Fixable? Weld or Braze?

[NOVA87Wrangler]

So the frame broke on my bike. Right about the weld. It's 6061 heat treated aluminum. There's a warranty on the frame so they are going to ship me a new one, but it's been a couple weeks and they still haven't shipped it yet. I use this bike to commute to/from work everyday. So I was thinking about trying to *fix* it for the interim. I'm got decent soldering experience and I just got a small stick welder for , but I've never welded aluminum. I've watched some videos online showing how to stick weld aluminum but I'm hesitant to try on this partially because of how thin the material is. So I was considering brazing it because it seems it'd be better to fill the gaps. I've got a propane torch but could be convinced to buy oxy-acetylene if needed. I guess I could take it to someone to get it done as well. Any suggestions/referrals for someone in the NOVA area?

https://i.imgur.com/wKq9ZJv.jpg

https://i.imgur.com/Eged6Ts.jpg

 

[joe49]

Not a place to learn. Best you find a pro welder for your repair to tig weld it. A sleeve repair will go along way towards it being sound.

 

[ng8264723]

Sleeve it for now.. Cutting a piece of tubing in half and overlap it. That is as long as it is not at the joint...

 

[NOVA87Wrangler]

That's what I was afraid of, it's too close to the joint to sleeve it unfortunately. I'll have to call around and see if I can find a fab shop to weld it for me . . .

 

[Mike.ASC]

I tig weld aluminum almost every day, where is the crack located? Can you post a picture...?

 

[Moosefire66]

Needs to be tig welded, not brazed. Best done by a professional as aluminum is very soft and easy to blow thru. Maybe even add a corner gusset as well since it can't be sleeved

Sent from my SAMSUNG-SM-G890A using Tapatalk

 

[brianh]

Another alternative is a carbon fiber fix, I have made a few bike frames out of aluminums and carbon fiber lugs its a simple process wet down the carbon with epoxy and wrap with electrical tape. The frame pictured while not pretty is now 13 years old without an issue.

 

[MShaw]

Just remember that 6061-t6 is a heat treated alloy. The weld area will be annealed and much weaker. The last place I worked did a tremendous amount of aluminum weldments. Anything in 6061-t6 was always heat treated after welding unless it was a very low stress part.

 

[ez-duzit]

You're not going to stick weld aluminum.

Tig welding is appropriate. Mig is a possibility. But you will lose the heat treat.

Wait for the new frame.

 

[Fcvapor05]

I would highly recommend that you do not weld your frame.

Where is the crack??

You will not be able to just drop weld metal on top to fill the crack- this will take a lot of prep, grinding the crack completely out, which will leave a gap. A skilled welder will be able to fill this gap, but bicycle frame tubing is thin. It will take skill.

When the joint it welded, the weld itself as well as both tubes the weld touches, will only be about 40% as strong as they were originally. Welding will remove the heat treat. Depending on which joint is cracked, this will result in a frame that is not safe to ride.

 

[theoldwizard1]

Not a place to learn. Best you find a pro welder for your repair to tig weld it. A sleeve repair will go along way towards it being sound.

AGREE !! And it better be a shop that has EXPERIENCE welding aluminum !

 

[AZ Pete]

AGREE !! And it better be a shop that has EXPERIENCE welding aluminum !

Imwould get a seat post that extends below the crack, then do the carbon fiber wrap and call it a day. The seat post should minimize flex, and the carbon fiber should strengthen the tube.


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[rlitman]

Just remember that 6061-t6 is a heat treated alloy. The weld area will be annealed and much weaker. The last place I worked did a tremendous amount of aluminum weldments. Anything in 6061-t6 was always heat treated after welding unless it was a very low stress part.

That’s why very few bike frames use 6061. 7005 tubing can be welded and keep most of its strength. 6061 will be fully annealed around that weld, and you’d need to re heat treat the whole frame.

The carbon fiber wrap idea has some merit.

