consists of a sleeve having two sets of internal
splines.
 It slides on a splined shaft with smaller diameter
splines.
 The bigger diameter splines match with the external
dog clutch teeth on driving shaft.

43. DOG AND SPINE CLUTCH
 When the sleeve is made to slide on the splined
shaft, its teeth match with the dog clutch teeth of
the driving shaft.
 Thus the sleeve turns the splined shaft with the
driving shaft. The clutch is said to be engaged. To
disengage the clutch, the sleeve is moved back on
the splined shaft to have no contact with the driving
shaft.
 The driven shaft revolves exactly at the same
speed as that of the driving shaft, as soon as the
clutch is engaged. Therefore it is also known as
positive engagement clutch.

44. CLUTCH COMPONENTS
 Clutch Plate
 Clutch Facing
 Pressure Plate
 Springs
 Release lever
 Bearing
 Cover
 Straps

45. CLUTCH PLATE
 A clutch plate consist of a steel plate with splined
hub, friction facing and the rivets for attaching the
friction facing with plate.
 Facing are binded with plate by using resins.
 Three types of clutch plates are available
a) Solid clutch plate
b) Axially cushioned clutch plate
c) Axially and torsionally cushioned clutch plate

46. CLUTCH PLATE

47. CLUTCH FACING
 Requirements of efficient clutch facing:
a) Good wear resistance at very high speed and high
intensity of pressure
b) High coefficient of friction
c) High heat resistance
d) Cheap and simple construction
e) Light in weight
f) Long life

48. CLUTCH FACING MATERIALS
 Common materials used for clutch lining are:
(i) Asbestos: It can be used at high temperature also and
linings of this material have coefficient of friction of about
0.4-0.75.
(ii) Reybestos and Ferodo: These materials are most
suitable and generally used for clutch friction linings and
have a co efficient of friction of about 0.35.
(iii) Leather: The co-efficient of friction between dry leather
and iron is 0.27.
(iv) Cork: The co-efficient of friction between cork and steel
or iron is 0.32.
(v) Fabric: This material has co-efficient of friction about
0.4, but it cannot be used a high temperature.

49. TYPES OF FACINGS ON THE BASIS OF THEIR
MANUFACTURING METHODS
 The various types of friction materials are as given
under—
(i) Mill board type: This material is in the form of sheets
made of asbestos and treated with certain impregnates.
From the standard sheet we can cut facing discs
according to different size requirements. This is the
cheapest material and gives satisfactory results.

50. TYPES OF FACINGS ON THE BASIS OF THEIR
MANUFACTURING METHODS
(ii) Moulded type: When asbestos fibers are mixed with a
suitable binder and heated to a definite temperature and
then moulded in dies under pressure, this type of friction
material is called “moulded type”. To improve the wearing
qualities of the material (sometimes metallic wires are
also inserted). This type of lining is stronger, dense and
capable to transmit heavy loads through it. The
disadvantage is only this that moulding for each size
lining is very costly.

51. TYPES OF FACINGS ON THE BASIS OF THEIR
MANUFACTURING METHODS
(iii) Woven type: This type of material is made by spinning
threads from asbestos fibers, weaving this thread into a
cloth and then impregnating it with a bonding material.

52. PRESSURE PLATE
 High tensile grey iron is the most commonly used
material for pressure plate, which must be sufficiently
rigid so as not to distort under the pressure of clutch
springs.
 Adequate rigidity is also required to provide uniform
pressure to clutch plate.
 The pressure plate should also have sufficient mass and
thermal conductivity to absorb and conduct away the
heat generated during engagement.

53. Release lever:
 The pressure plate in case of coil spring type clutch
has a three or four number of release levers.
Cover:
 This is steel pressing bolted in to flywheel and
houses the pressure plate assembly.
 It provides pivot for release lever and takes the
reaction of springs, so it must be sufficiently rigid.
 It should have holes for the dissipation of heat.

