disk caliper redux

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

Quoted message said:

since the previous thread is now too deep for me to follow on a threaded
newsreader, here's a summary of one side of the debate so far:

1. front mounted calipers for mtb forks are a bad idea because the
material from which they're made has poor tensile fatigue properties.

2. it is possible to manufacture from different much more expensive
materials to accommodate a front caliper, but the cost and/or weight
penalty are unattractive, especially since the rear caliper solution is so
obvious and simple.

3. complaining about fork design is a red herring. through axle options
already exist for the hammer heads. "angled" dropout options still don't
address the only real causes of alleged wheel ejection - quick release
failure or operator error.

as with many other engineering situations, there are multiple solutions to
a problem. bridges for example. there are some bridges that use
materials in compression, others use materials in tension. but you
wouldn't dream of using compression materials in tension. same principle
applies to suspension forks - the design has to accommodate the materials
used. failure to recognize something so basic by those supposed to be
schooled in engineering is a tragic failure of our education system.

I fixed your post for you. HTH.

clive

jim beam said:

since the previous thread is now too deep for me to follow on a threaded
newsreader, here's a summary of the debate so far:

1. front mounted calipers for mtb forks are a bad idea because the
material from which they're made has poor tensile fatigue properties.

If the caliper is on an IS mount, then the bolts joining the caliper to
the tab welded onto the fork are in shear stress-- this is true whether
the tab is on the front or the rear of the fork?

I would also expect a similar kind of shearing cycle in both cases on
the caliper body itself, where the bolts attach to it.

But the weld connecting the tab to the fork is getting a tensile fatigue
cycle for a front caliper, and compressive for a rear one.

For a "post mount", the weld connecting the post to the fork, and the
bolts connecting the caliper to the post are in a tensile cycle for
front or compressive for rear. If the bolts go through the caliper to
heads on the other side, then won't the actual caliper will be in a
compressive cycle if it's on the front?

In article <[email hidden]>,

jim beam said:

since the previous thread is now too deep for me to follow on a
threaded newsreader, here's a summary of the debate so far:

Indeed, it was. "Snipping" extraneous material is the standard way to
manage this, but you and a couple of others don't do it.

Quoted message said:

1. front mounted calipers for mtb forks are a bad idea because the
material from which they're made has poor tensile fatigue properties.

Suspension forks seem to be made from different materials by different
manufacturers. Which one(s) are you referring to?

Quoted message said:

2. it is possible to manufacture from different much more expensive
materials to accommodate a front caliper, but the cost and/or weight
penalty are unattractive, especially since the rear caliper solution
is so obvious and simple.

Obviously and simply flawed, you mean.

Quoted message said:

3. complaining about fork design is a red herring. through axle
options already exist for the hammer heads. "angled" dropout options
still don't address the only real causes of alleged wheel ejection -
quick release failure or operator error.

First you contradict yourself- saying that fork design is a red herring
and then attempting to prove this by pointing to an alternative fork
design that renders the ejection force moot! It's a tacit admission of
the design flaw.

Then you treat conjecture as fact again, claiming that the *only* real
causes of "alleged" wheel ejection are "quick releaser failure" and
"operator error." All it would take is one ejection not caused by
either of those situations to collapse your house of cards. There is
already anecdotal evidence and some crudely performed experiments that
certainly appear to contradict you.

You continue to start with your conclusion ("Annan and Brandt are
wrong"😉 and work your way backwards from there. That's how you keep
getting yourself into corners.

Quoted message said:

as with many other engineering situations, there are multiple
solutions to a problem. bridges for example. there are some bridges
that use materials in compression, others use materials in tension.
but you wouldn't dream of using compression materials in tension.
same principle applies to suspension forks - the design has to
accommodate the materials used.

The materials used have to accommodate the design. That's why engineers
choose between different materials for different applications. If no
appropriate material is available, that limits the design options.
Since forks with the disk brake caliper mounted forwards already exist
and perform successfully, there is no reason to accept your claims that
such a design is inappropriate.

Quoted message said:

failure to recognize something so basic by those supposed to be
schooled in engineering is a tragic failure of our education system.

Apparently the same problems apply to metallurgical education.

Tim McNamara said:

In article <[email hidden]>,

jim beam said:

since the previous thread is now too deep for me to follow on a
threaded newsreader, here's a summary of the debate so far:

Indeed, it was. "Snipping" extraneous material is the standard way to
manage this, but you and a couple of others don't do it.

[snip]

Dear Tim,

You've misunderstood the problem, which has nothing to do with
snipping.

When there are so many replies to replies, the thread tree becomes
unwieldy. Many threaded newsreaders have a limit to how they display
the tree and stop indenting at some point.

For example, my older version of Forte Free Agent just stops indenting
after some limit--I think that it's 32 replies-to-replies.

Instead of this, where C is the 32nd reply to a reply

A
B
C
L
M
N
X
Y
Z

It shows this:

A
B
C
L
M
N
X
Y
Z

You can no longer tell at a glance that Y and Z reply to X.

If you look at the original thread in Google Groups, you can see
another way of handling an excessively deep thread tree:

http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/879729f063acfce8/9b0543f5ab444ce6#9b0543f5ab444ce6

Page down to posts 272/273, and you'll see a section where there are
lots of huge indentations. My post 273 is a reply to post 272 above
it, from dabac, but the indentation doesn't show this.

