Well the title is an obvious reference to the 'Peppina marries MiniGaggia' thread, which this thread is an offshoot of!

The designs there and here both use brew-temperature boilers/kettles (as opposed to the pressurized boiler Pavoni design) but differ in the method of delivering and heating the brew water.

"Conti" refers to the Conti Comocafe and its displaced piston/chamber
"Achille" refers to the Gaggia Achille's Heat Exchanger system.

This 'Front Page' will serve as an index of sorts, to reflect the current design and link to the relevant posts.

There are two designs, the first is a basic espresso-only machine, while the second will incorporate all the design elements brought up in this thread.

First- Espresso only.

The main elements of this design are-

1. Heat Exchanger in a non-pressurized boiler.

2. Piston position chosen for stability.

3. One-way valves on the piston (like the Achille design).

4. Group attached directly to the boiler.

Second- Super machine!

All of the above and also including-

1. Pressure gauge for brew pressure.

2. Control of temperature profile during the shot.

3. Steam for milk drinks.

4. Hot water tap for tea/cocoa.

5. More+better temperature displays.

6. PID

There are many design elements which are up in the air, but the immediate goal of this thread is to hammer out a basic design which could be tested by many people. Some parts of the design would have to be custom made, some parts could be bought or 'borrowed' from stock machines. I have yet to find a site selling the stock Achille group.

Custom made-

HX tube.
Piston chamber.
Frame.

Stock-(of course it is important to choose compatible parts! I haven't done a very good job of that with these links!)

Group.
Dispersion block.
Dispersion screen.(1)
Portafilter + baskets.
Piston.
One-way valves.
Lever mechanism.(1)
Complete lever mechanism w/out chamber (1, 2)
Temperature displays/controls.
Fittings.(1)
Heating Element.

To add more links please PM me.

Thanks for all contributions!

Henry

One big question:

Should the goal be to produce a 'flat' temperature profile or to have control over the temperature profile?

Opinions needed!

I think the question of whether flat or falling profiles are better is very much up in the air, and I would personally love to have a machine which could produce both! There are currently no commercially available machines which allow control over both pressure and temperature profile (during the shot).

With the HX design it would be possible to create flat, falling, and rising profiles by using (for example) 3 small boilers (each warming a portion of the HX tube) or one compartmentalized boiler with separate heating elements.

Or to compare flat and falling, a single boiler with two HX tubes, one long and one short . . .

While it would be interesting, perhaps the first goal should be to make a functioning flat-profile machine?

Henry

Some relevant reading-

Dave's (Cannonfodder) explaination of the Achille Piston and HX.

Jim Schulman's original review of the La Peppina.

Gaggia Achille parts diagram


FE-AR La Peppina parts diagram


Henry

hbuchtel wrote:Well the title is an obvious reference to the 'Peppina marries MiniGaggia' thread, which this thread is an offshoot of!

Hello Henry,
We are fortunate to have a great deal of information from that long running thread. There were a lot of good suggestions and part and material selection and location possibilities. So, lets get on with the show!

The two proposed designs both use brew-temperature boilers/kettles (as opposed to the pressurized boiler Pavoni design) but differ in the method of delivering and heating the brew water.

The main elements of this design are-

1. Heat Exchanger in a non-pressurized boiler.

I like the directions you were going in the other thread. ( HX coil experiments could be accomplished by using an electric deep fryer vs. electric fry pan for the HX coil shape and orientation.) A torn down and modified monoblock pump machine or even steam toy would furnish the group that , for experiments, could be isolated and separately held at temperature from the metal of the HX kettle pot or pan.

2. Piston position chosen for stability.

1.With the piston placement being movable in the design, The piston could be driven by a rack or a leverage system. ( As an aside, The same lever that pulls the shot could, at choice, be used to drive water into a second steam flash-boiler. This would be done by a simple leverage ratio and mechanical flow switch {two way}change.) The difference in leverage is to give high pressure with a low volume into a small flash-boiler to provide steam.
2. I've checked out air / liquid cylinders and the food safe ones are in the $200 dollar range for what we might want. Therefore I might suggest that we make our own using the information from the other thread on the super "V" rings.
3. Also, lets think about Hot water for the drinks of our not so enamored acquaintances, or their children.

3. One-way valves on the piston (like the Achille design).

I shall re-read Cannonfodder's article on the Achille. It does seem to me that since the kettle is at X °C or °F it could be left as stale water ( thereby requiring attention.) Or as in the Achille it would be refilled by the one way valve ( thereby being covered and unpressurized but not stale.)

(I will update this to reflect any changes in design)

There are many design elements which are up in the air, but the immediate goal of this thread is to hammer out a basic design which could be tested by many people. I personally should have time to make a working model in January.
Thanks for all contributions!
Henry

Many of the above possibilities may seem mutually exclusive but could be integrated. Have fun!
Thanks for the opportunity!
Sincerely
richard / Espressme

hbuchtel wrote:One big question:
Should the goal be to produce a 'flat' temperature profile or to have control over the temperature profile?

In Jim Schulman's review of the Elektra SemiAutomatic, the temperature plot over the course of the extraction is humped, i.e. it rises and then falls almost but not quite symmetrically, something like this:

∩

Jim says the espresso tastes great and I don't doubt it. My bias, if it's a bias, is to avoid having the temperature fall into sour range or rise into bitter range for more than a couple of seconds during the extraction. Some flavors are temperature dependent -- i.e. the same aromatic chemical tastes different on the tongue at different temperatures. But the extraction of some chemicals that taste bad at any temperature occurs only when the water temperature rises too high.

