union() {
difference() {
	cylinder( r=4, h=1.2, center=true, $fn=30);
	cylinder( r=3.4, h=1.2, center=true, $fn=30);
	translate( [3.5,-0.8,0] ) { cube( size=[2,0.5,1.2], center=true ); }
}

difference() {
	cylinder( r=3.4, h=1.2, center=true, $fn=30);
	cylinder( r=3.1, h=1.2, center=true, $fn=30);
	translate( [3,0,0] ) { cube( size=[1,2,1.2], center=true ); }
}
difference() {
	cylinder( r=3.1, h=1.2, center=true, $fn=30);
	cylinder( r=2.5, h=1.2, center=true, $fn=30);
	translate( [2.5,0.8,0] ) { cube( size=[2,0.5,1.2], center=true ); }
}

}