Transmission system helps to transmit power to the engine of vehicle. It consist of clutch, gearbox, propeller shaft etc.

1. Subject: Automobile Engineering (AEN)
TOPIC: TRANSMISSION SYSTEM
BY
Prof. Pranit Mehata
ST. JOHN POLYTECHNIC, PALGHAR

2. INTRODUCTION
 Power developed by engine is used to turn the wheels so that the
motor vehicle can be propelled on the road.
 The mechanism that transmits the power developed by the engine of
the automobile to the driving wheels is called the transmission
system.
 It includes clutch, the gearbox, propeller shaft, universal joints,
wheel and tyres.
 The purpose of transmission is to provide high torque at the time of
starting, hill climbing, acceleration and pulling the load.

3. CLUTCH

4. CLUTCH
 A clutch is mechanism which enable the rotary
motion of one shaft to be transmitted at will to second
shaft, whose axis is coincident with that of first.
 It is located between the engine and gear box.
 When clutch is engaged the power flows from the
engine to the rear wheels through the transmission
system and the vehicle moves.
 When clutch is disengaged the power is not
transmitted from the engine to the rear wheels and the
vehicles stop but engine is still running.
The clutch is disengaged at the time of : starting the
vehicle, changing the gears and stopping the vehicle
when engine is idle.
The clutch is engaged only when the vehicle is running.

5. FUNCTION OF CLUTCH
 To permit engagement or disengagement of a gear when
the vehicle is stationary and the engine is running.
 To transmit the engine power to the road wheels smoothly
without jerk/shock to the transmission system while setting
the wheel in motion.
 To permit the engaging of gears when the vehicle is in
motion without damaging the gear wheels.

6. REQUIREMENT OF CLUTCH
 It should be easily operated.
 It should be dynamically balanced.
 It should be free from slip when engaged.
 It should engage gradually.
 It should be easily accessible and have simple means of adjustment.
 It should be as small as possible
 It should be able to dissipate large amount of heat.
 It should have suitable mechanism to damp vibrations.

7. WORKING PRINCIPLE OF CLUTCH
 The clutch principle is based on friction.
 When two friction surfaces are brought in contact with
each other and pressed they are united due to friction
between them and revolve as single unit.
 If one is revolved the other will also revolve.
 One surface is considered as driving member and other
as driven member. The driving member is kept rotating.
 When the driven member is brought in contact with
driving member, it also starts rotating. When driven
member is separated from the driving member it stops
revolving.
 This is how a clutch operates.

8. TYPES OF CLUTCH
CLUTCHES
Positive Clutch Gradual Engagement
Friction Clutch
Cone Clutch Plate Clutch
Single Plate Multiplate
Centrifugal
Clutch

9. SINGLE PLATE CLUCTH

10. MUTIPLATE CLUTCH

11. CENTRIFUGAL CLUTCH

12. DIAPHRAGM CLUTCH

13. GEAR BOX

14. INTRODUCTION
 An automobile requires high torque when climbing hills and when starting, even though
they are performed at low speeds.
 On other hand, when running at high speeds on level roads, high torque is not required
because of momentum.
 So requirement of a device is occur, which can change the vehicle’s torque and its speed
according to road condition or when the driver need.
 This device is known as transmission (Gear Box) box.

15. INTRODUCTION
 The next main component of transmission system is gearbox.
 The main function of gearbox is to provide the necessary variation to driving torque
according to operating conditions.
 The gearbox is necessary:
1. When engine is coupled to gear box a constant fixed speed is given to the vehicle
2. The gear box is provided with series of gears and shaft to obtain different speeds.
3. The gear box provides more torque on hill climbing and low torque at low speeds of engine.
4. Gear box is required to run the vehicle in reverse direction.
5. Gear box is also necessary to provide a neutral gear so that the engine power does not
transmit to the rest of the transmission line up to the wheels even the clutch is in engaged.