Instead, dabac's post has been indented as far to the right as
Google's display allows, so my reply to his post is shoved all the way
back to the left side of the tree (with no explanation).

Google turns what should be this:

A
B
C
D
E

into this:

A
B
C
D
E

You can no longer tell that E replies to D.

Again, it has nothing to do with snipping, just with how to indent to
show which post the next post replies to. Snipping doesn't affect the
thread-tree/message-list display.

I think that Jim Beam's suggestion to start a new thread is one good
solution to problem of a thread that's gotten so deeply indented on a
tree display that following it becomes difficult.

Cheers,

Carl Fogel

jim beam said:

since the previous thread is now too deep for me to follow on a threaded
newsreader,

Hmm. You have as much trouble following threads as you do trimming
posts, I see.

Quoted message said:

here's a summary of the debate so far:

Rather, a summary of your opinions.

Quoted message said:

1. front mounted calipers for mtb forks are a bad idea because the
material from which they're made has poor tensile fatigue properties.

IOW, they're made from the same material that front mount motorcycle
forks use to successfully resist tensile fatigue under tremendously
greater loads. Those guys at Honda must have had some unusually
capable metallurgists!

Quoted message said:

2. it is possible to manufacture from different much more expensive
materials to accommodate a front caliper,...

Yep. Like cast aluminum alloys! Pretty wild stuff!

Quoted message said:

but the cost and/or weight penalty are unattractive,

How many grams would you estimate, jim? You've never said. My guess
is fifteen grams.

Quoted message said:

3. complaining about fork design is a red herring. through axle options
already exist for the hammer heads.

Then disk and fork manufacturers should clearly explain "This fork is
not to be used for long bumpy downhill off-road riding. A dangerous
condition could result, including serious bodily harm." That should
help sales!

Quoted message said:

"angled" dropout options still
don't address the only real causes of alleged wheel ejection - quick
release failure or operator error.

Begging the question much?

Quoted message said:

as with many other engineering situations, there are multiple solutions
to a problem. bridges for example. there are some bridges that use
materials in compression, others use materials in tension. but you
wouldn't dream of using compression materials in tension. same
principle applies to suspension forks - the design has to accommodate
the materials used. failure to recognize something so basic by those
supposed to be schooled in engineering is a tragic failure of our
education system.

I'm trying to figure how someone got through a metallurgy program
without understanding tensile stress, and without understanding that
aluminum (and even magnesium) can successfully fight tensile fatigue -
IOW, that it's done every day!

- Frank Krygowski

In article <[email hidden]>,

Quoted message said:

Tim McNamara said:

In article <[email hidden]>,

jim beam said:

since the previous thread is now too deep for me to follow on a
threaded newsreader, here's a summary of the debate so far:

Indeed, it was. "Snipping" extraneous material is the standard way to
manage this, but you and a couple of others don't do it.

[snip]

Dear Tim,

You've misunderstood the problem, which has nothing to do with
snipping.

When there are so many replies to replies, the thread tree becomes
unwieldy. Many threaded newsreaders have a limit to how they display
the tree and stop indenting at some point.

For example, my older version of Forte Free Agent just stops indenting
after some limit--I think that it's 32 replies-to-replies.

I guess stand corrected. My newsreader doesn't seem to have this
problem, so your explanation makes little sense to me. I don't know
offhand what newsreader jim is using. Mine threads by references so
it's pretty easy to keep track. Counting quote strings is pretty easy,
although some newsreaders goof things up by inserting spaces (> >
instead of >>😉 into the quote string and not inserting a newline between
quoted material and new material, both of which make it harder to keep
track.

Quoted message said:

I think that Jim Beam's suggestion to start a new thread is one good
solution to problem of a thread that's gotten so deeply indented on a
tree display that following it becomes difficult.

I agree that clearing out from the detritus of the old thread was a very
good idea.

Tim McNamara said:

In article <[email hidden]>,

Quoted message said:

On Fri, 16 Feb 2007 10:19:12 -0600, Tim McNamara
<[email hidden]> wrote:

Quoted message said:

Quoted message said:

In article <[email hidden]>,
jim beam <[email hidden]> wrote:

Quoted message said:

Quoted message said:

> since the previous thread is now too deep for me to follow on a
> threaded newsreader, here's a summary of the debate so far:

Quoted message said:

Quoted message said:

Indeed, it was. "Snipping" extraneous material is the standard way to
manage this, but you and a couple of others don't do it.

Quoted message said:

[snip]

Quoted message said:

Dear Tim,

Quoted message said:

You've misunderstood the problem, which has nothing to do with
snipping.

Quoted message said:

When there are so many replies to replies, the thread tree becomes
unwieldy. Many threaded newsreaders have a limit to how they display
the tree and stop indenting at some point.

Quoted message said:

For example, my older version of Forte Free Agent just stops indenting
after some limit--I think that it's 32 replies-to-replies.

I guess stand corrected. My newsreader doesn't seem to have this
problem, so your explanation makes little sense to me. I don't know
offhand what newsreader jim is using. Mine threads by references so
it's pretty easy to keep track. Counting quote strings is pretty easy,
although some newsreaders goof things up by inserting spaces (> >
instead of >>😉 into the quote string and not inserting a newline between
quoted material and new material, both of which make it harder to keep
track.

