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Date: 01 Mar 2007 10:11:08
From: gscace
Subject: Experiments in programmable, variable brew pressure profiling
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Hi:
I just finished building and installing a bolt-on, programmable
pressure profiling pump system to my uber-stable LM Frankenlinea. I
did this because I wanted to test prevailing ideas about preinfusion,
the benefits of lever machine pressure profiles, etc. on a very stable
platform on which selected brewing parameters may be quickly changed
while holding others constant to values which are the current state of
the art. At the same time, if the tests warranted, I wanted to make
the system transparent enough that I could put together similar
systems so that interested folks could just do a pump swap, with no
extra effort involved. Depending on how this all goes over the next
few weeks I may end up writing something more comprehensive, but for
now I'll give progress reports as I learn stuff.
Acknowledgements up front for folks who who ought to be recognized:
Andy Scheckter implemented brew pressure profiling over a year ago,
and should be credited as being a true pioneer on this. I'd like to
thank Michael Teahan for tipping me off to a source of the required
pump, and to Clyde Smith at Fluid-o-Tech, for his advice and
encouragement. I should also mention here that the path I'm treading
is not new. There is a body of work that has recently been performed
by machine manufacturers, but I am not privy to details.
As I said earlier, the idea here isn't necessarily to pioneer any
device, but to test the idea of pressure profiling in a reasonably
systematic way, look at any perceived benefit from pressure profiling,
publish the results in places where the results might have some
impact, and in the end maybe make it possible for others to tailor
brew parameter space for themselves if the results warrant.
Now, a little about the device: Unlike Andy's, the programmable
pressure-profiling system (PPPS) is built from an array of
commercially available parts. The pump is a rotary vane pump, which
is magnetically coupled to 3-phase magnetic drive. Power is supplied
to the pump drive by an accompanying 3-phase, variable-frequency
converter that operates the drive over the range from 1100 to
3500RPM. The RPM of the pump is varied in response to an output
signal provided by a fast-acting, industrial process controller. An
electronic pressure transducer mounted in the water delivery line to
the espresso machine provides a feedback signal to the process
controller. The pump / drive combination is really quite
interesting. Power consumption of the magnetic drive is 1/3 the power
required by a traditional AC motor / pump combination. The system
also has reliability advantages. Since the pump is magnetically
coupled to the drive, there is no shaft seal to wear out. The pump
plumbing is configured so that most of the water delivered by the pump
impeller is recirculated to the pump inlet. The amount of
recirculation is adjusted so that the pump runs at nearly maximum
speed when the output pressure is approximately 140 psi. This sets
the pressure range of the pump from almost no pressure at 1100 RPM to
140 psi at slightly less than 3500 RPM.
The test machinery: The test platform includes equipment considered
to be state-of-the-art within the coffee industry. The pump is
installed on a 2-group, LM FrankenLinea AV. Water supply to the pump
is from a 5-gal. plastic carboy, filled with carbon-filtered water
conditioned by an acid neutralizer and solar salt ion-exchange
softener. Unlike a stock Linea, the Linea used here has no exposed
plumbing. Flowmeters and group solenoids are mounted on top of the
group caps, with water passageways integrated into the cap design.
Temperature stability and reproducibility of this machine is better
than 1 degree F under all duty cycles. Temperature control is
achieved using a boiler mounted thermocouple, with industrial fuzzy-
logic process controller. The machine has 0.6mm gicleurs installed in
both groups. A Mazzer Robur is used for grinding the coffee. Coffee
is roasted in-house (literally, since that's where Espresso Research
Company HQ resides) on a Has Garanti drum roaster with 1 kg. capacity.
Progress: I've got the pump installed on the Linea and I've learned
how to control the pump. The coupled system of pump and espresso
machine produces an interesting control problem on startup. Cool
makeup water entering the boiler expands, raising the boiler pressure
to 12 bar. On pump startup, the brew solenoid opens, ejecting a small
amount of water. At the same time the pump activates, with speed
controlled by the process controller. The controller at first detects
falling pressure, and speeds the pump to compensate, resulting in a
pressure burp on startup. The problem is reasonably managed by
selecting the fuzzy logic control parameter in the controller, and
assigning an initial pressure setpoint of around 1.5 bar, rather than
my initial setting of zero. The controller now detects a falling
pressure, but the response is to allow the pressure to fall, ramping
quickly to 1.5 bar for 1 second, then initiating the programmed pre-
infusion cycle. There is no issue of pressure burping if the pump is
configured to mimic a normal AC-motor-driven pump. In this case, at
startup the pump speed rapidly increases to that which is required to
support 9 bars pressure as measured in the group.
