The automotive chassis: Volume 1: Components design

Mechanical Engineering Series

Giancarlo Genta

Lorenzo Morello

The Automotive

Chassis

Volume 1: Components Design

Second Edition

Mechanical Engineering Series

Series Editor

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Minnesota, Minneapolis, MN, USA

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Giancarlo Genta • Lorenzo Morello

The Automotive Chassis

Volume 1: Components Design

Second Edition

123

Giancarlo Genta

Politecnico di Torino

Turin, Italy

Lorenzo Morello

Politecnico di Torino

Turin, Italy

ISSN 0941-5122 ISSN 2192-063X (electronic)

Mechanical Engineering Series

ISBN 978-3-030-35634-7 ISBN 978-3-030-35635-4 (eBook)

https://doi.org/10.1007/978-3-030-35635-4

1st edition: © Springer Science+Business Media B.V. 2009

2nd edition: © Springer Nature Switzerland AG 2020

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Foreword

Each book—even one that at first glance might seem like a “cold” university

engineering text—tells a fascinating story of experience and knowledge.

When I was invited to write an introduction to this volume, based on the

experiences of a great professor and a very experienced industrial manager, I felt

the pleasant feeling of a puzzle just completed: the text has, in fact, achieved the

important goal of helping readers understand what it really means to move from the

concept to the creation of a new car, from design to assembly.

To describe the impact of the text, it is sufficient to highlight how the authors’

passion for creating this manual—so much so that it has become an international

point of reference in the design of chassis—coincides substantially with the

enthusiasm of the thousands of people who work every day at Fiat Chrysler

Automobiles with the aim of conceiving and creating cars that are increasingly

innovative.

Before they even start studying on these pages, I would like students to be aware

that creating a new car—or even just contributing to its birth—is a fascinating job,

made up of successive joints of creative and technical skills, which requires an

extraordinary commitment. The same commitment needed to lay the foundations

for new engineers to grow and make their contribution to creating ever more

cutting-edge cars.

Flipping through the pages of the book and investigating the various design

steps, it is clear that the authors have achieved an important objective: to give due

importance to the fact that a university text must not only tell the theory on how to

build new cars, but also describe in a coherent and comprehensive way the content

of a car starting from the manufacturer’s point of view, sometimes very different

from the theory, too often the only subject in university texts.

And in telling this small story of effective integration between the world of study

and the world of work, I rediscover a bit of the experiences I lived first by studying

Engineering at the University and then working in Fiat Chrysler Automobiles: I find

out how much effort and dedication both paths have taken. But, above all, how

much satisfaction can they bring.

v

The approach used by the authors shows the indissoluble link between the

academic system and the professional paths that a car company like FCA is able to

offer, making it well understood that “knowing how to do” is very different from

“doing” but that the two voices together are a winning combination, an essential

method to always keep up with the times and make a difference in a context in

which knowledge remains the fundamental competitive advantage.

Torino, Italy

June 2019

Daniele Chiari

Head of Product Planning &

Institutional Relations, FCA, Emea

vi Foreword

Foreword to the Second Edition

It is a great pleasure and honor for me to write the foreword to the second edition of

The Automotive Chassis.

First of all, I want to express the gratitude that I have for the authors, who have

been great masters of my education: Professor Genta as my Tutor at Politecnico di

Torino and Professor Morello as Head of Engineering at Fiat Auto. Their inno￾vative, methodical, rational approach, and their effort to promote and develop the

technical competence have helped to form my core values and beliefs.

The two books of The Automotive Chassis represent an exceptional masterpiece

that has been useful in these years to the engineering students and also to the

automotive engineers of my generation. Thanks to this work, we have further

developed our knowledge of the most complex and fascinating area of the vehicle

where the real technical competence of the engineer is tested.

In this second edition, the first book maintains its robust and structured approach

to “Components Design” and the second book on “Systems Design” has been

further enriched and updated according to the rapid growth of our car industry

toward NEVs and Autonomy. With these actions, The Automotive Chassis will

continue its role of spreading the chassis engineering culture in our fascinating

automotive world.

