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Old 09-02-10, 12:34 PM   #1
neomoco
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cracked carbon frame near the seapost suggestions ?

hi guys ,
i have a problem with my carbon frame , a small crack has apeared near the seatpost clamp ,
it seems that the seapost has cracked probably because of overtight , and at the same time the frame has cracked about 1 cm
the seatpost clamp was switched on the other side , i was thinking maby is better this way
what do you think is that dead frame walking ? will the crack extend ?
or is there something that can be done ?
suggestions ?
thanks

picture : http://img830.imageshack.us/img830/3663/p1010601.jpg
http://img255.imageshack.us/img255/355/p1010608w.jpg
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Old 09-02-10, 12:41 PM   #2
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If it were Metal you can stop a crack from continuing by drilling a hole in the end of the crack..
you could try that with CF and That may help..

I think you may be needing to replace the frame..

Another data Point to keep me on metal frames , preferably steel.
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Old 09-02-10, 12:57 PM   #3
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If it were Metal you can stop a crack from continuing by drilling a hole in the end of the crack..
you could try that with CF and That may help..

I think you may be needing to replace the frame..

Another data Point to keep me on metal frames , preferably steel.

That does scare me about carbon. But I would still like one. Do they still make titanium bikes? Haven't heard about them in, oh about 20 years.
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Old 09-02-10, 01:14 PM   #4
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I don't think the crack will spread. However, I would reinforce the spot with Epoxy, and wrap with a few strands of carbon fiber, Kevlar, or fiberglass.

I don't know if you ever worked with composites before, probably not, since you wouldn't be asking.

What I'm saying is, you are lucky, because carbon fiber can be repaired with Epoxy and fiberglass, at room temperature 75 or 80 degrees F.- you don't want or need a welding apparatus.

I would use Kevlar and epoxy to wrap the cracked tube. You'll have to search online to find Kevlar.

Epoxy is available at the local hardware store. Look for 2-Ton Epoxy, in the 25 ml. double syringe, made by a company called Devcon.

You could get a good piece of fiberglass at a Hobby store, that sells model airplanes. This repair should cost less than twelve dollars, including the cost of disposable latex gloves to wear.
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Old 09-02-10, 01:21 PM   #5
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I think it can be fixed. It is hard to make out from the pics but I would assume that the carbon fabric did not tear, but only the epoxy has cracked. It could probably be infused with more epoxy then wrapped with a few layers of prepreg carbon ribbon to shore up the crack. I might not look as pretty with the extra layers, but it should hold. This procedure is best left to a person with experience with making repairs to CF bike frames. Craig Calfee comes to mind if you don't know of anyone local. If the frame is expensive enough to warrant the repair, you might want to send a few pics to Calfee and get his opinion and possibly an estimate to make the repair. I know that he does make repairs on frames other than his own.

Edit: Looks like hotbike was thinking (pretty much)the same thing but beat me to the punch with an answer. I don't know if I would trust fiberglass, but you might get away with it if you use more thickness than I was picturing. If you can get any kind of carbon cloth or prefereably unidirectional ribbon, I would have more confidence in the long term.

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Old 09-02-10, 02:14 PM   #6
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Do they still make titanium bikes? Haven't heard about them in, oh about 20 years.
The sure do. Litespeed, Lynskey, Moots, Airborne, Merlin, Seven, Independent Fabrications and many others are still very much in the Ti frame business.
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Old 09-02-10, 02:19 PM   #7
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thank you guys for you answers

i`m not from uk or us or a big country , i`m from eastern europe so most probably i will have to get the materials for repair online

this is what i found until now :
kevlar :
http://cgi.ebay.co.uk/KEVLAR-FABRIC-...#ht_562wt_1137

epoxy
http://cgi.ebay.co.uk/Devcon-2-Ton-C...ht_2793wt_1137

in my area there arent serious repair shops not to mention carbon specialists , so i will have to do the thing alone so what do you think about the materials ?
maby some suggestions on other materials to use ?

fiber glass is this any good ? : http://cgi.ebay.co.uk/Body-Filler-Sp...1#ht_927wt_911


wouldn`t some carbon fibre be advised ? don`t know for what to search on ebay could someone help ?

i found this carbon repair kit opinions ? : http://www.carbonmods.co.uk/Products...epair-kit.aspx

Last edited by neomoco; 09-02-10 at 02:48 PM.
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Old 09-02-10, 02:39 PM   #8
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Devcon epoxy should be perfect. The kevlar should work too but is not as stiff as carbon plus there is the matter that kevlar is yellow and will need to be painted if you don't want the repair to stand out. Carbon tape or fabric (cloth) would be better if you can find someone who ships to your country. One foot of this stuff would work. http://cgi.ebay.com/Carbon-Fiber-Tap...item3a57a49239
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Old 09-02-10, 03:29 PM   #9
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i could search for some carbon fabric tape , how many layers should i apply ?

if i buy from different sources the epoxy the carbon + transport it`s gona get epxensive anyway

wouldn`t it be better to just buy this repair kit wich seems proffesional ?

http://www.carbonmods.co.uk/Products...epair-kit.aspx

and is about 60 dollars with transport included

what do you think about the kit ?

