On Friday 30 April 2021 16:52:46 Adrian H wrote: > On Thu, Apr 29, 2021 at 1:58 PM Gene Heskett <gheskett@shentel.net> wrote: > > One final question: Once the circumference has been determined, do I > > subtract an equal amount from Y that I added to x to keep the > > circumference unchanged as I make it into an ellipse? Or is there > > some trig needed? > > Here are some approximations for the perimeter of an ellipse, with the > last one being "exact". It's actually way more complicated to compute > than that of a circle. > > https://www.mathsisfun.com/geometry/ellipse-perimeter.html Thanks for the link, bookmarked. But I already solved it close enough for the girls I go with. I made a SWAG based on the starting circle, made a 4mm thick test disk for a trial fit, had to add .3mm to the size and reduce the eliptical offset about 1%, made another at full thickness, fits perfect. Now I need to gnaw out the rest of it in $200 worth of extruded alu. Thanks Adrian. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene>