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Attempt at aluminum head tube crack repair.

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Attempt at aluminum head tube crack repair.

Old 05-17-16, 10:37 AM
  #1  
kennj123
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Attempt at aluminum head tube crack repair.

bought a used bike ($125) that appeared to be in excellent shape. after about 30 miles noticed cracks in head tube. emailed seller and he said too bad. Rather than give up I decided to attempt repair with expoxy. I've done quite a few repairs both cosmetic and load bearing very successfully in past so i thought I'd give it a try. photo below:



I really just wanted to get it done. Expoxy was setting fast so I didn't get a chance to do a nice drop with the wire. next time I think i could do a much nicer job and kind of lace it up like a shoe string.

So any opinions? I figure about 50% will just be some variation of your going to die.
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Old 05-17-16, 10:53 AM
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The crack is at the bottom. What's with all the wire & goop all over the head tube ?
Looks ugly and ineffective.

If there was room at the bottom, maybe just a hose clamp wrapped around the crack would control it.

PS, You're going to die.
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Old 05-17-16, 11:11 AM
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Originally Posted by Homebrew01 View Post
The crack is at the bottom. What's with all the wire & goop all over the head tube ?
Looks ugly and ineffective.

If there was room at the bottom, maybe just a hose clamp wrapped around the crack would control it.

PS, You're going to die.
there was a crack coming from the top as well, it was smaller but its what made me think I might as well do a hail mary. The wire is wrapped very neatly around the top and bottom, probably about 4 or 5 loops side by side. There is a couple problems with hose clamps, biggest problem is they don't give dimensional stability. if the stresses on the tube are causing it to flex from a circle to an oval, clamp won't help.

Last edited by kennj123; 05-17-16 at 12:50 PM.
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Old 05-17-16, 12:26 PM
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It is fugly, and you've managed to ensure that you'll never be able to see those cracks growing, so death is in your future.

Did you drill the end of the cracks, to stop them from spreading? How did you get the wire wraps tight enough to provide any strength, at all?

I hope it works, but I think you may have wasted some epoxy. It's probably time to start shopping for a new frame, if not a new bike.
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Old 05-17-16, 12:39 PM
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I do not think that is going to work very well. Did you sand the paint underneath for a best bond? I would have done about 100 wraps to form just a band around just the top and the bottom only, then epoxy and maybe a layer of mold release membrane and a hose clamp tightened over the repair until it is cured to get as tight as possible and squeeze out air and maximize compression. I'd also use Kevlar thread instead of metal wire.

Last edited by dwmckee; 05-17-16 at 12:42 PM.
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Old 05-17-16, 12:40 PM
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Originally Posted by kevindsingleton View Post
It is fugly, and you've managed to ensure that you'll never be able to see those cracks growing, so death is in your future.

Did you drill the end of the cracks, to stop them from spreading? How did you get the wire wraps tight enough to provide any strength, at all?

I hope it works, but I think you may have wasted some epoxy. It's probably time to start shopping for a new frame, if not a new bike.
Thats about 50cents worth of epoxy and 2$ worth of wire. I get epoxy by the gallon and use it for quite a few things. Wire is tight but does not have to be too tight given the way its embedded in mat. And no, didn't drill the holes. thought about it, but I didn't know what was inside of of where I was drilling. I'm counting on the fact that the fix is so strong there is no way the crack will propagate. And the fuglyness is an anti-theft feature, so that makes it worth more.
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Old 05-17-16, 12:49 PM
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Originally Posted by dwmckee View Post
I do not think that is going to work very well. Did you sand the paint underneath for a best bond? I would have done about 100 wraps to form just a band around just the top and the bottom only, then epoxy and maybe a layer of mold release membrane and a hose clamp tightened over the repair until it is cured to get as tight as possible and squeeze out air and maximize compression.
Surface prep is excellent. all paint gone and surface very rough and cleaned with acetone. I did a quick experiment on a piece of electrical conduit and the adhesion of mat to pipe was excellent without compression. The first layer of epoxy was pure epoxy. very runny and thin but it had very low viscosity and could penetrate all the small nooks and crannies i put on the rough surface, Let it set for an hour and then applied the mat and then the wire. I do quite a bit of work with epoxy.
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Old 05-17-16, 12:49 PM
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Originally Posted by kennj123 View Post
So any opinions? I figure about 50% will just be some variation of your going to die.
So did you start this thread for entertainment value, or what? Because you've already done the deed ... how is someone else's opinion going to change anything?
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Old 05-17-16, 12:57 PM
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Originally Posted by techsensei View Post
So did you start this thread for entertainment value, or what? Because you've already done the deed ... how is someone else's opinion going to change anything?
Because if I just said what i was going to do it would be difficult to get people to understand what i was trying to do and opinions would be all over the place. Figured I would do it so i could show pictures and get more relevant feedback. If somebody did something similar they could post pictures. I have tools that I could cut off what I put on if somebody can show a superior solution.
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Old 05-17-16, 01:03 PM
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You stripped it down to bare metal, then decided to both A) not drill the cracks, thus ensuring that they'll continue to grow, and B) not take it to a welder to fix it the only right way?

I'm not sure comparing adhesion to galvanized steel conduit and bare aluminum is providing you with any worthwhile information.

Again, I hope it works out, but I'm pretty sure it's gonna asplode!

Good job on the anti-theft feature. That, you nailed!
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Old 05-17-16, 01:16 PM
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You're going to die, but it probably won't be on this bike.

You've probably bought yourself a little extra warning/indication time between when the bike will be dangerous to ride, and when it would actually have failed in a catastrophic fatality.

Although you could've done the same thing with hose clamps as mentioned earlier.

