About this model: This is a model of a torus contact with a flat surface. The contact forces include friction. The calculation of contact forces and moments is done within a Modelica custom component (Project>Definitions>Components). Model assumes the ground is the z = 0 plane, and the local x-axis is the axis of the torus. To create an stl file of a torus with radii (R and r) other the one used in the model, use the attached Maple worksheet (Project>Attachments>Documents).