Automotive Chassis Engineering

Table of Contents

1. Frontmatter

2. Chapter 1. Vehicle Mechanics

   David C. Barton, John D. Fieldhouse

   Abstract

   Before embarking on the focus of this book which is on particular and detailed aspects of chassis engineering, it was felt necessary to provide a basic understanding of the dynamic forces experienced by any road vehicle during normal operation. This chapter introduces such forces on a vehicle when considered as a rigid body. It discusses the source of each force in some detail and how they may be applied to predict the performance of a vehicle. It extends the normal straight-line driving to include non-steady state cornering and the case of car-trailer combinations. Each section generally includes typical problems with detailed solutions.

3. Chapter 2. Deceleration Behaviour

   David C. Barton, John D. Fieldhouse

   Abstract

   In addition to the dynamic forces experienced by a vehicle during normal operation, there are decelerating forces induced by the driver. Such induced forces emanate from the braking system as the driver actuates the system in order to decelerates the vehicle in a controlled manner, and indeed to bring the vehicle to a stop and hold it in that state. This chapter firstly discusses the conventional hydraulic braking system fitted to the majority of passenger cars and light commercial vehicles. This discussion includes the design methodology and the primary components within the hydraulic system, and their configurations, that ensure safe deceleration even if the system partly fails due to deterioration, such as oil leaks. The chapter proceeds to study the kinematic analysis of any braking vehicle, beginning with a static analysis and then moving towards brake proportioning and adhesion utilisation. The discussion concentrates on a constant front/rear brake ratio but also introduces the concept of variable brake ratio. The chapter also considers wheel locking and its effects on vehicle stability, along with pitching of the vehicle. Advanced systems such as Anti-lock Braking Systems (ABS) are discussed and regenerative braking via an electric powertrain is briefly covered.

4. Chapter 3. Suspension Systems and Components

   David C. Barton, John D. Fieldhouse

   Abstract

   Suspension system design is as much about quality/refinement as being a handling/safety issue. This chapter begins by considering the kinematic requirements of any suspension system before discussing common suspension systems for both dependant and independent designs. Both front and rear suspension designs are considered. The chapter continues with a detailed analysis of the suspension system components—tyres, linkages, springs and dampers—the latter including active damping. It aims to extend the understanding of load transfer when body roll is considered along with the effects of sprung and unsprung masses. Both anti-squat and anti-dive designs are also studied. The chapter concludes with a quarter vehicle analysis whereby body bounce and wheel hop modes are identified as areas of interest. The chapter includes many numerical examples to better explain the theory and demonstrate their application.

5. Chapter 4. Steering Systems

   David C. Barton, John D. Fieldhouse

   Abstract

   The primary purpose of this chapter is to provide the automotive engineer with a basic understanding of steering systems. It reviews current and modern designs with accompanying theories regarding the forces within the systems, both static and dynamic. It considers power assistance and the move towards steer-by-wire as full electronic control becomes increasingly reliable. The theory is supported by worked examples and “case studies” that more readily demonstrate their application. As such the engineer should be in a position to develop appropriate in-house computer-aided design packages that meet a specific need without unnecessary peripheral features. The chapter begins by introducing requirements and regulations that govern the basic design strategies. It continues with consideration of steering geometry and current common designs. The forces imposed on the steering system, both for a stationary and moving vehicle, are introduced along with the move towards electric steering systems. The chapter concludes by considering four wheel steer and additional steering assistance.

6. Chapter 5. Vehicle Structures and Materials

   David C. Barton, John D. Fieldhouse

   Abstract

   This chapter commences with a review of chassis structures for the different classes of road vehicles including mass-produced passenger cars, high performance vehicles, small sports cars and commercial vehicles. It proceeds to consider the different materials used in vehicle structures with a focus on reducing vehicle weight and therefore carbon emissions through the use of high strength steel, aluminium and composite materials. The following section outlines different methods of analysis of vehicle structures including both traditional theoretical methods and modern computational techniques. Crash safety of vehicles under impact loading is then considered and a particular case study of the crashworthiness of a small space frame sports car is presented in detail. The final section of the chapter deals with the durability assessment of vehicle structures and again includes a detailed case study of the fatigue assessment and optimisation of a suspension component.

7. Chapter 6. Noise, Vibration and Harshness (NVH)

   David C. Barton, John D. Fieldhouse

   Abstract

   This chapter aims to provide chassis engineers with knowledge of the background theory and techniques so that they can make informed judgements on NVH solution strategies at an early stage of vehicle development. The Chapter commences with a review of the fundamentals of acoustic theory as this topic is often not covered in detail in Bachelor level engineering programmes. The human response to sound is then outlined followed by a description of general noise measurement and control techniques. The main sources of noise in road vehicles are then reviewed and common assessment and mitigation techniques are outlined for each type of noise. The next section introduces the sources and nature of automotive mechanical vibration as distinct from air-borne noise. There is a focus on vibration arising from the internal combustion engine since this remains the predominant motive power source for the majority of road vehicles. Principles of vibration control are then described with a focus on vibration absorbers and the isolation of engine-induced vibration. The final section of the chapter deals with the particular problems of brake noise and vibration, the latter affecting not only the brake itself but also the entire chassis due to transmission of the vibration through the suspension and steering systems.

8. Backmatter