[Henry Anthony]

DJ,

I believe you have the solution. I made a helix 1" wide with an axis offset by 1" with the coil distance of 3" (I think - it really doesn't matter for the sake of discussion). This results in a coil with a 4" diameter. The outside edge measured something like 12.9 somthing. A 4" diameter circle has a circumference of like 12.56. So I think what you suggest would work.