AE- unit 3.ppt TRANSMISSION SYSTEMS , GEAR BOXES
kpsamy
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81 slides
Mar 12, 2025
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About This Presentation
Clutch, Gear box, Torque Convertor, Fluid Coupling
Slide Content
UNIT III
TRANSMISSION SYSTEMS
TRANSMISSION SYSTEMS
INTRODUCTION
General Overview
•Transfers power from the engine to the wheels for vehicle propulsion.
•Includes components like the clutch, gearbox, propeller shaft, universal joint,
differential, and drive wheels.
Key Components & Functions
•Clutch – Engages/disengages engine power smoothly.
•Gearbox – Reduces engine speed and increases torque.
•Universal Joint – Connects shafts at angles for smooth power transmission.
•Differential – Allows wheels to rotate at different speeds during turns.
Purposes of the Transmission System
•Ensures smooth power engagement.
•Reduces and controls engine speed.
•Enables power transfer at different angles.
•Allows differential wheel speeds.
•Acts as a safety device by preventing overload damage.
General Overview
•Transfers power from the engine to the wheels for vehicle propulsion.
•Includes components like the clutch, gearbox, propeller shaft, universal joint,
differential, and drive wheels.
Key Components & Functions
•Clutch – Engages/disengages engine power smoothly.
•Gearbox – Reduces engine speed and increases torque.
•Universal Joint – Connects shafts at angles for smooth power transmission.
•Differential – Allows wheels to rotate at different speeds during turns.
Purposes of the Transmission System
•Ensures smooth power engagement.
•Reduces and controls engine speed.
•Enables power transfer at different angles.
•Allows differential wheel speeds.
•Acts as a safety device by preventing overload damage.
CLUTCH
Definition and Function
•Connects or disconnects the engine from the transmission system.
•Located between the engine and gearbox.
•Engaged during normal running; disengaged using the clutch pedal for
starting, stopping, and gear shifting.
Principle of Friction Clutch
•Works on the friction principle:
–Disengaged Position – No contact, no power transmission.
–Engaged Position – Friction between surfaces transmits torque.
•Torque transmission depends on:
–Applied pressure
–Coefficient of friction
–Flange radius
» (a)Disengaged position(b) Engaged Position
Definition and Function
•Connects or disconnects the engine from the transmission system.
•Located between the engine and gearbox.
•Engaged during normal running; disengaged using the clutch pedal for
starting, stopping, and gear shifting.
Principle of Friction Clutch
•Works on the friction principle:
–Disengaged Position – No contact, no power transmission.
–Engaged Position – Friction between surfaces transmits torque.
•Torque transmission depends on:
–Applied pressure
–Coefficient of friction
–Flange radius
» (a)Disengaged position(b) Engaged Position
CLUTCH
Functions of a Clutch
•Allows smooth gear engagement/disengagement.
•Transmits engine power without shocks.
•Prevents gear damage during motion.
Characteristics of a Good Clutch
•Transmits maximum engine torque.
•Ensures smooth, jerk-free engagement.
•Efficient heat dissipation.
•Balanced to reduce vibration.
•Compact design for minimal space usage.
•Includes free pedal play to reduce wear.
•Built-in damping to minimize noise and vibrations.
•Easy operation for the driver.
Functions of a Clutch
•Allows smooth gear engagement/disengagement.
•Transmits engine power without shocks.
•Prevents gear damage during motion.
Characteristics of a Good Clutch
•Transmits maximum engine torque.
•Ensures smooth, jerk-free engagement.
•Efficient heat dissipation.
•Balanced to reduce vibration.
•Compact design for minimal space usage.
•Includes free pedal play to reduce wear.
•Built-in damping to minimize noise and vibrations.
•Easy operation for the driver.
CLUTCH-TYPES
1.Friction clutch
1.Single plate clutch
2.Multi-plate clutch
•Wet clutch
•Dry clutch
3.Cone clutch
•Internal cone clutch
•External cone clutch
2.Centrifugal clutch
3.Semi centrifugal clutch
4.Coil pressure spring clutch
5.Conical spring clutch or diaphragm clutch
•Tapered spring clutch
•Crown spring clutch
6.Positive clutch-dog and spline clutch
7.Hydraulic clutch
8.Vacuum clutch
9.Electromagnetic clutch
10.Over running clutch.
1.Friction clutch
1.Single plate clutch
2.Multi-plate clutch
•Wet clutch
•Dry clutch
3.Cone clutch
•Internal cone clutch
•External cone clutch
2.Centrifugal clutch
3.Semi centrifugal clutch
4.Coil pressure spring clutch
5.Conical spring clutch or diaphragm clutch
•Tapered spring clutch
•Crown spring clutch
6.Positive clutch-dog and spline clutch
7.Hydraulic clutch
8.Vacuum clutch
9.Electromagnetic clutch
10.Over running clutch.
Single Plate Clutch
Definition & Usage
•Connects the engine to the transmission system.
•Commonly used in cars, trucks, and tractors.
Main Components
•Flywheel – Mounting surface, rotates with crankshaft, dissipates heat.
•Pilot Bearing – Supports transmission input shaft, prevents wobbling.
•Clutch Plate – Provides friction for power transmission, has torsion springs for
cushioning.
•Pressure Plate – Applies force on clutch plate to transmit torque.
•Clutch Cover Assembly – Houses pressure plate, springs, and release
mechanism.
•Release Mechanism – Operates clutch engagement/disengagement.
•Withdrawal Force & Bearing – Transfers force from clutch pedal to release
mechanism.
•Clutch Shaft – Transmits power from engine to gearbox.
Definition & Usage
•Connects the engine to the transmission system.
•Commonly used in cars, trucks, and tractors.
Main Components
•Flywheel – Mounting surface, rotates with crankshaft, dissipates heat.
•Pilot Bearing – Supports transmission input shaft, prevents wobbling.
•Clutch Plate – Provides friction for power transmission, has torsion springs for
cushioning.
•Pressure Plate – Applies force on clutch plate to transmit torque.
•Clutch Cover Assembly – Houses pressure plate, springs, and release
mechanism.
•Release Mechanism – Operates clutch engagement/disengagement.
•Withdrawal Force & Bearing – Transfers force from clutch pedal to release
mechanism.
•Clutch Shaft – Transmits power from engine to gearbox.
Single Plate Clutch
Single Plate Clutch
Clutch plate or disc plate:Pressure plate:
Clutch plate or disc plate:Pressure plate:
Single Plate Clutch
Working
•When engaged, friction between the flywheel, clutch plate, and
pressure plate allows power transmission to the gearbox.
•Pressing the clutch pedal moves the pressure plate away,
disengaging the clutch and stopping power transfer (declutching).
•Releasing the pedal re-engages the clutch, restoring power
transmission.
Advantages:
–It makes easy to change gears than a cone type.
–It is reliable than a cone clutch.
Disadvantages:
–Requires more force to operate.
–Takes up more space than multi-plate clutch.
Working
•When engaged, friction between the flywheel, clutch plate, and
pressure plate allows power transmission to the gearbox.
•Pressing the clutch pedal moves the pressure plate away,
disengaging the clutch and stopping power transfer (declutching).
•Releasing the pedal re-engages the clutch, restoring power
transmission.
Advantages:
–It makes easy to change gears than a cone type.
–It is reliable than a cone clutch.
Disadvantages:
–Requires more force to operate.
–Takes up more space than multi-plate clutch.
Multi Plate Clutch
Definition & Usage
•Multi-plate clutches are used in heavy vehicles, racing cars, and motorcycles
where high torque transmission is required.
•Compared to single plate clutches, they offer smoother operation and easier
engagement due to multiple friction surfaces.
•Suitable for applications where space is limited but high power transmission is
needed.
Increased Torque Transmission
•More clutch plates = More friction surfaces = Greater torque transmission.
•A small multi-plate clutch can transmit
the same torque as a single plate clutch
of twice the diameter.
•Ideal for compact, high-performance
applications.
Definition & Usage
•Multi-plate clutches are used in heavy vehicles, racing cars, and motorcycles
where high torque transmission is required.
•Compared to single plate clutches, they offer smoother operation and easier
engagement due to multiple friction surfaces.
•Suitable for applications where space is limited but high power transmission is
needed.
Increased Torque Transmission
•More clutch plates = More friction surfaces = Greater torque transmission.
•A small multi-plate clutch can transmit
the same torque as a single plate clutch
of twice the diameter.
•Ideal for compact, high-performance
applications.
Multi Plate Clutch
Types of Multi-Plate Clutches
•Wet Clutch:
–Operates in an oil bath for cooling and lubrication.
–Commonly used in automatic transmissions to reduce wear and
overheating.
•Dry Clutch:
–Operates without oil, creating more direct friction.
–Found in performance-focused vehicles where immediate power transfer
is needed.
Construction & Arrangement
•Similar in design to a single plate clutch but with multiple clutch plates.
•Clutch plates are arranged in two sets:
–One set slides in flywheel grooves.
–The other set slides on pressure plate hub splines.
•Plates are pressed together by a strong coil spring and housed in a drum.
Types of Multi-Plate Clutches
•Wet Clutch:
–Operates in an oil bath for cooling and lubrication.
–Commonly used in automatic transmissions to reduce wear and
overheating.
•Dry Clutch:
–Operates without oil, creating more direct friction.
–Found in performance-focused vehicles where immediate power transfer
is needed.
Construction & Arrangement
•Similar in design to a single plate clutch but with multiple clutch plates.
•Clutch plates are arranged in two sets:
–One set slides in flywheel grooves.
–The other set slides on pressure plate hub splines.
•Plates are pressed together by a strong coil spring and housed in a drum.
Multi Plate Clutch
Working Mechanism
•Engaged State: Pressure from the spring presses the clutch plates together,
transmitting power from the engine to the transmission.
•Disengaged State: Pressing the clutch pedal releases the pressure, allowing the
clutch plates to separate and stopping power transmission.
•Works on the same principle as a single plate clutch but provides higher
efficiency and torque capacity.
Advantages of Multi-Plate Clutch
•Higher Torque Transmission
•Compact Size
•Smooth Operation
•Efficient Cooling (Wet Clutch)
Disadvantages of Multi-Plate Clutch
•Higher Cost
•More Wear & Tear (Dry Clutch)
•Complex Design
Working Mechanism
•Engaged State: Pressure from the spring presses the clutch plates together,
transmitting power from the engine to the transmission.
•Disengaged State: Pressing the clutch pedal releases the pressure, allowing the
clutch plates to separate and stopping power transmission.
•Works on the same principle as a single plate clutch but provides higher
efficiency and torque capacity.
Advantages of Multi-Plate Clutch
•Higher Torque Transmission
•Compact Size
•Smooth Operation
•Efficient Cooling (Wet Clutch)
Disadvantages of Multi-Plate Clutch
•Higher Cost
•More Wear & Tear (Dry Clutch)
•Complex Design
Cone Clutch
Definition & Construction
•A cone clutch derives its name from the conical contact surfaces between its
components.
