Scamdium strikes again!

In article <[email hidden]>,

Phil Lee said:

http://weightweenies.starbike.com/phpBB2/viewtopic.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.

Tim McNamara said:

In article <[email hidden]>,

Phil Lee said:

http://weightweenies.starbike.com/phpBB2/viewtopic.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

BigBen said:

Tim McNamara said:

In article <[email hidden]>,

Phil Lee said:

http://weightweenies.starbike.com/phpBB2/viewtopic.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

In article <[email hidden]>,

(BigBen) said:

Tim McNamara said:

In article <[email hidden]>,

Phil Lee said:

http://weightweenies.starbike.com/phpBB2/viewtopic.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."

Quoted message said:

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.

Tim McNamara said:

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."

Technically, the right side of the axle is subject to both torque and
bending forces as well; the torque has to get *to* the spider, and it
does that through the right side of the BB axle. Perhaps what you mean
is that the left side of the axle experiences bending and torsional
loads at the same time, while the right side experiences them
separately.

(That is, when the left crank is at 9:00, it exerts both bending and
torsional loads on the left side of the BB, while the right side of the
BB axle experiences only torsional loads and a small bending load from
lifting the right leg. When the right crank is at the 3:00 position,
the BB axle experiences bending only, with torsional loading coming
only from lifting the left leg).

Quoted message said:

Quoted message said:

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.

It's possible to design an aluminum bottom bracket axle that's safe for
even someone of Chalo's size, but it would have to have a larger
diameter than most (or all) current designs. Like not 19-22 mm but
rather something on the order of 50mm. Whether such a large diameter BB
is desireable is a separate question.

Tim, I don't think either of these points is news to you...I just
wanted to clarify.

Jason

Phil Lee said:

http://weightweenies.starbike.com/phpBB2/viewtopic.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.

Quoted message said:

It's possible to design an aluminum bottom bracket axle that's safe for
even someone of Chalo's size, but it would have to have a larger
diameter than most (or all) current designs. Like not 19-22 mm but
rather something on the order of 50mm. Whether such a large diameter BB
is desireable is a separate question.

As a rule of thumb, a tubular structure made from aluminum can be made
equally stiff to a steel tube of similar wall thickness if its diameter
is increased by a factor of 1.4. Furthermore, if its cross-sectional
area is increased to accomodate the difference between the tensile
strengths of the aluminum and steel in question, then the aluminum part
will almost certainly prove to be as reliable as the steel part. The
principle is well illustrated by the aluminum frames that are
ubiquitous on bicycles today.

For my part, I find cranks with 3/4" (19mm) solid CrMo spindles with
fine-pitched splines to be perfectly adequate for my needs. This
suggests that an aluminum spindle of approximately 27mm diameter with a
9.5mm wall would be adequate for me, as long as it were made of some
very strong aluminum alloy like 7075-T6, 7068-T6, 7055-T77511, or a
Scandium-doped alloy. Such a spindle could easily be fitted into an
American BB shell along with some reasonably stout bearings.

Chalo Colina

jim beam said:

Phil Lee said:

http://weightweenies.starbike.com/phpBB2/viewtopic.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

Phil Lee said:

jim beam said:

Phil Lee said:

http://weightweenies.starbike.com/phpBB2/viewtopic.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.

Chalo said:

Quoted message said:

It's possible to design an aluminum bottom bracket axle that's safe for
even someone of Chalo's size, but it would have to have a larger
diameter than most (or all) current designs. Like not 19-22 mm but
rather something on the order of 50mm. Whether such a large diameter BB
is desireable is a separate question.

As a rule of thumb, a tubular structure made from aluminum can be made
equally stiff to a steel tube of similar wall thickness if its diameter
is increased by a factor of 1.4. Furthermore, if its cross-sectional
area is increased to accomodate the difference between the tensile
strengths of the aluminum and steel in question, then the aluminum part
will almost certainly prove to be as reliable as the steel part. The
principle is well illustrated by the aluminum frames that are
ubiquitous on bicycles today.

For my part, I find cranks with 3/4" (19mm) solid CrMo spindles with
fine-pitched splines to be perfectly adequate for my needs. This
suggests that an aluminum spindle of approximately 27mm diameter with a
9.5mm wall would be adequate for me, as long as it were made of some
very strong aluminum alloy like 7075-T6, 7068-T6, 7055-T77511, or a
Scandium-doped alloy. Such a spindle could easily be fitted into an
American BB shell along with some reasonably stout bearings.

