Significant Accident

Terry Morse said:

Quoted message said:

I've posted eight photos of the crank on a private page of the
club's web site:

http://www.ocrebels.com/CrankFailure.htm

Quoted message said:

Hmm. Note what looks like a flaw in the metal at the 9 o'clock
position, surrounded by corrosion:

http://www.ocrebels.com/images/failure/pic7.htm

Quoted message said:

It looks to my untrained eye that this could have been the original
source of the crack. I'm also curious about the shiny section, from
about the 1 o'clock position to the 7 o'clock position. The
polished surface suggests that the fracture was there quite a while,
and the relative movement of the pieces did the polishing.

The smooth region you describe is the area that failed all at once.
The upper part of that picture, the granular part, failed gradually in
fatigue. Motion in such a fracture remains the classically termed
"hairline crack" until rupture. In that crack motion is at best
fretting that may advance oxidation. Hairline crack means only that
the part had not yet separated and is meaningless for that reason.
Such cracks are at times more visible when wet because they emit a
fine slurry of oxide, in aluminum as well as steel.

Quoted message said:

If there are any materials people here, could they comment?

That's the comment.

Jobst Brandt
[email hidden]

Quoted message said:

Terry Morse said:

Quoted message said:

I've posted eight photos of the crank on a private page of the
club's web site:

http://www.ocrebels.com/CrankFailure.htm

Quoted message said:

Hmm. Note what looks like a flaw in the metal at the 9 o'clock
position, surrounded by corrosion:

http://www.ocrebels.com/images/failure/pic7.htm

Quoted message said:

It looks to my untrained eye that this could have been the original
source of the crack. I'm also curious about the shiny section, from
about the 1 o'clock position to the 7 o'clock position. The
polished surface suggests that the fracture was there quite a while,
and the relative movement of the pieces did the polishing.

The smooth region you describe is the area that failed all at once.
The upper part of that picture, the granular part, failed gradually in
fatigue. Motion in such a fracture remains the classically termed
"hairline crack" until rupture. In that crack motion is at best
fretting that may advance oxidation. Hairline crack means only that
the part had not yet separated and is meaningless for that reason.
Such cracks are at times more visible when wet because they emit a
fine slurry of oxide, in aluminum as well as steel.

Quoted message said:

If there are any materials people here, could they comment?

That's the comment.

Jobst Brandt
[email hidden]

Dear Jobst,

"That's the comment."

How fortunate that there is nothing else to be said and no
possibility of error!

Carl Fogel

I'm working on getting photos of the spindle, but it may be infeasible as the
bike is going back to the owner soon. It is known to be at least ten years
old, gone through many, many centuries and doubles, and I'm told (by the
temporary holder) that it might date from the days when Merlin made its own
bottom bracket. The guy is also apparently a Big (300#?) individual.

Jobst or anyone: is there anything the normal rider, not privy to an Xray
crystallography setup, can do to check for incipient failures of this genre?

Art
Temporary usercode - to be deleted when spam starts. Use MyBrainHurts at this ISP to reach me

Arthur Shapiro said:

I'm working on getting photos of the spindle, but it may be
infeasible as the bike is going back to the owner soon. It is known
to be at least ten years old, gone through many, many centuries and
doubles, and I'm told (by the temporary holder) that it might date
from the days when Merlin made its own bottom bracket. The guy is
also apparently a Big (300#?) individual.

That's too bad. I think a good picture of such a failure helps riders
realize that these things break and that there is effectively no
warning.

Quoted message said:

Jobst or anyone: is there anything the normal rider, not privy to an
Xray crystallography setup, can do to check for incipient failures
of this genre?

Especially with a heavy rider, replace the spindle every 20,000 miles
whether it needs it or not. I say that because most of my Campagnolo
spindles failed in the bearing races and didn't last long enough for
this type of failure. When one finally outlasted bearing failure mode
it broke in the taper after about 30,000 miles but that's only a guess
because that spindle survived several right and left failed cranks.

Jobst Brandt
[email hidden]

Sheldon Brown said:

An anonymous poster quoted somebody without attribution:

Quoted message said:

I was under the impression that Shimano and Campagnolo tapers were
significantly different and not compatable.

You're not alone, many people are under this impression.

In my experience, however, it is almost never a problem in practice, if
you make allowance for the desired chainline.

Is there a rule of thumb you use? Something like, "When using a Campa
crank with a Shimano BB subtract X mm from the spec spindle length?"

