Design & Modelling of Front Suspension Geometry

This challenge tests your understanding of front and side view kingpin geometry.

Also draw a rough sketch using the hardpoints to visualize the suspension

Assume the ground to be at zero elevation (vertical coordinate ) and the tire radius to be 300mm.

Coordinate system

X-pointing towards the back of the vehicle.

Y-pointing towards the right.

Z-pointing towards the top.

1, Calculate the following geometric parameters.

• Caster.

• Mechanical trail.

• Kingpin inclination Angle.

• Kingpin longitudinal offset.

• Scrub radius

• Kingpin lateral offset or spindle length

2, If the pneumatic trail is 25 mm and lateral force is 2000N, Calculate the restoring moment acting at the point where kingpin intersects the ground in side view.

3, Suggest a hardpoint recommendation to change sign of scrub radius that you calculated.

4, Finally Design the Front suspension geometry.

Methodology with Solutions:

1.

• Caster = 5.38 deg
• Mechanical Trail = 9.412mm
• KPI Angle = 10.01 deg
• Kingpin longitudinal Offset = 18.82 mm
• Scrub Radius = 32.353 mm
• Kingpin Lateral offset or Spindle Offset = 85.294 mm

2. Pneumatic Trail = 25 mm ; Lateral Force = 2000N

Restoring Force = 2000 * 25 = 50000 N-mm

3. New Points : for -ve scrub radius.

LCA_Knuckle_Ball_Joint X=0; Y= -812.75 ; Z = 100

UCA_Knuckle_Ball_Joint X=40; Y= -739.71 ; Z= 525

4.Front Suspension Geometry:

Roll Center came out to be at 506.81 mm