disk brake debate - summary II

James Annan wrote:
jim beam wrote:

wrote:

An interesting spin on the available data. Your 20kN force has been
totally blown away. Wouldn't it be best to admit you were mistaken
there? Jobst has a point about fretting over time for indentation
reinforcement.


i'm delighted that number's "blown away"! i said from the beginning
that my figure was a guesstimate.

You said "a rough calc shows the clamping force for a normal skewer is
~20kN", which has been shown to be out by a factor of about 3 from a
plausible upper limit and more like an order of magnitude according to
actual measurements.

No doubt you'll be "delighted" once you work out that the rest of your
argument is similarly wrong.

Actually, it isn't.

But if it helps you to make a buck or three to think otherwise, great.

E.P.

41 wrote:

James Annan wrote:

41 wrote:


James Annan wrote:


jim beam wrote:

yet more self-flagellation. Stop humiliating yourself and move on,
can't you? If you pulled your head out of your arse for once you might
be able to make a useful contribution, or at least an interesting
on e...


But that would require far more than 20kN, which Mr "Metallurgy School"
Jim Beam admits he cannot generate. You see, you have neglected to
account for the mechanical interlock that has resulted from so much
fretting.

Even if such forces were made available to shear the damn thing out,
your assessment of the results is wildly overoptimistic. L


chuckle.

Thanks for that, I can't honestly say it made 700 posts worth reading,
but it paid back something anyway!


It's my pleasure.


A conveniently apropos picture which just popped up in another ng:

http://www.edconrad.com/ebay/SimplyMagic/sunshine.jpg

I daresay you could be right, it looks like a tight interlock. jim might
not hear UNLESS WE SHOUT!

James
--
James Annan
see web pages for email
http://www.ne.jp/asahi/julesandjames/home/
http://julesandjames.blogspot.com/

"dvt" wrote in message
...
jim beam wrote:
dvt wrote:

dvt wrote:

The data in another thread shows evidence that indented/embossed
fork ends don't greatly affect pullout force. Here's the message ID
for that data in case you missed it: .



I just saw your note in the other thread. Use groups.google.com's
advanced search and plug in the message ID I gave above.

"Steel on steel static friction is in the range of .74 to .78 (dry).
Avallone, E.A. and Baumeister III, T. (1987). Marks' standard
handbook
for mechanical engineers (9th ed.). New York, NY: McGraw-Hill.

Phil H"

correct?

Nope. You have to plug the message ID specifically into the message ID
box on the advanced search page. Try this:

http://groups.google.com/group/rec.b...bb1680e2?hl=en

The article implies pullout force is equal to clamping force which
results in u = .25 for steel on steel. That is only 1/3 of the cited
value. As Jim pointed out, u = .74 - .78 is for smooth surfaces. One
would expect this figure to be higher with a serrated QR.

Phil H

James Annan wrote:
41 wrote:

James Annan wrote:

41 wrote:


James Annan wrote:


jim beam wrote:

yet more self-flagellation. Stop humiliating yourself and move on,
can't you? If you pulled your head out of your arse for once you might
be able to make a useful contribution, or at least an interesting
on e...


But that would require far more than 20kN, which Mr "Metallurgy School"
Jim Beam admits he cannot ge nerate. You see, you have neglected to
account for the mechanical interlock that has resulted from so much
fretting.

Even if such forces were made available to shear the damn thing out,
your assessment of the results is wildly ov eroptimistic. L


chuckle.

Thanks for that, I can't honestly say it made 700 posts worth reading,
but it paid back something anyway!


It's my pleasure.


A conveniently apropos picture which just popped up in another ng:

http://www.edconrad.com/ebay/SimplyMagic/sunshine.jpg

I daresay you could be right, it looks like a tight interlock. jim might
not hear UNLESS WE SHOUT!

HOLY CRAP! So we know where his monitor is, and the mouse too I
suppose, but I'm wondering: where does he keep the keyboard?

But no doubt, like everything else, he somehow faked the picture.e

James Annan wrote:
jim beam wrote:

wrote:

An interesting spin on the available data. Your 20kN force has been
totally blown away. Wouldn't it be best to admit you were mistaken
there? Jobst has a point about fretting over time for indentation
reinforcement.



i'm delighted that number's "blown away"! i said from the beginning
that my figure was a guesstimate.


You said "a rough calc shows the clamping force for a normal skewer is
~20kN", which has been shown to be out by a factor of about 3 from a
plausible upper limit and more like an order of magnitude according to
actual measurements.

No doubt you'll be "delighted" once you work out that the rest of your
argument is similarly wrong.

James

by what factor is your ejection force exceeded by pullout force? oh,
wait, you've not done any analysis. my bad.

"41" wrote in message
oups.com...

James Annan wrote:
41 wrote:

James Annan wrote:

41 wrote:


James Annan wrote:


jim beam wrote:

yet more self-flagellation. Stop humiliating yourself and move
on,
can't you? If you pulled your head out of your arse for once you
might
be able to make a useful contribution, or at least an interesting
on e...


But that would require far more than 20kN, which Mr "Metallurgy
School"
Jim Beam admits he cannot ge nerate. You see, you have neglected
to
account for the mechanical interlock that has resulted from so
much
fretting.

Even if such forces were made available to shear the damn thing
out,
your assessment of the results is wildly ov eroptimistic. L


chuckle.

Thanks for that, I can't honestly say it made 700 posts worth
reading,
but it paid back something anyway!


It's my pleasure.


A conveniently apropos picture which just popped up in another ng:

http://www.edconrad.com/ebay/SimplyMagic/sunshine.jpg

I daresay you could be right, it looks like a tight interlock. jim
might
not hear UNLESS WE SHOUT!

