A semi-centrifugal clutch uses both clutch springs and centrifugal force from weighted levers to transmit power from the engine to the clutch shaft. At low engine speeds, clutch springs engage the clutch to transmit power. At high speeds, weighted levers fly outward due to centrifugal force and exert pressure on the pressure plate, firmly engaging the clutch. This reduces the need for stiffer springs and makes clutch operation easier for the driver.

1. “A clutch
is
a mechanical device which engages
and
disengages
driving shaft
powe
r
transmissio
n
especiall
y
from
to driven
shaft.”
In the simples
t
application
,
clutche
s
connec
t
an
d
line
disconnec
t
shafts).
two rotating shaft
s
(drive shaft
s
or
In these devices, one shaft is typically attached
to an
engin
e
or other powe
r
unit (the driving
member)
while the other shaf
t
(the driven member
)
provide
s
output power for wrk.

2. The very first principle on which a clutch works is
friction.
brought
When two revolving friction surface
s
are
are
into contac
t
and presse
d,
then
they
united and start revolve at same speed due to
friction
forc
e
betwee
n
them. This is the basi
c
principle of
clutch.
The friction between these two surfaces
depends on
the area of surface, pressure applied upon
them and the friction material between them.

3. The driving membe
r
of a clutch is the flywheel
mounte
d
membe
r
on
is
the engin
e
crankshaf
t
and the driven
pressur
e
shaft.
plate mounte
d
on the
transmissio
n
Som
e
plate
s
whole
friction plates
,
sometime
s
known a
s
clutch
are kept between
these
two member
s.
This
assembly is known as the
clutch.

4. An automobile clutch has following
function:
1. It can be disengaged. This allows engine
cranking
and permits
the
engin
e
to run without delivering
power to the
transmission.
2. While disengagin
g,
it permits the driver to shift
the transmissio
n
into variou
s
gea
r
accordin
g
to
operating
condition.

5. 3. While
provide
s
on
gears,
engaging, the
clutch
slips momentarily.
this
smoot
h
engageme
nt
and lessen
s
the shoc
k
shaft and other
parts
of automobile
.
4. While engaging, the
clutch
transmits the power
to
the wheel without slipping, in ideal
condition.

6. 1. Driving
member:
It is the
member
which is directly connecte
d
to the
crankshaft. The driving member consists
of
a
cover
which carrie
s
the pressur
e
plate (driving disc)
,
the
pressure springs and the
releasing
lever. This
entire
assembl
y
is bolted on the
flywheel
and
and
rotate
s
with
engin
e
all the
the
time. The flywheel the pressur
e
plate grip driven membe
r
betwee
n
them under
the action
of
the pressure
spring.

7. 2. Driven member:
The driven member consists
of
a plate which is
free
to slide lengthwise on the splines
of
the clutch
shaft
but which drives the shaft through those splines.
This
plate is known
as
friction plate. The clutch housin
g
also includes in the driven
member.
3. Operating
member:
The operatin
g
membe
r
connects
the
driver to this
whole assembly. It consist the foot pedal, the
linkage,
the releas
e
lever and
springs
necessar
y
to ensur
e
proper operation the

9. 1. Friction Clutch
 Cone clutch
 Single plate clutch
 Multi-plate cutch
 Semi-centrifugal
clutch
 Centrifugal clutch
2. Fluid flywheel
Fluid coupling
Torque converter.

11. 1. Cone
Clutch
A con
e
clutch “oldes
t
of all” is a type of
clutch system in which two mating members
known
a
s
the mal
e
membe
r
an
d
cone
s
the
are
femal
e
membe
r
designed
in
shap
e
of used, due
to
the
mating of these two members frictional force due
to
the frictional contac
t
betwee
n
them is generate
d
results in torque or
power.
The engagement and
disengagement of
the male
and
female member
of
the cone clutch is controlled by
the

12. 1. Femal
e
Cone
-
It is the part of
a
cone
which
is
connected
to
the flywheel
of
the engine and
also
rotate
s
with it, this con
e
is having inner cutting
con
e
shape
d
groove
over
which the
male
con
e
interlocks and mak
e
frictional contac
t
with it in
order to engage the
drive.
Male Cone- It is the part
of
2. a cone clutch which
is
connecte
d
to the transmissio
n
shaf
t
and is
machined in the shape
of
a solid cone over
which
frictional material is
attached.

