Ouch!!

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reohn2
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Re: Ouch!!

Postby reohn2 » 24 Sep 2014, 9:26pm

neilob wrote:As a number of you imply, I should feel really sick at my stupidity in allowing it to happen. And I do. I've moved past steel apart from my Thorn tourer, but I do have this nagging doubt (which has been well expressed above) that its what you can't see with carbon that's the problem. I can't imagine feeling confident hitting 40+mph on a twisting descent on that frame knowing the little I know about catastrophic failure modes of carbon fibre frames. So I will probably cut it up and bin it rather than see it somehow return to use. A shame but its the only decent thing to do.


Do you ave a good household insurance policy?
I'd check it out first before sawing it up.
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JohnW
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Re: Ouch!!

Postby JohnW » 24 Sep 2014, 11:38pm

foxyrider wrote:Good carbon frames have wall thicknesses much thinner than aluminium, comparable to steel, how thick did you all think the CF tubes are? I think there is a fair chance that my superlight Columbus steel frame would suffer similar damage to the OP's carbon fibre.

This isn't a failure, this is accidental damage so all those jumping on the 'steel is best' soapbox can return to their high horses!


Except that steel would survive that kind of accident much better, and we know better where we are with steel. I've had that kind of accident with steel frames, caused less damage thereby, and ridden for years on the frame..........well........I've done it once, actually.

We're not on high horses foxy, we just have experience with steel and doubts about carbon. Can you say with certainty that the OP's frame is safe?

(Edited for spelling)
Last edited by JohnW on 25 Sep 2014, 9:52am, edited 2 times in total.

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[XAP]Bob
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Re: Ouch!!

Postby [XAP]Bob » 25 Sep 2014, 9:21am

foxyrider wrote:Good carbon frames have wall thicknesses much thinner than aluminium, comparable to steel, how thick did you all think the CF tubes are? I think there is a fair chance that my superlight Columbus steel frame would suffer similar damage to the OP's carbon fibre.

This isn't a failure, this is accidental damage so all those jumping on the 'steel is best' soapbox can return to their high horses!

But accidental damage is one of the things you expect a frame to experience occasionally.

We'd be suggesting some touch up paint (or at least a little laquer) to restore the paint finish, but noone would be suggesting cutting it up - or that they wouldn't feel safe doing a downhill on it.

CF doesn't cope well with "non design" loads, and once it has failed to cope with those it's capacity to deal with "design" loads is potentially seriously compromised - the fact that this damage was accidental is irrelevant, it's damage that wouldn't be a concern on steel (or titanium). The life of an Al frame would likely be reduced, but not ended.
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Edwards
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Re: Ouch!!

Postby Edwards » 25 Sep 2014, 9:41am

I would very happily ride the frame as is and not be bothered about this damage. *I do have a slight doubt about it so would not ride it at 40mph down a twisting descent before getting it professionally repaired.
I would consider it wrong for the frame to be sold or given to somebody else with out them being told of this problem. I also think this information should be passed on for steel and other types of frame.

I am also considering the environment cost of jumping to the scrap conclusion. I feel that the least that should be done is get stuff properly checked and repaired if possible, before squandering the carbon it takes to build things by throwing them away.

* I not sure I could even get a bike to go that fast any more. :(
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reohn2
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Re: Ouch!!

Postby reohn2 » 25 Sep 2014, 1:23pm

foxyrider wrote:Good carbon frames have wall thicknesses much thinner than aluminium, comparable to steel, how thick did you all think the CF tubes are? I think there is a fair chance that my superlight Columbus steel frame would suffer similar damage to the OP's carbon fibre.


I disagree,even if punctured,which I doubt even a thin walled steel tube would,it'd probably ding more than a thicker one.But if perforated would still remain usable,especially on a toptube which is in compression mostly.
CF OTOH is likely to crack with than kind of impact damage,the crack is most likely only apparent on the inside of the tube where it's deflected inward.
On other threads I've made a point of this by saying CF doesn't stand up to that kind of accidental impact damage very well at all,and that's why it's not suited to the rough and tumble of everyday use. OK for ''Sunday best'' etc,but it has limited application.
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foxyrider
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Re: Ouch!!

Postby foxyrider » 25 Sep 2014, 3:49pm

JohnW wrote: Can you say with certainty that the OP's frame is safe?


No i can't but that only proves i'm not a CF technician, neither can you categorically say its not for the same reason.

The OP asked a question and i think the more sensible posters have answered that - get it checked out by the experts, it almost certainly can be repaired - hang on thats a bit like steel isn't it?
Convention? what's that then?
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Brucey
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Re: Ouch!!

Postby Brucey » 25 Sep 2014, 4:09pm

chainsets are not that heavy so I would be surprised if the frame was truly ruined by such a knock as that.

If there is significant damage in that area it will likely fall into one of three categories;

1) obvious and structurally worrying
2) worse than it at first looks, and apparent when you do more tests/examination.
3) not bad at this time, but may compromise the strength of the thing in the long term.

As others have pointed out the prospect of 3) is what gives me the willies, but if you are going to have a knock anywhere, arguably the top tube isn't a bad spot. On the fork or the steerer it would be a different story.

If you think it is 2) then a closer look is warranted. Ad hoc tests can include using a mirror on a stick inside (or a borescope; look out for foam cores....), and/or simply squeezing the tube in that area; if it flexes more than normal then the structure is weakened, but if it doesn't, it isn't proof that it is OK... It may be possible to get some professional quality NDT done on it but at what cost?

Some manufacturers have a provision in their warranty for such accidental damage arising; they may be able to inspect the frame, or arrange for a replacement at reduced cost.

If you choose to carry on using the frame and/or repairing it, I'd suggest a regular inspection of that region is warranted. I would expect the damaged area not to be airtight before it failed completely; you may be able to use that feature to advantage.

If it were mine I'd be thinking of repair, or at least having it inspected properly, rather than taking the hacksaw to it.

cheers
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JohnW
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Re: Ouch!!

Postby JohnW » 25 Sep 2014, 5:57pm

foxyrider wrote:
JohnW wrote: Can you say with certainty that the OP's frame is safe?


No i can't but that only proves i'm not a CF technician, neither can you categorically say its not for the same reason.......................


...........oh - absolutely foxy, indeed I can't, and we can only say what we'd do in OP's unenviable, situation. It's most unfortunate.

Is that a product of my ignorance - well, yes, certainly, but coloured by my own experience with steel, and the experience of others (including as related on several threads on this forum) with CF.

What I've said, as have several others, is that I would want a CF technician's learned advice before I'd feel safe on that frame. I wouldn't want to be misunderstood as seeking to tell others what to think and what to do.