Shangai, China

April 2019

Giorgio Cornacchia

Head of APAC Product

Development at FCA

vii

Preface

This book is the result of a double decades-long experience: from one side a

teaching experience of courses such as Vehicle Mechanics, Vehicle System Design,

Chassis design, and more to students of Engineering, from the other side from the

design praxis of vehicle and chassis components in a large automotive company.

This book is primarily addressed to students of Automotive engineering and sec￾ondarily to all technicians and designers working in this field. It also addressed to

all people enthusiast of cars that are looking for a technical guide.

The tradition and the diversity of disciplines involved in road vehicle design lead

us to divide the vehicle into three main subsystems: the engine, the body, and the

chassis.

The chassis isn’t today a visible subsystem anymore, tangible as a result of a

certain part of the fabrication process, while engine and body are; chassis com￾ponents are assembled, as a matter of fact, directly on the body. For this reason, the

function of the chassis cannot be assessed separately from the rest of the car.

As we will see better, reading the chapters dedicated in the first and in the second

part of this book, to the historical evolution, the situation was completely different

in the past; in the first cars the chassis was defined as a real self-moving sub￾assembly that included the following:

• a structure, usually a ladder framework, able to carry on all the remaining

components of the vehicle;

• the suspensions for the mechanical linkage of wheels with the framework;

• the wheels completed with tires;

• the steering system to change wheel angles accordingly to the vehicle path;

• the brake system to reduce the speed or to stop the vehicle;

• the transmission to apply the engine torque to the driving wheels.

This group of components, after the engine assembly, was able to move

autonomously; this happened at least in many experimental tests, where the body

was simulated with a ballast and during the fabrication process, to move the chassis

from the shop of the carmaker to that of the body maker.

ix

Customers often bought from the carmaker a chassis to be completed later on by

a body maker, according to their desire and specification.

On contemporary vehicles, this particular architecture and function is only

provided for industrial vehicles, with the exception of buses where the structure,

even if built by some body maker, participates with the chassis framework to the

total stiffness, such as a kind of unitized body.

On almost every car, the chassis structure cannot be separated from the body as

being part of its floor (platform); sometime some auxiliary framework is also added

to interface suspensions or power train to the body and to enable their pre-assembly

on the side of the main assembly line.

Nevertheless, tradition and some particular technical aspect of these components

have justified the development of a particular discipline within vehicle engineering;

as a consequence, almost all car manufacturers have a technical organization

addressed to the chassis, separated from those addressed to the body or to the

engine.

A new reason has been added in recent times to justify a different discipline and

a specific organization and is the setting up of the so-called technological platforms:

the modern trend of the market calls for an unprecedented product diversification,

never reached in the past; sometimes marketing expert calls this phenomenon

fragmentation.

This high diversification couldn’t be sustained with acceptable production cost

without a strong cross standardization of non-visible or of non-specific part of a

certain model.

This situation has been very well known since years to all industrial vehicle

manufacturers. The term platform implying the underbody and the front side

members, with the addition of the adjective technological, describes a set of

components substantially equal to the former chassis; the particular technical and

scientific issues, the different development cycle, and the longer economic life have

reinforced the specificity of engineers that are dedicated to this car subsystem.

The contents of this book are divided into five parts, organized into two

volumes.

The first volume describes main chassis subsystems in two parts.

The first part describes the main components of the chassis from the tire to the

chassis structure, including wheels, suspension, steering, and braking systems, not

forgetting the control systems that show an increasing importance, due to the

diffusion of active and automatic systems.

The second part is addressed to the transmission and to the related components;

the complexity of this topic justifies a separated presentation.

It should be noticed that, by many car manufacturers, the engineering and

production organization dedicated to this subsystem are integrated into the power

train organization, instead of the chassis organization. This has obviously no

influence on the technical contents of this book and can be justified by the stan￾dardization issues and by the life cycle of this component, in certain aspects more

similar to the engine than to the chassis.

x Preface

The explanation approach of the chassis components assumes the existence of a

general knowledge of the mechanical components that can be gathered through a

conventional machine design course. Topics that can be found on a non-specific

course are not treated. In particular, gears design in the second part will not be

approached exhaustively, as well as shafts, bearing, and seals design.

Nevertheless, in many parts of this book, design and testing knowledge that are

usually not approached in general purpose design courses are introduced and

discussed.

