I posted this on math stack exchange but realize it is more a physics question.
I have a structure which is set up as shown in the image. A weight hangs from point A with mass $m$. Joint B is free to rotate. Joint C connects the two parts ABC and CD. It is intended to be a fixed joint so that the two parts do not move relative to each other. The end D is free to slide along the ground plane.
The problem is to calculate the torque that is trying to rotate the two parts at joint C. I need to know if the joint will be strong enough or if it will fail when too much mass $m$ is applied. In actual fact the joint C is actually a motor and I need to know if its stall torque is enough to ensure it can hold the structure stable given a designated mass $m$.
Missing from the diagram is the angle $\theta$ which is the angle between the vertical and line AB. I know that the mass produces a torque around B of $dmg \sin \theta$. I can't quite work out the torque which is trying to open up the angle BCD.