fuselage welding

[TFF]

You get admonished at Oshkosh if you make the torch pop because it erodes the tip. I would say in an emergency fuel off first. Non emergency, however you want.

 

[Pilot-34]

One of my weird interests was to look at the hydro date of all of my O2 bottles when exchanged to see how old they were.
Kind of amazing how old some of them are. Wasn't uncommon (as of 15 years ago) to get bottles with the first stamp in the 1800's.

All of mine are half full - and out of date.

In 1988 I bought a few tools at a yard sale and asked the old guy if he had any more stuff he wanted to get rid of ? He said yeah he had his dad‘s tourch, but he thought it was pretty old and
he told me that he’s pretty sure the bottles hadn’t been filled since before the war.
I was thinking the Vietnam war, since it was my war . Now I thought that was pretty old so I set them bottles in the back of the shop and didn’t think anymore about it till one day I came out and my son was using them. I was amazed that both the oxygen and the acetylene worked , Then when I took them in to get refilled, I asked the guy if he could tell when they were last filled.
He looked at them and kind of quizzically asked me if there was any chance that they were last filled in 1928 !
Guess I was thinking the wrong war !

 

[Pops]

In 1988 I bought a few tools at a yard sale and asked the old guy if he had any more stuff he wanted to get rid of ? He said yeah he had his dad‘s tourch, but he thought it was pretty old and
he told me that he’s pretty sure the bottles hadn’t been filled since before the war.
I was thinking the Vietnam war, since it was my war . Now I thought that was pretty old so I set them bottles in the back of the shop and didn’t think anymore about it till one day I came out and my son was using them. I was amazed that both the oxygen and the acetylene worked , Then when I took them in to get refilled, I asked the guy if he could tell when they were last filled.
He looked at them and kind of quizzically asked me if there was any chance that they were last filled in 1928 !
Guess I was thinking the wrong war !

Makes me question what I have. Bet the gas bottle is very old. Replace the oxygen bottle a couple years ago. Can't remember the gas.

 

[Richard Roller]

You sure about that?


BJC

I was taught to turn off the Acetylene first, to blow out the flame with oxygen. A lot less smoke also.

 

[wsimpso1]

There is one thing that I haven't heard mentioned!, always shut off the oxygen first

There is a lively debate on this topic. In 1973 (pre-engineering program in high school) I was taught shut off fuel first. Why? In an emergency we will most likely do what we do every day, and with stuff that burns, cutting off fuel is really important. OK, this 11th grader learned as it was taught.

Since then, in Builder Education Center at AirVenture, we teach oxygen, then acetylene for turning off the fire. Quiet, peaceful, nice. When I asked if there was a technical reason behind it, the leader actually investigated. Came back that the "pop!" deposits ash inside the torch that can not really be removed, making popping while welding more and more common with time. OK, I hate it when my torch pops, so that is how we teach and now do this at home too. I also teach and operate with a rehersal of closing the acetylene bottle valve if ANYTHING untoward happens.

People talk about it both ways. I don't know the answer, but I would love to see something definitive on it that also that fits with the physics.

and also install a backflow preventer between your torch and the acetylene hose. If your kit didn't come with one it's worth a special trip to the welding store.

This one of those "yes do that" items. Really. If any of several faults occurs that drives mixed O-A up a hose and on fire, these gadgets will stop the action at a popped hose. A blown hose is scary enough, but think about the fire advancing inside the regulator and pouring acetylene and acetone at tank pressure out and on fire. Run your back flow preventers, which usually stop nastiness at the hoses. And if you have a runaway regulator, stop, fix or replace that regulator.

I witnessed a shop fire when the 'O' rings in an old torch failed and a friend came running out of the shop yelling, "Run, it's going to blow!" Sure enough he was cutting, had shut off the wrong gas first, the torch snapped, the oxygen went through/around the 'O' rings and ran up the acetylene hose, carrying a fire front with it.

