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Attempt at aluminum head tube crack repair.

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Attempt at aluminum head tube crack repair.

Old 05-19-16, 08:37 AM
  #101  
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Originally Posted by kennj123
Anytime concrete is used without something directly underneath it, its in tension. I've been in Italy and Brazil and its amazing what they are building out of nothing but rebar and concrete. Actually a better example of my case would be wire mesh in concrete, used in concrete floor so it won't crack. thats the same situation with my stranded wire around the head tube, its just i didn't need reinforcement lenghtwise.
Concrete as a material does not withstand significant tension. The rebar in the structure bears the tension and the concrete material around it just serves to keep the rebar from shifting out of optimal load bearing position (actually, concrete compression occurs between rebar members to help keep the rebar in place and bear tension). A concrete and rebar system can create a structural member that bears tension and compression.

Now back to bikes and epoxy...
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Old 05-19-16, 08:45 AM
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Originally Posted by cobba
Perhaps the logic of a cart-boy engineer stepping a bit beyond the limits of his training? Using familiar old tools and materials in novel ways to solve new problems... Maybe several wraps of wire in a shoelace pattern under that plastic would provide some additional structural integrity...
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Old 05-19-16, 09:02 AM
  #103  
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Originally Posted by dwmckee
the concrete material around it just serves to keep the rebar from shifting out of optimal load bearing position
I like the way you use the word 'just' there. the use of concrete to do the job of keeping the rebar in place is a pretty critical part of that building system. What alternate cost effective material could be used?
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Old 05-19-16, 09:05 AM
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Originally Posted by bigbenaugust

Did OP die in the last hour and a half?
...no.

Originally Posted by kennj123
I like the way you use the word 'just' there. the use of concrete to do the job of keeping the rebar in place is a pretty critical part of that building system. What alternate cost effective material could be used?
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Old 05-19-16, 09:09 AM
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Originally Posted by kennj123
If its not prior art is doesn't belong here.
...rarely, but nevertheless occasionally, some innovative techniques for repair and/or maintenance are shared here that are quite useful. Maybe next time.
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Old 05-19-16, 09:19 AM
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We already have crack initiation and the engineering method that you employed is to inhibit further propagation of the crack to extend the life of the part. I'm not an engineer but my guess is that if I was and was hired as an expert witness my testimony would be something like, the integrity of the part was compromised by the initial crack and although the fix allowed the part to function under normal loads, given the high load condition that was experienced at end of the part's fatigue life, the final phase was instantaneous and without warning, leading to the death of the plaintiff.
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Old 05-19-16, 09:36 AM
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Originally Posted by McBTC
the integrity of the part was compromised by the initial crack and although the fix allowed the part to function under normal loads, given the high load condition that was experienced at end of the part's fatigue life, .
I think its equally possible that with the epoxy-wire patch I have on my bike even with the crack in the head tube, my bike is now stronger than a bike that has a head tube with no crack. Basically the head tube on my bike is now over-engineered. That acutally does have some other risks though like concentrating the stress somewhere else like on the top tube. But I think the risk is mininimal. Its lunch time, time for a death defying ride.
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Old 05-19-16, 09:55 AM
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Originally Posted by kennj123
Basically the head tube on my bike is now over-engineered. That acutally does have some other risks though like concentrating the stress somewhere else like on the top tube.
Maybe you should wire & epoxy the rest of the frame as a preventative measure.
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Old 05-19-16, 09:58 AM
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Originally Posted by kennj123
I think its equally possible that with the epoxy-wire patch I have on my bike even with the crack in the head tube, my bike is now stronger than a bike that has a head tube with no crack. Basically the head tube on my bike is now over-engineered. That acutally does have some other risks though like concentrating the stress somewhere else like on the top tube. But I think the risk is mininimal. Its lunch time, time for a death defying ride.
Your ignorance is funny because of the certainty with which you think you understand. I don't think there is immediate danger to riding the bike as is (as there would not have been to ride without random wire and fiberglass wrappings) but your opinion of the modifications you made (I won't call it a repair) are hilariously wrong.
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Old 05-19-16, 10:10 AM
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Originally Posted by Wilfred Laurier
Your ignorance is funny because of the certainty with which you think you understand.
I said this 'I think its equally possible'.