 

[NOVA87Wrangler]

Imwould get a seat post that extends below the crack, then do the carbon fiber wrap and call it a day. The seat post should minimize flex, and the carbon fiber should strengthen the tube.


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Carbon Fiber wrap is an interesting idea. Never done that before, but should be in the realm of my skillset. The seat post already extends below the crack, I've still been riding it.

For those chiming in about the weakened state, that's what I was afraid of, but given the non-structural nature of the part, I'm not too concerned. If the crack was probably anywhere else, I wouldn't still be riding it and wouldn't even consider a self-fix.

Mike.ASC: I'm in northern Virginia, just outside the beltway and bike into downtown DC every day.

 

[Mike.ASC]

Carbon Fiber wrap is an interesting idea. Never done that before, but should be in the realm of my skillset. The seat post already extends below the crack, I've still been riding it.

For those chiming in about the weakened state, that's what I was afraid of, but given the non-structural nature of the part, I'm not too concerned. If the crack was probably anywhere else, I wouldn't still be riding it and wouldn't even consider a self-fix.

Mike.ASC: I'm in northern Virginia, just outside the beltway and bike into downtown DC every day.

I am only about 30 minutes south of the beltway in southern md.

 

[ez-duzit]

Unsubscribed.

 

[bubinga]

Anyone else getting an error from the image links?
You know, pictures may be hosted here at garage Journal.
Then they get hosted here, and stay here, for future research.
Plus, No Errors!
I just don't understand why people just don't upload pictures here?

 

[rlitman]

Carbon Fiber wrap is an interesting idea. Never done that before, but should be in the realm of my skillset. The seat post already extends below the crack, I've still been riding it.

For those chiming in about the weakened state, that's what I was afraid of, but given the non-structural nature of the part, I'm not too concerned. If the crack was probably anywhere else, I wouldn't still be riding it and wouldn't even consider a self-fix...

I've seen more than my fair share of cracked and broken frames, but don't recall seeing a crack there. Usually it is by the headset or chainstay.

That part is reinforced by the seatpost to a degree. You don't say what size seatpost you have, but one option may be to sleeve it from the inside, and then use a smaller seatpost within that.

If you sleeve it, you could either cut down the broken part, and put a seatpost clamp where the sleeve sticks out, OR you could find yourself a wedge clamping seatpost that grabs from the inside. And actually, if you can find that in the diameter for your frame, you might be able to use a long one of those and forget the repair entirely.

FYI, that frame was TIG welded, but as I pointed out above, welding is not an option for a repair.

If you do go the carbon fiber reinforcement route, it is important to make sure that more fibers run perpendicular to the crack. Wrapping strands around and around in the direction of the crack will add no significant strength.

 

[rlitman]

Anyone else getting an error from the image links?
You know, pictures may be hosted here at garage Journal.
Then they get hosted here, and stay here, for future research.
Plus, No Errors!
I just don't understand why people just don't upload pictures here?

As you wish.

 

[MoonRise]

DIY weld or braze repair on a cracked 6061 bicycle frame ? Forget about it.

Stick weld a thin aluminum bike frame? Ha! Nope.

And brazing some 6061 aluminum? Theoretically sometimes possible, but not really in the real world. Not counting the zinc alumalloy stuff, which works within its limits. But doing a structural repair on an aluminum bicycle frame is way past those limits IMNSHO.

That crack IS a structural crack.

Get on the frame company to send you the replacement frame.

Unless EVERYTHING is done just right with an aluminum weld, it WILL fail.

Leave a weld bead crater, it will fail.

Wrong weld filler, it will fail.

Trying to weld the 'wrong' aluminum alloy (like most of the 7xxx or 2xxx alloys), it will fail.

And here's the other thing about aluminum when it is used structurally, not even counting the welding of aluminum aspect. If the aluminum structure has a varying load on it, especially one that has both tension and compression stresses, the aluminum WILL fail from "fatigue" eventually. No matter what, no matter how well it was made or taken care of, the aluminum WILL fail. Because aluminum does not have a "fatigue limit", unlike steel.

