Tube construction: Alternatives to conventional welding

Thanks,
Its my LMA,
to be fair the basic bonded and riveted construction method, is quite sound, Its just that LMA made a hash of the design process, so here in the UK
we are redesigning it for better assembly.

See pic of poor design practice below, this will be redesigned on our Mk2 version.

 

I haven't found any examples of a riveted steel tube fuselage, so there must be a reason, but I can't think of one.

 

The original Heath Super Parasol, from the 1930s.

Used steel tube with sheet metal gussets. Cold formed rivets made from roofing nails.

 

Common nails larger than 1/8" make nice rivets. Just hammer the edges with multiple little taps round and around.

 

Welding is the best choice for a 4130 tube fuselage, BUT, the cluster has to be fitted very tightly in order to keep excessive heat out of the joint. Properly fitted, one can make a small neat weld. Efficiency at work. BUT, I think a cluster attached without heat would be very interesting.
Any good rivets out there up for the task?
Huck bolts?

 

Why not just learn to Tig weld.............its very enjoyable. Don't get caught up in the idea that you have to make a "stack of dimes" weld appearance or else your weld is total crap. With a little practice you can make welds that are strong and look just fine. Its really neat when you can take a very small arc and assemble thin things together without dousing the whole assembly with excessive heat.

 

Noted. Please see first post in thread. Welding is fine, wonderful, soothing, therapeutic, functional, etc. Many people find it so. This discussion is to cover alternatives.

And, there are folks who believe that only welding is proper--BUT not TiG!! Egads! On an airplan?! Insufficient penetration, etc, etc. So even among the welding accolites, there are apparently sects and heretics.

Edited to add: You wrote the below section in post 72. What happened? okay, it has been a few years. . .

 

The point he was making though is not that there are alternatives but whether a need actually exists for one. Back in the 1920s and 1930s when what is today called aerospace welding was still being developed (read as: quality control issues and/or issues with design of safety critical welded joints or the availability of equipment if you didn't work for a huge company) or on an assembly line during WWII (where you simply couldn't take time to teach the workers to weld) there might have been a need for it. For a one off build in someone's garage that will take years to complete, there's a good chance that alternatives will make the build slower or might even introduce design/maintenance issues.

Ask yourself: Why didn't the alternative I am considering remain the standard way of doing this? You'll often find that it is often because it's like opting for a heart transplant when the practical solution (read as: simpler and less likely to end badly) is a valve replacement.

Sorry....I'm playing devil's advocate simply to amuse myself during a very boring meeting.

 

I'm sure that for many situations, coping each tube and then welding them is just fine. Whether it is the "best" method may depend on how the various factors are weighted.
Welded steel cabins have a good reputation for crash safety. I believe that is because they are strong (the tubes and the joints) and also that, when something yields it is the ductile nature of steel to continue to absorb significant energy. For a cabin (where we'd like to keep the structure and outside objects away from the occupants), the ductility may not be very useful--we'd trade it for higher strength prior to yield if we could get it (at the same weight, cost, construction effort, etc). Several posts in this thread have noted that AL can offer strengths higher than 4130 at the same weight. So, perhaps there's no need to go with 4130 at all, just build to the same strength (which may be well above flight loads) using aluminum. The same logic would apply to composites-- yes, some composite planes fly apart into a jumble of foam and glass on impact, but perhaps that's due to a design that accounted for flight loads and not impact loads. There are some well engineered high performance composite sailplanes with good crashworthiness, and some Formula 1 cars with composite crash protection that is tremendous.

 

Ahem. That was Winginit with one T in post 72, not Winginitt with two Ts from #126. Also not to be confused with ekimnierbo, with no Ts.

 

Ah, thanks. Well, that explains it. What next--"the second "t" is silent."?

 

For some reason you guys seem to dwell on the identity change, so I guess once and for all I'll explain it to you. My service provider sold out to another service provider.....twice. Each time I tried to contact HBA and change the provider but keep the same name with a different provider designation. Either HBA ignored my requests or they sent the reply to my now non-existant account....which I could no longer access. I tried numerous times to make contact with HBA on each of these ocassions and it was like throwing something into a black hole. The only way to get access again was to create a new account and it kept telling me my "name" was already taken. Did you conspiracy theorist not notice than whenever a new idenity appeared the old one was never heard from again ?
Nothing clandestine about it. Just could not access the account any longer. I did have a little fun when you guys first discovered the duplicity but couldn't get me to admit it. It was like Adam Schiff personified........CONSPIRACY CONSPIRACY CONSPIRACY ! Now you know all the dirty little details, that probably won't satisfy you either. Personally I just grin when I think how much some of you fret over me.


