# Guy builds 'FrankenGaggia' with flow profiling



## risky (May 11, 2015)

Pretty good effort for a DIY project.

https://coffeehustle.com/posts/q9EmQBBtPDKvFBGfv/controlling-espresso-extraction-through-real-time-flow-rate


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## hotmetal (Oct 31, 2013)

Amazing! Especially the point about 'paying for your mistakes twice' in grind size. And finding a way to break that relationship on the fly. I doff my hat to anyone that can analyse the process and build something round a Classic, RasPi and a cheap set of scales to make a gravimetric pressure profiling Classic! "No effort at all apart from teaching myself to program in Python"

I think I'd find it easier to just learn how to make espresso (that's a life's work in itself potentially though).

Interesting read, cheers for posting.

PS the guy appears to have the same nick as DoubleShot - I did a double take there!


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## MWJB (Feb 28, 2012)

Ingenious & no doubt has a useful application, but there are a few misconceptions.

The relationship between grind size & time is not linear (e.g. there is no '30second grind', nor '4 minute grind' that universally applies across differing methods), nor easy to establish. In percolation (drip/espresso) grind size is more relevant to how much water you pass through the grinds, e.g. a coarse grind corresponds to a longer brew ratio & a finer grind to a shorter brew ratio. It's possible that controlling the flow through the puck can go some way to normalising different grind settings/beans at the same setting for a given brew ratio (we do this all the time with drip pour regimes), but once you get significantly coarser, for instance, you'll need to change the brew ratio for a longer shot to maintain a decent extraction, the coarser you go the faster the flow will need to be to hit an equivalent extraction. So, you might not want to keep a 1:2 ratio at 33sec.

Grind fine, or grind coarse & there is still the same amount of "stuff to extract", too coarse and you won't hit a nominal extraction, too fine & extraction drops again. But in either scenario, the bean still contains the same amount of soluble solids, the grind (in terms of size & distribution) normally dictates how much of those solids we can wash out at a given brew ratio.


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## froggystyle (Oct 30, 2013)

Lots of words and no pictures makes me sad....

Is this the same machine that boots linked to a while ago??


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## Jumbo Ratty (Jan 12, 2015)

I clicked on the link and got

Whoa! Are you sure you want to go there? https://coffeehustle.com/posts/q9EmQBBtPDKvFBGfv/c... may try to steal your information.


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## mremanxx (Dec 30, 2014)

Jumbo Ratty said:


> I clicked on the link and got
> 
> Whoa! Are you sure you want to go there? https://coffeehustle.com/posts/q9EmQBBtPDKvFBGfv/c... may try to steal your information.


Yeh me too, I'm using McAfee. Didn't continue.


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## Jumbo Ratty (Jan 12, 2015)

mremanxx said:


> Yeh me too, I'm using McAfee. Didn't continue.


Im using McAfee too and took their advice,,,,, Froggystyle says no pictures so im not missing anything


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## ds_gaggia (Mar 14, 2016)

MWJB said:


> The relationship between grind size & time is not linear (e.g. there is no '30second grind', nor '4 minute grind' that universally applies across differing methods), nor easy to establish. In percolation (drip/espresso) grind size is more relevant to how much water you pass through the grinds, e.g. a coarse grind corresponds to a longer brew ratio & a finer grind to a shorter brew ratio. It's possible that controlling the flow through the puck can go some way to normalising different grind settings/beans at the same setting for a given brew ratio (we do this all the time with drip pour regimes), but once you get significantly coarser, for instance, you'll need to change the brew ratio for a longer shot to maintain a decent extraction, the coarser you go the faster the flow will need to be to hit an equivalent extraction. So, you might not want to keep a 1:2 ratio at 33sec.