•It consists of two cones:
–Male Cone (splined on the driven shaft/gearbox shaft).
–Female Cone (fixed with the driving shaft/flywheel).
•The friction surfaces of these cones are typically lined with leather or other
high-friction materials.
•Figure illustrates the structural details of a cone clutch.
Definition & Construction
•A cone clutch derives its name from the conical contact surfaces between its
components.
•It consists of two cones:
–Male Cone (splined on the driven shaft/gearbox shaft).
–Female Cone (fixed with the driving shaft/flywheel).
•The friction surfaces of these cones are typically lined with leather or other
high-friction materials.
•Figure illustrates the structural details of a cone clutch.
Cone Clutch
Working Principle
•Engaged Position:
–The male cone is fully inserted into the female cone.
–Friction surfaces make full contact, allowing power transmission from
the engine to the gearbox.
–The pressure springs keep the male cone pressed into the female cone at
all times.
•Disengaged Position:
–When the clutch pedal is pressed, the male cone slides backward,
compressing the spring and breaking contact.
–Power transmission stops, disengaging the engine from the gearbox.
Advantages of Cone Clutch
✅ Higher Normal Force ✅ Lower Operating Effort
✅ less axial force ✅ Better Grip & Less Slippage
Disadvantages of Cone Clutch
❌
Binding Issue
❌
Wear Sensitivity
❌
Not Commonly Used
Working Principle
•Engaged Position:
–The male cone is fully inserted into the female cone.
–Friction surfaces make full contact, allowing power transmission from
the engine to the gearbox.
–The pressure springs keep the male cone pressed into the female cone at
all times.
•Disengaged Position:
–When the clutch pedal is pressed, the male cone slides backward,
compressing the spring and breaking contact.
–Power transmission stops, disengaging the engine from the gearbox.
Advantages of Cone Clutch
✅ Higher Normal Force ✅ Lower Operating Effort
✅ less axial force ✅ Better Grip & Less Slippage
Disadvantages of Cone Clutch
❌
Binding Issue
❌
Wear Sensitivity
❌
Not Commonly Used
Centrifugal Clutch
Definition & Working Principle
•A centrifugal clutch operates automatically based on engine speed and is
controlled by the accelerator.
•When engine speed increases, centrifugal force causes the clutch to engage.
•When engine speed decreases, the clutch disengages automatically.
•Greater centrifugal force = Stronger engagement between driving and driven
members.
Definition & Working Principle
•A centrifugal clutch operates automatically based on engine speed and is
controlled by the accelerator.
•When engine speed increases, centrifugal force causes the clutch to engage.
•When engine speed decreases, the clutch disengages automatically.
•Greater centrifugal force = Stronger engagement between driving and driven
members.
Centrifugal Clutch
Construction
Two Main Components:
–Driving Member – Connected to the engine shaft, consists of:
•Spider (hub)
•Shoes with friction lining
•Springs (holding shoes inward)
–Driven Member – A drum enclosing the driving member, connected to the
driven shaft.
Engagement Process
•At low speed – The springs hold the shoes inward, and the clutch remains
disengaged.
•As speed increases – The shoes move outward due to centrifugal force and contact
the inner surface of the drum.
•At high speed – The friction force locks the driving and driven members, making
them rotate together.
•When speed decreases – The centrifugal force reduces, the springs pull the shoes
inward, and the clutch disengages.
Construction
Two Main Components:
–Driving Member – Connected to the engine shaft, consists of:
•Spider (hub)
•Shoes with friction lining
•Springs (holding shoes inward)
–Driven Member – A drum enclosing the driving member, connected to the
driven shaft.
Engagement Process
•At low speed – The springs hold the shoes inward, and the clutch remains
disengaged.
•As speed increases – The shoes move outward due to centrifugal force and contact
the inner surface of the drum.
•At high speed – The friction force locks the driving and driven members, making
them rotate together.
•When speed decreases – The centrifugal force reduces, the springs pull the shoes
inward, and the clutch disengages.
Centrifugal Clutch
Advantages of Centrifugal Clutch
✅ Automatic Operation
✅ Smooth Power Transmission
✅ Simple & Compact Design
✅ Less Wear & Tear
Disadvantages of Centrifugal Clutch
❌
Less Torque Transmission
❌
Slippage at Low Speed
❌
Limited Use – Mostly used in lightweight vehicles and low-speed
applications.
Applications of Centrifugal Clutch
??????
Two-wheelers without gears (e.g., mopeds, scooters).
??????
Lawnmowers and small agricultural machinery.
??????
Go-karts and small automatic vehicles.
Advantages of Centrifugal Clutch
✅ Automatic Operation
✅ Smooth Power Transmission
✅ Simple & Compact Design
✅ Less Wear & Tear
Disadvantages of Centrifugal Clutch
❌
Less Torque Transmission
❌
Slippage at Low Speed
❌
Limited Use – Mostly used in lightweight vehicles and low-speed
applications.
Applications of Centrifugal Clutch
??????
Two-wheelers without gears (e.g., mopeds, scooters).
??????
Lawnmowers and small agricultural machinery.
??????
Go-karts and small automatic vehicles.
Semi Centrifugal Clutch
Definition & Working Principle
•Semi-centrifugal clutches work similarly to centrifugal clutches, but with the
addition of light pressure springs.
•The pressure between clutch plates increases with higher rotational speed.
•Uses weights linked to the pressure plate to enhance engagement force as
speed increases.
Definition & Working Principle
•Semi-centrifugal clutches work similarly to centrifugal clutches, but with the
addition of light pressure springs.
•The pressure between clutch plates increases with higher rotational speed.
•Uses weights linked to the pressure plate to enhance engagement force as
speed increases.
Semi Centrifugal Clutch
Construction
Main Components:
–Flywheel – Connected to the engine.
–Pressure Plate – Applies pressure on the clutch plate.
–Weights – Attached to the pressure plate, move outward due to
centrifugal force.
–Light Clutch Pressure Springs – Provide low pressure at idling speed,
making it easier to operate.
–Release Levers & Throw-out Bearing – Assist in disengaging the clutch
for gear shifting.
Working Mechanism
•At low speed – Light clutch springs exert low pressure, making it easy to press the clutch pedal.
•As speed increases – Centrifugal force moves the weights outward, increasing the pressure on the
pressure plate.
•At high speed – The additional force from weights enhances the clutch engagement, transmitting
more power.
•When the clutch pedal is pressed – The release levers move, reducing pressure and disengaging the
clutch.
Construction
Main Components:
–Flywheel – Connected to the engine.
–Pressure Plate – Applies pressure on the clutch plate.
–Weights – Attached to the pressure plate, move outward due to
centrifugal force.
–Light Clutch Pressure Springs – Provide low pressure at idling speed,
making it easier to operate.
–Release Levers & Throw-out Bearing – Assist in disengaging the clutch
for gear shifting.
Working Mechanism
•At low speed – Light clutch springs exert low pressure, making it easy to press the clutch pedal.
•As speed increases – Centrifugal force moves the weights outward, increasing the pressure on the
pressure plate.
•At high speed – The additional force from weights enhances the clutch engagement, transmitting
more power.
•When the clutch pedal is pressed – The release levers move, reducing pressure and disengaging the
clutch.
Semi Centrifugal Clutch
Advantages of Semi-Centrifugal Clutch
✅ Reduced Pedal Effort
✅ Automatic Load Adjustment
✅ Better Torque Transmission
✅ Longer Clutch Life
Disadvantages of Semi-Centrifugal Clutch
❌
More Complex Mechanism
❌
Limited Applications
Applications of Semi-Centrifugal ClutchRacing cars
??????
Heavy-duty vehicles
??????
Performance motorcycles
Advantages of Semi-Centrifugal Clutch
✅ Reduced Pedal Effort
✅ Automatic Load Adjustment
✅ Better Torque Transmission
✅ Longer Clutch Life
Disadvantages of Semi-Centrifugal Clutch
❌
More Complex Mechanism
❌
Limited Applications
Applications of Semi-Centrifugal ClutchRacing cars
??????
Heavy-duty vehicles
??????
Performance motorcycles
Diaphragm Clutch
Construction:
Similar to a single plate clutch but uses diaphragm (Belleville) springs instead of
coil springs.
Working Mechanism:
•Engaged Position: The diaphragm spring applies pressure to the clutch plate,
ensuring contact with the flywheel.
•Disengaged Position: When the pedal is pressed, the diaphragm spring pivots,
releasing pressure from the clutch plate.
Construction:
Similar to a single plate clutch but uses diaphragm (Belleville) springs instead of
coil springs.
Working Mechanism:
•Engaged Position: The diaphragm spring applies pressure to the clutch plate,
ensuring contact with the flywheel.
•Disengaged Position: When the pedal is pressed, the diaphragm spring pivots,
releasing pressure from the clutch plate.
Positive Clutch
Construction:
Consists of a driving member and a driven member with a sliding sleeve having
two sets of internal splines.
Working Mechanism:
•Engaged Position: The sliding sleeve moves forward, and its larger splines
match with the external dog clutch teeth, locking the shafts together.
•Disengaged Position: The sleeve moves back, disconnecting the driving and
driven shafts.
Construction:
Consists of a driving member and a driven member with a sliding sleeve having
two sets of internal splines.
Working Mechanism:
•Engaged Position: The sliding sleeve moves forward, and its larger splines
match with the external dog clutch teeth, locking the shafts together.
•Disengaged Position: The sleeve moves back, disconnecting the driving and
driven shafts.
Positive Clutch
Features:
•Used to lock two shafts together or lock a gear to a shaft.
•Requires a synchronizing mechanism for smooth engagement.
•Ensures rigid and direct power transmission without slippage.
•Simple in construction and operation.
•Used in high-torque applications, such as gearboxes and industrial machinery.
Features:
•Used to lock two shafts together or lock a gear to a shaft.
•Requires a synchronizing mechanism for smooth engagement.
•Ensures rigid and direct power transmission without slippage.
•Simple in construction and operation.
•Used in high-torque applications, such as gearboxes and industrial machinery.
Hydraulic Clutch
Purpose: Used when mechanical linkage is impractical or when high clutch
spring pressure makes mechanical operation difficult.
Construction: Consists of a master cylinder, slave cylinder, and oil reservoir.
Working Mechanism:
•When the clutch pedal is pressed, fluid pressure from the master cylinder
moves to the slave cylinder.
•The slave cylinder push rod operates the clutch release fork, disengaging the
clutch.
Advantages:
•Reduces driver effort by multiplying
force through hydraulics.
•Eliminates mechanical linkages,
reducing wear and friction.
•Flexible hydraulic lines allow easy
routing at any angle.
•Provides smooth and efficient clutch
operation.
•Ideal for heavy-duty vehicles and
machinery requiring high force
transmission.
Purpose: Used when mechanical linkage is impractical or when high clutch
spring pressure makes mechanical operation difficult.
Construction: Consists of a master cylinder, slave cylinder, and oil reservoir.