16. TYPES OF GEARBOX
GEAR BOX
Selective Gear Box
Constant
mesh
Gear Box
Synchrom
esh Gear
Box
Sliding
Mesh
Gear Box
Planetary Gear
Box
Epicyclic
Gear Box

17. CONSTANTMESH GEAR BOX
In this type of gear box, all the
gears are in constant mesh with the
corresponding gears on the lay
shaft.
The gears on the main shaft which
is splined are free. The dog clutches
are provided which are free to slide
on the main shaft. One dog clutch is
between the clutch gear and the
second gear while other is between
first gear and reverse gear.
The gears on the lay shaft are fixed.

18. CONSTANTMESH GEAR BOX
 For first gear (low gear) the Dog clutch D2 moves
towards left by mean of gear shift lever, it teeth
are engaged with teeth on low gear M1. A motion
is carried from clutch gear K-lay shaft A-lay shaft
gear C-main shaft gear M1-dog D2-main shaft for
final drive.
 For second gear dog clutch D1 is moves towards
right which mesh the teeth on second gear M2. A
motion is carried from clutch gear K-lay shaft A-
lay shaft gear B -main shaft gear M2 -dog D1-
main shaft for final drive.

19. CONSTANTMESH GEAR BOX
 For third gear (direct gear) the dog clutch D1
moves towards the left by selector mechanism to
mesh with teeth on clutch gear K. A motion is
carried from clutch gear K- dog D1-main shaft for
final drive.
 For reverse gear the dog clutch D2 is moved right
and mesh with teeth on M1 gear. A motion is
carried from clutch gear K-gear A- gear D-
intermediate gear I-gear M3-dog D2-main shaft
for final drive.

20. SYNCHROMESH GEAR BOX
 It consist of synchronizer which is placed between
two gears. G1 and G2 are the ring-shaped members
which are having the internal tooth that fits onto the
external teeth. F1 and F2 are the sliding members of
the main shaft. H1, H2, N1, N2, P1, P2, R1, R2 are
the friction surface.
 A spline shaft is used as the output shaft over which
the synchronizers and gears are mounted. According
to the Fig. B, C, D, E are the gears that can freely
rotate on the main shaft in mesh with corresponding
gears in the layshaft. As long as shaft A is rotating all
the gears in the main shaft and layshaft rotates
continuously.
 It is the intermediate shaft over which gears with
suitable size are mounted and is used to transmit the
rotational motion from clutch shaft to the final output
shaft. According to the Fig. U1, U2, U3, U4 are the
fixed gears on the countershaft(layshaft).

21. SYNCHROMESH GEAR BOX
 For first gear, the ring shaft member and the sliding
members i.e., G2 and F2 moves towards left till the
cones P1 and P2 rub each other. Then friction makes
their speed equal. Once their speeds are equal G2 is
further pushed towards left and it engages with the teeth
L2. A motion is carried from clutch gear B to the
layshaft gear U1. Then it goes to layshaft U3, and the
motion is moved to the main shaft gear D. From there
the motion is transferred to F2 which is the sliding
member and then to the main shaft for the final drive.
 For second gear the ring shaft and the sliding members
i.e., G1 and F1 moves towards the right till the cones N1
and N2 rub each other. Then the friction makes their
speed equal. G1 is further pushed towards the right so
that it meshes with the gear. The motion is transferred
from clutch gear B to the layshaft gear U1. From U1 the
motion is transferred to U2. From U2 it is shifted to the
main shaft gear C. Then the motion is transferred to the
sliding member F1. Then it goes to the main shaft for the
final drive.

22. SYNCHROMESH GEAR BOX
 For top gear or direct gear, the motion is shifted directly
from clutch gear B to the sliding member F1. Then from
F1 to the main shaft. This is done by moving G1 and F1
to the left.
 For reverse gear, the motion is transferred from clutch
gear A to the layshaft gear U1. From there it is
transferred to layshaft gear U4 and then to the
intermediate gear U5. From there to the main shaft gear
E and then to the sliding member F2 and then to the
main shaft for the final drive. This is done by moving G2
towards the right. Intermediate gear helps to achieve the
reverse gear.

23. OVERDRIVE
 It is the unit fitted between gearbox and
propeller shaft to permit propeller shaft
at faster speed than that in top gear.
 Overdrive are used in sport cars.
 By using this there is increase in speed
about 20 to 25 % than the maximum
engine speed.
 So advantage of this is to increase
engine life, improve fuel consumption
also reduce noise and vibration.

