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Questions and Answers
What was the main reason for developing independent front suspension?
What type of spring is commonly used in independent front suspension?
What is prevented by the independent front suspension system?
What is improved by the wider spacing of the front springs?
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How many types of independent front suspensions are mentioned?
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What is the main characteristic of independent front suspension?
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When was the independent front suspension developed?
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What is the advantage of independent front suspension?
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What is the effect of independent front suspension on the steering system?
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What is the current trend in front suspension systems?
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What is the primary advantage of using independent front suspension?
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What type of suspension allows the wheels to respond individually to road conditions?
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Which of the following is a characteristic of independent front suspension?
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What is the effect of independent front suspension on wheel wobble?
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Which type of suspension is used in all vehicles nowadays?
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What is the advantage of a wider spacing of the front springs?
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Which of the following is not a type of independent front suspension?
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What is the primary purpose of the coil or torsion bar or leaf spring in independent front suspension?
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Which type of suspension is mentioned as an alternative to independent front suspension?
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What is the result of greater wheel movement in independent front suspension?
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What is the primary function of the front springs in an independent front suspension system?
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Which type of suspension is mentioned as an alternative to independent front suspension?
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What is the advantage of a Mac Pherson Strut and link type suspension?
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What is the main characteristic of a longitudinal leaf spring rear suspension?
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Which type of suspension system is used in all vehicles nowadays?
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What is the purpose of the coil or torsion bar or leaf spring in independent front suspension?
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What is the effect of independent front suspension on wheel wobble?
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What is the main difference between independent front suspension and rigid axle front suspension?
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What is the advantage of a parallelogram type suspension?
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What is the purpose of using a coil spring in independent front suspension?
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What is the primary benefit of independent front suspension?
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What type of suspension allows the wheels to move independently?
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What is the characteristic of the independent front suspension system?
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What is the advantage of using a coil spring in independent front suspension?
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What type of suspension is used in modern vehicles?
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What is the effect of independent front suspension on the steering system?
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What is the type of suspension that allows greater wheel movement?
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How many types of independent front suspensions are mentioned?
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What is the purpose of the coil or torsion bar or leaf spring in independent front suspension?
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What is the advantage of a wider spacing of the front springs?
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What is the primary purpose of power steering systems?
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What is the function of the pressure relief flow valve in the power steering pump?
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What is the common problem in a steering system that is caused by worn ball sockets or worn idler arm?
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How do you bleed a power steering system?
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What is the purpose of the control valve in a power steering system?
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What is the result of air in the power steering system?
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What is the function of the power steering pump?
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What is the purpose of the dry-park test?
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What is the normal limit of steering wheel rotation without moving the front wheels?
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What is the purpose of clamps and clamp bolts in a steering system?
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Study Notes
Transmission System
- The transmission system plays a crucial role in transferring power from the engine to the wheels, enabling the vehicle to move efficiently across different speeds and conditions.
- Components of a transmission system:
- Transmission (manual or automatic)
- Clutch (for manual transmission)
- Gearbox
- Differential
- Driveshaft (propeller shaft)
- Torque converter (for automatic transmission)
Functions of a Transmission System
- Gear ratio selection
- Torque multiplication
- Smooth power delivery
- Adaptability to driving conditions
- Efficiency improvement (modern transmission systems aim to optimize fuel efficiency and reduce emissions)
Clutches and Power Transmission
- The purpose of the clutch is to allow the driver to couple or decouple the engine and transmission.
- Requirements of a clutch:
- Pick up its load smoothly without grab or clatter
- Have a driven disc of low moment of inertia to permit easy shifting
- Damp out any vibration of the crankshaft to prevent gear clatter
- Require little pedal pressure to operate
- Be easy to adjust and service
- Be cheap to manufacture
Types of Clutches
- Positive clutches
- Merits: simple, no slip, no heat generated, compact, and low cost
