Gas or TIG weld?

[gshearer]

Question about welding the chromoly tubing --- gas or TIG ?? please excuse me if this has already been discussed here - I did a search and pulled no good hits.

Is anybody TIG welding their fuselage? I have heard discussions about embrittlement with TIG vs. the wide area heating of oxy-acetylene. My welding experience is limited to a bit of stick welding and some OA, so I'd appreciate hearing views from you guys with a lot more experience!

Thanks

[Chris In Milwaukee]

This is a bit of religious subject, but either is fine. Your preference, mainly.

OA has the advantage of you not needing full-coverage welding gear while working with it. No sunburn due to UV exposure.

I have both, and I'll probably use TIG because of the precision heat control. But you have to have good tight-fitting tube joints for it to be "easy".

OA is easier to join larger gaps, from my limited experience.

Back when this group was on Yahoo! Groups, there were some adventurous discussions on the topic!

https://groups.yahoo.com/neo/groups/Bearhawk/search/messages?query=tig%20vs%20oa

~Chris

[Chris In Milwaukee]

A lot of great (spirited) discussion on the topic if you search:

http://www.homebuiltairplanes.com/

http://www.eaaforums.org/

Be warned, some folks are passionate!

[BTAZ]

For me, I used OA because I found it much easier to make "out of position" welds and easier to maneuver within the fuselage tubing than it would be with the typical helmet.

Used the typical Smith torch set, lightweight hoses, a "Gassaver" to make it pain free to start/stop, a good set of two stage regulators sourced from Ebay and three sets of "medium"(nominally 3' tall) tanks. I expect the setup could be reproduced for less then $500 if you buy used(including tanks)

I have a very nice ESAB 252 TIG and used it for welding the tanks and also on heavy steel parts(some of the landing gear and tail wheel for example) that I could weld seated at a bench.

However, one factor not often discussed is managing the tanks. Here in AZ it is very trouble free to own/exchange the tanks.No real issue with proving ownership and any type of tank can be traded for a different gas(I.E. CO2 tanks can be traded at face value for an equivalent sized O2 tank). Find a tank at a yard sale that isn't marked as a rental tank, buy it, and take it in and exchange it for what you need.

From reading other forums, there are parts of the country where it is very inconvenient to manage the tanks(can only be refilled from the vendor you purchased them from, can't get used tanks filled, lose your receipt from the prior fill and you are out of luck, etc.) which may be a factor.

[Battson]

When I did some welding to my Quickbuild fuselage, I used GTAW (the welder formerly known as TIG). Bob Barrows recommended I heat treat the GTAW welds with an OA torch to stress relieve them. This was done by heating the weld and wider area around the weld to a cherry red colour for a few minutes, and then gradually removing the heat and allowing the metal to cool slowly (basically simulating the OA welding process). Because the welds in question were in critical areas, I followed his advice to the letter.

[S Lathrop]

I was around for the welding discussion on the old Yahoo forum.

I think the best advise form that forum is use the welding process you do the best. Bad TIG welding may be worse than bad OA welding. Bad welding is just bad and should not be any where near an airplane.

My personal opinion is that the best process for doing the fuel tanks is to gas weld the seams with oxygen and hydrogen. The welds are much cleaner on the side opposite of the weld and the material is annealed in the area of the weld. Also the metal can formed in the areas of the welds without fear of cracking. Fittings are best welded with TIG.

I TIG welded my tanks because it has been decades since I did any aluminum gas welding. My fuselage is all TIG welded as well.

Stress relieving with an OA torch in critical areas is a good practice.

When you look at Indy cars form the 1950's, they had 70 gallon, aluminum tanks that were all gas welded. The body work was also gas welded.

[Ed Welfred]

I welded the tail with OA but switched to TIG for the frame because I purchased a tubing kit from VR3. Every joint was a perfect match and the TIG meant less distortion. I will post heat all joints. I also bought the Miller welding goggles and have a few different cheater glasses to insert into the goggles. I found the goggles instead of the helmet to be necessary to get into the difficult corners. TIG left a clean weld area. My OA tended to bring a certain amount of slag to the surface.

[Mark Goldberg]

At the kit factory we do some TIG but mostly O/A weld. We TIG in a few places where the distortion needs to be minimized. Also TIG fuel tanks. The reason I am posting here now is I am hoping this vast group of members can either confirm or contradict something that I have been saying - that we seem to be the only airplane factory in the world still O/A welding our 4130 tube fuselages. Does anyone know of another factory still gas welding tube fuselages other than us?? Mark

[Bdflies]

I think Mark is probably correct, for a couple of reasons. Oxy/acetylene welding has become an art form. In my 40+ years involvment in welding supplies, I knew of a mere handful of folks who could do it. I don't recall ever seeing anything O/A welded in a production shop. And I've been in a lot of shops... While it can be learned, if you run an ad, to hire a welder with experience in O/A welding, you might get lonely.
Another reason is cost. While Argon has never been cheap, it's been outpaced by the soaring cost of acetylene. Since the late 60's, the industry buzz was that acetylene would be phased out. Acetylene was a pain in the butt, back then and it's even worse now. Well, it's still around. It's become so much of a burden (ecologically, safety,etc..) it's limited to specialty applications, in industry. TIG equipment costs more, initially, but it's a more cost efficient process in a production environment.
I think Steve's advice is best: "do what you're good at."
Now, I have to ask Mark; Why do you use O/A at your factory?

Bill

[Mark Goldberg]

We do O/A welding at the factory for two main reasons. First and main reason is that Bob Barrows thinks O/A welding on 4130 is preferable to TIG. I know lots of opinions on this and I am not the least bit interested in getting into that discussion. But Bob is not your casual welder or uninformed, amateur student of metallurgy. He really knows about metals and how they behave. So we follow his lead on this. In addition - when we set up the factory we discovered another reason to be happy with O/A welding - Argon is 3 times the price in Mexico when compared to US prices. Apparently because no argon is produced in MX. All of it comes from the US. We still TIG a few parts like the tail surfaces where distortion on thin materials is more a concern. Mark

[jaredyates]

My local pro welder friend Alan Waters and I did some testing on the machinery at the community college with some parts that he TIG welded and that I gas welded. Keep in mind that I'm a relative newbie when it comes to welding, regardless of the process. His joint failed as a sudden snap with a clean break right outside of the HAZ. Mine failed with some clinking and tearing. One might conclude that his method was inferior, had it not been that mine failed in the high 5000 lb range and his failed in the low 7000 lb range. Both were on par with the calculated strength of the tube without any welds. His was a little over and mine was a little under.

Part of the reason we don't have as much discussion about it here is because the folks who were around in the Yahoo days exhausted the debate there, though this doesn't do much good for you of course!

I think we have good reason to believe that a properly executed weld is going to be fine from either of those two processes.

[Bdflies]

Well, if Bob prefers O/A, then that's good enough for me! Wasn't trying to draw you into the discussion, Mark. Really just curious.. BTW, Argon is a byproduct of Oxygen/Nitrogen liquefaction. If they produce Oxygen, which they do, Argon is produced. Pricing, on the other hand, is a whole nuther discussion! I could tell you stories! But, that would cost you beer (or rum...).
As for discussing welding processes, you have no idea how much I'd enjoy that furball!

Bill