Hello, I saw some small tubing by the plasma cutter labeled “for class/training use”. Is it possible for me to buy some to use for my project?
Thank you
Steve
We really aren’t setup for selling. The stuff in the metal rack is for classes and makerspace projects, when we have unwanted leftovers we put it in the scrap bin and its free to take.
I just bought
.75 x.035 4130, $5/ft tubing and
.875x.035 1020, $1.50/ft
For the coffin race project. No scrap on that yet.
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Did you get this locally? I couldn’t even find .035 mild steel on the website.
Can I get a link to the discord thread for the coffin race?
This is the least terrible price I could find (online) for 4130 btw:
I called a bunch of steel places in town and finally found 4130 at Jorgensen steel in west dallas. And they also had the .035 1020 DOM steel which was much cheaper. Flexing the two side by side they don’t feel that different, but you can heat treat the 4130, which we are not going to do with the coffin racer. So I went with cheaper 1020 DOM for the coffin racer and got one stick of 4130 to see if I had any regrets on getting mostly 1020. I also talked to a guy at an experimental aircraft group at Addison airport, he sent me to Kipp Aero, who mainly restores old British roadsters, but also makes wooden kit planes, but they don’t sell 4130 and only had a few pieces of around 3/8" 4130 leftover from a museum replica they made.
You have to buy full 20-24’ pieces at Jorgensen. Their cutting charge was like $10/piece but I asked nicely and they let me cut it with a cordless cutoff grinder in their loading area.
The Makerspace has a cash/Credit card account now at Jorgensen.
Has a location in Ft. Worth but they dont carry steel yet, they told me they are moving in about a year and should stock 4130 after that. They will cut to length, so would be a good resource in the future if you needed short lengths of 4130.
And this post might seem long but its nothing compared to the time I spent trying to find suitable thinwall tubing and filler metal. Lots of time on bike framebuilding forums, welding forums, and some aircraft forums.
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Aircraft spruce is a great resource for a lot of cool stuff
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Thanks for the source. In truss structures, the limitation is Euler buckling, which doesn’t improve if you switch to 4130, because it’s about the same stiffness even if it’s a lot stronger. If one element in the truss exceeds the buckling limit, it’s going to cause a failure, so you still need cross members at the same spacing, so you end up with a similar truss. Also, in practice, most failures occur in the heat-affected zone.
The time I spend welding is miniscule compared to the time I spend designing and making the jigs. If the jigs are good, it’s really hard for me to mess things up. Conversely, it takes a skilled welder to ad-lib things. With mild steel I can end up with a structure that’s lighter and stronger than almost any other method, way easier to do QA than composites, more heat resistant than composites, and I won’t feel that bad if I have to start over.
I haven’t actually welded any lightweight trusses, just boring stuff like tables and shelves. I did weld this one control assembly out of 4130 tube and plate, but it’s way too thick and heavy. It was mostly for practice and for experiment with the phenolic hardpoint.
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We are still learning to fillet braze, it is way more forgiving than welding thin walls. I’ll have my brazing torch set up sat afternoon and sunday night, come give it a try after about 1 sat or after 6pm sun.
Tonight I played with Oxy Propane, The flame was a little harder to light than acetylene and I had to use a larger tip but it seemed to work fine.
Lets talk about trusses,