Advanced Vehicle Technology 2 Episode 1 pptx

1.2 The major individual components comprising the body shell will now be described separately under the following subheadings: 1 Window and door pillars 2 Windscreen and rear window rai

Advanced Vehicle Technology

To my long-suffering wife, who has provided port and understanding throughout the preparation

sup-of this book

Vehicle Technology

Second edition

Heinz Heisler MSc., BSc., F.I.M.I., M.S.O.E., M.I.R.T.E., M.C.I.T., M.I.L.T.

Formerly Principal Lecturer and Head of Transport Studies,

College of North West London, Willesden Centre, London, UK

OXFORD AMSTERDAM BOSTON LONDON NEW YORK PARIS

SAN DIEGO SAN FRANCISCO SINGAPORE SYDNEY TOKYO

An imprint of Elsevier Science

Linacre House, Jordan Hill, Oxford OX2 8DP

225 Wildwood Avenue, Woburn, MA 01801-2041

First published by Edward Arnold 1989

Reprinted by Reed Educational and Professional Publishing Ltd 2001 Second edition 2002

Copyright#1989, 2002 Heinz Heisler All rights reserved

The right of Heinz Heisler to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988

No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether

or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of

a license issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1T 4LP Applications for the copyright holder's written permission to reproduce any part of this publication should be addressed

to the publishers

Whilst the advice and information in this book are believed to be true and

accurate at the date of going to press, neither the authors nor the publisher can accept any legal responsibility or liability for any

errors or omissions that may be made.

Library of Congress Cataloguing in Publication Data

A catalogue record for this book is available from the Library of Congress ISBN 0 7506 5131 8

