Crack in chainstay bridge: how did it happen?

I just discovered a crack in the chainstay bridge that seems to go from the middle of the bridge,
across the weld, and into the left chainstay. This is a (very) high end titanium frame,
approximately 8 years old, and has never been crashed. I did do the hardest climb I've ever done
(23%) the day before this discovery, but I doubt that caused it. The frame has been sent back to the
builder, most likely under their lifetime warranty.

A high-resolution picture can be found at

http://mywebpages.comcast.net/kenlehner/105_05842.JPG

How might this have happened, how long could it have been there, and what might have happened if I
continued to ride it? Thanks for any and all opinions.

Ken Lehner

 

On 30 May 2003 06:47:42 -0700, [email protected] (Ken Lehner) wrote:

>I just discovered a crack in the chainstay bridge that seems to go from the middle of the bridge,
>across the weld, and into the left chainstay. This is a (very) high end titanium frame,
>approximately 8 years old, and has never been crashed. I did do the hardest climb I've ever done
>(23%) the day before this discovery, but I doubt that caused it. The frame has been sent back to
>the builder, most likely under their lifetime warranty.
>
>A high-resolution picture can be found at
>
>http://mywebpages.comcast.net/kenlehner/105_05842.JPG
>
>How might this have happened, how long could it have been there, and what might have happened if I
>continued to ride it? Thanks for any and all opinions.
>
>Ken Lehner

sure looks like a twist fracture ... I would expect warranty.

If I had to guess (which I am) I would see you as a larger (and/or stronger) than average rider who
spends a lot of time out of the saddle..

having the crack propagate to the stay would indicate that eventually, on the drive side downstroke
the stay would have parted completely..

 

Ken Lehner writes:

> I just discovered a crack in the chainstay bridge that seems to go from the middle of the bridge,
> across the weld, and into the left chainstay. This is a (very) high end titanium frame,
> approximately 8 years old, and has never been crashed. I did do the hardest climb I've ever done
> (23%) the day before this discovery, but I doubt that caused it. The frame has been sent back to
> the builder, most likely under their lifetime

> A high-resolution picture can be found at

> http://mywebpages.comcast.net/kenlehner/105_05842.JPG

> How might this have happened, how long could it have been there, and what might have happened if I
> continued to ride it? Thanks for any and all opinions.

The picture has lighting that obscures whether this is a crack at all. From what I can see, it is a
scratch in the paint similar to the one on the inside of the chainstay. This little tube has no
structural function other than to keep the rear wheel from jamming in the "V" of the chainstays when
knocked forward from horizontal dropouts, an archaic attachment in the first place. On touring
bicycles it was used to attach the rear mud guard.

If you could take another, more close-up, picture of the "crack" at its widest, it might show that
the "crack" is in fact a scratch. The only place it has the resemblance of a crack is where it
passes over the weld and that could be cause by the unevenness of the weld surface that diverted the
scratching element. Cracks usually affect paint differently that the picture shows.

Let us know what you find... or what the Mfg found.

Jobst Brandt [email protected] Palo Alto CA

 

In article <[email protected]>, [email protected] says...
>
>
>I just discovered a crack in the chainstay bridge that seems to go from the middle of the bridge,
>across the weld, and into the left chainstay. This is a (very) high end titanium frame,
>approximately 8 years old, and has never been crashed. I did do the hardest climb I've ever done
>(23%) the day before this discovery, but I doubt that caused it. The frame has been sent back to
>the builder, most likely under their lifetime warranty.
>
>A high-resolution picture can be found at
>
>http://mywebpages.comcast.net/kenlehner/105_05842.JPG
>
>How might this have happened, how long could it have been there, and what might have happened if I
>continued to ride it? Thanks for any and all opinions.

Hard to tell from the picture, but it looks more like a scratch than a crack.
-----------------
Alex __O _-\<,_ (_)/ (_)

 

paint defect. not oriented for stress, and it traverses a weld.

jb

Ken Lehner wrote:
> I just discovered a crack in the chainstay bridge that seems to go from the middle of the bridge,
> across the weld, and into the left chainstay. This is a (very) high end titanium frame,
> approximately 8 years old, and has never been crashed. I did do the hardest climb I've ever done
> (23%) the day before this discovery, but I doubt that caused it. The frame has been sent back to
> the builder, most likely under their lifetime warranty.
>
> A high-resolution picture can be found at
>
> http://mywebpages.comcast.net/kenlehner/105_05842.JPG
>
> How might this have happened, how long could it have been there, and what might have happened if I
> continued to ride it? Thanks for any and all opinions.
>
> Ken Lehner

 

"ajames54" <[email protected]> wrote in message
news:[email protected]...
>
>
> sure looks like a twist fracture ... I would expect warranty.

Expect a warranty replacement after r8 years. That is un-reasonable. Yea I know Litespeed's
marketing managers would disagree but any sane bike maker or materials expert would agree.