13. 3. Spring – Normal thrust spring located behind
the
mal
e
con
e
is use
d
for engageme
nt
and
disengagement
of
the
clutch.
4. Shafts- The female cone which is directly
attached
to the flywheel is mounted over a solid shaft.
5. Sleeves
-
Sleeve
s
having
inner
spline
s
attache
d
to
is
the mal
e
cone
mounted
over
the
splined
shaft
used for the to and fro motion of the male
cone.
6. Pedal
–
A clutch peda
l
operate
d
by the driver is
used for input regarding the engagement and
the
disengagement
of
the
clutch.

16. 1.Les
s
wea
r
and tear compar
e
to positiv
e
displacement clutch.
2. It is silent in operation.
3. The normal force acting on the
contact
surface
is
larger than the axial force generated by the
springs.
4. Comparatively
higher
torque ca
n
be transmitted
than same size
of
plate
clutch.

17. 1. Operation
of
the clutch is highly depended on
the
con
e
angle
.
If the cone
angle
is smalle
r
than
20
degree, it becomes difficult to disengage the
clutch.
2. Frequent maintenance required because the
small
amoun
t
of wea
r
on
the
con
e
surfac
e
results
in
a
considerabl
e
inner cone.
amoun
t
of the axial movemen
t
of the

19. 2. Single Plate
Clutch
It is a type of friction clutch in which powe
r
is
transmitted
by
means
of
friction between the
contact
surface usually called clutch
plates.
As nam
e
sugges
t
a this clutch consist
s
of only on
e
clutch plate with both sid
e
friction lining (frictional
surface
).
These surfaces have high
Coefficient of
friction.
Single
plate clutch also called dry clutch because no
lubricant
is used as coolant.

20. 1. Clutch
plate:
In single plate clutch only one
clutch
plate is used
.
Clutch plate is main component
of
clutches. It is
thin
dis
c
type metallic
plate
having both sid
e
frictional
surface
s.
materia
l
without
Frictional surfaces on plate must be
of
suc
h
to provid
e
friction for transmitting torque
sleeping
.
The coefficien
t
of friction of
contact surfaces should be high for proper
connection
without slipping. Clutch plate is assemble
d
in
between flywheel and pressure
plate.

21. 2. Pressure
plate:
The
pressure
iron. It
helps
maintain
the flywheel
and
plate which is generally made up
of
cas
t
in applying pressure on clutch plates
to
proper
clutch
contact between the surfaces
of
plate
by
means
of
spring
which
are attached to
it.
3. Springs:
Springs are used to maintain the pressure on
pressure plate for proper connection between
clutch plate and
flywheel and prevent the slipping
of
contact
surfaces.

24. 4.
Flywheel:
Flywheel is attached
to
engin
e
output an
d
its other
side comes in contact with clutch plate when
pressure
is applied by the pressure plate.
Operating
mechanism:
This
includes
foot pedal
,
linkage
,
bearin
g
and
lever
etc
.
All
these
component
s
are connecte
d
in a
sequence. Foot pedal is
located
a lever mechanism is
attached
inside the
automobiles;
with foot pedal
which
transmit the motion from pedal
to
spring by mean
s
of thrust
bearings.

25. A lever is attached to the paddle which is
responsible
for the force transmission from the paddle.
When peda
l
is presse
d
spring is compresse
d
and
engine is free to move without any
load.
Lever is
attached
in such
a
manne
r
when
we
pres
s
the clutch paddle thrust bearing moves forward
and
pressure plate moves backward or it moves away
from
the flywheel; due to this the connection between
the
clutch plate and flywheel release
d
and shaft
s
are
disengage

26. This time we can
easily
change
gears
in cas
e
of
automobiles. Again if we want to engage the
shafts
just release the clutch paddle; then springs
attached
to the pressure plate push the pressure plate
forward.

