printrbot simple fan duct and tensioner

The fan/tensioner combo on the simple just doesn't really cut it for cooling. This is a little more like the setup you get when you get the new one with the aluminum extruder. The fan bolts will screw into the fan holes, just like they do in the wood version. A small wood screw or two to attach it, and you are good to go.

The replacement tensioner is two parts printed in place, with support material. It takes some whittling to finish it, but it works, and has the added benefit of holdi