Last edited by neomoco; 09-02-10 at 03:37 PM.
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Old 09-02-10, 03:46 PM   #10
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Originally Posted by neomoco View Post
hi guys ,
i have a problem with my carbon frame , a small crack has apeared near the seatpost clamp ,

picture : http://img830.imageshack.us/img830/3663/p1010601.jpg
http://img255.imageshack.us/img255/355/p1010608w.jpg
STOP- WAIT- A QUESTION FOR YOU

Did you check with your LBS if it's under Warranty?

My friend had a similar issue and wanted to trash the frame. I went to the Orbea web site and saw that his frame was covered.
The LBS handled the swap and actual he received a new seat post, stem and handlebar and a better model.

If you try to fix it you will forever void any chance of it being a warranty issue.
of course it looks like you over torqued the seat post clamp, but that happens.
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Old 09-02-10, 03:54 PM   #11
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i`m pretty sure that the frame is not under warranty anymore

the best i could find was this :

http://cgi.ebay.co.uk/SAMPLE-CARBON-...#ht_550wt_1137
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Old 09-02-10, 05:01 PM   #12
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It LOOKS like the area that broke is being pulled inwards to be in contact with the seat post. What is the fit like between the post and the frame? I'm thinking that the seat post was a little too loose a fit and the seat clamp pulled the top of the frame in hard enough and the relief cut in the seat tube was short enough that it snapped this area to allow the clamp to pull the frame into tight contact. If I'm right then it's not the seat clamp being too tight but a poor fit of the seat post to frame. A proper fit should be a light push fit that will hold the post and maybe even post and saddle in place by itself without any clamp even being on the bike.

If it were me I'd fill the crack with a good grade of clear epoxy WHILE the seat post clamp in in place and tight. Just be sure there's some thing on the post to prevent the epoxy taking hold of that.

There's really no point in taking the post out and binding the frame since the clamp will just want to snap the repair all over to make it fit the post. And in fact looking at the picture of the crack it sure seems like I can see that it's flexed inwards which supports my suggestion that the seat post is too small. It may be the correct size but the frame is out or the post is a smidge under the correct size but not enough to be the next size down. Either way I'd bet that with no clamp and if that area springs out that the post will literally fall into the frame. And that sort of easy sliding fit is too loose.
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Old 09-02-10, 05:17 PM   #13
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it`s actually the other way arround ... the seatpost fits the frame very well
it`s actually very hard to move the seatpost inside the frame when i want to lower it or get it out ... the length of the seapost is good aswell so that is not a problem
as i wrote at the begining of the thread the seapost cracked probably because of overthight and this way it probably made itself a little smaller because of the crack (vertical crack near the seatpost clamp about 2 cm)
i already made an order for another seapost that should arrive soon but the frame crack i have to take care of it anyway or at least try
i ordered a 400 mm alloy seatpost 31.6 - hopefully the length will help a bit

it`s clearly that the frame cracked because the seatpost cracked , i didn`t found out about it until i saw the cracked frame
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Old 09-02-10, 06:22 PM   #14
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i could search for some carbon fabric tape , how many layers should i apply ?

if i buy from different sources the epoxy the carbon + transport it`s gona get epxensive anyway

wouldn`t it be better to just buy this repair kit wich seems proffesional ?

http://www.carbonmods.co.uk/Products...epair-kit.aspx

and is about 60 dollars with transport included

what do you think about the kit ?
I have bought products from Carbonmods before you might want to contact them with what it is you want to do and they can give advice on product you should use.
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Old 09-02-10, 07:05 PM   #15
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thks for all your support
i have sent an e-mail to carbonmods and hopefully i can rezolve this problem soon
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Old 09-02-10, 08:44 PM   #16
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.....as i wrote at the begining of the thread the seapost cracked probably because of overthight and this way it probably made itself a little smaller because of the crack....

My bad. When you wrote that the first time I took it to mean the seat tube of the frame. Let's face it, folks saying that they collapsed a seat POST are few and far between so perhaps you can excuse my "translating" it to mean seat TUBE.... If you tightened things enough to collapse and crack the seatpost then it's no wonder the seat tube cracked as well.


The good news is that the crack is back on the rear where it's not highly stressed. Likely you could get away with just drilling a stress relief hole and call it a day. But if you want to repair it I'd say that the important part is to strongly link the lower fixed portion with the cracked loose "wing". To so that you need to run vertical fibers across the crack to tie things together and form a stress carrying column of carbon that runs across the crack and supports the compressive stresses that this area will see from the slanted seat tube. To do this if it were my frame I'd router out a small channel to allow the fibers to contact more of the deeper fibers to aid in tieing the crack together better. Something like this diagram below.