Working Mechanism:
•When the clutch pedal is pressed, fluid pressure from the master cylinder
moves to the slave cylinder.
•The slave cylinder push rod operates the clutch release fork, disengaging the
clutch.
Advantages:
•Reduces driver effort by multiplying
force through hydraulics.
•Eliminates mechanical linkages,
reducing wear and friction.
•Flexible hydraulic lines allow easy
routing at any angle.
•Provides smooth and efficient clutch
operation.
•Ideal for heavy-duty vehicles and
machinery requiring high force
transmission.
Electro-Magnetic Clutch
Construction:
Consists of a flywheel with electric winding, a pressure plate, and a gearbox
shaft with splines.
Working Mechanism:
•Engagement: When electric current passes through the winding, the pressure
plate moves towards the flywheel due to armature attraction, engaging the clutch.
•Disengagement: When the current is cut off, the pressure plate separates,
disengaging the clutch.
Construction:
Consists of a flywheel with electric winding, a pressure plate, and a gearbox
shaft with splines.
Working Mechanism:
•Engagement: When electric current passes through the winding, the pressure
plate moves towards the flywheel due to armature attraction, engaging the clutch.
•Disengagement: When the current is cut off, the pressure plate separates,
disengaging the clutch.
Electro-Magnetic Clutch
Advantages:
•Remote operation possible as no mechanical linkages are required.
•Engaging force increases with engine speed, ensuring smooth clutch operation.
•Suitable for automatic and high-speed applications.
Disadvantages:
•High heat production due to armature current.
•Expensive initial cost compared to mechanical clutches
Advantages:
•Remote operation possible as no mechanical linkages are required.
•Engaging force increases with engine speed, ensuring smooth clutch operation.
•Suitable for automatic and high-speed applications.
Disadvantages:
•High heat production due to armature current.
•Expensive initial cost compared to mechanical clutches
Vaccum Clutch
Construction:
•Consists of a vacuum cylinder, solenoid valve, reservoir, and non-return
valve.
Working Mechanism:
•Engagement: When the gear lever switch is open, the solenoid valve remains at
the bottom, keeping the clutch engaged by spring force.
•Disengagement: When the gear lever switch is closed, the solenoid valve pulls
up, connecting one side of the vacuum cylinder to the reservoir. This creates
vacuum pressure, moving the piston and disengaging the clutch.
Construction:
•Consists of a vacuum cylinder, solenoid valve, reservoir, and non-return
valve.
Working Mechanism:
•Engagement: When the gear lever switch is open, the solenoid valve remains at
the bottom, keeping the clutch engaged by spring force.
•Disengagement: When the gear lever switch is closed, the solenoid valve pulls
up, connecting one side of the vacuum cylinder to the reservoir. This creates
vacuum pressure, moving the piston and disengaging the clutch.
Vaccum Clutch
Advantages:
•Uses engine manifold vacuum, reducing the driver's effort.
•No mechanical linkages required, allowing for smoother operation.
•Ideal for automatic or semi-automatic transmissions.
Disadvantages:
•Complex system compared to mechanical clutches.
•Less effective at high altitudes, where vacuum pressure is lower.
Advantages:
•Uses engine manifold vacuum, reducing the driver's effort.
•No mechanical linkages required, allowing for smoother operation.
•Ideal for automatic or semi-automatic transmissions.
Disadvantages:
•Complex system compared to mechanical clutches.
•Less effective at high altitudes, where vacuum pressure is lower.
Gear Box
Definition:
•A gearbox is a speed and torque-changing device that transmits power from the
engine to the driving wheels by varying the gear ratio.
Necessity:
•Provides high torque during starting, hill climbing, acceleration, and heavy load
pulling.
•Helps overcome resistances acting on the vehicle.
•Allows the engine to run at optimum speed while the wheels adjust progressively.
Purposes:
•Disconnects the engine from driving wheels when needed.
•Ensures smooth connection between engine and wheels without shock.
•Varies leverage between engine and wheels.
•Reduces engine speed (e.g., 4:1 ratio in passenger cars, higher for heavy vehicles).
•Allows driving wheels to run at different speeds.
•Accommodates relative movement between engine and wheels due to road
flexing.
Definition:
•A gearbox is a speed and torque-changing device that transmits power from the
engine to the driving wheels by varying the gear ratio.
Necessity:
•Provides high torque during starting, hill climbing, acceleration, and heavy load
pulling.
•Helps overcome resistances acting on the vehicle.
•Allows the engine to run at optimum speed while the wheels adjust progressively.
Purposes:
•Disconnects the engine from driving wheels when needed.
•Ensures smooth connection between engine and wheels without shock.
•Varies leverage between engine and wheels.
•Reduces engine speed (e.g., 4:1 ratio in passenger cars, higher for heavy vehicles).
•Allows driving wheels to run at different speeds.
•Accommodates relative movement between engine and wheels due to road
flexing.
Gear Box
TYPES OF GEARBOX
•There are many types of gearboxes. Generally, it can be classified
as follows.
•Manual transmission
Sliding mesh gearbox
Constant mesh gearbox
Synchromesh gearbox
•Epicyclic gearbox
•Automatic transmission
Hydramatic gearbox
Torque converter gearbox.
TYPES OF GEARBOX
•There are many types of gearboxes. Generally, it can be classified
as follows.
•Manual transmission
Sliding mesh gearbox
Constant mesh gearbox
Synchromesh gearbox
•Epicyclic gearbox
•Automatic transmission
Hydramatic gearbox
Torque converter gearbox.
Sliding Mesh Gearbox
Definition:
•A simple manual transmission system using spur gears, where gears slide to engage
with each other.
Construction:
•Consists of a main shaft, countershaft (lay shaft), and an idler gear.
•Uses three forward gears and one reverse gear.
Working Mechanism:
•Neutral: No motion is transmitted to the output shaft.
•First Gear: Gear (5) meshes with low-speed gear (4) for high torque and low speed.
•Second Gear: Gear (6) meshes with gear (3) for moderate speed and torque.
•Third Gear (Top Gear): Gear (6) directly connects with clutch gear (1), making
input and output shafts rotate together.
•Reverse Gear: Gear (5) meshes with idler gear (8) to reverse the rotation.
Disadvantages:
•Noisy operation due to direct gear engagement.
•Difficult gear shifting, requiring double clutching technique.
•Not used in modern vehicles due to inefficiency and wear.
Definition:
•A simple manual transmission system using spur gears, where gears slide to engage
with each other.
Construction:
•Consists of a main shaft, countershaft (lay shaft), and an idler gear.
•Uses three forward gears and one reverse gear.
Working Mechanism:
•Neutral: No motion is transmitted to the output shaft.
•First Gear: Gear (5) meshes with low-speed gear (4) for high torque and low speed.
•Second Gear: Gear (6) meshes with gear (3) for moderate speed and torque.
•Third Gear (Top Gear): Gear (6) directly connects with clutch gear (1), making
input and output shafts rotate together.
•Reverse Gear: Gear (5) meshes with idler gear (8) to reverse the rotation.
Disadvantages:
•Noisy operation due to direct gear engagement.
•Difficult gear shifting, requiring double clutching technique.
•Not used in modern vehicles due to inefficiency and wear.
Sliding Mesh Gearbox
First or low speed gear Second gear
Sliding mesh gearbox
Third or top gear Reverse gear
First or low speed gear Second gear
Sliding mesh gearbox
Third or top gear Reverse gear
Constant Mesh Gearbox
Definition:
•A type of manual transmission in which all gears remain constantly meshed, and dog
clutches are used for engaging and disengaging gears.\
Construction:
•Dog clutches (D & D )
₁ ₂
on the main shaft engage different gears.
•All gears on the countershaft are fixed and always in mesh.
•Helical gears are used for smooth operation (except the reverse gear, which is spur
type).
Working Mechanism:
•First Gear: Dog clutch D
₁
moves left to engage gear (7), transmitting power from (1)
→ (2) → (4) → (7) → D .
₁
•Second Gear: D disengages, and
₁
D moves right
₂
to lock with gear (8), transmitting
power from (1) → (2) → (3) → (8) → D .
₂
•Third (Top) Gear: D moves left
₂
to directly engage clutch gear (1), allowing direct
power transfer.
•Reverse Gear: D disengages, and
₂
D moves right
₁
to engage gear (6) through the
idler gear (5), reversing shaft rotation.
Definition:
•A type of manual transmission in which all gears remain constantly meshed, and dog
clutches are used for engaging and disengaging gears.\
Construction:
•Dog clutches (D & D )
₁ ₂
on the main shaft engage different gears.
•All gears on the countershaft are fixed and always in mesh.
•Helical gears are used for smooth operation (except the reverse gear, which is spur
type).
Working Mechanism:
•First Gear: Dog clutch D
₁
moves left to engage gear (7), transmitting power from (1)
→ (2) → (4) → (7) → D .
₁
•Second Gear: D disengages, and
₁
D moves right
₂
to lock with gear (8), transmitting
power from (1) → (2) → (3) → (8) → D .
₂
•Third (Top) Gear: D moves left
₂
to directly engage clutch gear (1), allowing direct
power transfer.
•Reverse Gear: D disengages, and
₂
D moves right
₁
to engage gear (6) through the
idler gear (5), reversing shaft rotation.
Constant Mesh Gearbox
First gear Second gear Third gear Reverse gear
First gear Second gear Third gear Reverse gear
Constant Mesh Gearbox
Advantages Over Sliding Mesh Gearbox:
•Uses helical gears for smoother operation.
•Synchronizers can be added for easy gear shifting.
•Less gear damage as only dog clutch teeth wear out.
•Reduces gear noise and improves durability.
Disadvantages:
•Double clutching is required, making shifting harder.
•More complex and costly than sliding mesh gearboxes.
•Less efficient compared to a synchromesh gearbox.
Advantages Over Sliding Mesh Gearbox:
•Uses helical gears for smoother operation.
•Synchronizers can be added for easy gear shifting.
•Less gear damage as only dog clutch teeth wear out.
•Reduces gear noise and improves durability.
Disadvantages:
•Double clutching is required, making shifting harder.
•More complex and costly than sliding mesh gearboxes.
•Less efficient compared to a synchromesh gearbox.
Synchromesh Gearbox
Definition:
•A gearbox that allows smooth gear shifting without gear clashing by
synchronizing the speed of engaging gears. It replaces dog clutches with
synchromesh units for seamless gear engagement.
Construction & Working:
•Uses helical gears for quieter operation.
•Synchromesh units synchronize gear speeds before engagement.
•Sleeves and cones ensure smooth shifting by equalizing the speed of the gears
before meshing.
•Generally used in higher gears (e.g., 2nd, 3rd, and 4th gears).
•Reverse and first gears lack synchromesh units and can only be engaged when
the vehicle is stationary.
Definition:
•A gearbox that allows smooth gear shifting without gear clashing by
synchronizing the speed of engaging gears. It replaces dog clutches with
synchromesh units for seamless gear engagement.
