happytamper wrote:Seems to me, from my engineering days, air will always stay at the top. Especially if we are letting a short preinfusion occur.

I wonder what pressure we will see on our pulls with this apparatus in place. I will bet some of us are pulling at 20 bars and others at 6.

Maybe this machine should do a tour, to get a larger sampling of lever practises. Or as a training tool. However I am excited to get my brass beauty back to Montreal for a while, Of course only after all our Alchemist has exhausted all testing and has had a thoroughly good time with it.

Now we have to invent a sieve for measuring the varying degrees of grind.

Brew pressure varies, but it would take Schwarzenegerrian strength to reach 20 bars on a ~50mm piston with a lever of typical length and the typical distance between pins. I suspect the o-rings would pop well before that point.

Regards
Timo

timo888 wrote:Brew pressure varies, but it would take Schwarzenegerrian strength to reach 20 bars on a ~50mm piston with a lever of typical length and the typical distance between pins. I suspect the o-rings would pop well before that point.

Regards
Timo

I agree that either o rings or something else would give way before reaching 20 bar, but it's only about 100 lbs of force on the lever. Not really all that much IMO.

Well, it is all put together, minus the lever piston pin, that I have somehow misplaced it and of course, it is non-standard size. I am going to machine a new one today.

Richard, I will post some photos today, but I solved the piston through way by drilling a 4 mm whole straight through. I then enlarged the piston pivot hole so it would accept a new sleeve. The sleeve had a groove machined around the center outside to allow passage of air. The sleeve was then silver soldered in the new pivot hole. The result was a piston that allows the passage of air, but not light (the pivot sleeve blocks it).

Alchemist wrote:Richard, I will post some photos today, but I solved the piston through way by drilling a 4 mm whole straight through. I then enlarged the piston pivot hole so it would accept a new sleeve. The sleeve had a groove machined around the center outside to allow passage of air. The sleeve was then silver soldered in the new pivot hole. The result was a piston that allows the passage of air, but not light (the pivot sleeve blocks it).

Rotten photo, but here is the piston as I received it.



I drilled out the pivot hole to make room for the sleeve on the left. The sleeve does not have it's bypass groove



Actually, I just photoshopped the photo above a little to give you an idea of what the sleeve looked like. Those are the same sleeve. It is a little exaggerated to show what I mean. It was much shallower.



Here is the new sleeve all inserted and soldered in.



And the hole all the way through. That was really "fun". Took using a lathe, and going very slowly. Any other way and the bit wanted to wander. Finally, I put a small 1/8" hole in the (hrm, not sure whet it is called) "bottom".




There you go. That was how the throughway way put into the piston. More later.

Alchemist wrote:There you go. That was how the throughway way put into the piston. More later.

Ingenuity begets ingenuity.... though maybe begets is the wrong word, considering this suggestion: if you place a condom over the piston head, you can prevent coffee grounds from getting into the conduit, and you should still be able to measure the brew pressure (though it might not be as much fun). The pharmacist gave me a weird look when I asked if he had any prophylactics that could withstand boiling water temperatures. For this feature I do think you will need some Dow 111.

Regards
Timo

Hey Timo,

I would have liked to see the pharmacists face.

Alchemist wrote:

Alchemist wrote:(many snips)
Richard, I will post some photos today, but I solved the piston through way by drilling a 4 mm whole straight through. I then enlarged the piston pivot hole so it would accept a new sleeve. The sleeve had a groove machined around the center outside to allow passage of air. The sleeve was then silver soldered in the new pivot hole. The result was a piston that allows the passage of air, but not light (the pivot sleeve blocks it).

Rotten photo, but here is the piston as I received it.
I drilled out the pivot hole to make room for the sleeve on the left. The sleeve does not have it's bypass groove
Actually, I just photoshopped the photo above a little to give you an idea of what the sleeve looked like. Those are the same sleeve. It is a little exaggerated to show what I mean. It was much shallower.
Here is the new sleeve all inserted and soldered in.
And the hole all the way through. That was really "fun". Took using a lathe, and going very slowly. Any other way and the bit wanted to wander. Finally, I put a small 1/8" hole in the (hrm, not sure whet it is called) "bottom".
There you go. That was how the throughway way put into the piston. More later.

Alchemist,
My hat and shop apron are off to you!8) The safety glasses stay on!
A very neat job and elegant solution!:!: The precompressed air Blows the crud out when brew pressure is released!
"Iligitimi non carborundum"
Thanks
Richard / espressme

I always planned on going in through the side, above the showerscreen.

Yeah, the gauge would stop showing pressure as it goes into the screens basket but you would have a reading when you are starting to pull which would be easy to follow through.



If i have time, i think i am still going with this.

j7on wrote:I always planned on going in through the side, above the showerscreen.

Yeah, the gauge would stop showing pressure as it goes into the screens basket but you would have a reading when you are starting to pull which would be easy to follow through.



If i have time, i think i am still going with this.

I considered this approach, but you would have to machine the gauge end to fit the curve of the wall exactly or you are going to blow through gaskets as it rubs and abrades each pull. I have heard this approach before, but I just don't think it would work or would be too much work. YMMV

espressme wrote:Alchemist,
My hat and shop apron are off to you!8) The safety glasses stay on!
A very neat job and elegant solution!:!: The precompressed air Blows the crud out when brew pressure is released!
"Iligitimi non carborundum"
Thanks
Richard / espressme

I prefer to think of it as the role of Devil's Advocate, Richard, not bastard.

With the piston downstroke, the air inside the tube will compress and a water-coffeeoils emulsion will go up into the tube some distance. (Version in miniature of the All-Clad Presso air-in-piston issue ) The more you press, the more the air will compress, until it reaches the point where it's easier for water to exit through the puck than to compress the air in the tube. The good thing is that the oils will passivate the raw metal. The bad thing is that they may eventually produce some unpleasant flavors. Scrubbing the tube with a pipe-cleaner or surgical-supply narrow-tube brush should be made part of the regular cleaning regimen.

Regards
Timo
---------
"More dentists recommend Crest® than any other oral dentrifrice."

timo888 wrote:I prefer to think of it as the role of Devil's Advocate, Richard, not bastard.

With the piston downstroke, the air inside the tube will compress and a water-coffeeoils emulsion will go up into the tube some distance. (Version in miniature of the All-Clad Presso air-in-piston issue ) The more you press, the more the air will compress, until it reaches the point where it's easier for water to exit through the puck than to compress the air in the tube. The good thing is that the oils will passivate the raw metal. The bad thing is that they may eventually produce some unpleasant flavors. Scrubbing the tube with a pipe-cleaner or surgical-supply narrow-tube brush should be made part of the regular cleaning regimen.

Regards
Timo
---------
"More dentists recommend Crest® than any other oral dentrifrice."

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....