Chalo Colina

Thanks for the input, Chalo. Your math makes sense to me.

FWIW, I secretly hope that a new BB standard emerges (the American (AKA
BMX) spec would work fine) such that we could use 25-30mm aluminum
bottom bracket axles with appropriately oversized bearings. One
advantage of an Al:Al interface is that both the BB and crank would
have similar stiffnesses, reducing the incidence of creaking.

People like Peter would hate it, but I suspect we're headed that way;
Cannondale, Specialized and Pinarello already offer such BBs. I guess
my secret hope is no longer a secret.

Jason

P.S. Peter, I mean no offense by this; "people like Peter" is meant to
mean "those skeptical of change qua change" rather than "people who
hate anything new."

jim beam said:

Phil Lee said:

jim beam said:

Phil Lee, Squid wrote:
> http://weightweenies.starbike.com/phpBB2/viewtopic.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...

Quoted message said:

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

Phil Lee said:

jim beam said:

Phil Lee said:

jim beam wrote:
> Phil Lee, Squid wrote:
>> http://weightweenies.starbike.com/phpBB2/viewtopic.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.

Quoted message said:

Quoted message said:

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....

Quoted message said:

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.

"jim beam" <[email hidden]> wrote in message
news:[email hidden]...
[edit]

Quoted message said:

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....

And am I right in thinking they're held on with rivets, mostly? That got me
wondering about this cracking-round-eyelets thing that rattles on and on in
RBT. I saw someone on TV restoring an aircraft. drilling the holes for the
rivets involved at least a 3 step process (pilot, bigger drill, finishing
drill). I assumed this was to produce a smooth round hole. I'm willing to
believe that holes in rims are a one step process. This could leave a
comparatively rough and ovalised hole. Could this lead to more serious
crack propogation?

Skippy
E&OE

In article
<[email hidden]>,

Skippy said:

"jim beam" <[email hidden]> wrote in message
news:[email hidden]...
[edit]

Quoted message said:

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....

And am I right in thinking they're held on with rivets, mostly? That got me
wondering about this cracking-round-eyelets thing that rattles on and on in
RBT. I saw someone on TV restoring an aircraft. drilling the holes for the
rivets involved at least a 3 step process (pilot, bigger drill, finishing
drill). I assumed this was to produce a smooth round hole. I'm willing to
believe that holes in rims are a one step process. This could leave a
comparatively rough and ovalised hole. Could this lead to more serious
crack propogation?

Bicycle rim holes should be finished with a grommet so
machining is a negligible contribution to rim hole
failure. Experience of many people show that thick
anodizing of bicycle rims is a much greater contributor to
rim failure.

--
Michael Press

Skippy said:

"jim beam" <[email hidden]> wrote in message
news:[email hidden]...
[edit]

Quoted message said:

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....

And am I right in thinking they're held on with rivets, mostly? That got me
wondering about this cracking-round-eyelets thing that rattles on and on in
RBT. I saw someone on TV restoring an aircraft. drilling the holes for the
rivets involved at least a 3 step process (pilot, bigger drill, finishing
drill). I assumed this was to produce a smooth round hole. I'm willing to
believe that holes in rims are a one step process. This could leave a
comparatively rough and ovalised hole. Could this lead to more serious
crack propogation?

it could - the process you describe is designed to create the smoothest
surfaces possible and therefore mitigate fatigue. bike rim holes are
drilled or punched in a one-step process.

the bottom line is that rims are a component that wears in use. it
therefore has a limited lifetime. if the wear life is shorter than the
fatigue life [assuming spoke tension as specified by the rim
manufacturer], it's simply not worth the effort or expense to try
extending it even further.

Michael Press said:

In article
<[email hidden]>,

Skippy said:

"jim beam" <[email hidden]> wrote in message
news:[email hidden]...
[edit]

Quoted message said:

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....

And am I right in thinking they're held on with rivets, mostly? That got me
wondering about this cracking-round-eyelets thing that rattles on and on in
RBT. I saw someone on TV restoring an aircraft. drilling the holes for the
rivets involved at least a 3 step process (pilot, bigger drill, finishing
drill). I assumed this was to produce a smooth round hole. I'm willing to
believe that holes in rims are a one step process. This could leave a
comparatively rough and ovalised hole. Could this lead to more serious
crack propogation?