Construction & Working:
•Uses helical gears for quieter operation.
•Synchromesh units synchronize gear speeds before engagement.
•Sleeves and cones ensure smooth shifting by equalizing the speed of the gears
before meshing.
•Generally used in higher gears (e.g., 2nd, 3rd, and 4th gears).
•Reverse and first gears lack synchromesh units and can only be engaged when
the vehicle is stationary.
Synchromesh Gearbox
Advantages:
1.Easy and smooth gear shifting without the need for double clutching.
2.Less wear and tear on gears.
3.Quieter operation due to the use of helical gears.
Disadvantages:
1.Complex design, making repairs and maintenance difficult.
2.Higher initial cost than constant mesh or sliding mesh gearboxes.
3.Quick gear shifting may still cause noise due to improper engagement.
Advantages:
1.Easy and smooth gear shifting without the need for double clutching.
2.Less wear and tear on gears.
3.Quieter operation due to the use of helical gears.
Disadvantages:
1.Complex design, making repairs and maintenance difficult.
2.Higher initial cost than constant mesh or sliding mesh gearboxes.
3.Quick gear shifting may still cause noise due to improper engagement.
Epicyclic Gearbox
Definition:
•An advanced type of gearbox where at least one gear (planet gear) rotates around
its own axis and also around another axis, unlike ordinary gear systems.
Working Principle:
•The sun wheel is fixed to a shaft and rotates freely.
•The planet wheel rotates both around its axis and around the sun wheel.
•The annulus (ring gear) remains stationary, allowing different gear ratios.
Definition:
•An advanced type of gearbox where at least one gear (planet gear) rotates around
its own axis and also around another axis, unlike ordinary gear systems.
Working Principle:
•The sun wheel is fixed to a shaft and rotates freely.
•The planet wheel rotates both around its axis and around the sun wheel.
•The annulus (ring gear) remains stationary, allowing different gear ratios.
Epicyclic Gearbox
Construction:
•Uses planetary gears inside a ring gear for compactness.
•No sliding gears; gear shifting is controlled by brakes and clutches instead.
•Compound gears enable multiple speed ratios and reverse gear.
Advantages:
•Constant mesh of planetary gears, eliminating gear slippage.
•Uses smaller clutches and brakes for gear shifting.
•More compact and lighter than traditional gearboxes.
•Even load distribution over multiple gear wheels increases durability.
•Higher gear tooth contact area, reducing wear and improving efficiency.
•Smaller size compared to three or four-speed gearboxes while maintaining high
performance.
Construction:
•Uses planetary gears inside a ring gear for compactness.
•No sliding gears; gear shifting is controlled by brakes and clutches instead.
•Compound gears enable multiple speed ratios and reverse gear.
Advantages:
•Constant mesh of planetary gears, eliminating gear slippage.
•Uses smaller clutches and brakes for gear shifting.
•More compact and lighter than traditional gearboxes.
•Even load distribution over multiple gear wheels increases durability.
•Higher gear tooth contact area, reducing wear and improving efficiency.
•Smaller size compared to three or four-speed gearboxes while maintaining high
performance.
Automatic Gearbox
Definition:
•A gearbox that automatically selects and shifts gears without manual input from the
driver. The driver only selects basic modes like neutral, forward, or reverse.
Working Principle:
•No need for a clutch pedal or gear shift lever.
•The system automatically selects the appropriate gear based on speed and throttle
position.
•Uses hydraulic, centrifugal, or electronic controls to shift gears.
Types of Automatic Gearboxes:
•Hydramatic Transmission:
–Uses planetary gear sets for power transmission.
–A centrifugal governor selects gears based on speed and throttle position.
–Hydraulic pistons and springs control gear shifting.
•Torque Converter Transmission:
–Uses fluid coupling and a torque converter for smooth gear shifting.
–Works with an epicyclic gear arrangement for automatic speed control.
–Combines different units to function seamlessly.
Definition:
•A gearbox that automatically selects and shifts gears without manual input from the
driver. The driver only selects basic modes like neutral, forward, or reverse.
Working Principle:
•No need for a clutch pedal or gear shift lever.
•The system automatically selects the appropriate gear based on speed and throttle
position.
•Uses hydraulic, centrifugal, or electronic controls to shift gears.
Types of Automatic Gearboxes:
•Hydramatic Transmission:
–Uses planetary gear sets for power transmission.
–A centrifugal governor selects gears based on speed and throttle position.
–Hydraulic pistons and springs control gear shifting.
•Torque Converter Transmission:
–Uses fluid coupling and a torque converter for smooth gear shifting.
–Works with an epicyclic gear arrangement for automatic speed control.
–Combines different units to function seamlessly.
Automatic Gearbox
Hydramatic Transmission:
Overview:
•Hydramatic transmission is a fully automatic system with a four-speed forward
and reverse geared mechanism, using a fluid flywheel and planetary gears for
smooth power transmission.
Key Components & Functions:
•Planetary Gear Sets: Three sets used for power transmission, with two
providing four forward speeds.
•Fluid Flywheel: Reduces engine torque reactions and cushions automatic shifts.
•Hydraulic Control: Brake bands and clutches control gear shifts based on
throttle position and a centrifugal governor.
•Gear Selection: Controlled via a lever on the steering column with positions—
Neutral, Drive, Low, and Reverse.
Hydramatic Transmission:
Overview:
•Hydramatic transmission is a fully automatic system with a four-speed forward
and reverse geared mechanism, using a fluid flywheel and planetary gears for
smooth power transmission.
Key Components & Functions:
•Planetary Gear Sets: Three sets used for power transmission, with two
providing four forward speeds.
•Fluid Flywheel: Reduces engine torque reactions and cushions automatic shifts.
•Hydraulic Control: Brake bands and clutches control gear shifts based on
throttle position and a centrifugal governor.
•Gear Selection: Controlled via a lever on the steering column with positions—
Neutral, Drive, Low, and Reverse.
Automatic Gearbox
Hydramatic Transmission:
Gear Operations:
•First Gear: Maximum gear ratio; power transmission through planetary gears
for smooth acceleration.
•Second Gear: Direct drive in the front unit; power transferred via fluid flywheel.
•Third Gear: Engages clutch and rear unit, with power split 40% through fluid
coupling and 60% via intermediate shaft.
•Fourth Gear: Direct drive achieved by locking clutch and releasing bands,
minimizing slippage.
•Reverse Gear: Uses an additional planetary gear set for reversing motion.
•Neutral Gear: Disconnects engine power from the output shaft.
Hydramatic Transmission:
Gear Operations:
•First Gear: Maximum gear ratio; power transmission through planetary gears
for smooth acceleration.
•Second Gear: Direct drive in the front unit; power transferred via fluid flywheel.
•Third Gear: Engages clutch and rear unit, with power split 40% through fluid
coupling and 60% via intermediate shaft.
•Fourth Gear: Direct drive achieved by locking clutch and releasing bands,
minimizing slippage.
•Reverse Gear: Uses an additional planetary gear set for reversing motion.
•Neutral Gear: Disconnects engine power from the output shaft.
Automatic Gearbox
Advantages of Hydramatic Transmission:
•Simplified driving with no clutch pedal.
•Reduces driver fatigue.
•Smooth gear shifts without jerks.
•Better acceleration and hill-climbing performance.
•Fuel-efficient and reduces wear and tear.
•Noise-free gear shifting.
•Increased transmission lifespan.
Advantages of Hydramatic Transmission:
•Simplified driving with no clutch pedal.
•Reduces driver fatigue.
•Smooth gear shifts without jerks.
•Better acceleration and hill-climbing performance.
•Fuel-efficient and reduces wear and tear.
•Noise-free gear shifting.
•Increased transmission lifespan.
Gear Shift or
Selector Mechanism
1.Floor Mounted Shift Mechanism:
Selector Mechanism: Used for shifting gears easily using a gear shift lever.
Mounting: Gear shift lever is positioned on the floorboard and ball-mounted in
the gearbox cover.
Movement: The lever allows movement in any direction for gear selection.
Selector Sleeve & Rods:
•Lower end of the gear lever fits into a slot in the selector sleeve.
•Forks mounted on three separate selector rods guide the gear movement.
•Selector rods are supported in the gearbox casing for stability.
•Avoiding Unwanted Engagement:
•Slots on selector rods prevent accidental engagement of gears.
•Spring-loaded balls oppose movement until sufficient force is applied.
•Gear Engagement Process:
•Transverse motion of the gear lever selects the required fork.
•Longitudinal movement of the fork engages the desired gear.
•Fork & Gear Interaction:
•Selection forks fit into grooves on gear bosses for smooth operation
Selector Mechanism
1.Floor Mounted Shift Mechanism:
Selector Mechanism: Used for shifting gears easily using a gear shift lever.
Mounting: Gear shift lever is positioned on the floorboard and ball-mounted in
the gearbox cover.
Movement: The lever allows movement in any direction for gear selection.
Selector Sleeve & Rods:
•Lower end of the gear lever fits into a slot in the selector sleeve.
•Forks mounted on three separate selector rods guide the gear movement.
•Selector rods are supported in the gearbox casing for stability.
•Avoiding Unwanted Engagement:
•Slots on selector rods prevent accidental engagement of gears.
•Spring-loaded balls oppose movement until sufficient force is applied.
•Gear Engagement Process:
•Transverse motion of the gear lever selects the required fork.
•Longitudinal movement of the fork engages the desired gear.
•Fork & Gear Interaction:
•Selection forks fit into grooves on gear bosses for smooth operation
Gear Shift or
Selector Mechanism
1.Floor Mounted Shift Mechanism:
Selector Mechanism
1.Floor Mounted Shift Mechanism:
Gear Shift or
Selector Mechanism
2. Steering column mounted gear shift mechanism:
•Mounting: Gear lever rod is placed on the steering column for easy access.
•Engagement Mechanism:
•A tongue on the gear lever rod engages the forks through axial movement.
•Angular movement of the gear shift lever enables gear selection in the
gearbox.
•Gear Selection Process:
•First & Second Gear:
•Lever is moved upward from neutral.
•Then moved radially forward or backward to engage the gear.
•Third & Fourth Gear:
•Lever is moved downward from neutral.
•Then moved radially forward or backward for selection.
•Reverse Gear:
•Knob is pulled outward, then lever is pushed downward in neutral.
•Moved to the extreme position and then backward to engage
reverse gear.
Selector Mechanism
2. Steering column mounted gear shift mechanism:
•Mounting: Gear lever rod is placed on the steering column for easy access.
•Engagement Mechanism:
•A tongue on the gear lever rod engages the forks through axial movement.
•Angular movement of the gear shift lever enables gear selection in the
gearbox.
•Gear Selection Process:
•First & Second Gear:
•Lever is moved upward from neutral.
•Then moved radially forward or backward to engage the gear.
•Third & Fourth Gear:
•Lever is moved downward from neutral.
•Then moved radially forward or backward for selection.