Pat

Email address works as is.

Dye penetrant testing will make the crack more easily seen. A good auto
machine shop/supplier should have inexpensive kits.

Magna-flux, a bit more expensive, will reveal some flaws below the surface
of the metal.

Neither of these non-destructive tests are effective without some
understanding that may be beyond some here.

A proper visual inspection with understanding, good light, a 5X or 10X glass
and a clean field is a good beginning.

Brandt is usually correct. Note when his critics address side issues,
a.k.a. quibbles.

"Arthur Shapiro" <[email hidden]> wrote in message
news:tvm3d.329400$Oi.272261@fed1read04...

Quoted message said:

I'm working on getting photos of the spindle, but it may be infeasible as
the
bike is going back to the owner soon. It is known to be at least ten
years
old, gone through many, many centuries and doubles, and I'm told (by the
temporary holder) that it might date from the days when Merlin made its
own
bottom bracket. The guy is also apparently a Big (300#?) individual.

Jobst or anyone: is there anything the normal rider, not privy to an Xray
crystallography setup, can do to check for incipient failures of this
genre?

Art
Temporary usercode - to be deleted when spam starts. Use MyBrainHurts at
this ISP to reach me

John Forrest Tomlinson said:

Sheldon Brown said:

An anonymous poster quoted somebody without attribution:

Quoted message said:

<Since then I have used Shimano BB's and spindles, even with my
Campagnolo cranks. That doesn't mean it can't occur again but it
hasn't for a long time.>

and responded:

Quoted message said:

I was under the impression that Shimano and Campagnolo tapers were
significantly different and not compatable.

You're not alone, many people are under this impression.

In my experience, however, it is almost never a problem in practice, if
you make allowance for the desired chainline.

Is it possible to make chainline predictions just from the length of
the spindle?

Probably, if the spindles are precision, which Campy and Shimano are (at least
in the higher end stuff). Specialized also used to make very nice precision
spindles. (Some "for" Campy and some "for" Shimano.)

Quoted message said:

Or are their differences in the diameter of the tapered
section of the axle between the two brands. That is, will a
Campagonolo and Shimano spindle of, say 107mm both result in the same
chainline?

No. But I don't know the specific details -- I've typically done trial and
error rather than predictions.

<jobst.brandt wrote: (clip) The smooth region you describe is the area that
failed all at once. The upper part of that picture, the granular part,
failed gradually in fatigue. (clip)
^^^^^^^^^^^^^^^^
Jobst, I am surprised that a person of your expertese would make this
layman's error. You have it backwards. A typical fatigue failure starts
with a tiny crack, which acts as a stress raiser, causing the crack to
propagate across the metal. During the load cycling, as the crack grows,
there is movement within the crack, which polishes the surfaces on both
sides. When the undamaged metal has dimished in cross section to the point
where it can no longer sustain the load, there is a sudden fracture. The
part that breaks suddenly is not worn--the crystaline surface is the exposed
metal structure. The crystaline structure was there all along.

The idea that vibration, or cyclical stress causes the metal to
"crystalize," making it weaker, is not correct. I am not a metallurgist,
but I did graduate with highest honors from the University of California in
mechical engineering. I mention this only to lend credibility to what I am
saying above.

'Layman's error' or mis-speaking? The body of Jobst's work, compared to
your claimed summa cum laude, earns him the benefit of the doubt.

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

Quoted message said:

<jobst.brandt wrote: (clip) The smooth region you describe is the area
that failed all at once. The upper part of that picture, the granular
part, failed gradually in fatigue. (clip)
^^^^^^^^^^^^^^^^
Jobst, I am surprised that a person of your expertese would make this
layman's error. You have it backwards. A typical fatigue failure starts
with a tiny crack, which acts as a stress raiser, causing the crack to
propagate across the metal. During the load cycling, as the crack grows,
there is movement within the crack, which polishes the surfaces on both
sides. When the undamaged metal has dimished in cross section to the
point where it can no longer sustain the load, there is a sudden fracture.
The part that breaks suddenly is not worn--the crystaline surface is the
exposed metal structure. The crystaline structure was there all along.

The idea that vibration, or cyclical stress causes the metal to
"crystalize," making it weaker, is not correct. I am not a metallurgist,
but I did graduate with highest honors from the University of California
in mechical engineering. I mention this only to lend credibility to what
I am saying above.

