frame repair

Discussion in 'Mountain Bikes' started by Danneh, Feb 5, 2004.

  1. Danneh

    Danneh New Member

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    About 2 months ago i got hit by a car riding my pride and joy Giant TCR composite 1, the accident was my fault (broke up with gf previous night) lack of attension (my bikes are now insured, im a fool). Anyhow i got off very likely just heavy bruising but my wheel was crisped and the tube that goes from the rear mech to the seat post has a bad crack neat the top.

    My question is, can anyone give me any advice on how to repair composite frames ? theres no way i can replace it even with a low spec frame so im gonna have to have a go, its killing me not riding (although it has taken me two months to even contemplate repairing it and riding again).

    Thank you in advance
     
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  2. Danneh

    Danneh New Member

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    Sorry posted in wrong place just realised this is mtb, cant seem to delete :[
     
  3. Hecubus

    Hecubus New Member

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    Sorry but the sad truth is that frame now belongs in the garbage. If it was a steel frame MAYBE there is something that could have been done about it but carbon and Al frames are useless once something like that happens. I think your best bet is to see if Giant has some sort of crash replacement warranty in which they sell you a new frame at a very low cost.
     
  4. boudreaux

    boudreaux New Member

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    Actually, many CF frames can be repaired, depending on the construction method.It may not be cost effective though. Even 7xxx series aluminum is repariable, but 6xxx isn't because or the required heattreatment.
     
  5. Hecubus

    Hecubus New Member

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    I know there are places that can repair some aluminum frames depending and the damage but its not always a guarranteed to be succesfull. I suppose some carbon might be repairable but I have never heard of any company that would rapair them. I don't think it would be rapairable unless the crack was relatively small. Either way, I think its safer to just get rid of the frame in such a situation. I sure as hell would never trust a repaired carbon frame.
     
  6. dabac

    dabac Well-Known Member

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    I haven't tried repairing a bike, but I've built and repaired a lot of composite structures over the years and I can't see why a bike should be any exception to the rule. First do a bit of research - try to find out more about how the frame actually is produced. What type of resin is it that binds the carbon fibre layers together? What other resins that can be handled outside a factory setting are there that can bond to the one they've used? If theirs is some sort of epoxy you are quite likely to be able to find a matching product. Even if theirs isn't an epoxy you might still find one with matching characteristics. A well equipped shop that caters to boat builders should be able to help you with both resin and some carbon fibre tape. Make a couple of "dry" runs by wrapping the the injury with another material or a length of fibre that you'll later discard until you've figured out how you're going to apply the "bandage", then prep the surface. You don't want to cut into the fibers too much, but run a fine-grit sandpaper over the damaged area and an inch or so on to the unaffected surfaces. Wash with a non-staining detergent and let dry (acetone should do OK). Mix up your resin, coat the prepped area (a brush is probably the tool of your choice here) and apply the carbon fibre tape as smooth as you can. When you've done one layer coat it with more resin until the surface becomes saturated, then add the next layer. Keep going until your satisfied with the thickness of your repair (2-3 mm should be sufficient depending on the length of the repair).

    Some tips you might want to consider: Mix a small batch first and try different application techniques until you've figured out when the fible cloth is sufficiently saturated. For optimum strength/weight ratio you want as little resin as possible while still retaining full saturation, but in this case you shouldn't be too concerned about that.
    If the salesman is unsure about material compatibility and bonding you might want to pick a small secluded spot on the bike and do a trial application. Prep a 1x1 cm surface, take a piece of carbon fibre (Several layers, fully saturated) and stick it there. Leave yourself a tab to pull with. Once the resin has cured properly give it a good pull and see what happens. If the pull is parallel to the treated surface your grip (even with pliers!) should slip before the patch breaks free.

    Disclaimers and warnings: Epoxy is toxic. Protect your skin from spill and your airways from fumes. Wear gloves and an approved mask.
    The accident might have damaged your bike in some other place that you haven't discovered yet, or your repair might not be as good as you thought. Inspect it CLOSELY for other damage prior to repair. After repairs start with easy rides and inspect after each one. Be attentive to how the bike handles. Any further deterioration needs to be taken very seriously.

    There's a site somewhere that describes how to fix a broken carbon fibre saddle, it might serve as some inspiration if you can track it down.
     
  7. Danneh

    Danneh New Member

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    wow dabac thats some really useful info thanks. I have got in touch with a company specialising in boat repairs and hes sorted me out with a repair kit that should do the job, he even told me some of their repair jobs can withstand 80 tonnes!!!!!! So fingers crossed.
     
  8. Greg-O

    Greg-O New Member

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    so how did it turn out?
     
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