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Topic: Poisson's ratio WAS: Re: Compak vs Macap vs Rocky (11 msgs / 207 lines)
1) From: Mike Koenig
Ray,
Please try not to abuse scientific phenomena.  Poisson's ratio has nothing
to do with systems of particles, and applies only to solid objects, (like
rubber or metal).
Tamping in one axis cannot correct for clumps - you will get less dense
areas in your puck.  Applying some lateral force (I think you say you let
the vibration of your grinder settle the puck) could take care of some
clumping (though I'm quite curious why your grinder vibrates that much,
doesn't seem right to me)...
--mike
On Sat, May 15, 2010 at 2:55 AM,  wrote:
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2) From: raymanowen
Then I don't know why the grounds would press out and seal against the sides
of the basket when you are only applying axial force with the tamper.
Hydrostatic?
I hope I don't owe a refund of all our pay at the Geophysics Research
Institute at CSM. Please don't tell Dr. Levent Ozdemir or Dr. Russ Miller we
were doing bad oil shale research. Damn!
What supports you when you walk on a sandy beach?
Teach me, please. -ro
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3) From: Kirk Janowiak
Sorry, Mike, but Poisson applies here with ground coffee as well. Way  
back when I was taking agronomy coursework at Purdue, we used Poisson  
ratios in looking into soil compaction issues. "System" or no, Poisson  
ratios are discussed in any number of arrangements aggregate from sand  
to concrete. Doesn't have to be a solid like metal.
Kirk
(Janomac)
On May 17, 2010, at 2:34 PM, Mike Koenig wrote:
<Snip>
JanoMac
janomac
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4) From: John A C Despres
Poisson's ratio is simply about contraction or expansion when something is
stretched or compacted. In my mind it will work in the case of solids or
loose particles.
John
On Tue, May 18, 2010 at 7:25 AM, Kirk Janowiak  wrote:
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5) From: Rich
Casual observation in the real physical world by a disinterested 
observer tells that it does.
John A C Despres wrote:
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6) From: Clay Spence
I think so, too, but it can be really complicated unless the deformation is
elastic, I think meaning that the object returns to its original shape when
you remove the force. Imagine stretching a bunch of loose particles (or
trying to) instead of compacting them. Poisson's ratio might be different
for the two cases. If you compact, the ratio probably depends on how much
you compact. And after you've compacted loose particles some, they usually
won't return to the original shape, and the ratio is probably different. All
that doesn't mean it can't be a useful idea for approximate reasoning.
Clay
On Tue, May 18, 2010 at 8:42 AM, Rich  wrote:
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7) From: Joseph Robertson
Teach me too.
Any science is more than I have under my higher education belt. One thing I
love about good coffee, it goes with any book and any discussion. Damn spell
check better work this time, ;^))
JoeR
On Tue, May 18, 2010 at 12:01 AM,  wrote:
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-- 
Ambassador for Specialty Coffee and palate reform.
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8) From: Mike Koenig
I'm probably splitting hairs here, but Poisson's effect happens on the
molecular level, with bonds elongating under pressure or strain.  I'm not a
geoscience guy, but I imagine the effect effect would happen in rocks, dense
clays and shale, etc,  but what you are seeing in a coffee puck is
interactions between discrete non-uniform particles.
I'm not arguing at all that you don't get some lateral expansion during
tamping, since that certainly does happen, but it's not necessarily uniform,
and dependent on the distribution (and re-arrangement under force) of the
particles, as opposed to poisson's effect, which describes a predictable
amount of lateral expansion based on the change axial length.  If the
expansion was due to poisson's effect, the puck would spring back when you
let go of the tamper.   What you are getting is some re-arrangement of the
particles under force (like when you step in sand, and it moves out of the
way under your foot).
--mike
On Tue, May 18, 2010 at 3:01 AM,  wrote:
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9) From: Joseph Robertson
Mike,
Nice to hear a human description of a "Natural" force of nature.  We being
part of nature. Although some would argue I'm not at all natural of this
earth like my mother who used to ( tongue in cheek I'm sure ) tell friends
when introducing me as a child that "Joe did not come by stork, there was
this small shiny ship that landed one night in our neighborhood." Could this
be why I love Sci fi and this black gold that runs through this list's
vein's? I did a wiki pedia and some other reading so I would have a clue
when you and RayO or anyone else shares information on this 'spro tamping
topic.
Very interesting and fun now back to my coffee.
JoeR
On Tue, May 18, 2010 at 7:34 AM, Mike Koenig  wrote:
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-- 
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10) From: Scott Miller
And I thought we were going to have a reprisal of Abe Vigoda's role on
Barney Miller...
cheers,
SfM
On Tue, May 18, 2010 at 4:36 PM, Ryan M. Ward
wrote:
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11) From: Doug Hoople
One word: bouillabaisse. :)
Doug
On Tue, May 18, 2010 at 9:30 AM, Tom & Maria - Sweet Maria's Coffee <
sweetmarias> wrote:
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