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1
THE COMMERCIAL VEHICLE
AN INTRODUCTION
2
VEHICLE GEOMETRY
FRONT SUSPENSION
REAR SUSPENSION
REAR AXLE
FR
AM
EFRONTAXLE
STEERING B
OX
HA
NG
ER
S
TOTAL VEHICLE ALIGNMENT
3
DO NOT FORGET THE BIG PICTURE
4
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
5
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
6
ACKERMANN PRINCIPLE
THE DOUBLE PIVOT STEERING
THE SINGLE PIVOT STEERING
7
THE DOUBLE PIVOT STEERING ACKERMANN PRINCIPLE
CUT
PARALLELOGRAM
STRAIGHT AHEAD
RECTANGLE
8
ACKERMANN PRINCIPLE
INSTANTANIOUS CENTRES
9
ACKERMANN PRINCIPLE
NEED : TO ACHIEVE TOE OUT ON TURNS IN ORDER TO ENSURE PURE ROLLING OF TYRES AROUND CORNERS
THE TRAPEZIUM EFFECT
10
ACKERMANN PRINCIPLE
x x x x x
THE PRINCIPLE : EQUAL DISPLACEMENTS ON THE X AXISSUBTEND UNEQUAL ANGLES ON THE CIRCUMFERENCE
11
ACKERMANN PRINCIPLETHE TRAPEZIUM EFFECT
A > B
NOTE: FOR THE SAME DISPLACEMENT THE ANGLE CUT BY THE INNER TYRE IS MORE
X X
A B
12
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
13
ACKERMANN PRINCIPLE
14
KING PIN LINE
TYRE LINE
INCLUDED ANGLE
CENTREPOINT STEERING
INCLUDED ANGLE
15
INCLUDED ANGLE
INCLUDED ANGLE
KING PIN OFFSET
16
NEED : CENTRE POINT STEERING AND STEERING SELF CENTRING
KING PIN ANGLE AXLE BEAM
KING PIN BORENORMAL
KING PIN ANGLE
17
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
18
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.
19
20
CASTOR
KINGPIN LINE
CASTOR ANGLE
TRAILING DISTANCE
21
CASTOR
KINGPIN LINE
NORMAL
CASTOR IS DERIVED BY THE SLOPE OF THE SPRING
NEED : DIRECTIONAL STABILITY
CASTOR ANGLE
22
CASTOR
23
RIM OFFSET/DEPORT
RIM OFFSET
Rim deport
24
RIM OFFSET
LESS RIM DEPORT ON FRONT WHEEL
WIDER TRACK WIDTH
LESS RIM OFFSET ON REAR WHEELS
DUALS KISSING