add rod cover model

used to cover screws around rod and allow for big gear to turn.

3d_models/rod_cover.scad

@@ -0,0 +1,49 @@
+rad = 31;
+dx = rad/2;
+hole_sz=6.5;
+shaft_sz=30;
+
+full_h = 4;
+
+module screw_hole(x,y) {
+    translate([x,y,0]){
+        linear_extrude(height = full_h+5, center = true, convexity = 10, twist = 0, slices = 20, scale = 1.0) {
+            circle(d=hole_sz, $fn=50);
+        }
+    }
+}
+
+
+module ring(inner, outer, height) {
+    difference() {
+        cylinder(h=height, r=outer, center=true, $fn=50);
+        cylinder(h=height+1, r=inner, center=true, $fn=50);
+    }
+}
+
+union() {
+    difference() {
+        hull() {
+//          cube([42.3,42.3,full_h], center=true);
+        translate([17,17,0]) cylinder(r=6,h=full_h,center=true);
+        translate([-17,17,0]) cylinder(r=6,h=full_h,center=true);
+        translate([-17,-17,0]) cylinder(r=6,h=full_h,center=true);
+        translate([17,-17,0]) cylinder(r=6,h=full_h,center=true);            
+        }  
+        translate([0,0,-1]){
+            screw_hole(dx,dx);
+            screw_hole(dx, -dx);
+            screw_hole(-dx,dx);
+            screw_hole(-dx,-dx);
+            
+            linear_extrude(height = full_h+4, center = true, convexity = 10, twist = 0, slices = 20, scale = 1.0) {
+                circle(d=shaft_sz, $fn=50);
+            };
+        }
+    }
+    
+    translate([0,0,full_h/2]) {
+        ring(15,17,2);
+    }
+}
+