- Friction clutches
- Merits: smooth engagement, can slip during engagement, high torque capacity
- Types:
- Single plate clutch
- Multi-plate clutch
- Centrifugal clutch
- Semi-centrifugal clutch
- Diaphragm spring single plate clutch
- Electro-magnetic clutch
- Overrunning clutch or free-wheel unit
Diaphragm Spring Single Plate Clutch
- Advantages:
- Compact design
- Easier to balance rotationally
- Uniformly distributed pressure on pressure plate
- No release levers required
- Minimum effort required to disengage the clutch
- Minimum internal friction
Multi-Plate Clutch
- Used in heavy transport vehicles, epicyclic gearboxes, and racing cars
- Advantages:
- Higher torque transmission capacity
- Compact design
Automatic Clutch
- Centrifugal clutch: automatically disengages when speed falls below a certain value and re-engages when speed rises above it
- Fluid coupling or fluid torque converter: used to transmit power between two rotating shafts without Interrupting the flow of power
Gear Box in an Automobile
- Necessity of gear box: to maintain engine speed at the most economical value under all conditions of vehicle movement
- Functions of a gear box:
- Torque ratio variation between engine and wheels
- Means of reversal of vehicle motion
- Transmission can be disconnected from engine by neutral position of gear box
Types of Gear Box
- Progressive type gear box
- Epicyclic (or) planetary type gear box
- Selective type gear box (e.g., constant mesh gear box with positive dog clutch, constant mesh gear box with synchromesh device, sliding mesh gear box)### Gearbox
- A gearbox is a mechanical device that uses gears to transmit and change the speed of rotation of a mechanical shaft
- Types of gearboxes:
- Constant mesh gearbox
- Synchromesh gearbox
- Automatic gearbox
Constant Mesh Gearbox
- All gears on the main shaft are in constant mesh with the corresponding gears on the lay shaft
- Gears on the lay shaft are fixed, while those on the main shaft are free to rotate
- Dog clutches are used to engage and disengage gears
Synchromesh Gearbox
- Similar to constant mesh gearbox, but with synchronizers instead of dog clutches
- Synchronizers allow for smooth gear changes by equalizing the speed of the gears before engagement
- Used in modern cars to reduce the cost of production
Automatic Gearbox
- Also known as automatic transmission
- Uses a complex system of gears, clutches, and hydraulic pumps to change gear ratios automatically
- Components:
- Torque converter
- Planetary gear sets
- Hydraulic system
- Control unit (TCU or TCM)
- Working:
- The TCU receives inputs from sensors and determines the appropriate gear ratio
- Hydraulic pressure is used to engage and disengage clutches and brake bands
- Shift points are determined by factors such as vehicle speed, engine load, and driver demand
Differential
- A mechanical device that allows each of the driving wheels to rotate at different speeds
- Purpose:
- To drive a pair of wheels with equal torque while allowing them to rotate at different speeds
- To prevent wheel spinning and road damage when turning
- Components:
- Pinion drive gear
- Crown wheel/ring gear
- Spider/planet gear
- Cross-pin
- Side/sun gear
- Differential case assembly
- Construction:
- The differential is an arrangement of gears that work together to allow the vehicle to take a turn smoothly
- The pinion gear is fixed to the propeller shaft and rotates the crown wheel
Suspension System
- The chassis of the vehicle is connected to the front and rear wheels through the medium of springs, shock absorbers, and axles
- Components:
- Springs
- Dampers (shock absorbers)
- Stabilizer (sway bar or anti-roll bar)
- Linkage system
- Functions:
- To eliminate road shocks from transmission to vehicle components
- To obtain good road holding while driving, cornering, and braking
- To keep the proper steering geometry
- To obtain a particular height to body structure
- To resist the torque and braking reactions
- To maintain the stability of the vehicle while traveling over rough roads
- To safeguard the occupants against road shocks and provide a riding comfort
Sprung Weight and Unsprung Weight
- Sprung weight: The weight of the vehicle body that is supported by springs
- Unsprung weight: The weight of the wheels, axles, and other parts of the vehicle that are not supported by springs
- Effects of unsprung weight:
- Controls the trade-off between wheel bump and vibration isolation
- Affects the ride quality and road noise
- Exacerbates wheel control issues under hard acceleration or braking### Types of Springs
- There are five types of springs: compression, compression-shear, steel reinforced, progressive, and face shear springs.
- Air springs are also used in air suspension systems, which can be adjusted up or down by supplying air pressure.
Leaf Spring Suspension
- Leaf spring suspension consists of a number of leaves of increasing lengths made of steel plates.
- The spring eye is mounted to the frame by a pin called shackle pin.
- The centre portion of the spring is attached to the front axle by a V-bolt.
- The stiffness or spring rate of the leaf spring is determined by its length, width, and thickness.
- Greater the number of leaves, higher the stiffness.
Air Suspension System
- Air springs are flexible bellows made of textile-reinforced rubber, containing compressed air.
- They are used to carry load on vehicles and provide elasticity or "springiness" when compressed.
- Air springs have three characteristics: they are soft when unloaded, they increase stiffness when loaded, and they maintain constant vehicle height.
- They provide optimum riding comfort in both lightly loaded and fully loaded conditions.
Shock Absorber
- Shock absorbers are used to control vibrations on springs, provide comfortable ride, and act flexible and rigid.
- They are used as a part of the suspension system and provide more resistance to the motion of the spring and road wheel.
- Types of shock absorbers include mechanical, hydraulic, and telescopic shock absorbers.
Telescopic Shock Absorber
- Construction consists of an upper eye attached to the axle, a lower eye attached to the chassis frame, and two-way valves.
- Working involves fluid flowing between the valves to produce a damping force.
- The damping force varies with the speed of the piston.
Types of Suspension System
- There are two basic types of suspension systems: front end suspension and rear end suspension.
- Front end suspension types include independent front suspension and rigid axle front suspension.
- Rear end suspension types include longitudinal leaf spring, transverse leaf spring, and coil spring rear end suspension.
Independent Front Suspension
- Developed in the 1930s to improve vehicle ride control and riding comfort.
- Each front wheel is mounted on its own axle and independently supported by a coil or torsion bar or leaf spring.
- Types of independent front suspensions include longitudinal, transverse, sliding, MacPherson Strut, parallelogram, trailing link, and vertical guide suspensions.
Transmission System
- The transmission system plays a crucial role in transferring power from the engine to the wheels, enabling the vehicle to move efficiently across different speeds and conditions.
