Fuselage Welding

[N96290]

Re: Fuselage Welding

I have seen first hand the problems of not pre and post heating 4130 tubing. In the late 60's I was into circle track racing and a tube frame modified which looked beautiful lost control and rolled several times. Pieces of the frame came flying out of the dust cloud and the tube had broken like glass next to a lot of the welds. Enough of the cage remained intact that the driver was not seriously hurt but that is about all that was left of that car. He was lucky in that the welds that would have killed him did not fail. The welding was done with at that time state of the art electric tig or mig welding equipment. There are newer welding materials and equipment which work better without pre and post heating than the old gas welding without treatment but there is still nothing like doing it right.

[Guest]

Re: Fuselage Welding

I have seen first hand the problems of not pre and post heating 4130 tubing. In the late 60's I was into circle track racing and a tube frame modified which looked beautiful lost control and rolled several times. Pieces of the frame came flying out of the dust cloud and the tube had broken like glass next to a lot of the welds. Enough of the cage remained intact that the driver was not seriously hurt but that is about all that was left of that car. He was lucky in that the welds that would have killed him did not fail. The welding was done with at that time state of the art electric tig or mig welding equipment. There are newer welding materials and equipment which work better without pre and post heating than the old gas welding without treatment but there is still nothing like doing it right.

"Right" according to who?

[N96290]

Re: Fuselage Welding

According to manual 18, the bible.

[mohawktipi]

Re: Fuselage Welding

O.K. it's not a Tcraft but I just purchased the plans for a Sonerai II LS. In reading through the material, it stated that TIG welding would require that the 4130 tubing be heat treated to restore strength properties. They strongly advise gas welding.

[mohawktipi]

Re: Fuselage Welding

After I posted my first response, it occured to me that this situation might best be solved by Occam's Razor "when you have two competing theories that make exactly the same predictions, the simpler one is the better."

Since we know that gas welding works and the TIG welding leaves many questions unanswered (in this situation) why not use the time proven gas method.

[Guest]

Re: Fuselage Welding

I have seen first hand the problems of not pre and post heating 4130 tubing. In the late 60's I was into circle track racing and a tube frame modified which looked beautiful lost control and rolled several times. Pieces of the frame came flying out of the dust cloud and the tube had broken like glass next to a lot of the welds. Enough of the cage remained intact that the driver was not seriously hurt but that is about all that was left of that car. He was lucky in that the welds that would have killed him did not fail. The welding was done with at that time state of the art electric tig or mig welding equipment. There are newer welding materials and equipment which work better without pre and post heating than the old gas welding without treatment but there is still nothing like doing it right.

Hi Lyn,

How did you determine that lack of pre/post heat was the root cause?

Dave

[Forrest Barber]

Re: Fuselage Welding

This getting ridiculous, I have first hand experience with the breaking right outside the weld on the mig welded stuff. Numerous experimentials that were done at home have had problems. The approved methods for the Taylorcraft are part of the TC ; the "new" factory had tried for deviations and I think a few of us have seen "those" struts and fuselages, what a mess. I am now out of the discussion and back to my torches for any repairs on 1025 or 4130 or the 1010 struts too!! I agree that MIG process in a controlled situation is very good, we have a lot of fab shops around us doing award winning motorcycles & cars , just don't use it for repairs on older aircraft. All this in MHO. Back to the big snow Event in NE Ohio.....

[Ragwing nut]

Re: Fuselage Welding

Do to the chromium content in 4130, concentrated heat will cause stress risers (embrittlement) in the grain of the metal and under proper circumstances such as an accident, it will fail along those stress risers unless the material is stress relieved. pre-heat is not as vital on thin wall materials, but post heat is an absolute.

1025 does not have chromium in it, so it is not as suseptible to embrittlement, but the issue becomes that you can make such a small pretty bead with TIG, there is not enough weld material to maintain structural integrity of the joint.

I build airplanes, custom cars, etc, and have gas torch, MIG, and TIG in the shop. However when I am working on aircraft, I always use the gas torch.

[Guest]

Re: Fuselage Welding

This getting ridiculous, I have first hand experience with the breaking right outside the weld on the mig welded stuff. Numerous experimentials that were done at home have had problems. The approved methods for the Taylorcraft are part of the TC ; the "new" factory had tried for deviations and I think a few of us have seen "those" struts and fuselages, what a mess. I am now out of the discussion and back to my torches for any repairs on 1025 or 4130 or the 1010 struts too!! I agree that MIG process in a controlled situation is very good, we have a lot of fab shops around us doing award winning motorcycles & cars , just don't use it for repairs on older aircraft. All this in MHO. Back to the big snow Event in NE Ohio.....

Yes it is. You indicted electric welding process then as we discuss TIG you change the subject to MIG and reference a lot of anecdotal information.

There is nothing ridiculous about asking how one determined the root cause of a problem or giving valid technical references.

I suspect that all modern aircraft manufacturers use TIG on their chrome moly engine mounts and do not pre/post heat. I suspect that because I was told that by Miller Electric.

