Steering Arm Length
 
Description
The steering arm length is the shortest distance between the King Pin (steer) Axis and the connection of the tie rod to the suspension upright.
Units
Length
Request Names
• steering_arm.length_left
• steering_arm.length_right
Inputs
• King Pin (steer) axis location (KPP) left and right
• King Pin (steer) axis unit vector (kpv) left and right
• Tie rod to suspension upright location (TR0) left and right
Method
The vector R from the connection of the tie rod to the suspension upright location (TRO) to the King Pin (steer) axis location (KPP) is difference between the two locations:
R = KPP - TRO
This vector R may be decomposed into two vectors: One vector parallel to the King Pin Axis and one vector perpendicular to the King Pin Axis. The length of the vector perpendicular to the King Pin (Steer) Axis is the steering arm length. The portion of R parallel to the steer axis SP is given by the dot product of R with the King Pin Axis unit vector (kpv):
SP = (R o kpv) kpv
The portion of R perpendicular to the steer axis, the steering arm vector (SA), then is:
SA = R - (R o kpv) kpv
Note the steering arm vector (SA) is used as an input to calculate the steering arm tie rod toggle angle. The magnitude of the steering arm vector is the steering arm length.
steering_arm.length = | SA |
Request Statements
Steering Arm Length (and Toggle Angle):
REQUST/id, FUNCTION=USER(900,49,characteristics_input_array_id,   , left_tie_rod_outer_id,   , left_tie_rod_inner_id,   , right_tie_rod_outer_id,   , right_tie_rod_inner_id)/
Nomeclature
• Bold text in uppercase letters, such as R, shows vectors.
• Bold text in lowercase letters, such as u_lon, shows unit vectors.
• X is the vector cross product operator.
• o is the vector dot product operator.
• * is the scalar multiplication operator.
• | R | is the length (norm) of the vector R.
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