The Biconcave script was used to create left and right profile. The two profiles were joined, and revolved around the x axis.
The resulting "dumbbell" was rotated to the z-axis.
A MoI helix along the z-axis, with radius greater than that of the dumbbell, was created, from bottom of dumbbell to top of dumbbell.
The helix was rotated, (with copy on), 180 degrees, along z-axis.
A line segment was drawn between the bottom ends of the two helices.
The line segment was swept along the two helical rails, created a helicoid. The attached .3dm is at this stage. The next two steps still need to be done.
The dumbbell was trimmed with the helicoid, to create two symmetric ribbons on the dumbbell.
The top edge of each ribbon was joined to make a curve, and a second curve, along the dumbbell.
(I like Michaels method, which may give similar results.)
A superb paper, with helices and OTHER types of spirals, and their varieties of "helicoids":
Spirals on surfaces of revolution
http://elib.mi.sanu.ac.rs/files/journals/vm/57/vmn57p2-10.pdf
Another (unstudied) link:
https://scholar.google.com/scholar?hl=en&as_sdt=0%2C48&q=Accelerated+Algorithm+for+Solids+of+Revolution+Converting+into+Ribbon+by+Spiral+Coordinate+System&btnG=
The existing MoI projection command does not seem to do radial projection(?)
- Brian
The two ribbons look cool, also.
