[Homeroast] Poisson's ratio WAS: Re: Compak vs Macap vs Rocky Grinders

Rich rich-mail at octoxol.com
Tue May 18 07:42:08 CDT 2010


Casual observation in the real physical world by a disinterested 
observer tells that it does.

John A C Despres wrote:
> 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 <janomac at gmail.com> wrote:
> 
>> 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:
>>
>>  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, <raymanowen at gmail.com> wrote:
>>>
>>>  The Major (Silver Fireplug; BUFF) burrs do wonderful things to coffee
>>>> beans
>>>> once again after 5 years' use, renewed a couple of months ago.  When I
>>>> first
>>>> got it, the maintenance tag said they'd been in use for 10 years- I
>>>> presume
>>>> at *$. There's a story in there somewhere.
>>>>
>>>> (Can they even access the burrs in their present push-button pop
>>>> machines-
>>>> and would they?) Employees in the SCAA, SCAB or SCAM union punch in, push
>>>> buttons, make change, punch out and cash their check. Seems like little
>>>> else
>>>> was interesting to the majority in Denver town when I was seeking a
>>>> reason
>>>> to enjoy espresso.
>>>>
>>>> Why seek to enjoy espresso? As I said before, I was associated with a
>>>> fellow
>>>> that won the bid on an equipment lot from the SS United States in dry
>>>> dock...
>>>>
>>>> "Hey, Ray- What do you know about this espresso machine?
>>>>
>>>> "Nuthin-' but I can count- it has 5 or 6 stations, and looks like it came
>>>> from a Tijuana Cat House, with all the black and red Naugahyde and gold
>>>> (polished Brass?) pieces...  Thus started my quest to find out how Real
>>>> Espresso should taste.
>>>>
>>>> Looks like SCAA might as well be SCCA, as much as they do for the
>>>> commercial
>>>> cup.  Almost made "Commercial" a four-letter word, instead of "Artisan"
>>>> the
>>>> bean deserves.
>>>>
>>>> In my opinion, the Grinder is Everything.  Any real coffee shop ought to
>>>> keep a stack of new burrs like the Cincinnati Kid had a stack of chips at
>>>> the table in Las Vegas.
>>>>
>>>> Who promotes the palaver about coffee clumps surviving the packing tamp?
>>>> Stand up and be counted. So coffee clumps have more structural integrity
>>>> than the buildings in San Francisco in 1906, Philippines 1968, or Haiti
>>>> more
>>>> recently. By comparison, the raw coffee clumps out of the new burrs in
>>>> the
>>>> Mazzer are demolished by the Richter 10.0 vibration and tamping force
>>>> that
>>>> resolves to a tri-axial force by Poisson's ratio.
>>>>
>>>> The compression due to the axial tamping force causes transverse forces
>>>> that
>>>> tend to seal the puck in the filter basket. Otherwise, the brewing water
>>>> would flow around the puck instead of through it, at reduced pressure and
>>>> extraction and little crema formation.
>>>>
>>>> Conversely, a wine bottle cork screw can extract the cork when it's
>>>> screwed
>>>> in less than half-way. Poisson again. Screw a wood screw into the cork,
>>>> and
>>>> you're never pulling it out intact. P.
>>>>
>>>> So the grinder makes clumps. They can't survive packing and tamping- I
>>>> have
>>>> some extra sharp Cheddar and Irish Dubliner that might go well with your
>>>> spur gear sound.
>>>>
>>>> Cheers, Mabuhay, Iechyd da -RayO, aka Opa!
>>>>
>>>> Got Grinder?
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>> JanoMac
>> janomac at gmail.com
>>
>>
>>
>>
>>
>>
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