+module ball_holder(){
+ gap = wall_thickness * 4;
+ difference (){
+ cylinder(r = holder_radius, h = holder_height);
+ translate([0, 0, ball_radius + holder_floor + holder_arms_length]){
+ sphere(r = ball_radius);}
+ translate([0, 0, holder_floor + (holder_height - holder_floor) / 2 + 0.5]){
+ cube([holder_diameter + 0.1, gap, holder_height - holder_floor + 0.1],
+ center = true);}}}
+