The document discusses various types of vehicle transmission systems. It begins by defining the transmission system and its main components like the clutch, gearbox, propeller shaft, etc. It then lists the key requirements of an effective transmission system. The rest of the document focuses on different types of clutches used in vehicles - including single plate, multi-plate, cone, centrifugal, electromagnetic, and torque converter clutches. For each type, it provides details on parts, operation, applications, and advantages/disadvantages.

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2. Transmission systems
The mechanism that transmits the power developed by the engine
of automobile to the engine to the driving wheels is called the
TRANSMISSION SYSTEM (or POWER TRAIN).
It is composed of –
• Clutch
• The gear box
• Propeller shaft
• Universal joints
• Rear axle
• Wheel
• Tyres
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3. Requirements of Transmission System
• Provide means of connection and disconnection of engine with rest of power
train without shock and smoothly.
• Provide a varied leverage between the engine and the drive wheels.
• Provide means to transfer power in opposite direction.
• Enable speed reduction between engine and the drive wheels in the ratio of
5:1.
• Provide means to drive the driving wheels at different speeds when required.
• Bear the effect of torque reaction , driving thrust and braking effort effectively.
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4. Clutch
A clutch is a mechanical device that provides for
the transmission of power (and therefore usually
motion) from one component (the driving
member) to another (the driven member) when
engaged, but can be disengaged.
The clutch cover is bolted to the engine
flywheel
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5. Why Do we Need Clutch
In a car, you need a clutch because the engine spins all the time and the car
wheels don't. In order for a car to stop without killing the engine, the wheels
need to be disconnected from the engine somehow.
The clutch allows us to smoothly engage a spinning engine to a nonspinning
transmission by controlling the slippage between them. To understand how a
clutch works, it helps to know a little bit about friction.
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6. Function of Clutch
1. When the clutch is engaged, the power flows from the engine to the wheels
through the transmission system and the vehicle moves.
2. When the clutch is disengaged, the power is not transmitted to the wheels and
the vehicles stops while the engine is still running.
3. The clutch is kept engaged when the vehicle is moving.
4. The clutch also permits the gradual taking up of the load. When properly
operated, it prevents jerky motion of the vehicle.
5. The clutch is disengaged :- i) when starting the engine. ii) when shifting the
gears. iii) when stopping the vehicle. iv) when idling the engine.
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7. Principle of Operation
The clutch works on the principles of friction. When two friction
surfaces are brought in contact with each other and pressed they
are united due to the friction between them.
The friction between the surfaces depends upon:-
i) Nature of the surfaces.
ii) applied pressure.
iii) co-efficient of friction.
The two surfaces can be separated and brought into contact when
required. One surface is considered as driving member and other as
driven member. The driving member is kept rotating.
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8. Main parts of a clutch
1. Driving member
2. Driven member
3. Operating member
Driving member has a flywheel which is mounted on the engine
crankshaft. A disc is bolted to flywheel which is known as pressure plate
or driving disc.
The driven member is a disc called clutch plate. This plate can slide
freely to and fro on the clutch shaft.
The operating member consists of a pedal or lever which can be
pressed to disengage the driving and driven plate.
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9. Classification
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10. Two halves carrying projections or halves
• One half is fixed and the other can move along the axis
