This is a work in progress, but it already provides much stronger and uniform cooling than a standard basic cooler which just blows in a straight line. I also tried the crab claw fan duct by AK Erik and it didn't work well with a standard 40x10 fan.
I believe this approach is better than the brute force approach of using large or multiple fans blowing all over the place which cool off everything - including the heat-bed. The vanes are the key here - and are what sets it apart from other circular, doughnut looking coolers.
The idea here is to create a vortex which swirls around the print nozzle to concentrate the cooling in a tight area. I need to do a little more experimentation with the design of the vanes (which are hidden from view on the inside) to get the vortex focused even tighter.
I strongly suggest that you insulate your heater block with ceramic tape or similar insulating material to avoid melting the cooler. I've had no problem with the cooler melting with the ceramic tape/kapton tape in place.
You will probably need the mounting bracket file here. This part was remodeled and I think the dimensions are different from the original C-Bot and D-Bot.
You will also need a standard 40mm cooling fan and mounting screws.
UPDATE: I've designed an adapter which allows the use of a 50mm radial (centrifugal) fan with this. It provides very powerful cooling - I think actually TOO MUCH unless perhaps you are printing very fast with a very large nozzle. It has to be turned down to almost nothing if you are printing with a 0.4mm nozzle at normal speeds. In that case, I actually believe I have more control with the standard 40mm axial fan in place.
Print standing on the fan end. Supports are not needed (especially if you have a good layer cooling fan)
Print in ABS. If you use PLA it will almost certainly melt.