This is an upgrade design for my Reprap Prusa i3. It includes X Motor and Idler end replacements to make use of trapezoidal lead screws, improved bearings for the smooth rods and a belt tensioner adjustment. I found the original design using the original linear bearings to be fragile. I've also added a Z Stop to the motor end.

I've included holes on the top z shaft mounts for KP08 pillow block ball bearings (https://www.amazon.com/gp/product/B00W8W7RNG/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1) to further steady the trapezoidal lead screws. I don't have them installed on mine at this time however as my motors won't drive the additional load they impose.

Thanks to:
http://www.thingiverse.com/thing:111903 for the X adjust inspiration. Although I redrew everything from scratch, the design is almost identical to burtdonalds.

http://www.thingiverse.com/thing:542892 for the Z end stop idea. I've used the Blackhawk Prusa i3 ReWork - Adjustable Z Endstop in my printer, and incorporated the design into this upgrade.

Take a look at my X Stop design at http://www.thingiverse.com/thing:1798572.

EDIT:
Updated the Z Shaft Mount STL files as it appears I may have had one wrong. My apologies.

I've added different length Z Stop arms that mount to the X Axis assembly to accommodate different extruders. Pick the one that works for you. The short version should always work, but will require a longer screw. The medium version is the original length. I don't know if the long version will be of any use to anyone, but it is included.

EDIT 08-08-18
Added the SketchUp file so that others can improve upon the design. I've effectively abandoned my i3 clone for the time being as I am working with another printer when I have time.