+x_T_r = sina;
+y_T_r = -tana * sina;
+
+top_r = wall_r - (d_OC_r - 1);
+
+wall_x_r = wall_r / tan(90-alpha);
+
+top = top_r * r1;
+basew = base_r * rnom;
+
+echo(r0,r1, "ratio",r1/r0);
+
+module CrossSection(plus=0) {
+ difference(){
+ polygon([[-0.1, y_T_r * r0],
+ [x_T_r * r0, y_T_r * r0],
+ [x_B_r * r1, y_B_r * r1],
+ [x_B_r * r1 + wall_x_r * rnom + plus, y_B_r * r1],
+ [basew + plus, top],
+ [-0.1, top]]);
+ translate([0, -d_OC_r * r0])
+ circle(r = r0);