Extra long gantry and choice of dimensions - weight issues?

[soulvoid]

With regards to this thread http://www.mechmate.com/forums/showthread.php?p=5299&highlight=longer+gantry#post5299

I intend to build an 3500mm long gantry with 120x60 tubes. However the wall thickness available in 120x60 start at 4mm... Is 120x60x2mm a standard dimension in the rest of the world?

According to my calculations, the tubes at 3500mm over 6'(1800mm) and 4mm over 2mm would be about 60 kg heavier...(76kg vs. 17kg) I can live with slower acceleration/speed, but this seems like it might be a little too much...

Any comments appreciated.

[Gerald D]

Håvard, I have seen 120 x 60 in 2, 2.5 and 3mm wall thickness in Germany when designing some things for them before. It was in QSTE tube (higher strength) but that is not important for us. I would think these are very common sizes, in various steel grades.

[Gerald D]

Hebra (http://www.hebra.no/no_index.html) should be able to give you advice on where to look for it.