• Jaws of moving half enter into socket of mating half •
Eg. Square jaw, spiral jaw
Advantages
• No slip and positive engagement
• No heat during engagement/disengagement Drawbacks • Engagement only
when stationary or rotate at very low speed • High speed engagement results in
shocks
Positive Contact Clutches
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11. Friction Clutch: Single plate
Disengaged position engaged position
https://www.youtube.com/watch?v=devo3kdSPQY
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12. • A single plate clutch has one clutch plate. This
clutch works on the principle of friction. It is the most
common type of clutch used in motor vehicles.
• The clutch primarily consists of two members, one
mounted on the driving shaft and the other on the
driven shaft.
• These two shafts are parallel and concentric with
each other; one shaft is fixed to its housing while the
other is splined so that it can move axially.
• The driving torque can increase by increasing the
effective radius of contact.
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13. Pressure plate and housing
Clutch plate or friction plate
𝑇 = 𝜇𝑊𝑟 𝑚
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14. Applications
Single plate clutches are used where large radial space is available. e.g. cars, buses, and trucks.
Advantages
• The working of engagement and disengagement is very smooth in a single plate clutch.
• Power losses are very less.
• As sufficient surface area is available for heat dissipation in such clutches, no cooling oil is
required. Therefore, single plate clutches are dry type.
• Single plate clutches have a quick operation and respond fast.
• It makes it easier to change gears than a cone type.
Disadvantages
• Single plate clutches have high wear and tear rate.
• It has less torque transmitting capacity.
• The springs have to be the more stiff hence greater force requires to disengage.
• It requires high maintenance.
• The space required to accommodate the clutch is more as compared to the multi-plate clutch.
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15. Multi Plate Clutch
• In a multi plate clutch, the torque is transmitted by
friction between several pairs of co-axial annular
driving faces maintained in contact by an axial thrust.
• Both sides of each plate are lined with friction material,
so that a single-plate clutch has two pairs of driving
faces in contact.
• n = no. of pairs of driving faces.
• Then, for a plate clutch, the maximum torque
transmitted is
mWrnT 
No. of driving
pairs n = 6
https://www.youtube.com/watch?v=TcYsV063lk8
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16. Applications
• Multi-plate clutches use where compact construction is required, e.g., scooters,
motorcycles, and racing cars.
• The multi-plate clasp use in heavy commercial vehicles to transmit high torque.
Advantages
• Decrease the weight of the clutch.
• It has a very compact size.
• Increase the amount of torque transmits.
• Decrease the moment of inertia of the clutch.
Disadvantages
• They heat up quickly.
• Multi-plate clutches are heavy.
• Multi-plate clutches are too expensive.
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17. Cone clutch
A cone clutch “oldest of all” Is a type of clutch
system in which two mating members known as the
male member and the female member designed
in shape of cones are used, due to the mating of
these 2 members frictional force due to the
frictional contact between them is generated
results in torque or power transmission between
them.
Advantages of Cone Clutch:
•As compared to each other, the cone clutch is
more efficient than a single plate clutch.
•In the case of cone clutch the friction surface
experience the potential of the normal force.
Disadvantages of Cone Clutch:
•Cone clutch oftentimes inefficient to
disengage the clutch.
•This situation takes place when the angle is
more than 20°.
•Small wear can produce due to huge axial
movement.
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18. Centrifugal Clutch
For engaging clutches, Centrifugal clutch
uses the concept of centrifugal force. It is
operated automatically according to the
speed of an engine. Thus, in a vehicle, any
clutch paddle is not required for the
movement of the clutch.
https://www.youtube.com/watch?v=HrmWNBwHBQ018

