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?

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.

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..

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

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

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.

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.

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
--
|\ /| no .sig
|o o|
|/ \|

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.

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

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?

He didn't say "bent". He said "deformed". A stressed china plate will
certainly be that.

And any material bent plastically stays bent forever. Hmm.

Maybe.

PS: You can learn something every day. "Plastically" was a new one on
me, but there are 636,000 instances of it on UK Google. Thanks for that.

Bent carbon frame?
 

On Monday, 9 July 2018 07:08:32 UTC+1, 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?

Doesn't every material have an "elastic limit"?
After that it snaps, not deforms.

Bent carbon frame?
 

On 09/07/18 10:51, wrote:

Doesn't every material have an "elastic limit"?
After that it snaps, not deforms.

Every material has an elastic limit and a breaking strength. The
difference can go from nothing (china) to something very substantial
(steel).

It can also be directional. So concrete works under compression but not
under tension, carbon fibre works under tension but not compression.
Hence concrete usually has steel reinforcement and carbon fibres are
used in composites. Wood and steel can be used in both directions.

Steel work hardens after its elastic limit is reached and after the
excess load has been removed keeps its original strength. Work hardening
takes energy, making it good for crash absorption. Aluminium has little
or no work hardening.

Under cyclic loads below their elastic limit materials also have a
fatigue life: it is possible to design a steel part to never fail;
aluminium and concrete always have an end life.

Bent carbon frame?
 

On 09/07/2018 15:37, TMS320 wrote:

On 09/07/18 10:51, wrote:

Doesn't every material have an "elastic limit"?
After that it snaps, not deforms.

Every material has an elastic limit and a breaking strength. The
difference can go from nothing (china) to something very substantial
(steel).

It can also be directional. So concrete works under compression but not
under tension, carbon fibre works under tension but not compression.
Hence concrete usually has steel reinforcement and carbon fibres are
used in composites. Wood and steel can be used in both directions.

Steel work hardens after its elastic limit is reached and after the
excess load has been removed keeps its original strength. Work hardening
takes energy, making it good for crash absorption. Aluminium has little
or no work hardening.

Under cyclic loads below their elastic limit materials also have a
fatigue life: it is possible to design a steel part to never fail;
aluminium and concrete always have an end life.

The much-maligned Wikipedia is very useful, isn't it?

Bent carbon frame?
 

On Monday, 9 July 2018 15:37:30 UTC+1, TMS320 wrote:
On 09/07/18 10:51, wrote:

Doesn't every material have an "elastic limit"?
After that it snaps, not deforms.

Every material has an elastic limit and a breaking strength. The
difference can go from nothing (china) to something very substantial
(steel).

It can also be directional. So concrete works under compression but not
under tension, carbon fibre works under tension but not compression.
Hence concrete usually has steel reinforcement and carbon fibres are
used in composites. Wood and steel can be used in both directions.

Steel work hardens after its elastic limit is reached and after the
excess load has been removed keeps its original strength. Work hardening
takes energy, making it good for crash absorption. Aluminium has little
or no work hardening.

Under cyclic loads below their elastic limit materials also have a
fatigue life: it is possible to design a steel part to never fail;
aluminium and concrete always have an end life.

The dropouts on my 2011 Scott CR1 conduct electricity and are aluminium. I believe the 2018 ones are all carbon.

Bent carbon frame?
 

On 09/07/18 15:42, JNugent wrote:

The much-maligned Wikipedia is very useful, isn't it?

Is this your second source of information (after this newsgroup) for
your in depth knowledge of modern cyclists?

Bent carbon frame?
 

On Mon, 9 Jul 2018 02:51:24 -0700 (PDT), wrote:
On Monday, 9 July 2018 07:08:32 UTC+1, 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?

Doesn't every material have an "elastic limit"?

Most materials have a limit to elastic behaviour. They don't all
yield when they reach it - some are almost perfectly elastic until the
point where they shatter into thousands of pieces. A dinner plate
doesn't reach a iield strnegth, then deform and stay defomred -
doesn't "deform", it shatters.

Many materials that do yield don't have a yield 'point' - even
relatively common stuff like stainless steel doesn't have a defined
yield point - it doesn't exhibit a pure elastic behaviour except at
infinitesimal strains.

regards, Ian SMith
--
|\ /| no .sig
|o o|
|/ \|

Bent carbon frame?
 

On 09/07/2018 17:37, TMS320 wrote:

On 09/07/18 15:42, JNugent wrote:

The much-maligned Wikipedia is very useful, isn't it?

Is this your second source of information (after this newsgroup) for
your in depth knowledge of modern cyclists?

It was not I who quoted that site.

Bent carbon frame?
 

On 10/07/18 01:05, JNugent wrote:
On 09/07/2018 17:37, TMS320 wrote:
On 09/07/18 15:42, JNugent wrote:

The much-maligned Wikipedia is very useful, isn't it?

Is this your second source of information (after this newsgroup) for
your in depth knowledge of modern cyclists?

It was not I who quoted that site.

Nor did I. Has it got much to say about evil cyclists?

Bent carbon frame?
 

On Monday, July 9, 2018 at 2:34:46 AM UTC-7, wrote:
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

Shortly after 9/11 a sub contractor tried to repair a carbon wing or tail section like it was a surfboard ding. Apparently composite materials in modern commercial air craft is a little more complicated than that. The air liner crashed in NY City killing all on board. The NTSB & FAA were really good telling everyone it wasn't terrorism so don't worry about it.

If you do the same thing with a damaged carbon bike frame, be careful when you first try it out. Don't start off pegging curbs, pot holes, RR tracks, etc.

Bent carbon frame?
 

On 10/07/2018 07:43, TMS320 wrote:
On 10/07/18 01:05, JNugent wrote:
On 09/07/2018 17:37, TMS320 wrote:
On 09/07/18 15:42, JNugent wrote:

The much-maligned Wikipedia is very useful, isn't it?

Is this your second source of information (after this newsgroup) for
your in depth knowledge of modern cyclists?

It was not I who quoted that site.

Nor did I. Has it got much to say about evil cyclists?

How should I know?

Bent carbon frame?
 

On Tuesday, 10 July 2018 09:18:47 UTC+1, Bret Cahill wrote:


If you do the same thing with a damaged carbon bike frame, be careful when you first try it out. Don't start off pegging curbs, pot holes, RR tracks, etc.

It is OK now - it was just a bent Aluminium dropout lug which is bonded to the Carbon frame. A bit like a bent saucepan, I suppose.