- Components of a transmission system:
- Transmission (manual or automatic)
- Clutch (for manual transmission)
- Gearbox
- Differential
- Driveshaft (propeller shaft)
- Torque converter (for automatic transmission)
Functions of a Transmission System
- Gear ratio selection
- Torque multiplication
- Smooth power delivery
- Adaptability to driving conditions
- Efficiency improvement (modern transmission systems aim to optimize fuel efficiency and reduce emissions)
Clutches and Power Transmission
- The purpose of the clutch is to allow the driver to couple or decouple the engine and transmission.
- Requirements of a clutch:
- Pick up its load smoothly without grab or clatter
- Have a driven disc of low moment of inertia to permit easy shifting
- Damp out any vibration of the crankshaft to prevent gear clatter
- Require little pedal pressure to operate
- Be easy to adjust and service
- Be cheap to manufacture
Types of Clutches
- Positive clutches
- Merits: simple, no slip, no heat generated, compact, and low cost
- Friction clutches
- Merits: smooth engagement, can slip during engagement, high torque capacity
- Types:
- Single plate clutch
- Multi-plate clutch
- Centrifugal clutch
- Semi-centrifugal clutch
- Diaphragm spring single plate clutch
- Electro-magnetic clutch
- Overrunning clutch or free-wheel unit
Diaphragm Spring Single Plate Clutch
- Advantages:
- Compact design
- Easier to balance rotationally
- Uniformly distributed pressure on pressure plate
- No release levers required
- Minimum effort required to disengage the clutch
- Minimum internal friction
Multi-Plate Clutch
- Used in heavy transport vehicles, epicyclic gearboxes, and racing cars
- Advantages:
- Higher torque transmission capacity
- Compact design
Automatic Clutch
- Centrifugal clutch: automatically disengages when speed falls below a certain value and re-engages when speed rises above it
- Fluid coupling or fluid torque converter: used to transmit power between two rotating shafts without Interrupting the flow of power
Gear Box in an Automobile
- Necessity of gear box: to maintain engine speed at the most economical value under all conditions of vehicle movement
- Functions of a gear box:
- Torque ratio variation between engine and wheels
- Means of reversal of vehicle motion
- Transmission can be disconnected from engine by neutral position of gear box
Types of Gear Box
- Progressive type gear box
- Epicyclic (or) planetary type gear box
- Selective type gear box (e.g., constant mesh gear box with positive dog clutch, constant mesh gear box with synchromesh device, sliding mesh gear box)### Gearbox
- A gearbox is a mechanical device that uses gears to transmit and change the speed of rotation of a mechanical shaft
- Types of gearboxes:
- Constant mesh gearbox
- Synchromesh gearbox
- Automatic gearbox
Constant Mesh Gearbox
- All gears on the main shaft are in constant mesh with the corresponding gears on the lay shaft
- Gears on the lay shaft are fixed, while those on the main shaft are free to rotate
- Dog clutches are used to engage and disengage gears
Synchromesh Gearbox
- Similar to constant mesh gearbox, but with synchronizers instead of dog clutches
- Synchronizers allow for smooth gear changes by equalizing the speed of the gears before engagement
- Used in modern cars to reduce the cost of production
Automatic Gearbox
- Also known as automatic transmission
- Uses a complex system of gears, clutches, and hydraulic pumps to change gear ratios automatically
- Components:
- Torque converter
- Planetary gear sets
- Hydraulic system
- Control unit (TCU or TCM)
- Working:
- The TCU receives inputs from sensors and determines the appropriate gear ratio
- Hydraulic pressure is used to engage and disengage clutches and brake bands
- Shift points are determined by factors such as vehicle speed, engine load, and driver demand
Differential
- A mechanical device that allows each of the driving wheels to rotate at different speeds
- Purpose:
- To drive a pair of wheels with equal torque while allowing them to rotate at different speeds
- To prevent wheel spinning and road damage when turning
- Components:
- Pinion drive gear
- Crown wheel/ring gear
- Spider/planet gear
- Cross-pin
- Side/sun gear
- Differential case assembly
- Construction:
- The differential is an arrangement of gears that work together to allow the vehicle to take a turn smoothly
- The pinion gear is fixed to the propeller shaft and rotates the crown wheel
Suspension System
- The chassis of the vehicle is connected to the front and rear wheels through the medium of springs, shock absorbers, and axles
- Components:
- Springs
- Dampers (shock absorbers)
- Stabilizer (sway bar or anti-roll bar)
- Linkage system
- Functions:
- To eliminate road shocks from transmission to vehicle components
- To obtain good road holding while driving, cornering, and braking
- To keep the proper steering geometry
- To obtain a particular height to body structure
- To resist the torque and braking reactions
- To maintain the stability of the vehicle while traveling over rough roads
- To safeguard the occupants against road shocks and provide a riding comfort
Sprung Weight and Unsprung Weight
- Sprung weight: The weight of the vehicle body that is supported by springs
- Unsprung weight: The weight of the wheels, axles, and other parts of the vehicle that are not supported by springs
- Effects of unsprung weight:
- Controls the trade-off between wheel bump and vibration isolation
- Affects the ride quality and road noise
- Exacerbates wheel control issues under hard acceleration or braking### Types of Springs
- There are five types of springs: compression, compression-shear, steel reinforced, progressive, and face shear springs.
- Air springs are also used in air suspension systems, which can be adjusted up or down by supplying air pressure.
Leaf Spring Suspension
- Leaf spring suspension consists of a number of leaves of increasing lengths made of steel plates.
