First ever lever pull pressure mod

[Alchemist]

Well, I think it is a first. Back in the thread "Peppina Marries MiniGaggia" there was a brief discussion of attaching a pressure gauge to the piston to monitor the pull pressure. Disregarding the spirited discussion about the necessity , Happy Tamper offered to send me his lever machine to "play" with and modify if I could.

I am going to outline just what I did, step by step, should anyone else want to follow in our footsteps, but I will start off this thread with a Final photo.

In addition, the whole point of this exercise, I want to experiment and document how pull pressure profiles affect the shot. Are isocratic best, does a decay work best, are we actually at 9 bar? That whole thing. Real data

It is not quite finished, but is very close. While I have people here, I wanted some advice before final assembly. The machine has been apart for a couple months now. Upon test fitting everything, I notice the lever gaskets are very tight in the group head. Should I lubricate them. They are fine and pliable. I would prefer not to have to get lubrication just for this little job if it can do without it, but also don't want to have to break some locktight to add lubrication should there be leaks due to lack of lub. Anyone care to give me some experience based advice?






Disregard the nail as lever pin - I left the pin at work. Sigh - almost done.

[mogogear]

"Pay no attention to the man behind the curtain"

So John, it appears you have bored down through the piston shaft!! Good for you. That scale on the gauge looks like you will have the upper reaches of force covered. I am so relieved to know you have not been whiling away your time hoping to turn cocoa beans in to gold.... I can't wait to see how the pressure ramps up

[happytamper]

Hi John,

The mod looks super cool, a first in espresso history. Lots of gauges all over the place.

I am glad my old brass Ambassador made the international trip to help in this process. Looks like alot of new coffee data for lever enthusiasts is now a possibility.

Willi Wonkas chocolate factory has now expanded to coffee.

As for the Lubrication. The gaskets are relatively new so they may be a bit tight. It is always good to have some though I find it disapears with time and the water becomes the lubrication so lube is not absolutely necessary, or at least this is what happened with my Europiccola.

Look forward to seeing all the experiments.

All the best,

Mitch

[Alchemist]

Hi John,
As for the Lubrication. The gaskets are relatively new so they may be a bit tight. It is always good to have some though I find it disapears with time and the water becomes the lubrication so lube is not absolutely necessary, or at least this is what happened with my Europiccola.

OK, then if there is no counter suggestions, I will not worry about additional lubrication. It went together fine.

And right you are Mogo, hole through the center - but it was not nearly that simple. More of that later....

[espressme]

OK, then if there is no counter suggestions, I will not worry about additional lubrication. It went together fine.

And right you are Mogo, hole through the center - but it was not nearly that simple. More of that later....

Hello Alky,
Congratulations! You did the almost impossible! I found a photo a while ago of one of the rip-off machines with a gauge as you have it.
I'd love to know how you solved it!
Best Reagrds to All,
Sincerely
Richard / Espressme

[bobcraige]

How do you expect the purge the air from the gauge path?

[Alchemist]

How do you expect the purge the air from the gauge path?

Either it will work with an air in the path (pressure is pressure after all), or should I find it does not work for what ever reason, the gauge could be loosened to purge the air.

The pathway is very small, built to accommodate air. I doubt there is a ml all told. I expect some compression, but again, pressure is pressure, and the water should be re-expelled after the shot should some compress up the pathway.

[hbuchtel]

When there is a gauge measuring boiler pressure there is certainly air in the system . . . why would it be a problem?

EDIT: re-reading this thread I realized above sentence doesn't make much sense, what I meant is gauges that measure boiler pressure (such as the one on the end of the sight glass on the G. Factory) measure accurately in spite of there being air in the boiler, so why would a gauge measuring brew pressure require that the air is purged?

Will John have to release 'false pressure' as it warms up?

Henry

[happytamper]

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.

[espressme]

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.

you sirrah have a wicked mind. And, unfortunately have me thinking!!
Enjoy
Richard espressme

[timo888]

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

[Alchemist]

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]

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.

[timo888]

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

[happytamper]

Hey Timo,

I would have liked to see the pharmacists face.

[espressme]

(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

[j7on]

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.

[Alchemist]

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

[timo888]

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."

[Alchemist]

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....