For information on all Butterworth-Heinemann publications

visit our website at www.bh.com

Typeset by Integra Software Services Pvt Ltd, Pondicherry, India

www.integra-india.com

Printed and bound in Great Britain

1 Vehicle structure

1.1 Integral body construction

1.2 Engine, transmission and body structures

1.3 Fifth wheel coupling assembly

1.4 Trailer and caravan drawbar couplings

1.5 Semi-trailer landing gear

1.6 Automatic chassis lubrication system

2 Friction clutch

2.1 Clutch fundamentals

2.2 Angular driven plate cushioning and torsional damping

2.3 Clutch friction materials

2.4 Clutch drive and driven member inspection

2.5 Clutch misalignment

2.6 Pull type diaphragm clutch

2.7 Multiplate diaphragm type clutch

2.8 Lipe rollway twin driven plate clutch

2.9 Spicer twin driven plate angle spring pull type clutch

2.10 Clutch (upshift) brake

2.11 Multiplate hydraulically operated automatic transmission clutches 2.12 Semicentrifugal clutch

2.15 Composite flywheel and integral single plate diaphragm clutch

3 Manual gearboxes and overdrives

3.1 The necessity for a gearbox

3.2 Five speed and reverse synchromesh gearboxes

3.3 Gear synchronization and engagement

3.4 Remote controlled gear selection and engagement m

3.5 Splitter and range change gearboxes

3.6 Transfer box power take-off

3.7 Overdrive considerations

3.8 Setting gear ratios

4 Hydrokinetic fluid couplings and torque converters

4.1 Hydrokinetic fluid couplings

4.2 Hydrokinetic fluid coupling efficiency and torque capacity

4.3 Fluid friction coupling

4.4 Hydrokinetic three element torque converter

4.5 Torque converter performance terminology

4.6 Overrun clutches

4.7 Three stage hydrokinetic converter

4.8 Polyphase hydrokinetic torque converter

4.9 Torque converter with lock-up and gear change friction clutches

5 Semi- and fully automatic transmission

5.1 Automatic transmission consideration

5.2 Four speed and reverse longitudinally mounted automatic transmission mechanical power flow

5.3 The fundamentals of a hydraulic control system

5.4 Basic principle of a hydraulically controlled gearshift

5.5 Basic four speed hydraulic control system

5.6 Three speed and reverse transaxle automatic transmission mechanical power flow

5.7 Hydraulic gear selection control components

5.8 Hydraulic gear selection control operation

5.9 The continuously variable belt and pulley transmission

5.10 Five speed automatic transmission with electronic-hydraulic control

5.11 Semi-automatic (manual gear change two pedal control) transmission system

6 Transmission bearings and constant velocity joints

6.1 Rolling contact bearings

6.2 The need for constant velocity joints

7 Final drive transmission

7.1 Crownwheel and pinion axle adjustments

7.2 Differential locks

7.3 Skid reducing differentials

7.4 Double reduction axles

7.5 Two speed axles

7.6 The third (central) differential

7.7 Four wheel drive arrangements

7.8 Electro-hydralic limited slip differential

7.9 Tyre grip when braking and accelerating with good and poor road surfaces

7.10 Traction control system

8 Tyres

8.1 Tractive and braking properties of tyres

8.2 Tyre materials

8.3 Tyre tread design

8.4 Cornering properties of tyres

8.5 Vehicle steady state directional stability

8.6 Tyre marking identification

8.7 Wheel balancing

9 Steering

9.1 Steering gearbox fundamental design

9.2 The need for power assisted steering

9.3 Steering linkage ball and socket joints

9.4 Steering geometry and wheel alignment

9.5 Variable-ratio rack and pinion

9.6 Speed sensitive rack and pinion power assisted steering

9.7 Rack and pinion electric power assisted steering

10 Suspension

10.1 Suspension geometry

10.2 Suspension roll centres

10.3 Body roll stability analysis

10.4 Anti-roll bars and roll stiffness

10.5 rubber spring bump or limiting stops

10.6 Axle location

10.7 Rear suspension arrangements

10.8 Suspension design consideration

10.9 Hydrogen suspension

10.10 Hydropneumatic automatic height correction suspension

10.11 Commercial vehicle axle beam location

10.12 Variable rate leaf suspension springs

10.13 Tandem and tri-axle bogies

10.14 Rubber spring suspension

10.15 Air suspensions for commercial vehicles

10.16 Lift axle tandem or tri-axle suspension

10.17 Active suspension

10.18 Electronic controlled pneumatic (air) suspension for on and off road use

11 Brake system

11.1 Braking fun

11.2 Brake shoe and pad fundamentals

11.3 Brake shoe expanders and adjusters

11.4 Disc brake pad support arrangements

11.5 Dual- or split-line braking systems

11.6 Apportional braking

11.7 Antilocking brake system (ABS)

11.8 Brake servos

11.9 Pneumatic operated disk brakes (for trucks and trailers)

12 Air operated power brake equipment and vehicle retarders

12.1 Introductions to air powered brakes

12.2 Air operated power brake systems

12.3 Air operated power brake equipment

12.4 Vehicle retarders

12.5 Electronic-pneumatic brakes

13 Vehicle refrigeration

13.1 Refrigeration terms

13.2 Principles of a vapour-compression cycle refrigeration system

13.3 Refrigeration system components

13.4 Vapour-compression cycle refrigeration system with reverse cycle defrosting

14.3 Aerodynamic lift

14.4 Car body drag reduction

14.5 Aerodynamic lift control

14.6 Afterbody drag

14.7 Commercial vehicle aeordynamic fundamentals

14.8 Commercial vehicle drag reducing devices

Index

1.1.1 Description and function of body

components (Fig 1.2)

The major individual components comprising the

body shell will now be described separately under

the following subheadings:

1 Window and door pillars

2 Windscreen and rear window rails

3 Cantrails

4 Roof structure

5 Upper quarter panel or window

6 Floor seat and boot pans

Window and door pillars (Fig 1.2(3, 5, 6, and 8))

Windowscreen and door pillars are identified by a

letter coding; the front windscreen to door pillars

are referred to as A post, the centre side door pillars

as BC post and the rear door to quarter panel as

D post These are illustrated in Fig 1.2

These pillars form the part of the body structure

which supports the roof The short form A pillar and

rear D pillar enclose the windscreen and quarter

windows and provide the glazing side channels,

whilst the centre BCpillar extends the full height of

the passenger compartment from roof to floor and

supports the rear side door hinges The front and

rear pillars act as struts (compressive members)

which transfer a proportion of the bending effect,

due to underbody sag of the wheelbase, to each end

of the cantrails which thereby become reactive

struts, opposing horizontal bending of the

pas-senger compartment at floor level The central BC

pillar however acts as ties (tensile members),

trans-ferring some degree of support from the mid-span of

the cantrails to the floor structure

Windscreen and rear window rails (Fig 1.2(2))

