Is my frame okay still?

cyclingnolycra
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Is my frame okay still?

Postby cyclingnolycra » Mon Aug 20, 2018 9:47 pm

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I had a crash last week, wasn't too serious (just me hitting pavement/kerb, no other vehicles involved). Front wheel out of true, and later today I found a chip in the frame. Odd given that I thought only me + tyres hit the ground (and possibly right hand pedal). It looks more than just a superficial chip, but it's small and I doubt its an issue and I was just going to paint over it with clear nail polish remover...

Am I just being blaise and naïve? Do you guys think this is serious? (Carbon frame)

Thanks for advice!

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Duck!
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Re: Is my frame okay still?

Postby Duck! » Mon Aug 20, 2018 11:06 pm

It's most probably OK, just observe and see if it progresses at all, and if it does get it repaired.
I had a thought, but it got run over as it crossed my mind.

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OnTrackZeD
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Re: Is my frame okay still?

Postby OnTrackZeD » Tue Aug 21, 2018 8:49 am

cyclingnolycra wrote: Do you guys think this is serious? (Carbon frame)



Yes. Carbon can break in an instant. Its not like metal which bends first giving a warning it snaps with no warning.

Have it repair or bin it, these are your only safe choices.

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Duck!
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Re: Is my frame okay still?

Postby Duck! » Tue Aug 21, 2018 9:07 am

OnTrackZeD wrote:
cyclingnolycra wrote: Do you guys think this is serious? (Carbon frame)

Yes. Carbon can break in an instant.

Only if it takes a big enough hit to break the millions of fibres in one go. If it doesn't completely break at the moment of impact it won't just randomly do so at a later point. IF carbon degrades fom a small ding like this, it will do so in a progressive manner. The layup of the fibres is self-reinforcing to an extent, with different layers laid in different directions to take different stresses.
I had a thought, but it got run over as it crossed my mind.

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ValleyForge
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Re: Is my frame okay still?

Postby ValleyForge » Tue Aug 21, 2018 2:34 pm

A gentle sand and some white nail polish when completely dry and it will look as good as new.

BTW what brand?

And I've said it before, but Frameskin is your friend.
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cyclingnolycra
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Re: Is my frame okay still?

Postby cyclingnolycra » Tue Aug 21, 2018 10:07 pm

Thanks for the help guys.
Merida Scultura 4000 (2015).

So nail polish is a good idea? I've had some conflicting advice about it.

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Duck!
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Re: Is my frame okay still?

Postby Duck! » Tue Aug 21, 2018 10:57 pm

Or go to a hobby shop & pick up a small tin of enamel paint.. Put a small but identifiable mark at the current extent of the damage as a reference point, and observe to see if it grows.

I rode a cracked carbon MTB frame for 18 months before repairing it, and the damage didn't grow in that time. It's only when I put a matching ding in the other side of the tube I figured I'd better patch it. I'm still riding it, and it's fine.

I did also break the handlebar some months after the crash that did the second ding in the frame. It went soft and wobbly, but did not completely snap, and I safely, but carefully, rode several kilometres back to the trailhead, mostly uphill.
I had a thought, but it got run over as it crossed my mind.

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WyvernRH
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Re: Is my frame okay still?

Postby WyvernRH » Wed Aug 22, 2018 9:46 am

I can't comment if your frame is safe or not but I think the 'carbon fails quickly and massively' ideas come from the very early days of composites being used in the bicycle industry when the manufacturers hasn't got a good understanding of how to use the new material. Dunno why, it had been in use in aerospace and engineering generally for years. Manufacturers today have computer stress modelling and a good undrstanding iof layup techniques to put cross weaves and mass where it is needed.

It did happen back in the early days, I saw a pair of carbon forks basically fracture and tear apart at the end of a bumpy time trial tossing the rider to the ground. However that was so long ago I can't really remember exactly when it was; late 70's or early 80's maybe.
Still I would back a composite frame any day against an aluminium frame for safe failure modes. Aluminium gives very little notice before it fails totally, especially in high stress areas like forks (seen that happen as well...)

Richard

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Re: Is my frame okay still?

Postby Comedian » Wed Aug 22, 2018 5:21 pm

Duck! wrote:
OnTrackZeD wrote:
cyclingnolycra wrote: Do you guys think this is serious? (Carbon frame)

Yes. Carbon can break in an instant.

