From c25fc9c6959790b2d089c5d8b9761c99ff99611b Mon Sep 17 00:00:00 2001
From: "Jan \"Yenya\" Kasprzak" <kas@fi.muni.cz>
Date: Mon, 23 Jan 2017 13:41:06 +0100
Subject: [PATCH] chair spring - first version

---
 chair-spring.scad | 53 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)
 create mode 100644 chair-spring.scad

diff --git a/chair-spring.scad b/chair-spring.scad
new file mode 100644
index 0000000..e55e035
--- /dev/null
+++ b/chair-spring.scad
@@ -0,0 +1,53 @@
+infty = 100;
+eps = 0.01;
+
+wall = 2;
+spring_y = 24;
+spring_x = 8;
+spring_z = 8.5;
+
+spring_low = 1; // mm lower than spring_x
+
+clip_add_z = 5;
+clip_w = 15;
+
+// bottom
+translate([0, -spring_y/2, 0]) cube([wall, spring_y, spring_z]);
+
+// sides
+for (i = [-1,1]) scale([1, i, 1])
+	translate([0, spring_y/2 - wall, 0])
+		cube([spring_x, wall, spring_z]);
+
+// clip
+translate([0, -clip_w/2, 0]) cube([wall, clip_w, spring_z + clip_add_z]);
+
+spring_top_r = 12;
+spring_y_off = spring_y/4 - 1.2;
+
+difference() {
+	union() {
+		// center beam
+		translate([spring_x - wall, -spring_y/2, 0])
+			cube([wall, spring_y, spring_z]);
+		// round bottom of the spring
+		for (i = [-1,1])
+			translate([spring_top_r+spring_x- wall- spring_low,
+				i*spring_y_off, 0])
+				cylinder(r = spring_top_r, h = spring_z,
+					$fn = 128);
+	}
+	// top of the spring
+	translate([spring_x, -infty/2, -infty/2]) cube(infty);
+
+	// sides
+	for (i = [-1, 1]) scale([1, i, 1])
+	translate([-infty/2, spring_y/2, -infty/2]) cube(infty);
+
+	// round top of the spring
+	for (i = [-1,1])
+		translate([spring_top_r+spring_x- wall- spring_low,
+			i*spring_y_off, -eps])
+			cylinder(r = spring_top_r - wall, h = spring_z + 2*eps,
+					$fn = 128);
+}
-- 
2.43.0