$fn=120;

D_I_1=27;
D_I_2=25;
H=10;
Dicke=2.5;
Delta=0.001;
Open=90;


difference() {
  union() {
    cylinder(d1=D_I_1+2*Dicke, d2=D_I_2+2*Dicke, h=H);
    hull() {
      translate([-(D_I_2/2-4),0,0]) scale([1,1.5,1]) cylinder(d=8, h=H*3/5);
      translate([-(D_I_2/2+5),0,0]) cylinder(d=10, h=2.5);
    }
  }
  translate([1,0,-Delta]) cylinder(d1=D_I_1, d2=D_I_2, h=H+2*Delta);
  translate([0,0,-1]) for(j=[-Open/2:360/$fn:+Open/2]) rotate([0,0,j]) hull() {
    rotate([0,0,+360/$fn/2]) cube([60,0.001,20]);
    rotate([0,0,-360/$fn/2]) cube([60,0.001,20]);
  }
  {
    D=4;
    translate([-(D_I_1+2*Dicke+D-(D_I_1-D_I_2)/2)/2,0,0]) cylinder(d=D, h=20, center=true);
  }
}