TRANSMISSION SYSTEMS

1. UNIT-III
TRANSMISSION SYSTEMS

2. CLUTCH
Characteristics of a clutch
• Transmission of torque
• Gradual engagement
• Dissipation of heat
• Dynamic balancing
• Vibration damping
• Size of the clutch
• Free pedal clutch play
• Non-exertive operation of disengagement

4. • Clutch is mechanism used to connect or disconnect the
engine from the rest of transmission elements
• During normal running and stationary position, it is
always in engaged condition.
• The clutch is disengaged for starting, changing gears,
stopping and idling.
• When clutch is engaged the engine will be connected to
the transmission and power flows from engine to rear
wheel through transmission system.
• When clutch is disengaged by passing the clutch pedal,
the engine will be disengaged from the transmission.
Thus power does not flow to rear wheel while the
engine is still running.
•

5. • CLUTCH:
• Functions of clutch:
• To permit the engagement or disengagement of
a gear when the vehicle is stationary and the
engine is running.
• To transmit the engine power to rear wheels
smoothly without shocks to the transmission
system when the vehicle is in motion.
• To permit the engaging of the gears when the
vehicle is in motion damaging gear wheels.

6. TYPES OF CLUTCH
1. Friction clutch
a) single plate clutch
b)Multi plate clutch
• Wet type
• Dry type
c) cone clutch
2. Centrifugal clutch
3. Semi centrifugal clutch
4. Coil pressure spring clutch
5. Conical spring clutch or diaphragm clutch
a) Tapered
b) Crown spring
6. Positive clutch- dog and spline clutch
7. Hydraulic clutch
8. Vacuum clutch
9. Electromagnetic clutch
10. Over running clutch

7. Single plate clutch

8. MULTI PLATE CLUTCH

9. WET TYPE CLUTCH

10. CONE CLUTCH

11. CENTRIFUGAL CLUTCH

12. DIAPHRAGM CLUTCH

13. HYDRAULIC CLUTCH

14. ELECTROMAGNETIC CLUTCH

15. GEAR BOX
TYPES OF GEAR BOX
1.Manual transmission
a) Sliding mesh gearbox
b) Constant mesh gear box
c) Synchromesh gear box
2. Epicyclic gear box
3. Automatic gear box
a) Hydromatic gear box
b) Toque converter gear box
Gear box is speed and torque changing device. It
changes speed and torque between engine
and driving wheels.

16. • Purposes of transmission:
• It helps the engine to disconnect from driving
wheels
• It helps the running engine to be connected to the
driving wheel smoothly and without shock
• It provided the leverage between engine and driving
wheels to be varied
• It helps to reduce the engine speed in the ratio of
4:1 incase of passenger cars and in a greater ratio in
case of heavy vehicles. Trucks and lorries
• It helps the driving wheels to be driven at different
speeds.
• It gives the relative movement between engine and
driving wheels due to flexing of the road springs.

17. • Resistances to motion:
• Air resistance: It is the resistance offered by air to
the vehicle motion. It depends the factors
• 1.Size of vehicle, Shape of vehicle, Speed of
vehicle & Wind velocity
• Gradient resistances: The component of vehicle
weight which is parallel to the plane of the road.
This component remains constant but
independent of the vehicle’s speed.
• Rolling resistance:
• Road characteristics, Tyre characteristics, Weight
of the vehicle & vehicle speed.

