Update on frame failure

Carl Fogel writes:

http://pardo.net/bike/pic/fail-001/FAIL-017.html

Quoted message said:

Quoted message said:

As I look at this picture it strikes me as not a compression
failure from loading or braking. From what I can see this is a
ding in the tube caused by a foreign object. A tube wrinkled by
compression has a different contour and does not have a single
indentation as this one does. That this is a dent in the tube is
also apparent from there being no bend in the tube, which would
have to have occurred at the same time, it supposedly being a
compression failure. That is the nature of buckling of columns.

Quoted message said:

I think that you're mistaken--when I look at the frame, it looks
slightly bent to the naked eye:

http://pardo.net/bike/pic/fail-001/img-0.500-img_1242.jpg

Quoted message said:

And when I snap a straight line across the tube in the enlarged
picture, the "dented" tube is clearly bent. I tried, but couldn't
tell if the top or seat tubes were distorted. The line of the rear
brake cable sorta-kinda makes it look as if the top tube is slightly
bowed.

OK, slightly is not enough to cause the crash depicted nor is there
any indication of a fault that might cause this except that it was a
typical "over the bars" crash.

http://draco.acs.uci.edu/rbfaq/FAQ/9.36.html

Quoted message said:

The "dent" is in about the same place as much worse dent in
the picture in the other thread about this trashed mountain
bike:

Quoted message said:

http://snipurl.com/akxe

There is no parallel between the two incidents that I can imagine.

Quoted message said:

The "dents" in the same places and the similar bending of the tube
suggest the same mode (buckling) and point of failure, with one
example being much worse than the other. I expect that enough force
on the front fork will bend the frame in at about the same place
every time.

That doesn't make them related.

Quoted message said:

On the other hand, I see no scuff marks on the paint of the tube,
much less a hideous black skid mark, so I'm dubious that the front
tire touched the frame, much less jammed against the buckled frame
tube. It seems unlikely that a spinning rubber tire could hit a
painted surface hard enough to stop a bicycle and rider without
leaving a mark.

That is my assessment as well.

Jobst Brandt
[email hidden]

In rec.bicycles.tech Chalo writes:

http://pardo.net/bike/pic/fail-001/FAIL-017.html

Quoted message said:

Quoted message said:

As I look at this picture it strikes me as not a compression
failure from loading or braking. From what I can see this is a
ding in the tube caused by a foreign object. A tube wrinkled by
compression has a different contour and does not have a single
indentation as this one does.

Quoted message said:

Just before the bike stopped and pitched me off, there was a "crack"
sound. I am fairly certain that the sound came from the downtube as
it buckled, since it was clearly not the "clunk" that forks make
when the bottom out or the "ping" that frames make when they are
struck with a hard object.

Bending tubes do not make a cracking sound or even a clunk. What you
heard was something striking the downtube but I have no idea why that
would cause an end-over.

Quoted message said:

There was not so much as a scratch on the paint at the site of the
crease. The tube was arched upwards. Before I crashed, the frame
was in flawless condition as far as I knew.

It didn't arch upward significantly and the top tube is fairly
straight judging from the brake cable underneath that describes a
straight line for all practical purposes.

Quoted message said:

During the crash, the bike's handlebars hit the ground, but the rest
of it hit only me. If I had not been on clean open pavement, I
would have wondered whether something kicked up and jammed between
tire and downtube, but there was nothing present that could have
done that.

Quoted message said:

Quoted message said:

That this is a dent in the tube is also apparent from there
being no bend in the tube,

Quoted message said:

The upward bend in the downtube was quite apparent in just looking
at the bike, though it's relatively subtle in the furnished profile
view. If you use a straight edge, I think you'll see the vertical
displacement of the upper side of the tube is on the order of 1/2".
The downtube itself was originally conical, tapering from about 1.6"
to about 2.25" in diameter.