19. Advantages of Centrifugal Clutch:
These are the advantages of Centrifugal Clutch:
• It is automatic.
• Low cost and also low maintenance cost.
• Less wear and tear.
• Greater control over speed.
Disadvantages of Centrifugal Clutch:
Here are some disadvantages of Centrifugal Clutch:
Sometimes, engines suffer from slippage in lower RPM.
It cannot be used in a high-speed engine.
Peak speed depends on clutch size.
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https://www.youtube.com/watch?v=5SuqyE_bXqo
Electromagnetic clutch
Electromagnetic clutches operate electrically but
transmit torque mechanically. This is why they used to
be referred to as electro-mechanical clutches.
How it works
When the clutch is actuated, current flows through
the electromagnet producing a magnetic field. The
rotor portion of the clutch becomes magnetized
and sets up a magnetic loop that attracts the
armature. The armature is pulled against the rotor
and a frictional force is generated at contact.
Within a relatively short time, the load is
accelerated to match the speed of the rotor,
thereby engaging the armature and the output hub
of the clutch. In most instances, the rotor is
constantly rotating with the input all the time.

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Disengagement
When current is removed from the clutch, the armature is free to turn with the shaft. In
most designs, springs hold the armature away from the rotor surface when power is
released, creating a small air gap.
Cycling
Cycling is achieved by interrupting the current through the electromagnet. Slippage
normally occurs only during acceleration. When the clutch is fully engaged, there is no
relative slip, assuming the clutch is sized properly, and thus torque transfer is 100%
efficient.
Applications
Machinery, Vehicles, and Diesel locomotives

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https://www.youtube.com/watch?v=z5G2zQ_3xTc
Torque Convertor
A torque converter is generally a type of fluid coupling
capable of producing torque.
• Replacement of clutch for automatic transmission
vehicle.
It has two important purposes as it transfers the engine
torque to the transmission:
• It serves as an automatic clutch so the vehicle can be
stopped with the engine running and the transmission in
gear.
• It multiplies torque while the vehicle is accelerating to
improve acceleration and pulling power.
Parts of a torque convertor
1. Impeller- Connected to the flywheel and towards the
gearbox.
2. Turbine-Facing the impeller and the main shaft of the
gear box is taken from the turbine through the impeller.
3. Stator-Between the impeller and turbine

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Operational phases
A torque converter has three stages of operation:
Stall
The prime mover is applying power to the impeller but the turbine cannot rotate. For example, in an
automobile, this stage of operation would occur when the driver has placed the transmission in gear
but is preventing the vehicle from moving by continuing to apply the brakes. At stall, the torque
converter can produce maximum torque multiplication if sufficient input power is applied (the
resulting multiplication is called the stall ratio). The stall phase actually lasts for a brief period when the
load (e.g., vehicle) initially starts to move, as there will be a very large difference between pump and
turbine speed.
Acceleration The load is accelerating but there still is a relatively large difference between impeller
and turbine speed. Under this condition, the converter will produce torque multiplication that is less
than what could be achieved under stall conditions. The amount of multiplication will depend upon
the actual difference between pump and turbine speed, as well as various other design factors.
Coupling The turbine has reached approximately 90 percent of the speed of the impeller. Torque
multiplication has essentially ceased and the torque converter is behaving in a manner similar to a
simple fluid coupling. In modern automotive applications, it is usually at this stage of operation where
the lock-up clutch is applied, a procedure that tends to improve fuel efficiency.

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The two major operating conditions of a converter are stall and coupling.
These conditions shift back and forth depending on throttle opening and
vehicle load.
FIGURE 9-12 The fluid flowing around the guide ring is called vortex flow
(a). The fluid flow around the converter is called rotary flow (b). (Courtesy
of Chrysler Corporation)

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The fluid flow from the turbine is turned to the same direction as
the impeller by the stator vanes.
The vortex flow, torque multiplication, and efficiency of a torque converter
change as the turbine speed increases relative to the impeller.

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The maximum amount of torque multiplication produced by a converter is highly dependent on
the size and geometry of the turbine and stator blades, and is generated only when the
converter is at or near the stall phase of operation. Typical stall torque multiplication ratios range
from 1.8:1 to 2.5:1 for most automotive applications.
Failure Problems
• Overheating-Continuous high levels of slippage resulting in damage to the seals that retain
fluid inside the converter.
• Stator clutch seizure- The inner and outer elements of the one way stator clutch become
permanently locked together, thus preventing the stator from rotating during the coupling
phase.
• Stator clutch breakage- A very abrupt application of power can cause shock loading of the
stator clutch, resulting in breakage.
• Blade deformation and fragmentation- If subjected to abrupt loading or excessive heating of
the converter, pump and/or turbine blades may be deformed.
• Balloning-Operating a torque converter at very high RPM may cause the shape of the
converter's housing to be physically distorted due to internal pressure.

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Fluid coupling vs Torque convertor
A fluid coupling is a two element drive that is incapable of multiplying torque, while a
torque converter has at least one extra element—the stator—which alters the drive's
characteristics during periods of high slippage, producing an increase in output
torque.
Fluid coupling - acts as a automatic clutch without torque multiplication.
Torque convertor - is essentially an automatic clutch and torque multiplication device