parametric pendulum rod to increase frame stiffness

Parametric_pendulum_rod/Parametric-pendulum-rod.scad

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+//------------------------------------------------------------
+// Parametric pendulum rod coupling to increase frame stiffness
+//
+// http://www.thingiverse.com/wardwouts
+//
+// You'll need four of these to connect two bars and an appropriate
+// M3 screw and nut
+//------------------------------------------------------------
+
+// This needs to be tight, so about 5.8-ish for M6; 7.8-ish for M8
+M6 = 5.8;
+
+// And this can have some play
+M3 = 3.5;
+
+// Thickness at its weakest point
+thickness = 3;
+
+// Distance between the two holes
+seperation = 1.5;
+
+// Diameter of the disc
+diameter = 30;
+
+//80 for nice cylinders; 16 for speed
+FN=80*1;
+
+height = M6/2 + thickness;
+
+echo(str("========================================"));
+echo(str("The combined height will be ", height*4, " mm"));
+echo(str("So use a screw of at least ", round(height*4 +5), " mm length"));
+echo(str("========================================"));
+
+module base(){
+	difference(){
+		cylinder(h=height, r=diameter/2, $fn=FN);
+		union(){
+			translate([0,0,-height/2]){
+				cylinder(h=height*2, r=M3/2, $fn=FN);
+			}
+			translate([-diameter/2,M3/2+M6/2+seperation,height]){
+				rotate([0,90,0]){
+					cylinder(h=diameter*2, r=M6/2, $fn=FN);
+				}
+			}
+		}
+	}
+}
+
+base();