[CMSRacing]

Anyone here play with Ti? I have a member at my shop (I work at a Makerspace) who wants to build a plane with a Ti tube frame. He is not really a welder. My first instinct is to tell him he is nuts and run far away from this project. The part of me that is interested in welding new materials that I may not have much opportunity for otherwise is an uncontrollable itch.

The guy has cash and the engineering background/experience, but only one life. I'm pushing for a radio controlled version to start.
Any airspace folks here? I'm running out reasons to tell him, and me, why this is such a bad idea.
Thanks

[ldbtx]

Excellent article on TIG welding Ti here: http://www.millerwelds.com/resources/ar ... um-welding

You'll find a name you recognize in the Acknowledgements.

I can't claim any aerospace engineering experience. Closest I've gotten is working as a QC inspector in the satellite program for one of the major aerospace companies back in the 70s. More recently (mid-90s) I worked for a couple years repairing and building ultralight aircraft. Aircraft work is a hell of a responsibility. It never left my mind that every action I took; every bolt I tightened, every wire I installed, every fuel line I hooked up -- had the potential to kill somebody if I didn't do it perfectly.

You say the member of your Makerspace "isn't really a welder". It sounds like (and I mean no offense, so please don't take any) that you're not an experienced Ti welder. If I'm wrong, please set me straight. So, the question that comes to my mind is, "Do you have enough faith in your Ti welds to rest easy knowing that he's up in the air in an airframe you welded?" If the honest answer is "No", then run away before the project starts. The very fact that you asked for opinions from this group tells me that you would not want to have to live with the knowledge that the aircraft you welded experienced an in-flight failure.

An RC model is an interesting idea and could have value. However, unless the model is designed and constructed to simulate the actual forces and loads (properly scaled) as the full size plane, it will prove nothing. Hopefully, your member's engineering knowledge can make that a reality if he chooses to proceed with the project.

I wish you all the best with the project if you choose to get involved with it, and I remember the words of a very wise man who said, "The key to success is knowing which jobs to walk away from".

LDB

[LtBadd]

Strictly speaking, welding Ti is not difficult (I have done a lot of Ti welding for GE and Pratt Whitney aircraft components). However the attention to cleanliness and proper gas shielding is key. Yet many paragraphs could be written about these few words. I won't try to go further then what has already been said.

[jumpinjackflash]

I would love to be able to afford and create such a beast... my FEA and modeling software wouldn't touch all that needs to be looked at on a complete airframe. Tough to beat 4130 for cost and proven track records....then came carbon composite....this is similar to what I am building.
http://www.cubcrafters.com/carboncubex

[CMSRacing]

Thanks for the feedback. The article is a good resource, so thanks ldbtx.

I probably should have started this post with 3 statements and a question.
1) I have never welded Ti.

2) I have designed and welded many role cages and other frames for that try to stay close to the ground at speed, but never a plane.

3) the guy behind this project has a number of planes under his design and building belt already. He is currently helping someone build a new set of wings for one seater. (I know so little about planes that is as technical a description I can give a about the type of plane they are working on now.

The main question is, how feasible is it to properly shield welds on something this big made of Ti. We can't exactly build a hazmat tent around it flooded with argon.
Would back purging sections with a trailing cup be sufficient?

My idea about the radio controlled plane was less a test of design and more a compromise on safety. As long as it does not crash into one of us, it won't be the end of the world if it does.

[blue_heeler1]

I work in the aerospace industry as a structures mechanic/welder. This biggest problem is I see with Ti tube frame is purging the inner side of the tubing. I've done alot of repairs on Ti tube mounts for auxiliary power units, and usually require a hole, or drilling a hole to back purge the tube.

Not trying to run you off anything, but if something does happen, and the FAA investigation traces it back to you, it won't be good. Honestly, if you don't have much experience in welding Ti, I'd run. Even though I've got experience in Ti, I'd run. Way too much liability, especially for dealing with the main structure.


TI is a different animal. Although as said before, it's not too bad to weld, but sheilding, cleaning, purging, and welding in a zero wind environment is paramount.

[LtBadd]

Thanks for the feedback. The article is a good resource, so thanks ldbtx.

I probably should have started this post with 3 statements and a question.
1) I have never welded Ti.

2) I have designed and welded many role cages and other frames for that try to stay close to the ground at speed, but never a plane.

3) the guy behind this project has a number of planes under his design and building belt already. He is currently helping someone build a new set of wings for one seater. (I know so little about planes that is as technical a description I can give a about the type of plane they are working on now.

The main question is, how feasible is it to properly shield welds on something this big made of Ti. We can't exactly build a hazmat tent around it flooded with argon.
Would back purging sections with a trailing cup be sufficient?

My idea about the radio controlled plane was less a test of design and more a compromise on safety. As long as it does not crash into one of us, it won't be the end of the world if it does.

Here is an article providing good fundamentals for Ti TIG welding
http://www.thefabricator.com/article/ar ... ium-tubing

For tubing you would need to back purge (purge the ID of the tube ) and have good shielding at the torch until the weld cools to 800°F
What size is the tube, and wall thickness for this job?

I imagine the designer wants to use Ti over chrome moly for weight reasons

[weldin mike 27]

If ti is important, and cash isn't, some bikes these days have ti tubes glued/bonded into aluminium connection pieces. This could be far more feasible than welding. And still fun, leaves room for multi facet machining of the connections.

