// -*- C -*-

cable_maxdia = 12;
cable_mindia = 6;

wallmin = 1;
wall = 2;

delta_ellipse = 0.45;

// calculated

outerdia = cable_maxdia / cos(30) + wall*2;
delta_shift = 1 - delta_ellipse;

delta_shift_gap = (cable_maxdia-cable_mindia) * delta_shift;

module CrossSection(plus=0) {
  difference(){
    for (dx = [-plus, 0, plus])
      translate([dx, 0])
      circle(r= outerdia/2, $fn=6);

    scale([cable_maxdia,
	   cable_maxdia * delta_shift + cable_mindia * delta_ellipse])
      circle(r= sqrt(0.5) * delta_shift + 0.5 * delta_ellipse, $fn=4);

    square(center=true, [40, delta_shift_gap]);
  }
}

module CrossSectionDemo(){ ////toplevel
  color("blue"){
    translate([0, delta_shift_gap/2, 0]){
      difference(){
        circle(r = cable_maxdia/2, $fn=20);
	circle(r = cable_mindia/2, $fn=20);
      }
    }
  }
  
  linear_extrude(height=20)
    CrossSection(0);

  color("red")
    linear_extrude(height=1)
    CrossSection(2);
}

CrossSectionDemo();