Crank about to break?

Jim Rogers said:

I bought some used older (~94) Campy Chorus cranks 2 years ago and
didn't notice any problems with them when I installed them. I've ridden
~2,000 miles on these cranks and weigh 225.

Yesterday I was switching them to another bike and noticed a problem on
the left one. I don't know how to tell if this is just a scratch or a
crack. Here are a couple of pictures:

http://pg.photos.yahoo.com/ph/irene_r_1999/my_photos

Is that crank safe to use?

--Jim Rogers

Looks like the chain came off one time and scratched the surface of the
crank arm..............hang on though...left crank arm..........don't
know what may have caused that, but I doubt it would have affected the
integrity of the crank arm. Maybe a tool mark from some one trying to
tighten the bb.

Laters,

marz

On 23 Nov 2006 10:28:11 -0800, "Jim Rogers" <[email hidden]>

Quoted message said:

I bought some used older (~94) Campy Chorus cranks 2 years ago and
didn't notice any problems with them when I installed them. I've ridden
~2,000 miles on these cranks and weigh 225.

Yesterday I was switching them to another bike and noticed a problem on
the left one. I don't know how to tell if this is just a scratch or a
crack. Here are a couple of pictures:

http://pg.photos.yahoo.com/ph/irene_r_1999/my_photos

Is that crank safe to use?

It looks like a nick from something that got out of polace while the
crank was in motion. I doubt that it will cause a failure, but if
you're nervous about it, polishing the scratch to the point at which
it has no sharp points or edges should reduce the tendency of the mark
to act as a stress riser. Of course, that will remove a bunch of the
anodizing in the area, but there are always tradeoffs in a situation
like this.

I'd ignore it if it was mine.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Jim Rogers said:

http://pg.photos.yahoo.com/ph/irene_r_1999/my_photos

Is that crank safe to use?

http://materials.open.ac.uk/mem/mem_ccf.htm

Looks like cracks lead away from the damaged area on both sides in your
pics, but I'm not sure.

Why take a chance? Your first five minutes in the ER will cost way more
than a new crank, or replacement arm. Check ebay for an NOS
replacement, doesn't have to match to work <g>. --D-y

Jim Rogers said:

I bought some used older (~94) Campy Chorus cranks 2 years ago and
didn't notice any problems with them when I installed them. I've
ridden ~2,000 miles on these cranks and weigh 225.

Quoted message said:

Yesterday I was switching them to another bike and noticed a problem
on the left one. I don't know how to tell if this is just a scratch
or a crack. Here are a couple of pictures:

http://pg.photos.yahoo.com/ph/irene_r_1999/my_photos

Quoted message said:

Is that crank safe to use?

That doesn't look like a crack but rather a gouge from something that
got in between crank and BB while it was turning, the nick being
circular about the center of rotation. Stress cracks don't do that,
so I see no reason for concern. If you have the crank in your hand,
take a magnifier and look for cracks under good lighting if you think
this has been this way for many miles.

Jobst Brandt

<[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Jim Rogers said:

http://pg.photos.yahoo.com/ph/irene_r_1999/my_photos

Is that crank safe to use?

http://materials.open.ac.uk/mem/mem_ccf.htm

Looks like cracks lead away from the damaged area on both sides in

your

Quoted message said:

pics, but I'm not sure.

Why take a chance? Your first five minutes in the ER will cost way

more

Quoted message said:

than a new crank, or replacement arm. Check ebay for an NOS
replacement, doesn't have to match to work <g>. --D-y

That's a great web site. I like this area showing Carbon Fiber Composite
failures:

http://materials.open.ac.uk/mem/mem_comp.htm

Judging from the width and depth of the fissure the damage appears to be
more than just a simple surface crack. When I looked at the first
picture it looked like a chain scratch - but this is the left hand crank
arm. I copied both pictures and enlarged them in a file viewer. The
second picture shows the smoking gun.

It appears to be lap failure or delamination caused by rolled over metal
that did not weld into the parent metal during the billet making or
forging process.

I'd yank that crank NOW! There's no telling when it WILL fail.

Chas.

"Jim Rogers" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I bought some used older (~94) Campy Chorus cranks 2 years ago and
didn't notice any problems with them when I installed them. I've

ridden

Quoted message said:

~2,000 miles on these cranks and weigh 225.

Yesterday I was switching them to another bike and noticed a problem

on

Quoted message said:

the left one. I don't know how to tell if this is just a scratch or a
crack. Here are a couple of pictures:

http://pg.photos.yahoo.com/ph/irene_r_1999/my_photos

Is that crank safe to use?

--Jim Rogers

Judging from the width and depth of the fissure the damage appears to be
more than just a simple surface crack. When I looked at the first
picture it looked like a chain scratch - but this is the left hand crank
arm. I copied both pictures and enlarged them in a file viewer. The
second picture shows the smoking gun.

It appears to be lap failure or delamination caused by rolled over metal
that did not weld into the parent metal during the billet making or
forging process.

