// -*- C -*-

tube_dia = 27.5 + 0.5;
lock_w = 42.5 + 0.5;
lock_d = 28.0 + 0.5;
main_h = 45.0;
backflange_d = 12;

back_gap = 7;
main_th = 2.5;
midweb_d = 3;

// calculated

front_th = main_th;

tube_or = tube_dia/2 + main_th;
back_ohw = back_gap/2 + main_th;
backflange_ymin = tube_or+backflange_d;

lock_0y = tube_dia/2 + lock_d/2 + midweb_d;

lock_or = [lock_w, lock_d]/2 + [front_th,front_th];

module oval(sz){ // sz[0] > sz[1]
  xr = sz[0];
  yr = sz[1];
  hull(){
    for (sx=[-1,+1]) {
      translate([sx * (xr-yr), 0])
	circle(r=yr);
    }
  }
}

module MainPlan(){
  difference(){
    union(){
      circle(r = tube_or);
      translate([-back_ohw,0]) mirror([0,1])
	square([back_ohw*2, backflange_ymin]);
    }
    circle(r = tube_dia/2);
    translate([-back_gap/2,1]) mirror([0,1])
      square([back_gap, backflange_ymin+2]);
  }
  translate([0, lock_0y]){
    difference(){
      union(){
	oval(lock_or);
      }
      oval([lock_w/2, lock_d/2]);
    }
  }
}

MainPlan();