27. The working of the single plate clutch is smooth
i.e.
the engagement and disengagement is very
smooth in
operation
Less slip occurs in it; slip is occurs only at the
time
of engagement after engagement no slip occurs
and
the functioning becomes very smooth.
Power losses are very less.
Less heat generates because only single plate is
used.
Heat generatio
n
create
s
proble
m
in powe
r
transmission and can damage the working
parts.

28. It has less torque transmitting
capacity.
It ha
s
bigger in siz
e
even
for
transmitting
less
torque
.
It require
s
high maintenanc
e
becaus
e
they are dry
clutches
and
it is
any
necessar
y
leakag
e
to
of
preven
t
them from
moisture
machinery
.
or lubricant/oil in
Singl
e
plate clutche
s
hav
e
high wea
r
and tear rate
and have less smooth engagement.
Applications:
These are used in large size automobiles where
radial

30. 3. Multi Plate
Clutch
As nam
e
sugges
t
a this clutch consist
s
of only on
e
clutch plate with both sid
e
friction lining (frictional
surface). A multi-plate clutch is a type
of
clutch that
the
also
,
transmits more power
from
the
engine
to
transmission shaft
of
an automobile vehicle
and
makes up for the torque loss due to
slippage.
Heavy
purpos
e
machinery
,
commerci
al
vehicles
,
specia
l
military vehicles
,
racing car
s
and bike
s
us
e
this type
of
clutch.

31. Scooter
s
and motor-
cycles
us
e
multi-plate clutche
s
due to limited space in
their
gearboxe
s.
Multiple clutches consist
of
more than three discs
or
plates so that it is able to provide more torque
output.

33. 1.
2.
3.
Spring type Multi-Plate Clutch
Diaphragm type Multi-Plate
Clutch
Hydraulic Operate
d
or Automati
c
Transmissio
n
Multi-Plate Clutch
1. Spring type Multi-Plate Clutch: In this type
of
Multi-Plate Clutch, a cover is bolted to the
flywheel.
Multiple
plates
of
with the
clutch plate is found on the cover. The
outer
the clutch apply thrust on the inner
plates
help
of
clutch springs or thrust springs
to
form a drive, thereby engaging the
plates.

34. For the clutch disengagemen
t,
the mechanis
m
withdraws the end plate to compress the
springs
and
this
releas
e
type
of
the other plates
.
Old cars
and
bikes
use
clutch.
2.
of
Diaphrag
m
type Multi-Plate Clutch
:
This type
clutch consist
s
of a
special
crown shape
d
finger
type spring, that is why the name diaphragm
type. It
doe
s
not com
e
with thrust spring
s
or clutches
.
During
bears
engagement of the
clutch,
the diaphrag
m
agains
t
the outer ring and during
the
inner
clutch.
disengagement, the reaction load is
bear by
ring. Modern bikes and cars use this

35. 3. Hydraulic Operated or Automatic
Transmission
Clutch: Automatic transmission vehicles use this
type
of clutch. A hydraulic devic
e
containin
g
highly
compressed fluid operating with the accelerated
pedal
is attached to the multi-plate clutch. The
engagement
an
d
the disengagement
of
the clutch
plates
are
receive
d
with the
by the hydraulic device which is
controlled
accelerator
pedal.

37. 4. Semi Centrifugal
Clutch
“Sem
i
Centrifugal Clutche
s
use
d
in high
wher
e
powere
d
clutch
engine
s
an
d
racing car engine
s
disengagemen
ts
require appreciabl
e
an
d
tiresom
e
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 spring
s
transmit powe
r
at low engin
e
spee
d
and the centrifugal forc
e
transmit powe
r
at
higher engine
speed.

