Buyer's Guide to the Gaggia Achille - Page 24

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cannonfodder (original poster)
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#231: Post by cannonfodder (original poster) »

In the pursuit of knowledge, I decide to take some temperature measurements on the Achille to see what is going on in the basket. These were taken with a type K thermocouple on a calibrated Fluke 189 meter. The bead TC was simply placed on top of the puck using the popular 'over the lip' placement of the thermocouple. I settled on an average rebound time between flush and preinfuse of 12 seconds simply because that was as fast as I could remove my flush container, put the TC on the portafilter, lock it into the machine and start the datalogger. The rebound is not exact, one shot may be 12 seconds the next may be 14 which may account for the slight variation in temperature from shot to shot. However the general temperature curve remains the same.

I used a standard dose of 17 grams, a three pull flush (to help compensate for the added time needed to fiddle with the meter and thermocouple), a half pull preinfuse which you can see in the stair step around seconds 4-5, followed by a full lever pull for a total of 1.75oz dispensed. I pulled three shots back to back pausing between each shot to key in the datalog numbers on the computer.

One big surprise was how low the temperature readings were. I will partially attribute the low reading to the thermocouple bead laying on the surface of the puck. Once I removed the portafilter, the thermocouple had slightly imbedded in the pucks surface. It was just enough to scrape the surface of the puck as I unlocked the portafilter. As a reference point, I pulled a single shot form my Faema two group for comparison. On that shot, the thermocouple did not make an impression on the puck. It rode between the pucks surface and the shower screen giving me a reading that I expected.

More shots will be needed. The next series I will shorten the flush to two pulls. Until then, here are my cursory graphs.





Dave Stephens

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timo888
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#232: Post by timo888 »

cannonfodder wrote:In the pursuit of knowledge, I decide to take some temperature measurements on the Achille to see what is going on in the basket. These were taken with a type K thermocouple on a calibrated Fluke 189 meter. The bead TC was simply placed on top of the puck using the popular 'over the lip' placement of the thermocouple. I settled on an average rebound time between flush and preinfuse of 12 seconds simply because that was as fast as I could remove my flush container, put the TC on the portafilter, lock it into the machine and start the datalogger. The rebound is not exact, one shot may be 12 seconds the next may be 14 which may account for the slight variation in temperature from shot to shot. However the general temperature curve remains the same.

I used a standard dose of 17 grams, a three pull flush (to help compensate for the added time needed to fiddle with the meter and thermocouple), a half pull preinfuse which you can see in the stair step around seconds 4-5, followed by a full lever pull for a total of 1.75oz dispensed. I pulled three shots back to back pausing between each shot to key in the datalog numbers on the computer.

One big surprise was how low the temperature readings were. I will partially attribute the low reading to the thermocouple bead laying on the surface of the puck. Once I removed the portafilter, the thermocouple had slightly imbedded in the pucks surface. It was just enough to scrape the surface of the puck as I unlocked the portafilter. As a reference point, I pulled a single shot form my Faema two group for comparison. On that shot, the thermocouple did not make an impression on the puck. It rode between the pucks surface and the shower screen giving me a reading that I expected.

More shots will be needed. The next series I will shorten the flush to two pulls. Until then, here are my cursory graphs.
At what point in these 35-second extractions, following a three-pull cooling flush, does the Achille's heating element kick on?
Regards
Timo

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cannonfodder (original poster)
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#233: Post by cannonfodder (original poster) »

Just got back from a business trip, spent a week on the dark side of the moon.

Normally, I would not run a 35 second extraction, but I ran the shot volume longer than I normally would just to see what happens.

I was not watching the heating element on those extractions so I can not say. The element was still heating as I started the shots. The three pull flush drops the boiler pressure to around .9 bar.
Dave Stephens

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#234: Post by cannonfodder (original poster) »

I spent more time with the Achille tonight pulling shots and trying different timings and flush amounts. I also tried moving the over the lip thermocouple around but never got what I would call a reliable temperature. I believe the general temperature curve is a good representation of what is going on in the portafilter.

I settled on a pressurestat setting of 1.0-1.2 (or 1.98 but close enough to say .2). A two pull flush works best followed by an 18 second recovery. That was just enough time for the boiler to recover and the heating element to shut off. The half pull preinfuse is made just as the heating element clicks off. That allows me to get through most of the shot before the element kicks on at around second 23/24. At around 27 seconds I start to get a slow rise in temperature as the energized element starts to flash heat the water in the HX line.

This is the flattest profile I achieved from a dozen different flush/recover combinations. Don't be fooled by the low temperature reading, I can assure you this was not a 191F shot, but due to the over the lip on the puck thermocouple placement all of the temperatures read low. Do not view this graph as an absolute temperature profile, but as a temperature trend profile. I am confident based on my tasting that this profile is representative of the general temperature curve of the Achille.



Based on the rise at the end of the shot, using Dan's idea of allowing the machine to recover after the flush then powering off the heating element, you should be able to produce a nice, flat temperature profile. For darker roasts, allowing the machine to heat, then power off the heating element, do a two pull cooling flush followed by an 18 second recovery should produce a flat and cool temperature for those blends that work best in the sub 200F range.

For those of you wondering just how hard I have run the Achille over the past couple of months.

This is the new portafilter.


This is the portafilter after lots of coffee. I have worn a good bit of the chrome out of the PF.
Dave Stephens

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#235: Post by HB »

cannonfodder wrote:Don't be fooled by the low temperature reading, I can assure you this was not a 191F shot, but due to the over the lip on the puck thermocouple placement all of the temperatures read low.
That's a larger delta than I've seen with other over the lip measurements.

I'm reminded of one of the interesting discussions of the thermofilter Bench review that centered around the meaningfulness of temperature profiles. I've concluded they are excellent for tuning technique to increase reproducibility, but I don't think either the thermofilter or puck TC placement accurately captures the coffee's "temperature experience." Seeing the Achille's profile and thinking about its aluminum dispersion block versus others' brass dispersion block, I suspect that laying the TC across the top of the puck is measuring the dispersion block temperature more than the brew water temperature.
Dan Kehn

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cannonfodder (original poster)
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#236: Post by cannonfodder (original poster) »

I have used the over the lip TC on my Faema and Isomac and gotten readings that I expected based on taste and knowledge of the machines. But this Achille keeps me guessing as to why I get those low temperatures.

I wonder if I way under dose the basket (12g) and over the lip meter the results if I would get a more accurate water temperature. The mini puck would be providing just enough resistance to regulate the water flow while suspending the TC in a water cushion.

I may give that a try tomorrow just for fun. I have down dosed, but not that drastic.
Dave Stephens

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#237: Post by cannonfodder (original poster) »

After a couple of months I believe I have pushed the Achille to its limits and exposed both its strengths and weaknesses. I have not had any surprises for a couple of weeks now and I can pull shots with consistent quality. The thermal measurements are the only thing that vexes me. For some reason I just cannot get a good temperature map. I am confident in the general temperature profile, but the numbers are nowhere close. She wants to keep at least one secret from us.

I will continue to use the machine for another few weeks until my time with it is up but do not anticipate any other revelations. But then again, if they were anticipated, they would not classify as a revelation would they.

So I will wrap up my 'official' bench review by simply saying that the Achille is a joy to use. The machine is quick to learn, more forgiving than most levers, superb materials in craftsmanship with one or two idiosyncrasies. Overall, it is a solid lever machine that produces a wonderful espresso.

One final parting video of a bottomless double ristretto...

«missing video»
Dave Stephens