It looks more like an oval cross section in the picture offered, and
one that varies along its length. The bow it suffered is apparent
from the straight line of the parallel shift cable along its length in
the pictures.

http://draco.acs.uci.edu/rbfaq/FAQ/9.36.html

I am not convinced that the dent was caused by brake loading. There
was some other operator involved from what I can see.

Jobst Brandt
[email hidden]

Ryan Cousineau said:

In article <[email hidden]>,

(Chalo) said:

http://www.uploadimages.net/images/154121bohmside.JPG

If anybody has any ideas about where I might get a simple
made-to-measure frame in raw aluminum for cheap (sub-US$1,000), do
tell.

Chalo Colina

Is there a particular reason for choosing Al as the material of choice?
I mean, for that price there's a certain Ti builder who might do the
deed, and I think he does custom work too...

http://www.habcycles.com/mtb.html

Very funny, Mr. Cousineau!

--
Tom Sherman

"Chalo" <[email hidden]> wrote in message
news:[email hidden]...
| "GaryG" <garyg@shasta_SPAMBEGONE_software.com> wrote:
| >
| > On the website with pictures, it states:
| >
| > "In hard braking he reports it felt like the wheel jammed. The bike
flipped
| > and the rider broke both arms. In looking at the damage he suspects the
| > frame buckled, allowing the front tire to move back and jam on the
frame."
| >
| > I don't claim to be an expert in this, but I don't see how the front
tire
| > could have been able to move back and "jam on the frame" without
causing
| > significant damage to the head tube and/or forks.
|
| I can't see how it would have happened either-- but the bike went
| "crack" and the front wheel suddenly just stopped, like it had seized
| up. I am open to other hypotheses as to why that occurred.
|
| > But, the pictures on the
| > website don't show any damage in that area. The "ding" in the frame
could
| > have been caused by the crash due to impact with the ground or other
objects
| > (aluminum frames get dinged pretty easily, and a crash with a 385 lb
rider
| > could certainly cause damage like that).
|
| On close examination, I was also unable to find a tire mark, paint
| scuff, or any other marking at the site of the crease in the downtube.
|
| The bike didn't hit anything except me, after I had hit the ground .
| It came to rest with my legs all tangled up in it, and it took me
| probably half a minute to extract myself.
|
| > Given your weight, and the suspension forks, and the fact that you were
| > intentionally conducting a "hard braking test" with newly mounted disk
| > brakes, it seems possible that the forks took a sudden downward dive to
the
| > bottom of their travel, sending your weight forward and over the bars
(it's
| > a fairly common "over the bars" scenario in mountain biking accidents).
|
| I've bottomed out a lot of suspension forks,and none of them make the
| "crack" sound that preceded me getting tossed. These forks, Marzocchi
| MX Comp 29", I never managed to bottom out at all, despite their
| insufficient spring rate.
|
| I was trying to wear in the new pads, plus see if the improved braking
| would make anything bend from the added force, so I was stopping from
| 30-35mph on a steep downhill. I didn't make a sudden jerk at the
| brakes, so there was no sudden plunge to the bottom of the fork's
| travel. I had been hard on the brakes for about a full second before
| the "crack", so the fork had already sunk as low as it was going to
| go.
|
| Chalo Colina

Have you inspected the brake system for any broken parts and/or loss of
ability to modulate pressure? I'm wondering if the "crack" you heard
resulted from a failure in some part of the new brake. If that's the case,
the failure could have locked the wheel, and the extreme deceleration could
have simultaneously bent the down tube and pitched you over the bars.

JS

Chalo Colina said:

Now that I reflect on that description, I'll probably just commute on
my Bohemian-- and try not to gash up the paint too badly, or get it
heisted:

http://www.uploadimages.net/images/154121bohmside.JPG

That's the first 48-spoke wheel I've seen with a Rohloff hub.
Looks like a crow's-foot too, yes?

Any closer pics of the wheel? Did you drill more spoke
holes in the flanges yourself?

Tom Ace

Chalo said:

I reported a few weeks ago that I had buckled the frame of my bike
while braking

snip

Quoted message said:

Furthermore, I don't see how the suspension fork could have played a
role in the failure.

