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  • #31
    Re: Pressure and flow

    Originally posted by 7B7A7D300 link=1327651715/28#28 date=1329291870
    OK - Ross - there isnt going to be any measurements.  High speed pressure transducers are basically outside my ability to fund. 
    No worries Kevin. It would have been an interested test, but my gut feel is that the electrical frequency would be too fast to have any noticeable effect anyway. Im more interested in the effects of mechanical vibration that can be felt by placing your hand on the machine during use. This effect would normally be very hard to isolate and test, but I might end up being able to test it during the R&D of another project. One of these days Id like to design a conventional electric machine (and as automated as possible) that incorporates the Rossa Hand Espressos fundamentals. If I manage to pull it off, it would certainly shake up the home espresso scene. So in the process of R&D for this project, I will be able to directly and objectively test the effects of mechanical vibration on espresso quality. If I dont die from old age before I get to do the test, Ill post the results.

    Originally posted by 6D6C6B260 link=1327651715/28#28 date=1329291870
    Having said that, however, a couple of engineers of the wet mechanical type listened patiently to my question about the pressure fluctuations and pointed out that the boiler with any headspace in it plus the group head (which would certainly have air entrained) will actually act as a low pass filter.
    This would be true for any machine that pumps directly from the boiler. Air is a great dampener, but machines that use a heat exchanger through the boiler on the line that feeds the grouphead will not have any air in the system. Any air in the line would be pumped through the coffee puck as the water comes through. My electric machine uses a heat exchanger through its boiler, and I imagine that the majority of good machines would use a similar design. As previously noted, I havent seen the internals of many machines, so maybe a more knowledgeable person could comment on the use of heat exchangers.

    Originally posted by 6A4753414E4F4841675260475243260 link=1327651715/29#29 date=1329375246
    I wonder if the pressure fluctuations are more an effect of the thermoblock type machines, which dont have the whole suppression effect of a large-ish boiler?
    Thermoblock machines have a whole bunch of issues all to themselves largely resulting from the desire to design and build a cheap espresso machine. That said, Im sure the vibration from their pumps would not be helping their cause.

    Now that would be an interesting experiment! I might even dig out and test my old Sunbeam during the pump isolation test described above. Will definitely post those results.

    Comment


    • #32
      Re: Pressure and flow

      Originally posted by 033C2127322023213620203C530 link=1327651715/30#30 date=1329391333
      No worries Kevin. It would have been an interested test, but my gut feel is that the electrical frequency would be too fast to have any noticeable effect anyway. Im more interested in the effects of mechanical vibration that can be felt by placing your hand on the machine during use. This effect would normally be very hard to isolate and test, but I might end up being able to test it during the R&D of another project. One of these days Id like to design a conventional electric machine (and as automated as possible) that incorporates the Rossa Hand Espressos fundamentals. If I manage to pull it off, it would certainly shake up the home espresso scene. So in the process of R&D for this project, I will be able to directly and objectively test the effects of mechanical vibration on espresso quality. If I dont die from old age before I get to do the test, Ill post the results
      Surprisingly - vibration is dead simple to measure! You can just grab a piezo element and attach it - then look at the output with a DSO.. A cheap piezo beeper from Jaycar for example will have the element in there with 2 convenient leads attached

      Alternatively (and not quite as responsive) - you can measure this with an Android phone 8-) There is an app in the marketplace that does this quite well...

      Neither of these cheap and cheerful techniques give you any sort of measure of the energy in absolute terms, but if youre looking at a vibrating pump you can pretty much work it out from the mass of the slug, distance moved and frequency..

      Cheers
      /Kevin

      Comment


      • #33
        Re: Pressure and flow

        Originally posted by 576875736674777562747468070 link=1327651715/30#30 date=1329391333
        Air is a great dampener, but machines that use a heat exchanger through the boiler on the line that feeds the grouphead will not have any air in the system. Any air in the line would be pumped through the coffee puck as the water comes through. My electric machine uses a heat exchanger through its boiler, and I imagine that the majority of good machines would use a similar design. As previously noted, I havent seen the internals of many machines, so maybe a more knowledgeable person could comment on the use of heat exchangers.
        Many of the commercial machines out there use what I call a Test Tube exchanger. On these models the grouphead attaches directly to near the top of the boiler. Where it attaches there is a Test Tube that sticks down into the boiler at an angle. Fresh water is injected into the test tube at its top and leaves the test tube via a pipe/tube that extends from the grouphead down to the bottom of the test tube. With the test tube being a closed system other than the inlet and outlet it does not fill up with water and so the air in it provides a good buffer against any potential surges.


        Java "Test the tube!" phile
        Toys! I must have new toys!!!

        Comment


        • #34
          Re: Pressure and flow

          Originally posted by 556A7771647675776076766A050 link=1327651715/30#30 date=1329391333
          One of these days Id like to design a conventional electric machine (and as automated as possible) that incorporates the Rossa Hand Espressos fundamentals.

