I know I saw some people (Jaime one of them I believe) play with openscad.
Well, I forgot most of what I learned about Freecad and am giving Openscad a try, kind of neat.
Just playing around, I came up with this on my own 
not too impressive, but fun. (I left out the fn=100) My computer seems to not mind that. Of course I am not into anything complicated, yet!
cube([10,10,10]);
difference(){
difference(){
translate([20,0,0])
sphere(5);
translate([20,0,10])
sphere(7);}
translate([20,0,0])
cube([10,10,10]);}
translate([30,30,0])
difference(){
linear_extrude(5)
hull(){
translate([10,10,0])
circle([10]);
translate([-10,-10,0])
circle([10]);
translate([-10,10,0])
circle([10]);
translate([10,-10,0])
circle([10]);}
translate([0,0,-1])
linear_extrude(10)
hull(){
circle([10]);
translate([-5,-5,-1])
circle([10]);
translate([5,5,-1])
circle([10]);
translate([-5,5,0])
circle([10]);
translate([5,-5,0])
circle([10]);}
}
