Better Approach for an Odd Surface?

[miano]

I am trying to create this oddly-shape surface. Iit is a chain path that guides a chain around a curve and down the pipe. The red curves are from plans. I added an extension to the red curves at the top. The final surface would need to be trimmed at the horizontal red curve.

The red curves at the top and bottom are fixed because they need to match up to other components.

The blue curves I added to sketch out the surface using a networksrf.

Although the topology of the curves is the generally the same as the desired surface, one has to keep adding curves to the network to eliminate the kinks.

Is there a better approach for making such a surface?

Chain Path.3dm (1.6 MB)

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[Lagom]

Very hard to understand what the final result should look like. Maybe you can sculpt the surface from a cylinder?

[miano]

The image above is close to the desired final product. The outlines are correct. The lack of smoothness is wildly incorrect. In the image, the edge in the back is higher than the edge at the front to guide a chain around a curve.

[skysurfer]

Not on computer now but it should be simple:

Draw the path curve of the chain
Make a pipe with the needed radius over the curve
Draw a big flat plane at the desidered height, where the thing should open
Cut the pipe with the plane.

Smooth as silk ( if the path curve is smooth)

[AlW]

Although I have no specific suggestions, I note that Miano’s picture seems to require that the chain be supported over 180 degrees instead of 90.

Edit: Actually, I suppose Skysysurfer’s suggestion would still work except the trim plane would need to be a suitably curved surface like an exploded extruded arc or more customized surface.

[miano]

For more information, the only circular curve is where it connects to the pipe at the end.

The chain path is not circular in order to hold the chain in the path.

[jeremy5 (Jeremy)]

This is a tricky surface to make, not least because the red curve is pretty bumpy. I had two false starts before finding a way that worked for me. Result isn’t bad - would be better if I expended more time on it.

Rather than try to create a network surface I would simply loft the chute sections. I added some surface guides at each end to control the end directions, and I rebuilt all the curves, after experiment, to 9 point, degree 5.

Because the red line will cut the hopper at an acute angle I felt it would be better to build an extended surface and trim it back.
I put a plane through the last guide, continued the guide curve to create an arch with nicely matched end directions, and built a simple profile to blend from the guide tube to the peak of the arch, passing through the quad of the red curve.

I wanted to use edge surfaces to build the hopper, but thee didn’t give me enough control to easily pull them to the red curve. Instead I put a series of planes through the chute and used curve through points to run curves continuing the chute profile up through the red line and the profile curve.

I lofted the curves to create a pair of bulbous surfaces, most of which will be trimmed away, but with some chance of matching the chute.

The surfaces don’t coincide with the whole of the red line, so I had to do some CP pushing and pulling to wrangle them in line. As I was deliberately making a clean surface wobbly, this was a more forgiving process than usual…

Once satisfied, I matched the new surfaces to the guide ring, the chute and each other. It was necessary to use the refine option to get the matches, so the surfaces became heavier, but the hard work was done so I can live with that.

I could then use the red line to trim the chain path to its final shape. (full disclosure: I’d skimped the CP pulling because it’s not my project so I cheated and pulled the red line slightly to the surfaces to get the intersection).

Chain Path 004.3dm (6.3 MB)

HTH
Jeremy