We also decided to spend two chapters on the historical evolution of the auto￾motive product; they should enable the reader to appreciate the technical progress

of the car in its first 120 years of life. In the opinion of the authors, this subject is a

useful technical training and proves to be sometimes useful for inspiration too.

Only architectures that are typical to the most diffused road vehicles will be

considered: cars with some mention to industrial vehicles, without considering

other applications as motor bicycles, tractors, or earth moving machines and

quadricycles.

The second volume is divided into three parts and is entirely addressed to the

chassis as a system, putting in evidence the contribution of the chassis to the vehicle

performance, as perceived by the customer and as imposed by the legislation rules.

The third part is dedicated to an outline of the functions that the vehicle is

expected to perform, of the customers’ expectations and to the legislation.

In the fourth part, the influence of the chassis design for the vehicle performance

is explained. Particularly, the longitudinal, transversal, and vertical dynamics are

explained, with its influence on speed, acceleration, consumption, breaking

capacity, and maneuverability (or handling) and comfort.

The fifth part is addressed to mathematical models of the chassis and, more in

general, of the vehicle. As known, car engineers take more and more advantage

from mathematical models of virtual prototypes and perform numerical testing of

prototypes before they are available for physical tests.

Even if mathematical models are based upon calculation codes that are prepared

by specialist, and are available on the market, we think to be necessary to supply the

students with a clear idea of the methods at the base of these codes and on the

approximations that these codes imply. The purpose of this part isn't to enable

specialists to built up their models, but to suggest a correct and responsible usage

of their results.

The two books are completed by five appendices.

The first appendix recalls some notion on system dynamics, useful to understand

the setting up of mathematical models that are introduced in the fourth and fifth

parts.

The second appendix is dedicated to two-wheeled vehicles. The study of

two-wheeled vehicles, for some aspects more complicated than for four-wheeled

vehicles, is very particular and has nothing to do with cars; in addition to that,

industries that produce motorcycles are very well separated from the car industry.

Preface xi

Nevertheless, there are disciplines common to the two worlds, due to the fact

that both vehicles use pneumatic tires as interface with the ground; some knowledge

exchange between the two vehicle engineers could be of mutual benefit.

The third appendix is dedicated to the particular issues that should be faced when

vehicles on wheels will be developed for planets or environments different as the

earth. Starting from the only vehicle of this kind that was developed for the Apollo

Project, similarities and differences between conventional vehicles and those that in

the future could be utilized for interplanetary exploration.

The fourth appendix analyzes some mathematical approach, sometimes very

simplified to interpret the motion of cars after the impact due to an accident.

The last appendix reports the main data of vehicles of different kinds that are

used in some explanatory example in the book; these data could also enable the

student to practice their skills on exercises with a minimum of realism.

Turin, Italy Giancarlo Genta

Lorenzo Morello

xii Preface

Acknowledgements

The authors wish to thank Fiat Research Center for having made possible the

preparation of these two volumes, not only by supporting the cost of this work, but

also by supplying a lot of technical material that contributed to update the content

of these books and to orient them to practical applications.

Particularly, the authors appreciated the many suggestions and information they

received from Isabella Anna Albe Camuffo, Kamel Bel Knani, Roberto Cappo,

Paolo Mario Coeli, Silvio Data, Roberto Puppini, and Giuseppe Rovera.

The first volume of this work has, in addition, benefited of the lecture notes

prepared by Fiat Research Center, to sustain the teaching activity of the courses of

Vehicle System Design, Chassis Design, and Automotive Transmission Design,

within the course of Automotive Engineering of the Politecnico of Turin and of the

Master in Automotive Engineering of the Federico II University of Naples.

The authors’ gratitude must also be shown to the Companies that have supplied

part of the material used for the illustrations, mainly in the first volume; in

alphabetical order, we remember: Audi, Fiat Chrysler Automobiles (FCA, formerly

Fiat Auto), Getrag, Honda, Iveco, Marelli, Mercedes, Shaeffers, and Valeo. Without

their contribution, this book haven't been complete and, for the time being, topical.

