// -*- 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();