Only if it takes a big enough hit to break the millions of fibres in one go. If it doesn't completely break at the moment of impact it won't just randomly do so at a later point. IF carbon degrades fom a small ding like this, it will do so in a progressive manner. The layup of the fibres is self-reinforcing to an extent, with different layers laid in different directions to take different stresses.


Unless the damage acts as a stress riser. In which case it could fail catastrophically. There are very few areas on a bicycle that aren't stressed to some extent. You can't say just looking at it what has happened inside. You might have lost 20% of the load bearing material..

There is no way that would be allowed in any kind of a load bearing area in aviation. If it were more minor than that then they might allow it to operat without repair - it would have to be properly inspected and maybe tested. And it would be put on watch.

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OnTrackZeD
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Re: Is my frame okay still?

Postby OnTrackZeD » Thu Aug 23, 2018 10:02 am

Comedian wrote:
Duck! wrote:
OnTrackZeD wrote:Yes. Carbon can break in an instant.

Only if it takes a big enough hit to break the millions of fibres in one go. If it doesn't completely break at the moment of impact it won't just randomly do so at a later point. IF carbon degrades fom a small ding like this, it will do so in a progressive manner. The layup of the fibres is self-reinforcing to an extent, with different layers laid in different directions to take different stresses.


Unless the damage acts as a stress riser. In which case it could fail catastrophically. There are very few areas on a bicycle that aren't stressed to some extent. You can't say just looking at it what has happened inside. You might have lost 20% of the load bearing material..

There is no way that would be allowed in any kind of a load bearing area in aviation. If it were more minor than that then they might allow it to operat without repair - it would have to be properly inspected and maybe tested. And it would be put on watch.


Yes don't take our word for it, listen to an expert tester and repairer of carbon bikes.

https://www.youtube.com/watch?v=j-SFAB_ ... YF09P-t2fY

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Ivanerrol
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Re: Is my frame okay still?

Postby Ivanerrol » Thu Aug 23, 2018 9:12 pm

WyvernRH wrote:I can't comment if your frame is safe or not but I think the 'carbon fails quickly and massively' ideas come from the very early days of composites being used in the bicycle industry when the manufacturers hasn't got a good understanding of how to use the new material. Dunno why, it had been in use in aerospace and engineering generally for years. Manufacturers today have computer stress modelling and a good undrstanding iof layup techniques to put cross weaves and mass where it is needed.

It did happen back in the early days, I saw a pair of carbon forks basically fracture and tear apart at the end of a bumpy time trial tossing the rider to the ground. However that was so long ago I can't really remember exactly when it was; late 70's or early 80's maybe.
Still I would back a composite frame any day against an aluminium frame for safe failure modes. Aluminium gives very little notice before it fails totally, especially in high stress areas like forks (seen that happen as well...)

Richard


There's a man in my area who repairs carbon bikes. He was previously employed by Boeing in their Carbon fibre department.
His quote: There is no comparison between the aerospace industry and their work with carbon fibre compared to the bicycle industry.
The aero industries quality control is second to none - it has to be. The Asian bicycle manufacturers quality control is less than stellar.
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ironhanglider
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Re: Is my frame okay still?

Postby ironhanglider » Thu Aug 23, 2018 10:57 pm

Never mind the frame, how's the front brake?

This sort of damage is usually caused by the front brake smacking into the frame, bending the upper arm in the process.

Cheers,

Cameron
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cyclingnolycra
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Re: Is my frame okay still?

Postby cyclingnolycra » Fri Aug 24, 2018 12:32 pm

Oh! So the wheel twisted around and front brake smacked into frame during the crash?
That would make a lot of sense actually given that I'm fairly sure the frame itself didn't touch the ground in the crash.

I had to re-adjust the front brake to ensure it was symmetric either side of the spare wheel that I was using. One of the pads toes in a bit more than the other but otherwise the brake is functioning well, was able to go for a 50km ride yesterday.

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Re: Is my frame okay still?

Postby Comedian » Fri Aug 24, 2018 1:11 pm

ironhanglider wrote:Never mind the frame, how's the front brake?

This sort of damage is usually caused by the front brake smacking into the frame, bending the upper arm in the process.

Cheers,

Cameron

Yep.. first thing I thought when I saw that. Right side and all. Would be interesting to see if the bars whacked the TT too. Somethings bend and can hit when they are under load.

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