24. TORQUE CONVERTER
 It is a device which is used to
increase the engine torque.
 It is made up from three main
components namely impeller,
turbine and stator.
 An impeller is driving member
 A turbine is driven member
 Stator is fixed to the casing
 Whole assembly is filled with the
oil having suitable viscosity

25. EPICYCLIC GEAR TRAIN
 First gear ratio: This provide high torque ratios to
the vehicle it is obtained by fixing the ring gear
which in turn causes the planet carrier to rotate
with the power supplied to the sun gear.
 Second gear ratio: This provides high speed ratios
to the vehicle , these ratios are obtained by fixing
the sun gear which in turn makes the planet carrier
the driven member and annular the driving
member.
 Reverse gear ratio: This gear reverses the
direction of the output shaft which in turn reverses
the direction of the vehicle, this gear is achieved
by fixing the planet gear carrier which in turn
makes the annular gear the driven member and the
sun gear the driver member.

26. PROPELLER SHAFT
 It is the shaft which connects the transmission main of the output shaft to the
differential mechanism at rear wheel axles.
 It is also called as drive shaft.
 It consist of three main parts: propeller shaft, sliding joints and universal joints.
 Functions of Propeller Shaft:
1. It transmits rotary motion & power to the
differential.
2. Transmit motion at varying angles: Universal
Joint
3. Accommodates change in length: Done by sliding
Joint

27. AXLE
 An axel is a central shaft which is
used to move rotary motion to
wheels.
 For wheeled vehicle the axle may
be fixed to the wheels, rotating
with hem, or fixed to the vehicle,
with the wheels rotating around
the axel.
 An automobile has front and rear
axel

28. TYPES OF AXEL
REAR
AXLE
• Semi Floating
• Fully floating
• Three quarter
floating
FRONT
AXLE
• Dead Axle
• Live axle
STUB
AXLE
• Elliot
• Reverse Elliot
• Lamoine
• Reversed
lamoine

29. SEMI FLOATING AXLE
 In this type bearings are installed between
the axial housing and the axel shaft.
 Wheel is fitted directly to the flanged of
wheel hub at outer end of shafts by bolts,
while inner end of the axel is splines and
supported in differential.
 It has support all loads i.e. driving torque
and total weight of vehicle.
 It is the simplest and cheapest type of axel
 It is widely used in passenger cars.

30. FULLY FLOATING AXEL
 In this type of axel two taper roller bearings are used.
 Two roller bearings are between the wheel and axle
casings.
 The axal shaft is provided with flange at outer end,
which is fastened to the wheel hub by means of bolts.
 The weight of vehicle is taken by axle casing and
wheels.
 The axal shaft is only transmit the torque.
 The axle shaft may be removed from the casing
without effecting the hub and wheel.
 It is used for heavy duty vehicles such as trucks.

31. THREE QUARTER FLOATING AXEL
 In this type bearing is located between the axle casing
and the wheel hub.
 The shearing and bending stress due to weight of
vehicle is taken by axle casing.
 The axial shaft is keyed to the hub to provide torque.
 The inner end of the shaft is splined and connected to
the differential.
 The axal has to take only end loads and driving
torque.
 It is the compromise between full floating and semi
floating axle.

32. STUB AXLE
 Stub axle are connected to the front axle by king pins
 Front wheels are mounted on stub axles arrangement for
steering.
 Stub axle turns on king pin
 The stub axles are the forging of 3% nickel steel and alloy steels
containing chromium and molybdenum.
 Stub axle are of four types:
1. Elliot
2. Reversed Elliot
3. LaMoine
4. Reversed LaMoine.

33. TYPES OF STUB AXLE
 Elliot: this type uses a king pin, a yoke and
a cotter to connect to the front axle
 Reverse Elliot: this type has the opposite
arrangement of standard Elliot stub axle
 Lamoine: this stub axle type has an L-
shaped spindle instead of yoke-type hinge
 Reversed lamoine: it has the opposite
layout of standard lamoine stub axle.