Alchemist wrote:You devil

I disagree with this. I may run through the compression numbers and give a theorectical distance/volume the water will go up the tube, but note I say water. The piston head is only going to see water until the very end of the stroke, and then, even if a touch of oil/water makes it up the tube, it will be the first expelled when the air column expands again.

As for cleaning, look at the hole I have drilled. Ain't no brush going to make it up the hole.

But this is an experiment, and field testing should prove out....

Judging from the relatively small amount of coffeeoil-crud and sediment that found its way into my Caravel's hollow piston, I don't think the problem will be a big one, but it would have to be part of the cleaning regimen. I have found ultra thin brushes in a surgical parts catalog that are used to clean out very small flexi-tubes. Not inexpensive, but would do the trick if necessary. Maybe even a pipe-cleaner would do.

Regards
Timo

Well, houston, we have lift off.

I can hardly believe it. It works, first run out, no leaks, no problems.

The first thing I have to report is it is impossible (for me) to get a full pressure shot and get a picture at the same time. I will have to inlist some local help for that. Les? Mogo? Anyone else?

That said, I tried a few blind shots just to get my base line of the machine. I covered the gauge and just pulled shots until I was comfortable. It pulls real similar (go figure) to my Gaggia.

Once I had what I have been thinking of as 9 bars, I pulled the cover off the gauge, set, loaded, locked, closed my eyes and started the pull. Once into the pull and where I thought I should be I pulled off the cover (quick a trick while pull and holding steady). 130-135 psig. Very nice. basically right on target. Nice to know.

A couple more pulls and I can verify that i am pulling pretty consistently at 130 and all the way through the pull. But wow, that gauge does jump around. I probably have a 5-10 psi quiver.

Here are a few shot shots. They are

1) Before the shot
2) loaded with just boiler pressure
3) Somewhere in the shot
4) During the pull with as much pressure as I could exert without the machine slipping.

At some point I want to set up the video camera too for a live pull.









Oh, and for those who don't have it off the top of their head, 1 atm = 14.7 psi, 9 atm = 132.2 psi. Oh, and I see my converter says bar does not quite equat atm. 9 bar = 130.5 psi.

Alchemist wrote:Well, houston, we have lift off.I can hardly believe it. It works, first run out, no leaks, no problems.
...snips and clips...
Once I had what I have been thinking of as 9 bars, I pulled the cover off the gauge, set, loaded, locked, closed my eyes and started the pull. Once into the pull and where I thought I should be I pulled off the cover (quick a trick while pull and holding steady). 130-135 psig. Very nice. basically right on target. Nice to know.

I am totally pleased that you have proven the concept!
Thanks
richard / espressme

Congratulations on a great mod. Especially with no leaks on the first assembly and use. cool.

Pretty amazing that the pull you were using was around the recommended, but I guess this makes sense.

Interesting results, when you said you pulled until the machine slipped do you mean the base moving on the table surface or the gaskets slipping in the grouphead?

Live movie pull would be interesting too. Probably easier than taking pictures while pulling a shot.

happytamper wrote:Pretty amazing that the pull you were using was around the recommended, but I guess this makes sense.

Interesting results, when you said you pulled until the machine slipped do you mean the base moving on the table surface or the gaskets slipping in the grouphead?

The base moved and the machine tried to tip at 130 psi.

Annoying (as we all know) that quite a lot of the levers out there need two hands to pull do to stability issues.

Oh, I will report on an observation. There is on hell of a seeze, but I don't know if that is due to the mod or the new seals or just the nature of the LP. Mitch? Did you pull shots with the new seals?

And I don't find it quite as amazing that i was at 9 bar so much as I have a sucessful mod that will allow some profiling and experimentation. I will give a hat's off to Timo. Apparently my muscle memory (trained two times on a bath room scale) was sufficient. I would be interested none-the-less to see how other people pull on it.

Alchemist wrote:The base moved and the machine tried to tip at 130 psi.

Annoying (as we all know) that quite a lot of the levers out there need two hands to pull do to stability issues.

Oh, I will report on an observation. There is on hell of a seeze, but I don't know if that is due to the mod or the new seals or just the nature of the LP. Mitch? Did you pull shots with the new seals?

And I don't find it quite as amazing that i was at 9 bar so much as I have a sucessful mod that will allow some profiling and experimentation. I will give a hat's off to Timo. Apparently my muscle memory (trained two times on a bath room scale) was sufficient. I would be interested none-the-less to see how other people pull on it.

Hi Alchemist

I am pretty sure that most pavonis have a slight sneeze when removing the portafilter, mostly when the portafilter is removed right after the pour. Perhaps some compressed air in the gauge path could increase the sneeze potential. I used the Pavoni with the new seals for about two months.

As for the base issue, here is a comparison to the La peppina, i have been using my La Pepinna for the last few days and not only is the moving base an issue, there is a possibility of tipping the machine. For the Pavoni the moving base issue is only a nuisance, for the La Peppina it is a downright danger. If I continue to use the La Peppina I will either modify the base or bolt it to my counter. And I will absolutely continue to use it since it prepares great espresso, somewhat different from the pavonis. excuse the off topic stuff. Wonder what Timo has to say about safety and the La Peppina.

Look forward to seeing some interesting experimention.

happytamper wrote:... wonder what Timo has to say about safety and the La Peppina.

I don't know what the worse threat is ... boiling water or electric shock. I always keep my left hand on the PF handle while I pull the lever, and she's pretty stable then. Don't wipe any spills from your Peppina while she's drawing power.

A while ago, Richard mentioned an outlet modification that would prevent serious electric shock.

espressme wrote:... we are enjoying vintage machines now and therefore having a GFI socket may be a life saver. ..that type of socket should be in all kitchen / bathroom counter outlet boxes. It trips the breaker instantly as soon as any Voltage/current change is detected in reference to ground ie. a short circuit! And, it may be installed in any duplex outlet box using the existing wiring.

Regards
Timo

Alchemist wrote:I don't find it quite as amazing that i was at 9 bar so much as I have a sucessful mod that will allow some profiling and experimentation.

I am very impressed, Alchemist, that your "quiver" was less than 1 bar.

Regards
Timo

timo888 wrote:I am very impressed, Alchemist, that your "quiver" was less than 1 bar.

Regards
Timo

Thanks. er, um, I think

OK, here is a first bit of "real" data. Called out data as someone transcribed for me. Something kind of really intersting fell out. This is one of my "standard" constant pressure pulls. To the best of my knowledge and ability, that was a constant force I applied, but the resulting puck pressure is anything but. Target pressure, dip, and return of target. I saw this a number of times. And if it is not clear, those first pulls in the negative zone are preinfusion - basically hand weight. And the end is just that - the end of the stroke.

I have wondered about that dip for some time now, and I think it might have to do with the moving fulcrum. Thoughts? On some different pulls, in order to keep a constant puck pressure, I really had to exert myself in the middle of the pull.

Alchemist wrote: On some different pulls, in order to keep a constant puck pressure, I really had to exert myself in the middle of the pull.

image: http://www.home-barista.com/forums/userpix/661_pullgraph1_1.jpg

I think you should be happy with this profile.

The sag in the middle could be the result of increased flow through the puck. As flow increases, pressure descreases. As the puck expands from hydrostatic pressure mid-shot, and flow decreases, the pressure would return. This jibes with your statement that you really had to exert yourself mid-pull.

To test out this theory, try a long preinfusion (say 20 seconds) to give the puck a good time to swell, and then try a pull. Pressure shouldn't sag midway. You may have to grind more coarsely to prevent a stall, and give yourself at least 6mm headroom for expansion.

Regards
Timo