I notice you have a mechanical diskbrake with a very floppy brakecable.
If the fork compresses the cable will move about. If this were to catch
on the fronttire it would lock up the brake very fast.

--
---
Marten Gerritsen

INFOapestaartjeM-GINEERINGpuntNL
www.m-gineering.nl

"Steven M. Scharf" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

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

Quoted message said:

I have been advised in earnest by the Cannondale dealer that I should
use the original steel unicrown fork, with a rim brake, when I resume
the use of this bike.

How about forget the use of this bike and move to a frame that is less
likely to break, i.e. a steel frame.

Actually, steel frames are *more* likely to fail from overload. Since
aluminum has no fatigue limit, it has to be somewhat overbuilt to have
adequate fatigue life. This means it can take higher peak loads.

Quoted message said:

Chalo Colina said:

I reported a few weeks ago that I had buckled the frame of my bike
while braking and had broken my arms in the process. At that time I
said I'd be furnishing more details after I reached some agreement
with the manufacturer about a replacement.

As I look at this picture it strikes me as not a compression failure
from loading or braking. From what I can see this is a ding in the
tube caused by a foreign object. A tube wrinkled by compression has a
different contour and does not have a single indentation as this one
does. That this is a dent in the tube is also apparent from there
being no bend in the tube, which would have to have occurred at the
same time, it supposedly being a compression failure. That is the
nature of buckling of columns.

Quoted message said:

Jobst Brandt
[email hidden]

Jobst, I thought the Cannondale tubes
consisted of various thickness within the
same length of any given tube. If so,
would a thinner area at the indent change
your theory any?

In rec.bicycles.misc Richard Tack said:

Quoted message said:

Quoted message said:

I reported a few weeks ago that I had buckled the frame of my bike
while braking and had broken my arms in the process. At that time
I said I'd be furnishing more details after I reached some
agreement with the manufacturer about a replacement.

Quoted message said:

Quoted message said:

As I look at this picture it strikes me as not a compression
failure from loading or braking. From what I can see this is a
ding in the tube caused by a foreign object. A tube wrinkled by
compression has a different contour and does not have a single
indentation as this one does. That this is a dent in the tube is
also apparent from there being no bend in the tube, which would
have to have occurred at the same time, it supposedly being a
compression failure. That is the nature of buckling of columns.

Quoted message said:

I thought the Cannondale tubes consisted of various thickness within
the same length of any given tube. If so, would a thinner area at
the indent change your theory any?

No, because the blemish in the tube is a rounded dent made by some
object that has such a shape. That the paint is so clean and not
crazed makes this a mystery because the dent would have to be from a
piece of plastic or wood to not cause a blemish in the paint. That is
the object would have to be softer than the paint. the absence of
crazing in the paint implies that it is fairly elastic itself. The
whole incident seems odd to me. As I said, things don't seem to add
up. It reminds me of accident reconstructions I have made in
insurance claims in which the story told by the rider had little to do
with the damage. I don't know what to make of this but it doesn't
look like a load wrinkled tube to me.

Jobst Brandt
[email hidden]

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

Quoted message said:

In rec.bicycles.misc Richard Tack said:

Quoted message said:

> I reported a few weeks ago that I had buckled the frame of my bike
> while braking and had broken my arms in the process. At that time
> I said I'd be furnishing more details after I reached some
> agreement with the manufacturer about a replacement.

Quoted message said:

Quoted message said:

As I look at this picture it strikes me as not a compression
failure from loading or braking. From what I can see this is a
ding in the tube caused by a foreign object. A tube wrinkled by
compression has a different contour and does not have a single
indentation as this one does. That this is a dent in the tube is
also apparent from there being no bend in the tube, which would
have to have occurred at the same time, it supposedly being a
compression failure. That is the nature of buckling of columns.

Quoted message said:

I thought the Cannondale tubes consisted of various thickness within
the same length of any given tube. If so, would a thinner area at
the indent change your theory any?

