length = 76;
width = 40;
height = 20;
r = 4;
r_cable = 8;
wall = 2.5;
hole_dia = 4;
hole_dist = 5;


difference(){
    minkowski(){
        cylinder(r1 = r, r2 = r, $fn=100, true);
        cube([length-2*r, width-2*r, height], true);
    }
    translate([0, 0, wall]) minkowski() {
        cylinder(r1 = r, r2 = r, $fn=100, h=1e-100);
        cube([length - 2*wall - 2*r,
              width - 2*wall - 2*r,
              height - wall],
              true);
    }
    translate([length/2-wall/2, 0, height/2-r_cable+wall]) rotate([0, 90, 0]) union(){
        cylinder(h=wall+1, r1=r_cable, r2=r_cable, center=true, $fn=100);
        translate([-r_cable/2, 0,  0]) cube([r_cable, 2*r_cable, wall+1], true);
    }
    translate([-(length/2-hole_dist),
               (width/2-hole_dist),
               -height/2+wall/2]) cylinder(r1=hole_dia/2, r2=hole_dia/2, $fn=100, h=wall*2, center=true);
    translate([(length/2-hole_dist),
               -(width/2-hole_dist),
               -height/2+wall/2]) cylinder(r1=hole_dia/2, r2=hole_dia/2, $fn=100, h=wall*2, center=true);
}

//difference()
//translate([length/2-wall+1, 0, 0]) 
//rotate([0, 90, 0])
//        cylinder(h=2*wall, r1=r_cable, r2=r_cable);
//rotate([0, 90, 0]) union(){
//        cylinder(h=wall, r1=r_cable, r2=r_cable, true);
//        translate([-r_cable/2, 0,  0]) cube([r_cable, 2*r_cable, wall], true);
//}

// r=4, d=5mm
//    translate([-(length/2-hole_dist),
//               (width/2-hole_dia/2-hole_dist),
//               0]) cylinder(r1=hole_dia/2, r2=hole_dia/2, $fn=100, h=wall*2, center=true);