This is the third test version of an unbreakable tube. The tube is highly resistant to axial pressure. Accidental radial forces will angle tube's element, but will not break the tube. The string inside the tube will build up a tension similar to "prestressed concrete". Angled tube elements will flip back to their origin, if you use an elastic string. Use a strong string/wire to make the tube manual unbreakable. Some results so far: Things to do: Update to V3 (improved elements, OpenSCAD optimization)Print at least one of each part and several of the tube elements. Then assemble it with a strong string. Make a knot at the open end. Rotate the upper part of the assembled tube clock wise, to increase the tension. The two strings inside the tube will twist by this rotation. Build up enough tension. Then try to bend the tube.