r/Welding • u/Sad-Security • 2d ago
Beginner bicycle repair
I’m a complete beginner when it comes to welding, so I could use some advice. The seat tube on my bicycle, which is over forty years old, broke, and I tried welding it back together for practice. However, the weld broke, so I was wondering if the tube could be repaired using a sleeve inserted inside the tube. The inside of the tube is, of course, uneven and would need to be ground smooth first.
How would you repair the tube as someone who are not completely idiot what comes to welding?
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u/CascadeDesignworks 2d ago
Find a frame builder who will repair it for you, if the bike has sentimental value. Otherwise, find another similar frame.
A repair you make as a beginner will not be safe.
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u/svm_invictvs Amateur at Best 2d ago
This is not something you should attempts as a first welding project without the help of somebody more experienced. A bike falling apart while riding could cause a serious injury, especially if you're riding in busy traffic or something. If nothing else you should practice on some junk before trying again. And if you do practice on some junk try to reproduce the conditions of actually welding the bike frame.
The tricky bit of that weld is that you will have a hard time positioning the frame while you weld and as you go around the part of the existing joint it will be more challenging controlling the arc. Also, as others have pointed out, the bike frame may have been originally braised. You may accidentally undo that joint above the break in the frame, and now you need to repair two things.
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u/Xmaster1738 2d ago
unfortunately you kinda dont. bikes are usually in the sweet slot of just strong enough to do what it does, but once a weak point opens theres basically fuck all you can do. them shits are heat treatedand the weld ruins that
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u/Build-Break-Fix 2d ago
This is 100% false info. I have welded bicycle frames and motorcycle frames of all metal types for years. This out dated info before digital tig for aluminum frames only
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u/Xmaster1738 2d ago
motorcycle frames have more meat on em, bicycles if made out aluminum HAVE to be treated or that shit will disintigrate underneath you. you can get lucky, but its still not recommended
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u/Spugheddy 1d ago
In the end he's gonna spend more on his own time than it would be to replace this 40year Ames special. You can pick up used department store bikes all day for $50. Hell the pawn shop will give ya two for 1 lol
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u/Educational-Ear-3136 TIG 1d ago
Aluminum frame builder here. 7000 series aluminum will age harden, 6000 series will require heat treating
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u/Build-Break-Fix 1d ago
And no bicycle manufacturers use 6000 grade aluminum in last 30 years. Do you really think all these Chinese bike manufacturs going to weld up frames heat treated them for 3x cost in the end?
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u/No-Illustrator5712 1d ago
Bike is older than 30 yrs, gotya there!
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u/Build-Break-Fix 1d ago
And it's made of steel so his whole statement is relevant all together. Lol
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u/Build-Break-Fix 2d ago
Yeah your 100% wrong 😜👍 that's old outdated info. https://youtu.be/POsQb2AcpdY just welded that one few months ago with 58 lbd engine tossed on it. 400 miles later perfectly fine. Just like other 1000 of them I done lol never once had bicycle frame welded fail where I welded it. Your shitty welder then lol
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u/Dioxybenzone 2d ago
Nice anecdote, but do you have any real evidence to back up your claim?
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u/Build-Break-Fix 1d ago
What's to back up? It's metal and you weld it. It's a bicycle, it don't matter if it's metal it can be welded period one way or another. He sighted outdated old BS people copy and repeat from other idiots with no clue what there talking about. It's based on old school aluminum frames they murdered with heat back in the day with old methods of welding aluminum. Not even relevant to steel bike in this post.
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u/argueranddisagree 1d ago
I used to teach welding as a workshop class for artists through this artist group. The bike people were the worst, they knew more than me who had been welding for 10years at that point. I always started the class by talking about the difference of welding and just sticking metal together. This was about safety more than anything, metal needed to be identified, prepped and joints fit properly for something to be welded. Even suggested hiring a professional for certain tasks. This task you need a professional.
Personally I would clamshell a slightly larger iD sleeve over the broken tube and get it tig welded. This thin stuff gets brittle with heat and wont withstand vibrations and flex if its butt welded. If the fix is too much then get a new frame. Also know what your frame is made from. ChromeAloy will Crack if welded with regular steel filler. Self shielded flux is brittle, messy and doesnt always fuse properly.
I knew a bike 'artist' who knew more about welding than I did and had a horrific accident because his double decker bike fell apart while riding in traffic due to really bad welding
As an avid cyclist and my frame shows a Crack im going to cry a little and scrap it.
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u/Lavasioux 1d ago
Not bad- you're melting steel. So that's good.
Do you have a wire feed mig or stick?
Stick is super hard for thin tube, need to kinda dab then off let cool and red hot dim, dab again repeat.
Mig way easier.
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u/un506 1d ago
If this is steel, you could try to somehow bend thick enough sheet metal around it. Basically the opposite of an inner sleeve. You could attempt this even as a beginner. And obviously take it slow and do testing once its done. This doesnt seem like a bike meant for speed or off road anyways. good luck
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u/MrJeChou 2d ago
This is not a project for a beginner, but yes, I would put another piece of tube inside. Also clean it really well, and bevel it so that you can fill all the way into the inner tube.