[astjp2]

Re: Fuselage Welding

Forrest, what page of the type certificate says the welding must be Oxy/Acte? I have never see that once in any type certificate. Tim

This getting ridiculous, I have first hand experience with the breaking right outside the weld on the mig welded stuff. Numerous experimentials that were done at home have had problems. The approved methods for the Taylorcraft are part of the TC ; the "new" factory had tried for deviations and I think a few of us have seen "those" struts and fuselages, what a mess. I am now out of the discussion and back to my torches for any repairs on 1025 or 4130 or the 1010 struts too!! I agree that MIG process in a controlled situation is very good, we have a lot of fab shops around us doing award winning motorcycles & cars , just don't use it for repairs on older aircraft. All this in MHO. Back to the big snow Event in NE Ohio.....

[Guest]

Re: Fuselage Welding

After I posted my first response, it occured to me that this situation might best be solved by Occam's Razor "when you have two competing theories that make exactly the same predictions, the simpler one is the better."

Since we know that gas welding works and the TIG welding leaves many questions unanswered (in this situation) why not use the time proven gas method.

Hi Tom,

Yes Tom this is a good point indeed.

But one must also remember that while choosing this way it does allow you to select an acceptable method it does not prove that the alternate method is not also acceptable.

Its sort of why try to find the answer to an unncessary question. One might remain in a static state of welding technology with this method. That's not necessarily bad though.

Dave

[mike lutz]

Re: Fuselage Welding

An elderly ex IA in my area used to weld for Stinson during the war years and tells me they used to stick weld most of them.Also,I dont how reliable this is,but I was also told that Maule uses mig welding.A couple years ago I repaired a fuselage that a hangar had fallen on,and some of the welding had the bb,s and a few peices of wire at the weld that were not cleaned off.Maybe old repair,I dont know.Anyway,the way these aircraft are used in bush country i,ve never heard any horror stories about broken welds.Just my worthless two cents worth.I myself prefer and use the ox/acet method.

[rail]

Re: Fuselage Welding

I have been an A&P for 23 years along with a full career in the aviation and racing industries; fabricating, machining, shaping, spinning, welding and heat treatment of structural metal components.

AWS certified in welding pressure vessels in the aircraft industry! Trained to Boeing, Douglas, Grumman and Lockheed (WPS) Welding Process Specification!

Welded chassis and pressure vessels for Toyota Racing Development to there engineering specs.

Please do not pre and post heat the aircraft structure no matter what process you use!!! No matter if it is mild steel 1020 & 1025, normalized 4130 or heat treated 4130!

All you are doing is inducing "shrinkage" into the structure!

As for A&P's, they should be smart enough to know when to rely on a welder in the industry, not some preconceived antiquated practice!

Attached is a picture of a few of the welding references I use in decision making about welding. None of these advise the practice of pre and post heat of thin wall tube aircraft structures!!!

[astjp2]

Re: Fuselage Welding

I have seen pics of the oven that Stinson used, they post heated the entire fuselage in one piece.

An elderly ex IA in my area used to weld for Stinson during the war years and tells me they used to stick weld most of them.Also,I dont how reliable this is,but I was also told that Maule uses mig welding.A couple years ago I repaired a fuselage that a hangar had fallen on,and some of the welding had the bb,s and a few peices of wire at the weld that were not cleaned off.Maybe old repair,I dont know.Anyway,the way these aircraft are used in bush country i,ve never heard any horror stories about broken welds.Just my worthless two cents worth.I myself prefer and use the ox/acet method.

[astjp2]

Re: Fuselage Welding

2 minutes on google...found this

http://www.netwelding.com/Welding%204130.htm

During the WW II era 4130 high strength steel was used for some aircraft components. At that time oxy-acetylene was the welding process of choice for many of these items. The preheat and slow cooling inherent with that process made welding the nominal 0.30 carbon steel relatively straight forward (assuming one could oxyacetylene weld!). However with more modern welding process like TIG and MIG, the cooling rates can be much faster and care must be taken to avoid forming high hardness and brittle Martensite on cooling transformation. On heavier sections preheat and post weld heat treatment should be used. With the proper post weld heat treatment strengths of 200,000 psi can be achieved with reasonable toughness by tempering the Martensite that forms in the heat treating process. However when welding race car tubing, preheat is not often used nor are the parts post weld heat treated.

Most of the tubing used for race car construction is referred to as normalized. This refers to the heat treatment and cooling rate the tubing was subjected to in manufacture. Most normalized tubing will range in tensile strength from 95,000 to 110,000 psi. This can be welded with the proper filler metals to achieve similar strengths. Although there are more weldable grades of steel (those with lower carbon content from 0.06 to 0.15) in the 100,000 to 115,000 psi tensile strength range readily available for plate and sheet, 4130 remains a commonly used grade for tubing. Just be sure to take the precautions noted when welding.

The following is extracted from an article I wrote for the American Welding Societies technical journal called "The Welding Journal". It has additional information to that presented in the publication. You can Click This Link to see the article:
taken from link below....