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To fix or not to fix (cracked headtube)
#1
Oh yea, the dreaded crack in the headtube. The question is this. If you have a bicycle that you really want save the frame, what would you do to repair this? I have a couple Ideas myself but would like others to chime in with their ideas of how to make this a safe usable frame once again. So do not be shy lets hear it! This is kinda part 2 of the Czech bicycle thread. Being as its the only one I am aware of on this side of the pond I really want to save it from the scrap yard. If there are any Bicycle tutor friends from Europe that know anything about the brand Superior bicycles I would like to hear what you have to say about the company too.
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
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#2
Not sure where I saw the video or instructions but I think on a certain type of alloy, lugged, and other conditions that the headset piece can be removed from the rest of the frame. The only thing you would have to do is match the piece you are taking off as in geometry and all the other math involved.
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
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#3
A good welder may be able to weld the crack and make it reasonably strong. There is a chance of distorting the frame, weakening the metal, and missing other weak points that aren't showing yet. Note that the paint will be destroyed in the area. If you go this route, make sure it is someone who knows what they're doing working with aluminum.

If anyone tells you to glue this, use JB Weld (or a Euro equivalent), etc. - don't. This is a very dangerous crack. If it let's go the fork's going to fold up under you and you're going to get hurt. I'm not so sure even about welding this, but it's not completely ridiculous.

Sorry - bad luck!
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#4
I've seen this sort of thing on aluminium frames, cracked head tubes in particular, on another forum; the general consensus seems to be that unless it's a rare and valuable frame and you're prepared to spend a fair amount to get it repaired properly and safely, then it's best to scrap the frame. Sad
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#5
thanks for the advice guys, so far its about what I expected to hear.
My thoughts are this, I thought I would sleeve the inside with a a bonding adhesive, then cnc rings to bond and press on the top and bottom of the headtube (outside). I have seen other attempts of people welding, drilling, cutting, so I thought I would try and save the paint the best I could. If I fail I am out nothing I guess.
Do you think this would work, costs aside ?
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
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#6
When aluminium frames fail, they can fail catastrophically, given that it's the head tube that's cracked it could lead to a very nasty accident if it does fail completely and suddenly, so a repair may work and be absolutely fine, but is it really worth the risk?

I wouldn't ride it.
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#7
Uggh wish I could give a positive yes or no bro. I'm not really a metallurgical expert. So basically you are thinking of taking an alloy tube that just fits the inside of the head tube with some sort of bonding material to make it a permanent "weld". Then take some sort of rings that would over lap the outside of the head tube but go inside of the sleeved tube that would be bonded as well?
Correct me if I am wrong but can there be micro cracks that run along the main crack in the head tube, like ones invisible to the naked eye?. Might be do able but one would have to ride VERY carefully on it. That is one of the major stress point of a bicycle if I am thinking right. You might get away with it for a while but the metal is already weakened and has a tear in it. My thoughts to make a very good repair is the idea you have and well the real welding of the crack. That may hold up pretty good, providing the welder know what the heck they are doing!
Sorry I really do not have anything else to contribute.
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
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#8
Found this interesting video how a MTB crack is welded.... http://youtu.be/6emWh53WpZI
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
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#9
10-4 to what DaveM and xerxes said. You can take it and have it TIG welded if its good quality aluminum , but its risky, or you can check Nashbar and buy a new frame for around hundred bucks..

http://www.nashbar.com/bikes/Product_10053_10052_511239_-1___202337
Never Give Up!!!
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#10
As a Mechanical Design Engineer; I strongly recommend against riding this frame ever again, no matter what you do to it.

George has the best suggestion - no frame, spend some money to have it powder coated and detailed to match.

It is hard to tell for sure from the picture; but it looks like a fatigue crack, which started at a localized sharp point, maybe a burr on the bearing race, or a ding during assembly, or an inclusion in the casting (it looks like a cast aluminum head tube to me - which is a really bad idea for some many reasons).

A few degrees to the left there is another defect visible, this will probably also crack.