The former tastes could be ameliorated by the final temperature in the cup being in the right range. The latter tastes, however, need to be masked with sugar and/or lots of milk.

Regards
Timo

I neglected to say in my earlier post that the House of FE-AR appreciates your forbearance, Henry, in seeing to it that the hot-tempered Achille does nothing to besmirch its name.

Per your request:

---------
If the Comocafe had a cool water reservoir placed behind its kettle, or on the side of the machine opposite the lever for better balance, water could be drawn from the reservoir, through the HX-kettle, and down into the piston chamber.

You might even insert a thermoblock between reservoir and HX kettle to bring the water up to temperature, using the HX-kettle either to raise the water a few more degrees to the desired temperature or to absorb excess heat if the thermoblock had overshot the mark. You might then be able to use the same thermoblock for steam as well, using the HX-kettle to buffer the undershot and overshot temperatures.

Most impressive, like the Centre Pompidou in Paris, the HX's copper coil works would be visible through the glass
------

Regards
Timo

A lot of QUESTIONS-

Assuming the simplest possible construction (single boiler, no pre-heating of fresh water, thermostat on boiler, goal of flat-profile doubles)

Questions to be answered-

- if part of the tube is close to or directly above part of the heating element, will this cause a high temperature 'pocket'?

If yes, how can this be avoided in a lo-tech manner?

- How long and wide does the HX tube have to be?

a. Length: (assuming a 20ml flush and 60ml pull)

(1) How much does the temperature of the water in the boiler fall when 80ml of cool water enters the HX tube? (20ml quickly and 60ml slowly).

(2) Does it drop enough to trigger the thermostat?

If yes, perhaps a thermostat over-ride switch is needed.

(3) How much does the drop in boiler temperature affect the temperature of the water in the group-end of the HX tube?

b. Diameter

(1) General HX tube question- Does water in a horizontal tube travel in blocks? When cool water is forced into the end of the tube will it stay there or will it disperse throughout the tube?

Comments: My assumption is that cold water entering the tube will not draw much heat from the water in the front of the tube. To prevent this from happening, the HX tube should enter from the bottom of the boiler (so that the cold water stays at the end of the tube) rather then horizontally or from the top.

-----------------------------------------------------------------------

The answers to the above questions should give us a minimum length and a maximum diameter for the HX tube.

Henry

espressme wrote:( As an aside, The same lever that pulls the shot could, at choice, be used to drive water into a second steam flash-boiler. This would be done by a simple leverage ratio and mechanical flow switch {two way}change.) The difference in leverage is to give high pressure with a low volume into a small flash-boiler to provide steam.

That is a great idea! One consideration is how the valve* would affect the flow of water from the piston to the puck . . . I think it is important not to have any tight spots so that there is a lot of feedback from the flow at the puck.

*valve: Did you mean that you could switch a valve so that pressure from the lever could make espresso OR fill the steam boiler?

Does this picture show what you mean? (proportions etc way off . . .)



No comments on your other ideas yet, more reading and thinking to be done!

Henry

hbuchtel wrote:That is a great idea! One consideration is how the valve* would affect the flow of water from the piston to the puck . . . I think it is important not to have any tight spots so that there is a lot of feedback from the flow at the puck.
*valve: Did you mean that you could switch a valve so that pressure from the lever could make espresso OR fill the steam boiler?
Does this picture show what you mean? (proportions etc way off . . .)
image: http://www.home-barista.com/forums/userpix/177_SSL22581_1.jpg
No comments on your other ideas yet, more reading and thinking to be done!
Henry

Hello Henry,
That is correct, A valve would do as your diagram suggests. At the same time the lever ratio could be changed. That may not be necessary as the boiler feed pressure would only be about 1.3 Bar max at 260°F. I might suggest a flow restricter, though, to even out the admission of water to the boiler. Stop the lever pressure and the steam stops. Also, a one way valve would prevent steam from entering the piston.

A suggestion is that the steam boiler would be a flash boiler, operating as a wet boiler only when steaming. That is how the simple two heat temperature pump machines work. A large thermal mass at a high temperature giving off heat to a liquid. Obviously, There has to be enough mass at temperature to steam a reasonable amount of water. An OPV would be suggested!

The use of another diverter valve would be to allow water to go to a hot water tap rather than the group. That would allow construction of other drinks.

As to the questions for the HX, Perhaps someone can do the heat transfer equations.
A PID and high wattage element would be necessary to keep an even temp in the kettle.

Consider that one successful machine had a poppet valve like an IC engine as the diverter and anti backflow valve at the Group ( La Peppina has the washer. Since the HX entrance location is relatively inconsequential, that may work.

A spreadsheet seems to be in order to keep track of all the feature possibilities.

I operate on TLABR! = That looks about right. So, I am wondering what would happen if I were to attach a lever and pump to my old DeLonghi Pump machine with the Stainless steel boiler/monoblock????? And, if that works, a PID? Seems that There was an article on CG that dealt with a PID mod'd Hamillton Beach that gave great results. Probably would require flushing after steaming though. Is that another thread????

Pleasant thoughts to all!
richard
PS It just dawned on me where you live!

PPS It may be an Idea to have an editable 1st page like LMWDP to hold the features and ideas to make back tracking easier. An index so to speak? That would be a good place for un-answered questions! You could do that by editing your first introduction page as needed.

Hi Folks,
Here is a thread relevant to the discussion:
http://www.home-barista.com/levers/clevis-to-lever-further-explorations-in-espresso-space-t1243.html
Best regards
richard / espressme