Crank about to break?

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

Jim Rogers wrote:
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"
wrote:

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 wrote:

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 writes:

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?

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

wrote in message
oups.com...

Jim Rogers wrote:

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


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" wrote in message
ups.com...
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


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

I know little about metalurgy...

Including how to spell it!

--Jim

Jim Rogers wrote:
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