I'm having trouble with this structure, but I think I finally figured it out. I'm hoping to get a confirmation or a push in the right direction if I'm wrong. I'm trying to solve the truss in terms of the weight at the end.
The Attempt at a Solution
I sectioned the upper left portion cutting through the pivot members and 3 sections of cable (in blue) to try and solve for tension T in terms of W using the moment about the pivot point where the trusses are joined, but my solution went bad when I tried to apply that to the full structure in order to determine reactions at the supports.
I think what happened was that I don't know how to apply the tension force to the full FBD. I applied the tension only to the point of contact with the ground, which resulted in the roller having a downward force (impossible). I now suspect that I need to apply the tension at every point and basically treat it like a bunch of external forces to the full truss (resulting in 4 total applications of T). Am I correct?
I was also wondering if the tension force can be applied at the joints since a FBD of the pulleys gives a resultant at the joint equal to T in whatever directions the the cable runs. Or do I have to aplpy the forces at the radius of the pulleys?