Need advice on gantry design

[routercnc]

1. Top and bottom rails need to be further apart, i.e. vertical part of the "L" needs to be taller.
2. Z axis is way too far away from the gantry, it needs to be as close as possible to it.
3. The Z axis plate should be wider, when looking at the front face of it. It needs 2 bearings on top and 2 on the bottom, these should be as far apart as practical to resist sideways deflection at the tool.

Agree, #2 and #3 will make any of the options looked at so far a little bit stiffer.

#1 Though is an interesting one. The results for torsional stiffness show that the horizontal L (0.030 mm deflection) is better than the vertical L (0.034 mm deflection). This is easy to understand as that load case has a combination of bending in the X direction (for which the section is now very deep), and twisting (for which the section is the same as before). The sum of these gives an overall benefit for the horizontal L.
But the vertical loading needs to be checked as this will now be less stiff for the horizontal L. This is important to resist sagging due to the spindle/Y axis mass and causing machined surfaces to be bowed.

From a practical point of view the vertical L is always going to be a good choice as it allows more fore/aft gantry travel for any given bed length. But from an analysis point of view it will be interesting to see which will win overall . . . . .