A Cycling & bikes forum. CycleBanter.com

Go Back   Home » CycleBanter.com forum » rec.bicycles » Techniques
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

photos of broken bike bits



 
 
Thread Tools Display Modes
  #11  
Old February 13th 05, 06:03 AM
external usenet poster
 
Posts: n/a
Default

dianne_1234 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.


You will probably agree that the crank broke crosswise, no in torsion
(spiral) or to the outside (for which there are no forces).
Therefore, without going further into fracture analysis, it is safe to
say that it broke inward from the standing load on the pedal.

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.


That is not ruled out, but as I said, the pictures are all focused on
the pedal leaving the fracture blurred. We need a better photographer
and one with a flash or other illumination.

Jobst Brandt

Ads
  #12  
Old February 13th 05, 06:59 AM
A Muzi
external usenet poster
 
Posts: n/a
Default

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.



#31~#34 are forks damaged by jumping. (Or actually, they
were fine until it landed.)

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
  #13  
Old February 13th 05, 08:21 AM
external usenet poster
 
Posts: n/a
Default

On Sat, 12 Feb 2005 23:59:55 -0600, A Muzi
wrote:

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.



#31~#34 are forks damaged by jumping. (Or actually, they
were fine until it landed.)


Dear Andrew,

Another poster suggested trials-style riding, so I'm just
asking to be sure.

Do you mean dropping off a big ledge with the front wheel
bashing into the flat ground at the bottom at a steep
nose-down angle? (Push the fork back into the frame.)

Or am I misunderstanding, and you mean flying jumps where
the bike lands fairly flat at high speed on both wheels?
(Splay the fork outward.)

Carl Fogel
  #14  
Old February 13th 05, 09:50 AM
A Muzi
external usenet poster
 
Posts: n/a
Default

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.


wrote:
#31~#34 are forks damaged by jumping. (Or actually, they
were fine until it landed.)



wrote:
Another poster suggested trials-style riding, so I'm just
asking to be sure.

Do you mean dropping off a big ledge with the front wheel
bashing into the flat ground at the bottom at a steep
nose-down angle? (Push the fork back into the frame.)

Or am I misunderstanding, and you mean flying jumps where
the bike lands fairly flat at high speed on both wheels?
(Splay the fork outward.)


Sorry to be unclear. I meant the latter, as the fork goes
the other way in the former, like this:
http://www.yellowjersey.org/photosfr...t/NIMGAFRK.JPG

As I recall from my youth, when we rode down a large hill
then up a berm to get a couple of feet of air, the rear
lands first followed by a great _thwack_ as the front hits.
That's where I saw this type of failure first.

I imagine it wouldn't be as destructive if one could manage
to get both wheels to land at the same time.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
  #15  
Old February 13th 05, 04:16 PM
Bill Sornson
external usenet poster
 
Posts: n/a
Default

Bill Sornson wrote:
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


PS: The University of LIMERICK was what I was... never mind.


  #16  
Old February 13th 05, 09:00 PM
Tim McNamara
external usenet poster
 
Posts: n/a
Default

A Muzi writes:

As I recall from my youth, when we rode down a large hill then up a
berm to get a couple of feet of air, the rear lands first followed
by a great _thwack_ as the front hits. That's where I saw this type
of failure first.


Hmmm, yes, I remember bending the fork on my Hercules 3 speed in
exactly the same way, increasing the fork offset by a good inch or
more and making the tire rub the trailing edge of the fender, so that
I had to bend it upwards just to be able to still ride the bike home.
As I recall, I "repaired" the fork by running the bike into the back
wall of the garage a few times until it looked about right. :-O
  #17  
Old February 14th 05, 02:11 AM
external usenet poster
 
Posts: n/a
Default

On Sun, 13 Feb 2005 14:00:54 -0600, Tim McNamara
wrote:

A Muzi writes:

As I recall from my youth, when we rode down a large hill then up a
berm to get a couple of feet of air, the rear lands first followed
by a great _thwack_ as the front hits. That's where I saw this type
of failure first.


Hmmm, yes, I remember bending the fork on my Hercules 3 speed in
exactly the same way, increasing the fork offset by a good inch or
more and making the tire rub the trailing edge of the fender, so that
I had to bend it upwards just to be able to still ride the bike home.
As I recall, I "repaired" the fork by running the bike into the back
wall of the garage a few times until it looked about right. :-O


Dear Tim and Andrew,

D'oh!

I looked again at all the pictures and figured out that I
had things backwards.

This does indeed look like splayed-out pancake-landing
after-jump damage, not the nose-down, drop-off-a-table,
low-speed damage that I was wondering about.

Thanks for de-confusing me.

Carl Fogel
  #18  
Old February 14th 05, 02:18 AM
James Thomson
external usenet poster
 
Posts: n/a
Default

wrote:

This does indeed look like splayed-out pancake-landing
after-jump damage, not the nose-down, drop-off-a-table,
low-speed damage that I was wondering about.


It might equally be nose level (or slightly up - or even slightly down)
hop-off-a-table, low-speed damage.

James Thomson


  #19  
Old February 14th 05, 09:05 PM
Alex Rodriguez
external usenet poster
 
Posts: n/a
Default

In article .com,
says...


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?


They need to take better pictures. Most of them are of very poor quality.
---------------
Alex

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
if you wanted maximum braking, where would you sit? wle Techniques 133 November 18th 15 03:10 AM
Still Looking for a bike [email protected] UK 19 September 5th 04 10:25 AM
Convert Hybrid to Touring bike Willy Smallboy Techniques 23 March 26th 04 02:03 PM
Who is going to Interbike? Bruce Gilbert Techniques 2 October 10th 03 09:26 PM
FAQ Just zis Guy, you know? UK 27 September 5th 03 10:58 PM


All times are GMT +1. The time now is 04:08 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 CycleBanter.com.
The comments are property of their posters.