$fn=100;

difference(){  
  difference(){
   minkowski(){
    cube([219.5,52,40]);       
    cylinder(r=2,h=1); 
    rotate ([0,90,90]) cylinder(r=2,h=1);    
    rotate ([0,90,0])  cylinder(r=2,h=1);    
  }
    translate([-8,0,2]) cube([240,52,46]);
  }  
  translate([15, 65, 10]) rotate([90,0,0]) cylinder(h=80, r=1.6);
  translate([15, 65, 30]) rotate([90,0,0]) cylinder(h=80, r=1.6); 
  translate ([15, 10,-5]) rotate([0,0,90]) cylinder(h=9, r=1.6); 
  translate ([15, 44,-5]) rotate([0,0,90]) cylinder(h=9, r=1.6); 
     
}