I have loaded a program into the controller that mimics an e-61 pre-
infusion profile on startup, with straight-line (linear) increase in
pressure over an 8-second period to 9 bars of pressure. The pressure
profile remains constant at 9 bars for 5 seconds, then reduces
linearly to approximately 7 bars at pump cutoff. The pre-infusion
result is visually interesting to me in that liquid appears at the
same time over the entire surface of the brew basket (bottomless
portafilter), indicating that saturation of the cake is occurring more
or less completely. It's intuitively satisfying, at the least in that
the subsequent liquid flow buildup is uniform and very similar to what
I have observed from e-61 machines. The effect of the pre-infusion
ramp on required grind fineness is that my Robur needed to be set to
produce finer grind by several divisions of the knurled outer surface
of the adjusting collar. This is similar to what I experienced when
reducing gicleur diameters in the Linea during comparison tests
against a pre-production LM GS3 last winter ('05 - 06). I attribute
this to reduced "slamming" of hot water into the cake, reduction of
fines migration, or whatnot. Anyway it seemed reasonable to me based
on past experience.
The pressure tail-off is an arbitray exercise just because I could do
it, and because Andy Scheckter reports some benefit. It appears
possible to control the flow rate of the extraction by controlling
pressure tail-off, and by doing so somewhat delay the onset of
blonding. I don't know much more than that at this time. Paul Pratt
kindly sent me the pressure profile of his Faema lever machine, which
I will try when I get a little more orderly in my methods.
Essentially his machine starts at near zero pressure, builds very
quickly to 8.5 bars (piston release), and then reduces to 3 bars at
the end of the extraction. I'm presuming the pressure reduction is
linear since the piston is spring-driven.
Taste - Obviously this is the important, bottom-line issue.
Qualitative observation of extraction is only meaningful if it can be
correctly correlated to optimum taste. It's REALLY early to draw any
meaningful conclusions. But I didn't screw up by installing the pump
system. The coffee is at least as good as I was producing before, and
I was doing a pretty good job prior to the pump install. I've not yet
had time to alternate back and forth between straight 9 bar
extractions and profiled extractions, because my first efforts have
been in sorting out the system. I hope to do testing soon that will
be reasonably valid. I may bring another conical grinder home to pair
with the Robur so that I can one grinder correctly for profiled shots
and one for constant pressure shots. And I've got to find some test
victims - maybe local folk that can really hold their coffee.
More soon!
-Greg
This is gonna get cross-posted at HB and Coffeed. Both sites are not
necessarily visited by AC folk, and both sites have different target
audiences.
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Date: 02 Mar 2007 08:33:37
From: gscace
Subject: Re: Experiments in programmable, variable brew pressure profiling
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On 1, 11:21 pm, shall <mrf...@ihatespamearthlink.net > wrote:
> On 1 2007 10:11:08 -0800, "gscace" <gregory.sc...@nist.gov> wrote:
>
> >Hi:
>
> >I just finished building and installing a bolt-on, programmable
> >pressure profiling pump system to my uber-stable LM Frankenlinea. I
> >did this because I wanted to test prevailing ideas about preinfusion,
> >the benefits of lever machine pressure profiles, etc. on a very stable
> >platform on which selected brewing parameters may be quickly changed
> >while holding others constant to values which are the current state of
> >the art. At the same time, if the tests warranted, I wanted to make
> >the system transparent enough that I could put together similar
> >systems so that interested folks could just do a pump swap, with no
> >extra effort involved. Depending on how this all goes over the next
> >few weeks I may end up writing something more comprehensive, but for
> >now I'll give progress reports as I learn stuff. ...
>
> Great stuff, Greg!
>
> Now, is it just my imagination or are you and Ken Fox in a race to see
> who can spend the most time and money converting your high-end
> machines into Zaffiro/Amicas?
>
> shall :-)
No. I'm in a race to obsolete the GS3. Then if I ever get one, I'll
feel good about tinkering with it.
-Greg
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Date: 02 Mar 2007 04:21:34
From: Marshall
Subject: Re: Experiments in programmable, variable brew pressure profiling
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On 1 2007 10:11:08 -0800, "gscace" <gregory.scace@nist.gov > wrote:
>Hi:
>
>I just finished building and installing a bolt-on, programmable
>pressure profiling pump system to my uber-stable LM Frankenlinea. I
>did this because I wanted to test prevailing ideas about preinfusion,
>the benefits of lever machine pressure profiles, etc. on a very stable
>platform on which selected brewing parameters may be quickly changed
>while holding others constant to values which are the current state of
>the art. At the same time, if the tests warranted, I wanted to make
>the system transparent enough that I could put together similar
>systems so that interested folks could just do a pump swap, with no
>extra effort involved. Depending on how this all goes over the next
>few weeks I may end up writing something more comprehensive, but for
>now I'll give progress reports as I learn stuff. ...
Great stuff, Greg!
Now, is it just my imagination or are you and Ken Fox in a race to see
who can spend the most time and money converting your high-end
machines into Zaffiro/Amicas?
shall :-)
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Date: 01 Mar 2007 20:04:55
From: Dan Bollinger
Subject: Re: Experiments in programmable, variable brew pressure profiling
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> More soon!
