This is a modification of the X axis for Geeetech i3.
The x rods are placed horizontally instead of vertically and the extruder is turned into a Bowden setup. It fits original printer's Z interaxis and larger as it is adjustable in that direction.

The belt and motor are rotated 90 degrees too.

Interaxis of X axles is 45mm.

The belt locking plate and extruder cooling case should be glued together to the bearing support to insure they will not come loose (I still didn't glue it and didn't came loose even after many prints, but I suggest glueing...)

The Z low endstop has an adjustable plate to fix it on the original plate, but the trigger now is the step motor lower side of the body (this may need some fiddling as my printer is a bit modified so I cannot test it).
The x carriage has accomodation for X min end stop screw if you want to keep it further away from the side, otherwise it is the carriage itself that will trigger the endstop. As there are multiple fittings for microswitches, you can add a max endstop microswitch too.
Fit for a 40x40mm cooling fan.
You will need a longer GT2 belt.
Additional hardware are 2 fittings for the Bowden tube, M6 thread, and a few M6 nuts and M6 washers (both normal and large size) for the cooling part of the filament tube.
There is an assembled rendering to show the setup, plus the files for each single part.
Printing area increase to 240mm with original LM8LUU bearings, 250mm with shorter LM8UU bearings.
Where the x rods are inserted in the laterale supports, there is place for a screw and nut that is used to compress the x rods and relieve any pressure on the z axis when the belt is tightened. I made the two lateral supports identical, there is an extra plate to fit the idler pulley on one of the two. The Z axis threaded rod's nut is not fixed to the lateral supports but is free to move sidewasy to help decrease wobble for bent rods and the original Z bearing is mounted upside down.

As my Z-axis is modified, I don't know if there is any loss in vertical printing area; the different orientation of the X rods make the extruder nozzle a bit lower than before but the different height of the side carriage itself should make up for this difference with probably a little gain.

The parts should be printed oriented as they are and if your printer has a decent bridging ability, there is no need for supports at all. Shoulb be enough around 15% infill.
I printed the belt lock at 0.4, was ok but a 0.3 would be better.

UPDATE 6/6/18
Reworked X carriage with clamping for bearings.

mini heatsink
Mini heatsink

extruder heatsink mk10
Heatsink MK10

heatsink washer
Heatsink washer

extruder throat mk8
Extruder throat MK8

4mm teflon tube connector
Teflon tube connector 4mm

30mm fan
30x30 cooling fan

40mm fan
40x40 cooling fan

GT2 belt
GT2 belt

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