Torsional rigidity of non-circular bars in mechanisms and machines

A method to approximate the torsional rigidity of any cylindrical solid cross-section is presented on this paper. Cross sections are classified by similarity to an ellipse, rectangle and/or a triangle. An aspect ratio of length to width is used as the second criteria to enter a graph where the torsional rigidity of the cross-section is given as a ratio to that of a circle of equal area.