Quoted message said:

I think that Jim Beam's suggestion to start a new thread is one good
solution to problem of a thread that's gotten so deeply indented on a
tree display that following it becomes difficult.

I agree that clearing out from the detritus of the old thread was a very
good idea.

Dear Tim,

Interesting--the MT-NewsWatcher that you use on a Mac seems to get
around the problem.

Just to point out how diverse things are, here's what posters in this
short thread seem to be using:

Jim Beam Thunderbird Linux
Tim McNamara MT-NewsWatcher Mac
Carl Fogel Forte Free Agent Windows
Clive George Outlook Express Windows
Ben C slrn Linux
Frank Krygowski Mozilla Window
Carl Fogel Google Groups Windows

I may be misreading some header details, but it looks as if the six
posters in this thread each use a different program to post--and one
poster even uses two.

Last month, the most popular newsreader among the ten most prolific
recent posters was Thunderbird, which is what Jim Beam uses:

http://groups.google.com/group/rec.bicycles.tech/msg/61324650bd9e37f4

As for snipping, it's a vexing problem.

Many posters like to intersperse their comments. I find this harder to
read, but I can scarcely complain that they're too lazy to compose a
separate reply when I'm too lazy myself to snip everything extraneous
(or reduce my own sprawling blather).

My iron-clad rule is to snip if I feel like it and to repeat myself
whenever some unspeakable imbecile dares to remove the series of
typographical errors that were the heart of my argument.

Unfortunately, no matter how sensibly you snip, you'll eventually end
up facing silly complaints that whatever was snipped was absolutely
crucial and even accusations that your snipping deliberately distorted
things.

Even stranger, some posters will delete embarrassing posts from Google
Groups, leaving the unsnipped reply as the only easy place to show
what was going on.

Cheers,

Carl Fogel

Ben C said:

jim beam said:

since the previous thread is now too deep for me to follow on a threaded
newsreader, here's a summary of the debate so far:

1. front mounted calipers for mtb forks are a bad idea because the
material from which they're made has poor tensile fatigue properties.

If the caliper is on an IS mount, then the bolts joining the caliper to
the tab welded onto the fork are in shear stress-- this is true whether
the tab is on the front or the rear of the fork?

yes. there is a small bending component, but the tabs have a large
enough platform that bending is trivial.

Quoted message said:

I would also expect a similar kind of shearing cycle in both cases on
the caliper body itself, where the bolts attach to it.

not really - the caliper is a separate body. it can come apart, but
usually, calipers have to be relatively robust to withstand their
hydraulic loads, so most of the time the caliper's mounting points are
not too much of a problem.

Quoted message said:

But the weld connecting the tab to the fork is getting a tensile fatigue
cycle for a front caliper, and compressive for a rear one.

yes. again, there is a bending component, but primary is as stated.

Quoted message said:

For a "post mount", the weld connecting the post to the fork, and the
bolts connecting the caliper to the post are in a tensile cycle for
front or compressive for rear.

yes.

Quoted message said:

If the bolts go through the caliper to
heads on the other side, then won't the actual caliper will be in a
compressive cycle if it's on the front?

the bolts will compress it in the region of the clamp, but the load is
net tensile. if i understand your description correctly.

jim beam said:

3. complaining about fork design is a red herring. through axle options
already exist for the hammer heads. "angled" dropout options still
don't address the only real causes of alleged wheel ejection - quick
release failure or operator error.

The same could be said for upward-facing dropout slots. (I have seen
these on some tallbikes and choppers using upside-down frames.) If
you keep everything tightened properly it works fine. But why make it
that way when doing it right is just as easy?

Chalo

Chalo said:

jim beam said:

3. complaining about fork design is a red herring. through axle options
already exist for the hammer heads. "angled" dropout options still
don't address the only real causes of alleged wheel ejection - quick
release failure or operator error.

The same could be said for upward-facing dropout slots. (I have seen
these on some tallbikes and choppers using upside-down frames.) If
you keep everything tightened properly it works fine. But why make it
that way when doing it right is just as easy?

Chalo

i'll accept angled drops. i've said that before. but i won't accept
front disk calipers. can't say i'm wild about front rim calipers either
come to that.

On Fri, 16 Feb 2007 18:22:07 -0800, jim beam
<[email hidden]> wrote:

[snip]

Quoted message said:

2. that the stress/strain graph quoted for deformation theory is for a
different material to that from spokes are actually made - as shown in
different subsequent actual tensile samples graphs?

[snip]

Dear Jim,

For the benefit of puzzled readers . . .

In Jobst's book "The Bicycle Wheel," there's a stress-strain graph
showing a yield step or notch, meaning a section in the upward curve
where things behave oddly:

^ x
| x
stress- x
tension x
x
x x
x x x
x
strain-elongation -->

But no such notch appears on the stress-strain graphs of various
spokes being pulled apart in the back of the book in any edition (the
first edition includes carbon spokes, as well as modern stainless
steel spokes).

For what it's worth, the second mechanical engineering professor that
I caught unawares listened to my efforts to describe this point and
said that the yield notch appears in both carbon and stainless steel,
but that it's so tiny in all cases that it takes extraordinarily
precise measurements to reveal it in any specimen.

I haven't checked whether the professor's off-hand comments are
correct, but if they are, it would suggest that the diagram showing
the yield notch is greatly exaggerated and that it would not show up
in practical testing of spokes being pulled apart.

