Hobby project

[tonyfoale]

Thanks, Tony for sharing your thoughts on your project and the tip to the interesting mechatronics site.

FWIW: Given that an epoxy-granite filled gantry will be more rigid than a single vertical support of any design,
one remaining problem will be the gantry-to-spindle overhang distance (for the given precision of the linear rails).
Humble tip: You could mount the vertical rails on the outside of the gantry, to:
1) utilize the rail's inherent rigidity from their greater width (rather than their height, and perhaps even wider distance between the top and bottom bearing) and
2) thus improving overall rigidity by reducing the spindle overhang with app 30 mm.
Just my two cents...
ATB and good luck!
Johan

I did consider putting the vertical rails as you suggest but having decided to use plain granite slabs for the slides, and my lifelong membership of KISS, it was what the youth call a no-brainer to put the rails on the face.
However, I do plan on counterweighting the assembly, see these videos for hints on how I might do that.

and