No, because the blemish in the tube is a rounded dent made by some
object that has such a shape. That the paint is so clean and not
crazed makes this a mystery because the dent would have to be from a
piece of plastic or wood to not cause a blemish in the paint. That is
the object would have to be softer than the paint. the absence of
crazing in the paint implies that it is fairly elastic itself. The
whole incident seems odd to me. As I said, things don't seem to add
up. It reminds me of accident reconstructions I have made in
insurance claims in which the story told by the rider had little to do
with the damage. I don't know what to make of this but it doesn't
look like a load wrinkled tube to me.

Given the 385 lb rider, and the fact that he ended up "with my legs all
tangled up in it, and it took me
probably half a minute to extract myself", is it possible the dent was
caused by the rider's body?

GG

Quoted message said:

Jobst Brandt
[email hidden]

Gary G? said:

Quoted message said:

Quoted message said:

>> I reported a few weeks ago that I had buckled the frame of my
>> bike while braking and had broken my arms in the process. At
>> that time I said I'd be furnishing more details after I reached
>> some agreement with the manufacturer about a replacement.

Quoted message said:

Quoted message said:

Quoted message said:

> As I look at this picture it strikes me as not a compression
> failure from loading or braking. From what I can see this is a
> ding in the tube caused by a foreign object. A tube wrinkled by
> compression has a different contour and does not have a single
> indentation as this one does. That this is a dent in the tube is
> also apparent from there being no bend in the tube, which would
> have to have occurred at the same time, it supposedly being a
> compression failure. That is the nature of buckling of columns.

Quoted message said:

Quoted message said:

Quoted message said:

I thought the Cannondale tubes consisted of various thickness
within the same length of any given tube. If so, would a thinner
area at the indent change your theory any?

Quoted message said:

Quoted message said:

No, because the blemish in the tube is a rounded dent made by some
object that has such a shape. That the paint is so clean and not
crazed makes this a mystery because the dent would have to be from
a piece of plastic or wood to not cause a blemish in the paint.
That is the object would have to be softer than the paint. the
absence of crazing in the paint implies that it is fairly elastic
itself. The whole incident seems odd to me. As I said, things
don't seem to add up. It reminds me of accident reconstructions I
have made in insurance claims in which the story told by the rider
had little to do with the damage. I don't know what to make of
this but it doesn't look like a load wrinkled tube to me.

Quoted message said:

Given the 385 lb rider, and the fact that he ended up "with my legs
all tangled up in it, and it took me probably half a minute to
extract myself", is it possible the dent was caused by the rider's
body?

Now that you mention it, this could have been caused by a shoe sole or
plastic cleat, although I don't see that cleats were in use. However,
the "tangled up in the bicycle" scenario is an important clue. In any
case, I am certain that the damage on the downtube is not from
overload but rather from an impact of a foreign object.

Jobst Brandt
[email hidden]

Jean said:

Have you inspected the brake system for any broken parts and/or loss of
ability to modulate pressure? I'm wondering if the "crack" you heard
resulted from a failure in some part of the new brake. If that's the case,
the failure could have locked the wheel, and the extreme deceleration could
have simultaneously bent the down tube and pitched you over the bars.

That's a thought. The brakes seemed OK when I walked the bike back
home, but I'll have a closer look at them after I pick up the bike at
the dealer today.

Chalo

Blair P. Houghton said:

Dan said:

I agree. The fork isn't the problem.

It is. It's too long until it bottoms out.

By the time the fork is seeing a large braking load, it _is_ almost
bottomed, and no longer than a rigid fork. (Suspension forks are
usually shorter than rigid unicrowns when bottomed out.)

Chalo

Tom Sherman said:

Ryan Cousineau said:

Is there a particular reason for choosing Al as the material of choice?
I mean, for that price there's a certain Ti builder who might do the
deed, and I think he does custom work too...

http://www.habcycles.com/mtb.html

Very funny, Mr. Cousineau!