>
> -Greg
Exciting stuff, Greg. I hope to hear more. I do hope that after all this work
you will use a double-blind testing. Or, if all else fails, at least a
single-blind testing scheme.
Dan
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Date: 01 Mar 2007 16:16:40
From: Ken Fox
Subject: Re: Experiments in programmable, variable brew pressure profiling
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"gscace" <gregory.scace@nist.gov > wrote in message
news:1172772667.953664.121170@30g2000cwc.googlegroups.com...
> Hi:
>
Hi Greg,
This is all very interesting.
If it turns out that there is real benefit in a pressure tail off, I can
think of a fairly simple and cheap way of producing this without huge
modifications to a machine, assuming it is plumbed in with reasonably high
input mains water pressure (obviously does not apply to your current setup
discussed herein). This would be with an additional modification of what I
have done with my "Franken-Cimbali Jr.," the rotary one, which has a
combination of a pressure regulator on the input side (set at 3.5 bar) plus
a delay on make timer that starts the rotary pump after about 6 seconds of
regulated mains pressure.
What would be needed would be some sort of delay on break timer, that would
be set to turn off the pump after a set time period, reverting back to the
open solenoid but pump-off state that makes for the preinfusion I have at
the beginning of shots, a sort of "postinfusion" if you will.
Any of these sorts of mods including what you and Andy are attempting will
require better control the grind level, because you sort of have to decide
beforehand how long you want the shot to last in order to choose when the
various pressure levels kick in, assuming we are dealing with timing
functions rather than pressure functions. This means that a shot intended
to be a 35 second ristretto that turns out to be a 25 second normale, is not
going to benefit from the intended pressure drop at the end of the shot.
Conversely, the intended-normale that turns into an unintentional ristretto
might have the low pressure part of the shot kick in way too early. So if
you don't get the grind exactly right, I think there could be some
unintended results that may or may not be good.
One advantage of preinfusion-only is that the rest of the shot can just take
its time and be whatever it is going to be. It would be much easier if any
of us were cranking out tens of shots per day, so that our grinder
adjustments were minimal and predictable. Instead, we are often making
shots after many hours of non-use, during which the humidity, the coffee,
and other things can change and unless we want to be pitching half our shots
down the drain, compromises are being made. Or at least that is what
happens to me.
ken
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Date: 01 Mar 2007 16:02:09
From: bernie
Subject: Re: Experiments in programmable, variable brew pressure profiling
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gscace wrote:
> Hi:
>
> I just finished building and installing a bolt-on, programmable
> pressure profiling pump system to my uber-stable LM Frankenlinea.
huge snips
> More soon!
>
> -Greg
>
Facinating, Greg. I stand in awe. I have to read this stuff several
times to get the whole gist and it is so impressive. Do you suspect
there would be data to fall out that would indicate that for a
particular coffee there would be an optimal range of grind/pressure?
That would be something. To find that our 25-30second pulls at 8.75-9.25
bar might be way off the optimal taste we could obtain with a given
coffee. I would intuitivly think the lighter roasts or more subtle
nuances of African coffees would be coaxed out optimally at a lower
overall pressure profile compared to maybe a dark roast or something
like a Sumatra or Sulewesi. Maybe not. I look forward to your work and
appreciate what you are doing.
Bernie (technology eludes me most days)
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Date: 01 Mar 2007 12:06:05
From: gscace
Subject: Re: Experiments in programmable, variable brew pressure profiling
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Hey cool. Email me at gscace at NIST dot GOV and I'll give you my
phone numbers. I'm gonna have a chunk of time next weekend (from the
8th thru the 12th) as wife Casey and munchkin Anneke are off to visit
Anneke's cousins and Casey's sister.
-Greg
On 1, 3:00 pm, old...@adelphia.net wrote:
> Greg,
> If you need any victims let me know I'd be MORE than willing to drink
> your espresso.
> I'm just north of you in Frederick and you're in my old stomping
> grounds.
>
> Kurt
>
> > On 1, 1:11 pm, "gscace" <gregory.sc...@nist.gov> wrote:
> > And I've got to find some test
> > victims - maybe local folk that can really hold their coffee.
>
> > More soon!
>
> > -Greg
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Date: 01 Mar 2007 12:00:12
From:
Subject: Re: Experiments in programmable, variable brew pressure profiling
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Greg,
If you need any victims let me know I'd be MORE than willing to drink
your espresso.
I'm just north of you in Frederick and you're in my old stomping
grounds.
Kurt
> On 1, 1:11 pm, "gscace" <gregory.sc...@nist.gov> wrote:
> And I've got to find some test
> victims - maybe local folk that can really hold their coffee.
>
> More soon!
>
> -Greg
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