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Snapped Bottom Bracket Spindle?



 
 
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  #1  
Old October 22nd 07, 08:45 PM posted to rec.bicycles.tech
Prague Tech
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Posts: 2
Default Snapped Bottom Bracket Spindle?

Hey All,

I was working my regular pedicab driver shift the other day,
accelerating from a stop light with 3 large guys seated in my trailer
type pedicab. I sort of jumped forward in an unexpected way and heard
a scattering, clank-clank. I then noticed the my left pedal was
missing. Then I noticed my left crank arm, and the end of the bottom
bracket spindle that would normally keep the afore mentioned parts
attached were gone too. Upon inspection, the missing bottom bracket
stub was still pressed into the crank arm that I was holding in my
hands. In spite of my displeasure of not being able to earn more
money that night dragging drunken louts to their next whisky bar, I
was amused by the massive power I exhibited by ripping the crank
nipple right off.

So here is my question:
Was it really my massive lower body prowess that killed this BB
spindle? Or is it that Shimano is making crappy spindles that shread
after 5 months? Or is the pedicabbing I do on this bike just that
hard on the torquey bits?

Perhaps it was a combination of the three. I bring this to the R.B.T
group as none of my pedicabber buddies have had this particular
mechanical failure before. Chalo on the other hand has done it a few
times before resulting in his oh-so-fashionable grillz. (him 300+ lbs)

-Ken Cameron
humble neighborhood pedicabber

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  #2  
Old October 22nd 07, 10:44 PM posted to rec.bicycles.tech
[email protected]
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Posts: 3,751
Default Snapped Bottom Bracket Spindle?

Ken Cameron writes:

I was working my regular pedicab driver shift the other day,
accelerating from a stop light with 3 large guys seated in my
trailer type pedicab. I sort of jumped forward in an unexpected way
and heard a scattering, clank-clank. I then noticed the my left
pedal was missing. Then I noticed my left crank arm, and the end of
the bottom bracket spindle that would normally keep the afore
mentioned parts attached were gone too. Upon inspection, the
missing bottom bracket stub was still pressed into the crank arm
that I was holding in my hands. In spite of my displeasure of not
being able to earn more money that night dragging drunken louts to
their next whisky bar, I was amused by the massive power I exhibited
by ripping the crank nipple right off.


So here is my question:


Was it really my massive lower body prowess that killed this BB
spindle? Or is it that Shimano is making crappy spindles that
shred after 5 months? Or is the pedicabbing I do on this bike just
that hard on the torquey bits?


Perhaps it was a combination of the three. I bring this to the
R.B.T group as none of my pedicabber buddies have had this
particular mechanical failure before. Chalo on the other hand has
done it a few times before resulting in his oh-so-fashionable
grillz. (him 300+ lbs)


Although such spindles are usually hardened so they can take the high
contact stress of their bearing balls, this is most surely a fatigue
failure that was the summation of many loaded torque repetitions.
You'll note that only the torque of the left foot goes through the
spindle, the right foot going directly into the chain. The fracture
should be a slightly helical crack, part of which is at 45° to the
spindle.

Low quality material and/or heat treatment.

Jobst Brandt
  #3  
Old October 23rd 07, 05:25 AM posted to rec.bicycles.tech
jim beam
external usenet poster
 
Posts: 5,758
Default Snapped Bottom Bracket Spindle?

Prague Tech wrote:
Hey All,

I was working my regular pedicab driver shift the other day,
accelerating from a stop light with 3 large guys seated in my trailer
type pedicab. I sort of jumped forward in an unexpected way and heard
a scattering, clank-clank. I then noticed the my left pedal was
missing. Then I noticed my left crank arm, and the end of the bottom
bracket spindle that would normally keep the afore mentioned parts
attached were gone too. Upon inspection, the missing bottom bracket
stub was still pressed into the crank arm that I was holding in my
hands. In spite of my displeasure of not being able to earn more
money that night dragging drunken louts to their next whisky bar, I
was amused by the massive power I exhibited by ripping the crank
nipple right off.

So here is my question:
Was it really my massive lower body prowess that killed this BB
spindle? Or is it that Shimano is making crappy spindles that shread
after 5 months? Or is the pedicabbing I do on this bike just that
hard on the torquey bits?


impossible to say for sure without quality pics of the installation and
the break. shimano are not known for spindle breakage so i'm interested
to see if there was any damage to it that could have initiated metal
fatigue.



Perhaps it was a combination of the three. I bring this to the R.B.T
group as none of my pedicabber buddies have had this particular
mechanical failure before. Chalo on the other hand has done it a few
times before resulting in his oh-so-fashionable grillz. (him 300+ lbs)

-Ken Cameron
humble neighborhood pedicabber

  #4  
Old October 23rd 07, 07:46 PM posted to rec.bicycles.tech
Lou Holtman
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Posts: 627
Default Snapped Bottom Bracket Spindle?