54. Springs:
 Normal duty clutch springs are made from spring
steel wire.
 Spring provides continuous force on the pressure
plate and provides contact between pressure plate,
clutch plate and flywheel.
 The stiffness of spring should not be very high,
because it requires excessive release pressure.
Throw out Bearing:
 It is used to transfer force at the pedal from the
stationary linkage to the rotating clutch.

55. FLUID FLYWHEEL

56. FLUID FLYWHEEL
 The fluid flywheel or hydraulic coupling as it is frequently
called, has been used in cars employing automatic
transmission.
 It consists of two members, the driving and the driven as
shown in fig.
 The two members do not have any direct contact with
each other.
 The driven member is free to slide on splines on the
transmission shaft.
 The two rotors are always filled with fluid of suitable
viscosity.
 These are provided with radial ribs to form a number of
passages, which avoid formation of eddies and also
guide the fluid to flow in the desired direction

57. FLUID FLYWHEEL
 Advantages:
a) No wear on moving parts
b) No adjustment to be made
c) No maintenance and simple design
d) No jerk on transmission
 Disadvantages:
 Chances of slip
 Considerable vibration

58. CLUTCH ADJUSTMENT
 Clutch pedals are invariably provided with some free
play.
 It means free movement of pedal without causing any
movement of linkage.
 It is provided deliberately to safeguard against rapid
wear of the clutch plate and other components of
linkage.
 The free play should not be very small or very large.
 If it is very small, it does not allow complete
engagement of clutch and if it is to large it does not
allow complete disengagement of clutch.
 The clutch operation is continuous and driver has to
apply continuous effort by his legs on the lever. So
design of lever should be proper to avoid unnecessary
cumbersome to driver.

59. CLUTCH OVERHAUL
 A general procedure for clutch overhaul is as under.
1) Removing the clutch
2) Disassembling
3) Inspection and Service
4) Assembly
5) Refitting the clutch

60. CLUTCH OVERHAUL
1) Removing the clutch:
General procedure is as followed.
a) Remove transmission from chassis including various
clutch and transmission linkages.
b) Loosen the bolts securing the clutch to the flywheel.
This must be done diagonal wise and loosening
gradually till the entire spring pressure is completely
removed.
c) Remove the secreting bolts. Now the cover assembly
and the clutch friction plate may be lifted separately.

61. CLUTCH OVERHAUL
2) Disassembling:
a) Before starting dismantling the clutch cover assembly, it is
very important to mark relative positions of various
components so that they can be reassembled easily. Mark
pressure plate, release levers and cover. Remove the
release levers along with the plate.
b) Place cover assembly under a press, with wooden block
suitably placed above and below it.
c) Apply the pressure on the cover assembly and in this
position loosen the adjusting units. Remove pressure
gradually till the clutch springs are completely free.
d) Lift of the cover to inspect various parts inside.
e) If it is required to remove the other components, mark their
positions first and remove them according to the procedure
given in manual.

62. CLUTCH OVERHAUL
2) Inspection and service:
a) Clutch Facing:
 Inspect the clutch facing for wear. In case it is worn up
to the rivet head replace it.
 There may be grease or oil on the facings. Due large
quantity of oil on facing, darken its colour of the facing
gets almost black. This causes clutch slip. Facings
has to be replaced.
b) Clutch plate springs:
 Inspect the cushioning and torsional springs for
stiffness. If they found having crack or gets week,
replace complete plate.

63. CLUTCH OVERHAUL
2) Inspection and service:
c) Pressure springs:
 Inspect the pressure springs for stiffness. If variation is
more than allowable, it should be replaced.
d) Throughout bearing:
 Clean and lubricate the bearings. Hold the inner race
and rotate the outer race, if rotation is not uniform
replace the bearings.
e) Pressure plate:
 It should have a smooth plane surface. In case it is
distorted by more than 0.3 mm, or is badly scored,
replace it.

