+ difference(){
+ union(){
+ translate(main_cnr_pos){
+ intersection(){
+ difference(){
+ circle(r = main_cnr);
+ circle(r = main_cnr * 0.5);
+ }
+ square([10,10]);
+ }
+ }
+ polygon([[ -top_middle_dr, middle_bot_z ],
+ [ -top_middle_dr, top_z ],
+ [ main_cnr_pos[0], top_z ],
+ [ side_thick, main_cnr_pos[1] ],
+ [ side_thick, -side_height ],
+ [ side_taper, -side_height ],
+ [ 0, -rivet_posn ],
+ [ 0, by_oring_z ],
+ [ -oring_x_rad, by_oring_z ],
+ ],
+ convexity=10);
+ }
+ translate([ oring_mid_dia/2 - main_dia/2, 0 ])
+ hull(){
+ translate([ 0, oring_y_rad ])
+ scale([ 1/oring_oblate, oring_oblate ])
+ circle(oring_thick/2);
+ translate([ 0, oring_y_rad*2 - oring_thick/2 ])
+ circle(oring_thick/2);
+ }
+ }
+}
+
+module StrapHoopProfile(){
+ circle(r = strap_hoop_thick/2);
+}
+
+module StrapHoop(){ ////toplevel
+ bigrad = strap_hoop_inside/2 + strap_hoop_thick/2;
+ extralen = strap_hoop_thick * 5;
+
+ intersection(){
+ rotate([strap_hoop_elevation, 0,0]){
+ for (x= [ -1, +1 ] * bigrad) {
+ translate([x, -extralen, 0])
+ rotate([-90,0,0])
+ linear_extrude(height= extralen + strap_hoop_strlen + 0.1,
+ convexity=10)
+ StrapHoopProfile();
+ }
+ translate([0, strap_hoop_strlen, 0]){
+ intersection(){
+ rotate_extrude(convexity=10)
+ translate([bigrad, 0,0])
+ StrapHoopProfile();
+ translate([0,50,0])
+ cube([100,100,100], center=true);
+ }