Deprecated, upgraded to Hemera and overhauled gantry there:
=> https://libre3d.com/category/708/CoreXY/listings/1307/TronXY-X5S-CoreXY-MGN12-linear-rail-on-2020-profile-conversion-with-E3D-Hemera.html <=
Documentation of build at: https://burningbecks.wordpress.com/2018/12/25/new-y-gantry-stacking-the-pulleys-again/
This OpenSCAD file generates parts for the linear rail conversion of a TronXY X5S (or potentially any other CoreXY printer made from 2020 aluminium extrusion).
The pre-compiled STLs are meant for another 450mm long rail on the X axis (the .scad can generate a variant for 400mm rails) and threaded sleeves as idler axles.
If you can't find threaded sockets / sleeves with outer diameter 5mm, length 30mm and M4 inner thread you can still fall back to M5 screws - just compile it accordingly with OpenSCAD version 2015.03-2.
The "ABS_support" parameter and the ...ABS.STL are meant for tricky materials like PC-ABS (Lilypads and extra support are designed in).
Remove or exchange logos according to your gusto.
If you don't have "GT2-20T-6-5B" (GT2 pulleys with 20 teeth, 5mm bore for 6mm wide belts), change parameters to yours, but watch for alignment with motor and corner pulley mount! (Suggested read before designing yourself: https://drmrehorst.blogspot.com/2018/08/corexy-mechanism-layout-and-belt.html - I know my carriage is off! It's up next. ;-) )
EDIT - It's there: https://www.youmagine.com/designs/tronxy-x5s-x-carriage-for-mgn12-linear-rail / https://burningbecks.wordpress.com/2019/01/15/matched-x-carriage-including-xcr-bp6-and-petsfang/
EDIT 2 - Just uploaded some more rugged motor mounts: https://www.youmagine.com/designs/reinforced-motor-mounts-with-bushing-for-shaft