Buyer's Guide to the Gaggia Achille - Page 4

[cannonfodder]

Ok folks. Since the big question is how does it work versus the how good does it work (which is what I was starting with), I decided to shift gears.

I came home from the hospital this evening and tore the machine down. I have the answer and lots of photos to explain how the mystery piston works. You will have to give me a day to edit the photos and write the explanation but that should answer all the questions at hand.

Timo, while I do not have metric calipers, I did measure just about everything down to a thousandths of an inch (give or take one, one thousandths) so that should be close enough to calculate anything. A simple imperial to metric calculator will get you closer than you probably need.

Give me a day and the mystery will be revealed, and it does include a one way valve. Forget everything you know about lever machine operation, this is very different. Or at least different from anything I have seen, may be old school for others.

[peacecup]

Ok folks. Since the big question is how does it work versus the how good does it work

Ahem...

A voice in the wilderness for the latter. Although I'll admit to a certain acousto-centric bias towards lever machines (i.e. silence), I am most interested in what's in the cup, not how it got there. I hope, therefore, that you'll be able the summon all the kings horses and all the kings men, so we can see more video of Humpty in action again...

PC

[cannonfodder]

Don't worry. I am swimming in coffee from our wonderful sponsors. Keep in mind that I am still in the cursory examination of the machine. I have only been pulling shots for a week. Unlike the buyer's guide, the bench is an ongoing discussion and there is much more to discuss.

I am planning on many more photos and video.

[timo888]

Dave,
In the coolling flush video, it appears as though three pulls yields slightly more than 4 ounces. Is that right? So a single pull yields about about 1.3 ounces of water?

I asked earlier about warming flushes after initial heat-up when the ready light says the water is at temperature, and you said that the water isn't hot enough (doesn't even burn the skin) if pulled after a single warming flush. But if you were willing to use as much water to warm the group as you use to cool the group -- if you ran four ounces of water through the group in three pulls--would that bring the machine to the point where you can pull a shot that isn't sour?

Regards
Timo

[cannonfodder]

Update on the double basket capacity.

My spider sense was correct, 17 grams. I ran three doses using my 'normal' technique. No scoops, nothing fancy, I just dose until it feels correct. 17 grams on all three, the portafilter locks in with no group imprint on the puck surface. I up dosed to 18 grams, the puck shows a very light imprint of the shower screen screw so I would be confident in saying a 16-17 gram dose is just right.

[cannonfodder]

Dave,
In the coolling flush video, it appears as though three pulls yields slightly more than 4 ounces. Is that right? So a single pull yields about about 1.3 ounces of water?

I asked earlier about warming flushes after initial heat-up when the ready light says the water is at temperature, and you said that the water isn't hot enough (doesn't even burn the skin) if pulled after a single warming flush. But if you were willing to use as much water to warm the group as you use to cool the group -- if you ran four ounces of water through the group in three pulls--would that bring the machine to the point where you can pull a shot that isn't sour?

Regards
Timo

I would agree. I did some testing this morning on that exact point. You can quick heat the group but it still may not be completely thermally stable yet. You are heating a big chunk of brass.

I tweaked down the Pstat last night while I had the machine apart (I have photos of that as well). I turned it down some, but it needs another adjustment down. I am running 1.2-1.35, still high in my book. It appears to need a little less flushing but I want to get a 1.0-1.1 cycle.

On my water capacity test I pulled 5 measured full lever strokes and received a 2oz dose each time. You can short cycle the lever and only pull a quarter shot if you want. So when making a single, you could raise the lever a half to three quarters position and pull the shot.

Dan (HB) will be getting a machine soon as well. He will be able to confirm or refute my measurements and will be making the thermal measurements with his data logger. There is much more to come.


More testing is needed before I make any final opinion on the machine.

Stay tuned for the mystery of the water pumping cycle.

[cannonfodder]

Drip tray, my first nit pick

I knew the drip tray was small when I put the machine together. I was reminded of that point after 3 double shots. I overflowed the drip tray. Thank goodness for that sealed drip tray base.

The cover on the drip tray just sits on the basin. There is no recessed groove or sticky backing to keep it from moving. The cover is brushed stainless to match the base and the punched holes do a reasonable job of draining. The two large holes match up with the spouts on the portafilter so any offending drips fall through. The third large hole is a finger grip which aids in removing the cover.


Under the cover is a black plastic drip tray. Filled to the brim it holds 10oz but you will never remove it without spilling its contents. Again a very good reason for the sealed basin under the drip tray, spill cleanup is very easy. Realistically, 8oz is all you want in that tray. It is a drip tray in the true sense of the phrase. You will not be pulling your cooling flushes into this. I use a Pyrex container for flushing.


FYI, the Achille drip tray is still larger than the legendary Cremina, but much smaller than your typical heat exchanger pump machine.