You could file the area with a small round file and see if there is a
larger void below the surface.

I'd yank that crank NOW! There's no telling when it WILL fail.

Chas.

I added a few more photos (use the same link).

The first two show a crack/gouge/scratch/something that goes all the
way around the end. I don't know if you can see it in the picture, but
it does hook up the the mark I originally showed.

Also, the last picture shows another scratch/crack that I didn't notice
before (it is toward the left side). Is that a crack or a scratch?

I know little about metalurgy and old cranks have lots of blemishes.
How does one know which are serious?

--Jim

Quoted message said:

I know little about metalurgy...

Including how to spell it!

--Jim

Jim Rogers said:

I added a few more photos (use the same link).

The first two show a crack/gouge/scratch/something that goes all the
way around the end. I don't know if you can see it in the picture, but
it does hook up the the mark I originally showed.

Also, the last picture shows another scratch/crack that I didn't notice
before (it is toward the left side). Is that a crack or a scratch?

I know little about metalurgy and old cranks have lots of blemishes.
How does one know which are serious?

In that link I posted, take a look at the Nuovo Record crank that
failed. You can click on the photos to see enlargements that show the
"beach marks".

I can't say that's what's happening with yours, but again, why take the
chance? Especially in light of the additional problems shown in your
added photos. --D-y

<[email hidden]> wrote: in message
news:[email hidden]...

Quoted message said:

Jim Rogers said:

I bought some used older (~94) Campy Chorus cranks 2 years ago and
didn't notice any problems with them when I installed them. I've
ridden ~2,000 miles on these cranks and weigh 225.

Quoted message said:

Yesterday I was switching them to another bike and noticed a problem
on the left one. I don't know how to tell if this is just a scratch
or a crack. Here are a couple of pictures:

http://pg.photos.yahoo.com/ph/irene_r_1999/my_photos

Quoted message said:

Is that crank safe to use?

That doesn't look like a crack but rather a gouge from something that
got in between crank and BB while it was turning, the nick being
circular about the center of rotation. Stress cracks don't do that,
(clip)

^^^^^^^^^^^^^^^
Also supporting this view is the fact that the mark appears and disappears
at various places around the crank. This is consistent with some outside
object coming in contact while the crank is rotatintg. It is hard to
imagine a fatigue crack inside the metal surfacing in various places at the
same time, without already having produced total failure.

There is a test method called "Dye-check," which you might be able to
improvise in the kitchen. Soak ink around the area. Wipe it off. Sprinkle
on some flour or baking powder, and see whether ink comes out of the
"cracks." If it does, throw away the crank.

Jim Rogers said:

I added a few more photos (use the same link).

Quoted message said:

The first two show a crack/gouge/scratch/something that goes all the
way around the end. I don't know if you can see it in the picture,
but it does hook up the the mark I originally showed.

Quoted message said:

Also, the last picture shows another scratch/crack that I didn't
notice before (it is toward the left side). Is that a crack or a
scratch?

Quoted message said:

I know little about metallurgy and old cranks have lots of
blemishes. How does one know which are serious?

Well if it is a scratch, then there must be upset (raised) material
adjacent to the gouge, as in plowing, but I see none. Therefore, this
flaw was there from manufacture. If it is initiating structural
rather than cosmetic damage, you should be able to see a crack.
Without a closeup, I can't see any growing damage in your pictures.

Crank are generally finished with clear alodine or similar surface
treatment that readily expose cracks under careful inspection. That's
why I suggested inspecting with good lighting and a magnifier. Im
fairly sure this is a manufacturing flaw.

Jobst Brandt

[email hidden] wrote:
?

Quoted message said:

Well if it is a scratch, then there must be upset (raised) material
adjacent to the gouge, as in plowing, but I see none. Therefore, this
flaw was there from manufacture. If it is initiating structural
rather than cosmetic damage, you should be able to see a crack.
Without a closeup, I can't see any growing damage in your pictures.

I was looking for the raised area too, but saw none. I think the pix
aren't good enough to deliver a firm opinion, but it may be a simple
scratch done long enough ago to have worn down the raised area. For
example, a few brushes with a shoe would buff down the raised area of a
scratch.

Were it my crank, I'd vise and then stress it to see if the whatever
widens.

-paul

Paul Cassel said:

Quoted message said:

Well if it is a scratch, then there must be upset (raised) material
adjacent to the gouge, as in plowing, but I see none. Therefore,
this flaw was there from manufacture. If it is initiating
structural rather than cosmetic damage, you should be able to see a
crack. Without a closeup, I can't see any growing damage in your
pictures.

Quoted message said:

I was looking for the raised area too, but saw none. I think the
pix aren't good enough to deliver a firm opinion, but it may be a
simple scratch done long enough ago to have worn down the raised
area. For example, a few brushes with a shoe would buff down the
raised area of a scratch.

Quoted message said:

Were it my crank, I'd vise and then stress it to see if the whatever
widens.