I have an economic embargo on businesses whose owners give support to
terrorists. ;^)

Chalo Colina

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

Quoted message said:

As I look at this picture it strikes me as not a compression failure
from loading or braking. From what I can see this is a ding in the
tube caused by a foreign object. A tube wrinkled by compression has a
different contour and does not have a single indentation as this one
does. That this is a dent in the tube is also apparent from there
being no bend in the tube, which would have to have occurred at the
same time, it supposedly being a compression failure. That is the
nature of buckling of columns.

This does not make sense. This ding probably occurred on loading the
bicycle in or on a car.

Just as an observation, quite a few years ago I buckled a steel frame
by running into a rider who had fallen right in front of me. It was at
fairly slow speed (going uphill) and my front wheel struck him
squarely, bringing my bike to an nearly instant stop. I went over the
bars, but neither I nor the other rider suffered any injuries. It was
not until some time after I had picked myself up and continued on that
I noticed the peculiar handling of my bike.

To make a long story short, my bike's wheelbase was shortened about 2
inches and it had a ding in the down tube nearly identical to that
shown in the photos in the present case, although at a location closer
to the head tube. Interestingly, the fork suffered no noticeable
permananent bend.

Based upon my one experience, a tube clearly can be "dinged" and
buckle without being subjected to impact and I do not think the
conclusion that a foreign object had to be involved is valid without
some other evidence indicating this to be the case.

DR

Peter Cole said:

"Steven M. Scharf" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

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

Quoted message said:

I have been advised in earnest by the Cannondale dealer that I should
use the original steel unicrown fork, with a rim brake, when I resume
the use of this bike.

How about forget the use of this bike and move to a frame that is less
likely to break, i.e. a steel frame.

Actually, steel frames are *more* likely to fail from overload. Since
aluminum has no fatigue limit, it has to be somewhat overbuilt to have
adequate fatigue life. This means it can take higher peak loads.

good! go to the top of the class.

Quoted message said:

Gary G? said:

Quoted message said:

>>>I reported a few weeks ago that I had buckled the frame of my
>>>bike while braking and had broken my arms in the process. At
>>>that time I said I'd be furnishing more details after I reached
>>>some agreement with the manufacturer about a replacement.

Quoted message said:

Quoted message said:

>>As I look at this picture it strikes me as not a compression
>>failure from loading or braking. From what I can see this is a
>>ding in the tube caused by a foreign object. A tube wrinkled by
>>compression has a different contour and does not have a single
>>indentation as this one does. That this is a dent in the tube is
>>also apparent from there being no bend in the tube, which would
>>have to have occurred at the same time, it supposedly being a
>>compression failure. That is the nature of buckling of columns.

Quoted message said:

Quoted message said:

>I thought the Cannondale tubes consisted of various thickness
>within the same length of any given tube. If so, would a thinner
>area at the indent change your theory any?

Quoted message said:

Quoted message said:

No, because the blemish in the tube is a rounded dent made by some
object that has such a shape. That the paint is so clean and not
crazed makes this a mystery because the dent would have to be from
a piece of plastic or wood to not cause a blemish in the paint.
That is the object would have to be softer than the paint. the
absence of crazing in the paint implies that it is fairly elastic
itself. The whole incident seems odd to me. As I said, things
don't seem to add up. It reminds me of accident reconstructions I
have made in insurance claims in which the story told by the rider
had little to do with the damage. I don't know what to make of
this but it doesn't look like a load wrinkled tube to me.

Quoted message said:

Given the 385 lb rider, and the fact that he ended up "with my legs
all tangled up in it, and it took me probably half a minute to
extract myself", is it possible the dent was caused by the rider's
body?

Now that you mention it, this could have been caused by a shoe sole or
plastic cleat, although I don't see that cleats were in use. However,
the "tangled up in the bicycle" scenario is an important clue. In any
case, I am certain that the damage on the downtube is not from
overload but rather from an impact of a foreign object.

Jobst Brandt
[email hidden]

translation: "don't know so i'll make something up that can only be
verbally contradicted".

it's buckling. get that empty beer can out and prove it to yourself.

