O/A on steel tube question

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So, I've scoured the web and my AWS recources and come up empty handed.I tried many forum search combinations before breaking down and asking:Would you be comfortable welding cold rolled 1.25”x.120” dom tubing together with o/a for a motorcycle fame? Proficiency aside. Is there some inherent danger in doing this that I'm missing?I understand you have a larger haz but couldn't it be mitigated by taking the time to let it cool sufficiently and going in 1/4 sections like you would with any arc process?Suggestions, precautions, advice, criticism, all welcome.
Reply:Many aircraft frames were gas welded back in the day. It can be done. I wouldn't call it a beginner project though (not knowing your proficiency level).
Reply:All steel can be 'heat treated' to a certain extent.  On mild steel, the relative lack of carbon makes heat treating of it more or less worthless.Bottom line, by welding on mild steel you will not create much danger from HAZ.Now, O/A welding puts a lot more total heat into the metal because its not concentrated.  As a result, the metal as a whole gets hotter and because you have more metal at hotter temperatures, it tends to cool much slower.   That's a good thing.The bad thing is warping of the metal.  More heat, more opportunities for distortion.  You might want to experiment a little to figure out how bad.  I suspect you will still want to go slow with even heat on both sides of any joint.One thing the LWS can help you with is blankets to wrap the tubing that will keep the heat in a little better.   You sill want to weld in an area with no drafts, but blankets can help.  My LWS has this thin, carbon based ones that can be torn by hand and they show  a picture of a blow torch on one side and a bare hand on the other (haven't tested that yet).  Should be able to wrap the tube, weld, then slide the wrap closer to the weld and let it cool.Now, I have done O/A welding and I have done TIG welding.  Similar techniques, TIG you get a lot closer to the puddle (need to hold the torch steadier) and you have remote control for instant variation on the heat.  TIG, IMHO, is about 100x easier.  Just my opinion (and the fact that I haven't done any O/A welding in about 10 years - and 10 years ago I did it because I was bored).One option you have is to tack the frame together and pay someone to finish weld it.  If you have good fit on all the tubs and you've cleaned everything to the point that a weldor only has to wipe it down and start at it, I suspect it wouldn't cost much at all.  Of course a good weldor would probably not trust that you provide good fit and cleaned the joints so when you talk to him, bring a sample of what you mean by 'clean' etc. when you ask for pricing.  A good weldor has heard "Hey, its ready to weld" about 1000 times and knows that 999 of those times it isn't.Con Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX
Reply:Yes,  and aircraft frames are still being done that way.  I have plans for one now that I hope to build someday.Check out this website.   It is owned and operated by a master metalsmith named Ken White.  A really nice guy.  He is on a couple of aircraft forums I haunt.  https://www.tinmantech.com/index.phpHe has  DVD's and books that he has made specifically about this type of welding.Victor Oxy weld/cut Setup Meco Midget Torch outfitEverlast 2016 250EX & Power Cool W300Lincoln Power mig 210MP  w/amptrol and Spool GunEverlast Powerarc 200 Hypertherm Powermax 45Bandsaw, Lathe, grinders, press, Bridgeport, etc.
Reply:.120 wall tubing is about the ideal case for O/A welding.  Thick enough to make welding easy and not so thick you run into the excess preheat time and large HAZ assosciated with O/A on materials over 1/4 inch.
Reply:Could you braze the frame in order to reduce the required heat.
Reply:Thanks everyone! Been a ton of help.Keep 'em coming.Never Blend In.
Reply:Originally Posted by HousedadYes,  and aircraft frames are still being done that way.  I have plans for one now that I hope to build someday.Check out this website.   It is owned and operated by a master metalsmith named Ken White.  A really nice guy.  He is on a couple of aircraft forums I haunt.  https://www.tinmantech.com/index.phpHe has  DVD's and books that he has made specifically about this type of welding.
Reply:Originally Posted by jbmprods. i just wish it was as easy as he makes it look lol.
Reply:Edmvnd, there is a most informative book available from Lindsay Publishing Inc. titled Aircraft Welding by L.S.Elzea.(www.lindsaybks.com)About $16.00, very good referance on O/A welding with lessons and many pictures.  If you are interested in this type of welding you should get this book along with another titled The Oxy-Acetylene Handbook from Linde Reference Library. Both are easy reads and lesson based. Hope this info helps you. Bob
Reply:What is dom tubing?  drawn over mandrel, figured that out within the edit window  The make your own airplane like in the 1920's is chrome moly tubing isn't it?  I am under the impression back in perhaps the teens frames of motorcycles cracked a lot more than now.  Of course they had some pretty large displacement engines and small tubing by today's standards.How you could possibly weld the steering tube to the backbone and downtubes or lower backbone and have any bearing pockets still in line is kind of hard to imagine. I would think they would need bored after done.Pretty much one would need a jig to hold allignment of the parts wouldn't they if you were to expect it to be true?  My oxy acetylene welds don't always do too good on the destructive tests and when re melting with tig lots of strange activity.  Even though I have asked for and paid for oxy acetylene rod I have my doubts that is what I got.Last edited by fran...k.; 01-09-2012 at 11:18 AM.Reason: added stuff
Reply:Bob - Thanks for the heads up on those two sites. That Hathi Trust Digital Library is an immense reference source.  Lindsay looks like it's going to have some great material too. Fran...k - There are plenty of plans for frame fabrication out there and they really range widely in terms of how much work you want to put into them.Never Blend In.
Reply:If I am O/A welding 4130 tubing I ask my local welding supply for some ER70S2 rod, same rod you would use if tig welding this.  If I where to ask for some A/O rod they would bring some RG45 as that is the rod that is most commonly used when using the O/A process these days.  Big difference in the two rods.  I try to match the rod as close as I can to the tubing I am welding.  Yes using jigs is necessary most times with tubing.  Again this is explained in the book I mentioned in my above post.  Hope this helps.  Bob