I completely agree about the nonlinearity issue and the importance of the brew ratio. Perhaps I should have phrased what I wrote in the Coffee Hustle post a bit differently. My point is not that adjusting the flow rate makes it possible to pull a good espresso shot for any grind size; but rather that once the grind is within a certain range (I would say in the espresso range, within 10 micro clicks on a Vario), I don't need to worry too much about dialing in super precisely. My guess is that within this range, the relationships between grind fineness and extraction time, and between grind fineness and extraction rate, are both monotonically increasing. These assumptions probably don't hold across the entire range of potential grind sizes (from French press to Turkish grind settings). Too coarse, and the relationships are probably flat or nearly flat; too fine, and they are probably decreasing (due to channeling). But I am not interested in trying to pull a shot with such overly coarse or overly fine grinds.

About the brew ratio: this is the main variable I play with now that I have stopped adjusting grind size. Some coffees (high-grown, dense, or lightly roasted beans) benefit tremendously from higher brew ratios. But there's nothing surprising here: this should be true regardless of whether you adjust flow rate or not.

After using this setup for several weeks, I have 3 observations:

- I have become lazy when it comes to dialing in my grinder. 5 clicks up if I switch from dark to light roasts, 5 clicks down if I switch from light to dark; and it works.

- Not being able to rely on extraction time as a diagnosis tool is a bit disconcerting at first and takes some time getting used to. I can only rely on my taste buds and the observed flow profile. Overall, I would say that my shots taste much better than before, and my Gaggia has become considerably more forgiving. But when it comes to improving a shot, adjusting grind size does not have as much of an effect as before (of course, it's a feature, not a bug!); so I need to pay much more attention to the brew ratio, the preinfusion/pressure ramp-up phase (which has a big effect on what happens in the second half of the shot) and the temperature.

- For a given brew ratio and extraction time, I usually get my best results when the pump slows down in the last 10-15 seconds of the shot (sometimes dramatically, all the way down to 10 or 20% of its full power, which seems very weird). I can't measure pressure on this machine, but I would guess that pressure actually drops a lot during these shots. Maybe the full 9 bars are not necessary for the entire duration of the shot? Or the grind size required to restrict the flow and reach the desired brew ratio in, say, 30 seconds under 9 bars of pressure does not quite coincide with the grind size that makes the cup taste great in 30 seconds with variable flow rate... Any thoughts?

For those who couldn't access the original post:

http://coffeehustle.com/posts/q9EmQBBtPDKvFBGfv/controlling-espresso-extraction-through-real-time-flow-rate

Links to pictures/videos are here:

http://www.gaggiausersgroup.com/index.php/topic,1149.0.html


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## Jumbo Ratty (Jan 12, 2015)

ds_gaggia said:


> For those who couldn't access the original post:
> 
> http://coffeehustle.com/posts/q9EmQBBtPDKvFBGfv/controlling-espresso-extraction-through-real-time-flow-rate


Still get

Whoa! Are you sure you want to go there? https://coffeehustle.com/posts/q9EmQBBtPDKvFBGfv/c... may try to steal your information.


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## Dylan (Dec 5, 2011)

Jumbo Ratty said:


> Still get
> 
> Whoa! Are you sure you want to go there? https://coffeehustle.com/posts/q9EmQBBtPDKvFBGfv/c... may try to steal your information.


What is causing that, your browser or anti-virus?


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## risky (May 11, 2015)

McAffee is being overly paranoid.









Don't see what it thinks is the issue.


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## shaunclarke (Nov 30, 2011)

The link is safe. My work laptop is loaded up to the gunwales with AV software etc. Interesting article. How far do you go to obtain perfection???


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## dsc (Jun 7, 2013)

From a control perspective this is a fairly easy task, using feedback from a scale is easy, same goes for pressure feedback via pressure trandsducer or flow feedback via flowmeter. This is really basics and what enrages me is that manufacturers cannot be bothered to release a machine which offers the lot. VA recently announced the gravimetrics which I think is all about feedback from a scale. If that is indeed true my only answer is "WTF, why so late?".

T.


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