Readers are spared the usual pedantic footnoting of various editions
because my new spoke tension gauge, two editions of "The Bicycle
Wheel," and other materials are still in the professor's hands while
he considers whether he can justify making students perform some tests
that I have in mind.

Possibly someone will provide some links to actual stress-strain
graphs with scales showing how large or small the yield notch is and
whether it appears in stainless steel.

Cheers,

Carl Fogel

Quoted message said:

On Fri, 16 Feb 2007 18:22:07 -0800, jim beam
<[email hidden]> wrote:

[snip]

Quoted message said:

2. that the stress/strain graph quoted for deformation theory is for a
different material to that from spokes are actually made - as shown in
different subsequent actual tensile samples graphs?

[snip]

Dear Jim,

For the benefit of puzzled readers . . .

In Jobst's book "The Bicycle Wheel," there's a stress-strain graph
showing a yield step or notch, meaning a section in the upward curve
where things behave oddly:

^ x
| x
stress- x
tension x
x
x x
x x x
x
strain-elongation -->

But no such notch appears on the stress-strain graphs of various
spokes being pulled apart in the back of the book in any edition (the
first edition includes carbon spokes, as well as modern stainless
steel spokes).

For what it's worth, the second mechanical engineering professor that
I caught unawares listened to my efforts to describe this point and
said that the yield notch appears in both carbon and stainless steel,
but that it's so tiny in all cases that it takes extraordinarily
precise measurements to reveal it in any specimen.

I haven't checked whether the professor's off-hand comments are
correct, but if they are, it would suggest that the diagram showing
the yield notch is greatly exaggerated and that it would not show up
in practical testing of spokes being pulled apart.

to get a "yield notch", you need an interstitial dislocation locking
mechanism - carbon in mild steel and oxygen in titanium - something
stainless steels typically don't have. we had an example a while back
for stainless at 500F, but at that temperature, there are other possible
explanations.

yes, good rigid tensile testing machines are needed to show this effect,
but i believe jobst had access to one. to be fair, he's far from unique
in this kind of misunderstanding. it's typical to educate engineers on
the properties of mild steel and the subsequent assumption therefore is
that anything with the word "steel" in it behaves the same, despite
radical differences in a number of other regards, not least of which
being crystallography. it's just like engineers regularly assuming
fatigue endurance in "steel" as something on which they can rely for
design purposes. fact is, only mild steels have this property and the
high strength high alloy steels don't.

Quoted message said:

Readers are spared the usual pedantic footnoting of various editions
because my new spoke tension gauge, two editions of "The Bicycle
Wheel," and other materials are still in the professor's hands while
he considers whether he can justify making students perform some tests
that I have in mind.

Possibly someone will provide some links to actual stress-strain
graphs with scales showing how large or small the yield notch is and
whether it appears in stainless steel.

Cheers,

Carl Fogel

Quoted message said:

On Fri, 16 Feb 2007 18:22:07 -0800, jim beam

<[email hidden]> wrote:

[snip]

Quoted message said:

2. that the stress/strain graph quoted for deformation theory is for a
different material to that from spokes are actually made - as shown in
different subsequent actual tensile samples graphs?

[snip]

Dear Jim,

For the benefit of puzzled readers . . .

In Jobst's book "The Bicycle Wheel," there's a stress-strain graph
showing a yield step or notch, meaning a section in the upward curve
where things behave oddly:

^ x
| x
stress- x
tension x
x
x x
x x x
x
strain-elongation -->

But no such notch appears on the stress-strain graphs of various
spokes being pulled apart in the back of the book in any edition (the
first edition includes carbon spokes, as well as modern stainless
steel spokes).

Unless jim has zero knowledge of metallurgy (which I doubt) he's doing
his usual: raising red herrings and false representations in a
compulsive attempt to look smarter than Jobst.

Jobst's stress-strain curve on p.32 - the one with the notch - is not
presented as representing any particular alloy. In fact, it's a
standard "first introduction" curve, used to explain the concepts to a
beginner, and it contains that yield notch because the notch is a
feature of mild steel, which is the most common metal used in
manufacturing. For web examples, see http://en.wikipedia.org/wiki/Stress-strain_curve
or http://tinyurl.com/2qhxut
or http://tinyurl.com/35th8a

In almost any engineering book on material properties, that curve is
printed in the first couple chapters, and almost every author chooses
to show the notch just as Jobst has done. But again, the curve is
printed as a general example and introduction to concepts - exactly
what Jobst has done. If it matters, the author might point out that
(most) other metals don't have the notch. My guess is that Jobst
didn't mention it because it has no importance in bicycle wheels.

In the back of _The Bicycle Wheel_ Jobst gives specific curves for
spoke alloys. Those curves are not intended to be general, but
specific to those test results. Those metals don't display the notch,
so of course the notch is not shown. His curves appear to be
accurate.

I'm not surprised that Carl doesn't know this. It's the kind of thing
one learns in metallurgy and/or engineering classes, not English
classes.

But jim beam obviously should know this. As usual, his portrayal of
this as a mistake on Jobst's part is dishonest and cowardly.

- Frank Krygowski

Quoted message said:

Quoted message said:

On Fri, 16 Feb 2007 18:22:07 -0800, jim beam

<[email hidden]> wrote:

[snip]

Quoted message said:

2. that the stress/strain graph quoted for deformation theory is for a
different material to that from spokes are actually made - as shown in
different subsequent actual tensile samples graphs?