          Just make a small air compressor with a "profile" controller for the pressure, remove the handle on the Rossa and replace it with a pneumatic fitting, et voila` a Pneu-Rossa.

          Gonzo

          Comment


          • #35
            Re: Pressure and flow

            Originally posted by 18191E530 link=1327651715/31#31 date=1329395071
            Surprisingly - vibration is dead simple to measure!  You can just grab a piezo element and attach it - then look at the output with a DSO..  A cheap piezo beeper from Jaycar for example will have the element in there with 2 convenient leads attached Wink

            Alternatively (and not quite as responsive) - you can measure this with an Android phone  Cool  There is an app in the marketplace that does this quite well...
            Thanks Kevin. Ill look into these options if I get to a point where I need to put some numbers against the vibration. At this stage Im more interested in determining the effect of vibration on espresso quality, which requires isolating the variable and tasting the difference. This will inevitably be a subjective measure, but I guess it will be a starting point at the very least.

            Originally posted by 19322532233B3A3F36530 link=1327651715/32#32 date=1329416259
            Many of the commercial machines out there use what I call a Test Tube exchanger. On these models the grouphead attaches directly to near the top of the boiler. Where it attaches there is a Test Tube that sticks down into the boiler at an angle. Fresh water is injected into the test tube at its top and leaves the test tube via a pipe/tube that extends from the grouphead down to the bottom of the test tube. With the test tube being a closed system other than the inlet and outlet it does not fill up with water and so the air in it provides a good buffer against any potential surges.
            That sounds like a heat exchanger with some form of air dampener incorporated; albeit a unique description. If your description is accurate, it would suggest that other designers have been confronted with the effects of vibration on espresso quality.

            What exact name and model of machine uses this system?

            Are you certain that air remains in the system during extraction? If so, would you describe the system in more detail?

            Originally posted by 343C3D293C31530 link=1327651715/33#33 date=1329423970
            Just make a small air compressor with a "profile" controller for the pressure, remove the handle on the Rossa and replace it with a pneumatic fitting, et voila` a Pneu-Rossa.
            Thanks for the idea Gonzo, but I would never encroach on another persons idea or design. Furthermore, I have no intention to complicate the Rossas simple design. I think its pretty well perfect as is!

            The machine I have in mind will not look anything like the Rossa. It will be completely different other than its ability to provide the user with total control over the variables. As Im sure people can understand, all else will remain a tad secretive for some time to come.

            In a move to redirect this thread back onto topic, did you manage to test the effects of filter basket shape, temperature and water contact time on pressure and flow?

            Comment


            • #36
              Re: Pressure and flow

              Originally posted by 69564B4D584A494B5C4A4A56390 link=1327651715/34#34 date=1329453997
              That sounds like a heat exchanger with some form of air dampener incorporated; albeit a unique description. If your description is accurate, it would suggest that other designers have been confronted with the effects of vibration on espresso quality.

              What exact name and model of machine uses this system?

              Are you certain that air remains in the system during extraction? If so, would you describe the system in more detail?
              Looking at the hydraulic circuit for my machine it appears I had the inlet/outlet from the HX reversed, which means the air pocket inside the HX tube is smaller, but it is still present. Additionally there is also some air pockets in the grouphead itself to help in the dampening.

              Cimbalis as well as I believe Faema and Pasquinis (Owned by Cimbali.) use this design in addition to Im sure others as well. Download the manual at the bottom of this post to see the hydraulic circuit used in the Cimbali machines: http://coffeesnobs.com.au/YaBB.pl?num=1247055437/14#14


              Java "Circuits R Us" phile
              Toys! I must have new toys!!!

              Comment


              • #37
                Re: Pressure and flow

                Originally posted by 6B54494F5A484B495E4848543B0 link=1327651715/30#30 date=1329391333

                This would be true for any machine that pumps directly from the boiler. Air is a great dampener, but machines that use a heat exchanger through the boiler on the line that feeds the grouphead will not have any air in the system. Any air in the line would be pumped through the coffee puck as the water comes through. My electric machine uses a heat exchanger through its boiler, and I imagine that the majority of good machines would use a similar design. As previously noted, I havent seen the internals of many machines, so maybe a more knowledgeable person could comment on the use of heat exchangers.
                I have to agree here. At 9 bar any air left at in the system (if any) is going to be either heavily compressed into a small volume, forced out with the water, or dissolved in it. Probably not going to be much damping effect. I wouldnt think there would be too many places for air to hide in there anyway (shower screen excepted)?

                The boiler is a different story though. Im presuming that the pumps are generally upstream of the boiler?

                Comment


                • #38
                  Re: Pressure and flow

                  Originally posted by 4E7149626068030 link=1327651715/36#36 date=1329532073
                  The boiler is a different story though. Im presuming that the pumps are generally upstream of the boiler?
                  Every machine Ive ever seen has the pump on the inlet side. So the pump operates on room temperature water to avoid problems.

                  Im also pretty sure the E61 head designs end up with entrained air in the top as a consequence of the way they do the pre-infusion.

                  Got to rush!
                  /Kevin

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