Aluminum Welding

[Mike Jackson]

I am soliciting opinions/facts regarding aluminum welding. I'm installing a new fiberglass pod on my Air Command and have been imagineering mounting methods.

Another gyro friend of mine suggested an aluminum welded structure. Imagine a classroom lecturn. Slightly angled AL top, for mounting the pod, welded to a verticle 1x2 AL piece. "Floor mount" is AL welded to the verticle and bolted to airframe. He does a great job Tig welding aluminum but I'm concerned about vibration, both high and low freq, possibly cracking welds. With no other supporting angles I'm concerned about a "single point failure" while airborne.

There are certainly many material and structure options, but this one is very light, clean and relatively easy to manufacture.

Any thoughts?

Thanks,

Mike

[skyguynca]

I built a complete Biplane from welded aluminum 6061-T6 1 inch, 7/8, 3/4 and 1/2 tubing with .058 wall. I used to demonstrait its strength by standing on the aft section between the tail and cockpit and bounce up and down on it with my 200lbs and it held fine. I flew it for a little bit before someone bought it but it was a nice little plane. There are alot of things to learn about welding aluminum and there are a ton of myths that people are going to tell you. Make sure you talk to the experts who do it for a living to get your questions answered........since I am certainly no expert just have a little experience with it I will let someone else handle it.

[Bob]

If your worried about structural failure by welding a bar to a tube how about wrap the bar all the way arround the tube and then weld it ?
... or spred out the welded area with a triangle shaped base to the bar so the welded area has alot more surface area ...
keep workin at it you'll figure it out ! where there's a will there is a way !

Bob....

P.S. I do all my alum welding with alum stick rod ... I am NO expert ! but they don't brake if ya pre-heat the things I found !

[Mike Jackson]

David & Bob,

Thanks for your inputs!

Mike

[Jim]

If your friend is an expert in aluminum welding, you will have little problem. Just be very careful what kind of alloys you are using. Some are weldable, others not.

Also make very sure about the filler material. It must be the same as the base material. I have seen welds disintegrating after a while because the alloys were not compatible. This even happened with very experienced, professional welders.

I have welded things like fuel tanks from aluminum, with TIG, but because of my fear for the integrity of aluminum welds, I have always refrained from welding structural parts. That doesn’t say that it cannot be done!

Jim

[Doug Riley]

The problem with welding heat-treated material like 6061-T6 is that the welding heat takes out the heat-treatment of the parts being welded. Maybe the material ages back to T6 after it cools and maybe it doesn't -- if not, you've got soft spots at/near the joints. Proper T6 treatment is a controlled process that involves holding the material at elevated temps for hours.

Smaller 6061 parts can be annealed and re-heat-treated back to T6 if the welding rod is 6061 and a well-regulated oven is handy. OTOH, big welded 6061 objects like the Honeybee frame (the biplane, not the gyro of the same name) don't fit in most ovens!

[skyguynca]

One thing I learned from the guy who taught me to tig weld aluminum, T6 returns to t3 or t4 in a few weeks which is about 88000 kpsi which is more than strong enough for anything we are doing, but if you heat the aluminum too much it is destroyed. You can not reheat treat items yourself. For aluminum aging it is done in liquid vats that bring it up to temp and hold it there to age the material, the oven myth is for only small parts. There is a company who makes VW redrives and props, well known for their quality, all of their test aircraft are tig'd 6061t6 airframes they welded themselves and using alot of their advise (which these guys are great!!!!!!!!!!!!!!!) I welded my biplane together and it performs just as they said it would, the joints are flawless and strong. Like my advice earlier, do what I did, train with someone who does it for a living (welding aluminum) and they won't steer you wrong.