Clutch & Fluid Flywheel - CSVTU

Clutches
&
Fluid Flywheel
1
Manish RK Sahu
Asst. Professor
Department of Mechanical Engg.
Automobile
Engineering
Shri Shankaracharya Institute of
Professional Management And Technology
UNIT - 02

Introduction
A. Clutch
2
Accelerator
Brake
Clutch
A clutch is a mechanical device
which engages and disengages
power transmission especially from
driving shaft to driven shaft.
clutches connect and disconnect
two rotating shafts (drive shafts or
line shafts).

Functions of a Clutch
1. Function of transmitting the torque
from the engine to the drive train.
2. Smoothly deliver the power from the
engine to enable smooth vehicle
movement.
3. Perform quietly and to reduce drive-
related vibration.
4. Protect the drive train when given the
inappropriate use.
3

When the clutch pedal is pressed, a cable
or hydraulic piston pushes on the release
fork, which presses the throw-out bearing
against the middle of the diaphragm
spring. With the spring pushed, the clutch
disc is then disconnected from the rotating
flywheel that is attached to the engine.
When the pedal is released, the disc will
engage contact with the flywheel and
transmit the torque from the engine to the
rest of the drive train. 4
Principle of operation of Clutch

5
Principle of operation of Clutch

6
Types of Clutch
1. Friction Clutch
2. Centrifugal
Clutch
3. Semi-
Centrifugal Clutch
4. Diaphragm
Clutch
•Single Plate
•Multi-Plate
•Cone Clutch
• Tapered Fingered Type
• Crown Spring Type

7
Types of Clutch
5. Positive Clutch
6. Hydraulic Clutch
7. Vacuum Clutch
8. Diaphragm Clutch
9. Electro Magnetic
Clutch
•Dog Clutch
• Spline Clutch
• Tapered Fingered Type
• Crown Spring Type

8
1. Friction Clutch
A friction clutch plate is used in vehicles to allow the
transmission input shaft and engine to run at the same
speed when rotating. The friction that is created
between the engine and the transmission is what
provides the force required to move the vehicle.
When the clutch is engaged, the friction plate is
sandwiched between the engine flywheel and a steel
pressure plate that is bolted to the flywheel. If the
pressure between the flywheel and pressure plate is
not sufficient, it will allow the friction plate to slip and
thus the vehicle will not perform correctly

9
Types of Friction Clutches
Single Plate Clutch
• it has only one clutch plate.
Multi Plate Clutch
• This types of clutches use multiple clutches to make frictional
contact with a flywheel of the engine.
Cone Clutch
•It consists of friction surfaces in the form of cones.

10
Single Plate Clutch
Single plate clutch is the most common type
of clutch plate used in automobiles. It
consists only one clutch plate which is
mounted on the splines of the clutch plate.
The Flywheel is mounted on the engine
crankshaft and rotates with it.

12
Advantages
 Single Plate Clutch is not expensive.
 It has little maintenance.
 Gear shifting is easier compare to cone clutch
because pedal movement is less.
 Single Plate Clutch is more reliable because it
doesn't suffer from disadvantages of binding of
cone.

13
Disadvantages
 Greater force required to disengage
because the springs have to be more
stiff.

14
Applications
 Single plate clutches are used in trucks, buses,
and cars etc.
 Single plate clutches used where large radial
space is available.
 As sufficient surface area is available for the
heat dissipation in Single plate clutches, no
cooling oil is required. Therefore, single plate
clutches are dry type.

15
Multi Plate Clutch
Multi-Plate Clutch consists of a
number of clutch plates instead of
only one clutch plate like in the
Single plate clutch.
Friction surface also increased
because of a number of clutch
plates. Because of a number of
friction surfaces, The capacity of
the clutch to transmit torque is also
increased.