And you've kind of hidden the crack from view so your indication will be reduced.
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Old 05-17-16, 01:36 PM
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Muffler clamps are available in a variety of sizes.
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Old 05-17-16, 02:06 PM
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Originally Posted by flanso View Post
Muffler clamps are available in a variety of sizes.

... and so are coffins.
OP: you are definitely going to need one.
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Old 05-17-16, 02:11 PM
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Nothing terrible will happen. When the cracks get bigger, the headset cups will get loose, and the wiggling fork will let you know the party's over.
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Old 05-17-16, 02:35 PM
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Originally Posted by kennj123 View Post
I figure about 50% will just be some variation of your going to die.
Is there any reason you think you're not going to die...?
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Old 05-17-16, 02:47 PM
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Originally Posted by Homebrew01 View Post
Nothing terrible will happen. When the cracks get bigger, the headset cups will get loose, and the wiggling fork will let you know the party's over.
This. I personally would have used some fiberglass + resin to fix it after I wrapped it with whatever and drilled the ends of the cracks. Fiberglass is strong as crap and probably would have never have come loose.
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Old 05-17-16, 03:07 PM
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really hard to tell if this will work. Lot's of epoxy or resin in general does not guarantee strong. Thats why the bamboo frame guys will vacuum bag bag or or other wise compress the joint to get excess resing out. Same for squeeging out excess resin from surfboards.

Fiber glass matt is not terribly strong

the wire doesn't really appear to do anything

This would have been better (as best i can tell from the pics) if it was wrapped tightly with multiple layers of wet woven cloth, and excess resin removed.

will this hasten your untimely demise, probably not, will it increase your rep for sloppy work....yes
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Old 05-17-16, 03:29 PM
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Originally Posted by squirtdad View Post
really hard to tell if this will work. Lot's of epoxy or resin in general does not guarantee strong. Thats why the bamboo frame guys will vacuum bag bag or or other wise compress the joint to get excess resing out. Same for squeeging out excess resin from surfboards.

Fiber glass matt is not terribly strong

the wire doesn't really appear to do anything

This would have been better (as best i can tell from the pics) if it was wrapped tightly with multiple layers of wet woven cloth, and excess resin removed.

will this hasten your untimely demise, probably not, will it increase your rep for sloppy work....yes
Purpose of the large amount of resin is to make sure the wire is completely covered. I don't want it to rust, expand and break the fiberglass. The mat is not for strength, I just don't want to metal wire directly on the metal frame, the mat helps hold everything in place. As for slop factor, I don't do it for money, just for myself. If i did a pretty job all kinds of people will want me to do things for them for free. I'm just hoping to get 2years of relatively hard riding out of it. As for the purpose of the wire there to begin with its because epoxy has poor tensile properties compared to steel. for really tough jobs they put steel mesh in epoxy, but since i didn't need longitudinal strength, i figured wrapping steel around the pipe was good enough.

And what is all the concern about how the bike looks anyway. Do you guys pickup a lot of chicks with your really nice bikes?

PS. I'm getting more crap about the uglyness of the job than I expected. I thought the theme would be about all the different ways I was going to die. Anyway what is the point in worrying about how pretty it is when there is no consensus on what materials to use to make the repair. If my choice of material is flawed, bike will fail anyway and get tossed. ugly problem solved.

Last edited by kennj123; 05-17-16 at 03:59 PM.
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Old 05-17-16, 05:43 PM
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You haven't done anything that will slow the crack progression, you haven't done anything that will speed it up either. You've made an aesthetic change to the bike, that's about it.
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Old 05-17-16, 06:27 PM
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looks like a rice paper roll.. and after some "hard riding" like you say, will probably offer the same support as one. i would scrap it and start over.. you really do need to drill the cracks. and the muffler clamps are a great idea.
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Old 05-17-16, 06:35 PM
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Originally Posted by dwmckee View Post
I do not think that is going to work very well. Did you sand the paint underneath for a best bond? I would have done about 100 wraps to form just a band around just the top and the bottom only, then epoxy and maybe a layer of mold release membrane and a hose clamp tightened over the repair until it is cured to get as tight as possible and squeeze out air and maximize compression. I'd also use Kevlar thread instead of metal wire.
I looked for Kevlar thread or any other kind at the boat shop where I get my epoxy supplies and they didn't have anything, just mat. I never bothered with kevlar mat because you need special scissors to cut it and their are other hassles. But the thread is interesting. Quite a few places are selling it on Ebay. Will any of the stranded versions work? It looks like they have a monofiliment for fishing. Weight test is only 60lbs, but it could be a lot thinner that the alternatives at the same strength.
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Old 05-17-16, 06:37 PM
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Originally Posted by Homebrew01 View Post
Nothing terrible will happen. When the cracks get bigger, the headset cups will get loose, and the wiggling fork will let you know the party's over.
Good point... I just hope that you notice it when you hear the "Large" lady singing.....epoxy is not where the strength is it is in the matt.
Good luck!
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Old 05-17-16, 06:38 PM
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Originally Posted by d4vide View Post
looks like a rice paper roll.. and after some "hard riding" like you say, will probably offer the same support as one. i would scrap it and start over.. you really do need to drill the cracks. and the muffler clamps are a great idea.
Lots of naysayers here. I did an experiment on a piece electrical conduit and tried to bend it and the strength was excellent.
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Old 05-17-16, 07:41 PM
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Well when you decide a path that 100+ years of industrial experience hasn't found to be the best solution what do you expect? Andy
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Old 05-17-16, 07:51 PM
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Originally Posted by kennj123 View Post
... I get epoxy by the gallon and use it for quite a few things...
there is the thread.
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