'Equally possible' means 50%. How anyone twist that into thinking I have 'certainty' in my solution is completely beyond me. Is english your native language?

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Old 05-19-16, 10:24 AM
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Originally Posted by cobba
Maybe you should wire & epoxy the rest of the frame as a preventative measure.
I love the way i get blamed for being snarky and trolling but a comment like this gets a pass.

Last edited by kennj123; 05-19-16 at 10:34 AM.
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Old 05-19-16, 10:44 AM
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Old 05-19-16, 10:46 AM
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Originally Posted by cobba
Maybe you should wire & epoxy the rest of the frame as a preventative measure.
First, he should stop-drill the rest of the frame.
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Old 05-19-16, 10:46 AM
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Keep going .. make a Big bulbous overwrap of Fiberglass and lots More epoxy..
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Old 05-19-16, 10:50 AM
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The fix I employed when my Salsa Bandito also cracked at the bottom of the head tube was to never again purchase a scandium frame.
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Old 05-19-16, 11:07 AM
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Originally Posted by kennj123
I think its equally possible that with the epoxy-wire patch I have on my bike even with the crack in the head tube, my bike is now stronger than a bike that has a head tube with no crack. Basically the head tube on my bike is now over-engineered. That acutally does have some other risks though like concentrating the stress somewhere else like on the top tube. But I think the risk is mininimal. Its lunch time, time for a death defying ride.
This thread just keeps on giving.

You think it's equally possible because "stronger/not stronger" seems like a 50-50 proposition to you?!? If you understood the engineering of composite structures you would know that there is no significant force path between the head tube and patch. Thus you have not affected the underlying process. You have only made your bike heavier, not stronger, and made monitoring of the cracks impossible [bonus].
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Old 05-19-16, 11:20 AM
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Originally Posted by AnkleWork
T no significant force path between the head tube and patch. [bonus].
I've said it before, it all comes down to how well the aluminum head tube aheres to the epoxy. if the bond is good, it will work great. If not there is a possiblity the head tube will impode.
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Old 05-19-16, 11:28 AM
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Originally Posted by kennj123
I said this 'I think its equally possible'.

'Equally possible' means 50%. How anyone twist that into thinking I have 'certainty' in my solution is completely beyond me. Is english your native language?
It is far less than a 50% chance that your modifications have any positive effect. Maybe after the headtube finishes breaking, if you were to keep riding it, the wire will keep all the parts together to make it easier to clean up the accident site. I suspect the failure will manifest itself in a way that effectively discourages riding long before that, though.
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Old 05-19-16, 11:33 AM
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Originally Posted by kennj123
I've said it before, it all comes down to how well the aluminum head tube aheres to the epoxy. if the bond is good, it will work great. If not there is a possiblity the head tube will impode.
So you're saying that epoxy shear strength, wire tensile strength, headtube compressive strength, headtube internal stress, wire internal stress, and about a dozen other factors are not important. OK, it's your teeth.

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Old 05-19-16, 11:38 AM
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This entire thread has become a pointless debate between the OP and those ranging from those who say it won't work, to those implying imminent hazard and potential serious injury.

While I have little positive to say about the repair, I don't have anything really negative either, and don't endorse the notion that it represents any danger to the OP or anyone else.

Since even the OP says it's not a permanent long term solution, and will fail eventually, it's only a question of how long it lasts, and only time will answer that. Whether it's as long as the OP expects, is for the OP to decide, and whether it lasts longer than if he did nothing at all is unanswerable.

As far as any danger, I must have a very limited imagination because I can't see how a head tube split, especially one wrapped in fiberglass can lead to a catastrophic event with injury.

So why don't we spare ourselves the unnecessary acrimony, and table this a while until the OP (or his heir) reports how it held up.
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Old 05-19-16, 11:45 AM
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I have also worked a lot with epoxy. If the OP got the prep and mixing right and got a really tight wrap with that steel wire and the is epoxy in the cracks, I bet that the death of this frame will be from something completely unrelated. First,the crack probably won't grow. And if it does, so what? Maybe he will have to retire the frame because the slightly loose HS bugs him. If his work was good though, I'll wager my first guess, that that it holds up as long as the frame lives.

