clutch in detail

1. POWER TRAINS
BY:NAVIN H YADAV

2.  POWER TRAINS:
General Arrangement of Clutch, Principle of
Friction clutches, Torque transmitted,
Constructional details, Fluid flywheel, Single plate,
Multi plate and Centrifugal clutches
Gear box: Necessity for gear ratios in
transmission, Synchronous gear boxes, 3,4 and 5
speed gear boxes, Free Wheeling mechanism,
Planetary gears systems, over drives, fluid
coupling and torque converters, Epicyclic gear
box, principle of automatic transmission,
calculation of gear ratios, Numerical calculations
for torque transmission by clutches.

3. Introduction
 A Transmission system uses a clutch, gear
box, propeller shaft and a differential gear to
transmit power from engine to the road wheels
 The power may be transmitted to rear or front
or all four wheels depending on the drive used
 The clutch and gear box varies the ratio of
torque output to torque input
 The propeller shaft transmits final torque to
the rear axle from gear box
 A differential gear equally distributes the final
torque between the road wheels.

4. Functions of Transmission
System
 It disconnects engine from driving wheels
when required
 The engine is connected to driving wheels
when required
 It changes ratio of torque output to torque
input, as desired
 It turns the drive through a right angle

5. Clutch
 A clutch is a mechanical
device which transmits motion
from one shaft to the other which are along a
straight line or same axis of rotation.
 A Clutch is a machine member used to connect
the driving shaft to a driven shaft, so that the
driven shaft may be started or stopped when ever
needed, without stopping the driving shaft.

6. Location of The Clutch

9. Requirements of a clutch
1. Torque transmission.---The clutch must be able to transmit
maximum torque of the engine
2. Gradual engagement----The clutch should engage gradually to
avoid sudden jerks
3. Heat dissipation---The clutch should be able to dissipate large
quantity of heat which is generated during the clutch
operation due to friction
4. Dynamic balancing---The clutch should be dynamically
balanced. This is particularly required incase of high speed
engine clutches.
5. Vibration damping ---The clutch should have suitable
mechanism to damp vibrations and to eliminate noise
produced during power transmitted.
6. Size---The clutch should be as small as possible so that it
occupies minimum space

10. 7. Inertia -- clutch rotating parts should have minimum inertia
8. Clutch free pedal play – to reduce effective clamping load on
carbon thrust bearing
9. Ease of operation – as clutch transmits higher torque , its
disengagement should not tiresome the driver
10. Lightness

11. Used
Disconnecting the engine with gear box
 When starting the engine
 When changing the gears
 When stopping the engine

12. Principle of friction clutch
operation

13. Principle of Operation
 The clutch works on the principle of friction.
 When two surfaces are brought in contact with each other
and pressed they are united due to friction between them.
 The friction depends on area of contact, pressure applied
upon them and coefficient of friction on the surface of the
material.
 The two surfaces can be separated and brought in contact
when required.
 One is considered driving member and other driven
member. The driving member is kept rotating. When the
driven member is brought in contact with the driving
member it also start rotating.
 When the driven member is separated from the driving
member, it does not revolve .

14. T=µWR
Where, W- axial load applied
µ-Coefficient of friction
T- torque transmitted
R- effective mean radius of friction surface

15. Working of a clutch
 Clutch for a drive shaft:
The clutch disc (center)
spins with the flywheel
(left). To disengage, the
lever is pulled (black
arrow), causing a white
pressure plate (right) to
disengage the green
clutch disc from turning
the drive shaft, which
turns within the thrust-
bearing ring of the
lever. Never will all 3
rings connect, with no
gaps.