64. CLUTCH OVERHAUL
3) Assembly:
 Grease various clutch components requiring lubrication
before reassembling.
 Place the pressure plate on the blocks placed over the
press and place pressure springs on it at suitable places.
 Fit also the release levers and place the cover over the
assembled parts, ensuring that all the parts which where
marked before disassembling are placed in their correct
positions.
 Apply pressure gradually taking the care that the bolts are
guided properly through the holes in cover.
 Tighten the nuts in proper order and with the correct
maximum torque.
 Remove the pressure by releasing the press.

65. CLUTCH OVERHAUL
4) Refitting the clutch:
 Attach the clutch cover assembly to flywheel by
means of bolts, placing the clutch plate in between the
flywheel and the cover assembly.
 Make sure that the clutch plate is centralized.
 This may be done by using a clutch alignment bar.
 Place throughout bearing on the release levers and
refit the gear box at the proper place on the vehicle
chassis.
 Refit the clutch operating linkages and check for the
pedal movement.
 In case of any excess or lesser pedal play, readjust
the same as already explained.

66. CLUTCH TROUBLESHOOTING
1) Clutch Slip:
 It is some times experienced that clutch slips while
engagement and fails to transmit completely the
engine torque.
 Large slip causes wear out or burn out of clutch
facing.
 It causes wear of flywheel face and pressure plate.
Also affects the stiffness of the springs.

67. CLUTCH TROUBLESHOOTING
1) Clutch Slip:
 This may be caused due to following reasons:
a) Incorrect linkage adjustment which causes insufficient
free pedal play. To avoid this readiust the linkage
position and free pedal play.
b) Excessive oil or grease on clutch facings due to
leakage in crankcase or gearbox or excessive
lubrication of clutch shaft. The remedy is cleaning of
components or replacement of facing.
c) Weak or broken clutch spring. Replace it.
d) Worn out facings, replace it.

68. CLUTCH TROUBLESHOOTING
2) Clutch drag or spin:
 Sometimes when clutch is to be disengaged, it is not
disengaged completely and it causes difficulty in
changing the gears. The defect is called clutch drag.
 Reasons may be as followed:
a) Excessive free pedal play. Readjust it.
b) Oil or grease on the facings. Clean the facing if it is
excessively damaged, replace facings.
c) Pressure plate damaged. Replace it.
d) Clutch plate cracked. Replace it.
e) Clutch plate may be seized on clutch splined shaft.
Clean up the splines on the shaft and lubricate it.

69. CLUTCH TROUBLESHOOTING
3) Clutch Judder:
 Sometimes as the clutch is engaged, a vibration or
judder is produced instead of smooth gradual
engagement and the vehicle suddenly jumps forward.
The possible cases are:
a) Worn out clutch facings, which must be replaced.
b) Loose rivets, replace it.
c) Distorted clutch plate. Same has to be replaced.
d) Misalignment of the pressure plate with fly wheel. This
has to be corrected.
e) Bent splined shaft. Straight it or replace it.
f) Flywheel may loose on the crankshaft flange, tight it.
g) Oil, grease or dirt on facing. Clean it or replace it.

70. CLUTCH TROUBLESHOOTING
4) Clutch Rattle:
 During clutch engagement some peculiar noise may
be observed when engine is idle. This is clutch rattle.
a) It may due to worn throughout bearing, replace it.
b) Pedal return spring may loose or disconnected.
Replace it.
c) It may due to damaged clutch plate. Replace it.
d) Clutch splined shaft may bent. Straight it or replace it.

71. CLUTCH TROUBLESHOOTING
5) Knock:
 This is abnormal noise observed when engine is idling
and the clutch is engaged. This may be due to:
a) Worn out spines of clutch shaft or clutch plate hub.
Replace them.
b) The wearing out of bearing. Replace it.

72. CLUTCH TROUBLESHOOTING
6) Pulsation of clutch pedal:
 This may be caused by the misalignment of the engine
and the transmission.
 Due to this clutch disc moves to and fro on the clutch
shaft in each revolution and this movement is
transmitted back to the pedal. This results in rapid
wear of all parts. Remedy is proper alignment of the
links.
 It may also be due to wobbling of flywheel, due to
improper mounting on crankshaft or unbalance weight.
Mount it properly or balance it or replace it.