17
Advantages
 Multi-plate clutch transmits high torque because of the
number of friction surfaces.
 The overall diameter of Multi-plate clutch is reduced
compare to the single plate clutch and transmit the same
torque.
 It is used in commercial vehicles and racing cars to
transmit high torque.
 It is used in two wheelers where there is a limitation of
space

18
Disadvantages
Multi-plate clutches are too expensive.
Multi-plate clutches are heavy.

19
Applications
 The multi-plate clutches are used in
racing cars, and motorcycles.
 The multi-plate clutch is used in heavy
commercial vehicles to transmit high
torque

20
Cone Clutch
Cone Clutch having friction surfaces in
the form of a cone.
The engine crankshaft consists of a
female cone. The male cone is mounted
on the splined clutch shaft. Cone clutch
has friction surfaces on the conical
portion. The male cone can easily slide
on the clutch shaft.

22
Working
When the clutch is engaged (When the clutch
pedal is not pressed) the friction surfaces of the
male cone are in contact with the female cone
due to the force of the spring. The power is
transmitted from engine to transmission.
When the clutch is disengaged (When the clutch
pedal is pressed) the male cone slides against the
spring force. Now, the power does not transmit
from the engine

23
Advantages
The normal force acting on the friction surfaces is
greater than the axial force. Like in Single plate
clutch, the normal force acting on the friction
surfaces is equal to the axial force

24
Disadvantages
The main disadvantage of Cone clutch is If
the angle of the cone is made smaller than
200 the male cone tends to bind in the
female cone and it becomes difficult to
disengage the clutch.

25
Applications
 Cone clutch is used in low peripheral speed applications.
 Cone clutch is common in automobiles and other
combustion engine transmissions.
 It is also used in very specialist transmissions in racing,
rallying, or in extreme off-road vehicles.
 Cone clutches are used in power boats.
 Small cone clutches are used in synchronizer
mechanisms in manual transmissions

26
2. Centrifugal Clutch
Centrifugal Clutch uses centrifugal force
instead of spring force. This clutch is
always in engaged position.
And it does not have a clutch pedal to
operate it. Centrifugal clutch is
automatically operated with engine speed.
The vehicle can be stopped in gear without
stalling (stop running) the engine. And also
the gear can be started in any gear by
pressing the accelerator pedal.

27
Working Principle
• A centrifugal clutch works on centrifugal
force. One side of clutch connected to the
engine crankshaft and other side connected
to gearbox shaft, chain, or belt.
• As engine R.P.M. (Revolutions Per Minute)
increases, weighted arms in the clutch
swing outward and force the clutch to
engage position.
• The most common Centrifugal Clutches
have friction pads or shoes radially
mounted that engage the inside of the rim
of the housing

28
Advantages
• Centrifugal Clutch has less maintenance.
• It is not expensive.
• It does not need clutch pedal because it’s
automatic.
• It helps to prevent the engine from stalling
(stop running).

29
Disadvantages
• Due to slipping and friction, There is a loss of
power.
• It does not transfer a high amount of power
because Centrifugal clutch shoes slip in heavy
load condition.
• It causes overheating problems.
• Its engagement and disengagements depend
upon the speed of the driving shaft

30
Applications
• The centrifugal clutch is mainly used in mopeds and go-
karts.
• It is also used in mini bikes, chainsaw, and lawn mowers
etc.
• It is used in boats and paramotors to keep the engine
running during stalling (stop running) and disengage
loads during starting and idling.

31
Semi Centrifugal Clutches used in high
powered engines and racing car engines
where clutch disengagements require
appreciable and tiresome drivers effort.
The power transmitted with partly by
clutch springs and remaining by the
centrifugal action of an extra weight
provided in the system.
The clutch springs transmit power at low
engine speed and the centrifugal force
transmit power at higher engine speed
3. Semi Centrifugal Clutch

32
Advantages
• Clutch operation is very easy.
• Less stiff clutch springs are used as they
operate only at low engine speeds

33
Disadvantages
• Springs have transmitted the torque at
lower engine speeds only.
• Centrifugal forces work only at higher
engine speed to transmit torque

34
Applications
• The centrifugal clutch is mainly used in mopeds and go-
karts.
• It is also used in mini bikes, chainsaw, and lawn mowers
etc.
• It is used in boats and paramotors to keep the engine
running during stalling (stop running) and disengage
loads during starting and idling.

