[KiwiBacon]

Originally Posted by curtis73

Computer aided drafting.



Chromemoly seems to be getting replaced by 1020 in a lot of applications. I think 1020 is a bit more expensive, but its not as difficult to weld.

as far as metallurgy, here is a very basic primer for you:
http://home.sprynet.com/~monel/metallurgy_faq_v11.htm
http://en.wikipedia.org/wiki/Tensile_strength

That second link discusses tensile strength, but under the "see also" there are links for the other physical properties of materials.

1020 is plain carbon steel with 0.2% carbon content. It's just plain old steel.
Chromoly is a fairly generic term, but if you chose something like 4130 (what most people mean by chromoly) it's tougher than plain carbon steel, especially when heat-treated. But the ultimate tensile strength isn't much different.

My advice, if you want to build a tubular steel chassis or space-frame then build the first one from mild steel exhaust tubing. It's cheap and will bend a long way before it breaks.
Once you've got the layout and function right, then buy some of whatever you'd like it to be built from.