But really? I'd probably just glue the crack and see if it cracks loose again. If it does then the stress is working at the crack and it's loading up the fibers at the end of the crack and it will likely extend with time. Or worse, you may load the other intact side enough to begin a crack there as well. At the first sign of this happening THEN I would channel out the frame as I showed and support the crack with unidirectional carbon fibers. Wrapping around the tube won't do anything since the crack is nearly horizontal now and all the fibers from wrapping would not be crossing the crack enough to matter. All you'd do is cover up the damage and let it continue where you can't see it. If you run vertical fibers across the crack either with the "excavation" I showed below or as a purely surface patch then at least you're crossing the crack and supporting the fibers on each side much like the frame was before the crack. If you do use my method the patch is going to be quite strong due to the thickness and depth. But then the bond will be key. It would be important that the epoxy you use is very compatible with the original epoxy so the joint is very strong.
Attached Images
File Type: gif seatpost crack repiar2..gif (50.4 KB, 20 views)

Last edited by BCRider; 09-02-10 at 08:51 PM.
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Old 09-02-10, 09:43 PM   #17
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Yeah, that scares me about carbon frames too. I've seen this before. I think something like this usually happens in cases where the mechanic tightened the seat binder bolt with way too much torque. It would be fine for a little while, but after sitting on the bike and riding, the constant stress put on the seat tube near the binder bolt will eventually show it's wear, possible resulting in the crack that you see here. On metal frames, you usually only get deformation near the seat tube top where the binder bolt attaches. On carbon frames, crack!
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Old 09-02-10, 09:45 PM   #18
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Yeah, a torque wrench is very much needed for working on a carbon fiber frame unless you've wrenched enough to ballpark the torque by feel (but then, you wouldn't be here). Ritchey makes a torque key which is very useful, here.
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Old 09-03-10, 03:45 AM   #19
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thank you all for your replyes ... i got this mail from carbonmods :

Thanks for your email.

That crack is only small and it should be possible to repair it quite easily.

I would suggest removing the clamp to allow the cracked area of carbon frame to relax and then sand-papering the tube all around where you will do the repair (in fact all the way around the tube in a ring shape) so that you have a good rough surface for the repair to bond to.

This is the kit you should buy:

http://www.carbonmods.co.uk/Products...epair-kit.aspx

Apply some resin to the tube (making sure it gets into the damaged crack) and allow it to cure partially so that it is just tacky. Then cut a thin strip of carbon for the repair and wrap it around the tube several times. It will stick well to the partially cured resin so it will be easy to get started. Pull tight and wind it wound about 3 times, wetting it out with more resin as you go. Once finished, wrap the repair tightly with the shrink tape (included in the kit) and heat the tape to make it tighten. Allow to cure for 8hrs. Once cured remove the tape. If you want you can smooth and polish the repair to make it look neater (sandpaper and polish are included in the kit for this purpose). It should be very strong.

Best regards,

Matt



do you know what he meant by " wind it wound about 3 times " - english is not my first language and i don`t realy understand the expression ?

@BCRider thank you for you suggestion ... but in my opinion i think a wrap around would be better if you look carefully at the picture the crack has a down path its`s not orizontally ... i think a wrap arround would be best as suggested by carbonmods
but i`m thinking if i wrap arround how much should i avoid covering the hole (the cut in the frame for the seatpost clamp to bend the frame) / should i wrap it and apply the exposy and then cut the chanel ? or should i just try and wrap it just under the chanel

Last edited by neomoco; 09-03-10 at 04:27 AM.
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Old 09-03-10, 05:39 AM   #20
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Originally Posted by neomoco View Post
thank you all for your replyes ... i got this mail from carbonmods :

Thanks for your email.

That crack is only small and it should be possible to repair it quite easily.

I would suggest removing the clamp to allow the cracked area of carbon frame to relax and then sand-papering the tube all around where you will do the repair (in fact all the way around the tube in a ring shape) so that you have a good rough surface for the repair to bond to.

This is the kit you should buy:

http://www.carbonmods.co.uk/Products...epair-kit.aspx

Apply some resin to the tube (making sure it gets into the damaged crack) and allow it to cure partially so that it is just tacky. Then cut a thin strip of carbon for the repair and wrap it around the tube several times. It will stick well to the partially cured resin so it will be easy to get started. Pull tight and wind it wound about 3 times, wetting it out with more resin as you go. Once finished, wrap the repair tightly with the shrink tape (included in the kit) and heat the tape to make it tighten. Allow to cure for 8hrs. Once cured remove the tape. If you want you can smooth and polish the repair to make it look neater (sandpaper and polish are included in the kit for this purpose). It should be very strong.

