Important of clutches

2. BASIC DIFFERENCE BETWEEN
COUPLING,CLUTCHES, BRAKES
•A coupling such as a flange coupling, is a permanent connection. the driving and driven
shafts are permanently attached by means of coupling and it is not possible to disconnect the
shafts , unless the coupling dismantled.
• On the other hand , the clutch can connect or disconnect the driving and driven shafts , as
and when required by the operator.
In the operation of clutch ,the condition are follows:
•Initial condition: the driving member is rotating and the driven member is at rest.
•Final condition : both members rotate at the same speed and no relative motion.
In the operation of brake ,the condition are follows:
•Initial condition : one member such as the brake drum is rotating and the braking member
such as the brake shoe is at rest.
•Final condition : both members are at rest and have no relative motion.

3. WHAT IS CLUTCHES ?
•A clutch is a mechanical device that engages and disengages the power transmission ,
especially from driving shaft to driven shaft.
•In the simplest application, clutches connect and disconnect two rotating shafts (drive
shafts or line shafts). In these devices, one shaft is typically attached to an engine or other
power unit (the driving member) while the other shaft (the driven member) provides output
power for work.

4. 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.
Thus, clutch is nothing but a combination of two friction surfaces.

5. MAIN PARTS OF A CLUTCH
•It consists of
(a) a driving member,
(b) a driven member, and
(c) an operating member.
•Driving member has a flywheel which is mounted on the engine crankshaft. A
disc is bolted to flywheel which is known as pressure plate or driving disc.
• The driven member is a disc called clutch plate. This plate can slide freely to
and fro on the clutch shaft.
• The operating member consists of a pedal or lever which can be pressed to
disengaged the driving and driven plate.

6. TYPES OF CLUTCHES
1)Mechanical clutches
2)Pneumatic clutches
3)Hydraulic clutches
4)Electromagnetic clutches
Mechanical clutches
1)Positive contact clutches
i. jaw clutches
ii.toothed clutches
2)Friction clutches
i.Disc clutches
ii.Cone clutches
iii.centrifugal clutches

7. System Components
Flywheel: Transfers engine power to the clutch
Input shaft: Transfers power from clutch to the transmission
Clutch Disk (clutch): Splined to input shaft; transfers power from
engine to the input shaft
Pressure Plate Assembly: Spring pressure tightly holds the clutch to
the flywheel

8. Components cont:
•Release Bearing (throw-out bearing): Connected through linkage
or hydraulics to the clutch pedal; Provides a way for the pressure
plate to release pressure on the clutch
•Pilot Bearing (bushing) : Mounted in the tail of the crankshaft.
Stabilizes the input shaft. Not always used for FWD.
•Clutch Fork (if applicable): Slides the release bearing into and
away from the pressure plate assembly

10. Components cont:
•Clutch Linkage (or hydraulic plumbing): Allows the driver to
operate the clutch fork
•Clutch (bell-housing) Housing: Encloses the clutch assembly
–May be integral with the transmission or removable

11. •Mounted on the rear of the
crankshaft
•Acts as balancer for engine
•Adds inertia to the rotating
crankshaft
•Provides a surface for the
clutch to contact
•Usually surrounded by a ring
gear for electric starter
operation
Clutch Components - Flywheel

12. Flywheel Construction
•Usually constructed of
nodular cast iron which
has a high graphite content
•The graphite helps
lubricate engagement of
the clutch
•May also be constructed
from cold rolled steel

13. Clutch Disc Types
• Rigid - used primarily
for industrial/racing
applications.
•Flexible - most common,
everything from
grandma’s cruiser to
street/strip racing.

14. Flexible Clutch Disc
Hub flange - in direct contact with the input shaft
Friction ring - in direct contact with the flywheel/pressure plate.

15. Flexible Clutch Disc
Clutch facing - friction material
marcel springs - facing dampener
Torsional springs - further dampening for clutch application
Stop pins - limits the torsional spring’s travel
Rivets -fastens the facing material to marcel (springs)

16. Belleville/diaphragm Spring:

17. Spring-type Pressure Plate

18. Benefits and Disadvantages:
•Belleville/diaphragm type:
•cost effective
•uniform engagement
•limited spring pressure
•Spring:
•unlimited pressure capabilities
•as springs wear, pressure may become
inconsistent

19. Clutch Components
Release (throw-out) bearing
Operated by the clutch linkage
Presses against the pressure plate to release
the clutch

21. Clutch Components
Pilot Bearing (bushing)
•Installed (pressed) into a machined bore in the
end of the crankshaft or flywheel
•May be a bushing, ball-bearing or roller-bearing

22. Clutch linkage – Mechanical
Linkage-type

23. Clutch linkage – Mechanical
Cable-type

24. 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. Friction linings are provided on both the sides of clutch plate.

