Ultegra Road triple crank cracks due to fatigue.



G

[email protected]

Guest
[email protected] wrote:
> http://www.pbase.com/gearoidmuar/image/63965535.jpg
>
> http://www.pbase.com/gearoidmuar/image/63965536.jpg
>
> My friend Mick Lehane had this happen today. Fortunately he was only
> slightly hurt. Chainset about 4-5 years old. Shimano Ultegra. Mick's a
> 60 year old light fit cyclist who probably does about 5000 miles per
> year on this bike.
>
> Anyone seen this happen? I never have before and I'm cycling all my
> life. I've had bottom bracket axles crack in the past
>
but do you see how scratched up that thing is??? aluminum, like most
other structural metals, is notch sensitive. if the surface of the
component is scratched and damaged, it creates a multitude of small
notches from which fatigue can nucleate and grow. it's not simply
aesthetics which dictate the surface finish on these things.

for the future, your friend has got to learn to treat this stuff with
more respect. a campy [or any other brand] crank would have failed
identically in the same circumstances. when the f.a.a. investigates an
engine falling off a plane in flight, it's not going to have an issue
with the plane's manufacturer if it finds the service crew were using a
forklift to "massage" the engine's fixing bolts into position.
 
Yes.
I'm aware of crack propogation in aluminium.

It looks to me as if the fatigue occurred in the inner half (bike side)
and the outside bit was sudden.
The inner bit looked all powdered, like a salt of aluminium.

I've never seen a crank crack before. I've had several frames crack on
me, a couple of seat-posts, axles etc.
 
[email protected] wrote:
> Yes.
> I'm aware of crack propogation in aluminium.
>
> It looks to me as if the fatigue occurred in the inner half (bike side)
> and the outside bit was sudden.
> The inner bit looked all powdered, like a salt of aluminium.
>
> I've never seen a crank crack before. I've had several frames crack on
> me, a couple of seat-posts, axles etc.

I broke this same crank about a year ago, a little higher and maybe
less mileage. I have broken six or seven cranks, mostly 70s/80s
vintage Campy NR. One Shimano -- that one. I think cranks can fatigue
from bending at the bottom of the stroke, and, in my experience, this
is a common failure mode for people who weigh more than a few pounds
and who climb out of the saddle. I have broken cranks with and without
heel/shoe polishing, and if polishing or surface scratches are enough
to cause a crank to fail, then a serious redesign is in order. I have
big feet, and there is no way I am going to avoid hitting my crank arm
somewhere with my shoes. -- Jay Beattie.
 
Jay Beattie wrote:
> [email protected] wrote:
>> Yes.
>> I'm aware of crack propogation in aluminium.
>>
>> It looks to me as if the fatigue occurred in the inner half (bike side)
>> and the outside bit was sudden.
>> The inner bit looked all powdered, like a salt of aluminium.
>>
>> I've never seen a crank crack before. I've had several frames crack on
>> me, a couple of seat-posts, axles etc.
>
> I broke this same crank about a year ago, a little higher and maybe
> less mileage. I have broken six or seven cranks, mostly 70s/80s
> vintage Campy NR. One Shimano -- that one. I think cranks can fatigue
> from bending at the bottom of the stroke, and, in my experience, this
> is a common failure mode for people who weigh more than a few pounds
> and who climb out of the saddle. I have broken cranks with and without
> heel/shoe polishing, and if polishing or surface scratches are enough
> to cause a crank to fail, then a serious redesign is in order. I have
> big feet, and there is no way I am going to avoid hitting my crank arm
> somewhere with my shoes. -- Jay Beattie.
>
my shoes are size 13, and i /never/ "polish" the crank. ever. in fact,
i find it hard to understand how it's possible if cleats are positioned
correctly.

but shoes strike is not the only problem here - the inside of the crank
is scratched to blazes by repeated chain derailment. again, i find it
hard to understand how this problem is allowed to even occur in the
first place, let alone persist to the extent that this crank has
sustained the damage seen. there is a fundamental disconnect between
this rider's actions and the perception of consequences.
 
jim beam <[email protected]> wrote in
news:[email protected]:

