This is a continuation of the Conti marries Achille thread over in the lever machines forum. As this prototype is powered by a vibe pump (rather then a lever as originally planned) I thought it would be more appropriate to continue it over here.

Basically it is a heat exchanger machine with the boiler (kettle) at brew temperature rather then steam temp. The ~2.5 liter kettle is only there to provide heat for the long HX tube coiled inside it.

Here are the original drawings and a few pictures of the functioning machine-






The pump and manual pressure valve are off to the left, and the PID and electromagnetic relay are off to the right.


A few technical details:

• Group from Gaggia Espresso
  2.5 liter galvanized steel kettle
  1000W heating element
  5 meters of ID6mm nylon tubing (rated at 120C, 3.0Mpa)
  no-name vibe pump

This afternoon I got my grind and dose right and had the most extrordinary ristretto I've ever had... no exaggeration... the first sip was like a sunrise, gone in a moment then a slow wash of... no words for that flavor! The aftertaste wasn't pleasant, perhaps the temp was a bit low or there was a bad bean...

Here is a video of the shot. You can see the pressure up in the left hand corner, I held it at about 9bar. It was 15.5g of a mix of Colombian, mokha, and mandheling (the last of my greens!) pulled at 100C (un-calibrated) in a CMA double basket. (Warning- the vibe pump makes a racket... turn your volume down!) And the shot. Probably not much crema by the standards of the folks here, but it looks good to my lever-trained eye!


Enjoy!

Henry

I don't understand the thermosyphon line in the drawing. There is no thermosyphon loop as shown.

Congratulations Henry!
You have gone a lot further than most in scratching the itch for a better method of brewing.
Once the test bed works consistently, I await the package!
Cheers
Richard

old442 wrote:I don't understand the thermosyphon line in the drawing. There is no thermosyphon loop as shown.

Hello Kurt, the thermosyphon line is there, though hard to see... in the last photo the white tube is visible coming from behind the group and attaching low on the front side of the kettle (rather then at the bottom as in the drawing).

The thermosyphon works because the Gaggia groups have a hole (originally the water inlet) coming from the back of the group through to the inside of the group (see pic below). I drilled a small hole (see the first photo in the original post) in the kettle at the opposite corner from this hole so the water would wash over the surface of the group. I really don't know how much this helps, but it should help to keep the group closer to the temp of the water in the kettle.



Hello Richard! Any plans to make one of these yourself? I'm sure you could do a much better job then me! (ps thanks again for 'donating' that PF to the project!)

Henry

Hi henry,
I hope your health is better!
At the moment I am a couple weeks behind on custom work and have too many projects to try it. Your solution works and others will benefit when they try it. Maybe my pet project will use some of your Idea!
thanks from all of us!
sincerely
Richard

Hi Richard, my health is very good, thanks, which I think has more to do with being on vacation then anything else

I'd love to hear from anybody about directions to go with this project from here... on the list is an OPV, a 3-way group, a SS kettle, and getting the equipment together to do some of the temp testing that people have done on other temp-stable machines (like Jeff did on the PID'd Alexia).

About the 'package,' I'm thinking marble sides to replace the wood, then a single sheet of SS wrapping around from the group to the back of the machine. I still don't know where to put the temp management equipment, or whether to keep the pump and reservoir separate from the rest of the machine. . .

. . . but for now she is sitting there making great espresso!

Henry

other than bodging convenience, is there any reason you've used plastic tubing instead of a more thermally conductive metal tubing?

Good call. I'd never looked up the numbers before, turns out nylon is way lower then any kind of common metal (.25 vs 46 for steel and 401 for copper). I made the choice basically for convenience, but copper tubing (ID?) would be a good choice for the next one. I can't think of any reason why I would want a lower conductivity...

I don't think it is an issue with this model, because it takes 15+ minutes to warm up the 2.5 liters of water and without a 3 way valve I have to wait a long time between shots anyway. However, I'd like to be able to use a smaller kettle and make shots faster, so copper tubing would be a better choice.

Any thoughts on TC placement? Right now it is in a steel sheath coming in from the top, about 5cm away from the element and off to one side (ie not directly above the element). If I recall correctly, the displayed temperature has not fallen during a shot...

Henry

hbuchtel wrote:... it takes 15+ minutes to warm up the 2.5 liters of water ... I'd like to be able to use a smaller kettle and make shots faster, so copper tubing would be a better choice.

Any thoughts on TC placement? Right now it is in a steel sheath coming in from the top, about 5cm away from the element and off to one side (ie not directly above the element). If I recall correctly, the displayed temperature has not fallen during a shot...

Bravo, Henry.

With the current 2.5L kettle, how much time is required to raise or lower brew temp 2 degrees?

Can you divide the kettle into cubic regions and sample the temperature for each, to get a sense of how much temperature variation there might be within the kettle? Shooting from the hip, I'd place the TC closest to where the brew water enters the group.

Regards
Timo

timo888 wrote:Bravo, Henry.

With the current 2.5L kettle, how much time is required to raise or lower brew temp 2 degrees?

Can you divide the kettle into cubic regions and sample the temperature for each, to get a sense of how much temperature variation there might be within the kettle? Shooting from the hip, I'd place the TC closest to where the brew water enters the group.

Regards
Timo

Hi Timo! I think what I could do is put a couple of the TC sheaths at various points in the kettle, then drop the TC in one at a time. I'm not really sure what I should be looking for, but it would be good to just collect some more information.

Unfortunately I'll be traveling for the next 2 weeks, so I'll have to leave it as it is for now. French press for 2 weeks!

Henry

EDIT Sorry, forgot to answer your question about changing the temp. I just tried it, and it took a bizarre 8 minutes to get from 100 to 102C. I think this has less to do with the amount of water and more to do with my PID, which I assume was programmed to control industrial equipment... which might explain why it was being so cautious.