dear all, i have just received a question about torsion. 1. The problem statement, all variables and given/known data *************** a graph has been attached as attachment at bottom************* The objective is to find the torsion shear stress at the cross section of the "dark Grey tube". Let's have a look: 1.There is a reaction torque acting on the motor M, 2.The force is then transfered to dark grey tube by a light grey carrier. 3. blue cross is the center of the motor 4. purple cross is the centroid of the dark grey tube 5. i have J / Ixx,Iyy of that tube 6. Only the dark grey tube is fixed at 2 ends. 7. carrier is mush shorter than the tube 2. Relevant equations I think I am finding the suitable eqts. So I miss this section. Or You think T/J= shear/R ?? 3. The attempt at a solution So, #1 i would like to ask whether the following steps are correct and #2 What is the torsion equations for irregular hollow section. #3 how to find the R, outer radius of the shaft, for the case that equation T/J= shear/R is used. My Methodology: 1. Shear force is acting at the 2 hand sides of the tube as resultant. 2. the Shear force acts like a torque on the hollow section 3. use parallel axis theorem to transform "moment of inertia" from the original centroid to the torque center 4. use a torsion equation that contain J to fix it (<------------#2 that's what i would like to find now) Thank you very much for your help.