Jambo wrote:
"jim beam" wrote in message
...
Prague Tech wrote:


So here is my question:
Was it really my massive lower body prowess that killed this BB
spindle? Or is it that Shimano is making crappy spindles that shread
after 5 months? Or is the pedicabbing I do on this bike just that
hard on the torquey bits?

impossible to say for sure without quality pics of the installation and
the break. shimano are not known for spindle breakage so i'm interested
to see if there was any damage to it that could have initiated metal
fatigue.


And what, give us all the "benefit" of your "metarials skool" training? No
thanks, beamboy, he might as well ask a 3yo.




Boy, you are annoying.

Lou
--
Posted by news://news.nb.nu (http://www.nb.nu)
  #5  
Old October 23rd 07, 08:45 PM posted to rec.bicycles.tech
Prague Tech
external usenet poster
 
Posts: 2
Default Snapped Bottom Bracket Spindle?

On Oct 22, 11:25 pm, jim beam wrote:

impossible to say for sure without quality pics of the installation and
the break. shimano are not known for spindle breakage so i'm interested
to see if there was any damage to it that could have initiated metal
fatigue.


I will try to get some pics of the busted bits before the reinstall. As for the install, It came on this bike from a very trustworthy LBS 5 months ago. The BB had not been removed. I had tightened the crank bolts after pulling the crank and adding new chain ring.


Although such spindles are usually hardened so they can take the high
contact stress of their bearing balls, this is most surely a fatigue
failure that was the summation of many loaded torque repetitions.
You'll note that only the torque of the left foot goes through the
spindle, the right foot going directly into the chain. The fracture
should be a slightly helical crack, part of which is at 45° to the
spindle.


Low quality material and/or heat treatment.


Jobst Brandt


You called it.

  #6  
Old October 23rd 07, 10:00 PM posted to rec.bicycles.tech
[email protected]
external usenet poster
 
Posts: 3,092
Default Snapped Bottom Bracket Spindle?

On Oct 22, 12:45 pm, Prague Tech wrote:

So here is my question:
Was it really my massive lower body prowess that killed this BB
spindle? Or is it that Shimano is making crappy spindles that shread
after 5 months? Or is the pedicabbing I do on this bike just that
hard on the torquey bits?

Perhaps it was a combination of the three. I bring this to the R.B.T
group as none of my pedicabber buddies have had this particular
mechanical failure before. Chalo on the other hand has done it a few
times before resulting in his oh-so-fashionable grillz. (him 300+ lbs)

-Ken Cameron
humble neighborhood pedicabber


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

Scroll down to the bottom for the spindles. If a spindle's going
to fail, it seems like pedicabbing is a likely place - you probably
exert a frequent high startup torque. The BB spindle is a little
undersized for high load applications. The expensive cure for
this is a different spindle system. Other than that, it's possible
that avoiding the cheaper BBs helps (I have no evidence that
better BBs are made from stronger stuff, though) and periodic
inspection might help, though that is a nuisance with BB spindles.

Ben

  #7  
Old October 24th 07, 12:48 AM posted to rec.bicycles.tech
Ozark Bicycle
external usenet poster
 
Posts: 3,591
Default Snapped Bottom Bracket Spindle?

On Oct 23, 4:04 pm, "Jambo" [email protected] wrote:
"Lou Holtman" wrote in message

...



Jambo wrote:
"jim beam" wrote in message
...
Prague Tech wrote:


So here is my question:
Was it really my massive lower body prowess that killed this BB
spindle? Or is it that Shimano is making crappy spindles that shread
after 5 months? Or is the pedicabbing I do on this bike just that
hard on the torquey bits?
impossible to say for sure without quality pics of the installation and
the break. shimano are not known for spindle breakage so i'm interested
to see if there was any damage to it that could have initiated metal
fatigue.


And what, give us all the "benefit" of your "metarials skool" training?
No thanks, beamboy, he might as well ask a 3yo.


Boy, you are annoying.


A bonus effect with beamboy. But what's it got to do with you?



You *are* playing to the audience, aren't you, Jambozo?


  #8  
Old October 24th 07, 04:43 AM posted to rec.bicycles.tech
jim beam
external usenet poster
 
Posts: 5,758
Default Snapped Bottom Bracket Spindle?

Prague Tech wrote:
On Oct 22, 11:25 pm, jim beam wrote:
impossible to say for sure without quality pics of the installation and
the break. shimano are not known for spindle breakage so i'm interested
to see if there was any damage to it that could have initiated metal
fatigue.


I will try to get some pics of the busted bits before the reinstall. As for the install, It came on this bike from a very trustworthy LBS 5 months ago. The BB had not been removed. I had tightened the crank bolts after pulling the crank and adding new chain ring.


Although such spindles are usually hardened so they can take the high
contact stress of their bearing balls, this is most surely a fatigue
failure that was the summation of many loaded torque repetitions.
You'll note that only the torque of the left foot goes through the
spindle, the right foot going directly into the chain. The fracture
should be a slightly helical crack, part of which is at 45� to the
spindle.


Low quality material and/or heat treatment.


if that were true, it would be a common occurrence. but it's not. and
it's not excess torque either - the rider can exert no more torque on
the crank end of a pedicab than on any other bike.



Jobst Brandt


You called it.

 




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