•Reverse Gear:
•Knob is pulled outward, then lever is pushed downward in neutral.
•Moved to the extreme position and then backward to engage
reverse gear.
Gear Shift or
Selector Mechanism
2. Steering column mounted gear shift mechanism:
Selector Mechanism
2. Steering column mounted gear shift mechanism:
OVERDRIVES
Definition & Purpose:
•Overdrive is a device used to increase the gear ratio in a vehicle.
•It allows the transmission output shaft to turn faster than the input shaft.
•Mounted between the transmission and the propeller shaft.
•Provides higher cruising speed with lower engine RPM (reducing it by 20-
25%).
•Reduces wear, vibration, noise, and improves fuel efficiency.
Functionality:
•Overdrive is typically used only in top gear but can be applied to other gears in
sports cars.
•Helps achieve higher torque ratios by increasing the number of available speeds.
•Four-speed and five-speed transmissions often include overdrive.
•In some designs, overdrive can be manually or automatically operated.
Definition & Purpose:
•Overdrive is a device used to increase the gear ratio in a vehicle.
•It allows the transmission output shaft to turn faster than the input shaft.
•Mounted between the transmission and the propeller shaft.
•Provides higher cruising speed with lower engine RPM (reducing it by 20-
25%).
•Reduces wear, vibration, noise, and improves fuel efficiency.
Functionality:
•Overdrive is typically used only in top gear but can be applied to other gears in
sports cars.
•Helps achieve higher torque ratios by increasing the number of available speeds.
•Four-speed and five-speed transmissions often include overdrive.
•In some designs, overdrive can be manually or automatically operated.
OVERDRIVES
Operation of Overdrive:
•Engaging Overdrive:
–Car must be running above a set cut-in speed.
–Driver momentarily lifts foot off the accelerator to engage.
–Controlled by a centrifugal switch.
•Disengaging Overdrive:
–When the speed drops below a set level, overdrive disengages.
–Car automatically shifts back to third gear in most designs.
–If full-throttle acceleration is needed, overdrive shifts back to direct drive.
Construction and Working of Overdrive:
Components & Structure:
•Includes a planetary gear set, a sun gear, and a ring gear.
•Input shaft has splined grooves at the end with a freewheel clutch for
disengagement.
•Freewheel assembly (overrunning clutch) drives the main shaft when below cut-in
speed.
Operation of Overdrive:
•Engaging Overdrive:
–Car must be running above a set cut-in speed.
–Driver momentarily lifts foot off the accelerator to engage.
–Controlled by a centrifugal switch.
•Disengaging Overdrive:
–When the speed drops below a set level, overdrive disengages.
–Car automatically shifts back to third gear in most designs.
–If full-throttle acceleration is needed, overdrive shifts back to direct drive.
Construction and Working of Overdrive:
Components & Structure:
•Includes a planetary gear set, a sun gear, and a ring gear.
•Input shaft has splined grooves at the end with a freewheel clutch for
disengagement.
•Freewheel assembly (overrunning clutch) drives the main shaft when below cut-in
speed.
OVERDRIVES
•Functionality & Operation:
•Speed Increase:
–Achieved by locking the sun gear and driving the ring gear via the planet-pinion cage.
–This results in higher output shaft speed but reduces power to the wheels.
•Cut-in Speed:
–Minimum speed required for overdrive engagement.
–Below cut-in speed, sun gear is unlocked, and the drive becomes direct.
–Above cut-in speed, sun gear locks via electrical or hydraulic controls, enabling
overdrive.
•Power Transmission Path:
–Transmission main shaft → Planet gear carrier → Ring gear → Overdrive main
shaft.
–Pinions rotate around the stationary sun gear, increasing ring gear speed.
•Gear Ratio:
–Typically 0.7:1 (overdrive output shaft rotates faster than input).
–Ring gear is splined to the outer case of the freewheel assembly, which is part of the
overdrive main shaft.
•Functionality & Operation:
•Speed Increase:
–Achieved by locking the sun gear and driving the ring gear via the planet-pinion cage.
–This results in higher output shaft speed but reduces power to the wheels.
•Cut-in Speed:
–Minimum speed required for overdrive engagement.
–Below cut-in speed, sun gear is unlocked, and the drive becomes direct.
–Above cut-in speed, sun gear locks via electrical or hydraulic controls, enabling
overdrive.
•Power Transmission Path:
–Transmission main shaft → Planet gear carrier → Ring gear → Overdrive main
shaft.
–Pinions rotate around the stationary sun gear, increasing ring gear speed.
•Gear Ratio:
–Typically 0.7:1 (overdrive output shaft rotates faster than input).
–Ring gear is splined to the outer case of the freewheel assembly, which is part of the
overdrive main shaft.
OVERDRIVES
Advantages:
•Reduces Engine Speed: Maintains highway speed with lower engine RPM.
•Improves Efficiency: Requires less power to sustain motion, reducing engine load.
•Enhances Fuel Economy: Saves fuel by operating at optimal efficiency.
•Minimizes Wear & Tear: Reduces stress on engine components and accessories.
•Better Speed Maintenance: Allows a car to travel at 88 km/hr while the engine runs at an
equivalent of 70 km/hr, enhancing performance and longevity.
Advantages:
•Reduces Engine Speed: Maintains highway speed with lower engine RPM.
•Improves Efficiency: Requires less power to sustain motion, reducing engine load.
•Enhances Fuel Economy: Saves fuel by operating at optimal efficiency.
•Minimizes Wear & Tear: Reduces stress on engine components and accessories.
•Better Speed Maintenance: Allows a car to travel at 88 km/hr while the engine runs at an
equivalent of 70 km/hr, enhancing performance and longevity.
OVERDRIVES - Freewheel Drive (Overrunning Clutch)
•Also known as sprang clutch or one-way clutch.
•Function: Allows rotational motion in one direction only, disengaging when the
driven shaft rotates faster than the driveshaft.
Components:
•Hub with internal splines (connects transmission shaft to freewheel unit).
•Cam with four cam profiles (holds 12 rollers in a cage).
•Outer race (splined to overdrive output shaft).
Working Mechanism:
•When transmission output shaft rotates faster, rollers move into the narrow
gap between the cam and outer race, locking the system and transmitting motion.
•When the outer race turns faster, rollers drop into valleys of the cam, unlocking
the connection. The assembly then acts as a roller bearing, preventing torque
transfer.
•Also known as sprang clutch or one-way clutch.
•Function: Allows rotational motion in one direction only, disengaging when the
driven shaft rotates faster than the driveshaft.
Components:
•Hub with internal splines (connects transmission shaft to freewheel unit).
•Cam with four cam profiles (holds 12 rollers in a cage).
•Outer race (splined to overdrive output shaft).
Working Mechanism:
•When transmission output shaft rotates faster, rollers move into the narrow
gap between the cam and outer race, locking the system and transmitting motion.
•When the outer race turns faster, rollers drop into valleys of the cam, unlocking
the connection. The assembly then acts as a roller bearing, preventing torque
transfer.
TRANSFER BOX
Definition: A transfer box (or T-case) is a component in four-wheel-drive (4WD)
and all-wheel-drive (AWD) vehicles that distributes engine torque to all four
wheels.
•Other Names: Transfer gear case, transfer gearbox, jockey box.
•Connection: Linked to the engine, front axles, and rear axles via drive shafts.
•Control Mechanism: Operated by the driver through a transfer lever or button
inside the vehicle.
Function:
1.Transfers power from transmission to front and rear axles.
2.Locks front and rear axles when required.
3.Balances rotational differences between front and rear wheels.
4.Provides different speed ranges (high and low).
Definition: A transfer box (or T-case) is a component in four-wheel-drive (4WD)
and all-wheel-drive (AWD) vehicles that distributes engine torque to all four
wheels.
•Other Names: Transfer gear case, transfer gearbox, jockey box.
•Connection: Linked to the engine, front axles, and rear axles via drive shafts.
•Control Mechanism: Operated by the driver through a transfer lever or button
inside the vehicle.
Function:
1.Transfers power from transmission to front and rear axles.
2.Locks front and rear axles when required.
3.Balances rotational differences between front and rear wheels.
4.Provides different speed ranges (high and low).
TRANSFER BOX
Types of Transfer Box:
1.Gear-driven type
2.Chain-driven type
3.Housing type
4.Transfer case shift type
Types of Transfer Box:
1.Gear-driven type
2.Chain-driven type
3.Housing type
4.Transfer case shift type
FLUID FLYWHEEL
Definition:
A fluid flywheel (also called a fluid clutch or fluid coupling) is a device that transmits power
between a driving and driven member using fluid instead of direct mechanical contact.
Construction & Working:
•Components:
•Driving member (Impeller) – Connected to the engine flywheel.
•Driven member (Turbine) – Connected to the transmission shaft.
•Both members are enclosed in a housing filled with fluid (oil of specific viscosity).
•Operation:
•The impeller rotates, throwing the oil outward due to centrifugal force.
•The oil strikes the turbine vanes, making the driven member rotate.
•The speed of the driven member increases as engine speed increases.
Advantages:
1.Smooth power transmission.
2.Absorbs shocks and vibrations.
3.No separate pedal or lever required.
Disadvantages:
1.Drag on gearbox shaft even when slip is 100%.
2.Difficult gear changing with ordinary crash-type gearboxes
(hence, used with epicyclic gearboxes).
Definition:
A fluid flywheel (also called a fluid clutch or fluid coupling) is a device that transmits power
between a driving and driven member using fluid instead of direct mechanical contact.
Construction & Working:
•Components:
•Driving member (Impeller) – Connected to the engine flywheel.
•Driven member (Turbine) – Connected to the transmission shaft.
•Both members are enclosed in a housing filled with fluid (oil of specific viscosity).
•Operation:
•The impeller rotates, throwing the oil outward due to centrifugal force.
•The oil strikes the turbine vanes, making the driven member rotate.
•The speed of the driven member increases as engine speed increases.
Advantages:
1.Smooth power transmission.
2.Absorbs shocks and vibrations.
3.No separate pedal or lever required.
Disadvantages:
1.Drag on gearbox shaft even when slip is 100%.
2.Difficult gear changing with ordinary crash-type gearboxes
(hence, used with epicyclic gearboxes).
TORQUE CONVERTER GEARBOX
•Construction:
•Similar to a fluid flywheel but includes an additional stationary stator
(reaction member).
•All members have specially shaped blades or vanes.
•Operation:
•Unlike a fluid flywheel, which transmits the same torque as the engine, a
torque converter increases torque (2:1 to 3:1 ratio).
•It functions similarly to a gearbox but provides continuous torque variation
instead of discrete steps.
•Efficiency:
•Works efficiently within narrow speed limits due to continuous torque
variation.
•Offers better performance than a gearbox in transmitting power smoothly.
•Construction:
•Similar to a fluid flywheel but includes an additional stationary stator
(reaction member).
•All members have specially shaped blades or vanes.
•Operation:
•Unlike a fluid flywheel, which transmits the same torque as the engine, a
torque converter increases torque (2:1 to 3:1 ratio).
