Originally Posted by UnsafeAlpine
Sorry about the question. I'm sure it's been answered before but there only seems to be 5 threads in this forum.
I've recently decided to try my hand at frankensteining some bikes and I'm wondering what the best way to attach all this stuff together. I have access to an oxy-acytelene welder but should I be looking into mig or tig welders?
No need, a gas torch will do just fine--on steel. You may need to get a smaller heating tip, which only costs $15 or so.
Aluminum can be torch-welded but it presents particular difficulties, no matter which kind of welder you have. (this is the reason there are far more custom-frame builders working in steel than aluminum)
Is there a noticeable difference in strength? I'll likely be using bikes with gas bike frames and I don't know if heat treating is a concern or even if I should worry about it.
I assume you mean "bikes with gas pipe
frames"? For casual-use stuff lots of people do use muffler pipe, electrical conduit or whatever. It is heavier than usual, and not very stiff tho'.
If you want to build something nice and permanent, it's not much more money to buy the good tube, which is 4130 steel. There's places online to get it but look around for local metals supply places first, as they are probably cheaper. Get .049" wall for kids bikes, or .065" wall for adult-sized bikes if you don't know which to pick. The next-thickness-up is .080", which would make a very strong but rather heavy frame.
Steel doesn't need to be heat-treated after welding; it re-hardens in a few days to nearly what it was before (-aluminum does
require re-heat-treating, which is why I said to avoid it-).
Also fillet-braze it with brass rod, don't weld. Welding thin steel causes a lot of metal on the back side to burn off. Brazing is at a much lower temperature and won't burn the steel at all.