Conical Shell Drawing Calculator

This page will allow you to calculate the flat cutout design that can be rolled into an angled shell or curved armor. The output is just the dimensions of two arcs that, when given the same center point and connected together at each end, will provide the correct rainbow shape.

You can draw them using any tool you like, my favorite is e-machine shop. After you draw the arcs you can export as a dxf file that any waterjet shop or laser cutting place should be able to understand. I've used Big Blue Saw for such things in the past and had great luck. BBS has great service and is very accomodating. Instant quotes are especially nice. I've also found that Team Whyachi / Westar Manufacturing has better prices and more material options, but quoting isn't as easy with them. I will likely use them both again.

While I do not guarantee the accuracy of the calculation, I will say that I used this program to create the current shell for my 30 pound FBS Steel Shadow. I made the shell out of .125" thick 4130 and had it rolled at a local shop. They had to cut the arc into two pieces to make it rounder, so it might make sense for you to do the same with your waterjet drawing and stack the arcs to use a smaller sheet of material. The calculations are likely to be further from reality as the wall thickness increases, but .125" downward seems ok to me. I recommend putting numbers in for an an arc you can cut out of paper to verify that it works if you have doubts.