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THE COMMERCIAL VEHICLE

AN INTRODUCTION

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VEHICLE GEOMETRY

FRONT SUSPENSION

REAR SUSPENSION

REAR AXLE

FR

AM

EFRONTAXLE

STEERING B

OX

HA

NG

ER

S

TOTAL VEHICLE ALIGNMENT

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DO NOT FORGET THE BIG PICTURE

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STEERING GEOMETRY

WHEN : ACCELERATING & DECELERATING

STRAIGHT AHEAD & CORNERING

LOADED & UNLOADED

LOW SPEED OR HIGH

GOOD ROAD OR BAD

NEED : EASE OF HANDLING

SAFETY

TYRE LIFE

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STEERING GEOMETRY

ACKERMAN ANGLE

INCLUDED ANGLE

KING PIN ANGLE

CAMBER ANGLE

CASTOR ANGLE

TOE IN & TOE OUT

NOTE: MAINTENANCE OF THE FRONT AXLE IS BASICALLY TO PRESERVE THESE ANGLES

A DEVIATION WILL LEAD TO A LARGE DEFLECTION

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ACKERMANN PRINCIPLE

THE DOUBLE PIVOT STEERING

THE SINGLE PIVOT STEERING

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THE DOUBLE PIVOT STEERING ACKERMANN PRINCIPLE

CUT

PARALLELOGRAM

STRAIGHT AHEAD

RECTANGLE

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ACKERMANN PRINCIPLE

INSTANTANIOUS CENTRES

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ACKERMANN PRINCIPLE

NEED : TO ACHIEVE TOE OUT ON TURNS IN ORDER TO ENSURE PURE ROLLING OF TYRES AROUND CORNERS

THE TRAPEZIUM EFFECT

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ACKERMANN PRINCIPLE

x x x x x

THE PRINCIPLE : EQUAL DISPLACEMENTS ON THE X AXISSUBTEND UNEQUAL ANGLES ON THE CIRCUMFERENCE

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ACKERMANN PRINCIPLETHE TRAPEZIUM EFFECT

A > B

NOTE: FOR THE SAME DISPLACEMENT THE ANGLE CUT BY THE INNER TYRE IS MORE

X X

A B

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ACKERMANN PRINCIPLE

CORNERING

THE PRINCIPLE: IN A FOUR BAR CHAIN , FORMING A TRAPEZIUM ,

IF THE TWO NON PARALLEL SIDES ARE EXTENDED , THEY MEET AT A POINT.

THE LOCUS OF THIS POINT IS A STRAIGHT LINE - ON THE REAR AXLE

STRAIGHT AHEAD

ACKERMANANGLE

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ACKERMANN PRINCIPLE

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KING PIN LINE

TYRE LINE

INCLUDED ANGLE

CENTREPOINT STEERING

INCLUDED ANGLE

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INCLUDED ANGLE

INCLUDED ANGLE

KING PIN OFFSET

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NEED : CENTRE POINT STEERING AND STEERING SELF CENTRING

KING PIN ANGLE AXLE BEAM

KING PIN BORENORMAL

KING PIN ANGLE

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NEED : CAMBER ANGLE - A COMPONENT OF INCLUDED ANGLE FOR CENTRE POINT STEERING

- COMPENSATES THE DEFLECTIONS DUE TO BENDING

CAMBER ANGLE

NORMAL

CAMBER ANGLE

KINGPIN ANGLE

TYRE LINE

KING PIN LINE

INCLUDED ANGLE

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TOE IN

NEED: CONSEQUENT TO THE CAMBER ANGLE THE TYRE BEHAVES LIKE A CONE AND TENDS TO TO ROLL OUTWARDS.

TOE IN IS GIVEN TO COUNTER THIS FORCE.

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CASTOR

KINGPIN LINE

CASTOR ANGLE

TRAILING DISTANCE

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CASTOR

KINGPIN LINE

NORMAL

CASTOR IS DERIVED BY THE SLOPE OF THE SPRING

NEED : DIRECTIONAL STABILITY

CASTOR ANGLE

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CASTOR

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RIM OFFSET/DEPORT

RIM OFFSET

Rim deport

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RIM OFFSET

LESS RIM DEPORT ON FRONT WHEEL

WIDER TRACK WIDTH

LESS RIM OFFSET ON REAR WHEELS

DUALS KISSING