•It functions similarly to a gearbox but provides continuous torque variation
instead of discrete steps.
•Efficiency:
•Works efficiently within narrow speed limits due to continuous torque
variation.
•Offers better performance than a gearbox in transmitting power smoothly.
TORQUE CONVERTER GEARBOX
A torque converter consists of three main parts, which work together to transfer and
multiply torque using fluid dynamics.
•Impeller (Pump) – Driving Member:
–Connected to the engine shaft and rotates with engine speed.
–Contains curved vanes that direct transmission fluid outward due to centrifugal
force.
–Acts as a centrifugal pump, delivering fluid to the turbine.
•Turbine – Driven Member:
–Connected to the vehicle's transmission and rotates with the fluid force.
–Curved blades redirect the fluid, generating motion.
–Has a lock-up clutch that engages at coupling point to reduce losses and
improve efficiency.
•Stator – Reaction Member:
–Placed between the impeller and turbine, connected via a freewheel clutch.
–Redirects returning fluid to assist in torque multiplication (changing direction
by ~90°).
–Prevents fluid backflow, ensuring efficient energy transfer.
A torque converter consists of three main parts, which work together to transfer and
multiply torque using fluid dynamics.
•Impeller (Pump) – Driving Member:
–Connected to the engine shaft and rotates with engine speed.
–Contains curved vanes that direct transmission fluid outward due to centrifugal
force.
–Acts as a centrifugal pump, delivering fluid to the turbine.
•Turbine – Driven Member:
–Connected to the vehicle's transmission and rotates with the fluid force.
–Curved blades redirect the fluid, generating motion.
–Has a lock-up clutch that engages at coupling point to reduce losses and
improve efficiency.
•Stator – Reaction Member:
–Placed between the impeller and turbine, connected via a freewheel clutch.
–Redirects returning fluid to assist in torque multiplication (changing direction
by ~90°).
–Prevents fluid backflow, ensuring efficient energy transfer.
TORQUE CONVERTER GEARBOX
•The torque converter operates in three stages:
•Stall (Stop Condition):
–The impeller rotates, but the turbine remains stationary as the driver holds the
brake.
–Maximum torque multiplication occurs.
–When the accelerator is pressed, the impeller moves faster, initiating turbine rotation.
•Acceleration:
–The turbine speed increases, but there is still a significant speed difference between
the impeller and turbine.
–Torque multiplication gradually reduces compared to stall condition.
•Coupling:
–The turbine reaches 90% of the impeller speed, known as the coupling point.
–Torque multiplication stops, and the torque converter functions as a fluid coupling.
–The lock-up clutch engages, making the turbine and impeller move at the same
speed, improving efficiency.
–The stator also begins to rotate, reducing resistance.
•The torque converter operates in three stages:
•Stall (Stop Condition):
–The impeller rotates, but the turbine remains stationary as the driver holds the
brake.
–Maximum torque multiplication occurs.
–When the accelerator is pressed, the impeller moves faster, initiating turbine rotation.
•Acceleration:
–The turbine speed increases, but there is still a significant speed difference between
the impeller and turbine.
–Torque multiplication gradually reduces compared to stall condition.
•Coupling:
–The turbine reaches 90% of the impeller speed, known as the coupling point.
–Torque multiplication stops, and the torque converter functions as a fluid coupling.
–The lock-up clutch engages, making the turbine and impeller move at the same
speed, improving efficiency.
–The stator also begins to rotate, reducing resistance.
TORQUE CONVERTER GEARBOX
S.
No.
Fluid coupling Torque converter
1.
Output speed is less than the input
speed.
Output speed is more than the
input speed.
2.
It is used to transmit rotary motion
from a shaft to another shaft with
Casing rotates with shafts.
It is also used to transmit rotary
motion from a shaft to another
with increased torque.
3.Casing rotates with shafts.Casing is stationary.
4.
There are no stationary guide
vanes in the flow path.
Stationary guide vanes are
provided in the flow path.
5.
There is no torque
multiplication between shafts.
Itprovidestorque
multiplication between shaft
during accelerations
S.
No.
Fluid coupling Torque converter
1.
Output speed is less than the input
speed.
Output speed is more than the
input speed.
2.
It is used to transmit rotary motion
from a shaft to another shaft with
Casing rotates with shafts.
It is also used to transmit rotary
motion from a shaft to another
with increased torque.
3.Casing rotates with shafts.Casing is stationary.
4.
There are no stationary guide
vanes in the flow path.
Stationary guide vanes are
provided in the flow path.
5.
There is no torque
multiplication between shafts.
Itprovidestorque
multiplication between shaft
during accelerations
PROPELLER SHAFT
Functions of Propeller Shaft:
•Transmits power from the gearbox output shaft to the differential and wheels.
•Transfers motion at varying angles as the vehicle moves.
•Allows length adjustment between the gearbox and rear axle.
Construction of Propeller Shaft:
•Made of thin-walled steel tubes (diameter: 50-70 mm, thickness: 1.5-7.5
mm).
•Uses universal joints at both ends to handle angular variations.
•A slip joint accommodates length changes.
•In long vehicles (trucks, buses), intermediate shafts are added for support
using a bearing unit.
Types of Propeller Shafts:
•Solid or open type –
Exposed shaft, used in some vehicles.
•Hollow or enclosed type –
Lightweight, stronger, and more common.
Functions of Propeller Shaft:
•Transmits power from the gearbox output shaft to the differential and wheels.
•Transfers motion at varying angles as the vehicle moves.
•Allows length adjustment between the gearbox and rear axle.
Construction of Propeller Shaft:
•Made of thin-walled steel tubes (diameter: 50-70 mm, thickness: 1.5-7.5
mm).
•Uses universal joints at both ends to handle angular variations.
•A slip joint accommodates length changes.
•In long vehicles (trucks, buses), intermediate shafts are added for support
using a bearing unit.
Types of Propeller Shafts:
•Solid or open type –
Exposed shaft, used in some vehicles.
•Hollow or enclosed type –
Lightweight, stronger, and more common.
PROPELLER SHAFT- TYPES
1. Open Type Propeller Shaft:
•Used in heavy commercial vehicles, cars, and light vehicles.
•Tubular in cross-section but not enclosed.
•Two universal joints (one at the gearbox, one at the differential).
•Longer shaft, often made of two portions for support.
•Connected to the chassis cross member with a bearing.
•Front universal joint has a splined connection for telescopic action to
accommodate axle movement.
2. Enclosed Type Propeller Shaft:
•Prevents axle twisting during power transmission.
•Solid cross-section, with a smaller diameter than the open type.
•Supported by roller bearings inside torque tubes at the front and rear.
•May have only one universal joint, connected to the gearbox via a ball joint or
spherical bearing.
•The torque tube resists twisting motion of the axle during braking.
•Rear connection uses a splined sleeve and rivets to prevent longitudinal
movement.
1. Open Type Propeller Shaft:
•Used in heavy commercial vehicles, cars, and light vehicles.
•Tubular in cross-section but not enclosed.
•Two universal joints (one at the gearbox, one at the differential).
•Longer shaft, often made of two portions for support.
•Connected to the chassis cross member with a bearing.
•Front universal joint has a splined connection for telescopic action to
accommodate axle movement.
2. Enclosed Type Propeller Shaft:
•Prevents axle twisting during power transmission.
•Solid cross-section, with a smaller diameter than the open type.
•Supported by roller bearings inside torque tubes at the front and rear.
•May have only one universal joint, connected to the gearbox via a ball joint or
spherical bearing.
•The torque tube resists twisting motion of the axle during braking.
•Rear connection uses a splined sleeve and rivets to prevent longitudinal
movement.
SLIP JOINTS
•The propeller shaft is inclined downward from the transmission main shaft to the rear axle.
•As the rear axle moves due to compression and expansion of the rear springs, the propeller
shaft changes in length (shortens and lengthens).
•A slip joint is used between the propeller shaft and the universal joint to compensate for this
variation in length.
•The slip joint enables smooth power transmission from the engine to the rear axle while
allowing axial movement.
•In vehicles with a torque-tube drive, a slip joint
is not required.
•The slip joint consists of:
•A male splined end of the main shaft.
•A female splined member (integrated with the universal joint hub).
•The splines ensure the slip joint can transmit power efficiently while accommodating length
changes in the propeller shaft.
•The propeller shaft is inclined downward from the transmission main shaft to the rear axle.
•As the rear axle moves due to compression and expansion of the rear springs, the propeller
shaft changes in length (shortens and lengthens).
•A slip joint is used between the propeller shaft and the universal joint to compensate for this
variation in length.
•The slip joint enables smooth power transmission from the engine to the rear axle while
allowing axial movement.
•In vehicles with a torque-tube drive, a slip joint
is not required.
•The slip joint consists of:
•A male splined end of the main shaft.
•A female splined member (integrated with the universal joint hub).
•The splines ensure the slip joint can transmit power efficiently while accommodating length
changes in the propeller shaft.
UNIVERSAL JOINTS
Purpose: Universal joints create a flexible connection between two rigid shafts at
an angle, allowing for power transmission under varying conditions.
Function in Automobiles:
•Connects the propeller shaft to the gearbox shaft to transmit rotary motion.
•Accommodates rear axle movement caused by road springs, ensuring continuous
power transmission.
•Essential when a gearbox is mounted rigidly while the rear axle position varies.
Applications in Vehicles:
•Between clutch and gearbox.
•Between main gearbox and auxiliary gearbox.
•On driving shafts of a driven front axle.
Purpose: Universal joints create a flexible connection between two rigid shafts at
an angle, allowing for power transmission under varying conditions.
Function in Automobiles:
•Connects the propeller shaft to the gearbox shaft to transmit rotary motion.
•Accommodates rear axle movement caused by road springs, ensuring continuous
power transmission.
•Essential when a gearbox is mounted rigidly while the rear axle position varies.
Applications in Vehicles:
•Between clutch and gearbox.
•Between main gearbox and auxiliary gearbox.
•On driving shafts of a driven front axle.
UNIVERSAL JOINTS
Construction:
•Consists of two yokes attached to the shaft ends.
•A central cross piece (spider) connects the yokes.
•Bearings in the yoke allow smooth rotation as shaft angles change.
Operational Behavior:
•When shafts operate at an angle, motion is not uniform.
•The driven shaft speed fluctuates, reaching a maximum and minimum twice per
revolution due to pivot pin rotation in different planes.
Types of Universal Joints
Universal joints are classified as follows.
»Variable velocity joints,
»Constant Velocity (CV) joints.
Construction:
•Consists of two yokes attached to the shaft ends.
•A central cross piece (spider) connects the yokes.
•Bearings in the yoke allow smooth rotation as shaft angles change.
Operational Behavior:
•When shafts operate at an angle, motion is not uniform.
•The driven shaft speed fluctuates, reaching a maximum and minimum twice per
revolution due to pivot pin rotation in different planes.
Types of Universal Joints
Universal joints are classified as follows.