16. The
Clutch

18. Types of Clutches
1. Friction Clutches:
a. Single plate clutch
b. Multi plate clutch----i)Wet ii)Dry
c. Cone clutch---i)External ii) Internal
2. Centrifugal Clutch
3. Semi-centrifugal clutch
4. Conical spring clutch or diaphragm clutch
a. Tapered finger type
b. Crown spring type
5. Positive Clutch—Dog and spline clutch
6.Hydraulic clutch
7.Electro magnetic clutch
8.Vaccum clutch
9. Over running clutch or free wheel clutch

19. Single Plate Clutch

20. Working
 It has only one clutch plate mounted on the splines of clutch
shaft.
 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 pedal is pressed, the pressure plate moves
back against the force of the springs and clutch plate
becomes free between the flywheel and the pressure plate.
 Thus, the flywheel remains rotating as long as the engine is
running and the clutch shaft speed reduces slowly and finally
stops rotating.
 As soon as the pedal is pressed, clutch is said to be
disengaged otherwise it remains engaged due to spring
forces.

21. Cover assembly of single plate
clutch

22. Multiplate Clutch

23. Working
 Multiplate clutch consist of a number of clutch plates, instead
of
only one clutch plate as incase of single plate clutch.
 As the number of clutch plates increased number of friction
surfaces which increases the capacity of the clutch to transmit
torque.
 The plates are alternately fixed to the engine shaft and
gearbox shaft.
 They are firmly pressed by strong coil springs and assembled
in a drum.
 Each of the alternate plate slides in the grooves on the
flywheel and other slides on the splines on the pressure plate.
Thus each alternate plates have inner and outer splines.
 The multi-plate clutch works in the same way as single plate
clutch, by operating the clutch pedal. Multiplate clutch is used

24. Cone clutch
Contact surface is in the form of cone

25. Centrifugal clutch

26. Working
 The centrifugal clutch uses centrifugal force instead of spring force
for keeping it in the engaged position. Also it does not require clutch
pedal to operate it.
 The clutch is operated automatically depending upon the engine
speed. The engine can be stopped in gear without stalling the
engine.
 Similarly vehicle can be started in any gear pressing the accelerator
pedal.
 It consists of weight A pivoted at B. When the engine speed
increases the weights fly off due to the centrifugal force, operating
the bell crank lever P which presses the plate C.
 The movement of the plate C presses the spring E Which ultimately
presses the clutch plate D on the flywheel against spring G. This
makes the Clutch engaged.
 The spring G keeps the clutch disengaged at low speeds at about
500 rpm. Stop H limits the movement of the weights due to the
centrifugal force.

27. Semi-Centrifugal clutch

28. Clutch operation methods
 Mechanically
 Electromagnetic operation
 Hydraulic operation
 Vacuum operation
 Clutch by wire

30. Electromagnetic clutch

31. Hydraulically operated single plate
clutch

32. Vacuum operation clutch

33. Clutch by wire
 In this system there is no mechanical link between
the clutch and the pedal
 The clutch pedal is electronically controlled by
means of an Electronic Control Unit (ECU) and an
actuator
 A sensor on the pedal measures its exact position
which is transmitted to ECU
 Information about the car’s behavior from other
sensors is also transmitted to ECU, which then
operates the clutch through the actuator
 Advantages are improved drive ability, better
pedal feel and less wear due to absence of
mechanical linkage

34. Wet clutch

35. Description Wet clutch Dry clutch
Heat
dissipation
Good Bad
Life Longer life Short
Torque
transmission
Lower Higher
Clamping force More Less
Coefficient of
friction
Less due to oil
presence
More

36. Coil spring single plate clutch

37. Diaphragm clutch

38. Advantages of diaphragm w.r.t coil
spring
 More compact means of storing energy
 Less affected by the centrifugal forces, it can
withstand higher rotational speeds whereas
coil springs distort transversely at higher
speeds
 Diaphragm acts as both clamping spring and
release lever

39. Clutch Components
 Clutch plate
 Clutch facing
 Pressure plate
 Springs
 Bearing

40. Clutch plate

41. Torsional springs and cushioning springs

42. Clutch facing
Requirement of a good clutch facing
 Good wearing properties
 Presence of good binders in it
 Cheap and easy to manufacture
 High co-efficient of friction
 High resistance to heat

