Any sugestions how to build my gantry

[Tom J]

In my opinion distance between rails should be at least 250mm for the gantry. So 150 is not enough. As you say another option is to make gantry from 2x 80x80 and some perpendicular pieces in between, to look like a stair.

That was a question I ask myself - how far apart should get the blocks on gantry
I use calculation








There are few rules of thumb:
Clearance between table and bottom rail of gantry should not be bigger than distance between bottom and top gantry rails - X axis. Something like that D2=D1 - (D3/2)





There is compromise between forces on blocks and torques on plates and rails - that is why I use Mathcad to use those distances as variables and see what are the results.

What the point to overbuild design by using heavy strong profile if we do not consider reactions on bearings caused by own weight and cutting force.

IMHO should be compromise between calculation and try and error build. At the end we will see if chatter, vibration and deflections occurs - real life:)