See the last iteration of this assembly at Sketchfab, where I uploaded my [WIP!] 3D printer following this link: http://is.gd/2XLAA4

NOTE: http://www.thingiverse.com/thing:1505842 is the newer version (as seen in Remixes Tab)

This is a WIP for a minimal Carriage for smooth rod based 3D printers. The current design uses 3 LM8UU bearings and features a two-screws mounting system for both the hotend mount in the front and the blowers system at the back. The lacking of the fourth bearing permits adding a board for breaking the wires connections for easy replacement of the toolhead.

The current design has been printed at 0.1mm, on the side, with the bearings holes pointing upwards.

I have added screenshots of different types of clamps that can be designed for the setup, one with an Inductive probe that is brought as close to the nozzle as possible, in between the two hotends and to the front, between the fans - using the fan shroud I have posted here: http://www.thingiverse.com/thing:1310496 - and one designed for a direct contact probe I have been toying with (http://forums.reprap.org/read.php?1,620626)(http://www.thingiverse.com/thing:1335303). The design options are endless, the only fixed parts are the central hole for the screw and the tongue and groove style joint that prevents rotating of the clamp.

I have attached DesignSparkMechanical rsdoc files for both the X Carriage and the DualHotEnd_Mount so you can download and play with them in CAD rather than STL surface geometry only.

Update 20042016: I have finally taken the challenge to re-design this X Carriage to feature a tensioning mechanism that would allow symmetrical tension adjustment of the two CoreXY belts. Check it @ http://www.thingiverse.com/thing:1505842

Update 30032016: I have uploaded an exploded view on Sketchfab at https://skfb.ly/MBrB

Update 03032016: I have added the Dual HotEnd Mount in the pictures, tailored for E3d-V6 dimensions (http://files.e3d-online.com/v6/Drawings/V6-175-SINK.pdf). Please let me know if you want the Inductive Probe Clamp too, or the DirectContact Probe maybe.
I have also attached the RSDOC of the mount.