[cannonfodder]

Timo, here are you lever dimensions;

The lever from end of handle to end of threads measures 10.06 inch, the thread portion is .506 inch, the lever shaft diameter is .592 inch.

The lever pins are stainless steel and measure 1.166 inch over all length, top of screw head to end of threads and .229 inch diameter (measured at pin center).

The piston (left to right) pin to hinge pin centerline is .983 inch (give or take .001). From the group pivot assemble (piece the handle screws into) is 2.206 inches from the face (left end) to the hinge pin centerline.

The group piston chamber measures 1.730 inch in diameter but I forgot to measure the stroke. The group piston shaft measures .470 inch diameter.

The two pieces in the back are the sliders for the rear pin. The La Pav's use a solid tube, the Achille uses a two part pin that rides in a tongue and groove in the group, once again stainless steel.

Good enough?

[timo888]

Indications that the machine has been designed to produce brew pressures somewhat higher than, say, the Cremina:

the relatively small (43mm) piston cylinder diameter

the lever's greater mechanical advantage [i.e. ratio of length of work-arm to the length of the effort-arm] --only 25mm distance between pins on-center

thicker lever arm (though the pins themselves are apparently not more robust, but they may be made of stronger metal?)

Regards
Timo
P.S. How do the lever dimensions and the piston diameter compare to the same on the main lever competitors, Pavoni, Elektra, PV Lusso?

[peacecup]

I confess to an interest in technical issues, particularly as they relate to what ends up in the cup:

I don't think the drip tray is a nit-pick - you may have noticed the giant removable drip try in my Ponte Vecchio photo- this is borrowed from my old Estro Vapore, which sits sadly neglected under my desk (and which, btw, is a very well-designed and constructed piece of equipment for a home appliance). The PV Export has no removable drip try, just a depression in the aluminum base.

16-17 gram dose is just right.

I usually dose 15 g in my 45-mm double basket. These usually produce 1.5 oz doppios, which I guess are really ristrettos. Still, assuming a linear dose-voulme relationship, my coffee is stronger than an Achille doppio (15g:1.5oz vs. 17g:2.0oz). I can get 16g in and pull a 2 oz shot. With such a larger diameter PF I assumed the Achille would hold more coffee. The PF must be shallower, which brings us to:

the relatively small (43mm) piston cylinder diameter

Is this correct? This would seem to put a 43-mm flow over a 58-mm puck - is this not a recipe for uneven extraction? The PV piston and PF are of equal 45-mm diameter. I haven't seen any hint of side-channeling since about the first week of operation.

P.S. How do the lever dimensions and the piston diameter compare to the same on the main lever competitors, Pavoni, Elektra, PV Lusso?

Do the lever dimensions matter much on the spring-lever machines? (edit - I guess they do!). They have to compress the spring, but the spring does the water (I'll admit to helping out by pushing down directly on the piston when I want more pressure). The PV lever is 24 cm long from the piston cotter to the tip of the plastic handle. The lever appears to be ~1.4 cm diameter (about the same as the Achille). The two pins are ~1.6 cm apart, giving a rather high work-arm ratio? This would suggest a strong spring needs to be compressed? That, plus the narrow-diameter group gives a relatively high pressure?





PC

[peacecup]

Lever pin diameter ~5 mm.

[timo888]

the relatively small (43mm) piston cylinder diameter

Is this correct? This would seem to put a 43-mm flow over a 58-mm puck - is this not a recipe for uneven extraction? The PV piston and PF are of equal 45-mm diameter. I haven't seen any hint of side-channeling since about the first week of operation.

The small piston with larger basket would not necessarily cause uneven extraction. The gicleur and dispersion screen design could easily compensate.

The PV lever is 24 cm long from the piston cotter to the tip of the plastic handle. The lever appears to be ~1.4 cm diameter (about the same as the Achille). The two pins are ~1.6 cm apart, giving a rather high work-arm ratio? This would suggest a strong spring needs to be compressed? That, plus the narrow-diameter group gives a relatively high pressure?

The closer the pins are to each other, the greater the mechanical advantage. It's not unreasonable to surmise from the fact that the PV pins are only 16mm apart that there's a hefty spring inside. That is probably the case, though it's not necessarily the case. The lever dimensions would make the spring easier to compress, whatever size it was.

Yes, if the force remains constant, the pressure increases as you change the area to the which the force is applied. Larger area, lower pressure; smaller area, higher pressure.

Regards
Timo

[cannonfodder]

Hold up folks, you only have half of the information. I am working on the rest. Forget everything you know about how a lever machine operates. The piston does NOT push water into the shower screen, it pushes COLD water into the HX, then from the HX into the lower group, out a dispersion block and out the shower screen.