I would have done the repair a little differently. If I did a steel and epoxy wrap. I'd start with the good flowing epoxy, probably wedging the crack open a bit to get it in there, then hose clamp it closed until it sets. Pull the hose clamp, wrap with a tight spiral of wire say 1/2" vertical, finishing by twisting the wires together and tightening them by twisting further with a stick or vise grips with vicegrips. Epoxy that with a small paint brush. (Actually, I would do the wraps, start the twisting but not the tightening, then epoxy and last tighten the bejeesus out of it.)

I did a repair years ago on a frame that had been struck by probably an SUV hard, trashing the fork, denting the top tube and bending both dropouts several inches to the right. Got a new fork and straightened the stays. Two weeks later I noticed each chainstay had a crack just behind the bridge; 2/3 and 1/3 circumferences respectively. I repaired it with a carbon fiber wrap starting a couple of inches up the down tube, over the whole BB and back to several inches past the bridge on both sides, going over the bridge as well. One of the tougher laminating jobs I have done in my years of hand lay composite work. After I cleaned up, I took another look. Horrors! Big voids were forming as the rather stiff CF unidirectional started to show its stuff. I hastily cut inner tube strips and did a very tight wrap around the entire job. Messy! Epoxy oozed out everywhere.

Next day I went to see if I could salvage the bike. (I paid $20 for the frame, $2? for the epoxy and someone gave me the CF years before so i had nothing to lose except I loved that bikes ride from the first.) I guessed the innertube was now part of the job, but it unwrapped perfectly cleanly. And underneath was a CF job that looked professionally vacuum bagged. Rode 8000 miles on that repair until I retired the bike because I no longer trusted it. (What else was going to fail? The slam that sport Peugeot 501 tubed frame took was not minor.) Besides, I had its replacement on hand, a custom inspired by it.

That retired bike was Jessica. Its replacement: Jessica J. The two most fun bikes I have ever ridden.

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Old 05-19-16, 12:33 PM
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If the resin is any good at all the wire will only make it weaker, although if resin fractures it still may be kept in place around the head tube by the wire.
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Old 05-19-16, 12:36 PM
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Originally Posted by rmfnla
Unless you abused the bike those cracks didn't just appear.

Not sure about the second paragraph; was the seller Amish..?
Is the headset a factory headset?

Is it possible the bike was assembled from a pile of parts?

I think I've run a 30.0 mm headset cup in a 30.2mm head tube, and survived the day.

But, what about running a 30.2mm cup in a 30.0mm head tube?

If that is the case, then whoever assembled the bike is at fault.

Oh...
Never mind. Probably a 1 1/8" headset, so that wouldn't be the issue. I do wonder, however, if the cup was too tight for some reason. Maybe the head tube wasn't properly reamed at the factory.
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Old 05-19-16, 12:46 PM
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Originally Posted by AnkleWork
So you're saying that epoxy shear strength, wire tensile strength, headtube compressive strength, headtube internal stress, wire internal stress, and about a dozen other factors are not important. OK, it's your teeth.

[Don't quit your day job.]
I might as well go for broke and start blowing up this thread once and for all. Anyone quote me from here on out get full fury response until thread is locked.


the adhesion between aluminum and epoxy is issue of two very dissimilar materials being compatible together using a one time, improvised procedure. The rest of the materials you mentioned are all factory made to reasonably high quailty standards.

Ankework, please quit your day job. your an idiot and can't be doing your job correctly given your limited brain capacity.

ka-boom.
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Old 05-19-16, 12:48 PM
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Originally Posted by CliffordK
Is the headset a factory headset?

Is it possible the bike was assembled from a pile of parts?

I think I've run a 30.0 mm headset cup in a 30.2mm head tube, and survived the day.

But, what about running a 30.2mm cup in a 30.0mm head tube?

If that is the case, then whoever assembled the bike is at fault.

Oh...
Never mind. Probably a 1 1/8" headset, so that wouldn't be the issue. I do wonder, however, if the cup was too tight for some reason. Maybe the head tube wasn't properly reamed at the factory.
Bike is 15years old but in surprising newish condition. Everything is stock according to knowyourbike and bluebook.
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