Pipe command - unwanted twisting

Hi All,

I am trying to achieve the pipe being narrower in the middle, and wider near the corners. When I use Pipe command with variable radius, I get twists and distortions. When I create a single diameter pipe and then explode and manipulated via control points, the edges/corners come apart, and I need a closed polysolid.

I have done this before with rounded curves, so is it the square corners that are causing disorientation?

The pics below show both methods


Any help much appreciated.


Hello - my guess is the problem is that there’s no way to add a radius location and the obvious angle on the corners. I think a sweep1 or just lofts with ellipses on the corners and a circle in the middle is the way to go:


Blue = Sweep1, White = 3x Loft, then Join.