Calculation of tyre lateral forces.

[D J Yates]

Myself and a team mate have just spent several hours trying to solve free body diagrams of the front wheels (front view) to find the lateral and normal reactions at the tyres for a given lateral acceleration.

We used an FBD of the sprung mass rolling about the neutral roll axis to find the reactions and moments at the roll centers, then applied the forces and moment at the front roll center in the front view FBD. Four simultanious equations can be found from the front view FBD. Finding normal tyre forces alone is simle (same as the method in all the vehicle dynamics books), however, lateral forces cannot be determined. We also tried to find the reactions in directions parrallel and perpendicular to the lines conecting RC and contact patches but with no joy, all the forces just cancel each other out.

Could anyone suggest where (and/or why) we may be going wrong?

[D J Yates]

Myself and a team mate have just spent several hours trying to solve free body diagrams of the front wheels (front view) to find the lateral and normal reactions at the tyres for a given lateral acceleration.

We used an FBD of the sprung mass rolling about the neutral roll axis to find the reactions and moments at the roll centers, then applied the forces and moment at the front roll center in the front view FBD. Four simultanious equations can be found from the front view FBD. Finding normal tyre forces alone is simle (same as the method in all the vehicle dynamics books), however, lateral forces cannot be determined. We also tried to find the reactions in directions parrallel and perpendicular to the lines conecting RC and contact patches but with no joy, all the forces just cancel each other out.

Could anyone suggest where (and/or why) we may be going wrong?