[snip]

Dear Jim,

For the benefit of puzzled readers . . .

In Jobst's book "The Bicycle Wheel," there's a stress-strain graph
showing a yield step or notch, meaning a section in the upward curve
where things behave oddly:

^ x
| x
stress- x
tension x
x
x x
x x x
x
strain-elongation -->

But no such notch appears on the stress-strain graphs of various
spokes being pulled apart in the back of the book in any edition (the
first edition includes carbon spokes, as well as modern stainless
steel spokes).

Unless jim has zero knowledge of metallurgy (which I doubt) he's doing
his usual: raising red herrings and false representations in a
compulsive attempt to look smarter than Jobst.

Jobst's stress-strain curve on p.32 - the one with the notch - is not
presented as representing any particular alloy. In fact, it's a
standard "first introduction" curve, used to explain the concepts to a
beginner, and it contains that yield notch because the notch is a
feature of mild steel, which is the most common metal used in
manufacturing. For web examples, see http://en.wikipedia.org/wiki/Stress-strain_curve
or http://tinyurl.com/2qhxut
or http://tinyurl.com/35th8a

which is what i said.

Quoted message said:

In almost any engineering book on material properties, that curve is
printed in the first couple chapters, and almost every author chooses
to show the notch just as Jobst has done. But again, the curve is
printed as a general example and introduction to concepts - exactly
what Jobst has done.

it's also misleading because it's evidence of complexity in deformation
mechanism which is typically not subsequently explained to engineers and
without which, they can't be expected to understand or apply proper
principles to other systems.

Quoted message said:

If it matters, the author might point out that
(most) other metals don't have the notch. My guess is that Jobst
didn't mention it because it has no importance in bicycle wheels.

except that stainless steels used in spokes don't have it.

Quoted message said:

In the back of _The Bicycle Wheel_ Jobst gives specific curves for
spoke alloys. Those curves are not intended to be general, but
specific to those test results. Those metals don't display the notch,
so of course the notch is not shown. His curves appear to be
accurate.

which again illustrates my point - regurgitation of text book and not
understanding the the mechanisms that differentiate.

Quoted message said:

I'm not surprised that Carl doesn't know this. It's the kind of thing
one learns in metallurgy and/or engineering classes, not English
classes.

carl has bothered to ask questions both on group in in private
correspondence. and is interested to know more. shame you don't.

Quoted message said:

But jim beam obviously should know this. As usual, his portrayal of
this as a mistake on Jobst's part is dishonest and cowardly.

if you knew your business, you wouldn't be reduced to such statements.

Quoted message said:

Quoted message said:

On Fri, 16 Feb 2007 18:22:07 -0800, jim beam

<[email hidden]> wrote:

[snip]

Quoted message said:

2. that the stress/strain graph quoted for deformation theory is for a
different material to that from spokes are actually made - as shown in
different subsequent actual tensile samples graphs?

[snip]

Dear Jim,

For the benefit of puzzled readers . . .

In Jobst's book "The Bicycle Wheel," there's a stress-strain graph
showing a yield step or notch, meaning a section in the upward curve
where things behave oddly:

^ x
| x
stress- x
tension x
x
x x
x x x
x
strain-elongation -->

But no such notch appears on the stress-strain graphs of various
spokes being pulled apart in the back of the book in any edition (the
first edition includes carbon spokes, as well as modern stainless
steel spokes).

Unless jim has zero knowledge of metallurgy (which I doubt) he's doing
his usual: raising red herrings and false representations in a
compulsive attempt to look smarter than Jobst.

Jobst's stress-strain curve on p.32 - the one with the notch - is not
presented as representing any particular alloy. In fact, it's a
standard "first introduction" curve, used to explain the concepts to a
beginner, and it contains that yield notch because the notch is a
feature of mild steel, which is the most common metal used in
manufacturing. For web examples, see http://en.wikipedia.org/wiki/Stress-strain_curve
or http://tinyurl.com/2qhxut
or http://tinyurl.com/35th8a

In almost any engineering book on material properties, that curve is
printed in the first couple chapters, and almost every author chooses
to show the notch just as Jobst has done. But again, the curve is
printed as a general example and introduction to concepts - exactly
what Jobst has done. If it matters, the author might point out that
(most) other metals don't have the notch. My guess is that Jobst
didn't mention it because it has no importance in bicycle wheels.

In the back of _The Bicycle Wheel_ Jobst gives specific curves for
spoke alloys. Those curves are not intended to be general, but
specific to those test results. Those metals don't display the notch,
so of course the notch is not shown. His curves appear to be
accurate.

I'm not surprised that Carl doesn't know this. It's the kind of thing
one learns in metallurgy and/or engineering classes, not English
classes.

But jim beam obviously should know this. As usual, his portrayal of
this as a mistake on Jobst's part is dishonest and cowardly.

- Frank Krygowski

Dear Frank,

"Those alloys don't display the notch, so of course the notch is not
shown."

In other words, the stainless steel spokes tested in the appendix
don't match the generalized example for a different material?

If so, the generalized example hardly illustrates what's happening
with the stainless steel spokes, which is what it's supposed to be
doing.

I'm surprised that you're not following what seems to be an obvious
problem in the text, so forgive me for repeating it--a yield-notch
graph is apparently intended to illustrate the behavior of stainless
steel spokes that don't apparently exhibit such behavior.

