It will be a long long way ...

Somebody has done a locost with an arc welder ?
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Is this another "What is this question?"

I don't think you're following those plans closely enough.

I think its been assimilated by the borg

resistance is fertile!

I think is almost impossible to do it with the 25x25x1.5 mm RHS tube. I've been trying with 1.5 mm arcs and I'm very disappointed, the results are worse than the 2mm ones.

I'll do it with 25x25x2 mm tube (the difference of the weight is not important) and give me a 0.5 mm of margin over de 1.5 mm penetration of a good weld.

I'll weld the chasis with my arc welder, no doubts, but... I'll feel better if anybody has done this before !
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I've done a lot of mine with 2.5mm rods, you can't hang around though or else the pool drops out of the tube. It can be done though.

but you forget, the Borg strive for perfection!

I think your mistake was trying to weld that piece of painted wood on the middle of it!

I knew there were a few mistakes in the book!

There are mistakes in the book, pdfs, ... everywhere !!!