X carriage Loop

this is a X carriage named Loop:
- for standart linear bearing LM8UU
- standart 50mm M4 fixation holes for extruder
- standart 50mm spaced rod (ex: RepRap Prusa, MendelMax etc.)
- Fan mount integrated
- Strong structure for a rigid ABS print (work as well with PLA of course)
- integrated belt tensionning system (one side only)

it's mainly a variant of http://www.thingiverse.com/thing:9869
what is different then?
- linear bearing are inserted from the side, not from the bottom
- linear housing is really tight avoiding use of plastic collar or screw (maybe too much, see instructions)
- the main structure has been reinforced because i found the Greg's version to be too bendable for a proper rigidity.
- Belt attachement position have been optimized to avoid collision with extruder gear (see my extruder Loop: http://www.thingiverse.com/thing:169372)
- Belt clamp include nuts cavity
- include fan mount holes with nuts for 40mm fan air duct. want one? I desinged