tau = 6.283;
function rads2degs(rads) = rads * 360/tau;

function ClipHook_r2(w,g,l,ye,k) = w/2 + g + w/2;
function ClipHook_r3(w,g,l,ye,k) = k * ClipHook_r2(w,g,l,ye,k);
function ClipHook_yce(w,g,l,ye,k) = g/2 + w + g + w/2 - ClipHook_r3(w,g,l,ye,k);
function ClipHook_xe(w,g,l,ye,k) =
	sqrt(pow( ClipHook_r3(w,g,l,ye,k),      2) -
	     pow( ClipHook_yce(w,g,l,ye,k) + ye, 2));

module ClipHook(w=1.2, g=0.2, l=0.0, ye=0, k=3.0, h=3.5) {
  r2 =  ClipHook_r2(w,g,l,ye,k);
  r3 =  ClipHook_r3(w,g,l,ye,k);
  yce = ClipHook_yce(w,g,l,ye,k);
  xe =  ClipHook_xe(w,g,l,ye,k);

  xc = -l/2;
  yc = g/w + w/2;

  echo("ClipHook(w g l ye k h) ", w, g, l, ye, k, h);
  echo("ClipHook r2 r3 yce xe =", r2, r3, yce, xe);

  $fn = 20;

  module jcirc(x,y) { translate([x,y,0]) circle(r=w/2); }
  module jarc(cx,cy,r,a1=0,a2=tau) {
    astep = (a2-a1)/6;
    size = 5*(r+w/2);
    translate([cx,cy,0]) {
      intersection() {
	difference() {
		circle(r=r+w/2);
		translate([0,0,-1])
			circle(r=r-w/2, h=h+2);
	}
	scale(size,size) {
	  for (ai=[0:4]) {
	    echo(" jarc ", a1,a2, astep, ai, rads2degs(a1 + astep*ai) );
	    rotate(rads2degs(a1 + astep*ai)) {
	      polygon([ [0,0], [1,0],
			[cos(rads2degs(astep*2)),sin(rads2degs(astep*2))] ]);
	    }
	  }
	}
      }
    }
  }

  linear_extrude(height=h) {
    jcirc(-xc, -yc);
    jarc(xc, yc, r2, tau*0.25, tau*0.75);
  }
}

ClipHook(l=3);