X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=reprap-play.git;a=blobdiff_plain;f=cable-splice-clamp.scad;h=c23c9367563383aa174adc6f4f827aa609449160;hp=b1f6876979f7afd2fd6256a722e05a4c2fac545a;hb=80554664accdac13cc2f4c6ee6c6dd0da04138ce;hpb=2e81016db65692fd06fd31351ea8df75c2e51c72

diff --git a/cable-splice-clamp.scad b/cable-splice-clamp.scad
index b1f6876..c23c936 100644
--- a/cable-splice-clamp.scad
+++ b/cable-splice-clamp.scad
@@ -1,34 +1,83 @@
 // -*- C -*-
 
-cable_maxdia = 12;
-cable_mindia = 6;
+include <commitid.scad>
 
-wallmin = 1;
-wall = 2;
+rnom = 9;
 
-delta_ellipse = 0.5;
+// alpha is slope angle, which is half of inner concave angle that
+//  wire sits in
+alpha = 40; // degrees
 
-// calculated
+// mu is minimum number of cable radii that cable tangent point (line)
+//  with splint ought to be away from edge of split
+mu = 1/4;
 
-outerdia = cable_maxdia / cos(30) + wall*2;
-delta_shift = 1 - delta_ellipse;
+// wall thickness, and base width as fraction of cable size
+wall_r = 1.5 / 6.5;
+base_r = 0.75;
 
-module CrossSection(plus=0) {
-  difference(){
-    for (dx = [-plus, 0, plus])
-      translate([dx, 0])
-      circle(r= outerdia/2, $fn=6);
+// for cross-section calculations:
+//
+// origin O is at intersection of straight line segments forming walls
+// C is centre of circle (wire x-section) (of radius r or radius 1)
+//       which is tangent to lines
+// T is said tangent points
+// B is inner base point, which is extension of line from B by mu*r
+
+sina = sin(alpha);
+cosa = cos(alpha);
+tana = sina/cosa;
+
+// blah_r is blah where r=1
+// d_AB is distance AB
+// dy_AB is " " " vertical component
+
+d_OT_r = tana;
+d_OB_r = tana + mu;
+
+d_OC_r = 1/cosa;
+
+dy_OB_r = d_OB_r * sina;
+
+// *0 and *1 relate to smallest and largest wire
+// r[01] is radius
+// r10 is radius ratio
+
+r10 = d_OC_r / dy_OB_r;
 
-    scale([cable_maxdia,
-	   cable_maxdia * delta_shift + cable_mindia * delta_ellipse])
-      circle(r= 0.5, $fn=30);
+r0 = rnom / sqrt(r10);
+r1 = rnom * sqrt(r10);
 
-    square(center=true, [40, (cable_maxdia-cable_mindia) * delta_shift]);
+x_B_r =   d_OB_r * cosa;
+y_B_r = -dy_OB_r;
+
+x_T_r =         sina;
+y_T_r = -tana * sina;
+
+top_r = wall_r - (d_OC_r - 1);
+
+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_r * rnom,   y_B_r * r1],
+	     [base_r * rnom,                top_r * rnom],
+	     [-0.1,                         top_r * rnom]]);
+    translate([0, -d_OC_r * r0])
+      circle(r = r0);
   }
 }
 
-linear_extrude(height=20)
-  CrossSection(0);
+module CrossSectionDemo(){ ////toplevel
+  CrossSection();
+  for (rc=[["red", r1],
+	   ["blue",r0]]) {
+    color(rc[0]) translate([0, -d_OC_r * rc[1]]) circle(r = rc[1]);
+  }
+}
 
-linear_extrude(height=1)
-  CrossSection(2);
+//CrossSection();
+CrossSectionDemo();