- The spring eye is mounted to the frame by a pin called shackle pin.
- The centre portion of the spring is attached to the front axle by a V-bolt.
- The stiffness or spring rate of the leaf spring is determined by its length, width, and thickness.
- Greater the number of leaves, higher the stiffness.
Air Suspension System
- Air springs are flexible bellows made of textile-reinforced rubber, containing compressed air.
- They are used to carry load on vehicles and provide elasticity or "springiness" when compressed.
- Air springs have three characteristics: they are soft when unloaded, they increase stiffness when loaded, and they maintain constant vehicle height.
- They provide optimum riding comfort in both lightly loaded and fully loaded conditions.
Shock Absorber
- Shock absorbers are used to control vibrations on springs, provide comfortable ride, and act flexible and rigid.
- They are used as a part of the suspension system and provide more resistance to the motion of the spring and road wheel.
- Types of shock absorbers include mechanical, hydraulic, and telescopic shock absorbers.
Telescopic Shock Absorber
- Construction consists of an upper eye attached to the axle, a lower eye attached to the chassis frame, and two-way valves.
- Working involves fluid flowing between the valves to produce a damping force.
- The damping force varies with the speed of the piston.
Types of Suspension System
- There are two basic types of suspension systems: front end suspension and rear end suspension.
- Front end suspension types include independent front suspension and rigid axle front suspension.
- Rear end suspension types include longitudinal leaf spring, transverse leaf spring, and coil spring rear end suspension.
Independent Front Suspension
- Developed in the 1930s to improve vehicle ride control and riding comfort.
- Each front wheel is mounted on its own axle and independently supported by a coil or torsion bar or leaf spring.
- Types of independent front suspensions include longitudinal, transverse, sliding, MacPherson Strut, parallelogram, trailing link, and vertical guide suspensions.
Transmission System
- The transmission system plays a crucial role in transferring power from the engine to the wheels, enabling the vehicle to move efficiently across different speeds and conditions.
- Components of a transmission system:
- Transmission (manual or automatic)
- Clutch (for manual transmission)
- Gearbox
- Differential
- Driveshaft (propeller shaft)
- Torque converter (for automatic transmission)
Functions of a Transmission System
- Gear ratio selection
- Torque multiplication
- Smooth power delivery
- Adaptability to driving conditions
- Efficiency improvement (modern transmission systems aim to optimize fuel efficiency and reduce emissions)
Clutches and Power Transmission
- The purpose of the clutch is to allow the driver to couple or decouple the engine and transmission.
- Requirements of a clutch:
- Pick up its load smoothly without grab or clatter
- Have a driven disc of low moment of inertia to permit easy shifting
- Damp out any vibration of the crankshaft to prevent gear clatter
- Require little pedal pressure to operate
- Be easy to adjust and service
- Be cheap to manufacture
Types of Clutches
- Positive clutches
- Merits: simple, no slip, no heat generated, compact, and low cost
- Friction clutches
- Merits: smooth engagement, can slip during engagement, high torque capacity
- Types:
- Single plate clutch
- Multi-plate clutch
- Centrifugal clutch
- Semi-centrifugal clutch
- Diaphragm spring single plate clutch
- Electro-magnetic clutch
- Overrunning clutch or free-wheel unit
Diaphragm Spring Single Plate Clutch
- Advantages:
- Compact design
- Easier to balance rotationally
- Uniformly distributed pressure on pressure plate
- No release levers required
- Minimum effort required to disengage the clutch
- Minimum internal friction
Multi-Plate Clutch
- Used in heavy transport vehicles, epicyclic gearboxes, and racing cars
- Advantages:
- Higher torque transmission capacity
- Compact design
Automatic Clutch
- Centrifugal clutch: automatically disengages when speed falls below a certain value and re-engages when speed rises above it
- Fluid coupling or fluid torque converter: used to transmit power between two rotating shafts without Interrupting the flow of power
Gear Box in an Automobile
- Necessity of gear box: to maintain engine speed at the most economical value under all conditions of vehicle movement
- Functions of a gear box:
- Torque ratio variation between engine and wheels
- Means of reversal of vehicle motion
- Transmission can be disconnected from engine by neutral position of gear box
Types of Gear Box
- Progressive type gear box
- Epicyclic (or) planetary type gear box
- Selective type gear box (e.g., constant mesh gear box with positive dog clutch, constant mesh gear box with synchromesh device, sliding mesh gear box)### Gearbox
- A gearbox is a mechanical device that uses gears to transmit and change the speed of rotation of a mechanical shaft
- Types of gearboxes:
- Constant mesh gearbox
- Synchromesh gearbox
- Automatic gearbox
Constant Mesh Gearbox
- All gears on the main shaft are in constant mesh with the corresponding gears on the lay shaft
- Gears on the lay shaft are fixed, while those on the main shaft are free to rotate
- Dog clutches are used to engage and disengage gears
Synchromesh Gearbox
- Similar to constant mesh gearbox, but with synchronizers instead of dog clutches
- Synchronizers allow for smooth gear changes by equalizing the speed of the gears before engagement