OA cutting does frequently call for higher O2 pressure than acetylene pressure. But a regulator fault can cause much higher pressures and shove the fire back into the regulator too. Run back flow preventers.

Typically the fire going upstream will blow the hose it is in. So point the hoses away from the bottles so any fire coming out the hose fitting is NOT pointed at the tank valves. Then be that calm head who reaches over and gives the acetylene valve a half-turn to off.

Billski

 

[wsimpso1]

You get admonished at Oshkosh if you make the torch pop because it erodes the tip.

That is a new one on me, and I teach OA at OSH. I understood that we get ash in the torch from turning off fuel first, which makes the torch pop more over time.

I would say in an emergency fuel off first. Non emergency, however you want.

In an emergency, I too was taught cut fuel first.

 

[TFF]

I know you work in the practice area. I sat in on the presentation once and the presenter made a big deal of making the torch pop. I guess that was his thing and it’s not really transferred to the practice.

I believe a bottle has a lifespan of 100 years. Now days there are not many suppliers because of the big companies buying up small, so filling a different supply chain bottle can get someone stuck if the wrong buyout happens and you sat on one for a long time. Also because of 9/11, big bottles can only be rented not owned. I have a bunch of old big bottles that are good for nothing unless you have a understanding supplier that will swap out what you are allowed to have now days.

 

[ironnerd]

...OA can look horrible and be good

I'm counting on that

 

[SpruceForest]

Fascinating stuff re: choices on welding with other than TIG and OA, as well as leaving stuff out the designer wanted left in...

From the 2022 Bearhawk LSA accident... freshly released NTSB report.

The pilot built the airplane from plans, and its primary fuselage structure was made of tubular steel covered in fabric. He used an unapproved welding process to construct the airframe and used thicker walled tubing to compensate. Postaccident examination of the wreckage showed the weld quality was generally poor, and a set of structural bracing components in the main wing spar carry-through section was omitted. Even with the poor build quality, the steel airframe structure appeared to be intact before impact. The omission of the braces alone would not have resulted in the failure of the wing as observed: however, the combined effect of the omission and modifications would have affected the overall structural integrity of the airplane.

From later in the report's Airframe Structure:

The tube widths of all the steel airframe members met the diameters specified in the plans; however, most tube walls were about 30% thicker. The steel tube members appeared to have been welded using the metal inert gas (MIG) arc welding process, contrary to both the kit manufacturer’s recommendations and FAA best practices. According to friends of the pilot, he had elected to use thicker gauge tube because he was using a MIG welder and was aware of the increased weight penalty that using the thicker tube would incur.

The weld quality was generally poor throughout, with multiple areas of incomplete fusion, porosity, and burn-through. Of note, the left fore-aft lower wing box longeron exhibited an incomplete weld to the left aft vertical support, with no penetration, and had detached (figure 3). However, the remaining airframe welds in all other locations were correctly oriented, and appeared intact, with any separation failures occurring in overload just beyond the weld fillets.

The airplane’s plans called for diagonal bracing of the main wing spar carry-through area in the upper cabin. Examination of the airframe revealed that the carry-through structure bracing was missing. Review of the pilot’s build logs and airframe remnants indicated that the bracing had never been installed; nothing in the build logs indicated this omission was intentional.

The designer of the airplane performed a structural analysis to calculate how the omission of the bracing would affect the airframe integrity. The results indicated that the carry-through would lose about 20% of its compressive strength, with little change to tensile strength.

And finally:
The National Transportation Safety Board determines the probable cause(s) of this accident to be:

An excessive pitch control input for undetermined reasons while the airplane was operating above maneuvering speed, which led to a structural failure of the right wing during cruise flight. Contributing to the accident was the poor construction quality of the airplane and the inadvertent omission by the pilot/builder of a series of structural airframe components.