43. Types of Friction materials
 Millboard type- asbestos sheet treated with certain
impregnants
 Moulded type- mixed asbestos fibers with a binding material
 Woven type- cloth with certain binders
• Solid woven variety- cloth is woven to required thickness
• Laminated variety- layers of cloth one upon the other are
held together by a binder. Stitches are provided in addition to
binders

44. Common clutch facing materials
are;
 Leather- coefficient of friction- 0.27
 Cork -0.32
 Fabric-0.4
 Asbestos -0.2
 Reybestos and Ferodo- 0.35
 Non-asbestos clutch facing

45. Design details of single plate
clutch
Uniform Pressure Intensity: P= constant
 Total axial load on clutch W= πPr(ro
2 -ri
2 )
 Total Torque Transmitted
T= 2 /3 µ W(ro
3-ri
3)/(ro
2-ri
2)
T= µWR
 Effective Mean Radius R=2/3(ro
3-ri
3)/(ro
2-ri
2)

46. Uniform Rate of Wear: Pr= constant
 Axial load on clutch W= 2πPr(ro -ri)
 Torque Transmitted
T= µ W(ro+ri)/2
T= µWR
 Effective Mean Radius R= (ro+ri)/2
T=2µWR

47. Problem-1
The engine of a car employing a single plate
friction clutch develops maximum torque of
150Nm. External diameter of the clutch plate is
1.2 times its internal diameter. Determine the
dimensions of the clutch plate and the axial force
provided by the springs. The maximum
allowable pressure intensity for the clutch
facings is 100KPa and coefficient of friction is
0.3. Assume uniform wear.

48. Problem-2
An automobile clutch has a clutch plate of
160mm inside and 240 mm outside diameter. Six
springs in the clutch provide a total force of
4.8KN, when the clutch is new and each spring
is compressed 5 mm. the maximum torque
developed by the automobile engine is 250 Nm.
Determine
i. Factor of safety for the new clutch and
ii. The amount of wear of the clutch facing that
will take place before the clutch starts
slipping. Assume coefficient of friction for the
facing is 0.3

49. Problem-3
Determine the size of the clutch plate suitable for
an Ambassador car employing a single plate
type of friction clutch and developing 37.5 KW at
4200rpm. The inside diameter of the clutch plate
is 0.6 times its outside diameter and it is to be
ensured that even after a loss of 30% of the
engine torque due to wear of the clutch facing,
the clutch does not slip. The intensity of pressure
on the facing is not to exceed 70kPa. Assume
µ=0.3

50. Problem-4
Single plate friction clutch is to be designed for an
Ashok Leyland bus developing 80.85 kW at 2400
rpm. The maximum torque developed however is
376 Nm at 1600 rpm. A maximum wear of clutch
facing of 3 mm is to be allowed, when the clutch
must transmit at least 25% excess torque. A
pressure intensity of 190kPa can be safely allowed
and ratio Inside dia/ outside dia= 0.6 is considered
reasonable.
a) Calculate clutch plate dimensions
b) If 9 springs are used and initial spring force is to
be 1.2 times the spring force after allowable
wear of 3 mm, find out the spring stiffness.
Assume µ=0.35.

51. Design details of Multi plate
clutch
If n= total number of friction plates in the multi
plate clutch, then number of pairs of contact
surfaces= (n-1)
then, Torque T= (n-1) µWR
i) For uniform pressure intensity,
T= (n-1)2 /3 µ W(ro
3-ri
3)/(ro
2-ri
2)
ii) For uniform wear rate,
T=(n-1)W(ri +ro)/2

52. Problem on Multi plate clutch
A multi plate clutch is to be designed for a motor
cycle whose engine develops maximum torque
of 13Nm at 3500rpm. The external diameter of
the clutch facings is limited to 100mm and the
inner diameter may be assumed to be 0.2 times
the external diameter. The maximum intensity of
pressure may be taken as 80kPa and µ=0.3.
Calculate the number of plates.