photos of broken bike bits

The University of Limerick Mountain BIke Club has collected some
interesting failures.

http://www.skynet.ie/~mtbclub/Photogallery/0001_Broken/

I'm curious how that rigid fork might have failed. The crack is on the
left leg, on the back side, and has some light orange rust. The bent
right leg I imagine might have collapsed as a result after the left one
let go.

Any opinions?

wrote:
The University of Limerick Mountain BIke Club has collected some
interesting failures.

http://www.skynet.ie/~mtbclub/Photogallery/0001_Broken/

I'm curious how that rigid fork might have failed. The crack is on the
left leg, on the back side, and has some light orange rust. The bent
right leg I imagine might have collapsed as a result after the left
one let go.

Any opinions?

There once was a site with pics
Of breaks, and cracks, and strips
Along came Carl Fogel
The Usenet mogul
And Dianne's modest thread was ripped

Crystal Ball Bill
(rainy morning)

wrote:
The University of Limerick Mountain BIke Club has collected some
interesting failures.

http://www.skynet.ie/~mtbclub/Photogallery/0001_Broken/

I'm curious how that rigid fork might have failed. The crack is on
the
left leg, on the back side, and has some light orange rust. The bent
right leg I imagine might have collapsed as a result after the left
one
let go.

Any opinions?

Here's the closeup: http://tinyurl.com/6lxzw

The bike appears to be heavily gusseted around the head tube, and it's
equipped with Magura hydraulic brakes. This leads me to believe that it
was used for rough riding- slalom competition, jumping, wheelies, or
trials. The fork is also bent forward, so the initial failure is on the
back side of the fork.

I'd guess it's a fatigue failure of the fork leg. The failure is right
at where it transitions from straight leg to bend, a highly stressed
and heavily manipulated area. Add abusive riding, and it probably went
sproing when the rider landed.

Jeff

dianne who? writes:

The University of Limerick Mountain BIke Club has collected some
interesting failures.

http://www.skynet.ie/~mtbclub/Photogallery/0001_Broken/

I see mostly pictures of a failed tight crank that unfortunately is
focused on the pedal rather than the fracture. Just the same, it also
shows the failure mode to be one of bending from standing on the
bottom of the stroke as most previous pictures of crank failures have.

I'm curious how that rigid fork might have failed. The crack is on
the left leg, on the back side, and has some light orange rust. The
bent right leg I imagine might have collapsed as a result after the
left one let go.

I see a bent fork and a separated head tube. I don't see a fork
separation or crack.

Jobst Brandt

On Sat, 12 Feb 2005 19:24:03 GMT,
wrote:

dianne who? writes:

The University of Limerick Mountain BIke Club has collected some
interesting failures.

http://www.skynet.ie/~mtbclub/Photogallery/0001_Broken/

[snip]

I'm curious how that rigid fork might have failed. The crack is on
the left leg, on the back side, and has some light orange rust. The
bent right leg I imagine might have collapsed as a result after the
left one let go.

I see a bent fork and a separated head tube. I don't see a fork
separation or crack.

Jobst Brandt


Dear Jobst,

You may not have been looking at the pictures that Dianne
had in mind. I think that she meant the broken fork shown in
pictures #31..#34 on the third page of the gallery.

Carl Fogel

On Sat, 12 Feb 2005 19:24:03 GMT, may
have said:

dianne who? writes:

The University of Limerick Mountain BIke Club has collected some
interesting failures.

http://www.skynet.ie/~mtbclub/Photogallery/0001_Broken/

I see mostly pictures of a failed tight crank that unfortunately is
focused on the pedal rather than the fracture. Just the same, it also
shows the failure mode to be one of bending from standing on the
bottom of the stroke as most previous pictures of crank failures have.

I'm curious how that rigid fork might have failed. The crack is on
the left leg, on the back side, and has some light orange rust. The
bent right leg I imagine might have collapsed as a result after the
left one let go.

I see a bent fork and a separated head tube. I don't see a fork
separation or crack.

Page three, photos 31 through 34. I'd say it looks like the fork tube
had a flaw which resulted in a stress crack across the back of the
leg, and that the other one just folded, as Dianne supposed, when the
crack propagated far enough for the tube to tear.

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

On Sat, 12 Feb 2005 19:24:03 GMT,
wrote:

dianne who? writes:

The University of Limerick Mountain BIke Club has collected some
interesting failures.

http://www.skynet.ie/~mtbclub/Photogallery/0001_Broken/

I see mostly pictures of a failed tight crank that unfortunately is
focused on the pedal rather than the fracture. Just the same, it also
shows the failure mode to be one of bending from standing on the
bottom of the stroke as most previous pictures of crank failures have.

That one interested me because in several photos I think I can see the
darker side of the crack on the /inner/ side of the arm, as if the
crack had originated *opposite* to the "standing on the pedal at 6:00"
argument would suggest. Photos 8-10 are the ones.

It also appears to me there might be a sudden change in cross section
near the break, but I'm not familiar with the crank model.

On Sat, 12 Feb 2005 14:29:10 -0600, Werehatrack
wrote:

On Sat, 12 Feb 2005 19:24:03 GMT, may
have said:

http://www.skynet.ie/~mtbclub/Photogallery/0001_Broken/

a fork separation or crack.

Page three, photos 31 through 34. I'd say it looks like the fork tube
had a flaw which resulted in a stress crack across the back of the
leg, and that the other one just folded, as Dianne supposed, when the
crack propagated far enough for the tube to tear.

I agree. Are we missing anything? The break in "splay" is opposite to
what I've seen the most of (bent front to back). Could a hard landing
have been an aggravating factor? Or is a tube flaw (and riding) all it
takes?

http://www.skynet.ie/~mtbclub/Photogallery/0001_Broken/

a fork separation or crack.

Page three, photos 31 through 34.


"dianne_1234" wrote:

I agree. Are we missing anything? The break in "splay" is
opposite to what I've seen the most of (bent front to back).
Could a hard landing have been an aggravating factor?
Or is a tube flaw (and riding) all it takes?


Judging by the equipment (tiny chainring, bashguard, and Magurae), and the
very low seat position. this poor little mtb has been pressed into trials
service and jumped to death. The same bike features in several pictures.

The bike looks newest in the picture with the head tube separation. It may
be that the frame was then replaced and the fork was kept, having survived
the impact that caused the frame to snap. I can't figure out whether the
red crank broke and was replaced before the fork died, or vice versa.

In any case, a clumsy trials rider who land heavilys can subject a bike to
repeated shocks outside the normal range of abuse.

James Thomson

"dianne_1234" wrote:

That one interested me because in several photos I think I can
see the darker side of the crack on the /inner/ side of the arm,
as if the crack had originated *opposite* to the "standing on
the pedal at 6:00" argument would suggest. Photos 8-10 are
the ones.

It also appears to me there might be a sudden change in cross section
near the break, but I'm not familiar with the crank model.

It resembles (but may not be) an FSA Power Pro:

http://www.chainreactioncycles.com//...px?ModelID=873

It looks as though the transition from the base of the hidden fifth spider
arm to the crank proper is point of growth for the crack. A little like
this one (a Coda 'Magic' M900) which was detected early:

http://pardo.net/pardo/bike/pic/fail/FAIL-014.html

James Thomson