The report, WPR22FA169, is available here: https://data.ntsb.gov/carol-main-public/keyword-search

 

[john87]

I have a question about O/A welding equipment. I have a Victor torch set with an oxygen and acetylene bottles. I have always used it for cutting only. I have a Lincoln 225 for my welding needs. The first question, is there an appropriate size handle for welding. My handle with a welding tip seems very large and somewhat heavy. I have seen the small torches HVAC and plumbers use to solder and that looks like a nice size to get into tight spaces. Will it work? I assume changing to my larger bottles for welding convenience.

Second question, is can I substitute propane for acetylene when welding? When I got my torch set, I was just a poor new college graduate with a new wife and a child. I could not afford both an oxygen and acetylene bottle so used propane to cut. It was a little slower but worked. Would it impact welding?

Last question, someone suggested one of the Sport Air Workshops to get started. Will it provide enough hands on to feel confident to practice at home and be successful.

Thank you all with far more experience in this aircraft welding world.

Jeff

Hi there,

You cannot use propane or anything else either, despite what makers of various gases might like to claim. You see, it is not just a matter of heat, it is a matter of flame chemistry.

When you burn oxy acetylene in air the reaction takes place in two stages.

1, in the inner cone of the flame where it goes something like this; C2H2 + O2 form 2CO + H2

2, In stage 2 in the outer cone, CO + H2 + O2 form CO2 and H2O

The flame draws nearly as much oxygen from the air as it does from the cylinder, and so, greatly reduces oxidisation of your metal. You can see this quite clearly sometimes as you play the flame on steel. If the metal is cold, you can also see the H2O condensing on the plate..

john..

 

[Pops]

Fascinating stuff re: choices on welding with other than TIG and OA, as well as leaving stuff out the designer wanted left in...

From the 2022 Bearhawk LSA accident... freshly released NTSB report.

The pilot built the airplane from plans, and its primary fuselage structure was made of tubular steel covered in fabric. He used an unapproved welding process to construct the airframe and used thicker walled tubing to compensate. Postaccident examination of the wreckage showed the weld quality was generally poor, and a set of structural bracing components in the main wing spar carry-through section was omitted. Even with the poor build quality, the steel airframe structure appeared to be intact before impact. The omission of the braces alone would not have resulted in the failure of the wing as observed: however, the combined effect of the omission and modifications would have affected the overall structural integrity of the airplane.

From later in the report's Airframe Structure:

The tube widths of all the steel airframe members met the diameters specified in the plans; however, most tube walls were about 30% thicker. The steel tube members appeared to have been welded using the metal inert gas (MIG) arc welding process, contrary to both the kit manufacturer’s recommendations and FAA best practices. According to friends of the pilot, he had elected to use thicker gauge tube because he was using a MIG welder and was aware of the increased weight penalty that using the thicker tube would incur.

The weld quality was generally poor throughout, with multiple areas of incomplete fusion, porosity, and burn-through. Of note, the left fore-aft lower wing box longeron exhibited an incomplete weld to the left aft vertical support, with no penetration, and had detached (figure 3). However, the remaining airframe welds in all other locations were correctly oriented, and appeared intact, with any separation failures occurring in overload just beyond the weld fillets.

The airplane’s plans called for diagonal bracing of the main wing spar carry-through area in the upper cabin. Examination of the airframe revealed that the carry-through structure bracing was missing. Review of the pilot’s build logs and airframe remnants indicated that the bracing had never been installed; nothing in the build logs indicated this omission was intentional.

The designer of the airplane performed a structural analysis to calculate how the omission of the bracing would affect the airframe integrity. The results indicated that the carry-through would lose about 20% of its compressive strength, with little change to tensile strength.

And finally:
The National Transportation Safety Board determines the probable cause(s) of this accident to be:

An excessive pitch control input for undetermined reasons while the airplane was operating above maneuvering speed, which led to a structural failure of the right wing during cruise flight. Contributing to the accident was the poor construction quality of the airplane and the inadvertent omission by the pilot/builder of a series of structural airframe components.

