Thanks to maker WashingtonApple I have fixed an issue where the opening for the 50mm fan was undersized. I made the vertical distance 51mm to allow for sagging and variations in printed size vs. modeled size.
The new/fixed file is Active_Duct_v3a_fixed. The model was parse through Netfabb, and re-imported into S3D to ensure it renders cleanly.
This has been painfully remixed in Sketchup over way too many hours to make it so that you can run a 50mm fan in a Replicator 1 / Duplicator 4 / FlashForge / CTC printer. I made it specifically for my Flash Forge Creator Pro, but it should work with the rest just as well. It shouldn't go beyond the original dimensions of the v2 Active Duct.
I did this mod because I wanted to be able to quiet my printer down. I've already upgraded most of the fans on both the extruders and the PSU to Gelid Silent fans. I've already modded my FFCP to have a 24vdc -> Adjustable vdc transformer, and I'll be running a Gelid Silent 5 50mm 12v fan at about 6 volts.
The Gelid Silent 5 (50mm) is rated 12.9CFM @ 12v @ 0.15Amp @ 23 dBA @ 4000rpm.
The Paps 414F fans (40mm) are rated 4.7CFM @ 24v @ 22.1 dBA @ 5400rpm
Long of it short, a 50mm fan underdriven will be quieter yet flow more air (assuming we get a linear drop in output).
Thruit00 uses Paps 414F fans, but these are 40mm fans which can be had from Mouser Electronics here: http://www.mouser.com/ProductDetail/ebm-papst/414F/?qs=fklqa858EevxfN57mkkqlw%3D%3D