These box-section rails span the front window

pillars and rear pillars or quarter panels depending

upon design, so that they contribute to the

resist-ance opposing transverse sag between the wheel

track by acting as compressive members The

other function is to support the front and rear

ends of the roof panel The undersides of the rails

also include the glazing channels

Cantrails (Fig 1.2(4)) Cantrails are the tal members which interconnect the top ends of thevertical A and BCor BCand D door pillars (posts).These rails form the side members which make upthe rectangular roof framework and as such aresubjected to compressive loads Therefore, theyare formed in various box-sections which offer thegreatest compressive resistance with the minimum

horizon-of weight and blend in with the rohorizon-ofing A drip rail(Fig 1.2(4)) is positioned in between the overlap-ping roof panel and the cantrails, the joins beingsecured by spot welds

Roof structure (Fig 1.2) The roof is constructedbasically from four channel sections which formthe outer rim of the slightly dished roof panel.The rectangular outer roof frame acts as the com-pressive load bearing members Torsional rigidity

to resist twist is maximized by welding the fourcorners of the channel-sections together The slightcurvature of the roof panel stiffens it, thus prevent-ing winkling and the collapse of the unsupportedcentre region of the roof panel With large cars,additional cross-rail members may be used toprovide more roof support and to prevent the roofcrushing in should the car roll over

Upper quarter panel or window (Fig 1.2(6)) This

is the vertical side panel or window which occupiesthe space between the rear side door and the rearwindow Originally the quarter panel formed animportant part of the roof support, but improvedpillar design and the desire to maximize visibilityhas either replaced them with quarter windows orreduced their width, and in some car models theyhave been completely eliminated

Floor seat and boot pans (Fig 1.3) These tute the pressed rolled steel sheeting shape toenclose the bottom of both the passenger and lug-gage compartments The horizontal spread-outpressing between the bulkhead and the heel board

consti-is called the floor pan, whilst the raconsti-ised platformover the rear suspension and wheel arches is known

as the seat or arch pan This in turn joins onto alower steel pressing which supports luggage and isreferred to as the boot pan

To increase the local stiffness of these platformpanels or pans and their resistance to transmittedvibrations such as drumming and droning, manynarrow channels are swaged (pressed) into the steelsheet, because a sectional end-view would show a2

semi-corrugated profile (or ribs) These channels

provide rows of shallow walls which are both bent

and stretched perpendicular to the original flat

sheet In turn they are spaced and held together

by the semicircular drawn out channel bottoms.Provided these swages are designed to lay thecorrect way and are not too long, and the metal isnot excessively stretched, they will raise the rigidity

Fig 1.2 Load bearing body box-section members

3

Fig 1.3 (a±c) Platform chassis

4

of these panels so that they are equivalent to a sheet

which may be several times thicker

Central tunnel (Fig 1.3(a and b)) This is the

curved or rectangular hump positioned

longitudin-ally along the middle of the floor pan Originlongitudin-ally it

was a necessary evil to provide transmission space

for the gearbox and propeller shaft for rear wheel

drive, front-mounted engine cars, but since the

chassis has been replaced by the integral

box-section shell, it has been retained with front wheel

drive, front-mounted engines as it contributes

considerably to the bending rigidity of the floor

structure Its secondary function is now to house

the exhaust pipe system and the hand brake cable

assembly

Sills (Figs 1.2(9) and 1.3(a, b and c)) These members

form the lower horizontal sides of the car body

which spans between the front and rear road-wheel

wings or arches To prevent body sag between the

wheelbase of the car and lateral bending of the

structure, the outer edges of the floor pan are given

support by the side sills These sills are made in the

form of either single or double box-sections

(Fig 1.2(9)) To resist the heavier vertical bending

loads they are of relatively deep section

Open-top cars, such as convertibles, which do not

receive structural support from the roof members,

usually have extra deep sills to compensate for the

increased burden imposed on the underframe

Bulkhead (Figs 1.2(1) and 1.3(a and b)) This is the

upright partition separating the passenger and

engine compartments Its upper half may form

part of the dash panel which was originally used to

display the driver's instruments Some body

manu-facturers refer to the whole partition between engine

and passenger compartments as the dash panel If

there is a double partition, the panel next to the

engine is generally known as the bulkhead and that

on the passenger side the dash board or panel The

scuttle and valance on each side are usually joined

onto the box-section of the bulkhead This braces

the vertical structure to withstand torsional

distor-tion and to provide platform bending resistance

support Sometimes a bulkhead is constructed

between the rear wheel arches or towers to reinforce

the seat pan over the rear axle (Fig 1.3(c))

