Stem Failure?

Does this failure look typical to anybody?

I am borderline-obsessive about tightening to spec (48 inch
pounds in this case), so I don't think it was a case of
over-tightening.

Blurry Photo On Bike:
http://tinyurl.com/7dq5brf

Clearer Photos Of Pieces:
http://tinyurl.com/82yaleg
http://tinyurl.com/6wgtcva
http://tinyurl.com/7nwjlzg
--
Pete Cresswell

(PeteCresswell) wrote:
Does this failure look typical to anybody?

I am borderline-obsessive about tightening to spec (48 inch
pounds in this case), so I don't think it was a case of
over-tightening.

Blurry Photo On Bike:
http://tinyurl.com/7dq5brf

Clearer Photos Of Pieces:
http://tinyurl.com/82yaleg
http://tinyurl.com/6wgtcva
http://tinyurl.com/7nwjlzg


I just see a white screen.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

"(PeteCresswell)" wrote:
oes this failure look typical to anybody?

:I am borderline-obsessive about tightening to spec (48 inch
ounds in this case), so I don't think it was a case of
ver-tightening.

:Blurry Photo On Bike:
:http://tinyurl.com/7dq5brf

:Clearer Photos Of Pieces:
:http://tinyurl.com/82yaleg
:http://tinyurl.com/6wgtcva
:http://tinyurl.com/7nwjlzg

No pictures...
--
sig 8

On Dec 25, 2:28*pm, "(PeteCresswell)" wrote:
Does this failure look typical to anybody?

I am borderline-obsessive about tightening to spec (48 inch
pounds in this case), so I don't think it was a case of
over-tightening.

Blurry Photo On Bike:http://tinyurl.com/7dq5brf

Clearer Photos Of Pieces:http://tinyurl.com/82yaleghttp://tin...rl.com/7nwjlzg
--
Pete Cresswell

"Links also broken" (just a little Christmas Day humor attempted
there).
--D-y

On Sun, 25 Dec 2011 15:28:08 -0500, "(PeteCresswell)"
wrote:

Does this failure look typical to anybody?

I am borderline-obsessive about tightening to spec (48 inch
pounds in this case), so I don't think it was a case of
over-tightening.

Blurry Photo On Bike:
http://tinyurl.com/7dq5brf

Clearer Photos Of Pieces:
http://tinyurl.com/82yaleg
http://tinyurl.com/6wgtcva
http://tinyurl.com/7nwjlzg

The links don't work. Picassa returns "Sorry, that page was not
found" for all of them. The main site works:
https://picasaweb.google.com/108149798664924808733/
but I can't find the November72011 sub directory.
Perhaps permissions to view without a login?

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

In article ,
Jeff Liebermann wrote:

On Sun, 25 Dec 2011 15:28:08 -0500, "(PeteCresswell)"
wrote:

Does this failure look typical to anybody?

I am borderline-obsessive about tightening to spec (48 inch
pounds in this case), so I don't think it was a case of
over-tightening.

Blurry Photo On Bike:
http://tinyurl.com/7dq5brf

Clearer Photos Of Pieces:
http://tinyurl.com/82yaleg
http://tinyurl.com/6wgtcva
http://tinyurl.com/7nwjlzg

The links don't work. Picassa returns "Sorry, that page was not
found" for all of them. The main site works:
https://picasaweb.google.com/108149798664924808733/
but I can't find the November72011 sub directory.
Perhaps permissions to view without a login?

The links work fine for me.

Concerning the picture, showing a 4-bolt stem with the front "plate"
split cleanly in half along the horizontal: That is truly scary. I had
read that 4 bolts should be safer than 2, given that with two the
failure any one bolt will lead to catastrophic failure. Never considered
the possibility of the plate itself failing.

Ned

Ned Mantei wrote:
Concerning the picture, showing a 4-bolt stem with the front
"plate" split cleanly in half along the horizontal: That is truly
scary.

It's not the worst failure mode though: the bar will turn in the
loose clamp but the rider will stay able to steer and (carefully)
brake.


Anyway: From the failure mode I would expect the plate was bent,
i.e. the bar either over size or deformed or the bolts way
overtightened. Thomson might be interested in stem and bar.


I had read that 4 bolts should be safer than 2, given that with
two the failure any one bolt will lead to catastrophic failure.

If 1 bolt in a 2 bolt stem fails the bending forces on the plate are
pretty and it's likely to snap near the remaining bolt, thus freeing
the bar and removing all steering, which typically results in a
crash.

--
MfG/Best regards
helmut springer panta rhei

Ned Mantei wrote:
Concerning the picture, showing a 4-bolt stem with the front
"plate" split cleanly in half along the horizontal: That is truly
scary.

It's not the worst failure mode though: the bar will turn in the
loose clamp but the rider will stay able to steer and (carefully)
brake.


Anyway: From the failure mode I would expect the plate was bent,
i.e. the bar either off size or deformed or the bolts way
overtightened. Thomson might be interested in stem and bar.


I had read that 4 bolts should be safer than 2, given that with
two the failure any one bolt will lead to catastrophic failure.

If 1 bolt in a 2 bolt stem fails the bending forces on the plate are
pretty high and it's likely to snap near the remaining bolt, thus
freeing the bar and removing all steering, which typically results
in a crash.

--
MfG/Best regards
helmut springer panta rhei

On Dec 25, 8:28*pm, "(PeteCresswell)" wrote:
Does this failure look typical to anybody?

I am borderline-obsessive about tightening to spec (48 inch
pounds in this case), so I don't think it was a case of
over-tightening.

Blurry Photo On Bike:http://tinyurl.com/7dq5brf

Clearer Photos Of Pieces:http://tinyurl.com/82yaleghttp://tin...rl.com/7nwjlzg
--
Pete Cresswell

Looks like a low strength material failure. The plate is simply too
thin as a cast item, it should be cold forged or at least machined
from rolled material in those dimensions. Only if you bulked up the
bar diameter could you be held in any way to blame, but the appearance
of the fracture, from the given images, simply does not suggest this.

Op 26-12-2011 14:38, thirty-six schreef:
On Dec 25, 8:28 pm, wrote:
Does this failure look typical to anybody?

I am borderline-obsessive about tightening to spec (48 inch
pounds in this case), so I don't think it was a case of
over-tightening.

Blurry Photo On Bike:http://tinyurl.com/7dq5brf

Clearer Photos Of Pieces:http://tinyurl.com/82yaleghttp://tin...rl.com/7nwjlzg
--
Pete Cresswell

Looks like a low strength material failure. The plate is simply too
thin as a cast item, it should be cold forged or at least machined
from rolled material in those dimensions. Only if you bulked up the
bar diameter could you be held in any way to blame, but the appearance
of the fracture, from the given images, simply does not suggest this.

I'm sure it is machined. The fracture looks brittle though.

Lou