Barrel cooling duct for MendelMax 2 & JD Duallie Belt Driven Extruder

I was having heat creep issues in my J-Head barrel during dual extrusion that wouldn't be a problem with single extrusion either. It is recommended to cool the barrel anyway. I designed this to fight that problem. I also wanted to prevent intake and exhaust turbulence from cooling the part.

This is designed around the J-Head hot ends, it would work with hot ends with a 16mm diameter barrel.

I intended this for use with ABS and other materials where cooling the part would be unwanted. For P