// -*- C -*-

arch_height = 24;
arch_width = 75;
end_width = 25;

arch_thick = 5;

// computed

arch_alpha = atan(arch_height / (arch_width/2));
arch_beta = 2*arch_alpha;
echo(arch_alpha,arch_beta);
arch_in_rad = arch_width/2 / sin(arch_beta);
arch_to_chord = arch_in_rad * cos(arch_beta);

end_thick = arch_thick;

//arch_to_chord = (arch_width/2)*(arch_width/2)/arch_height;
//arch_in_rad = arch_to_chord + arch_height;
//arch_in_rad2 = sqrt(arch_to_chord*arch_to_chord +
//		    (arch_width/2)*(arch_width/2));

//echo(arch_in_rad, arch_in_rad2);

module ArchProfile(){
  intersection(){
    translate([-200,0])
      square([400,200]);
    union(){
      translate([0,-arch_to_chord]){
	difference(){
	  circle(arch_in_rad + arch_thick, $fa=0.1);
	  circle(arch_in_rad, $fa=0.1);
	}
      }
      for (m=[0,1])
	mirror([m,0])
	  translate([arch_width/2,0])
	  square([end_width, end_thick]);
    }
  }
  %square([arch_width/2,arch_height]);
}

ArchProfile();