Bicycle rim holes should be finished with a grommet so
machining is a negligible contribution to rim hole
failure. Experience of many people show that thick
anodizing of bicycle rims is a much greater contributor to
rim failure.

sorry, but there's no proven connection with anodizing. the originator
of this allegation used a dye penetrant test as "proof". all dye
penetrant testing shows is that cracking is present - it is entirely
uninformative as to cause. deployment of an inappropriate test should
warn of flawed theory, but the fact that cracking is often out of plane
with any potential anodizing cracks shows just how wildly off base it
really is. please don't propagate this old wives tale any more michael.
thanks.

Michael Press said:

In article
<[email hidden]>,

Skippy said:

"jim beam" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Quoted message said:

Quoted message said:

don't be afraid of properly
deployed aluminum alloys - aluminum alloy wings stay on planes for a good
long time....

Yeah. After 15 years in service, the FAA mandates frequent inspections
for cracks with an eddy current meter. This is one of the main reasons
Airbus and Boeing are so eager to shift to carbon: not just the weight
savings, but the wait savings. Current inspection procedures for carbon
parts are visual and perhaps a tap test and nothing more. As recent
discoveries show, these are inadequate. See latest New Scientist for
the story.
Ô

jim beam said:

Michael Press wrote:

Quoted message said:

Quoted message said:

Bicycle rim holes should be finished with a grommet so
machining is a negligible contribution to rim hole
failure. Experience of many people show that thick
anodizing of bicycle rims is a much greater contributor to
rim failure.

sorry, but there's no proven connection with anodizing. the originator
of this allegation used a dye penetrant test as "proof". all dye
penetrant testing shows is that cracking is present - it is entirely
uninformative as to cause. deployment of an inappropriate test should
warn of flawed theory, but the fact that cracking is often out of plane
with any potential anodizing cracks shows just how wildly off base it
really is. please don't propagate this old wives tale any more michael.

So then maybe you can explain the tremendously failure rates between
anodized rims and the same rim without anodizing (something I've seen
even with modern "thin anodized" rims. It's OK to try to shoot holes
in theory, but unless you have some other more plausible theory, it's
all hand-waving.

I'm also curious as to what might keep anodizing from cracking "in
plane" with typical rim-killing cracks. Seems to me that the same
stresses that kill the parent material would certainly be likely to
flex the brittle anodizing enough to create a crack in the same plane.

Or is this just another "Jobst said it so I'm going to try to convince
everyone it's not true" issue?

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame

Mark Hickey said:

jim beam said:

Michael Press wrote:

Quoted message said:

Quoted message said:

Bicycle rim holes should be finished with a grommet so
machining is a negligible contribution to rim hole
failure. Experience of many people show that thick
anodizing of bicycle rims is a much greater contributor to
rim failure.

sorry, but there's no proven connection with anodizing. the originator
of this allegation used a dye penetrant test as "proof". all dye
penetrant testing shows is that cracking is present - it is entirely
uninformative as to cause. deployment of an inappropriate test should
warn of flawed theory, but the fact that cracking is often out of plane
with any potential anodizing cracks shows just how wildly off base it
really is. please don't propagate this old wives tale any more michael.

So then maybe you can explain the tremendously failure rates between
anodized rims and the same rim without anodizing (something I've seen
even with modern "thin anodized" rims. It's OK to try to shoot holes
in theory, but unless you have some other more plausible theory, it's
all hand-waving.

so what rims are available both anodized and unanodized? and what's
your data? all i've seen is a bunch of misdiagnosed assertions that
happen to coincide with "tension as high as the rim can bear".

Quoted message said:

I'm also curious as to what might keep anodizing from cracking "in
plane" with typical rim-killing cracks. Seems to me that the same
stresses that kill the parent material would certainly be likely to
flex the brittle anodizing enough to create a crack in the same plane.

study this:
http://web.onetel.net.uk/~davidwgreen/rimpics/4.JPG
the crack is not radial, it's tangential, therefore it's not initiating
from any anodizing crack. anodizing cracks, as you'll know if you've
looked at them under a magnifier, extend strictly radially from the rim
hole.

Quoted message said:

Or is this just another "Jobst said it so I'm going to try to convince
everyone it's not true" issue?

there's nothing wrong with jobst's work when it's something within his
actual sphere of knowledge. but given that that sphere is apparently
much smaller than he cares to admit, the problem comes when he starts
making flawed presumptions about stuff he doesn't actually know or can
be bothered to research. and it gets worse when he tries to b.s. a
metallurgist on basic materials theory about which he hasn't got the
faintest clue.