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Scamdium strikes again!



 
 
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  #1  
Old July 25th 06, 04:20 AM posted to rec.bicycles.tech
Phil Lee, Squid
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Posts: 161
Default Scamdium strikes again!

http://weightweenies.starbike.com/ph...ic.php?t=19036

Aluminum BB axles are not a good material selection...

--
Phil Lee, Squid


  #2  
Old July 25th 06, 02:50 PM posted to rec.bicycles.tech
Tim McNamara
external usenet poster
 
Posts: 6,945
Default Scamdium strikes again!

In article m,
"Phil Lee, Squid" wrote:

http://weightweenies.starbike.com/ph...ic.php?t=19036

Aluminum BB axles are not a good material selection...


No. Especially as the left side is more prone to breaking (subject to
both torque and bending), and it will break under highest load which is
while standing on it. Then you'll get dumped into the road, possibly
right in front of a large motor vehicle.

The only time I had this happen was in 1984 when I stood up at a stop
sign to accelerate from a stop, snapped off the left side of the BB
axle, and ended up on my ass in the road. Fortunately it was a low
traffic side street. Gouged the heck out of my left ankle, too.
  #3  
Old July 25th 06, 09:35 PM posted to rec.bicycles.tech
BigBen
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Posts: 68
Default Scamdium strikes again!

On Tue, 25 Jul 2006 08:50:30 -0500, Tim McNamara
wrote:

In article m,
"Phil Lee, Squid" wrote:

http://weightweenies.starbike.com/ph...ic.php?t=19036

Aluminum BB axles are not a good material selection...


No. Especially as the left side is more prone to breaking (subject to
both torque and bending), and it will break under highest load which is


Forgive the ignorance: does that apply to hollow axle, tapered square,
XT b.brackets?

If so, which are the ones not made of aluminum?

TIA
jbr
  #4  
Old July 25th 06, 11:18 PM posted to rec.bicycles.tech
Phil Lee, Squid
external usenet poster
 
Posts: 161
Default Scamdium strikes again!

BigBen wrote:
On Tue, 25 Jul 2006 08:50:30 -0500, Tim McNamara
wrote:

In article m,
"Phil Lee, Squid" wrote:

http://weightweenies.starbike.com/ph...ic.php?t=19036

Aluminum BB axles are not a good material selection...


No. Especially as the left side is more prone to breaking (subject
to both torque and bending), and it will break under highest load
which is


Forgive the ignorance: does that apply to hollow axle, tapered square,
XT b.brackets?

If so, which are the ones not made of aluminum?


No major manufacturer makes or sells aluminum-axle bottom brackets. Your XT
bottom bracket has a steel axle.

If you look at the pictures, notice that the break does not traverse the
90-degree inner corner for most of the circumference, where one might expect
it to break. Maybe the axle was notched during installation.
--
Phil Lee, Squid


  #5  
Old July 25th 06, 11:46 PM posted to rec.bicycles.tech
Tim McNamara
external usenet poster
 
Posts: 6,945
Default Scamdium strikes again!

In article ,
(BigBen) wrote:

On Tue, 25 Jul 2006 08:50:30 -0500, Tim McNamara
wrote:

In article m,
"Phil Lee, Squid" wrote:

http://weightweenies.starbike.com/ph...ic.php?t=19036

Aluminum BB axles are not a good material selection...


No. Especially as the left side is more prone to breaking (subject
to both torque and bending), and it will break under highest load
which is


Forgive the ignorance: does that apply to hollow axle, tapered
square, XT b.brackets?


The left side of the BB axle is subject to both torque and bending
forces from the left crank. The right side of the axle is subject only
to bending forces from the right crank as the torque goes directly into
the "spider."

If so, which are the ones not made of aluminum?


Aluminum is a bad choice for BB axles period. Few are made from
aluminum, the vast majority are made from steel and a few from titanium.
  #6  
Old July 26th 06, 02:36 AM posted to rec.bicycles.tech
jim beam
external usenet poster
 
Posts: 166
Default Scamdium strikes again!

Phil Lee, Squid wrote:
http://weightweenies.starbike.com/ph...ic.php?t=19036

Aluminum BB axles are not a good material selection...

they're fine if they're dimensionally appropriate for the job. aluminum
shimano axles anyone?

the problem comes when you use the same size in aluminum as you do in
steel given aluminum's much lower strength. presence of scandium in
this situation is pretty much irrelevant.
  #7  
Old July 26th 06, 02:58 AM posted to rec.bicycles.tech
Phil Lee, Squid
external usenet poster
 
Posts: 161
Default Scamdium strikes again!

jim beam wrote:
Phil Lee, Squid wrote:
http://weightweenies.starbike.com/ph...ic.php?t=19036

Aluminum BB axles are not a good material selection...

they're fine if they're dimensionally appropriate for the job. aluminum
shimano axles anyone?

the problem comes when you use the same size in aluminum as you do in
steel given aluminum's much lower strength. presence of scandium in
this situation is pretty much irrelevant.