> [email protected] wrote:
>> http://www.pbase.com/gearoidmuar/image/63965535.jpg
>>
>> http://www.pbase.com/gearoidmuar/image/63965536.jpg
>>
>> My friend Mick Lehane had this happen today. Fortunately he was only
>> slightly hurt. Chainset about 4-5 years old. Shimano Ultegra. Mick's a
>> 60 year old light fit cyclist who probably does about 5000 miles per
>> year on this bike.
>>
>> Anyone seen this happen? I never have before and I'm cycling all my
>> life. I've had bottom bracket axles crack in the past
>>
> but do you see how scratched up that thing is??? aluminum, like most
> other structural metals, is notch sensitive. if the surface of the
> component is scratched and damaged, it creates a multitude of small
> notches from which fatigue can nucleate and grow. it's not simply
> aesthetics which dictate the surface finish on these things.
>
> for the future, your friend has got to learn to treat this stuff with
> more respect. a campy [or any other brand] crank would have failed
> identically in the same circumstances. when the f.a.a. investigates an
> engine falling off a plane in flight, it's not going to have an issue
> with the plane's manufacturer if it finds the service crew were using a
> forklift to "massage" the engine's fixing bolts into position.

I wonder if Hollowtech can be to blame; it's a delamination with sharp
corners.

--
Mike DeMicco <[email protected]>
 
Mike DeMicco wrote:
> jim beam <[email protected]> wrote in
> news:[email protected]:
>
>> [email protected] wrote:
>>> http://www.pbase.com/gearoidmuar/image/63965535.jpg
>>>
>>> http://www.pbase.com/gearoidmuar/image/63965536.jpg
>>>
>>> My friend Mick Lehane had this happen today. Fortunately he was only
>>> slightly hurt. Chainset about 4-5 years old. Shimano Ultegra. Mick's a
>>> 60 year old light fit cyclist who probably does about 5000 miles per
>>> year on this bike.
>>>
>>> Anyone seen this happen? I never have before and I'm cycling all my
>>> life. I've had bottom bracket axles crack in the past
>>>
>> but do you see how scratched up that thing is??? aluminum, like most
>> other structural metals, is notch sensitive. if the surface of the
>> component is scratched and damaged, it creates a multitude of small
>> notches from which fatigue can nucleate and grow. it's not simply
>> aesthetics which dictate the surface finish on these things.
>>
>> for the future, your friend has got to learn to treat this stuff with
>> more respect. a campy [or any other brand] crank would have failed
>> identically in the same circumstances. when the f.a.a. investigates an
>> engine falling off a plane in flight, it's not going to have an issue
>> with the plane's manufacturer if it finds the service crew were using a
>> forklift to "massage" the engine's fixing bolts into position.
>
> I wonder if Hollowtech can be to blame; it's a delamination with sharp
> corners.
>
have you ever seen the crack nucleate from inside?
 
On Sun, 23 Jul 2006 12:27:24 -0700, jim beam <[email protected]>
wrote:

>my shoes are size 13, and i /never/ "polish" the crank. ever. in fact,
>i find it hard to understand how it's possible if cleats are positioned
>correctly.

I have size 8 1/2 feet and "polish" the crank all the time. I could
adjust my cleats to not do so, and I guess that'd be "correct" in
terms of protecting the cranks, but my knees would ache.

JT

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[email protected] wrote:
> Yes.
> I'm aware of crack propogation in aluminium.
>
> It looks to me as if the fatigue occurred in the inner half (bike side)
> and the outside bit was sudden.
> The inner bit looked all powdered, like a salt of aluminium.
>
> I've never seen a crank crack before.

next time you go to a swap meet, look for the campy super record cranks
of which there are invariably always a number. unless it's n.i.b.,
it'll almost certainly be cracked where the spider meets the crank arm.

> I've had several frames crack on
> me, a couple of seat-posts, axles etc.
>
 
John Forrest Tomlinson wrote:
> On Sun, 23 Jul 2006 12:27:24 -0700, jim beam <[email protected]>
> wrote:
>
>> my shoes are size 13, and i /never/ "polish" the crank. ever. in fact,
>> i find it hard to understand how it's possible if cleats are positioned
>> correctly.
>
> I have size 8 1/2 feet and "polish" the crank all the time. I could
> adjust my cleats to not do so, and I guess that'd be "correct" in
> terms of protecting the cranks, but my knees would ache.

that's a bummer. you'll have to budget for a regular crank replacement
program if you want to minimize the risk of failure and injury.
 
On Sun, 23 Jul 2006 13:46:17 -0700, jim beam <[email protected]>
wrote:

>John Forrest Tomlinson wrote:
>> On Sun, 23 Jul 2006 12:27:24 -0700, jim beam <[email protected]>
>> wrote:
>>
>>> my shoes are size 13, and i /never/ "polish" the crank. ever. in fact,
>>> i find it hard to understand how it's possible if cleats are positioned
>>> correctly.
>>
>> I have size 8 1/2 feet and "polish" the crank all the time. I could
>> adjust my cleats to not do so, and I guess that'd be "correct" in
>> terms of protecting the cranks, but my knees would ache.
>
>that's a bummer. you'll have to budget for a regular crank replacement
>program if you want to minimize the risk of failure and injury.

