Tube or pipe that changes sizes?

[pixelmonkey380]

to type an explanation without a visual would take several pages.

the goal is to create an expansion chamber, like that for a 2 stroke motorcycle exhaust. see google images here.

suggestions?
chris<pixelmonkey>:D

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[Rich O Brien]

You could do the follow but use more segments in your initial geometry to get desired results

[mitcorb]

Other tools you could use:
Lines to Tubes.
Pipe on Path
Tube on Path
Fredo Scale step by step, ring by ring with orientation of scaling to orientation of rings.

Curviloft, also, in a series of sections.