The report, WPR22FA169, is available here: https://data.ntsb.gov/carol-main-public/keyword-search

MIG can look good and have no penetration. One time I dropped a piece of steel that weighed about 400 lbs from about 250' up in the boiler building due to about 4' of a heavy weld that was welded in a fab shop with MIG with no penetration except for one place the penetration was about the size of an aspirin. Painted over and looked good. Very fortunate that no one was hurt or killed.
I do not own a MIG machine. Have used one a lot for tacking only in fabrication just temporary only to hold things in place until it would be completely welded with stick.

 

[wsimpso1]

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

An excessive pitch control input for undetermined reasons while the airplane was operating above maneuvering speed, which led to a structural failure of the right wing during cruise flight. Contributing to the accident was the poor construction quality of the airplane and the inadvertent omission by the pilot/builder of a series of structural airframe components.

The report, WPR22FA169, is available here: https://data.ntsb.gov/carol-main-public/keyword-search

So, the fuselage was overweight from substituting thicker tubing, many welds were real crap, important parts were omitted, one joint failed completely, but it still took the pilot going well beyond g limits to fold up a wing (not a welded assembly) and make it crash.

One thing not talked about was if extra weight contributed to the wing failure - the fuselage truss had to be a few pounds heavier than one built to plans. Probably not much difference.

So... It still took pilot error of the "pull the wings off the airplane" variety to have a crash. Usually a really bad day happens when a wing folds up, no matter what else was wrong with the fuselage, crappy welds or not.

Billski

 

[SpruceForest]

Amazing how bad welds can be and still be strong enough to work for a long time. Sounds like elevator somehow went full deflection and aircraft above maneuvering stressed things a bit too much.

 

[wsimpso1]

I have a question about O/A welding equipment. I have a Victor torch set with an oxygen and acetylene bottles. I have always used it for cutting only. I have a Lincoln 225 for my welding needs. The first question, is there an appropriate size handle for welding. My handle with a welding tip seems very large and somewhat heavy. I have seen the small torches HVAC and plumbers use to solder and that looks like a nice size to get into tight spaces. Will it work? I assume changing to my larger bottles for welding convenience.

Most any torch can mix acetylene and oxigen and cause it to burn just off the tip. Issues are weight & balance, ease of balancing the flame, variety of tips available, etc. If a torch is hard to use, the welder will tire more easily, which both interferes with learning and interferes with getting work done. I have a Meco Midget (Tin Man Tech sells them) and it is tiny and can get into all sorts of places to weld clusters. Small can work...

Second question, is can I substitute propane for acetylene when welding? When I got my torch set, I was just a poor new college graduate with a new wife and a child. I could not afford both an oxygen and acetylene bottle so used propane to cut. It was a little slower but worked. Would it impact welding?

Look up adiabatic flame temperature for O2-Acetylene and O2-Propane. Then look up melting point of 4130 steel. The bigger the difference in temperature between them, the easier it is to get heat in a particular place, make a puddle, add rod to the puddle, etc.

Last question, someone suggested one of the Sport Air Workshops to get started. Will it provide enough hands on to feel confident to practice at home and be successful.

Great classes. The point is to spend a long weekend running a torch, puddling, laying beads, and then putting stuff together. If you are capable of learning this, you will be well on your way, and ought to be fine for practice by yourself.

Well, let's qualify things. I have been teaching welding at OSH since 2015. Most folks who stay at it a couple hours can grasp the sub-conscious skill set to build on. In a weekend class you will get far more dedicated practice and coaching. I have seen lots of folks run the torch, come back and practice, and get it. Sadly some folks can not take direction and some folks simply can see well enough. Neither group was going to learn how to weld.

If you can read a paperback at 15", can hold a torch and rod at the angles we show you, and have learned any other hand-eye coordination and tool skills, you can learn welding. In WWII, industry made many thousands of unskilled laborers into welders of many types. Truth to tell, primary motivation was usually higher pay. Us? We want to build airplanes!

