Hi All, I'll write a proper introduction in the appropriate forum but the brief back-story is that I have been in the 'design' phase of my CNC router build for about two years, slow progress due to time constraints etc. However I now find myself with a few weeks on my hands and I thought I would get properly stuck into the project. Here goes... Attached is a sketch of an idea that I had for the X axis gantry beam. Apologies if some of my mechanical terminology is incorrect, it isn't my forte; I was thinking about the forces acting on the X axis carriage once the Z axis assembly is mounted to it. I haven't worked it out, but the mass of the spindle and the Z assembly will be quite heavy and hanging it off the side of the gantry will produce a considerable rotational force (torque?) around some point in the cross section of the gantry profile (moment??). I was wondering whether there is anything to be gained by using the pictured arrangement over the more conventional arrangement of running both linear rails along the same side of the gantry beam. I have also seen designs that run the rails along the top and bottom of the beam. It seems to me that using this arrangement the linear rail carriages will be similarly loaded rather than one being pushed inwards whilst the other is pulled outwards. This is where my thought process runs out of steam. Firstly, am I over thinking this? Or, do you think that there anything to be gained from this idea? Paul.