35
Positive clutch is a mechanical device and type of
clutch used for engage and disengage power
transmission from driving shaft to driven shaft.
Positive clutch is use where positive drive (torque
transmit without slip) is required. In positive clutch
two machine elements are used, one element is
rigidly fixed to driving shaft and other machine
element is free to slide axially on splined driven shaft
and it helps for engage or disengage clutch. Machine
elements of positive drive have jaws which help to
connect shaft (driving shaft and driven shaft). Jaws
may be in square shape, triangular shape or gear
toothed. According to use different type of jaw
machine element is used in clutch
Positive Clutch

36
Clutch friction linings are
subjected to severe
rubbing so that generation
of heat in relatively short
periods takes place.
Friction Plate Clutch Lining Material

37
Therefore, the lining material should have a combination of the
following properties to withstand the operating conditions.
(a) Relatively high coefficient of friction under entire operating
conditions.
(b) Maintenance of friction properties during entire working life.
(c) Relatively high energy absorption for short periods.
(d) Withstanding high pressure plate compressive loads.
(e) Withstanding high impacts of centrifugal force during gear
changing.

38
(f) Adequate shear strength to transmit engine torque.
(g) High level of endurance in cyclic working without
effecting friction properties.
(h) Good compatibility with cast iron facings over the entire
range of operating temperature.
(i) A high degree of tolerance against interface
contamination without affecting its friction take-up and grip
characteristics.

39

40
Calculating the Torque Transmitted by a Clutch
This calculation is about working out how much torque a clutch can transmit before it begins to slip - clutch slip.
The torque transmitted by a clutch depends on the following four factors:
The number of friction couples in contact. 'S'
The spring force of the pressure plate. 'P'
The coefficient of friction between the clutch lining and the flywheel, and the clutch lining and the pressure plate. 'μ'
'μ' is just the Greek letter 'mu'. Rather than have to write down the lengthy phrase 'co-efficient of friction' every time we want to use it,
we just substitute 'μ'.
You are already familiar when we do this with other ratios: π (Greek letter 'pi') is simply the number of times the diameter of any circle
fits into its circumference: = 3.14 (or 22/7).
The mean effective radius of the clutch disc (also called the driven plate). 'R'
The formula used for this calculation is: T=SPμR where:
T is the torque transmitted (measured in SI units, Nm)
S is the number of friction couples in contact. For example, in a single plate dry clutch, there are 2 friction couples: one between the
front of the clutch disc and the flywheel, and one between the back of the clutch disk and the pressure plate.
P Pressure plate clamping force. [Measured in newtons]
μ is the coefficient of friction between the clutch lining and the flywheel and pressure plate.
R is the mean (average) effective radius (M.E.R.) of the clutch disc, measured in metres.

Introduction
B. Fluid Flywheel
41
It is also known as Fluid clutch or fluid coupling which couples the driving
member with the driven member through a media of fluid. It consists of two
members in which one is a driving member and the other one is driven member
as shown in Figure. Among them, the driving member is connected with the
engine flywheel and the driven member is connected with the transmission
shaft. These two members are not made to contact with each other. The driven
member is free to slide on splines provided on the transmission shaft. The two
rotors are filled with a fluid of required viscosity. They also guide the fluid to
flow in the desired direction.

Working
43
When the engine is started, the driving member called the
impeller starts to move inside the housing containing oil.
Pockets of moving driving members are completely filled
with oil. Due to this, the centrifugal force forces the oil
outward radially. The pockets are designed in such a way
that the splashed oil will strike the pockets or vanes of
the driven member. Hence. it is forced to move in the
same direction. When the engine speed increases. the oil
which is coming out from the pocket of the driving
member strikes the pockets of the driven member with
greater force. Thus, it tends the driven member to rotate
at the same speed.

Advantages
44
1. It gives smoother power take-up than the centrifugal
type when the engine IS accelerated.
2. The fluid in the coupling behaves as a cushioning agent
between engine and gearbox in order to absorb shocks
during braking or coasting down on incline.
3. No need of separate pedal or lever to operate.
4. The driving member acts as a flywheel on the
crankshaft. Thus. it is smoothened out the torque
variation.
5. There is no wear on moving parts.

