Add chair piston guard

models/chair_piston_guard.scad

@@ -0,0 +1,19 @@
+// A cover for computer chair pistons, so you don't accidentally kick the greasy
+// piston. Nothing special, just a cylinder with 2 cylinders cut out of it.
+
+// These default values are for an ikea ALRIK and my (badly tuned) pronter.
+
+piston_dia = 28.2;
+outer_dia = 53;
+contact_length = 5;
+covered_length = 147;
+
+thickness = 1.5;
+
+difference() {
+    cylinder($fn=120, h=(contact_length + covered_length), d =(outer_dia + 2*thickness));
+    cylinder($fn=120, h=contact_length, d=piston_dia);
+    translate([0, 0, contact_length]) {
+        cylinder($fn=120, h=covered_length, d=outer_dia);
+    }
+}