[LtBadd]

We did a TI pipe job several years back and bought a large gas lens, they worked well. We got P/N 430311
http://www.pwt-online.com/products/prodGSD.htm

[Oscar]

The main question is, how feasible is it to properly shield welds on something this big made of Ti. We can't exactly build a hazmat tent around it flooded with argon.
Would back purging sections with a trailing cup be sufficient?

how can you back-purge internal tubing sections with an external trailing cup??

Me thinks you need to actually get your hands on titanium tubing to try it out just to see how sensitive it is. Titanium Joe sells a "welding starter kit" for $25 that consists of the following:

2pcs of 6al-4v (grade 5) Bar
2pcs of CP2 (Grade 2) Bar
2pcs of 3al-2.5v (Grade 9) Tubing
2pcs of CP2 (Grade 2) Tubing
2pcs of CP2 (Grade 2) Sheet
2pcs of 6al-4v (grade 5) Sheet
3pcs of 0.035"dia CP2 (grade 2) Weld Wire
3pcs of 0.035"dia 6al-4v (Grade 5) Weld Wire
3pcs of 0.062"Dia CP2 (Grade 2) Weld Wire
3pcs of 0.062"dia 6al-4v (grade 5) Weld Wire

[LtBadd]

The main question is, how feasible is it to properly shield welds on something this big made of Ti. We can't exactly build a hazmat tent around it flooded with argon.
Would back purging sections with a trailing cup be sufficient?

how can you back-purge internal tubing sections with an external trailing cup??

You can't, you have to have a separate purge line, so either a second argon bottle, or a dual flow meter off of one bottle

[CMSRacing]

how can you back-purge internal tubing sections with an external trailing cup??

Let me try that sentence again. Would purging the front with a trailing cup and regular torch flow and purge the back by filling the tubing with argon be sufficient.

As I count I would need 3 lines. One to the torch, one to the trailing cup, one to the tubing for internal purge.

Also, I imagine there will be some challenging connection points that may require some other planning. I'm thinking convergence of tubing similar to the seat post/down tube/chain stays on bicycles. I reference bicycles as I know some high-end are made out of Ti by small outfits. I imagine they have some good processes for shielding.

Thanks for the info on the Ti piece kit. I'll look into it.

[Oscar]

how can you back-purge internal tubing sections with an external trailing cup??

Let me try that sentence again. Would purging the front with a trailing cup and regular torch flow and purge the back by filling the tubing with argon be sufficient.

As I count I would need 3 lines. One to the torch, one to the trailing cup, one to the tubing for internal purge.

Also, I imagine there will be some challenging connection points that may require some other planning. I'm thinking convergence of tubing similar to the seat post/down tube/chain stays on bicycles. I reference bicycles as I know some high-end are made out of Ti by small outfits. I imagine they have some good processes for shielding.

Thanks for the info on the Ti piece kit. I'll look into it.

That's exactly what you need, 3 lines just as you mentioned. It is not just a sufficient condition, it is a necessary condition if you do not have any other kind of heat sinking going on around the weld joint. I just received my Ti welding starter kits + scrap tubing, can't wait to get started.

[Superiorwelding]

The main question is, how feasible is it to properly shield welds on something this big made of Ti. We can't exactly build a hazmat tent around it flooded with argon.
Would back purging sections with a trailing cup be sufficient?

how can you back-purge internal tubing sections with an external trailing cup??

Me thinks you need to actually get your hands on titanium tubing to try it out just to see how sensitive it is. Titanium Joe sells a "welding starter kit" for $25 that consists of the following:

2pcs of 6al-4v (grade 5) Bar
2pcs of CP2 (Grade 2) Bar
2pcs of 3al-2.5v (Grade 9) Tubing
2pcs of CP2 (Grade 2) Tubing
2pcs of CP2 (Grade 2) Sheet
2pcs of 6al-4v (grade 5) Sheet
3pcs of 0.035"dia CP2 (grade 2) Weld Wire
3pcs of 0.035"dia 6al-4v (Grade 5) Weld Wire
3pcs of 0.062"Dia CP2 (Grade 2) Weld Wire
3pcs of 0.062"dia 6al-4v (grade 5) Weld Wire

Oscar,
I am interested in this kit but didn't see it on his website. Where is it at Oscar.
-Jonathan

[Oscar]

The main question is, how feasible is it to properly shield welds on something this big made of Ti. We can't exactly build a hazmat tent around it flooded with argon.
Would back purging sections with a trailing cup be sufficient?

how can you back-purge internal tubing sections with an external trailing cup??

Me thinks you need to actually get your hands on titanium tubing to try it out just to see how sensitive it is. Titanium Joe sells a "welding starter kit" for $25 that consists of the following:

2pcs of 6al-4v (grade 5) Bar
2pcs of CP2 (Grade 2) Bar
2pcs of 3al-2.5v (Grade 9) Tubing
2pcs of CP2 (Grade 2) Tubing
2pcs of CP2 (Grade 2) Sheet
2pcs of 6al-4v (grade 5) Sheet
3pcs of 0.035"dia CP2 (grade 2) Weld Wire
3pcs of 0.035"dia 6al-4v (Grade 5) Weld Wire
3pcs of 0.062"Dia CP2 (Grade 2) Weld Wire
3pcs of 0.062"dia 6al-4v (grade 5) Weld Wire

Oscar,
I am interested in this kit but didn't see it on his website. Where is it at Oscar.
-Jonathan

You're correct, it is not on the website. I was offered that through email. You have to email them directly. Same to buy scrap tubing @ $20/lb, must email them.