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Modelling and analysis of suspension systems 227
{F I 61 } 1
Body 4
I
{F J 51 } 1
H
{F B 31 } 1
{F H54 } 1
{F H45 } 1
Y
X 1
1
C
{F C 37 } 1
J
Body 5
{F C 73 } 1
Z 1
{F E 21 } 1 F
{F A 31 } 1 B
A
C
Body 2 G
{F G42 } 1
G
Body 3 D {F D34 } 1
{F D43 } 1
H
{F F 21 } 1
D
E
{F G24 } 1
P
O 1
{F P 41 } 1
Fig. 4.73
Free-body diagram for double wishbone suspension system static force analysis
In this model we are treating the connections and mounts as pin-jointed, or
as the equivalent spherical joints in an MBS model. For the track rod, Body
5, both ends of the linkage are pin-jointed and the force by definition must,
if we allow ourselves the assumption to ignore gravity for this study, act
along the axis H–J. In a similar manner the force acting on Body 7 at the
base of the strut at point C must be equal and opposite to the force acting at
the top on Body 6 at point I:
{F J51 } 1 {F H54 } 1 (4.257)
{F C37 } 1 {F C73 } 1 {F I61 } 1 (4.258)
The number of unknowns can be reduced even further, by using scale factors
to exploit the knowledge that the lines of action of the forces are known:
{F H54 } 1 f S1 {R JH } 1 (4.259)
{F C37 } 1 f S2 {R CI } 1 (4.260)