Scuttle (Fig 1.3(a and b)) This can be considered

as the panel formed under the front wings which

spans between the rear end of the valance, where itmeets the bulkhead, and the door pillar and wing.The lower edge of the scuttle will merge with thefloor pan so that in some cases it may form part ofthe toe board on the passenger compartment side.Usually these panels form inclined sides to the bulk-head, and with the horizontal ledge which spans thefull width of the bulkhead, brace the bulkhead wall

so that it offers increased rigidity to the structure.The combined bulkhead dash panel and scuttle willthereby have both upright and torsional rigidity

Front longitudinals (Figs 1.2(10) and 1.3(a and b))These members are usually upswept box-sectionmembers, extending parallel and forward from thebulkhead at floor level Their purpose is to with-stand the engine mount reaction and to support thefront suspension or subframe A common feature

of these members is their ability to support verticalloads in conjunction with the valances However, inthe event of a head-on collision, they are designed

to collapse and crumble within the engine ment so that the passenger shell is safeguarded and

compart-is not pushed rearwards by any great extent

Front valance (Figs 1.2 and 1.3(a and b)) Thesepanels project upwards from the front longitudinalmembers and at the rear join onto the wall of thebulkhead The purpose of these panels is to transferthe upward reaction of the longitudinal memberswhich support the front suspension to the bulkhead.Simultaneously, the longitudinals are preventedfrom bending sideways because the valance panelsare shaped to slope up and outwards towards thetop The panelling is usually bent over near theedges to form a horizontal flanged upper, thuspresenting considerable lateral resistance Further-more, the valances are sometimes stepped andwrapped around towards the rear where they meetand are joined to the bulkhead so that additionallengthwise and transverse stiffness is obtained

If coil spring suspension is incorporated, thevalance forms part of a semi-circular tower whichhouses and provides the load reaction of the spring

so that the merging of these shapes compounds therigidity for both horizontal lengthwise and lateralbending of the forward engine and transmissioncompartment body structure Where necessary,double layers of sheet are used in parts of the springhousing and at the rear of the valance where theyare attached to the bulkhead to relieve some of theconcentrated loads

5

Rear valance (Fig 1.2(7)) This is generally

con-sidered as part of the box-section, forming the front

half of the rear wheel arch frame and the panel

immediately behind which merges with the heel

board and seatpan panels These side inner-side

panels position the edges of the seat pan to its

designed side profile and thus stiffen the underfloor

structure above the rear axle and suspension When

rear independent coil spring suspension is adopted,

the valance or wheel arch extends upwards to form

a spring tower housing and, because it forms a

semi-vertical structure, greatly contributes to the

stiffness of the underbody shell between the floor

and boot pans

Toe board The toe board is considered to form

the lower regions of the scuttle and dash panel near

where they merge with the floor pan It is this

panelling on the passenger compartment side

where occupants can place their feet when the car

is rapidly retarded

Heel board (Fig 1.3(b and c)) The heel board is

the upright, but normally shallow, panel spanning

beneath and across the front of the rear seats Its

purpose is to provide leg height for the passengers

and to form a raised step for the seat pan so that

the rear axle has sufficient relative movement

clearance

1.1.2 Platform chassis (Fig 1.3(a±c))

Most modern car bodies are designed to obtain

their rigidity mainly from the platform chassis and

to rely less on the upper framework of window

and door pillars, quarter panels, windscreen rails

and contrails which are becoming progressively

slenderasthe desirefor better visibility isencouraged

The majority of the lengthwise (wheelbase)

bend-ing stiffness to resist saggbend-ing is derived from both

the central tunnel and the side sill box-sections

(Fig 1.3(a and b)) If further strengthening is

necessary, longitudinal box-section members may

be positioned parallel to, but slightly inwards from,

the sills (Fig 1.3(c)) These lengthwise members

may span only part of the wheelbase, or the full

length, which is greatly influenced by the design of

road wheel suspension chosen for the car, the depth

of both central tunnel and side sills, which are built

into the platform, and if there are subframes

attached fore and aft of the wheelbase (Fig 1.6

(a and b))