38. Beside
s
clutch, pressure
plate
and spline
s
shaf
t
it
mainly consists
of:
1.
2.
3.
4.
5.
Compression spring (3
numbers)
Weighted levers (3 numbers)
Engine Shaft
Flywheel
Clutch Shaft

39. When the engine at low speed the spring keeps
the
clutch
engaged
to transmit power,
the
weighte
d
levers do not have
any
pressure on the pressure
plate.
When
lever
s
keep
s
engine
at
high spee
d
the weights fly off and
exert pressur
e
on the pressur
e
plate which
the clutch firmly engage
d
to transmit high
torque
.
Thus instea
d
of having more stiff spring
s
for
keeping the
clutch
engage
d
firmly at high
speeds,
they are less because centrifuga

40. weighted levers,
so
that the driver may not
get
any
strain in operating the
clutch.
when the engine speed decreases, the
weights fall
and
the weighted levers do not exert any pressure on
the
pressure plate and only spring pressure is
exerted on
the pressure plate to keep the clutch engaged.

42. Advantages
1. Clutch operation is very
easy.
2. Les
s
stiff clutch spring
s
are use
d
a
s
they operat
e
only at low engine
speeds.
Disadvantages
1. Springs have
transmitted speeds only.
the
torque
at lower
engine
2. Centrifugal forces work only at higher engine
speed to
transmit torque.

44. 5. Centrifugal
Clutch
“Centrifugal
Clutch
use
s
centrifuga
l
forc
e
instea
d
of
spring force. This clutch is always in engaged
position.”
and it does not
have
a clutch pedal to operate
it.
Centrifugal clutch is automaticall
y
operate
d
with
gea
r
engin
e
spee
d.
The vehicl
e
ca
n
be stopped
in
without stalling (stop running) the engine. And also
the
gea
r
ca
n
be starte
d
in any gea
r
by pressin
g
the
accelerator
pedal.

45. 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)
weighted arms in the clutch swing
outward
the clutch to engage position.
increase
s,
and
force
The most common
Centrifugal
pads or shoes radially
mounted
Clutches have
friction
that engage the
inside
of the rim of the
housing.

46. On the center shaft (Driving or input shaft) there
are
an assorte
d
amoun
t
of extensio
n
springs
,
which
connect to a clutch
shoe.
When the cente
r
shaf
t
(Driving shaft
)
spin
s
fast
enough, the springs extend causing the clutch
shoes
to engage the friction face.
It can be compared to a drum brake in reverse
order.
The weighte
d
arm
s
forc
e
thes
e
disk
s
together and
engage the clutch and power
transmitted.

47. When the engin
e
Per
shaf
t
reache
s
a certain RPM
(Revolution
s
Minute), the clutch activate
s,
variabl
e
working almos
t
like a continuousl
y
transmission
.
As the load increase
s
the R.P
.M.
drops
thereb
y
disengaging the clutch and letting the RPM rise
again
and reengaging the clutch.

50. Advantage
s
1.
2.
3.
4.
Centrifugal Clutch has less maintenance.
It is not expensive.
It does not need clutch pedal because it’s
automatic.
It help
s
to prevent the engin
e
from stalling (stop
running).
Disadvantage
s
1.
2.
3.
Due to slipping and friction, There is a loss of
power.
It causes overheating problems.
Its engagement and disengagements depend
upon the
speed
of
the driving
shaft.

51. 1. The centrifugal clutch is mainly used in mopeds
and
go-karts.
2. It is also
used
etc.
in mini
bikes,
chainsaw,
and
lawn
mower
s
3. It is use
d
in
boats
an
d
Para-
motors
to keep
the
engin
e
running during stalling (stop running) an
d
disengage loads during starting and
idling.

52.  In this type of clutch, the flywheel consists of winding.The current
supplied in the winding from the battery or dynamo. When the current
passes through the winding, it produces an electromagnetic field
which attracts the pressure plate, thereby engaging the clutch. When
the supply is cut-off, the clutch is disengaged.
Electromagnetic Clutch

53. It consists of a vacuum cylinder with piston, solenoid
operate 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
form the battery and the circuit incorporates a switch which
is placed in the gear lever.
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.
Vacuum Clutch

55.  The hydraulic clutch is operated in the same way as the vacuum clutch.
Only the difference is that it is operated by oil pressure whereas the
vacuum clutch is operated by vacuum.
 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.
 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
the disengaged.
 As soon as the driver leaves the gear lever, the switch is open which
closed the control valve and the clutch is engaged.
Hydraulic Clutch