25. 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.
Transmission 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.
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. Single plate clutch is shown fig.

26. Design of clutch plate
2
R
r
δ
1
R
2
R
1
R

27. Single Plate Clutch
•W=total axial load
•R1=External radius of clutch plate
•R2=internal radius of the clutch plate
•P=intensity of pressure between contacting
surfaces.
•µ=coefficient of friction between contacting
surfaces
1
R
1
R

28. Single Plate Clutch
•Consider a elemental ring of radius ‘r’ and
thickness δr on the contacting surface.
therefore,
•Area of the ring on contacting surface is,
•Axial load on the ring is,
δW=pressure×Area of the ring
δr
r
2π
p
δW 


29. Single Plate Clutch
•Frictional resistance offered by ring is,
•Frictional torque acting on the ring is,
δW
μ
Fr 
δr
r
p
μ
2π
δr)
r
2π
μ(p
Fr 

r
2
r
r
r
δ
r
p
μ
2π
δr.r
r
p
μ
2π
T
r
F
T




30. Single Plate Clutch
•Torque transmitted by single plate clutch is
obtained by considering following two
assumptions
(a)uniform pressure theory
(b)uniform wear theory

31. Single Plate Clutch
(a)uniform pressure theory:
•Assuming that the intensity of pressure over the
entire contacting surface area is constant,
•Total torque transmitted by single plate clutch
can be obtain by integrating Equation
Then, p=constant
 
2
2
2
1 R
R
π
W
area
surface
contacting
load
p




32. Single Plate Clutch
•(1)within limit R2 to R1 we
[∵p=Constant]

 
1
2
R
R
2
T
0
r δr
r
p
μ
2π
Τ

 
1
2
R
R
2
T
0
r δr
r
p
μ
2π
Τ
 
3
2
3
1
R
R
3
R
R
p
μ
π
3
2
3
r
p
μ
2π
Τ
2
1












33. …….(A)
• Equation (A) gives the torque transmitted by single plate
clutch due to friction considering uniform pressure theory.
   
3
2
3
1
2
2
2
1
R
R
R
R
π
W
μ
π
3
2
Τ 



 








 2
2
2
1 R
R
π
W
p

 
 







 2
2
2
1
3
2
3
1
R
R
R
R
μ W
3
2
Τ

34. Single Plate Clutch
(b) Uniform Wear Theory
•In this theory, we are considering that
wear which take place is uniform over the
entire contacting surface i.e.
P.r=constant
P.r=C
P=C/r
…...(3)

35. Single Plate Clutch
•Axial load acting on the ring is
δW=p 2π r δr
δW=2 π C δr …(4)
•Integrating above Equation(4) within limit we get,
δr
C
2π
r
C
δW 
 

w
0
R
R
1
2
δr
C
2π
δW

36. Single Plate Clutch
•We know that frictional torque acting on ring is,
……….(5)
…….(6)
   
 
2
1
2
1
R
R
R
R
2π
W
C
R
R
C
2
r
C
2π
W 1
2




 
δr
r
C
μ
2π
Τ
δr
r
r
C
μ
π
2
Τ
δr
r
p
μ
2π
Τ
r
2
r
2
r





37. Single Plate Clutch
•Torque transmitted by single plate clutch can be
obtain by integrating the Equation (4 ) within the
limit R2 to R1 we get,
 
2
R
R
C
μ
2π
2
r
C
μ
2π
Τ
δr
r
C
μ
2π
Τ
δr
r
C
μ
2π
Τ
2
2
2
1
R
R
2
R
R
T
0
r
R
R
T
0
r
1
2
2
2
2
2


















38. Single Plate Clutch
•This is the torque transmitted by single plate
due to friction considering uniform wear theory.
 
 
 
 
μW
π
2
1
Τ
R
R
R
R
μW
π
2
1
Τ
R
R
R
R
2π
W
μ
π
Τ
2
1
2
2
2
1
2
2
2
1
2
1









39. Single Plate Clutch
•Power transmitted by single plate clutch is
given by,
rpm
in
shaft
of
Speed
N
where,
Watt
60
NΤ
2π
P
Τ
ω
P




40. MULTIPLATE CLUTCH
Multi-plate clutch consists of more than one clutch plates contrary to single plate
clutch which consists of only one plate. Friction surfaces are made in case of multi-
plate clutch. 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. He plates are firmly held by the force of coil springs and they assembled in a
drum.

41. 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.
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. This type
of clutch has been shown in Figure.