Advantages
45
6. No need of adjustment is required.
7. No maintenance is necessary. except maintaining the
required oil level.
8. It is simple in design.
9. There is no jerk on transmission when the gear
engages. It damps all shocks and strains.
10. No skill is required for operating.
11. Car can be stopped in gear and moved off just by
pressing the accelerator pedal itself

Disadvantages
46
1. There is a drag on the gear box-shaft even the
slip is 100%.
2. It has the gear changing difficult with the
ordinary crash type gearbox. So. the fluid
flywheel is generally used with an epicyclic
gearbox which avoids this difficulty.

Home Assignments
47
1. Difference between Friction Clutch and Centrifugal Clutch
2. Difference between fluid flywheel and Friction Clutch.
3. Positive Clutch

48
Axial load on the differential element is
δW = pressure intensity x differential area
= p x 2Π 𝑟 𝑑𝑟
Torque Transmitted by the Clutch
dr
r1
r
r2

49
Total Axial load on the clutch is
W = p x 2Π 𝑟 𝑑𝑟
𝑟2
𝑟1
W = 2Π p 𝑟 𝑑𝑟
𝑟2
𝑟1
Torque transmitted by the clutch is
T = μ x 2Π p 𝑟2 𝑑𝑟
𝑟2
𝑟1
Where μ is coefficient of friction.

50
𝑟2
𝑟1
W = Π 𝑝 (r2
2 - r1
2 )
T = μ x 2Π p 𝑟2 𝑑𝑟
𝑟2
𝑟1
T =
2
3
μ Π p (r2
3 - r1
3 )
T = μ
2
3
(r2
3 − r1
3 )
(r2
2 − r1
2 )
Π p (r2
2 - r1
2 )
A. Uniform Pressure Theory
p = constant
This assumption is essentially valid if surface of friction material is truly plane,
i.e. when the clutch is new.
R = Effective mean Radius
W
T = μ W R

51
𝑟2
𝑟1
W = 2Π 𝑝r (r2 - r1 )
T = μ x 2Π 𝑝 𝑟 r 𝑑𝑟
𝑟2
𝑟1
T = 2μ Π p (
r2
2 − r1
2
2
)
T = μ
(r2 + r1 )
2
2Π pr (r2 - r1 )
B. Uniform Wear Theory
p r = constant
This assumption is essentially valid if surface of friction material is damaged,
i.e. when the clutch is old.(Pressure distribution changes)
W
T = μ W R

52
Numerical Problem (Single Plate Clutch)
Que. – An automobile engine is developing a maximum torque of 200 Nm has
a single plate dry friction clutch. The outside dia. 1.2 times the inner diameter ,
the allowable pressure intensity for the clutch facings is 90 kPa and the
coefficient of friction is 0.3. Assuming uniform wear of lining, Determine the
dimensions of clutch plate and axial force of springs.
Solution : for uniform wear
T = 2 μ W R (2 pairs of friction surfaces)
Axial load W = 2Π 𝑝r (r2 - r1 )
pr = constant
p1r1 = p2r2
Pressure intensity will be maximum where radius is minimum.
Thus pr=p1r1 = 90 x 1000x r1

53
R =
(r2 + r1 )
2
=
(r1 + 1.2r1 )
2
= 1.1 𝑟1
W= 2 Π x 90 x 1000r1 x (1.2 r1 –r1) = 113040 r1
2
T = 2 μ W R
200 = 2 x 0.3 x 113040 r1
2 x1.1 r1
r1
3 = 2.6807 x 10-3 m3 = 2680735 mm3
r1 = 138.92 mm
d1 = 277.84 mm
d2 = 1.2 x 277.84 = 333.41 mm
W = 113040 r1
2 = 2181.5 N