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

Quoted message said:

Peter Cole said:

"Steven M. Scharf" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

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

>I have been advised in earnest by the Cannondale dealer that I should
>use the original steel unicrown fork, with a rim brake, when I resume
>the use of this bike.

How about forget the use of this bike and move to a frame that is less
likely to break, i.e. a steel frame.

Actually, steel frames are *more* likely to fail from overload. Since
aluminum has no fatigue limit, it has to be somewhat overbuilt to have
adequate fatigue life. This means it can take higher peak loads.

good! go to the top of the class.

I don't agree. Assuming that "overload" refers to any non-fatigue structural
failure...

Aluminum has about 1/3 the stiffness (modulus of elasticity) of steel and
about the same strength (yield). To compensate for its low stiffness,
aluminum is usually formed into larger diameter thin tubes, which are more
likely to fail in local buckling because of the low modulus of elasticity
and the thinner tube wall in relation to the tube diameter. I don't believe
that in this case the failure was a material strength or fatigue failure,
it was a stiffness or buckling failure. Recall that Euler's solution to
elastic columns is a function of material and section stiffness - not
material strength or fatigue properties. I also believe that a sudden
buckling of the tube wall could produce a "crack" or "snap" sound.

jim beam:

Quoted message said:

Peter Cole said:

"Steven M. Scharf" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

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

>I have been advised in earnest by the Cannondale dealer that I should
>use the original steel unicrown fork, with a rim brake, when I resume
>the use of this bike.

How about forget the use of this bike and move to a frame that is less
likely to break, i.e. a steel frame.

Actually, steel frames are *more* likely to fail from overload. Since
aluminum has no fatigue limit, it has to be somewhat overbuilt to have
adequate fatigue life. This means it can take higher peak loads.

good! go to the top of the class.

Which class is that?

Unless you have dimensions to compare structures built with both
materials, you're both in lala land.

In article <[email hidden]>,

(Chalo) said:

Tom Sherman said:

Ryan Cousineau said:

Is there a particular reason for choosing Al as the material of choice?
I mean, for that price there's a certain Ti builder who might do the
deed, and I think he does custom work too...

http://www.habcycles.com/mtb.html

Very funny, Mr. Cousineau!

I have an economic embargo on businesses whose owners give support to
terrorists. ;^)

Chalo Colina

Sheesh. I wrote privately regarding this to another correspondent, and
you may note how often I write in rb* politics threads, but I think this
is a poor economic strategy in most cases.

The eschaton on such a broad boycott (Republican business-owners) isn't
that Republicans will change their mind, it is (at best) parallel
economies. You don't really want to be as dumb as GOPers who won't eat
Heinz ketchup, do you?

I'm kind of reluctant to continue this thread of discussion, since it is
political rather than reality-based (simple rule: cycling is real,
politics is not, confine discussions of non-real topics to pubs and
avoid mixed company), and because it puts me in the awkward position of
playing sock-puppet for Habanero, a company with whom I have no
relationship (I'm willing to plug them as a low-price maker of Ti
frames, since they fit your requested cost parameters, and because I
wanted to ask about your general exclusion of non-Al frames).

Mark has shown a general (and reasonable) reluctance to enter into most
discussions which refer directly to his company in this way, and I think
this is a generally sensible policy, since it avoids excessive
self-plugging, and allows him to productively discuss bike tech here
without unseemly self-promotion.

As I once pointed out in defending Jobst, the alternative to the prickly
Jobst we all know and love is probably not a kinder, gentler Jobst, it's
that Jobst will stop posting in this newsgroup. Similarly, I don't think
the alternative to the Mark Hickey we all know and love is a Mark who
suddenly sees the light and whips out a Nader-themed bicycle ("designed
according to safety principles laid down by Ralph himself!"😉, it's a
Mark who stops posting here because it's more trouble than joy.

I don't think that's a positive outcome.

--
Ryan Cousineau, [email hidden] http://www.wiredcola.com
Verus de parvis; verus de magnis.