Hold your horses. I am working on a very long and detailed post with lots of photos that I hope will explain how this nifty thing works.

[cannonfodder]

Heat exchanger lever operation

The Achille has a very innovative system for pumping water through the group. I will try my best to explain how it works. Let me start by saying you need to forget how most piston-driven lever espresso machines operate. Clear your mind, this is not your normal lever espresso machine. In fact, it is more like a pump-driven heat exchanger espresso machine, but instead of an electric pump, you are using a hand water pump.

The Achille works with a pressure and vacuum action. The key is in the piston design. The group piston contains a hollow bolt and a one-way ball valve that allows water to flow from above the piston to below the piston on the upstroke, but closes under pressure of the down stroke.

A single up and down stroke

As the piston sits at the bottom rest position, the space above the piston in the piston chamber is full of water. Don't worry about how that water got there, just keep reading. As you raise the lever, a check valve on the heat exchanger water reservoir shuts so water can not be pumped back into the water reservoir. While the piston rises, the water that is above the piston flows through two holes just above the top of the piston:



The water continues through a hollow shaft down the center of the piston and out a large hex bolt with tiny holes drilled all over the face (think floor drain grating) on the bottom of the piston:



At the top of the lever stroke, the water that was above the piston is now below the piston. Now you start the down stroke. The one way valve in the piston closes. The water in the piston chamber is now pushed out through a tube in the bottom of the piston chamber and into the heat exchanger in the top of the boiler. It circulates through the heat exchanger coils and back out through a lower tube and into the lower group assembly. The water moves through the lower assembly and into the group chamber, then down through the dispersion block and out of the shower screen.

The diagram below shows the flow from start to finish:


Water flow to group exit


Water exit hole to dispersion block


Shower screen and dispersion block

During this down stroke, the space above the piston is drawing a vacuum because the one way valve in the piston is closed. Now the check valve in the heat exchanger reservoir tube that prevented water from flowing into the heat exchanger reservoir during the upstroke opens under the vacuum. The vacuum now sucks water from the heat exchanger reservoir back into the space above the piston. Remember the 'Don't worry about how that water got there' sentence at the beginning? This is how that water got above the piston.

In a nutshell: You raise the lever, the water above the piston moves to below the piston. You push the lever down. The water that is now below the piston is pushed out, passing through the HX and then into the water dispersion block. At the same time, the vacuum above the piston pulls water from the heat exchanger reservoir to fill the void above the piston.

A real stroke of genius

The piston is never in hot water. It is pumping from the cold side of the tank, just like an electric pump. Because the piston is isolated from the heat of the group, the seals will last for years. The piston is not exposed to coffee oils because the brew chamber is completely separate of the group piston. So there is never any need to remove the piston for cleaning. You just clean the dispersion block and shower screen just like any other pump operated machine.

[cannonfodder]

After you pull a shot, don't forget to dump the puck, or it may be stuck to the shower screen an hour later.

[hbuchtel]

Ah-ha, a wolf in sheeps clothing!

Thanks for the description, finally that parts diagram makes sense!

In Jim's Semiautomatica review he mentions the theory that it is the straight water path through the dispersion block that is responsible for lever machines distinctive shots, is the Achille dispersion block similar in design to the Elektra?

Henry

[cannonfodder]

Ah-ha, a wolf in sheeps clothing!

Thanks for the description, finally that parts diagram makes sense!

In Jim's Semiautomatica review he mentions the theory that it is the straight water path through the dispersion block that is responsible for lever machines distinctive shots, is the Achille dispersion block similar in design to the Elektra?

Henry

I cannot say. Jim will have to chime in on the Elektra comparison. The water path is most definitely straight down.

The dispersion block is aluminum on the Achille. I would much rather have stainless steel for ease of cleaning, but it still pulls a darn good shot.

[cpl593h]

Wow. That's such a brilliant design.

[another_jim]

I cannot say. Jim will have to chime in on the Elektra comparison. The water path is most definitely straight down.

The dispersion block is aluminum on the Achille. I would much rather have stainless steel for ease of cleaning, but it still pulls a darn good shot.

From the picture, the water path to the dispersion block is very off-center; but it's hard to tell how well the block straightens and evens things out. The issue would be somewhat moot on a machine like this if it had a bottomless, since one can start with gentle pressure on the lever until the basket bottom shows an even black, and only then punch it to get the right flow.

[cannonfodder]

I was referring to the physical water direction not the location in relation to the center of the block. Like an E61 whose water path is a 45 degree angle into the dispersion disk.

From the parts diagram, the Elektra has two dispersion blocks to better distribute the flow. But unlike the Elektra, I doubt a person will be able to generate the same instant 13bar pressure the Elektra's pump can ramp up to.

I never made a lever pull with the shower screen off to watch the flow out of the block. Sounds like a good reason to make another video.