Torsional rigidity of the platform is usuallyderived at the front by the bulkhead, dash panand scuttle (Fig 1.3(a and b)) at the rear by theheel board, seat pan, wheel arches (Fig 1.3(a, b andc)), and if independent rear suspension is adopted,

by the coil spring towers (Fig 1.3(a and c)).Between the wheelbase, the floor pan is normallyprovided with box-section cross-members to stiffenand prevent the platform sagging where thepassenger seats are positioned

1.1.3 Stiffening of platform chassis(Figs 1.4 and 1.5)

To appreciate the stresses imposed on and theresisting stiffness offered by sheet steel when it issubjected to bending, a small segment of a beamgreatly magnified will now be considered (Fig.1.4(a)) As the beam deforms, the top fibres con-tract and the bottom fibres elongate The neutralplane or axis of the beam is defined as the planewhose length remains unchanged during deforma-tion and is normally situated in the centre of auniform section (Fig 1.4(a and b))

The stress distribution from top to bottom withinthe beam varies from zero along the neutral axis(NA), where there is no change in the length of thefibres, to a maximum compressive stress on the outertop layer and a maximum tensile stress on the outerbottom layer, the distortion of the fibres beinggreatest at their extremes as shown in Fig 1.4(b)

It has been found that bending resistanceincreases roughly with the cube of its distancefrom the neutral axis (Fig 1.5(a)) Therefore, bend-ing resistance of a given section can be greatlyimproved for a given weight of metal by takingmetal away from the neutral axis where the metalfibres do not contribute very much to resistingdistortion and placing it as far out as possiblewhere the distortion is greatest Bending resistancemay be improved by using longitudinal or cross-member deep box-sections (Fig 1.5(b)) and tunnelsections (Fig 1.5(c)) to restrain the platform chas-sis from buckling and to stiffen the flat horizontalfloor seat and boot pans So that vibration anddrumming may be reduced, many swaged ribs arepressed into these sheets (Fig 1.5(d))

1.1.4 Body subframes (Fig 1.6)Front or rear subframes may be provided to bracethe longitudinal side members so that independentsuspension on each side of the car receives adequatesupport for the lower transverse swing arms (wish-bone members) Subframes restrain the two halves

of the suspension from splaying outwards or the6

longitudinal side members from lozenging as

alter-native road wheels experience impacts when

travel-ling over the irregularities of a normal road surface

It is usual to make the top side of the subframe

the cradle for the engine or engine and transmission

mounting points so that the main body structure

itself does not have to be reinforced This

particu-larly applies where the engine, gearbox and final

drive form an integral unit because any torque

reaction at the mounting points will be transferred

to the subframe and will multiply in proportion to

the overall gear reduction This may be

approxi-mately four times as great as that for the front

mounted engine with rear wheel drive and will

become prominent in the lower gears

One advantage claimed by using separate

sub-frames attached to the body underframe through

the media of rubber mounts is that transmittedvibrations and noise originating from the tyresand road are isolated from the main body shelland therefore do not damage the body structureand are not relayed to the occupants sittinginside

Cars which have longitudinally positionedengines mounted in the front driven by the rearwheels commonly adopt beam cross-membersubframes at the front to stiffen and support thehinged transverse suspension arms (Fig 1.6(a)).Saloon cars employing independent rear suspen-sion sometimes prefer to use a similar subframe atthe rear which provides the pivot points for thesemi-trailing arms because this type of suspensionrequires greater support than most other arrange-ments (Fig 1.6(a))

Fig 1.4 Stress and strain imposed on beam when subjected to bending

7

When the engine, gearbox and final drive are

combined into a single unit, as with the front

longi-tudinally positioned engine driving the front wheels

where there is a large weight concentration, a

sub-frame gives extra support to the body longitudinal

side members by utilising a horseshoe shaped frame(Fig 1.6(b)) This layout provides a platform forthe entire mounting points for both the swing armand anti-roll bar which between them make up thelower part of the suspension

Fig 1.5 Bending resistance for various sheet sections

8

Fig 1.6 (a±c) Body subframe and underfloor structure

9