18. Sliding mesh gear box

19. Constant mesh gear box

20. Synchromesh gear box

21. SHIFT OR SELECTOR MECHANISM
1. FLOOR MOUNTED SHIFT MECHANISM

22. FLUID FLYWHEEL

23. • When the engine is started, driving member called impeller starts to
move inside the housing containing oil.
• Pockets of moving driving member are completely filled with oil
• The centrifugal force the oil outward radially
• The splashed oil will strike the pockets or vanes of the driven member.
• It is forced to move in the same direction
• When engine speed increases the oil which is coming out from the
pocket of the driving member strikes the pocket of the driven member
with greater force
• Thus it tends the driven member to rotate at the same speed
• Advantage:
• It gives smoother power take up
• No need of separate pedal or lever to operate
• There is no wear on moving parts
• No need of adjustment is required
• No maintenance is necessary, except maintaining required oil level
• It is simple in design
• No skill is required for operating

25. Types of propeller shaft
• Solid or open type
•Hollow or enclosed type

27. • It restricts the propeller shaft to keep inclined.
• Whenever the rear wheels absorb irregularities in the
road, the rear axle housing will move up and down by
compressing and expanding the suspension spring.
• The angle between transmission output shaft and
propeller shaft will change
• The rear axle rotation housing is in the form of arcs with
different points their centres of rotation
• The rear axle housing moves in a shorter arc when
compared to the propeller shaft
• It causes a reduction length occupied by the propeller
shaft making the angle between transmission and
propeller shaft increased.
• If any variation in the inclination of the propeller shaft
occurs the universal joints will take care of.

28. Slip joint used to between propeller shaft and universal joint
connecting the propeller shaft to compensate for this change of length
and it helps to transmit power from engine to rear axle at the same
time

29. To provide flexible connection between two rigid shafts at an
angle permits the transmission of constantly varying power
Universal joint

31. • Overdrive:
• Planetary gears are used to increase the speed.
• Sun gear driven by the planet pinion gear
• At the same time the sun gear is locked
• Speed of main shaft is increase and decrease in power to driving wheels
• minimum speed of the engine varies with different models- cut in
speed.
• Engine runs below the speed drive is directly by unlocking the sun gear
through solenoid.
• Solenoid is controlled by electrical circuit.
• When engine speed is above the cut in speed the electrical controls
having the solenoid move the pawl to engage with gear plate.
• Sun gear is locked. The power is transmitted from the transmission
main shaft to the planet pinion cage, to the ring gear and to overdrive
main shaft.
• When the pinions rotate around the stationary sun gear, the ring gear is
driven at increased speed.

34. •Drive shaft spins the Pinion gear.
•Pinion gear turns the larger ring gear
to produce gear reduction.
•Ring gear attached to differential case, hence
it rotates with the ring gear.
•Differential case spins the sun gears which
are attached to the axles.
Axles transfer the power to the wheels

36. SEMI FLOATING AXLE

37. FULL FLOATING AXLE

38. THREE QUARTER FLOATING AXLE

39. • Hotchkiss drive

40. • Rear axle drives:
• The whole of the rear axle drive unit moves
forward and vehicles is pushed when the road
wheel begin to rotate.
• Both torque and power transmitted to wheels
by the engine.
• This torque does not rotate the wheels to the
desired direction but also rotates the
differential housing in the opposite direction.
• 1. Hotchkiss drive
• 2. Torque tube drive

41. • The slip joint provides the increased length of
propeller shaft if the rear springs get deflected.
It gets deflected while driving fast and also
while braking.
• The deflection helps to improve flexibility and
damp shocks
• The driving force is transferred from the axle
casing to the front end of the spring and then
to the frame.
• Both rear end torque and driving thrust are
opposed by spring.

42. TORQUE TUBE DRIVE

43. • Torque Tube drive:
• A hollow tube encloses the propeller shaft in this type
• The tube is rigidly connected to the differential housing at one
end.
• The other end of the tube is connected to the gear box casing
by a flexible ball and socket arrangement
• Driving thrust and rear end torque are carried by a hollow tube
• The tube is used in bearing to support the propeller shaft. Only
one universal joint is enough at the gearbox.
• There is no sliding joint needed in the propeller shaft.
• Helical to torsion bar springs are used when rear end torque
and driving thrust are carried out by a torque tube
• Liminated springs are used, shackles will also be placed at both
ends
• Driving thrust is transferred to the front end of the frame
through gear box
• Hotchkiss drive, the driving thrust is transferred to the rear end
of frame thro cup and gearbox shaft.