I plan to build a reasonably large (3m x 2m) moving-gantry router with quite a large z-axis (300mm or so travel hopefully), but I'm not yet sure how to approach making the gantry. I want to mount a 16hp ATC spindle I have bought already which weighs around 45kg, and I'm assuming a single box section, however big, probably won't be stiff enough over 2000mm. I'm wondering whether a pair (or more?) of welded aluminium or steel trusses would be a possibility? The finished space-frame could also be skinned in sheet to add to the stiffness (and to make it look less like a railway bridge!)

Anyone seen this approach used before?