Winginitt: Why not just learn to Tig......its very enjoyable.

Vigilant1:Noted. Please see first post in thread. Welding is fine, wonderful, soothing, therapeutic, functional, etc. Many people find it so. This discussion is to cover alternatives.

Vigilant1 :But, if we want the advantages of a chrome moly tube fuselage but already know in our heart that we do not want to invest the scores of hours needed to master welding and we also don't want to fiddle around with the precise fitting of angled tubes, what are the alternatives? Are there alternatives, assuming we can live with the weight penalties, etc?

Winginitt: I suggested Tig welding because you apparently are either unaware of how little time it takes to learn to do a decent Tig weld vs endless hours trying to perfect a perfectly formed cosmetic bead every time. EAA offers a simple one weekend training class that gets most people near the point of producing consistant and strong welds. I have seen many o/a welds that I wouldn't have used on a go kart much less an airplane. You have a misconception of how difficult Tig is, and I merely suggested that you try it before discarding it. Don't be afraid to give it a try like so many people do. The idea that you have to be super gifted as a welder in order to learn Tig is all wrong.

Vigilant1:And, there are folks who believe that only welding is proper--BUT not TiG!! Egads! On an airplan?! Insufficient penetration, etc, etc. So even among the welding accolites, there are apparently sects and heretics.

Winginitt: This shows that you really have no understanding of weld processes. If you look at the majority of welds performed by amatuer airplane builders you will find ramapant overheating and extremly poorly crafted welds done by the less than gifted O/A welders. Many look like pidgeons did the work. If you ever even tried tig welding you would see the vast difference in ease of heat control compared to O/A. Someone who works in a job where they weld all the time with O/A can produce quality work.....but take a look at some of the welds in really old airplanes and you will find that not all of them are beautiful. As far as penetration goes,how do you weld thin tubing and not get penetration ?

Precise fitting of tubes.....don't you think all those tubes you want to insert precisely into each other are going to require some time and effort too ? Where do you think the precise stamped/pressed sheet metal fittings will come from ? Where do the gussets come from ? Where do any of the things you talk about using come from ? Are YOU going to make them ?
I can tell you the parts may assemble easily if made properly, but someone is going to have to do a ton of work designing dies and getting equipment to make the parts. Printing them ?
How strong are they going to be. Going to perform destructive testing ? You still have to learn how to design and how to print and purchase stuff to print with.
When done you most likely will increase the weight of the airplane significantly because all those gussets and fittings are going to weigh far more than a simple weld.
Cheapracer is experimenting with alternative methods. Ask him if everything has gone as smoothly as he had expected, or whether there have been unforseen problems along the way.

Vigilant1:
1) Fittings made of stamped/pressed sheet metal, with included gussets (i.e. riveted construction used by some British companies during WW-II). These handled some fairly sizeable loads, we're not talking about a pop-riveted hang glider fuselage)
2) Internal fittings (forged?), perhaps brazed or riveted into straight-cut tubing. With 3D printers; it would seem practical to rapidly make a mold of any needed angle/cluster. They wouldn't necessarily need to be "solid" parts of cylindrical cross-section, simple metal "webs" would be lighter and just as strong as the tubing, though they'd need enough area to mate with the tubing)
3) External fittings (forged), brazed or riveted onto straight-cut tubing (similar to the lugs found on some bicycle frames).
4) Other?

Winginitt: How much penetration do you think a brazed fitting has ?

Winginitt:
Actually this thread is so old I had forgotten that I had posted on it. You have said that you don't want to consider welding because it takes too long to learn. In the two years since you originated this thread you could easily have learned to weld proficiently. How much progress have you made on your alternative processes in that time ? Instead of being combative when someone (me) simply tries to help you, it might be wise to at least consider that they could have a point worth listening to. I spent years in manufacturing (hands on) and more years in inpection and project managing. Also spent time in a technical material group. I can tell you from first hand experience that designing and making all those alternative components is going to be far more involved than simple tube fitting and welding will be. Most likely it won't be as strong either. You know, I actually feel sorry for those people who grew up in an environment where they were never exposed to working on mechanical things or spent time trying to learn how to do many things them selves simply because they had no money. Learning to weld opens up new horizons and I've never heard anyone say they were sorry they had learned to weld. Many gave up because they bought cheap basically useless machines and got poor results, but no one who ever bought a decent machine and learned to weld has regretted it. If you look at the professional race car chassis made today, you will find all of them are Tig welded.....not O/A, not gusseted, and not brazed.