- Used in modern cars to reduce the cost of production
Automatic Gearbox
- Also known as automatic transmission
- Uses a complex system of gears, clutches, and hydraulic pumps to change gear ratios automatically
- Components:
- Torque converter
- Planetary gear sets
- Hydraulic system
- Control unit (TCU or TCM)
- Working:
- The TCU receives inputs from sensors and determines the appropriate gear ratio
- Hydraulic pressure is used to engage and disengage clutches and brake bands
- Shift points are determined by factors such as vehicle speed, engine load, and driver demand
Differential
- A mechanical device that allows each of the driving wheels to rotate at different speeds
- Purpose:
- To drive a pair of wheels with equal torque while allowing them to rotate at different speeds
- To prevent wheel spinning and road damage when turning
- Components:
- Pinion drive gear
- Crown wheel/ring gear
- Spider/planet gear
- Cross-pin
- Side/sun gear
- Differential case assembly
- Construction:
- The differential is an arrangement of gears that work together to allow the vehicle to take a turn smoothly
- The pinion gear is fixed to the propeller shaft and rotates the crown wheel
Suspension System
- The chassis of the vehicle is connected to the front and rear wheels through the medium of springs, shock absorbers, and axles
- Components:
- Springs
- Dampers (shock absorbers)
- Stabilizer (sway bar or anti-roll bar)
- Linkage system
- Functions:
- To eliminate road shocks from transmission to vehicle components
- To obtain good road holding while driving, cornering, and braking
- To keep the proper steering geometry
- To obtain a particular height to body structure
- To resist the torque and braking reactions
- To maintain the stability of the vehicle while traveling over rough roads
- To safeguard the occupants against road shocks and provide a riding comfort
Sprung Weight and Unsprung Weight
- Sprung weight: The weight of the vehicle body that is supported by springs
- Unsprung weight: The weight of the wheels, axles, and other parts of the vehicle that are not supported by springs
- Effects of unsprung weight:
- Controls the trade-off between wheel bump and vibration isolation
- Affects the ride quality and road noise
- Exacerbates wheel control issues under hard acceleration or braking### Types of Springs
- There are five types of springs: compression, compression-shear, steel reinforced, progressive, and face shear springs.
- Air springs are also used in air suspension systems, which can be adjusted up or down by supplying air pressure.
Leaf Spring Suspension
- Leaf spring suspension consists of a number of leaves of increasing lengths made of steel plates.
- The spring eye is mounted to the frame by a pin called shackle pin.
- The centre portion of the spring is attached to the front axle by a V-bolt.
- The stiffness or spring rate of the leaf spring is determined by its length, width, and thickness.
- Greater the number of leaves, higher the stiffness.
Air Suspension System
- Air springs are flexible bellows made of textile-reinforced rubber, containing compressed air.
- They are used to carry load on vehicles and provide elasticity or "springiness" when compressed.
- Air springs have three characteristics: they are soft when unloaded, they increase stiffness when loaded, and they maintain constant vehicle height.
- They provide optimum riding comfort in both lightly loaded and fully loaded conditions.
Shock Absorber
- Shock absorbers are used to control vibrations on springs, provide comfortable ride, and act flexible and rigid.
- They are used as a part of the suspension system and provide more resistance to the motion of the spring and road wheel.
- Types of shock absorbers include mechanical, hydraulic, and telescopic shock absorbers.
Telescopic Shock Absorber
- Construction consists of an upper eye attached to the axle, a lower eye attached to the chassis frame, and two-way valves.
- Working involves fluid flowing between the valves to produce a damping force.
- The damping force varies with the speed of the piston.
Types of Suspension System
- There are two basic types of suspension systems: front end suspension and rear end suspension.
- Front end suspension types include independent front suspension and rigid axle front suspension.
- Rear end suspension types include longitudinal leaf spring, transverse leaf spring, and coil spring rear end suspension.
Independent Front Suspension
- Developed in the 1930s to improve vehicle ride control and riding comfort.
- Each front wheel is mounted on its own axle and independently supported by a coil or torsion bar or leaf spring.
- Types of independent front suspensions include longitudinal, transverse, sliding, MacPherson Strut, parallelogram, trailing link, and vertical guide suspensions.
Transmission System
- The transmission system plays a crucial role in transferring power from the engine to the wheels, enabling the vehicle to move efficiently across different speeds and conditions.
- Components of a transmission system:
- Transmission (manual or automatic)
- Clutch (for manual transmission)
- Gearbox
- Differential
- Driveshaft (propeller shaft)
- Torque converter (for automatic transmission)
Functions of a Transmission System
- Gear ratio selection
- Torque multiplication
- Smooth power delivery
- Adaptability to driving conditions
- Efficiency improvement (modern transmission systems aim to optimize fuel efficiency and reduce emissions)
Clutches and Power Transmission
- The purpose of the clutch is to allow the driver to couple or decouple the engine and transmission.