It was tongue in cheek, of course.

I'm curious to know what proportion of high-mileage Ksyrium SSC SL riders
get broken spokes compared to standard-spoke riders.
--
Phil Lee, Squid


  #8  
Old July 26th 06, 03:13 AM posted to rec.bicycles.tech
jim beam
external usenet poster
 
Posts: 166
Default Scamdium strikes again!

Phil Lee, Squid wrote:
jim beam wrote:
Phil Lee, Squid wrote:
http://weightweenies.starbike.com/ph...ic.php?t=19036

Aluminum BB axles are not a good material selection...

they're fine if they're dimensionally appropriate for the job. aluminum
shimano axles anyone?

the problem comes when you use the same size in aluminum as you do in
steel given aluminum's much lower strength. presence of scandium in
this situation is pretty much irrelevant.


It was tongue in cheek, of course.

I'm curious to know what proportion of high-mileage Ksyrium SSC SL riders
get broken spokes compared to standard-spoke riders.


well, those spokes are 3x the size...

interestingly, when those wheels first came out, it seemed like i'd see
someone shipwrecked with a broken aluminum spoke once or twice a month.
the last few years though, i can't say i've seen one.
  #9  
Old July 26th 06, 04:44 AM posted to rec.bicycles.tech
Phil Lee, Squid
external usenet poster
 
Posts: 161
Default Scamdium strikes again!

jim beam wrote:
Phil Lee, Squid wrote:
jim beam wrote:
Phil Lee, Squid wrote:
http://weightweenies.starbike.com/ph...ic.php?t=19036

Aluminum BB axles are not a good material selection...

they're fine if they're dimensionally appropriate for the job.
aluminum shimano axles anyone?

the problem comes when you use the same size in aluminum as you do
in steel given aluminum's much lower strength. presence of
scandium in this situation is pretty much irrelevant.


It was tongue in cheek, of course.

I'm curious to know what proportion of high-mileage Ksyrium SSC SL
riders get broken spokes compared to standard-spoke riders.


well, those spokes are 3x the size...


That's what I mean. However, with aluminum's lack of a fatigue limit...

interestingly, when those wheels first came out, it seemed like i'd
see someone shipwrecked with a broken aluminum spoke once or twice a
month. the last few years though, i can't say i've seen one.


The lack of a fatigue limit would almost ensure that higher-mileage wheels
would have constant breakages, wouldn't it?

Does the ball-and-socket method of the SSC SL spoke heads resist breakage
better when compared to the J-bend of SS spokes?

--
Phil Lee, Squid


  #10  
Old July 26th 06, 05:33 AM posted to rec.bicycles.tech
jim beam
external usenet poster
 
Posts: 166
Default Scamdium strikes again!

Phil Lee, Squid wrote:
jim beam wrote:
Phil Lee, Squid wrote:
jim beam wrote:
Phil Lee, Squid wrote:
http://weightweenies.starbike.com/ph...ic.php?t=19036

Aluminum BB axles are not a good material selection...

they're fine if they're dimensionally appropriate for the job.
aluminum shimano axles anyone?

the problem comes when you use the same size in aluminum as you do
in steel given aluminum's much lower strength. presence of
scandium in this situation is pretty much irrelevant.
It was tongue in cheek, of course.

I'm curious to know what proportion of high-mileage Ksyrium SSC SL
riders get broken spokes compared to standard-spoke riders.

well, those spokes are 3x the size...


That's what I mean. However, with aluminum's lack of a fatigue limit...


it has a definable fatigue limit, but not an endurance limit. stainless
steel doesn't have an endurance limit either, so traditional spokes have
no intrinsic advantage.


interestingly, when those wheels first came out, it seemed like i'd
see someone shipwrecked with a broken aluminum spoke once or twice a
month. the last few years though, i can't say i've seen one.


The lack of a fatigue limit would almost ensure that higher-mileage wheels
would have constant breakages, wouldn't it?


be careful of terminology. while there is a lot of confusion about
which term describes what in certain quarters, where i came from,
endurance limit describes the "knee" in the s-n graph of mild steel,
while fatigue limit describes the stress level to survive an arbitrary
number of stress cycles, say 10^7. it's the design, stress risers,
material quality, etc., that determine fatigue life more than anything
else, particularly once you get away from the simple alloys systems.
don't be afraid of properly deployed aluminum alloys - aluminum alloy
wings stay on planes for a good long time....


Does the ball-and-socket method of the SSC SL spoke heads resist breakage
better when compared to the J-bend of SS spokes?


in terms of design principle, yes it should do - no intrinsic bending.
all the broken aluminum spokes i've ever seen have broken at the
threaded end.

 




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