// -*- C -*- include rnom = 9; // alpha is slope angle, which is half of inner concave angle that // wire sits in alpha = 40; // degrees // 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; // wall thickness, and base width as fraction of cable size wall_r = 1.5 / 6.5; base_r = 0.75; // 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; r0 = rnom / sqrt(r10); r1 = rnom * sqrt(r10); 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); } } module CrossSectionDemo(){ ////toplevel CrossSection(); for (rc=[["red", r1], ["blue",r0]]) { color(rc[0]) translate([0, -d_OC_r * rc[1]]) circle(r = rc[1]); } } //CrossSection(); CrossSectionDemo();