- Requirements of a clutch:
- Pick up its load smoothly without grab or clatter
- Have a driven disc of low moment of inertia to permit easy shifting
- Damp out any vibration of the crankshaft to prevent gear clatter
- Require little pedal pressure to operate
- Be easy to adjust and service
- Be cheap to manufacture
Types of Clutches
- Positive clutches
- Merits: simple, no slip, no heat generated, compact, and low cost
- Friction clutches
- Merits: smooth engagement, can slip during engagement, high torque capacity
- Types:
- Single plate clutch
- Multi-plate clutch
- Centrifugal clutch
- Semi-centrifugal clutch
- Diaphragm spring single plate clutch
- Electro-magnetic clutch
- Overrunning clutch or free-wheel unit
Diaphragm Spring Single Plate Clutch
- Advantages:
- Compact design
- Easier to balance rotationally
- Uniformly distributed pressure on pressure plate
- No release levers required
- Minimum effort required to disengage the clutch
- Minimum internal friction
Multi-Plate Clutch
- Used in heavy transport vehicles, epicyclic gearboxes, and racing cars
- Advantages:
- Higher torque transmission capacity
- Compact design
Automatic Clutch
- Centrifugal clutch: automatically disengages when speed falls below a certain value and re-engages when speed rises above it
- Fluid coupling or fluid torque converter: used to transmit power between two rotating shafts without Interrupting the flow of power
Gear Box in an Automobile
- Necessity of gear box: to maintain engine speed at the most economical value under all conditions of vehicle movement
- Functions of a gear box:
- Torque ratio variation between engine and wheels
- Means of reversal of vehicle motion
- Transmission can be disconnected from engine by neutral position of gear box
Types of Gear Box
- Progressive type gear box
- Epicyclic (or) planetary type gear box
- Selective type gear box (e.g., constant mesh gear box with positive dog clutch, constant mesh gear box with synchromesh device, sliding mesh gear box)### Gearbox
- A gearbox is a mechanical device that uses gears to transmit and change the speed of rotation of a mechanical shaft
- Types of gearboxes:
- Constant mesh gearbox
- Synchromesh gearbox
- Automatic gearbox
Constant Mesh Gearbox
- All gears on the main shaft are in constant mesh with the corresponding gears on the lay shaft
- Gears on the lay shaft are fixed, while those on the main shaft are free to rotate
- Dog clutches are used to engage and disengage gears
Synchromesh Gearbox
- Similar to constant mesh gearbox, but with synchronizers instead of dog clutches
- Synchronizers allow for smooth gear changes by equalizing the speed of the gears before engagement
- Used in modern cars to reduce the cost of production
Automatic Gearbox
- Also known as automatic transmission
- Uses a complex system of gears, clutches, and hydraulic pumps to change gear ratios automatically
- Components:
- Torque converter
- Planetary gear sets
- Hydraulic system
- Control unit (TCU or TCM)
- Working:
- The TCU receives inputs from sensors and determines the appropriate gear ratio
- Hydraulic pressure is used to engage and disengage clutches and brake bands
- Shift points are determined by factors such as vehicle speed, engine load, and driver demand
Differential
- A mechanical device that allows each of the driving wheels to rotate at different speeds
- Purpose:
- To drive a pair of wheels with equal torque while allowing them to rotate at different speeds
- To prevent wheel spinning and road damage when turning
- Components:
- Pinion drive gear
- Crown wheel/ring gear
- Spider/planet gear
- Cross-pin
- Side/sun gear
- Differential case assembly
- Construction:
- The differential is an arrangement of gears that work together to allow the vehicle to take a turn smoothly
- The pinion gear is fixed to the propeller shaft and rotates the crown wheel
Suspension System
- The chassis of the vehicle is connected to the front and rear wheels through the medium of springs, shock absorbers, and axles
- Components:
- Springs
- Dampers (shock absorbers)
- Stabilizer (sway bar or anti-roll bar)
- Linkage system
- Functions:
- To eliminate road shocks from transmission to vehicle components
- To obtain good road holding while driving, cornering, and braking
- To keep the proper steering geometry
- To obtain a particular height to body structure
- To resist the torque and braking reactions
- To maintain the stability of the vehicle while traveling over rough roads
- To safeguard the occupants against road shocks and provide a riding comfort
Sprung Weight and Unsprung Weight
- Sprung weight: The weight of the vehicle body that is supported by springs
- Unsprung weight: The weight of the wheels, axles, and other parts of the vehicle that are not supported by springs
- Effects of unsprung weight:
- Controls the trade-off between wheel bump and vibration isolation
- Affects the ride quality and road noise
- Exacerbates wheel control issues under hard acceleration or braking### Types of Springs
- There are five types of springs: compression, compression-shear, steel reinforced, progressive, and face shear springs.
- Air springs are also used in air suspension systems, which can be adjusted up or down by supplying air pressure.
Leaf Spring Suspension
- Leaf spring suspension consists of a number of leaves of increasing lengths made of steel plates.
- The spring eye is mounted to the frame by a pin called shackle pin.
- The centre portion of the spring is attached to the front axle by a V-bolt.
- The stiffness or spring rate of the leaf spring is determined by its length, width, and thickness.
- Greater the number of leaves, higher the stiffness.
Air Suspension System
- Air springs are flexible bellows made of textile-reinforced rubber, containing compressed air.
- They are used to carry load on vehicles and provide elasticity or "springiness" when compressed.
- Air springs have three characteristics: they are soft when unloaded, they increase stiffness when loaded, and they maintain constant vehicle height.
- They provide optimum riding comfort in both lightly loaded and fully loaded conditions.
Shock Absorber
- Shock absorbers are used to control vibrations on springs, provide comfortable ride, and act flexible and rigid.
- They are used as a part of the suspension system and provide more resistance to the motion of the spring and road wheel.
- Types of shock absorbers include mechanical, hydraulic, and telescopic shock absorbers.