Doug Huffman said:

'Layman's error' or mis-speaking? The body of Jobst's work, compared to
your claimed summa cum laude, earns him the benefit of the doubt.

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

Quoted message said:

<jobst.brandt wrote: (clip) The smooth region you describe is the area
that failed all at once. The upper part of that picture, the granular
part, failed gradually in fatigue. (clip)
^^^^^^^^^^^^^^^^
Jobst, I am surprised that a person of your expertese would make this
layman's error. You have it backwards. A typical fatigue failure starts
with a tiny crack, which acts as a stress raiser, causing the crack to
propagate across the metal. During the load cycling, as the crack grows,
there is movement within the crack, which polishes the surfaces on both
sides. When the undamaged metal has dimished in cross section to the
point where it can no longer sustain the load, there is a sudden fracture.
The part that breaks suddenly is not worn--the crystaline surface is the
exposed metal structure. The crystaline structure was there all along.

The idea that vibration, or cyclical stress causes the metal to
"crystalize," making it weaker, is not correct. I am not a metallurgist,
but I did graduate with highest honors from the University of California
in mechical engineering. I mention this only to lend credibility to what
I am saying above.

Dear Doug,

I imagine that Jobst receives the same benefit of the doubt
and general good will that he exercises--or better.

Carl Fogel

Leo Lichtman said:

The idea that vibration, or cyclical stress causes the metal to
"crystalize," making it weaker, is not correct. I am not a metallurgist,
but I did graduate with highest honors from the University of California in
mechical engineering. I mention this only to lend credibility to what I am
saying above.

When I see "University of California" all by itself like that I think
Berkeley, and ISTR that the college of engineering at Berkeley does
not award honors. Maybe I am remembering incorrectly, or maybe you
graduated from a different campus. I don't mean to question your
statement, it just looked funny when I read it.

We all are not 'equal'. You're how old? Ridden how many miles? Written
how many books on bicycle engineering? And you're not even 'Leo' but a
spoiler not even susceptible to peer review, speaking of 'honors'.

Children are better seen than heard - so to write. Your 'Dear' is
disingenuous. I'd rather be right than nice.

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

Quoted message said:

Doug Huffman said:

'Layman's error' or mis-speaking? The body of Jobst's work, compared to
your claimed summa cum laude, earns him the benefit of the doubt.

Dear Doug,

I imagine that Jobst receives the same benefit of the doubt
and general good will that he exercises--or better.

Carl Fogel

Doug Huffman said:

We all are not 'equal'. You're how old? Ridden how many miles? Written
how many books on bicycle engineering? And you're not even 'Leo' but a
spoiler not even susceptible to peer review, speaking of 'honors'.

Children are better seen than heard - so to write. Your 'Dear' is
disingenuous. I'd rather be right than nice.

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

Quoted message said:

Doug Huffman said:

'Layman's error' or mis-speaking? The body of Jobst's work, compared to
your claimed summa cum laude, earns him the benefit of the doubt.

Dear Doug,

I imagine that Jobst receives the same benefit of the doubt
and general good will that he exercises--or better.

Carl Fogel

Dear Doug,

I imagine that you receive the same benefit of the doubt and
general good will that you exercise--or better.

Carl Fogel

I've just been told it was a Phil Wood BB.

Art

"Jim Smith" <[email hidden]> wrote: When I see "University of
California" all by itself like that I think Berkeley, and ISTR that the
college of engineering at Berkeley does not award honors. Maybe I am
remembering incorrectly, or maybe you graduated from a different campus. I
don't mean to question your statement, it just looked funny when I read it.
^^^^^^^^^^^^
This discussion ought to be about the content and correctness of the points
in the discussion, not about whether to believe Jobst or me based on our
status or prestige. Isn't there a metallurgist or materials engineer in the
group who can jump in here?

But, not questioning my credentials, you have still called them into
question. I graduated with highest honors from the University of California,
Berkeley, in 1952. This was awarded by the university, not the College of
Engineering, as far as I can recall. However, I don't believe that is the
issue, and I don't think we should make it that.

Leo Lichtman said:

"Jim Smith" <[email hidden]> wrote: When I see "University of
California" all by itself like that I think Berkeley, and ISTR that the
college of engineering at Berkeley does not award honors. Maybe I am
remembering incorrectly, or maybe you graduated from a different campus. I
don't mean to question your statement, it just looked funny when I read it.
^^^^^^^^^^^^
This discussion ought to be about the content and correctness of the points
in the discussion, not about whether to believe Jobst or me based on our
status or prestige. Isn't there a metallurgist or materials engineer in the
group who can jump in here?

