Please review this router gantry idea

[Jonathan]

No, one tube will be much stronger. Second moment of area (J) is proportional to radius to the power 4. The deflection is inversely proportional to J, so this means that for instance one 200mm tube would deflect around 16 times less than a single 100mm tube. The big advantage with a single tube is it's the strongest shape in torsion, so if using two I'd make them rectangular/square section as the forces are now mainly bending not torsional.

So you can't really go wrong if you use a big tube. The same principles apply to box section...

http://www.mycncuk.com/forums/linear...alculator.html