# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1398806437 -7200
# Node ID 1281a9daf3dd382e60797fe142853f6d2ea25f72
# Parent  ccc9692dbc0ef12ca4b3dfdab383d4407c677748
Added front "lug" feature to mate with the back "lug".

diff -r ccc9692dbc0e -r 1281a9daf3dd cartridge.scad
--- a/cartridge.scad	Wed Apr 23 23:45:56 2014 +0200
+++ b/cartridge.scad	Tue Apr 29 23:20:37 2014 +0200
@@ -167,7 +167,7 @@
 	(Acorn Support Application Group Note 014).
 	*/
 
-	/* Extra internal features. */
+	/* Extra internal features. Depths include front and back surfaces. */
 
 	pcb_back_support_width = 1.2;
 	pcb_back_support_depth = back_depth -
@@ -202,9 +202,17 @@
 	pcb_lug_offset_from_outside = 7.55;
 
 	pcb_lug_cross_width = 6.7;
-	pcb_lug_cross_depth = pcb_lug_depth;
+	pcb_lug_cross_depth = pcb_back_support_depth;
 	pcb_lug_cross_height = 1.4;
 
+	pcb_front_lug_depth = pcb_back_support_bump_depth +
+		pcb_front_support_depth - front;
+	pcb_front_lug_inner_radius = pcb_lug_outer_radius;
+	pcb_front_lug_outer_radius = pow(
+		pow(pcb_lug_cross_width / 2, 2) +
+		pow(pcb_lug_cross_height / 2, 2),
+		0.5);
+
 	/* Repeated constructs. */
 
 	module pcb_support(xdir, bump_height, bump_offset) {
@@ -271,6 +279,22 @@
 				}
 	}
 
+	module pcb_front_lug(xdir) {
+		translate([xdir *
+			(width/2 - pcb_lug_offset_from_outside),
+			-front_depth + front + pcb_front_lug_depth,
+			-height / 2 + bottom + bottom_from_base +
+				pcb_lug_offset_from_bottom
+			])
+			rotate([90, 0, 0])
+				difference() {
+					cylinder(h=pcb_front_lug_depth,
+						r=pcb_front_lug_outer_radius);
+					cylinder(h=pcb_front_lug_depth,
+						r=pcb_front_lug_inner_radius);
+				}
+	}
+
 	/* The actual shapes. */
 
 	translate([-width * 0.6, 0, 0])
@@ -338,6 +362,11 @@
 						pcb_support_margin,
 					0,
 					-height / 2 + bottom + bottom_from_base);
+
+			/* Circular "lugs" to hold PCBs in place. */
+
+			pcb_front_lug(-1);
+			pcb_front_lug(1);
 		}
 
 		/* Label insets. */