See attachment, please. Six variables that can change individually and hence altering all connected. The goal is always to find the distance between A & C, "ACD" if you will. ACD = ... Given 6 flexible variables: (Abbreviated to perhaps make things easier: r, abd, wt, abl, pll, pld. Use or not, up to you.) > r = radius of 1/2-circle > wt = wall thickness of 1/2-circle > abd = distance between A & B > abl = angle of blue line > pll = length of the 2 purple lines > pld = distance between the two purple lines Constants: * The purple line inside the 1/2-circle is in contact with the inner wall. (Blue line angle changes and along with it changes the position of purple lines, and inner purple line always meeting with inner wall, as shown.) * The blue line always through center of the two purple lines, and the two lines always perpendicular to the blue line. * Distance between the two purple lines, whatever it may be, will always be divided by 2, for finding point C. * Point B always along 'A' line, zero degrees. * 'abl' always through point B. My simple notes so far, maybe helpful...: * Position of inner purple line dictated by abl, wt, pll. * Radius of 1/2-circle minus wall thickness, r - wt = .... That new radius, along the inside wall, where the inner purple line is in contact with. * Calculating for sin of theta, maybe involved, I can do that, but that's about it for my resourcefulness, individually...; I have more notes, but they seem to cause more stress than clarity. Seems to be very advanced mathemetics, multi-dimentional sorta geometric thinking, I can't even figure out where to start. It's improtant, though.... I hope you can help. Ask questions. I'll revise up here if I should have included more points.... Thank you.