As for the accuracy of the curves from the actual testing, I assume
that they're reasonably accurate, but probably not terribly detailed.

After all, the carbon-steel spokes tested and graphed in the first
edition show no signs of any yield notch, which would be expected.

The tests, as far as I know, were intended primarily to show how
strong various spokes were--that is, the 2 mm straight spokes all fail
at about the load, regardless of how far they stretch before doing so,

Cheers,

Carl Fogel

Quoted message said:

Quoted message said:

Quoted message said:

On Fri, 16 Feb 2007 18:22:07 -0800, jim beam

<[email hidden]> wrote:

[snip]

> 2. that the stress/strain graph quoted for deformation theory is for a
> different material to that from spokes are actually made - as shown in
> different subsequent actual tensile samples graphs?
[snip]

Dear Jim,

For the benefit of puzzled readers . . .

In Jobst's book "The Bicycle Wheel," there's a stress-strain graph
showing a yield step or notch, meaning a section in the upward curve
where things behave oddly:

^ x
| x
stress- x
tension x
x
x x
x x x
x
strain-elongation -->

But no such notch appears on the stress-strain graphs of various
spokes being pulled apart in the back of the book in any edition (the
first edition includes carbon spokes, as well as modern stainless
steel spokes).

Unless jim has zero knowledge of metallurgy (which I doubt) he's doing
his usual: raising red herrings and false representations in a
compulsive attempt to look smarter than Jobst.

Jobst's stress-strain curve on p.32 - the one with the notch - is not
presented as representing any particular alloy. In fact, it's a
standard "first introduction" curve, used to explain the concepts to a
beginner, and it contains that yield notch because the notch is a
feature of mild steel, which is the most common metal used in
manufacturing. For web examples, see http://en.wikipedia.org/wiki/Stress-strain_curve
or http://tinyurl.com/2qhxut
or http://tinyurl.com/35th8a

In almost any engineering book on material properties, that curve is
printed in the first couple chapters, and almost every author chooses
to show the notch just as Jobst has done. But again, the curve is
printed as a general example and introduction to concepts - exactly
what Jobst has done. If it matters, the author might point out that
(most) other metals don't have the notch. My guess is that Jobst
didn't mention it because it has no importance in bicycle wheels.

In the back of _The Bicycle Wheel_ Jobst gives specific curves for
spoke alloys. Those curves are not intended to be general, but
specific to those test results. Those metals don't display the notch,
so of course the notch is not shown. His curves appear to be
accurate.

I'm not surprised that Carl doesn't know this. It's the kind of thing
one learns in metallurgy and/or engineering classes, not English
classes.

But jim beam obviously should know this. As usual, his portrayal of
this as a mistake on Jobst's part is dishonest and cowardly.

- Frank Krygowski

Dear Frank,

"Those alloys don't display the notch, so of course the notch is not
shown."

In other words, the stainless steel spokes tested in the appendix
don't match the generalized example for a different material?

If so, the generalized example hardly illustrates what's happening
with the stainless steel spokes, which is what it's supposed to be
doing.

I'm surprised that you're not following what seems to be an obvious
problem in the text, so forgive me for repeating it--a yield-notch
graph is apparently intended to illustrate the behavior of stainless
steel spokes that don't apparently exhibit such behavior.

As for the accuracy of the curves from the actual testing, I assume
that they're reasonably accurate, but probably not terribly detailed.

After all, the carbon-steel spokes tested and graphed in the first
edition show no signs of any yield notch, which would be expected.

no, they're highly worked higher carbon steel, not mild steel. such
steels don't have an endurance limit either.

Quoted message said:

The tests, as far as I know, were intended primarily to show how
strong various spokes were--that is, the 2 mm straight spokes all fail
at about the load, regardless of how far they stretch before doing so,

Cheers,

Carl Fogel

Quoted message said:

Quoted message said:

Quoted message said:

<[email hidden]> wrote:
[snip]

Quoted message said:

Quoted message said:

Quoted message said:

jim beam wrote
> 2. that the stress/strain graph quoted for deformation theory is for a
> different material to that from spokes are actually made - as shown in
> different subsequent actual tensile samples graphs?
[snip]

Quoted message said:

Quoted message said:

Quoted message said:

For the benefit of puzzled readers . . .
In Jobst's book "The Bicycle Wheel," there's a stress-strain graph
showing a yield step or notch, meaning a section in the upward curve
where things behave oddly:
^ x
| x
stress- x
tension x
x
x x
x x x
x
strain-elongation -->
But no such notch appears on the stress-strain graphs of various
spokes being pulled apart in the back of the book in any edition (the
first edition includes carbon spokes, as well as modern stainless
steel spokes).

Quoted message said:

Quoted message said:

Unless jim has zero knowledge of metallurgy (which I doubt) he's doing
his usual: raising red herrings and false representations in a
compulsive attempt to look smarter than Jobst.
Jobst's stress-strain curve on p.32 - the one with the notch - is not
presented as representing any particular alloy. In fact, it's a
standard "first introduction" curve, used to explain the concepts to a
beginner, and it contains that yield notch because the notch is a
feature of mild steel, which is the most common metal used in
manufacturing. For web examples, see http://en.wikipedia.org/wiki/Stress-strain_curve
or http://tinyurl.com/2qhxut
or http://tinyurl.com/35th8a

In almost any engineering book on material properties, that curve is
printed in the first couple chapters, and almost every author chooses
to show the notch just as Jobst has done. But again, the curve is
printed as a general example and introduction to concepts - exactly
what Jobst has done. If it matters, the author might point out that
(most) other metals don't have the notch. My guess is that Jobst
didn't mention it because it has no importance in bicycle wheels.

