Rework of Central Carriage from project "X3D XS CoreXY by Unix"
Made for use with bowden extruder.
In my printer it works with this extruder: http://www.thingiverse.com/thing:275593
EDIT april, 3, 2017:
This carriage is tested and proven to fit and work, although I've had big problems with printing quality and oozing caused by play in indirect bowden system. I think it is more resonable to use lightweight NEMA 17 motor with original direct extruder carriage instead of this. (File named central_carriage in http://www.thingiverse.com/thing:730199/#files)
My advice: only use bowden feed extruder if you for some reason really need it. Direct is better in spite of his downside (weight).