Now if you want to hang it on the wall; with it disabled so it can never be riden; that is another matter all together.
Nigel
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#11
So if I understand everybody correctly "scrap it"! Man, what a bummer. I bought the bike for parts anyway. Just thought I would stir things up and get some input. Todays structural and even non-structural adhesives are quite impressive and have gained more and more popularity in the engineering fields of Marine, automotive, and aerospace technology to name a few. I purchased this bicycle to repair and repair with little to no welding at all. The structural engineers that I have consulted with tell me it can be done and will be stronger than it ever was and the beauty of bonding means I may use different materials if need be that would create a "ply matrix" if you will. However due to expansion and contraction differential I will probably use similar materials to bond. Again from a financial perspective sure scrap it! I just happen to have the luxury of a fabrication company "Matcor" at my finger tips.
http://www.matcor-matsu.com/
If anyone can do it we can. I appreciate all the responses from my Tutor buds, all sound advice. I am one to say always to "Error on the side of Caution". But being in Manufacturing and development sometimes you have to go farther to make strides and achieve what used to be impossible possible. I will keep you posted on whether or not it was a success, still some planning to do
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
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#12
(12-13-2012, 03:46 PM)xerxes Wrote:  When aluminium frames fail, they can fail catastrophically, given that it's the head tube that's cracked it could lead to a very nasty accident if it does fail completely and suddenly, so a repair may work and be absolutely fine, but is it really worth the risk?

I wouldn't ride it.
Echo.
That frame, Bob, is a wall-hanger. Trust me (and xerxes).
I don't care what Super-Wonder-Epoxy and sleeve material / method you use. A heavy Zip Tie would be just as effective.
Consider this - YOU know how you will treat the frankenbike and may not ever intend to do more than cruise the 'hood in your Stuperman T-shirt and get road rash on a street corner. Suppose you got hit by a bus and your widow had to sell it to help pay for your cremation ($999) Smile .
How you gonna feel, sitting up there in Heaven, looking down on a fellow cyclist that thinks he has a dirt-worthy frame, and then the headtube fails in a creek-crossing and our friend is suddenly sitting beside you on that cloud and offering to teach you to play the Harp better??

Recycle.

With the advent of Mountain Biking, I've noticed a marked improvement in the quality of aluminum beer cans. Smash it in the machine and take your money. Seriously.
Wheelies don't pop themselves. (from a QBP fortune cookie)
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#13
Thanks Rob, for now it is being recycled in the fluid trainer for the winter. Still a chance a bus may bust through wall and get meSmile I still have to try it out for the sake of trying. I am certainly not desperate for another bicycle really. If it has to stay in the trainer when I am done thats fine too. scrap it out for a $1.50, nope! It is better to fail and learn than to never have failed at all (builds character). I cannot go back to my engineers and tell them they are wrong,have you ever tried telling one they are smoked up?
I will utilize a pull tester that will determine exactly how much force per square inch it will take to breach the bond before I will proceed with the bonding of the headtube. I believe it will be in the 1500 lb. range or the aluminum will snap or tear before the bond breaches. It will not fail catastrophically if I can achieve that failure rate in a pull test of one square inch of bond. I will not assume anything until the test results and data taken has been analyzed for this specific application and analyzed again. that will determine how far I am willing to go on or not. We shall see but at least I will know with facts and data the possibility of saving and using a SaFE! frame that other wise has met its demise.
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
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#14
Throw it away and buy a steel frame - steel is real. Big Grin

Some are fairly cheap too: http://www.on-one.co.uk/i/q/FROOVDO126/on_one_inbred_26er_vertical_dropout
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#15
(12-14-2012, 04:30 AM)painkiller Wrote:  Thanks Rob, for now it is being recycled in the fluid trainer for the winter. Still a chance a bus may bust through wall and get meSmile I still have to try it out for the sake of trying. I am certainly not desperate for another bicycle really. If it has to stay in the trainer when I am done thats fine too. scrap it out for a $1.50, nope! It is better to fail and learn than to never have failed at all (builds character). I cannot go back to my engineers and tell them they are wrong,have you ever tried telling one they are smoked up?
I will utilize a pull tester that will determine exactly how much force per square inch it will take to breach the bond before I will proceed with the bonding of the headtube. I believe it will be in the 1500 lb. range or the aluminum will snap or tear before the bond breaches. It will not fail catastrophically if I can achieve that failure rate in a pull test of one square inch of bond. I will not assume anything until the test results and data taken has been analyzed for this specific application and analyzed again. that will determine how far I am willing to go on or not. We shall see but at least I will know with facts and data the possibility of saving and using a SaFE! frame that other wise has met its demise.