Best regards,

Matt



do you know what he meant by " wind it wound about 3 times " - english is not my first language and i don`t realy understand the expression ?

@BCRider thank you for you suggestion ... but in my opinion i think a wrap around would be better if you look carefully at the picture the crack has a down path its`s not orizontally ... i think a wrap arround would be best as suggested by carbonmods
but i`m thinking if i wrap arround how much should i avoid covering the hole (the cut in the frame for the seatpost clamp to bend the frame) / should i wrap it and apply the exposy and then cut the chanel ? or should i just try and wrap it just under the chanel


Hey. Fantastic! You got a decent solution there to try the repair yourself. Come back to this thread and let us know if you were successful with the repair. I'd be interested to know if it worked. Good luck!
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Old 09-03-10, 06:22 AM   #21
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"Pull tight and wind it wound about 3 times, wetting it out with more resin as you go." --neomoco

Matt, meant to cut a length of CF long enough to make three layers of cloth over the crack. Start the first layer with the partially cured epoxy, once you've made the first revolution apply the resin to the cloth and make two more revolutions.

"...english is not my first language and i don`t realy understand the expression ?" --neomoco

I think that was a mistype... English can be quite fractured depending on where it's spoken, however.

Brad
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Old 09-03-10, 07:25 AM   #22
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"Pull tight and wind it wound about 3 times, wetting it out with more resin as you go." --neomoco

Matt, meant to cut a length of CF long enough to make three layers of cloth over the crack. Start the first layer with the partially cured epoxy, once you've made the first revolution apply the resin to the cloth and make two more revolutions.

"...english is not my first language and i don`t realy understand the expression ?" --neomoco

I think that was a mistype... English can be quite fractured depending on where it's spoken, however.

Brad
I think he meant "wind it AROUND three times".

Pardon me, but when I gave my earlier reply, I had not looked at the photographs. Now, looking at the photographs I see the problem.

neomoco wrote:
"....but i`m thinking if i wrap arround how much should i avoid covering the hole (the cut in the frame for the seatpost clamp to bend the frame) / should i wrap it and apply the exposy and then cut the chanel ? or should i just try and wrap it just under the chanel"

You should wrap the carbon around, covering the channel. After the epoxy hardens, cut the channel. A file or a hacksaw will be fine.

Three times, or three layers, might be too much. You might make it impossible to hold the seat-post tight, if the binder bolt can not squeeze the tube.

Kevlar would be a good material, however, Kevlar is very difficult to cut, being as it is nearly indestructible.

The carbon mod repair kit has more carbon and resin than you need.
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Old 09-03-10, 07:41 AM   #23
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I think he meant "wind it AROUND three times".

Pardon me, but when I gave my earlier reply, I had not looked at the photographs. Now, looking at the photographs I see the problem.

neomoco wrote:
"....but i`m thinking if i wrap arround how much should i avoid covering the hole (the cut in the frame for the seatpost clamp to bend the frame) / should i wrap it and apply the exposy and then cut the chanel ? or should i just try and wrap it just under the chanel"

You should wrap the carbon around, covering the channel. After the epoxy hardens, cut the channel. A file or a hacksaw will be fine.

Three times, or three layers, might be too much. You might make it impossible to hold the seat-post tight, if the binder bolt can not squeeze the tube.

Kevlar would be a good material, however, Kevlar is very difficult to cut, being as it is nearly indestructible.

The carbon mod repair kit has more carbon and resin than you need.

well i was thinking i`m not gona wrap the whole tube all the way up so basically in not gonna put any carbon were the seat clamp squezeez the tube ... so what do you think is that a good ideea ?
i might put only 2 layers i`ll see how thick the carbon is .... thks for the advice

of course as soon as i will fix it i`ll post the pictures ... for now i wait for the carbonmods kit that i ordered

Last edited by neomoco; 09-03-10 at 10:08 AM.
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Old 09-03-10, 08:14 AM   #24
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hotbike, I didn't take the directions to also cover the seatpost's slot, at the most just a small percentage at the lower end.

Looking again at the pictures I think that drilling a stress relief hole at the end of the crack(s) and a couple of single layer patches, one on each side of the seatpost would possibly work just fine. Lay the patch on the partially cured resin, use a small roller to remove any voids, apply a top coat of resin and again use a roller.

Because it may be difficult to determine if the seatpost clamp was overtightened or if constant flexing through normal riding is the root of the problem, I wonder if a tight fitting mountain bike seatpost, which is typically longer than a road bike's seatpost might offer a bit less flexability by reducing leverage thus helping to prevent these semi common CF failures. Thoughts?

Brad
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Old 09-03-10, 10:13 AM   #25
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i thought about buying a longer seatpost clamp myself but i think is going to put even more stress near the crack
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