But, not questioning my credentials, you have still called them into
question. I graduated with highest honors from the University of California,
Berkeley, in 1952. This was awarded by the university, not the College of
Engineering, as far as I can recall. However, I don't believe that is the
issue, and I don't think we should make it that.

Let's say you graduated with a GPA of
2.0; would your analysis be any
different? I think not.

"Richard Tack" wrote: Let's say you graduated with a GPA of 2.0; would
your analysis be any different? I think not.
^^^^^^^^^^^^^^^^
I hope not. I guess I made a mistake in trying to build up my credibility
by referring to my education. I know that Jobst Brandt commands a lot of
respect, and I am at a disadvantage in this discussion. But, does that
change the metallurgical truth? I think not. So lets talk about that
instead.

Leo Lichtman said:

Quoted message said:

The smooth region you describe is the area that failed all at
once. The upper part of that picture, the granular part, failed
gradually in fatigue.

Quoted message said:

Jobst, I am surprised that a person of your expertese would make
this layman's error.

I hope you can contain your emotions and wonderment but let's get to
the root of your contentions.

Quoted message said:

You have it backwards. A typical fatigue failure starts with a tiny
crack, which acts as a stress raiser, causing the crack to propagate
across the metal.

Fatigue doesn't have to have an initiating flaw such as a "tiny crack",
it initiates a tiny crack, one that subsequently grows.

Quoted message said:

During the load cycling, as the crack grows, there is movement
within the crack, which polishes the surfaces on both sides. When
the undamaged metal has dimished in cross section to the point where
it can no longer sustain the load, there is a sudden fracture. The
part that breaks suddenly is not worn--the crystaline surface is the
exposed metal structure. The crystaline structure was there all
along.

I think you'll find that forced ruptures tear across crystal planes
and even smear metal in shear failures, which this one partly is. The
fatigue failure tears the metal apart on crystal planes until there is
insufficient structure remaining to withstand a forced rupture.

Quoted message said:

The idea that vibration, or cyclical stress causes the metal to
"crystalize," making it weaker, is not correct.

Thanks for the quote. I have written about this on several occasions.
However, the claim that a failed axle on a car was too old and
crystallized came about from mechanics, untrained in metallurgy, who
made this analysis. It was common in my youth, when Ford rear axles
were poorly designed with a long conical taper with a flat keyway the
length of the taper. They had classic fatigue failures that initiated
along the keyway and finally sheared at 45 degrees in a helical
torsion failure. The fatigue crack was crystalline and usually dirty.

Quoted message said:

I am not a metallurgist, but I did graduate with highest honors from
the University of California in mechical engineering. I mention
this only to lend credibility to what I am saying above.

That's too bad. You should write your responses so that they rest on
their own merit rather than who said it. That's a basic flaw in an
uneducated world. People are unable to decide what is correct and
defer to credentials rather than evidence.

As I mentioned, the crystalline part of the failure (fatigue fracture)
has dirty areas and rust, something that belies your analysis. Please
review you ME texts with pictures of such failures and identify the
two zones of failure, the one that grew gradually and the one that
snapped of in the final thrust as the crank spindle did.

Jobst Brandt
[email hidden]

Arthur Shapiro said:

I've just been told it was a Phil Wood BB.

I'm not up on these spindles but I recall at one time they were
composites with solid ends welded onto a central tube. The heat
affected zone made them unreliable. I assume this one is not one of
those or it wouldn't have lasted as long as was reported.

More information please.

Jobst Brandt
[email hidden]

In article <[email hidden]>,

Leo Lichtman said:

"Richard Tack" wrote: Let's say you graduated with a GPA of 2.0; would
your analysis be any different? I think not.
^^^^^^^^^^^^^^^^
I hope not. I guess I made a mistake in trying to build up my credibility
by referring to my education. I know that Jobst Brandt commands a lot of
respect, and I am at a disadvantage in this discussion. But, does that
change the metallurgical truth? I think not. So lets talk about that
instead.

Yeah, trying to buff up your credibility on Usenet typically
backfires--principally because most people who do it are lying. Just
say your piece and justify it as best you can and most people will
listen.

--
B.B. --I am not a goat! thegoat4 at airmail.net