I don't think there is enough of a crack to reveal opening. That's
the problem with cranks. There is no warning other than sound when
water gets in the crack. Besides, you can't get to that part of the
crank with any part of a shoe top polish it. The pictures show me an
otherwise unblemished original surface finish.

Jobst Brandt

Jim Rogers said:

Yesterday I was switching them to another bike and noticed a problem on
the left one. I don't know how to tell if this is just a scratch or a
crack. Here are a couple of pictures:
http://pg.photos.yahoo.com/ph/irene_r_1999/my_photos
Is that crank safe to use?

To me it appears as a mark left there to disassemble it.
I would not worry at all.

Sergio
Pisa

Quoted message said:

I don't think there is enough of a crack to reveal opening. That's
the problem with cranks. There is no warning other than sound when
water gets in the crack. Besides, you can't get to that part of the
crank with any part of a shoe top polish it. The pictures show me an
otherwise unblemished original surface finish.

Jobst Brandt

It is unlikely that if it is a crack it will fail in the next few
rides- why not spray a flat black paint on the area put it on and use
it ? the flat black should show if it is a widening or lengthening
crack- perhaps at a glance while riding or upon closer inspection and
wear off fairly easily over a short time if everything seems ok

"Jim Rogers" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I added a few more photos (use the same link).

The first two show a crack/gouge/scratch/something that goes all the
way around the end. I don't know if you can see it in the picture, but
it does hook up the the mark I originally showed.

Also, the last picture shows another scratch/crack that I didn't

notice

Quoted message said:

before (it is toward the left side). Is that a crack or a scratch?

I know little about metalurgy and old cranks have lots of blemishes.
How does one know which are serious?

--Jim

After enlarging the additional pics, it really appears to be fold/lap
failure/delamination. These kinds of failures result from a forging fold
which is a discontinuity in the material resulting from the metal
folding over onto itself during the forging process. This can also
happen during billet production. Notice how the defects seem to wrap
around the raised axle boss at the same plane. They don't look like a
normal stress crack.

I saw a picture on the internet of a crank that failed from this kind of
problem. The link was posted in a message in this NG not long ago but I
haven't been able to find it. The crank arm splintered in layers around
the axle hole parallel to the length of the arm. The crank arm didn't
crack in half like those pictured at this site:

http://materials.open.ac.uk/mem/mem_ccf4.htm

With this kind of failure mechanism the crank arm is less likely to
catastrophically fail in a manner that can happen with a stress crack
where the arm breaks completely off.

It may last without any additional problems but picture yourself out of
the saddle honking up a hill and the left crank arm starts to fail. Are
you going to be able to recover and come to a safe stop? Is the
uncertainty worth the $100 or so USDs that it would cost to replace the
crank?

Here's some definitions:

"Fold -- A forging or casting discontinuity caused by metal folding back
on its own surface during flow in the die or mold cavity."

http://www.kaiseral.com/glossary_f.htm

"Lamination -- An abnormal structure resulting in a separation or
weakness aligned generally parallel to the worked surface of the metal.

Lap -- A surface defect, appearing as a seam, caused by fording over hot
metal, fins, or sharp corners and then rolling or forging them into the
surface, but not welding them."

http://www.kaiseral.com/glossary_l.htm

Chas.

Thank you all for your comments on my crank. I think there is enough
doubt that I went ahead and used a different crank. Better safe than
sorry I think.

Even though I won't be using this crank, I'm still curious about it and
would like to learn more. Is there anywhere I could send it to be
looked at for a professional diagnosis?

Or, would any of you be willing to look at it? I would mail it to you
with a postage-paid return envelope. You can email me off-list if
interested.

Either way, thanks again for all of the input.

--Jim

In article <[email hidden]>,

Jim Rogers said:

I added a few more photos (use the same link).

The first two show a crack/gouge/scratch/something that goes all the
way around the end. I don't know if you can see it in the picture, but
it does hook up the the mark I originally showed.

Also, the last picture shows another scratch/crack that I didn't notice
before (it is toward the left side). Is that a crack or a scratch?

I know little about metalurgy and old cranks have lots of blemishes.
How does one know which are serious?

Jim:

This _first_ (1 of 5) image in your album shows what may be a stray
thread (i.e. dust), a surface scratch (harmless), or a fatigue crack
across the base of the crank. My eye wants the crack to continue to the
nearest corner of the square hole, but I can't say for sure by looking
at this one photo. Can you examine that more closely and confirm what
this is?

--
Bill Bushnell
http://pobox.com/~bushnell/

Quoted message said:

This _first_ (1 of 5) image in your album shows what may be a stray
thread (i.e. dust), a surface scratch (harmless), or a fatigue crack
across the base of the crank. My eye wants the crack to continue to the
nearest corner of the square hole, but I can't say for sure by looking
at this one photo. Can you examine that more closely and confirm what
this is?

If I understand you, you are describing what looks like a crack or
thread at about 2 oclock on the face of the base in photo 1. It angles
down and to the left at about a 45* angle.

If so, that appears to be just a surface scratch.

--Jim