Friction in Clutch

2. • Conical Pivot Bearing
• Trapezoidal or Truncated Conical
Pivot Bearing
• Flat Collar Bearing
• Conical Collar Bearing
Previous lecture

3. • Friction Clutches
• Disc Clutches
• Cone Clutches
• Centrifugal Clutches
Today’s lecture

4. A clutch is a mechanical device that provides for the transmission of power (and therefore
usually motion) from one component (the driving member) to another (the driven
member) when engaged, but can be disengaged.
Clutch

5. 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.

6. 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.

7. TYPES OF CLUTCHES
1) Positive contact clutches
i. jaw clutches
ii.toothed clutches
2) Friction clutches
i.Disc clutches
ii.Cone clutches
iii.centrifugal clutches

8. 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.

9. TYPES OF 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

10. TYPES OF 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

11. TYPES OF 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

12. 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

14. Clutch Disc Types
• Rigid
•Flexible

15. Clutch linkage – Mechanical
Linkage-type

16. 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.

17. 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.

18. Design of clutch plate
2R
rδ
1R
2R
1R

19. 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
1R
1R

20. 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

21. Single Plate Clutch
•Frictional resistance offered by ring is,
•Frictional torque acting on the ring is,

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

23. 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

24. Single Plate Clutch
•(1)within limit R2 to R1 we
[∵p=Constant]
R1
R2

25. …….(A)
• Equation (A) gives the torque transmitted by single plate
clutch due to friction considering uniform pressure theory.

26. 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)

27. 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,
δW= (C/r) 2 π r δr

28. Single Plate Clutch
•We know that frictional torque acting on ring is,

29. 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,
R1
R2 R1
R2

30. Single Plate Clutch
This is the torque transmitted by single plate due
to friction considering uniform wear theory.

31. Single Plate Clutch
•Power transmitted by single plate clutch is
given by,

32. 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.

33. 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.

35. For multiplate clutch
•For uniform pressure theory,
•For uniform wear theory,

36. Multi plate 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.

37. •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,

38. In mutilate disc clutch
no of disc on driving shaft
no of disc on driven shaft
So no. of pairs in contact,

39. Clutch plate

40. 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.

41.  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.

42. 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

43. Advantages: It may be made in smaller size
or require less actuating force compared with
plate clutch
Disadvantages:
For small cone angle and exposure to dust
and dirt tends to bind the two cones and it
becomes difficult to disengage them.

44. Centrifugal clutch
Centrifugal clutch
Driving
shaft
Driven
shaft
Friction lining
Total friction torque , T = n µ R (F-P)
F=mrω2
ω
ω
2
2F m r2
1P m r

46. Next
• Balancing
• Balancing of rotating masses
• Balancing of reciprocating masses

47. Contact details:
Rohit Kumar Singla
Email ID: rohit.kumar@thapar.edu