 

Ken Lehner at [email protected] wrote on 5/30/03 6:47 AM:
> I just discovered a crack in the chainstay bridge that seems to go from the middle of the bridge,
> across the weld, and into the left chainstay. This is a (very) high end titanium frame,
> approximately 8 years old, and has never been crashed. I did do the hardest climb I've ever done
> (23%) the day before this discovery, but I doubt that caused it. The frame has been sent back to
> the builder, most likely under their lifetime warranty.

Looks more like someone ganked it with a sharp tool - starts narrow, digs in and ends narrow...

As others have observed, it's not exactly in a high-stress area or direction.

-- Jim

 

On 30 May 2003 06:47:42 -0700, [email protected] (Ken Lehner) wrote:

>I just discovered a crack in the chainstay bridge that seems to go from the middle of the bridge,
>across the weld, and into the left chainstay. This is a (very) high end titanium frame,
>approximately 8 years old, and has never been crashed. I did do the hardest climb I've ever done
>(23%) the day before this discovery, but I doubt that caused it. The frame has been sent back to
>the builder, most likely under their lifetime warranty.
>
>A high-resolution picture can be found at
>
>http://mywebpages.comcast.net/kenlehner/105_05842.JPG
>
>How might this have happened, how long could it have been there, and what might have happened if I
>continued to ride it? Thanks for any and all opinions.
>
>Ken Lehner
It is a pretty big file... don't view it in your browser, download it and use a real image viewer...

it is pretty clearly a crack.

 

ajames54 <[email protected]> wrote in message
news:<[email protected]>...
>
> sure looks like a twist fracture ... I would expect warranty.
>
> If I had to guess (which I am) I would see you as a larger (and/or stronger) than average rider
> who spends a lot of time out of the saddle..

"Larger" is so subjective; I'm 175lbs and 6'. Stronger I ain't. I do like to climb hills, and I do
stand a bit.

Ken Lehner

 

[email protected] wrote in message news:<[email protected]>...
> The picture has lighting that obscures whether this is a crack at all. From what I can see, it is
> a scratch in the paint similar to the one on the inside of the chainstay.

Are you saying that there are two scratches, one on the bridge and one on the chainstay?

> If you could take another, more close-up, picture of the "crack" at its widest, it might show that
> the "crack" is in fact a scratch. The only place it has the resemblance of a crack is where it
> passes over the weld and that could be cause by the unevenness of the weld surface that diverted
> the scratching element. Cracks usually affect paint differently that the picture shows.

I uploaded two more pictures:

http://mywebpages.comcast.net/kenlehner/105_0582.JPG and
http://mywebpages.comcast.net/kenlehner/105_0579.JPG

Don't know if those show more information. Can't get any more close-up, I'm afraid: we used the
macro setting on a digital camera.

>
> Let us know what you find... or what the Mfg found.

Will do. There was a distinctive hard, sharp edge to the "crack"; the dealer who shipped it back
scraped off some paint and thought it was a crack, not a scratch.

Ken Lehner

 

Ken Lehner writes:

> Are you saying that there are two scratches, one on the bridge and one on the chainstay?

There is another mark on the chainstay emanating from the middle of the bridge tube but it is
smaller and fainter.

>> If you could take another, more close-up, picture of the "crack" at its widest, it might show
>> that the "crack" is in fact a scratch. The only place it has the resemblance of a crack is where
>> it passes over the weld and that could be cause by the unevenness of the weld surface that
>> diverted the scratching element. Cracks usually affect paint differently that the picture shows.

> I uploaded two more pictures:

http://mywebpages.comcast.net/kenlehner/105_0582.JPG
http://mywebpages.comcast.net/kenlehner/105_0579.JPG

The second picture does, and the feature of interest is that the line splits in two finer lines
before tapering to nothing. that is the "scratch" has no end, it vanishes into detail too fine to
be a scratch, there being nothing that fine that could make a scratch. This is evidence that it
is a crack.

> Don't know if those show more information. Can't get any more close-up, I'm afraid: we used the
> macro setting on a digital camera.

Well done, for no microscope!

>> Let us know what you find... or what the Mfg found.

> Will do. There was a distinctive hard, sharp edge to the "crack"; the dealer who shipped it back
> scraped off some paint and thought it was a crack, not a scratch.

Oh noooooo. He destroyed valuable evidence. Not nice.

Jobst Brandt [email protected] Palo Alto CA

 

[email protected] (Ken Lehner) wrote in message
news:<[email protected]>...
> [email protected] wrote in message
> news:<[email protected]>...
> > Let us know what you find... or what the Mfg found.

The news is that the manufacturer has determined that the tubes are cracked, and that they will
replace the damaged tubes and repaint with the original colors of my 8 year old frame, all under
warranty. Can't ask for more than that!

So, how did this happen, if the bridge is under little or no pressure?