43. For multiplate clutch
•For uniform pressure theory,
•For uniform wear theory,
 
 








 2
2
2
1
3
2
3
1
R
R
R
R
μ W
3
2
n
Τ
 
2
1 R
R
μW
2
1
n
Τ 



44. Multiplate Clutch
Notes:
•In case of new clutch ,the intensity of pressure is uniform
along the surface of clutch but in case of old clutch
uniform theory is more correct.
•For single plate clutch normally both sides of the plate
are effective .there for single plate clutch has two pairs of
contacting surface i.e. n=2.
•In actual practice, usually the theory of uniform wear is
used in analysis of clutch.

45. •Intensity of pressure is maximum at the inner radius R2 of
the friction or contact surface,
•Intensity of pressure is minimum at the inner radius R1 of the
friction or contact surface,
2
max
2
max
R
C
P
OR
C
R
P 


1
max
1
max
R
C
P
OR
C
R
P 



46. In mutilate disc clutch
no of disc on driving shaft
no of disc on driven shaft
So no. of pairs in contact,
1
n
n
n 2
1 



1
n

2
n

47. Clutch plate

48. DIFFERENCE BETWEEN SINGLE
AND MULTI-PLATE CLUTCHES :-
The number of pairs of contacting surfaces in the single plate
clutch is one or at the most, two. These are more number of
contacting surfaces in the multi-disk clutch.
 As the number of contacting surfaces is increased, the
torque transmitting capacity is also increased, other conditions
being equal. In other words, for a given torque capacity, the
size of the multi-plate clutch is smaller than that of the single
plate clutch, resulting in compact construction.

49.  The work done by friction force during engagement is converted
into heat. More heat is generated in the multi-plate clutch due to
increased number of contacting surface. Heat dissipation is a serious
problem in the multi-plate clutch. Therefore, multi-plate clutches are
wet clutches, while single plate clutches are dry.
The coefficient of friction decreases due to cooling oil, thereby
reducing the torque transmitting capacity of the multi-plate clutch.
The coefficient of friction is high in dry single plate clutches.
 Single plate clutches are used in applications where large radial
space is a available, such as trucks and cars. Multi-disk clutches are
used in applications where compact construction is desirable, e.g.,
scooter and motorcycle.

50. Cone clutch
α = semi-apex angle of the
cone
Only one pair of driving
surfaces is possible, n =1
The maximum torque transmitted = T = μWrm cosecα

52. Centrifugal clutch
Centrifugal clutch
Driving
shaft
Driven
shaft
Friction lining
Total friction torque , T = nµR(F-P)
F=mrω2
ω
ω

54. Objectives
•Diagnose clutch problems before disassembly
•Adjust a clutch
•Install a replacement clutch
•Inspect worn or damaged clutch parts and
determine the cause of the problem

55. Introduction
•Early automobiles
–Produced with manual shift transmissions
•Required clutch
•Some new model cars and light trucks have
manual transmissions
–Utilize a clutch as well
•Common to have at least one new clutch installed
•Clutch work is not difficult to learn
•Diagnose problems before and after disassembly

56. Transmission Noise
•Sometimes noise occurs only when engine is
idling in neutral with clutch engaged
–Front transmission bearing on input shaft and
mainshaft pilot are only bearings rotating
•One of these bearings is probably the noise source

57. Pedal Problems and Slipping
Clutch
•Diagnosis on basis of pedal feel
–Pulsating pedal: something internal in clutch
–Pedal is hard to depress: binding linkage or cable
•Slipping clutch
–Tested by putting it in the highest gear range
•Several possible reasons clutch slip
–Partial engagement
–Partial disengagement

58. Dragging Clutch
•Clutch drags: does not release properly
–Disc stays attached to the flywheel
•Test for a dragging clutch
–Start engine and run it to normal operating
temperature
–Engine at idle and transmission in neutral: depress
clutch to floor
–Wait ten seconds
–Shift transmission into reverse

59. Oily Clutch Facings
•Oil leaking onto clutch disc:
–Causes clutch slipping
•Disc may overheat and burn its friction surface
•During repair:
–Disc and pressure plate are replaced
•Rest of the parts are thoroughly cleaned
–Determine and repair oil leak source
•Oil on front side of flywheel: crankshaft rear seal or
external engine leak
•Oil on rear side of flywheel: bad front transmission seal
or overfilled transmission

60. Damaged Friction Surfaces
•Damage to friction surfaces of clutch cover or
flywheel can cause clutch to slip
–Clutch slips: heat is generated
•Flywheel or pressure plate can be warped
•Flywheel, pressure plate, or disc can all become glazed
•Flywheel is commonly resurfaced

