Update: Added nut-traps to the fan shroud and shared stl. Original shroud designed by "goopyplastic" here: http://www.thingiverse.com/thing:151551. 20140426 NumberSix.
Update: LM12UU version of x-carriage with Fan Mount uploaded. 20140425 NumberSix.
Please Note: This a modification to a Mendel90 x-carriage designed for LM8UU bearings and T2.5 belt. 20131012 NumberSix.
An under-carriage fan mounting position has been added to the Mendel90 x-carriage. It takes a 40mm fan and incorporates M3 nut-traps to make it easy to install/remove the fan when the carriage is already on the printer.
The purpose of the fan is to cool the hot-end insulator. There is more detail on my reasoning for this and how the fan is controlled, on my blog: http://numbersixreprap.blogspot.ie/2013/09/active-cooling-of-j-head-insulator.html
I got the idea from GoopyPlastic's alteration which is published here: http://www.thingiverse.com/thing:151551 and I'm also using his half-ducting from the same publication. Tks Goopy.
The original x-carriage is from Nophead's publication here: http://www.thingiverse.com/thing:17826 and latest version on Github: https://github.com/nophead/Mendel90/tree/master/dibond/stls
I'm marking this as "work-in-progress" as I've observed some manifolding messages with the STL in Sli3er which I've not been able to sort. The STL loads, slices and prints fine from Kisslicer.
I've included the Sketchup version of the part also if anyone wants to modify further.
Download STL, slice and print.
Insert M3 nuts in nut traps by threading the nut on to a bolt and pulling them into the trap. Depending on your print they may fit snugly or not. You can glue the nuts in if desired.
Wire the fan as appropriate to your printer.