Unit 5: Braking System

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.

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.

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.

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.

Learn about the braking system, a crucial component of a vehicle, including its principle, mechanism, and conversion of kinetic energy to heat energy.