Machine casing item

The casing is intended to be an ingredient in craft recipes for machines.
It isn't actually used in any recipes yet.  Although mainly a craft
item, it is defined as a node type, mainly to get an appropriately cubic
inventory image.  It is incidentally possible to place it as a node:
this makes some sense, although the empty machine casing isn't actually
useful as a node.

technic/crafts.lua

@@ -131,6 +131,15 @@ minetest.register_craft({
 	}
 })
 
+minetest.register_craft({
+	output = "technic:machine_casing",
+	recipe = {
+		{ "technic:cast_iron_ingot", "technic:cast_iron_ingot", "technic:cast_iron_ingot" },
+		{ "technic:cast_iron_ingot", "technic:brass_ingot", "technic:cast_iron_ingot" },
+		{ "technic:cast_iron_ingot", "technic:cast_iron_ingot", "technic:cast_iron_ingot" },
+	},
+})
+
 -- Remove some recipes
 minetest.register_craftitem("technic:nothing", {
 	description = "",

technic/items.lua

@@ -144,3 +144,12 @@ minetest.register_craftitem("technic:carbon_cloth", {
 	inventory_image = "technic_carbon_cloth.png",
 })
 
+minetest.register_node("technic:machine_casing", {
+	description = S("Machine Casing"),
+	groups = {cracky=2},
+	sunlight_propagates = true,
+	paramtype = "light",
+	drawtype = "allfaces",
+	tiles = {"technic_machine_casing.png"},
+	sounds = default.node_sound_stone_defaults(),
+})