Steering Geometry 1

Ans:

1. Geometric Parameters calculations:

2. given : Pneumatic trail of 25mm & Lateral force of 2000N

Ans : The Restoring moment for a 2000N lateral load and 25mm pneumatic trail would be:

Restoring moment = lateral load * (pneumatic trail+Mechanical trail).

= 2000 * (25+9.41)

= 68822 N/mm

3. Hardpoint recommendation to change the sign of the scrub radius :

Ans : Scrub radius would be zero when the steering axis meets the ground at the tire contact as seen from the front view in the yz-plane.

In yz-plane, coordinate of tire contact = (-800,0)

We have, coordinate of upper ball joint = (-675,525)

Equation of steering axis if it were to pass through the above two points is:

z - z1 = [(z2-z1)/(y2-y1)](y-y1)

z - 0 = [(525-0)/(-675+800)](y+800)

Simplifying, z = 4.2y + 3360 ....... (3)

For current z-coordinate of the lower ball joint i.e. z = 100, from equation (3), we get y = -776.19

Thus, changing the y-coordinate of the given lower ball joint to -776.19mm would give us a ZERO scrub radius.

Further decrease in the y-coordinate (i.e. more negative value) makes the scrub radius negative (outboard).

So, Suggested LCA Knuckle Ball Joint coordinate = (0, -780,100) to change the sign of the scrub radius.