In the back of _The Bicycle Wheel_ Jobst gives specific curves for
spoke alloys. Those curves are not intended to be general, but
specific to those test results. Those metals don't display the notch,
so of course the notch is not shown. His curves appear to be
accurate.

I'm not surprised that Carl doesn't know this. It's the kind of thing
one learns in metallurgy and/or engineering classes, not English
classes.

But jim beam obviously should know this. As usual, his portrayal of
this as a mistake on Jobst's part is dishonest and cowardly.

Quoted message said:

"Those alloys don't display the notch, so of course the notch is not
shown."

In other words, the stainless steel spokes tested in the appendix
don't match the generalized example for a different material?

If so, the generalized example hardly illustrates what's happening
with the stainless steel spokes, which is what it's supposed to be
doing.

I'm surprised that you're not following what seems to be an obvious
problem in the text, so forgive me for repeating it--a yield-notch
graph is apparently intended to illustrate the behavior of stainless
steel spokes that don't apparently exhibit such behavior.

As for the accuracy of the curves from the actual testing, I assume
that they're reasonably accurate, but probably not terribly detailed.

After all, the carbon-steel spokes tested and graphed in the first
edition show no signs of any yield notch, which would be expected.

-snip-

Huh? Why would you expect a high carbon steel to behave like mild steel?

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

jim beam said:

Quoted message said:

Quoted message said:

On Feb 16, 9:39 pm, [email hidden] wrote:
> On Fri, 16 Feb 2007 18:22:07 -0800, jim beam
>
> <[email hidden]> wrote:
>
> [snip]
>
>> 2. that the stress/strain graph quoted for deformation theory is for a
>> different material to that from spokes are actually made - as shown in
>> different subsequent actual tensile samples graphs?
> [snip]
>
> Dear Jim,
>
> For the benefit of puzzled readers . . .
>
> In Jobst's book "The Bicycle Wheel," there's a stress-strain graph
> showing a yield step or notch, meaning a section in the upward curve
> where things behave oddly:
>
> ^ x
> | x
> stress- x
> tension x
> x
> x x
> x x x
> x
> strain-elongation -->
>
> But no such notch appears on the stress-strain graphs of various
> spokes being pulled apart in the back of the book in any edition (the
> first edition includes carbon spokes, as well as modern stainless
> steel spokes).
Unless jim has zero knowledge of metallurgy (which I doubt) he's doing
his usual: raising red herrings and false representations in a
compulsive attempt to look smarter than Jobst.

Jobst's stress-strain curve on p.32 - the one with the notch - is not
presented as representing any particular alloy. In fact, it's a
standard "first introduction" curve, used to explain the concepts to a
beginner, and it contains that yield notch because the notch is a
feature of mild steel, which is the most common metal used in
manufacturing. For web examples, see http://en.wikipedia.org/wiki/Stress-strain_curve
or http://tinyurl.com/2qhxut
or http://tinyurl.com/35th8a

In almost any engineering book on material properties, that curve is
printed in the first couple chapters, and almost every author chooses
to show the notch just as Jobst has done. But again, the curve is
printed as a general example and introduction to concepts - exactly
what Jobst has done. If it matters, the author might point out that
(most) other metals don't have the notch. My guess is that Jobst
didn't mention it because it has no importance in bicycle wheels.

In the back of _The Bicycle Wheel_ Jobst gives specific curves for
spoke alloys. Those curves are not intended to be general, but
specific to those test results. Those metals don't display the notch,
so of course the notch is not shown. His curves appear to be
accurate.

I'm not surprised that Carl doesn't know this. It's the kind of thing
one learns in metallurgy and/or engineering classes, not English
classes.

But jim beam obviously should know this. As usual, his portrayal of
this as a mistake on Jobst's part is dishonest and cowardly.

- Frank Krygowski

Dear Frank,

"Those alloys don't display the notch, so of course the notch is not
shown."

In other words, the stainless steel spokes tested in the appendix
don't match the generalized example for a different material?

If so, the generalized example hardly illustrates what's happening
with the stainless steel spokes, which is what it's supposed to be
doing.

I'm surprised that you're not following what seems to be an obvious
problem in the text, so forgive me for repeating it--a yield-notch
graph is apparently intended to illustrate the behavior of stainless
steel spokes that don't apparently exhibit such behavior.

As for the accuracy of the curves from the actual testing, I assume
that they're reasonably accurate, but probably not terribly detailed.

After all, the carbon-steel spokes tested and graphed in the first
edition show no signs of any yield notch, which would be expected.

no, they're highly worked higher carbon steel, not mild steel. such
steels don't have an endurance limit either.

Quoted message said:

The tests, as far as I know, were intended primarily to show how
strong various spokes were--that is, the 2 mm straight spokes all fail
at about the load, regardless of how far they stretch before doing so,

Cheers,

Carl Fogel

Dear Jim,

Oops! It sounds as if I've misunderstood you, as well as what I was
looking at.

Let's check if I'm following things now.

The idealized example in Jobst's book shows a large yield notch or
step.

