Around-the-nozzle cooling ring

This is another cooling design, inspired by (but not directly based on) thing 5756.

I wanted to use Iwo's design, but I just upgraded to a MakerGear stepper plastruder on my Thing-o-Matic, and there wasn't enough clearance around the extruder nozzle to mount any fan ducts on the top side of the Z-stage. So, this design is a circular cooling nozzle that mounts around the extruder nozzle, just under the Z-stage.

It is fed by two 1/4" PVC hoses, attached to a fan mount that sits on top of the