disk brake debate - summary II

1. in the absence of an iso pullout figure, [and conveniently ignoring
lawyer lips] there is no argument against disk brake ejection because
there is no pullout figure that the ejection force can easily be shown
to exceed.

2. according to the naysayers, pullout force is apparently /not/ a
function of qr clamping force in conjunction with mechanical interlock
caused by indentation. because by conveniently not acknowledging the
effect of clamping force and interlock, they have no argument. [see
point 1. above.]

3. if pullout force /were/ to be a function of mechanical interlock, no
one has yet shown any willingness to analyze existing estimates of the
material shear force that breaking that interlock would create.

4. yawn.

jim beam wrote:
1. in the absence of an iso pullout figure, [and conveniently ignoring
lawyer lips] there is no argument against disk brake ejection because
there is no pullout figure that the ejection force can easily be shown
to exceed.

2. according to the naysayers, pullout force is apparently /not/ a
function of qr clamping force in conjunction with mechanical interlock
caused by indentation. because by conveniently not acknowledging the
effect of clamping force and interlock, they have no argument. [see
point 1. above.]

3. if pullout force /were/ to be a function of mechanical interlock, no
one has yet shown any willingness to analyze existing estimates of the
material shear force that breaking that interlock would create.

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.

Nobody has addressed the reaction forces in the plane parallel to the
ground - the ones that tend to twist the fork legs. They obviously
exist, yet are completely ignored by the "engineers" here.

I got involved in this because of the research I was doing before
installing disks on both my mountain bikes. I read everything I could
lay my eyes on, and these threads came up in the course of my searches.
After all the reading I've done, I've decided that James and Jobst are
playing Chicken Little, and that my regular QR fork with new XT QRs
(which come with new XT disk hubs) are perfectly acceptable, and will
not eject my wheels with disk brakes in any sort of situation in which
I MTB, including road slicks on dry pavement during the muddy-trail
season. I suspect both James and Jobst have expert witness money
riding on their comments, which is why neither of them will admit to
any portion of the hypothesis as being questionable, let alone wrong.
I have yet to see James admit that anyone else might even have a point,
let alone a good point. There *must* be money involved - no one is
that arrogant.

4. yawn.

Dude, we were at "yawn" 400 posts ago. Nothing new here, move
along...

E.P.

P.S. My suggestion is to link to the summary thread during any further
discussion of this issue. None of the previous ones have gone as far
in knocking down James' hypothesis.

On 18 Oct 2005 21:50:17 -0700, "
wrote:


jim beam wrote:
1. in the absence of an iso pullout figure, [and conveniently ignoring
lawyer lips] there is no argument against disk brake ejection because
there is no pullout figure that the ejection force can easily be shown
to exceed.

2. according to the naysayers, pullout force is apparently /not/ a
function of qr clamping force in conjunction with mechanical interlock
caused by indentation. because by conveniently not acknowledging the
effect of clamping force and interlock, they have no argument. [see
point 1. above.]

3. if pullout force /were/ to be a function of mechanical interlock, no
one has yet shown any willingness to analyze existing estimates of the
material shear force that breaking that interlock would create.

An interesting spin on the available data. Your 20kN force has been
totally blown away.

But he put "summary" in the subject of this thread, so doesn't that
mean he's pulling together the best available knowledge?

JT

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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
one...

James

wrote:
jim beam wrote:

1. in the absence of an iso pullout figure, [and conveniently ignoring
lawyer lips] there is no argument against disk brake ejection because
there is no pullout figure that the ejection force can easily be shown
to exceed.

2. according to the naysayers, pullout force is apparently /not/ a
function of qr clamping force in conjunction with mechanical interlock
caused by indentation. because by conveniently not acknowledging the
effect of clamping force and interlock, they have no argument. [see
point 1. above.]

3. if pullout force /were/ to be a function of mechanical interlock, no
one has yet shown any willingness to analyze existing estimates of the
material shear force that breaking that interlock would create.


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. joe riel's number is much more
precisely calculated. the point is that no one was addressing the
degree of clamping force, just waving their hands. now we have a usable
number and are removing the void of uncertainty into which smoke can be
blown.


Nobody has addressed the reaction forces in the plane parallel to the
ground - the ones that tend to twist the fork legs. They obviously
exist, yet are completely ignored by the "engineers" here.

I got involved in this because of the research I was doing before
installing disks on both my mountain bikes. I read everything I could
lay my eyes on, and these threads came up in the course of my searches.
After all the reading I've done, I've decided that James and Jobst are
playing Chicken Little, and that my regular QR fork with new XT QRs
(which come with new XT disk hubs) are perfectly acceptable, and will
not eject my wheels with disk brakes in any sort of situation in which
I MTB, including road slicks on dry pavement during the muddy-trail
season. I suspect both James and Jobst have expert witness money
riding on their comments, which is why neither of them will admit to
any portion of the hypothesis as being questionable, let alone wrong.
I have yet to see James admit that anyone else might even have a point,
let alone a good point. There *must* be money involved - no one is
that arrogant.


4. yawn.


Dude, we were at "yawn" 400 posts ago. Nothing new here, move
along...

E.P.

P.S. My suggestion is to link to the summary thread during any further
discussion of this issue. None of the previous ones have gone as far
in knocking down James' hypothesis.

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
one...

James


that's another example of the logical disconnect that allows you to
claim that indented fork ends don't affect pullout force. james, your
theory is incomplete. you don't address pullout force; and without
that, your ejection force means nothing. all while we're ignoring the
elephant in the room, the presence of lawyer lips. you need to get with
the math. "move on" indeed.

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

jim beam wrote:
that's another example of the logical disconnect that allows you to
claim that indented fork ends don't affect pullout force.

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: .

--
Dave
dvt at psu dot edu

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.

--
Dave
dvt at psu dot edu

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?

those figures are for smooth surfaces, not what we have here.