»Variable velocity joints,
»Constant Velocity (CV) joints.
UNIVERSAL JOINTS-Variable Velocity
Joints
•In variable velocity joints, the driven and driving shafts do not rotate at the same
speed throughout a full revolution.
•When the shafts are perfectly aligned, they rotate at the same speed.
•In practice, the drive shaft is always inclined, causing speed fluctuations in the driven
shaft.
•The speed variation increases with the flex angle of the universal joint.
•To balance speed variations, yokes on shafts should not be in different planes when
using two variable velocity joints in one drive line.
•Types of Variable Velocity Joints:
1.Cross or Spider Type:
–Two yokes are connected at right angles by a cross (spider).
–Needle bearings are mounted between yokes and cross ends.
–Commonly used in driving shafts.
Joints
•In variable velocity joints, the driven and driving shafts do not rotate at the same
speed throughout a full revolution.
•When the shafts are perfectly aligned, they rotate at the same speed.
•In practice, the drive shaft is always inclined, causing speed fluctuations in the driven
shaft.
•The speed variation increases with the flex angle of the universal joint.
•To balance speed variations, yokes on shafts should not be in different planes when
using two variable velocity joints in one drive line.
•Types of Variable Velocity Joints:
1.Cross or Spider Type:
–Two yokes are connected at right angles by a cross (spider).
–Needle bearings are mounted between yokes and cross ends.
–Commonly used in driving shafts.
UNIVERSAL JOINTS-Variable Velocity
Joints2.Ring Type:
•Uses a flexible ring for connection.
•Two or three-armed spiders are bolted to opposite
faces of the flexible ring.
•The arms are arranged midway between each other.
•Materials: Made of rubber rings or thin steel discs instead of fabric rings.
Advantages: Absorbs torque fluctuations, provides axial movement, and requires no
lubrication.
Drawback: The ring has a limited lifespan.
3.Ball and Trunnion Type:
•Combines universal joint and slip joint in one assembly.
•A pin (cross shaft) is placed in T-fashion at the universal joint end.
•Balls mounted on needle bearings allow movement in grooves inside the
joint’s outer body.
•A heavy spring prevents excessive longitudinal movement.
•Power transmission: Through the trunnion, balls, and cross shaft.
•The bending moment is absorbed by ball rolling action and ball movement
along trunnion grooves.
•Covered by rubber or leather boots for protection.
Joints2.Ring Type:
•Uses a flexible ring for connection.
•Two or three-armed spiders are bolted to opposite
faces of the flexible ring.
•The arms are arranged midway between each other.
•Materials: Made of rubber rings or thin steel discs instead of fabric rings.
Advantages: Absorbs torque fluctuations, provides axial movement, and requires no
lubrication.
Drawback: The ring has a limited lifespan.
3.Ball and Trunnion Type:
•Combines universal joint and slip joint in one assembly.
•A pin (cross shaft) is placed in T-fashion at the universal joint end.
•Balls mounted on needle bearings allow movement in grooves inside the
joint’s outer body.
•A heavy spring prevents excessive longitudinal movement.
•Power transmission: Through the trunnion, balls, and cross shaft.
•The bending moment is absorbed by ball rolling action and ball movement
along trunnion grooves.
•Covered by rubber or leather boots for protection.
UNIVERSAL JOINTS-Constant velocity joints
Constant Velocity Joints:
•Ensure that the driven shaft rotates at the same speed as the driving shaft, regardless of the
angle.
•Commonly used in front-wheel-drive axles for smooth power transmission at large angles.
•Cadillac cars use ball-and-socket-type CV joints in their propeller shafts.
Types of Constant Velocity Joints:
•Rzeppa Joint:
–Consists of spherical inner and outer ball races with parallel grooves.
–Steel balls are placed in grooves within a spherical recess.
–Torque transmission occurs via balls, ensuring equal velocity for both shafts.
•Bendix Weiss Joint:
–Uses balls arranged in a circular pattern around a sphere.
–Four driving balls fit into machined races within yokes.
–A central ball acts as an inner race.
–Aligning action of the balls maintains constant velocity.
•Tracta Joint:
–Uses four yokes, two attached to shafts and two floating at the center.
–Circular segment mating surfaces allow smooth motion.
–Floating yokes contribute to constant velocity transmission.
Constant Velocity Joints:
•Ensure that the driven shaft rotates at the same speed as the driving shaft, regardless of the
angle.
•Commonly used in front-wheel-drive axles for smooth power transmission at large angles.
•Cadillac cars use ball-and-socket-type CV joints in their propeller shafts.
Types of Constant Velocity Joints:
•Rzeppa Joint:
–Consists of spherical inner and outer ball races with parallel grooves.
–Steel balls are placed in grooves within a spherical recess.
–Torque transmission occurs via balls, ensuring equal velocity for both shafts.
•Bendix Weiss Joint:
–Uses balls arranged in a circular pattern around a sphere.
–Four driving balls fit into machined races within yokes.
–A central ball acts as an inner race.
–Aligning action of the balls maintains constant velocity.
•Tracta Joint:
–Uses four yokes, two attached to shafts and two floating at the center.
–Circular segment mating surfaces allow smooth motion.
–Floating yokes contribute to constant velocity transmission.
DIFFERENTIAL
• On flat roads, both right and left wheels rotate at the same speed.
• During a turn, the inner wheel travels a shorter distance and must rotate
slower than the outer wheel, which covers more distance.
• The outer wheel follows a larger arc (OB), while the inner wheel follows a
smaller arc (OA), as shown in Figure
• On rough surfaces, the wheel with more traction (friction) rotates faster than
the other.
• On ordinary roads, both wheels maintain identical rpm due to road contact.
• Differences in tire inflation and wear can also cause slight rpm variations.
• If wheels are forced to run at the same rpm despite surface differences, tire
wear increases, and driving performance is affected.
• A differential device is used to balance the speed differences between the
two wheels while transmitting equal torque, ensuring smooth turning and better
performance.
• On flat roads, both right and left wheels rotate at the same speed.
• During a turn, the inner wheel travels a shorter distance and must rotate
slower than the outer wheel, which covers more distance.
• The outer wheel follows a larger arc (OB), while the inner wheel follows a
smaller arc (OA), as shown in Figure
• On rough surfaces, the wheel with more traction (friction) rotates faster than
the other.
• On ordinary roads, both wheels maintain identical rpm due to road contact.
• Differences in tire inflation and wear can also cause slight rpm variations.
• If wheels are forced to run at the same rpm despite surface differences, tire
wear increases, and driving performance is affected.
• A differential device is used to balance the speed differences between the
two wheels while transmitting equal torque, ensuring smooth turning and better
performance.
DIFFERENTIAL
•Major Components of Differential
The following main components are used in the differential assembly.
–Drive pinion or Bevel pinion.
–Ring gear or Crown wheel.
–Differential case.
–Differential side gear or sun gears.
–Differential pinions (or) planet gears.
–Axle shafts or half shafts.
–Pinion shaft or cross pin (or) spider.
•Major Components of Differential
The following main components are used in the differential assembly.
–Drive pinion or Bevel pinion.
–Ring gear or Crown wheel.
–Differential case.
–Differential side gear or sun gears.
–Differential pinions (or) planet gears.
–Axle shafts or half shafts.
–Pinion shaft or cross pin (or) spider.
DIFFERENTIAL
Construction of Differential:
•The differential side gears are mounted on the inner ends of axle shafts.
•Two bevel gears mesh at a 90° angle to connect driving and driven shafts.
•The differential case holds the axle shafts, side gears, and pinion gears.
•Pinion gears are mounted on a pinion shaft inside the differential case.
•The ring gear is bolted to the differential case and rotated by the drive pinion.
•The drive pinion connects to the driver shaft via a universal joint.
Basic Principle of Operation:
•Straight driving: Torque from the drive pinion rotates the ring gear, making the
entire differential rotate as a unit. Both wheels turn at the same speed.
•Turning: If one wheel experiences resistance (e.g., during a turn), differential
pinions spin to allow the inner wheel to slow down while the outer wheel speeds up.
•Example: If the ring gear makes 10 rotations during a right turn:
–The left wheel (outer) makes 12 rotations (travels farther).
–The right wheel (inner) makes 8 rotations (travels less).
•The ring gear's rotation equals the average of the two side gears’ rotations.
Construction of Differential:
•The differential side gears are mounted on the inner ends of axle shafts.
•Two bevel gears mesh at a 90° angle to connect driving and driven shafts.
•The differential case holds the axle shafts, side gears, and pinion gears.
•Pinion gears are mounted on a pinion shaft inside the differential case.
•The ring gear is bolted to the differential case and rotated by the drive pinion.
•The drive pinion connects to the driver shaft via a universal joint.
Basic Principle of Operation:
•Straight driving: Torque from the drive pinion rotates the ring gear, making the
entire differential rotate as a unit. Both wheels turn at the same speed.
•Turning: If one wheel experiences resistance (e.g., during a turn), differential
pinions spin to allow the inner wheel to slow down while the outer wheel speeds up.
•Example: If the ring gear makes 10 rotations during a right turn:
–The left wheel (outer) makes 12 rotations (travels farther).
–The right wheel (inner) makes 8 rotations (travels less).
•The ring gear's rotation equals the average of the two side gears’ rotations.
DIFFERENTIAL- Types
1. Conventional differential:
•The conventional differential is shown in Figure. It shows the pictorial representation
of the differential. The principle of operation is same as above.
2. Limited Slip differential:
•A standard differential sends power to the wheel with the least traction, which can
cause slipping on ice, mud, or wet roads.
•If one wheel is on dry pavement and the other on ice, the slipping wheel gets most of
the power, preventing movement.
•Differential locks solve this by ensuring both wheels receive equal power while still
allowing normal turns.
Working of Limited Slip Differential (LSD):
•LSD limits rpm differences between the two wheels using thrust washers and
clutch plates inside the differential case.
•When one wheel faces more resistance, the opposite wheel tries to rotate faster.
•This causes the clutch teeth to engage, pushing the side gears against thrust
washers.
•Friction increases, making the rear axle shafts rotate closer to the differential case,
reducing slip.
1. Conventional differential:
•The conventional differential is shown in Figure. It shows the pictorial representation
of the differential. The principle of operation is same as above.
2. Limited Slip differential:
•A standard differential sends power to the wheel with the least traction, which can
cause slipping on ice, mud, or wet roads.
•If one wheel is on dry pavement and the other on ice, the slipping wheel gets most of
the power, preventing movement.
•Differential locks solve this by ensuring both wheels receive equal power while still
allowing normal turns.
Working of Limited Slip Differential (LSD):
•LSD limits rpm differences between the two wheels using thrust washers and
clutch plates inside the differential case.
•When one wheel faces more resistance, the opposite wheel tries to rotate faster.
•This causes the clutch teeth to engage, pushing the side gears against thrust
washers.
•Friction increases, making the rear axle shafts rotate closer to the differential case,
reducing slip.