Telescopic Shock Absorber
- Construction consists of an upper eye attached to the axle, a lower eye attached to the chassis frame, and two-way valves.
- Working involves fluid flowing between the valves to produce a damping force.
- The damping force varies with the speed of the piston.
Types of Suspension System
- There are two basic types of suspension systems: front end suspension and rear end suspension.
- Front end suspension types include independent front suspension and rigid axle front suspension.
- Rear end suspension types include longitudinal leaf spring, transverse leaf spring, and coil spring rear end suspension.
Independent Front Suspension
- Developed in the 1930s to improve vehicle ride control and riding comfort.
- Each front wheel is mounted on its own axle and independently supported by a coil or torsion bar or leaf spring.
- Types of independent front suspensions include longitudinal, transverse, sliding, MacPherson Strut, parallelogram, trailing link, and vertical guide suspensions.
Braking System
- The braking system is a crucial component of a vehicle, used to slow and stop the vehicle.
- It converts kinetic energy into heat energy through friction between brake lining and brake drum.
- The braking system has four main requirements:
- Good anti-fade characteristics
- Consistency with safety
- No skidding while applying brakes
- Better cooling system
- The system should be strong enough to stop the vehicle within a minimum distance.
Types of Brakes
- Brakes are classified into several types based on:
- Application: Service brake, Parking brake
- Number of wheels: Two-wheel brake, Four-wheel brake
- Brake gear: Mechanical brake, Power brake
- Construction: Drum brake, Disc brake
- Location: Transmission brake, Wheel brake
- Method of braking contact: Internal expanding brake, External expanding brake
- Power unit: Cylinder brake, Diaphragm brake
- Power transmission: Direct acting brake, Geared brake
- Method of applying brake force: Single acting brake, Double acting brake
- Power employed: Vacuum brake, Air brake, Hydraulic brake, Hydrostatic brake, Electric brake
Drum Brakes
- There are two types of drum brakes:
- External contracting brake
- Internal expanding brake
- External contracting brake:
- Main components: Brake drum, bandwidth lining, operating lever, push rod, return spring, and adjusting lever
- Working: Push rod tightens the brake band around the drum to slow or stop the vehicle
- Disadvantages: Greater wear and tear
- Internal expanding brake:
- Main components: Brake drum, stationary plate, two brake shoes, anchor pins, and retracting spring
- Working: Cam turns and moves the brake shoes to create friction between the drum and shoes, slowing or stopping the vehicle
Disc Brakes
- A disc brake uses a caliper to squeeze brake pads against a rotating disc to create friction.
- Main components:
- Brake caliper
- Brake pads
- Rotor (brake disc)
- Types of disc brakes:
- Fixed caliper (swinging caliper) type
- Floating caliper type
- Sliding caliper type
Hydraulic Brakes
- Most modern cars use hydraulic brakes on all wheels with a hand brake to stop the rear wheel movement.
- The system uses liquid pressure to transmit the pedal force to the brake shoes.
- Main components:
- Master cylinder
- Wheel cylinder
- Working: When the brake pedal is applied, the master cylinder piston moves, increasing the pressure in the system, which forces the brake shoes against the brake drums.
Master Cylinder
- The master cylinder is the central unit in the hydraulic braking system.
- It produces the required hydraulic pressure to operate the system.
- Purposes:
- Build up the required hydraulic pressure
- Maintain a constant volume of fluid in the system
- Bleed or force air out of the brake line and wheel cylinder
- Construction: Made of cast iron, with brackets and holes for mounting, and two chambers: fluid reservoir and compression chamber
Vacuum Brake System
- Used in trains, operating on the principle of creating a partial vacuum inside a closed pipe system to generate braking force.
- Main components:
- Vacuum cylinder (brake cylinder)
- Vacuum pipe
- Ejector (vacuum generator)
- Control mechanism (driver's brake valve)
- Working:
- Application of brakes: Ejector creates a vacuum, which pushes the piston outward, applying pressure to the brake rigging and wheels.
- Release of brakes: Vacuum is released, and the piston returns to its original position, releasing the pressure on the brake rigging and wheels.
Air Brake System
- Used in trains and heavy vehicles, operating by using compressed air to apply and release brakes.
- Main components:
- Compressor
- Reservoir tanks
- Brake pipe
- Brake cylinder
- Control valve (triple valve)
- Working:
- Application of brakes: Reducing pressure in the brake pipe signals the triple valve to allow compressed air to enter the brake cylinders, applying the brakes.
- Release of brakes: Increasing pressure in the brake pipe back to normal level, venting the compressed air from the brake cylinders, and releasing the brakes.
Antilock Braking System (ABS)
- Prevents a vehicle's brakes from locking up and skidding during hard stops on wet or icy roads.
- The system depends on the coefficient of static friction between the tire and road.
- Improves safety by preventing skidding and maintaining traction.### Braking System
- When the tyre loses adhesion to the road while brakes are applied, the friction of brakes will be against drums or rotors, causing the wheel to lock and skid across the road.
- The braking force of the wheel is dependent on the sliding friction between the tyre and road, which is less than static friction.
- Under wet or icy conditions, the sliding friction is reduced, resulting in a longer stopping distance.
- Antilock Braking Systems (ABS) help prevent wheels from locking up, allowing the driver to control the vehicle under heavy braking.
