I had need to make a cone and recalled Steve Hamiltons post with the disc method. I built off that to make a layout tool that will do multiple cones without needing to cut templates each time. It starts with a gun cleaning rod and a lawn mower wheel. The pens are set to the dimensions of the cone and move the wheel til it hits. There is a mark on the wheel to get 360 degrees. Hose clamps are marginal, have to fix that. I think I can add an eccentric and pivots on the pen mounts to do nonparallel truncated cones.
cone layout.jpg