54
Numerical Problem (Single Plate Clutch)
Que. – An automobile is fitted with a single plate clutch and its engine develop 35
kW of power while turning at 4000 RPM.
d1 = 0.6 d2 & the clutch must not slip with 25% loss of engine torque due to wear of
the clutch. p(allowable) = 80 kPa and μ = 0.32. determine size, R and frictional area.
Solution : for uniform wear
T [design torque] = 2 μ W R (single plate clutch) *
Power =
2Π𝑁𝑇
60
35x1000 = 2 Π
4000
60
T
T = 83.6 Nm (Its not a design torque. It is torque after power loss )*
T [design torque] = 1.25 x 83.6 = 104.5 Nm

55
Axial load W = 2Π 𝑝r (r2 - r1 )
pr = constant
p1r1 = p2r2
Pressure intensity will be maximum where radius is minimum.
Thus pr=p1r1 = 80 x 1000x r1 = 80 x 1000x 0.6x r2
R =
(r2 + r1 )
2
=
(r2+ 0.6r 2)
2
= 0.8 𝑟2
W= 2 Π x 80 x 1000x 0.6x r2 x (r2 − 0.6r 2) = 120576 r2
2
T [design torque] = 2 μ W R
104.5 = 2 x 0.32 x 120576 r2
2 x0.8 𝑟2
r2
3 = 1693000 mm3
r2 = 119 mm
r1 = 71.4 mm
R = 95.2 mm
Frictional area = Π x R2 = 28457.95 mm2

56
Numerical Problem (Multi Plate Clutch)
T = (n-1) μ W R
Where n is number of clutch plates.

58
𝑟2
𝑟1
W = Π 𝑝 (r2
2 - r1
2 )
T =
μ x 2Π
𝑠𝑖𝑛θ
p 𝑟2 𝑑𝑟
𝑟2
𝑟1
*
T = μ
2
3𝑠𝑖𝑛θ
(r2
3 − r1
3 )
(r2
2 − r1
2 )
Π p (r2
2 - r1
2 )
A. Uniform Pressure Theory
W
T = μ W R
Cone Clutch Analysis
θ = semi cone angle

59
𝑟2
𝑟1
W = 2Π 𝑝r (r2 - r1 )
T =
μ x 2Π 𝑝 𝑟
sin θ
r 𝑑𝑟
𝑟2
𝑟1
*
T = μ
(r2 + r1 )
2𝑠𝑖𝑛θ
2Π pr (r2 - r1 )
B. Uniform Wear Theory
θ = semi cone angle
W
T = μ W R

60
Numerical Problem (Cone Clutch)
Que. – A cone clutch having total included angle 30
degree transmits 15 kilowatt 1250 Revolution per
minute. the width of its face is ¼ th of its mean
diameter . the normal pressure between the contact
faces is not to exceed 90 kiloPascal. coefficient of
friction is 0.32. make calculations for the main
dimensions of the clutch and the actual force
required. assume case of uniform wear

63
Centrifugal Clutch Analysis
• Centrifugal force acting on each shoe
at the running speed ω
Fc = m ω2 r
r denotes centre of gravity of the shoe
from the centre of spider. And m is mass
of each shoe.
• Inward force exerted by the spring
on each shoe at speed ω1 at which
engagement begins to take place
Fs = m ω1
2 r
Net outward radial force = Fc – Fs
Frictional force acting tangentially (F) = μ (Fc – Fs)
Total Frictional torque (T) = μ (Fc – Fs) R x n (n = number of shoes)

64
θ
r
l
• Contact length of shoe (l)
l = R.θ
• Force with which the shoe presses against the rim
= l.b.p
b = width of shoe
p = intensity of pressure exerted on the shoe
Under Equilibrium conditions,
l.b.p = Fc – Fs
b =
Fc –Fs
𝑙.𝑝

66
 Time t elapses before the engine attains the required speed
𝑡 =
𝐼𝜔
𝑇
 Energy Supplied E1 = T𝜔t
 Energy of Flywheel E2 =
𝐼𝜔2
2
 Energy loss during slipping = E1 – E2
Some other formulae

Clutch & Fluid Flywheel - CSVTU

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