Ken Lehner

 

On 4 Jun 2003 07:00:17 -0700, [email protected] (Ken Lehner) wrote:

>[email protected] (Ken Lehner) wrote in message
>news:<[email protected]>...
>> [email protected] wrote in message
>> news:<[email protected]>...
>> > Let us know what you find... or what the Mfg found.
>
>The news is that the manufacturer has determined that the tubes are cracked, and that they will
>replace the damaged tubes and repaint with the original colors of my 8 year old frame, all under
>warranty. Can't ask for more than that!
>
>So, how did this happen, if the bridge is under little or no pressure?
>
>Ken Lehner

Good to hear they are going to deal with it... though I am a bit surprised they would replace the
tubes and repaint ... but then again I don't know who they are so ...

There are a couple of possibilities as to how it happened... I'm inclined to think that the bridge
was mitered incorrectly or there was a rear triangle alignment problem.

I also don't think it is necessarily true that the bridge itself is under little or no pressure, it
acts as a stiffener for the rear triangle under pedal loads. Not normally a big deal but if there
was some sort of residual stress in the part from one of the above two causes then this sort of
thing could happen.

Could also happen if the tube was flawed or if the weld was contaminated.

 

Ken Lehner writes:

>> Let us know what you find... or what the Mfg found.

> The news is that the manufacturer has determined that the tubes are cracked, and that they will
> replace the damaged tubes and repaint with the original colors of my 8 year old frame, all under
> warranty. Can't ask for more than that!

> So, how did this happen, if the bridge is under little or no pressure?

When I see such a failure my first response is that it is highly unlikely and try to see if the
apparent crack is a scratch in the finish. Now that the existence of the crack is determined I must
assume there are stresses here that are not related to use of the bicycle. That would be residual
stress from welding, one end being welded after the other and that the direction of advancing the
weld of the second end caused high torsional stress on cooling. This stress, overlayed by the cyclic
low stress this tube experiences in use caused the somewhat helical crack.

This is something that would not occur in longer tubes because their torsional rigidity is low
enough to absorb such loads. This frame would do well with no tube there at all or at best a flat
tab (that some Italian frames used before ultra short chainstay became fashion). The tube is there
only to prevent tire jamming in the crotch of the chainstays when removing a rear wheel from
horizontal dropouts. It is a vestigial frame element.

Jobst Brandt [email protected] Palo Alto CA

 

<[email protected]> wrote in message newsmrDa.132$%[email protected]...

> The tube is there only to prevent tire jamming in the
crotch of the
> chainstays when removing a rear wheel from horizontal
dropouts. It is
> a vestigial frame element.

There -- one more reason not to have horizontal dropouts...

Matt O.

 

<[email protected]> wrote:
>The tube is there only to prevent tire jamming in the crotch of the chainstays when removing a rear
>wheel from horizontal dropouts. It is a vestigial frame element.

Most rear mudguards attach to it.
--
David Damerell <[email protected]> flcl?

 

David Damerell writes:

>> The tube is there only to prevent tire jamming in the crotch of the chainstays when removing a
>> rear wheel from horizontal dropouts. It is a vestigial frame element.

> Most rear mudguards attach to it.

Oh! Where do you see an attachment point on any of the bicycles of this kind or the one in question.
That would be on transportation bicycles rather than ones used for sport. The ones I had with
mudguards had a split side, rolled up, tube with a screw hole in it.

Jobst Brandt [email protected] Palo Alto CA

 

<[email protected]> wrote:
>David Damerell writes:
>><[email protected]> wrote:
>>>The tube is there only to prevent tire jamming in the crotch of the chainstays when removing a
>>>rear wheel from horizontal dropouts. It is a vestigial frame element.
>>Most rear mudguards attach to it.
>Oh! Where do you see an attachment point on any of the bicycles of this kind or the one in
>question.

I've never seen the bicycle in question; my observation was more general, that this tube continues
to serve a useful purpose on some frames.

>That would be on transportation bicycles rather than ones used for sport.

Perhaps things are different in the USA, but I have not seen any full-length rear mudguards that are
not of this design (and yes, I have looked at a fair selection of mudguards) - I suppose there must
be some other designs for people who don't have this tube, but it seems to be a convenient
attachment method that is not prone to coming loose.
--
David Damerell <[email protected]> flcl?

 

On 06 Jun 2003 11:20:25 +0100 (BST), David Damerell <[email protected]> wrote:
><[email protected]> wrote:

>>That would be on transportation bicycles rather than ones used for sport.
>
>Perhaps things are different in the USA, but I have not seen any full-length rear mudguards that
>are not of this design (and yes, I have looked at a fair selection of mudguards) - I suppose there
>must be some other designs for people who don't have this tube, but it seems to be a convenient
>attachment method that is not prone to coming loose.

I think he means that bikes used for sport don't have fenders.

Jasper

 

Jasper Janssen <[email protected]> wrote:
><[email protected]> wrote:
>><[email protected]> wrote:
>>>That would be on transportation bicycles rather than ones used for sport.
>>Perhaps things are different in the USA, but I have not seen any full-length rear mudguards that
>>are not of this design
>I think he means that bikes used for sport don't have fenders.

I think he means that too. If you read my article you will see that I am simply saying that on
bicycles that do have mudguards, the chainstay bridge is not a useless piece of the frame.
--
David Damerell <[email protected]> flcl?