I have built tubes by Bezier Curve, converting to mesh, and adding solidify modifier. I want concentric tubes now. I could not directly scale the duplicated tube, which will cause it to be not concentric (as shown on the left in the Figure 1).
I have been able to duplicate the Bezier Curve and go through the process and add thicker layer (on the right of Figure 1) to make concentric tubes. But there seems to be a little gaps between the outer tube and the inner one. However, this process will not work for dynamic tubes, especially when they change locations.
Figure 2, I tried using curve modifier, but only can move or rotate it or a little shrinkage. I think I need subdivisions on the cylinders, right?
Figure 3(left), Later, I tried more subdivisions, which works good for one cylinder, but not for concentric cylinders joined together. Even I also set subdivisions for the inner cylinder. Figure 3(right) using array modifier to elongate the cylinders and join them, add curve modifier, and separate them by loose parts. Make sure the origins of the cylinders and the curves at the same spot.