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Automotive Brake Systems Analysis and Design

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Engineering Design Handbook: Analysis and Design of Automotive Brake Systems.

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Analysis and Design of Automotive Brake Systems

This handbook treats the braking of motor vehicles such as passenger cars, trucks, and trailers. No attempt has been made to address fully the braking of specialty vehicles. However, the engineering relationships presented can be applied to the analysis of any automotive braking system, including those of tanks and special carriers. The text is structured so that it can be used by junior engineers with a minimum of supervision provided by a senior engineer. Chapters 2, 3, 4, 5, and 6 present the analysis of brake system components and should provide sufficient detail for the computations required for the analysis of entire brake systems. Chapter 7 and those that follow address the analysis and design of the brake system of motor vehicles including the computation of partial braking performance with the brake system in a failed condition. The examples in Chapter 14 are presented in considerable detail to provide the engineer with insight into the methodology used in solving brake problems. A brief description of brake system hardware is provided in Chapter 15 for the engineer not fully familiar with the functioning of various brake system components.

TOC

LIST OF ILLUSTRATIONS
LIST OF TABLES
PREFACE

CHAPTER 1. INTRODUCTION
List of Symbols Factors Influencing Stopping Distance
Braking Dynamics Methods to Improve Braking Capability
Overview of Brake System Design

CHAPTER 2. MECHANICAL ANALYSIS OF FRICTION BRAKES
List of Symbols 2-1
Different Brake Designs 2-2
Brake Shoe Displacement and Application 2-2
Brake Shoe Adjustment 2-3
Torque Analysis of Friction Brakes 2-4
Self-Energizing and Self-Locking 2-4
Leading and ^railing Shoe 2-6
Pressure Distribution Along Brake Lining 2-7
Lining Wear and Pressure Distribution 2-8
Brake Factor and Brake Sensitivity 2-9
Brake Factor of a Caliper Disc Brake 2-10
Brake Factor of a Leading-Trailing Shoe Brake With Pivot on Each Shoe 2-11
Brake Factor of a Two-Leading Shoe Brake With Pivot on Each Shoe 2-11
Brake Factor of a Leading-Trailing Shoe Brake With Parallel Sliding Abutment 2-12
Brake Factor of a Two-Leading Shoe Brake With Parallel Sliding Abutment 2-12
brake Factor of a Leading-Trailing Shoe Brake With Inclined Sliding Abutment 2-12
Brake Factor of a Two-Leading Shoe Brake With Inclined Sliding Abutment 2-13
Brake Factor of a Duo-Servo Brake With Eliding Abutment 2-13 2-4. 14
Brake Factor of a Duo-Servo Brake With Pivot Support 2-13 2-5
Effect of Shoe and Drum Stiffness on Brake Torque 2-13 2-6
Analysis of External Band Brakes 2-15 2-7
Analysis of Self-Energizing Disc Brakes 2-16 2- 8
Comparison of Brakes 2-18
References 2-18

CHAPTER 3. THERMAL ANALYSIS OF FRICTION BRAKES
List of Symbols 3-1 3-1
Temperature Analysis 3-2
The Friction Brake as a Heat Exchanger 3-2
Fundamentals Associated With Brake Temperature Analysis 3-7
Prediction of Brake Temperature During Continued Braking 3-5
Prediction of Brake Temperature During a Single Stop 3-6
Prediction of Brake Temperature During Repeated Braking 3-7
Prediction of Convective Heat Transfer Coefficient 3-8
Computer Equations for Predicting Brake Temperature 3-12
Analysis of Sealed Brakes 3-14 3-2 Thermal Stress Analysis 3-16
Fundamentals Associated With Thermal Cracks 3-16
Thermal Stresses in Solid-Rotor Disc Brakes 3-18
Thermal Stresses in Brake Drum 3-19
References 3-19

CHAPTER 4.
ANALYSIS OF AUXILIARY DRAKES 4- 0
List of Symbols 4-1 4-1 Exhaust Brakes 4-1
Hydrodynamic Retarders 4-2
Electric Retarders 4-3
Analysis of Integrated Retarder/Foundation Brake Systems 4-4
References 4-6

CHAPTER 5.
BRAKE FORCE PRODUCTION
List of Symbols 5-1
Introduction 5-2
Non powered Hydraulic Brake System 5-2
Vacuum-Assisted Hydraulic Brake System 5-6
Full-Power Hydraulic Brake System 5-11
Air Brake System 5-14
Compressed Air-Over-Hydraulic Brake System 5-15
Mechanical Brake System 5-16
Surge Brakes 5-18
Electric Brakes 5-18
References 5-18

