Also re: Pipe not generating results - another step of what Pipe does is to generate an outer pipe surface and then an inner pipe surface and then do a boolean between the 2. When the pipes are not well formed because they're not mitered well that boolean step is probably ending up generating no output for many of those cases.

If you instead use Sweep you should get results on each profile, but you'll see that many of them are not getting miter trims on them (due to difficulty calculating miter intersections between 2 curved segments as described previously above).

If instead of Pipe you draw a circle and use Sweep, you'll get a result on every path but there will be a lot of extended pieces on failed miter cut areas.

To use Sweep instead of pipe just draw a circle of your desired radius somewhere off to the side (specifically it should be outside of the bounding box around the paths), like this:



Select it and then run Construct > Sweep, then at the "Select rails" prompt select all those path curves, that will generate a result like this:




But the problem here is that there will not be clean intersections between the extended portions of each path segment - that's just what happens on sweeps along non-planar path curves. I think that probably building the tubes all on a flat piece instead and then using Flow would probably be your best bet.

- Michael