9 outer_d1 = tube_d + 2*wall;
10 outer_d2 = tube_d + 2*wall + hole_h * 0.7;
15 cylinder(r1 = outer_d1/2, r2 = outer_d2/2, h = hole_h, $fn = 16);
16 translate([0, 0, hole_h]) scale([1, 1, top_h*2/outer_d2])
17 sphere(outer_d2/2, $fn = 16);
19 translate([0, 0, -eps])
20 cylinder(r = tube_d/2, h = hole_h + eps, $fn = 16);