Particular thanks are conveyed to Donatella Biffignandi of the Automobile

Museum of Turin for the help and material supplied for the preparation of the

historical sections.

xiii

About the Authors

Giancarlo Genta got a degree in aeronautical engineering in 1970 and in aero￾space engineering in 1971 at the Politecnico of Turin. He started immediately after

his career at the Politecnico as Assistant of Machine Design and Technologies.

He has been Visiting Professor of Astronautical Propulsion Systems since 1976

and of Vehicle Mechanics since 1977 and, more recently, of Vehicle System Design

at the course of Mechanical Engineering and Automotive Engineering.

He was appointed Associate Professor of Aeronautical Engines Design in 1983,

at the Aerospace Engineering School of the Politecnico of Turin; he was appointed

full professor of the same course in 1990.

He was elected Director of the Mechanical Engineering Department of the

Politecnico from 1989 to 1995. He has been holding the course of Applied Stress

Analysis II for the Master of Science of the University of Illinois at the Politecnico

of Turin.

He also held many courses in Italy and abroad, in the frame of development

cooperation projects, in Kenya (2 years), Somalia (6 months), India (1 month), and

at the Bureau International du Travail.

He has been Honorary Member of the Academy of Sciences of Turin, since

1996, and of the International Academy of Astronautics, since 1999; he was elected

full member of the same Academy in 2006.

He coordinates the Research Doctorate in Mechatronics, since 1997.

He performed research activities, mainly in the field of Machine Design, par￾ticularly on static and dynamic structural analysis.

He studied the magnetic suspension of rotating parts, the vehicle dynamics, and

the related control systems; he was one of the promoters of the Interdepartmental

Laboratory on Mechatronics, where he performs research activities on magnetic

bearings, moving robots, and vehicle mechanics.

He is author of more than 270 scientific publications, covering many aspects of

mechanical design, published by Italian, English, and American magazines or

presented in Congresses.

xv

He wrote textbooks of Vehicle Mechanics (published in Italian and English),

adopted as reference in some Italian and American University. He also wrote

monographs on composite materials design, on the storage of energy on flywheels

(published in English and translated in Russian), on Rotating Systems Dynamics,

and of popular books on space exploration.

Lorenzo Morello got his degree on Mechanical Automotive Engineering in 1968,

at the Politecnico of Turin.

He started immediately after his career at the Politecnico as Assistant of Machine

Design and Technologies.

He left the Politecnico in 1971 and started a new activity at a branch of Fiat

dedicated to vehicles studies that will be joined to the new Research Center in 1976.

He participates in the development of some car and of experimental prototypes for

the ESV US Program. He also developed some mathematical model for vehicle

suspension and road holding simulation.

Starting from 1973 he was involved on an ample project for the development of

mathematical models of the vehicle, to address the product policies of the company

to face the first energy crisis; as part of this activity, he started the development of a

new automatic transmission for reduced fuel consumption and of a small direct

injection diesel engine to be used on automobiles.

He was appointed manager of the chassis department of the Vehicle Research

Unit and has been coordinating the development of many research prototypes, such

as electric cars, off-road vehicle, trucks, and buses.

He was appointed manager of the same Research Unit in 1977 and has been

leading a group of about 100 design engineers, dedicated to the development of

prototypes; a new urban bus with unitized thin steel sheet body, with spot welded

joints, a commercial vehicle that will start production later on, a small light weight

urban car, under contract of the National Research Council, and a hybrid car, under

contract of the US Department of Energy, were developed in this period of time.

He took the responsibility of the Engines Research Unit in 1980; this group, of

about 200 people, was mainly addressed to the development of new car engines. He

has been managing the development of many petrol engines, according to the

principle of high turbulence fast combustion, a car direct injection diesel engine,

many turbocharged prechamber diesel engines, a modular two-cylinder car engine,

and many other modified prototypes.

He was appointed Director of Products development in 1983; this position

includes all applied research activities on Vehicle Products of Fiat Group. The

Division included about 400 people, addressed to power train, chassis, and bodies

studies and also to prototype's construction.

He joined Fiat Auto in 1983 to take the responsibility of development of some

new car petrol engines and of the direct injection diesel (the first in the world for

automobile application). He was appointed Director for Power Train Engineering in

1987; the objective of this group was to develop all engines produced by the Fiat

Auto brands; the most important activity of this time is the development of the new

xvi About the Authors