DIFFERENTIAL- Types
Types of Limited Slip Differentials:
•Clutch-Plate Differential: Uses multiple clutch plates to distribute power evenly
between wheels.
•Cone Clutch Differential: Uses cone-shaped clutches for improved friction and
torque transfer.
Limited Slip Clutch-Plate Differential Cone Clutch
Differential
Types of Limited Slip Differentials:
•Clutch-Plate Differential: Uses multiple clutch plates to distribute power evenly
between wheels.
•Cone Clutch Differential: Uses cone-shaped clutches for improved friction and
torque transfer.
Limited Slip Clutch-Plate Differential Cone Clutch
Differential
DIFFERENTIAL- Types
3. Non-Slip Differential
•A torque-controlled differential that allows preloading of the system.
•Operates using resultant moments, and preload can be adjusted for better
performance.
Advantages of Non-Slip Differential:
•Maximum traction for all grip levels (adjustable).
•Reduces fuel consumption, improving efficiency.
•Minimizes tire wear, extending tire life.
•Provides a smoother and more comfortable drive.
•Ensures constant speed drive, preventing power loss.
•Reduces understeer when cornering, improving handling.
4. Double Reduction Type Differential
•Used in heavy-duty trucks and military vehicles for better torque and power
transmission.
•Unlike standard differentials with a single gear reduction, this system uses two
stages of gear reduction for increased torque.
3. Non-Slip Differential
•A torque-controlled differential that allows preloading of the system.
•Operates using resultant moments, and preload can be adjusted for better
performance.
Advantages of Non-Slip Differential:
•Maximum traction for all grip levels (adjustable).
•Reduces fuel consumption, improving efficiency.
•Minimizes tire wear, extending tire life.
•Provides a smoother and more comfortable drive.
•Ensures constant speed drive, preventing power loss.
•Reduces understeer when cornering, improving handling.
4. Double Reduction Type Differential
•Used in heavy-duty trucks and military vehicles for better torque and power
transmission.
•Unlike standard differentials with a single gear reduction, this system uses two
stages of gear reduction for increased torque.
DIFFERENTIAL- Types
Working Principle:
•First Gear Reduction:
–Achieved through a pinion and ring gear, similar to a standard final drive.
•Second Gear Reduction:
–A secondary pinion is mounted on the primary ring gear shaft.
–This pinion drives a large helical gear attached to the differential case,
further reducing speed and increasing torque.
Applications:
•Found in heavy-duty trucks and military vehicles (e.g., 5-wheel track vehicles).
•Some commercial heavy vehicles use either single or double-reduction
differentials based on load requirements.
Working Principle:
•First Gear Reduction:
–Achieved through a pinion and ring gear, similar to a standard final drive.
•Second Gear Reduction:
–A secondary pinion is mounted on the primary ring gear shaft.
–This pinion drives a large helical gear attached to the differential case,
further reducing speed and increasing torque.
Applications:
•Found in heavy-duty trucks and military vehicles (e.g., 5-wheel track vehicles).
•Some commercial heavy vehicles use either single or double-reduction
differentials based on load requirements.
REAR AXLE
•Power is transmitted through rear axles to driving wheels.
Types of Rear Axles:
•Dead Axles:
–Do not rotate with the wheels (stationary axles).
–Common in horse-driven vehicles and rear axles of front-wheel-drive
cars.
–Rear weight of the vehicle is supported by the axle.
–A chain drive is often used in these axles.
•Live Axles:
–Rotate with the wheels and are directly connected to them.
–Modern passenger cars use live axles.
–Differential gears drive each axle shaft through a spline connection.
–Both shafts and gears are enclosed by a housing to protect from water, dust,
and damage while providing a lubricant container.
•Power is transmitted through rear axles to driving wheels.
Types of Rear Axles:
•Dead Axles:
–Do not rotate with the wheels (stationary axles).
–Common in horse-driven vehicles and rear axles of front-wheel-drive
cars.
–Rear weight of the vehicle is supported by the axle.
–A chain drive is often used in these axles.
•Live Axles:
–Rotate with the wheels and are directly connected to them.
–Modern passenger cars use live axles.
–Differential gears drive each axle shaft through a spline connection.
–Both shafts and gears are enclosed by a housing to protect from water, dust,
and damage while providing a lubricant container.
REAR AXLE
Axle Components:
•Half Shafts/Driving Axles:
–Revolve inside the casing.
–Connected to bevel gears splined at one
end and supported by ball or roller bearings at the other end.
Functions and Forces on Axles:
•Weight Support: Axles carry the vehicle's rear weight.
•Bending and Shearing Forces: The rear axle experiences bending due to the
vehicle's weight and side thrusts during cornering.
•Driving Torque: Axles transmit the driving force to the wheels.
Construction of Rear Axles:
•Spiral bevel or hypoid-type gears are used in light vehicles.
•For higher load-bearing capacity, worm gear or double reduction systems are
used.
•Medium carbon alloy steel is used for strength, often containing nickel,
chromium, and molybdenum.
Axle Components:
•Half Shafts/Driving Axles:
–Revolve inside the casing.
–Connected to bevel gears splined at one
end and supported by ball or roller bearings at the other end.
Functions and Forces on Axles:
•Weight Support: Axles carry the vehicle's rear weight.
•Bending and Shearing Forces: The rear axle experiences bending due to the
vehicle's weight and side thrusts during cornering.
•Driving Torque: Axles transmit the driving force to the wheels.
Construction of Rear Axles:
•Spiral bevel or hypoid-type gears are used in light vehicles.
•For higher load-bearing capacity, worm gear or double reduction systems are
used.
•Medium carbon alloy steel is used for strength, often containing nickel,
chromium, and molybdenum.
REAR AXLETypes of Rear Axles:
•Semi-Floating Axle:
–The inner end is supported by the differential side gear.
–The outer end carries the wheel and transmits rotation through splines.
–Pre-lubricated bearings support the axle, and it's common in modern passenger cars.
–Forces: Side thrusts, shear force from the vehicle's weight, twisting from braking and
driving torques.
•Three-Quarter Floating Axle:
–One bearing at the outer end supports the wheel hub, which is keyed to the axle.
–The axle shaft is similar to the semi-floating design but with a single bearing at the outer
end.
–Forces: Bending loads from side thrusts during cornering and twisting from braking and
driving.
•Full-Floating Axle:
–The wheel hub is supported by two bearings mounted on the axle housing.
–The axle shaft is connected to the wheel hub via a coupling, transmitting rotary motion.
–The axle shaft can be removed without disturbing the wheel, and it is relieved from all
load stresses.
–Common in trucks for better durability and ease of maintenance.
•Semi-Floating Axle:
–The inner end is supported by the differential side gear.
–The outer end carries the wheel and transmits rotation through splines.
–Pre-lubricated bearings support the axle, and it's common in modern passenger cars.
–Forces: Side thrusts, shear force from the vehicle's weight, twisting from braking and
driving torques.
•Three-Quarter Floating Axle:
–One bearing at the outer end supports the wheel hub, which is keyed to the axle.
–The axle shaft is similar to the semi-floating design but with a single bearing at the outer
end.
–Forces: Bending loads from side thrusts during cornering and twisting from braking and
driving.
•Full-Floating Axle:
–The wheel hub is supported by two bearings mounted on the axle housing.
–The axle shaft is connected to the wheel hub via a coupling, transmitting rotary motion.
–The axle shaft can be removed without disturbing the wheel, and it is relieved from all
load stresses.
–Common in trucks for better durability and ease of maintenance.
REAR AXLE
Semi-floating axle Three-Quarter floating axle
Full floating axle
Semi-floating axle Three-Quarter floating axle
Full floating axle
REAR AXLE-DRIVES
Rear Axle Drives Overview:
•Power and torque are transmitted from the engine to the wheels.
•When the road wheels rotate, the entire rear axle unit moves forward.
•The torque reaction (opposite direction rotation of the differential housing) is a
reaction that needs to be managed to prevent unwanted movement of the axle.
Types of Rear Axle Drives:
1.Hotchkiss Drive 2. Torque Tube Drive
1. Hotchkiss Drive:
•Components: Propeller shaft, two longitudinal leaf springs, and a slip joint.
•Leaf Springs: Front ends are hinged to the frame, and rear ends are connected with
swinging shackles.
•Slip Joint: Allows the propeller shaft to adjust its length if the rear springs deflect.
•Function: Rear-end torque is absorbed by the springs, which deflect during fast
driving or braking, improving flexibility and shock absorption.
•Power Transfer: Driving force is transferred from the axle casing to the front of the
spring, then to the frame. Both rear-end torque and driving thrust are resisted by the
springs.
Rear Axle Drives Overview:
•Power and torque are transmitted from the engine to the wheels.
•When the road wheels rotate, the entire rear axle unit moves forward.
•The torque reaction (opposite direction rotation of the differential housing) is a
reaction that needs to be managed to prevent unwanted movement of the axle.
Types of Rear Axle Drives:
1.Hotchkiss Drive 2. Torque Tube Drive
1. Hotchkiss Drive:
•Components: Propeller shaft, two longitudinal leaf springs, and a slip joint.
•Leaf Springs: Front ends are hinged to the frame, and rear ends are connected with
swinging shackles.
•Slip Joint: Allows the propeller shaft to adjust its length if the rear springs deflect.
•Function: Rear-end torque is absorbed by the springs, which deflect during fast
driving or braking, improving flexibility and shock absorption.
•Power Transfer: Driving force is transferred from the axle casing to the front of the
spring, then to the frame. Both rear-end torque and driving thrust are resisted by the
springs.
REAR AXLE-DRIVES
Hotchkiss drive
Torque tube drive
Hotchkiss drive
Torque tube drive
REAR AXLE-DRIVES
2. Torque Tube Drive:
•Components: A hollow tube encloses the propeller shaft, connecting the
differential housing and gearbox.
•Tube Function: The torque tube carries both driving thrust and rear-end torque
while housing the propeller shaft.
•Support: The tube is supported by bearings, and only one universal joint is needed
at the gearbox.
•Springs: Torsion bar or helical springs can be used to carry the torque, and
shackles are placed at both ends if laminated springs are used.
•Power Transfer: The driving thrust is transferred from the front end of the tube to
the frame through the gearbox.
•Both systems manage rear-end torque and driving thrust but differ in structure and
the way power is transmitted through the chassis.
2. Torque Tube Drive:
•Components: A hollow tube encloses the propeller shaft, connecting the
differential housing and gearbox.
•Tube Function: The torque tube carries both driving thrust and rear-end torque
while housing the propeller shaft.
•Support: The tube is supported by bearings, and only one universal joint is needed
at the gearbox.
•Springs: Torsion bar or helical springs can be used to carry the torque, and
shackles are placed at both ends if laminated springs are used.
•Power Transfer: The driving thrust is transferred from the front end of the tube to
the frame through the gearbox.
•Both systems manage rear-end torque and driving thrust but differ in structure and
the way power is transmitted through the chassis.
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