I am currently doing a project, where I have to design a screw actuated gripper with all the calculations based on the attached drawing, I have assumed that b=c=100mm and 45 degree angle. I have done calculations concerning reaction forces, support rods reactions, main screw (which length I can pick myself) and 70mm should be fine here. I calculated that the thread is Tr 8x1.5 using S235 material.
Now for the design part. I had an idea to fix the two rods using a beam. Beam would be T shaped and it would keep the two rods fixed. I would have some kind of holder as well to hold the beam still on the left side. I would put a nut through the first bar and the motor would control the screw. I don't know if it will be possible to design it that way. Another way with the beam was to make a whole through the beam, and add a plate which will push the first bar forward (screw would be used to move the plate.
Maybe I can just use a steel bar that will fix upper and lower part and a screw that will be longer and will go through the first bar and the fixing bar as well.
I hope that you understand my ideas, it is pretty hard to explain it since I am not quite sure how it will work yet.