Holy cow, man. Are you and Nigel (nfmisso) related? Why do I get the feeling I'm about to step in poop, here? Wink
Engineering is a very cool and needed field of expertise but it is often reprimanded by Real World Results. Remember the Edsel? Just ugly. Okay - that was the Design / Marketing Group but, ain't many still on the road. Smile
The 'test' that you intend to run on that headtube is not unfamiliar to me. You may as well put it through a Rockwell hardness test while you're screwing around. None of that "science" will amount to a hill of beans if the frame is subjected to a SUDDEN, sharp, off-camber landing by an aggressive MTB'r trying to save skin. That's probably what caused the fracture to begin with. We all know that a repair is seldom stronger than the original build.
Ride it on the Trainer and enjoy the scenery. Don't forget the heavy-duty zip-tie.
That frame, Bob, is NOT dirt worthy and I would hate to see it get into unsuspecting hands. It is your duty, as a promoter of the cycling lifestyle, to ensure that only reliable equipment escapes your shop, brother. $1.50? Say what??
Now that I have chastized you and embarrased us both in front of our peers - I think that the quote that you were searching for was...
"Try not. Do. Or do not." Jedi Master Yoda.

Merry Crashmas.
Rob
Wheelies don't pop themselves. (from a QBP fortune cookie)
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#16
Hahahahah your killing me !i love it. fear not Rob. I would never sell this frame to anyone ever and or recommend this procedure I am about to attempt. It is purely for "what if" purposes. I would certainly chop the frame in bits before I would even recycle it to make sure nothing bad would happen if someone saw it and thought it was good. I think i could be related to Nigel now that you mention it. He really reminds me of my father in so many ways, brilliant,practical and can do wonders recycling and re-purposing things like kitty litter buckets and such. If it ain't broke don't fix it
strait forward simplistic approach and make things last forever. So do not be hard on Nigel he is the man,plus he did agree with taking this frame out of service and as I mentioned before, you guys are right, scrap it is the right thing to do. I do not want to mislead anyone new to cycling or not that this is what they should attempt. the answer is no! But I will let ya know how its coming along anyway Ha. Merry crashmas to you too. What is price of stock in zip ties anyway Rob? hook us up bro!
P.s. I make my own quotes for people to live by Smile "You only die once so you might as well enjoy it"
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
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#17
Hey PK while you are using the bike in a trainer drill a small hole on top of the crack kind of like a lollipop. That will keep the crack from continuing. This is something I have done with motorcycle windshields. The hole stops the crack until you can replace or plastic weld the crack. You can also put a hose clamp on it, its stronger than a zip tie. Experimenting with bonding is interesting. But do the hole thing and than bond. Let the engineers take the first test ride. :-))

In theory practice and theory are the same, in practice they are not. :-)))
Never Give Up!!!
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#18
got ya on the drilling part George, thanks. I do not want to do that simply because I want to use it as a cracko-meter if you will . I figure if I just fill the crack with paint and the headtube flexes after the inner sleeve is bonded and the solid outer rings are bonded in place then I would consider the test a failure. My Gt Tachyon also had this style headtube as with most new aluminum bikes today. I sold that bike a week or so ago, But if I ever buy a used one I think I would install similar external beefer rings on it too. One of the engineers already wants the bike when it is done. If I sold it it would be to him, he seems quite confident, I am a bit more reserved but always up for a challenge
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
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#19
Hmmm sounds like one hell of a test drive lmao Wink. Just kidding ill be waiting for results my friend.
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
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#20
I happened to come across this site, they seem to fix and repair a lot of stuff that I would have junked out. hard to believe that people spend money on repairs like that. But somebody must to make a business out of it
http://www.gripsport.com.au/photo-albums/detail/our-frame-repair-custom-engineering-service-an-overall-look
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
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