CHAPTER 6.
TIRE-ROAD FRICTION 6-0
List of Symbols 6-1
Tire- Road Interface 6-1
Road Friction Measurement 6-1
Tire Friction Characteristics 6-2
Tire Rolling Resistance 6-3
Tire Design and Composition 6-4
References 6-5

CHAPTER 7.
VEHICLE BRAKING PERFORMANCE
List of Symbols 7-1
Braking Performance Measures 7-1
Effectiveness 7-1 7-1.2
Efficiency 7-2
Response Time 7-2
Controllability 7-2
Thermal Effectiveness 7-2
Brake Force Modulation 7-2
Braking Performance Prediction and Analysis 7-3
Braking Performance Calculation Program 7-3
Dynamic Braking Program 7-6
Tractor-Trailer Braking and Handling Program 7-6
Vehicle Drags 7-7 7-4.1 Rolling Resistance 7-7
Aerodynamic Drag 7-7
Viscous Damping Drag 7-8
Drag Due to Turning 7-8 Engine
Drag 7-8
References 7-8

CHAPTER 8. BRAKING OF VEHICLES EQUIPPED WITH FIXED RATIO BRAKING SYSTEM
List of Symbols 8-1
Braking of Two-Axle Vehicle 8-4
Dynamic Brake Force 8-4
Actual Brake Force Distribution 8-6
Tire-Road Friction Utilization 8-7
Braking Efficiency 8-8
Optimum Brake Force Distribution for Straight-Line Braking 8-9
Straight-L.inc Versus Curved Path Braking Performance 8-12
General Braking Efficiency 8-15
Vehicle Stability Considerations 8-17
Braking of Tandem Axle Truck 8-18
Walking Beam Suspension 8-19
Two-Elliptic Leaf Spring Suspension 8-21
Air Suspension 8-25
Braking of Tractor-Semitrailer Combination Without Tandem Axles 8-25
Dynamic and Actual Brake Forces 8-25
Optimum Brake Force Distribution 8-27
Straight-Line Versus Curved Path Braking Performance 8-30
Vehicle Stability Considerations 8 -3
Braking of Tractor-Semitrailer Combination Equipped With Tandem Axles 8-31
Two-Axle Tractor Coupled to a Trailer Equipped With a Two-Elliptic Leaf Spring Suspension 8-31
Two-Axle Tractor Coupled to a Trailer Equipped With a Walking Beam Suspension 8-34
Three- Axle Tractor Equipped With a Walking Beam Suspension Coupled to a Trailer Equipped With a Two-Elliptic Leaf Spring Suspension 8-34
Braking of a Two- Axle Tractor Coupled to a Single- Axle Semitrailer and a Double Axle Trailer 8-37
Braking of Combat Vehicles 8-38
Effects of Rotational Energies 8-38
Tract Rolling Resistance 8-39
Braking of Half-Track Vehicle 8-39
Braking of Full-Track Vehicle and Special Carriers 8-39
Concluding Remarks on Vehicles Equipped With Fixed Ratio Braking Systems 8-39
References 8-40

CHAPTER 9.
BRAKING OF VEHICLES EQUIPPED WITH VARIABLE RATIO BRAKING SYSTEMS
List of Symbols 9-1
Two-Axle Vehicles 9-2
Dynamic and Actual Brake Forces 9-2
Optimum Variable Ratio Braking Distribution 9-3
Dynamic Brake Line Pressures 9-4
Pedal Force Requirements 9-5 P
Pressure Regulating Valves 9-5
Straight-Line Versus Curved Line Braking Performance 9-6
Vehicle Stability Considerations 9-7
Braking of Tractor-Semitrailer Vehicle 9-7
Dynamic and Actual Brake Forces 9-7
Dynamic Brake Line Pressures 9-12
Pressure Variation as Function of Suspension Deflection 9 15
Two-AxleTractor Coupled to a Trailer Equipped With Two-Elliptic Leaf Spring Suspension 9-15
Three- Axle Tractor Equipped With Walking Beam Suspension Coupled to a Trailer Equipped With Two-Elliptic Leaf Spring Suspension 9-16
Concluding Remarks on Vehicle Equipped With Variable Ratio Braking Systems 9-18
References 9-19

