// -*- C -*-

holespc = 20;

len = 50;
width = 20;
backspc = 10;
light_height = 12.5;
hole_from_back = 7.2 + 0.5;
hole_dia = 3.5 + 0.5;
bolthead_dia = 7 + 1.0;
bolthead_depth = 5;

height = light_height + backspc;

octagon_fudge = 1/cos(22.5);

module Bracket(){
  difference(){
    translate([-len/2, 0,0])
      cube([len, width, height]);
    for (xsgn=[-1,+1]) {
      translate([xsgn * holespc/2, -1, light_height - hole_from_back]) {
	rotate([-90,0,0]) {
	  rotate([0,0,360/8/2]) {
	    cylinder(r=bolthead_dia/2 * octagon_fudge,
		     h= bolthead_depth +1, $fn=8);
	    cylinder(r=hole_dia/2 * octagon_fudge,
		     h=50, $fn=8);
	  }
	}
      }
    }
  }
}

Bracket();