Curve frame and curvature?

Looks interesting! I don’t know much about the black-smithing process, do you mean that the bar gets twisted axially into a sort of fusili-pasta shaped thing before being wrapped around the larger diameter form?
Does it get rolled into a flat circle shape first and then elongated vertically or do both actions happen at the same time?

I think what you’re looking for may correspond to the integral of the torsion of the curve along its entire length… although of course there’ll be all sorts of real-world complications compared to an idealized curve with zero thickness :sweat_smile:

Edit: Here’s an idea, you could try comparing the Perpendicular Frame (zero-twisting) component with the Curve Frame at the beginning and end of the curve, and see how much they diverge from each other.
I believe that should theoretically give you the total amount of twist, or at least provide an approximate starting point where you can tack on whatever necessary correction factors :slight_smile: See the attached: spiral.ghx (160.2 KB)