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-   -   Bent carbon frame? (http://www.cyclebanter.com/showthread.php?t=256086)

[email protected] July 7th 18 08:38 PM

Bent carbon frame?
 
My Scott CR1 has a slight problem in that the Record rear mech collided with a Campag Shamal spoke and damaged both. Cue a new rear mech and a spoke BUT a LBS insisted that the carbon frame is also bent and they won't put it in a jig to straighten it. How can a Carbon stay bend?

TMS320 July 7th 18 10:35 PM

Bent carbon frame?
 
On 07/07/18 20:38, wrote:
My Scott CR1 has a slight problem in that the Record rear mech
collided with a Campag Shamal spoke and damaged both. Cue a new rear
mech and a spoke BUT a LBS insisted that the carbon frame is also
bent and they won't put it in a jig to straighten it. How can a
Carbon stay bend?


Any material has limits. When a carbon frame is damaged it can't be
repaired.


Peter Parry July 8th 18 02:29 PM

Bent carbon frame?
 
On Sat, 7 Jul 2018 12:38:15 -0700 (PDT), wrote:

My Scott CR1 has a slight problem in that the Record rear mech collided with a Campag Shamal spoke and damaged both.
Cue a new rear mech and a spoke BUT a LBS insisted that the carbon frame is also bent and they won't put it in a jig to straighten it.
How can a Carbon stay bend?


Stress any material beyond its elastic limit (yield strength) and it
will deform and stay deformed. You can't bend it straight again..

MrCheerful July 8th 18 02:34 PM

Bent carbon frame?
 
On 08/07/2018 14:29, Peter Parry wrote:
On Sat, 7 Jul 2018 12:38:15 -0700 (PDT), wrote:

My Scott CR1 has a slight problem in that the Record rear mech collided with a Campag Shamal spoke and damaged both.
Cue a new rear mech and a spoke BUT a LBS insisted that the carbon frame is also bent and they won't put it in a jig to straighten it.
How can a Carbon stay bend?


Stress any material beyond its elastic limit (yield strength) and it
will deform and stay deformed. You can't bend it straight again..


thread on the problem he

http://forums.mtbr.com/drivetrain-sh...e-1048540.html

[email protected] July 8th 18 02:46 PM

Bent carbon frame?
 
On Saturday, 7 July 2018 22:35:28 UTC+1, TMS320 wrote:
On 07/07/18 20:38, wrote:
My Scott CR1 has a slight problem in that the Record rear mech
collided with a Campag Shamal spoke and damaged both. Cue a new rear
mech and a spoke BUT a LBS insisted that the carbon frame is also
bent and they won't put it in a jig to straighten it. How can a
Carbon stay bend?


Any material has limits. When a carbon frame is damaged it can't be
repaired.


It is NOT "bent" after all, it's just that THAT particular LBS didn't fance the wheel faffage. A different LBS will fit a new Shamal spoke, a new £80 Centaur rear mech and in the meantime I am riding this Trek.

http://www.simonmason.karoo.net/trek1400.jpg

[email protected] July 8th 18 03:48 PM

Bent carbon frame?
 
On Sunday, 8 July 2018 14:46:11 UTC+1, wrote:
On Saturday, 7 July 2018 22:35:28 UTC+1, TMS320 wrote:
On 07/07/18 20:38, wrote:
My Scott CR1 has a slight problem in that the Record rear mech
collided with a Campag Shamal spoke and damaged both. Cue a new rear
mech and a spoke BUT a LBS insisted that the carbon frame is also
bent and they won't put it in a jig to straighten it. How can a
Carbon stay bend?


Any material has limits. When a carbon frame is damaged it can't be
repaired.


It is NOT "bent" after all, it's just that THAT particular LBS didn't fance the wheel faffage. A different LBS will fit a new Shamal spoke, a new £80 Centaur rear mech and in the meantime I am riding this Trek.

http://www.simonmason.karoo.net/trek1400.jpg


STOP PRESS - It is the Al dropout that is bent and it can be unbent, thankfully.

TMS320 July 8th 18 11:18 PM

Bent carbon frame?
 
On 08/07/18 15:48, wrote:

STOP PRESS - It is the Al dropout that is bent and it can be unbent, thankfully.


Al is not good once elastic limit has been exceeded. Unlike steel. But I
guess that since it is an insert, rather than an integral piece of frame
it is not so critical.

Ian Smith July 9th 18 07:08 AM

Bent carbon frame?
 
On Sun, 08 Jul 2018 14:29:15 +0100, Peter Parry wrote:
On Sat, 7 Jul 2018 12:38:15 -0700 (PDT), wrote:

Cue a new rear mech and a spoke BUT a LBS insisted that the carbon
frame is also bent and they won't put it in a jig to straighten it.
How can a Carbon stay bend?


Stress any material beyond its elastic limit (yield strength) and it
will deform and stay deformed. You can't bend it straight again..


Really.

What do you think the yield stress of, say, a china plate is?
Do you think you can bend that so it stays bent?

And any material bent plastically stays bent forever. Hmm.

regards, Ian SMith
--
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MrCheerful July 9th 18 08:02 AM

Bent carbon frame?
 
On 09/07/2018 07:08, Ian Smith wrote:
On Sun, 08 Jul 2018 14:29:15 +0100, Peter Parry wrote:
On Sat, 7 Jul 2018 12:38:15 -0700 (PDT), wrote:

Cue a new rear mech and a spoke BUT a LBS insisted that the carbon
frame is also bent and they won't put it in a jig to straighten it.
How can a Carbon stay bend?


Stress any material beyond its elastic limit (yield strength) and it
will deform and stay deformed. You can't bend it straight again..


Really.

What do you think the yield stress of, say, a china plate is?
Do you think you can bend that so it stays bent?

And any material bent plastically stays bent forever. Hmm.

regards, Ian SMith


a broken plate IS deformed. everything has a certain limit of
flexibility, even china. once that limit is reached, damage occurs,
either it stays bent or breaks.

[email protected] July 9th 18 10:34 AM

Bent carbon frame?
 
On Sunday, 8 July 2018 23:18:39 UTC+1, TMS320 wrote:
On 08/07/18 15:48, wrote:

STOP PRESS - It is the Al dropout that is bent and it can be unbent, thankfully.


Al is not good once elastic limit has been exceeded. Unlike steel. But I
guess that since it is an insert, rather than an integral piece of frame
it is not so critical.


The carbon bits of the frame end at the wheel dropouts which are aluminium. It is only the rear mech hanger bit which is bent so it can be gently eased back which is good news.

Here is a Carbon frame that has been in a real crash - as can be seen, they don't really bend as such.

https://pbs.twimg.com/media/Dhp1wzMWsAIcMUf.jpg



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