 

My viewpoint.

If someone wants to weld. Fine with me.

If someone wants T&G. Fine with me.

If someone wants composites. Fine with me.

If someone wants wood. Fine with me.

If someone wants sheet metal. Fine with me.

If someone wants bolted metal tubes. Fine with me.

If someone wants to start a thread on a particular method. Fine with me.

I don't see the point in bashing one method just because it is not your favorite. One reason I joined this forum was that it was the friendliest, with almost no bickering (at the time). What has happened to it?

[Edit] To appease cheapracer changed "aluminum" to "metal", which would included titanium, rubidium, copper, gallium, silicon....

 

I believe it's more associated with the type of craft it is more common to, eg; slower high wing craft.

and yes, aluminium is considerably stronger at the same weight.

At least a couple of major WW2 planes.

 

I note you left out titanium and stainless steel, your bias is showing!!

 

I agree with everything you said. I do think that whatever basis someone uses for their thread, it should contain accurate statements because the thread is not only for the benefit of the OP, but any builder who may read the thread worldwide. If an alternative method is viable, then thats a good thing. It doesn't mean that established methods therefore are bad. For example, to say that Tig welding thin wall tubing doesn't allow good penetration by the weld is totally inaccurate. I'm not saying that making stamped gussets and internal fittings won't work, but a builder must realize that while that may make assembly easier, it drastically increases the manufacturing time for the needed parts. Nothing personal in either of those statements, just something that anyone considering alternative methods needs to take a realistic look at.

 

If you started a thread that was specifically about screws, the usual suspects would jump on and tell you how they're superior craftsmen because they use nails. The truth is they probably just don't know to use a screw driver.

 

Ok, CR, I edited it to be more inclusive.

 

Hawker Hurricane steel riveted fuselage

 

Nice picture Dino ! I promise everyone I won't mention the dreaded "W" alternative, but lets look at the pictures of alternatives that have been presented on this thread. I'll start with Dinos first since it was the one I replied to.
1. First everyone should realize that just going to square tubing or aluminum tubing of any shape meets the requirement for "alternative" no matter what method of joining is employed.
2. Square tubing of any type will be easier to cut and match to other tubes than round tubes to round tubes.

The OP wants to avoid two things for sure. One I promised not to mention, and the other is cutting round tubes to fit other round tubes. If you examine (enlarge) the picture Dino furnished, you will notice that fishmouths have been cut even though brackets and riviting were used for assembly. Second, a close look will show that the brackets are not just flat surfaces with some bends but actually very special shapes that contour the round tubes and have been cadmium (?) plated. Professional high dollar factory stuff. Look at the lower inner bracket which designed to secure 3 intersecting tubes. Quality work to be sure. There are probably 30 brackets just on this one section of the fuselage. How much time and effort would it take to replicate this on a homebuilt? How many total brackets will need to be used for the whole airplane?




Looks nice sitting in the shop. My guess is there will be in the neighborhood of 100 brackets that will be employed to build this airplane. Since box tubing is being used to make for easy cutting and aligning, the rivets can't be bucked so pulled rivets will have to be used. I also wonder how tha outer surface of the airplane will look when covered? Will there be bulges in the fabric. Will it affect airflow over and around the fuselage? What about the tail surfaces? Will they have bulges ? How will the motor mount be built and attached....pulled rivits ?


How about the Boeing F4B ? Obviously professionally done. Look at the many shapes and sizes and even specially contoured brackets being utilized. Look at how many brackets are in this short section of the airplane. Would a homebuilder save himself some time by doing this alternate method of building?

My point here is that many things are doable in the realm of building an airplane in ones own shop, and a safe flying airplane can result from those efforts.....but often the effort expended may increase rather than reduce the time involved. You have realize that many of the common established methods may seem lengthy, but they became common for a reason.