HOLY CRAP! So we know where his monitor is, and the mouse too I
suppose, but I'm wondering: where does he keep the keyboard?

But no doubt, like everything else, he somehow faked the picture.e

Why does he need to fake it when its not very difficult to produce? With
a 6061-T6 bearing allowable of around 300 MPa, those indentations would
require a clamp-up force of 4kN for an indentation area of 15mm^2 (22
indentations of 2 x .35). An unremarkable result well within the realm
of possibility.

Phil H

Phil Holman wrote:
"41" wrote in message
oups.com...

James Annan wrote:
41 wrote:

James Annan wrote:

41 wrote:


James Annan wrote:


jim beam wrote:

yet more self-flagellation. Stop humiliating yourself and move
on,
can't you? If you pulled your head out of your arse for once you
might
be able to make a useful contribution, or at least an interesting
on e...


But that would require far more than 20kN, which Mr "Metallurgy
School"
Jim Beam admits he cannot ge nerate. You see, you have neglected
to
account for the mechanical interlock that has resulted from so
much
fretting.

Even if such forces were made available to shear the damn thing
out,
your assessment of the results is wildly ov eroptimistic. L


chuckle.

Thanks for that, I can't honestly say it made 700 posts worth
reading,
but it paid back something anyway!


It's my pleasure.


A conveniently apropos picture which just popped up in another ng:

http://www.edconrad.com/ebay/SimplyMagic/sunshine.jpg

I daresay you could be right, it looks like a tight interlock. jim
might
not hear UNLESS WE SHOUT!

HOLY CRAP! So we know where his monitor is, and the mouse too I
suppose, but I'm wondering: where does he keep the keyboard?

But no doubt, like everything else, he somehow faked the picture.e

Why does he need to fake it when its not very difficult to produce? With
a 6061-T6 bearing allowable of around 300 MPa, those indentations would
require a clamp-up force of 4kN for an indentation area of 15mm^2 (22
indentations of 2 x .35). An unremarkable result well within the rea lm
of possibility.

Oh, puh-lease, no serious posts in this thread! But if you read the
exchanges on this topic, I think you'll find what's wrong with your
argument, explicitly. But please, post anything serious elsewhere.
Like, why not where the discussion actually occurred, in response to
the actual posts that discussed the matter? At the same time you could
read them, which would save repetition.

And by the way, those dropouts shown were chrome-plated steel, not
aluminum. The aluminum ones he showed before that had no indentations
at all, only a little burnishing.

"41" wrote in message
oups.com...

Phil Holman wrote:
"41" wrote in message
oups.com...

James Annan wrote:
41 wrote:

James Annan wrote:

41 wrote:


James Annan wrote:


jim beam wrote:

yet more self-flagellation. Stop humiliating yourself and move
on,
can't you? If you pulled your head out of your arse for once
you
might
be able to make a useful contribution, or at least an
interesting
on e...


But that would require far more than 20kN, which Mr "Metallurgy
School"
Jim Beam admits he cannot ge nerate. You see, you have
neglected
to
account for the mechanical interlock that has resulted from so
much
fretting.

Even if such forces were made available to shear the damn thing
out,
your assessment of the results is wildly ov eroptimistic. L


chuckle.

Thanks for that, I can't honestly say it made 700 posts worth
reading,
but it paid back something anyway!


It's my pleasure.


A conveniently apropos picture which just popped up in another ng:

http://www.edconrad.com/ebay/SimplyMagic/sunshine.jpg

I daresay you could be right, it looks like a tight interlock. jim
might
not hear UNLESS WE SHOUT!

HOLY CRAP! So we know where his monitor is, and the mouse too I
suppose, but I'm wondering: where does he keep the keyboard?

But no doubt, like everything else, he somehow faked the picture.e

Why does he need to fake it when its not very difficult to produce?
With
a 6061-T6 bearing allowable of around 300 MPa, those indentations
would
require a clamp-up force of 4kN for an indentation area of 15mm^2 (22
indentations of 2 x .35). An unremarkable result well within the rea
lm
of possibility.

Oh, puh-lease, no serious posts in this thread! But if you read the
exchanges on this topic, I think you'll find what's wrong with your
argument, explicitly. But please, post anything serious elsewhere.
Like, why not where the discussion actually occurred, in response to
the actual posts that discussed the matter? At the same time you could
read them, which would save repetition.

41 wrote.....
"Like everything else, he somehow faked the picture"

Sorry, I took "everything else" to mean, well, everything else.


And by the way, those dropouts shown were chrome-plated steel, not
aluminum. The aluminum ones he showed before that had no indentations
at all, only a little burnishing.


http://home.comcast.net/~carlfogel/d.../indented.jpeg

Burnishing, please be serious.

http://home.comcast.net/~carlfogel/d...ki_indent.jpeg

What do you think, are the dropouts decorative chrome or hard chrome?

Phil H

Phil Holman wrote:
please be serious.

Not in this thread.

Anyrate, you have a bicycle, you have a quick release, the dropouts
have indentations: why not install the QR with serrations out of phase
with the old ones, and see if you get a new set with one normal
clamping operation, no riding? Good luck!!

Phil Holman wrote:
The article implies pullout force is equal to clamping force which
results in u = .25 for steel on steel. That is only 1/3 of the cited
value. As Jim pointed out, u = .74 - .78 is for smooth surfaces. One
would expect this figure to be higher with a serrated QR.

Precisely the point. If the serrated QR was able to "dig in" the
dropouts, then the measured pullout force would be higher than predicted
by friction. But the measurements show that the pullout force is less
than or equal to that predicted by friction. Therefore if the QR is
digging in, it isn't adding much to the pullout force.

--
Dave
dvt at psu dot edu