CHAPTER 10.
WHEEL-ANTI LOCK BRAKE SYSTEMS
List of Symbols 10-1
Fundamentals Associated With Antilock Brake System Analysis 1 0-1
Hydraulic Vacuum Powered Systems 10-6
Wheel-Antilock Control Systems 10-6
Analysts of Vacuum-Powered Systems 10-8
Hydraulic Pump Pressurized Systems 10-9 Pneumatic Systems 10-11
Straight-Line Versus Curved Path Performance 10-12
Theoretical and Experimental Results 10-13
Different Antiskid System Designs 10-15
References 10-16

CHAPTER 11.
DYNAMIC ANALYSIS OF BRAKE SYSTEMS
List of Symbols 1 1
Fundamentals of Response Time Analysis 11-1
Hydraulic Brake Systems 1 1-1
Pneumatic Brake Systems 11.3
References 11.5

CHAPTER 12.
BRAKE SYSTEM FAILURE
List of Symbols 12-1
Basic Considerations 12-1
Development of Brake Failure 12-1
Development of Drum and Rotor Failure 12-4
Brake Failure Analysis 12-5
Brake Line Failure 12-5
Vehicle Deceleration 12-6
Pedal Force 12-7
Braking Efficiency 12-7
Pedal Travel 12-7
Performance Calculation 12-9
Improved Dual Brake System Design 12-11
Comparison of Dual Brake Systems 12-14
Vacuum Assist Failure 12-16
Failure of Full Power Hydraulic Brake Systems 12-16
Failure of Pneumatic Brake Systems 12-16
Brake Fade 12-17
Brake Assembly Failure Due to Excessive Temperature 12-17
Consequences of Brake Failure 12-18
Brake System Component Deterioration 12-18
Vehicle Stability and Controllability 12-19
Human Factors Considerations 17-19
Effect of Maintenance on Brake Failure 12-20
Minimizing Brake Failure Through Proper Design 12-21
References 12-21

CHAPTER 13.
TESTING OF VEHICLE BRAKE SYSTEMS
List of Symbols 13-1
Basic Testing Requirements 13-1
General Outline of a Brake Test Standard 13-1
Effectiveness 13-3.2
Efficiency 13-3.3
Response Time 13-3.4
Controllability 13-3.5
Thermal Effectiveness 13-4
Brake Usage and Maintenance 13-5
Brake System Inspection and Diagnosis 13-6
Brake System Testing 13-6.1
Roller Dynamometer 13-6.2
Platform Tester 13-6.3
Brake Road Testing 13-7
Brake Test Procedures for Military Vehicles .. 1 3-7. 1
Road Test Procedures for Wheeled Vehicles 1 3-7.2
Road Test Procedures for Tracked Vehicles 13.8
Component Testing References

CHAPTER 14.
DESIGN APPLICATIONS
List of Symbols
Basic Considerations
Specific Design Measures
Design of Related Components Such as Suppression, Tires, and Rims
Brake System Design Check
Brake Factor Calculation
Design of Light Truck Brake System
Emergency Brake Analysis
Dynamic Brake Forces
Braking Efficiency Braking Peiformap.ee Diagram
Brake Fluid Volume Analysis Specific
Design Measures
Design of Truck Proportional Brake System
Fixed Ratio Braking — Drum Brakes
Variable Ratio Braking — Drum Brakes
Variable Ratio Braking — Disc Brakes
Design of Tank Disc Brakes
Mechanical Analysis
Thermal Analysis Temperature Analysis of Drum Brake System
Design of Full Power Hydraulic Brake System for Trucks
Determination of Wheel Cylinder Areas Determination of Booster and Accumulator Size

CHAPTER 15.
BRAKE SYSTEMS AND THEIR COMPONENTS
Pedal Force Transmission — Hydraulic Brakes
Basic Principles of Hydraulic Brakes
Single Circuit Brake System
Dual Circuit Brake System
Standard Master Cylinder
Tandem Master Cylinder
Stepped Master Cylinder
Stepped Bore Tandem Master Cylinder
Brake Torque Production.
Drum Brakes
Basic Brake Shoe Configuration
heel Cylinder
Wedge Brake.
S" Cam Brake
B rake Shoe Adjustment
Disc Brakes Basic Configuration
Parking Brake
Brace Force Distribution Valve
Hydraulic Brake Line
Vacuum Assist Systems
Compressed Air-Over-Hydraulic Brake System
Compressed Air Brakes
Secondary Brake Systems