Working Principle of ABS
- Wheel speed sensors are placed on each wheel to monitor speed.
- Each speed sensor has a toothed wheel that rotates at the same speed as the vehicle wheel or axle.
- The pulsed output from the wheel speed sensors goes to an ECU, which monitors each wheel speed relative to the speed of other wheels.
- When the brakes are applied and one or more wheels suddenly reduce speed, the ECU activates the antilock system.
Antilock System Operation
- Electrically operated solenoid valves are used to hold, release, and reapply hydraulic pressure to brakes.
- The controller senses a wheel locking up while braking and activates a solenoid to close a valve in the affected wheel brake line to prevent pressure from increasing further.
- If the locked wheel continues to lose speed, the controller activates a second solenoid to bleed pressure off the affected brake line.
- If the wheel regains traction and its speed increases, the solenoids are deactivated, and normal braking resumes.
Steering System
- Requirements:
- Keep the wheel in rolling motion without rubbing on the road.
- Associate with speed control.
- Be light and stable.
- Absorb road shocks.
- Be easily operated with minimal maintenance.
- Have self-centering action.
- Functions:
- Help in swinging the wheels to the left or right.
- Help in turning the vehicle at the driver's will.
- Provide directional stability.
- Minimize tyre wear and tear.
- Achieve self-centering efforts.
- Absorb road shocks.
Components of Steering System
- Steering Wheel
- Steering Column or Shaft
- Steering Gear
- Drop Arm or Pitman Arm
- Drag Link
- Steering Arm
- Track-Arms
- Track Rod or Tie-Rod
- Adjusting Screws
Types of Steering Gear Boxes
- Worm and Wheel Steering Gear
- Worm and Roller Steering Gear
- Re-circulating Ball type Steering Gear
- Rack and Pinion type Steering Gear
- Cam and Roller Gear type Steering Gear
- Cam and Peg Steering Gear
- Cam and Double lever Steering Gear
- Worm and Sector Type Steering Gear
Steering Gear Ratio or Reduction Ratio
- Defined as the number of turns on the steering wheel required to produce one turn of the steering gear cross shaft.
- Typically varies between 14.1 and 24.1.
Turning Radius
- The radius of the circle on which the outside front wheels move when the front wheels are turned to their extreme outer position.
- Typically 5 to 7.5 meters for buses and trucks.
Wheel Alignment
- Refers to the positioning of the front wheels and steering mechanism to provide directional stability and minimize tyre wear.
- Factors affecting wheel alignment:
- Wheel balance (static and dynamic)
- Tyre inflation
- Brake adjustments
- Steering linkages
- Suspension system
- Steering geometry
Steering Geometry
- Refers to the angular relationship between the front wheels and parts attached to it and the car frame.
- Includes:
- Caster angle
- Camber angle
- King-pin inclination
- Toe-in
- Toe-out
Caster Angle
- The angle between the backward or forward tilting of the king pin from the vertical axis at the top.
- Typically 2° to 4°.
Camber Angle
- The angle between the wheel axis and the vertical line at the top.
- Approximately 1/2° to 2°.
King-pin Inclination
- The angle between the vertical line and the king pin axis.
- Typically 7° to 8°.
Toe-in and Toe-out
- Toe-in: The amount by which the front part of the wheel points inwards.
- Toe-out: The difference in angles between the two front wheels and the vehicle frame during turning.
Reversible Steering
- When the deflection of road wheels is transmitted through the steering wheel to the road surface.
- Not desirable, but some degree of reversibility is needed to ensure the wheel returns to a straight position after taking a curve.
Steering Mechanisms
- Davis Steering Gear
- Ackermann Steering Gear
Davis Steering Gear
- Has a sliding pair, which results in more friction than the turning pair.
- Wear out earlier and become inaccurate after a certain time.
- Mathematically accurate.
- Consists of a cross link, sliding parallel to another link, and connected to the stub axle of the two front wheels by levers.
Ackermann Steering Gear
- Has only a turning pair.
- Not mathematically accurate except in three positions.
- Track arms are made inclined so that if the axles are extended, they will meet on the longitudinal axis of the car near the rear axle.
Power Steering
- Reduces the strain on the driver while negotiating sharp curves.
- Makes it easy to turn sharp corners.
- Usually arranged to be operative when the effort of steering wheel exceeds a pre-determined value.
- Fitted on heavy commercial vehicles and medium cars.
Steering Linkages
- A connection of various links between the steering gear box and the front wheels.
- The motion of the pitman arm and steering gear box is transferred to the steering knuckles of the front wheels through the steering linkages.
- Power steering systems typically use an engine-driven pump and hydraulic system to assist steering action.
Bleeding a Power Steering System
- Necessary to remove air from the system after replacing or repairing a hydraulic component.
- Procedure: Start the engine, turn the steering wheel fully from side to side, and check the fluid level, adding as needed.
Steering Wheel Play
- The most common problem in a steering system, caused by worn ball sockets, worn idler arm, or excessive clearance in the steering gearbox.
- Typically, the steering wheel should not be able to turn more than 1 1/2 inches without causing the front wheels to move.
- Can be checked using the dry-park test.
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Description
Learn about the key components and functions of a transmission system in automotive engineering, including gears and shafts that allow the engine's power to be transferred to the wheels.