That cracked frame is done. IMNSHO.

Any repair attempt would be just that. An 'attempt'.

 

[rlitman]

Sorry Moonrise, I usually agree much more with you, and you do raise some good points, but you also missed the mark on some issues today.

I've built and repaired bicycle frames. That break is only structural in the current use, but as I pointed out above, with a different style of seatpost, the break becomes cosmetic.

Also, the fatigue limit point is completely moot. There should never be a fatigue failure in a 6061 bicycle frame. Within its elastic limits 6061 can withstand 10^8 and many orders of magnitude greater fatigue cycles. Now the same cannot be said for all aluminum alloys, but blaming fatigue here is a red herring.

 

[MoonRise]

re: fatigue

I didn't say fatigue was THE reason for that seatpost failure. (although it might be. I can't see the crack in enough detail to tell if there are "beach marks" or not.)

The mention of fatigue and aluminum was meant along the lines of 'aluminum is different than steel'. In multiple ways, including some that folks sometimes aren't even aware of.

But a cracked aluminum bike frame, right were the seat tube is welded to the top tube just raises all sorts of warnings to me.

Was there a weld bead crater acting as a crack initiation site, or a 'bad' weld in some other way (porosity, lack of fusion, a start/stop that was not adequately tied in, poor weld prep, bad fit-up, a tack weld that was not feathered out or not fully fused, excessive weld bead reinforcement that 'rolled over' the surface or just set up a stress riser at the weld toe, or any of 30 other things that could have caused the failure. )

And I personally get the heebie-jeebies about putting my **** over a broken metal spear. No thanks.

But to me, from two pictures on the net, that crack is just worrysome for multiple reasons.

So much so that IMNSHO, I say just replace the frame.

(someone who really knows what they are doing and can evaluate and diagnose both the root cause of the failure and a possible repair -might- be able to fix the frame. But a man's got to know his limits.)

 

[rlitman]

Well, we're in agreement, in so much as the fact that that WELD is beyond DIY repair (it would only be possible if you could strip and heat-treat the entire frame post welding, which would be more effort and cost than buying a new frame). And that's is indeed because of the fact that it is 6061 aluminum, and not steel. But condemning the frame because of this potentially cosmetic break is like condemning a car for torn leather upholstery.

 

[bubinga]

As you wish.

Thank You rlitman.
Really do think it is A good idea for folks to just upload, host here.
maybe I'm missing something.

BTY, You are one of the Helpful and knowledgeable folks on this group.

 

[rlitman]

Thank You rlitman.
Really do think it is A good idea for folks to just upload, host here.
maybe I'm missing something.

BTY, You are one of the Helpful and knowledgeable folks on this group.

Well, there are good arguments for and against. Hosting here costs GJ money in the long run, as it takes up space and bandwidth. I know that because of that, in the past it was discouraged here, but I don't believe it is any more, now that uploaded images are automatically compressed and resized. But that's something best answered by Ryan.

On the pro side, hosting the image inline with the thread means they will be preserved together. I've seen lots of good build threads lose great wealths of information when their externally hosted images went dark, either through an act of the hosting service, OR an when the poster decides they want to pick up their stuff and go home.

 

[bubinga]

Well, there are good arguments for and against. Hosting here costs GJ money in the long run, as it takes up space and bandwidth. I know that because of that, in the past it was discouraged here, but I don't believe it is any more, now that uploaded images are automatically compressed and resized. But that's something best answered by Ryan.

Oh!!, I was not aware Of That..... Makes sense though.

On the pro side, hosting the image inline with the thread means they will be preserved together. I've seen lots of good build threads lose great wealth's of information when their externally hosted images went dark, either through an act of the hosting service, (PHOTO BUCKET...).......LOL, OR an when the poster decides they want to pick up their stuff and go home.

My Point Exactly!!!
If researching, Makes the post close to useless!!!.....