How about some pedal extensions?
 
On Sun, 23 Jul 2006 13:46:17 -0700, jim beam <[email protected]>
wrote:

>John Forrest Tomlinson wrote:
>> On Sun, 23 Jul 2006 12:27:24 -0700, jim beam <[email protected]>
>> wrote:
>>
>>> my shoes are size 13, and i /never/ "polish" the crank. ever. in fact,
>>> i find it hard to understand how it's possible if cleats are positioned
>>> correctly.
>>
>> I have size 8 1/2 feet and "polish" the crank all the time. I could
>> adjust my cleats to not do so, and I guess that'd be "correct" in
>> terms of protecting the cranks, but my knees would ache.
>
>that's a bummer. you'll have to budget for a regular crank replacement
>program if you want to minimize the risk of failure and injury.

Yes.

JT

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Remove "remove" to reply
Visit http://www.jt10000.com
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On Sun, 23 Jul 2006 21:43:59 GMT, R Brickston
<rb20170REMOVE.yahoo.com@> wrote:

>On Sun, 23 Jul 2006 13:46:17 -0700, jim beam <[email protected]>
>wrote:
>
>>John Forrest Tomlinson wrote:
>>> On Sun, 23 Jul 2006 12:27:24 -0700, jim beam <[email protected]>
>>> wrote:
>>>
>>>> my shoes are size 13, and i /never/ "polish" the crank. ever. in fact,
>>>> i find it hard to understand how it's possible if cleats are positioned
>>>> correctly.
>>>
>>> I have size 8 1/2 feet and "polish" the crank all the time. I could
>>> adjust my cleats to not do so, and I guess that'd be "correct" in
>>> terms of protecting the cranks, but my knees would ache.
>>
>>that's a bummer. you'll have to budget for a regular crank replacement
>>program if you want to minimize the risk of failure and injury.
>
>How about some pedal extensions?

That changes the mechanics of pedalling substantially. Might work for
some people but not not for me.

JT


****************************
Remove "remove" to reply
Visit http://www.jt10000.com
****************************
 
On 24 Jul 2006 01:10:10 GMT, Mike DeMicco
<[email protected]> wrote:

>jim beam <[email protected]> wrote in
>news:p[email protected]:
>
>> Mike DeMicco wrote
>>>
>>> I wonder if Hollowtech can be to blame; it's a delamination with
>>> sharp corners.
>>>
>> have you ever seen the crack nucleate from inside?
>
>Don't know. From the pictures shown, how can one tell?

Dear Mike,

In this picture . . .

http://www.pbase.com/gearoidmuar/image/63965536.jpg

.. . . the start of the failure seems obvious, given the classic
beachmark pattern expanding from the initial point of failure on the
pedal side.

Cheers,

Carl Fogel
 
jim beam wrote:

<snip>

> my shoes are size 13, and i /never/ "polish" the crank. ever. in fact,
> i find it hard to understand how it's possible if cleats are positioned
> correctly.

It's easy -- size 13 mountain bike shoes and neoprene or rubberized
fabric (Sugoi) booties for four (or more) months of the year. They add
a lot of bulk. I also have mobile ankles. By the way, I put probably
40K on an '80s Dura Ace crank which was beaten and polished, and it
never broke. I thought the Japanese cranks were pretty tough until I
broke the Ultegra triple. I am a little suspicious of the hollow
technology. -- Jay Beattie.
 
Jay Beattie wrote:
> jim beam wrote:
>
> <snip>
>
>> my shoes are size 13, and i /never/ "polish" the crank. ever. in fact,
>> i find it hard to understand how it's possible if cleats are positioned
>> correctly.
>
> It's easy -- size 13 mountain bike shoes and neoprene or rubberized
> fabric (Sugoi) booties for four (or more) months of the year. They add
> a lot of bulk. I also have mobile ankles. By the way, I put probably
> 40K on an '80s Dura Ace crank which was beaten and polished, and it
> never broke. I thought the Japanese cranks were pretty tough until I
> broke the Ultegra triple. I am a little suspicious of the hollow
> technology. -- Jay Beattie.
>
if fatigue was nucleating from inside, i'd say sure, but with the case
we see here, there is no difference compared to the failure you'd see in
a solid section. i therefore have no fear of hollowtech cranks.
indeed, i love their stiffness.
 
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