61. Chattering or Grabbing Clutch
•Chattering clutch
–Occurs when pedal shakes as clutch is engaged
•Grabbing clutch
–Occurs when friction disc does not slip normally
but grabs all at once
•Causes of clutch chatter or grabbing
–Oil on friction lining
–Worn or broken motor mounts
–Worn or bent clutch fork

62. Clutch Service
•Includes:
–Checking and adjusting free play and travel
–Hydraulic component service
–Clutch replacement
•Some clutches require adjustment
–As the disc wears, it becomes thinner
•Results in release levers moving closer to the release
bearing which means less clearance

63. Servicing Hydraulic Components
•Internal hydraulic system problems
–Usually the result of dirty or aging internal rubber
sealing parts
•Master cylinder and slave cylinder
–Either can develop leaks
•Different methods can be used to bleed air from
a clutch hydraulic system
–Gravity bleeding

64. Clutch Replacement
•Includes replacement of several parts
–Disc
–Release bearing
–Clutch cover
–Pilot bearing or bushing
–Sometimes a flywheel and/or front transmission
seal
•Often come in a clutch parts kit

65. Design and Analysis of Clutch
Using Sintered Iron as a Friction
Material
RESEARCH PAPER

66. ABSTRACT
•Clutch system is among the main systems inside a vehicle. Clutch is a
mechanical device located between a vehicle engine and its transmission and
provides mechanical coupling between the engine and transmission input shaft.
Clutch system comprise of flywheel, clutch disc plate and friction material,
pressure plate, clutch cover, diaphragm spring and the linkage necessary to
operate the clutch. The clutch engages the transmission gradually by allowing
a certain amount of slippage between the flywheel and the transmission input
shaft. However, the slipping mechanism of the clutch generates heat energy
due to friction between the clutch disc and the flywheel. At high sliding
velocity, excessive frictional heat is generated which lead to high temperature
rise at the clutch disc surface, and this causes thermo-mechanical problems
such as thermal deformations and thermo-elastic instability which can lead to
thermal cracking, wear and other mode of failure of the clutch disc component.

67. AUTOMOTIVE CLUTCH
SYSTEM
•Automotive clutches are located between the engine and the
transmission. It provides mechanical coupling between the engine
and transmission input shaft. Manual transmission cars need a
clutch to enable engaging and disengaging the transmission. The
clutch engages the transmission gradually by allowing a certain
amount of slippage between the flywheel and the transmission
input shaft (Erjavec 2005).Clutch basically consists of six major
parts: flywheel, clutch disc, pressure plate, diaphragm spring,
clutch cover and the linkage necessary to operate the clutch (Lee
and Cho 2006) as shown in Figure 1.

69. CLUTCH MATERIALS
•The clutch disc is generally made from grey cast iron (Afferante et al. 2003;
Poser et al. 2005). This is because grey cast iron has a good wear resistance
with high thermal conductivity and the production cost is low compare to other
clutch disc materials such as A1-MMC (aluminum-metal matrix composite),
carbon composites and ceramic based composites (Terhech et al. 1995; Jang et
al. 2003). High thermal conductivity of diffusivity of the material is considered
advantageous because heat is then allowed to dissipate at higher rate
(Bostwick and Szadkowski 1998). In this project, BS200 or ASTM G2500
grade grey cast iron is selected as the material for the commercial clutch disc.
Some properties of the material (BS Grade 200lASTM G2500) are shown in
Table below (Heo et al. 2002; CES EduPack 2005).

70. SINTERED FRICITON
MATERIL
•Friction pads are manufactured by sintering blend of powders
consisting of heat absorption material along with friction
generating & lubricating materials. The powders are blended in
optimized proportions & compacted to form a solid flat button of
predetermined shape. They are highly durable with harsher
engagement characteristics compared to organic linings. The
quality of materials used along with the sintering parameter play
an important role in providing the required performance
(Aleksandrova et al 1972).Particulate reinforcement gives the
necessary WEAR resistant for the sintered matrix (Mustafa Boz
& AdemKurtt2007 )

71. Method Of Analysis
•The torque that can be transmitted by a clutch is a function of its
geometry & the magnitude of the actuating force applied as well
the condition of contact prevailing between the members. The
applied force can keep the members together with a uniform
pressure all over its contact area & the consequent analysis is
based on uniform pressure condition. However as the time
progresses some wear takes place between the contacting
members & this may alter or vary the contact pressure
appropriately and uniform pressure condition may no longer
prevail. Hence the analysis here is based on uniform wear
condition.

73. Single plate clutch

80. CONCLUSION

81. CONCLUSION CONT..