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Old 09-23-2020, 01:39 PM   #1
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Default Can I braze a roll cage?

I'm thinking of fabbing up a roll cage for my prerunner project, problem is, can I braze up a cage with a torch and some silver solder without it falling apart on the first impact?

I don't have a welder and don't want to spend the time and money trying to weld.
This is for an 20ish mph build, not a crawler, so I'm worried about the structural integrity of things.

If not, I might just make a plastic roll cage.
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Old 09-23-2020, 01:49 PM   #2
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Default Re: Can I braze a roll cage?

For this purpose, a properly brazed or silver soldered joint will be as strong as a welded joint. If it falls apart while driving, then it is a problem with the person doing the brazing.
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Old 09-23-2020, 01:55 PM   #3
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Default Re: Can I braze a roll cage?

I have a 1/6th scale Willys that weighs in at 11lbs that has had a couple of unfortunate rolls. The cage is well triangulated and brazed 3/16" brake tubing that seems to be as straight as the day I finished building it. Maybe that's not saying much. haha

Clean the coating off the tubing good..
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Old 09-23-2020, 02:26 PM   #4
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Default Re: Can I braze a roll cage?

Quote:
Originally Posted by svt923 View Post
For this purpose, a properly brazed or silver soldered joint will be as strong as a welded joint. If it falls apart while driving, then it is a problem with the person doing the brazing.
Yep, that'll probably be me.
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Old 09-23-2020, 03:05 PM   #5
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Default Re: Can I braze a roll cage?

Braze away. Go with tubing, 3/16, noting that you need to cope the tubing that saddles one to another. Be sure to triangulate it properly, and if you can, put crown (rolled into the tubing) if it is applicable. Its harder to bend a formed piece in a crash than straight tube. Practice makes perfect, welcome to scratch building.
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Old 09-23-2020, 04:20 PM   #6
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Default Re: Can I braze a roll cage?

From my experience, the silver solder joints are plenty strong, but steel tube will definitely bend from a good tumble down a rock face. The flexblility of plastic seems to make it a more durable material. But hey, those bends and dings provide character
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Old 09-23-2020, 05:41 PM   #7
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Default Re: Can I braze a roll cage?


Absolutely you can. I did this one earlier this year. The hardest part was getting the bends in the correct spots to match the outline of the proline hilux body. I used 3/16 od brake line, safety sliv 56 solder and stay silv flux. The tabs are from rc fab tabs and definitely made the job easier. I used map gas and practiced on some scrap pieces until I got the hang of it. Watch the scale builders guild video on YouTube and you will get the idea real quick. It was honestly a lot easier than I expected given it was my first attempt.


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Old 11-20-2020, 06:41 PM   #8
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Default Re: Can I braze a roll cage?

I'm working on a tube buggy at the moment and I've got multiple joints that are brazed in close proximity. As I'm brazing one joint the other will melt and things start to move. Ideally I would jig everything up and braze all the joints at once but I dont actually have a good way of doing so. What I'm considering is trying to add some tiny Mig tack welds in order to hold things together before I braze the next joint thats near by.

I know these welds will not be strong so I can accept that, I just need them to prevent things from moving as I braze.

Anyway has anyone attempted something like this?

I'll test this on some scraps first and if that fails I guess I'll just need to fab up a jig of sorts.

I found this article when searching for info https://weldingtroop.com/can-you-weld-over-a-braze/

it lays out why this is a bad idea for strength, but I'm thinking my application is a tiny bit different as I only intend to tack a tiny portion and finish it off by brazing it. Plus these are just tiny trucks not structural repairs.

Last edited by HumboldtEF; 11-20-2020 at 06:48 PM.
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Old 11-21-2020, 06:56 AM   #9
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Default Re: Can I braze a roll cage?

I use some small neo magnets when I'm trying to keep one piece in place while brazing another close by. You could possibly try to braze from another direction that helps direct the "stray" heat over away from the piece you are trying to keep stationary.
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Old 11-21-2020, 08:36 AM   #10
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Default Re: Can I braze a roll cage?

You could also try a wet rag wrapped around the area you want to protect as a heat sink.
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Old 11-21-2020, 12:50 PM   #11
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Default Re: Can I braze a roll cage?

Cool thanks for the tips guys.

I actually grabbed a bunch of welders magnets for the project forgetting that I got stainless steel which isn't magnetic, DOH!
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Old 11-21-2020, 04:44 PM   #12
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Default Re: Can I braze a roll cage?

Just to update, I did a bit of testing today.

Mig before brazing is fine (as expected)



Mig after brazing is definitely a bit contaminated





As I started up the tack on the brazed joint it sputtered like I was welding aluminum for a second, I stopped and restarted the tack and it went back to normal.
It did melt the surrounding brazing filler which pooled up below the weld a bit but with the plan being to braze afterward I should be able to clean it back up and redistribute it.

I'll say this is acceptable to me on the 2-4 joints that may require this. From here on out I'll just plan to first tack with the mig on joints that will end up with other close by joints.

Grinding away all of the brazing filler first is also helpful as the only issue is the filler itself.

Side note, I found the stainless was easy to tack. I know its hard to work with but that probably applies more to welding up an exhaust on a 1:1 where you're welding on the flat of the tube instead of the gooch.

Last edited by HumboldtEF; 11-21-2020 at 04:53 PM.
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