Billski

 

[wsimpso1]

You get admonished at Oshkosh if you make the torch pop because it erodes the tip. I would say in an emergency fuel off first. Non emergency, however you want.

Yeah, we teach quiet welding. I had not heard that it erodes the tip, just that it soots up the inside.

 

[wsimpso1]

In 1988 I bought a few tools at a yard sale and asked the old guy if he had any more stuff he wanted to get rid of ? He said yeah he had his dad‘s tourch, but he thought it was pretty old and
he told me that he’s pretty sure the bottles hadn’t been filled since before the war.
I was thinking the Vietnam war, since it was my war . Now I thought that was pretty old so I set them bottles in the back of the shop and didn’t think anymore about it till one day I came out and my son was using them. I was amazed that both the oxygen and the acetylene worked , Then when I took them in to get refilled, I asked the guy if he could tell when they were last filled.
He looked at them and kind of quizzically asked me if there was any chance that they were last filled in 1928 !
Guess I was thinking the wrong war !

As long as they pass hydro test every ten years, they are good to go. Really, swap bottles when yours go empty. Let the welding store handle the hydro testing, which they have done for a better price than we can get.

 

[Pilot-34]

As long as they pass hydro test every ten years, they are good to go. Really, swap bottles when yours go empty. Let the welding store handle the hydro testing, which they have done for a better price than we can get.

Lol I’m pretty sure these haven’t been tested for about 100 years. And I hope they stay in the family for another 100 so so they along with the rest of the tools in the set have a place of their own in the shop.
Sadly the hoses broke and crumbled on the way home after I bought the set .

 

[wsimpso1]

Lol I’m pretty sure these haven’t been tested for about 100 years. And I hope they stay in the family for another 100 so so they along with the rest of the tools in the set have a place of their own in the shop.
Sadly the hoses broke and crumbled on the way home after I bought the set .

Are you just going to let them sit? Welding supply houses won’t fill them if the hydro test has expired.

 

[john87]

Ok, and i am a PROPERLY qualified welder here in the UK with specific certificates for oxy acetylene welding...

In general use, you ALWAYS shut the acetylene off first.

The reason is that when you shut the acetylene off first, the still flowing oxygen burns up any remaining fuel gas [or hot bits of carbon] in the torch, and then purges the torch ready for the relight [to prevent explosions]

Secondly, if you shut the oxygen off first, you may very well have glowing bits or pockets of burning gas, that could trigger a backfire at least, when you open the acetylene valve to relight..

The only exception to this, is if you actually have a "backfire" This is when the flame retreats into the torch. The visible flame is extinguished but you will generally hear a screeching or whistling sound with back smoke coming from the nozzle... The body of the torch will also get VERY hot very quickly..

It has been known for the magnesium alloy [i believe the one brand here was] torch body to start to burn..

In the case of a backfire, you must turn the OXYGEN off first and immerse the torch in water until it has cooled. Even with both torch valves closed the burning inside the torch can persist for some time. When all over, the torch will be found to be full of soot.

I have only had this once in 50 years of welding..

I once saw a "sustained backfire" It was about 45 years ago. I was in a welding shop in college when i saw someone holding a cutting torch that was making a chain of explosions sounding like a machine gun. I ran over and shut the valves off, and that was that.

Someone i know had a "flash back" This is caused by bad practice, not purging hoses and that sort of thing [I have never used flashback arrestors myself] Anyway, this chap went to light a torch and there was an instant explosion that blew the one regulator apart, or at least the gauge on it, causing him some injury... Apparently a flashback travels back up the hoses at 1400mph..

john..

 

[Pilot-34]

Are you just going to let them sit? Welding supply houses won’t fill them if the hydro test has expired.

Like I said they haven’t been filled or tested in about 100 years so I suppose they have earned a rest .