11 cylinder(r = tube_d/2 + spring_r + wall, h = body_h);
12 translate([0, 0, wall]) difference() {
13 cylinder(r = tube_d/2 + spring_r, h = body_h);
14 for (a = [0:360/n_spring:360])
16 translate([tube_d/2 + spring_r, 0, 0])
18 cylinder(r = spring_r, h = body_h + eps, $fn = 8);