Neither the stainless steel nor the carbon spoke test stress-strain
graphs in the strength-test appendix show such a notch.

I mistakenly assumed that the notch would appear in any carbon steel,
so I mistakenly figured that its absence in the graphs for the carbon
steel spokes in the 1st edition was due to the testing resolution not
being fine enough to show it.

Now you're correcting my mistake and saying that the yield notch is
found in low or mild steel (or unworked, undrawn steel), but that it
didn't appear in the carbon steel spoke graphs because it simply isn't
there--the spoke carbon steel is different and doesn't have the notch
behavior, either due to the higher carbon content or the work
hardening or both.

Is that the idea?

Cheers,

Carl Fogel

Quoted message said:

jim beam said:

Quoted message said:

On 16 Feb 2007 19:50:19 -0800, [email hidden] wrote:

> On Feb 16, 9:39 pm, [email hidden] wrote:
>> On Fri, 16 Feb 2007 18:22:07 -0800, jim beam
>>
>> <[email hidden]> wrote:
>>
>> [snip]
>>
>>> 2. that the stress/strain graph quoted for deformation theory is for a
>>> different material to that from spokes are actually made - as shown in
>>> different subsequent actual tensile samples graphs?
>> [snip]
>>
>> Dear Jim,
>>
>> For the benefit of puzzled readers . . .
>>
>> In Jobst's book "The Bicycle Wheel," there's a stress-strain graph
>> showing a yield step or notch, meaning a section in the upward curve
>> where things behave oddly:
>>
>> ^ x
>> | x
>> stress- x
>> tension x
>> x
>> x x
>> x x x
>> x
>> strain-elongation -->
>>
>> But no such notch appears on the stress-strain graphs of various
>> spokes being pulled apart in the back of the book in any edition (the
>> first edition includes carbon spokes, as well as modern stainless
>> steel spokes).
> Unless jim has zero knowledge of metallurgy (which I doubt) he's doing
> his usual: raising red herrings and false representations in a
> compulsive attempt to look smarter than Jobst.
>
> Jobst's stress-strain curve on p.32 - the one with the notch - is not
> presented as representing any particular alloy. In fact, it's a
> standard "first introduction" curve, used to explain the concepts to a
> beginner, and it contains that yield notch because the notch is a
> feature of mild steel, which is the most common metal used in
> manufacturing. For web examples, see http://en.wikipedia.org/wiki/Stress-strain_curve
> or http://tinyurl.com/2qhxut
> or http://tinyurl.com/35th8a
>
> In almost any engineering book on material properties, that curve is
> printed in the first couple chapters, and almost every author chooses
> to show the notch just as Jobst has done. But again, the curve is
> printed as a general example and introduction to concepts - exactly
> what Jobst has done. If it matters, the author might point out that
> (most) other metals don't have the notch. My guess is that Jobst
> didn't mention it because it has no importance in bicycle wheels.
>
> In the back of _The Bicycle Wheel_ Jobst gives specific curves for
> spoke alloys. Those curves are not intended to be general, but
> specific to those test results. Those metals don't display the notch,
> so of course the notch is not shown. His curves appear to be
> accurate.
>
> I'm not surprised that Carl doesn't know this. It's the kind of thing
> one learns in metallurgy and/or engineering classes, not English
> classes.
>
> But jim beam obviously should know this. As usual, his portrayal of
> this as a mistake on Jobst's part is dishonest and cowardly.
>
> - Frank Krygowski
Dear Frank,

"Those alloys don't display the notch, so of course the notch is not
shown."

In other words, the stainless steel spokes tested in the appendix
don't match the generalized example for a different material?

If so, the generalized example hardly illustrates what's happening
with the stainless steel spokes, which is what it's supposed to be
doing.

I'm surprised that you're not following what seems to be an obvious
problem in the text, so forgive me for repeating it--a yield-notch
graph is apparently intended to illustrate the behavior of stainless
steel spokes that don't apparently exhibit such behavior.

As for the accuracy of the curves from the actual testing, I assume
that they're reasonably accurate, but probably not terribly detailed.

After all, the carbon-steel spokes tested and graphed in the first
edition show no signs of any yield notch, which would be expected.

no, they're highly worked higher carbon steel, not mild steel. such
steels don't have an endurance limit either.

Quoted message said:

The tests, as far as I know, were intended primarily to show how
strong various spokes were--that is, the 2 mm straight spokes all fail
at about the load, regardless of how far they stretch before doing so,

Cheers,

Carl Fogel

Dear Jim,

Oops! It sounds as if I've misunderstood you, as well as what I was
looking at.

Let's check if I'm following things now.

The idealized example in Jobst's book shows a large yield notch or
step.

Neither the stainless steel nor the carbon spoke test stress-strain
graphs in the strength-test appendix show such a notch.

I mistakenly assumed that the notch would appear in any carbon steel,
so I mistakenly figured that its absence in the graphs for the carbon
steel spokes in the 1st edition was due to the testing resolution not
being fine enough to show it.

Now you're correcting my mistake and saying that the yield notch is
found in low or mild steel (or unworked, undrawn steel), but that it
didn't appear in the carbon steel spoke graphs because it simply isn't
there--the spoke carbon steel is different and doesn't have the notch
behavior, either due to the higher carbon content or the work
hardening or both.

Is that the idea?

yup!

Quoted message said:

Cheers,

Carl Fogel