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  • KJM
    replied
    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

    Leave a comment:


  • MrJack
    replied
    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?

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  • Javaphile
    replied
    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

    Leave a comment:


  • Portaspresso
    replied
    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?

    Leave a comment:


  • gonzob
    replied
    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

    Leave a comment:


  • Javaphile
    replied
    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

    Leave a comment:


  • KJM
    replied
    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

    Leave a comment:


  • Portaspresso
    replied
    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.

    Leave a comment:


  • LaughingAtFate
    replied
    Re: Pressure and flow

    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?

    Perhaps this is another reason why Boilers are Better? ;D

    Leave a comment:


  • KJM
    replied
    Re: Pressure and flow

    OK - Ross - there isnt going to be any measurements. High speed pressure transducers are basically outside my ability to fund.

    The fastest (affordable) transducers have response times of 10mSec. To look at the pressure waves in the fluid you need to resolve a bit better than that - youre looking at primary waveforms of 20mSec and I suspect you want to look for harmonics at higher frequencies...

    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.

    I do hate it when the bleeding obvious gets pointed out! :-[. Darn - I knew that too!

    Assuming the espresso machine designers were on the ball, this will nicely filter the pressure fluctuations down to vanishingly small. It will certainly take out 50Hz (they said, after the second espresso and without measuring anything...).

    This would also explain why there is no discernible difference in the taste from a vibe pump or a rotary in blind tasting.

    /Kevin

    Leave a comment:


  • KJM
    replied
    Re: Pressure and flow

    Originally posted by 675845435644474552444458370 link=1327651715/26#26 date=1328497399
    This would make for an interesting experiment. Let me know if you end up doing it.
    I actually had a snarf around the labs for some pressure transducers. We have some at work, but theyre rather excessively humongously large.. The liquid ones I have access to also suffer from the problem of having a 38mm (1 1/2") BSP thread that the liquid goes in So Im out on a limb unless I go buy one myself. Which I might do yet, just out of prurient interest.

    /Kevin

    Leave a comment:


  • Portaspresso
    replied
    Re: Pressure and flow

    Originally posted by 5D55544055583A0 link=1327651715/24#24 date=1328251749
    And I thought it was going to be pretty straightforward....
    Hi Gonzo,

    I personally think it is quite simple, but we seem to make it very complex. With the right equipment, following a few simple principles will result in great coffee. Reaching the pointy end of quality takes a bit more care and attention, but it is certainly not out of reach.

    In relation to the suggestions outline above, experimentation is king. Testing different baskets could prove difficult, but you should be able to figure something out. Temperature and water contact time should be easier.

    I see further potential for your idea if you can design it to control all the applicable variables. The great aspect of manual operation is the ability to control those variables to a much higher level than the majority of conventional machines. I look forward to seeing further revisions.

    Originally posted by 7170773A0 link=1327651715/25#25 date=1328266219
    The pump will oscillate at the mains frequency so youll see a 50Hz (or 100, depending on the action of the pump) pressure fluctuation..
    Hi Kevin,

    This would make for an interesting experiment. Let me know if you end up doing it.

    Cheers,
    Ross

    Leave a comment:


  • KJM
    replied
    Re: Pressure and flow

    Originally posted by 4D45445045482A0 link=1327651715/24#24 date=1328251749
    And I thought it was going to be pretty straightforward....
    Coffee? Straight forward? Doesnt it famously have 2+2=5 in here somewhere :

    Originally posted by 7A45585E4B595A584F5959452A0 link=1327651715/23#23 date=1328248578
    Electrical frequency is not the issue, its the mechanical vibration
    No - that was my point. The pump will oscillate at the mains frequency so youll see a 50Hz (or 100, depending on the action of the pump) pressure fluctuation..

    /Kevin

    Leave a comment:


  • gonzob
    replied
    Re: Pressure and flow

    Originally posted by 023D2026332122203721213D520 link=1327651715/21#21 date=1328235343
    Based on my experience, pumping your presso more than once will destroy your shot. The pressure ramp-up profile should be as smooth as possible. It can be a steep climb or flatter, but it needs to be smooth. Even very small fluctuations will totally destroy your shot. You can pause half way through the build-up, but dont fluctuate the pressure.

    Yes, Ive noticed, and others have commented that, with a standard Presso, if you "have another go" with the levers it stuffs it.

    However, with my Pneu-presso I can hold the pressure very well. My videos show the machine in its infancy and when I was still new to it. Since then Ive fixed a few leaks and learned to use it, and I can now ramp it up, to say 2 bar, hold it there for a bit, then ramp it up to 6 bar, and hold it there. The shot volume with my machine is not limited by the stroke of the levers.

    I digress. The issue here is that theres a big difference between machines with the same grind. KJM has pointed out that the shape of the basket is a big variable (and maybe the perforations...). Zaneus says temperature is a big player. Now Ross says the pre-infusion makes the world of difference. All back up their ideas with experience and logic.

    And I thought it was going to be pretty straightforward....

    Gonzo

    Leave a comment:


  • Portaspresso
    replied
    Re: Pressure and flow

    Originally posted by 68696E230 link=1327651715/22#22 date=1328239884
    Ross: do you have some data on this already?
    Electrical frequency is not the issue, its the mechanical vibration quite noticeable on many domestic and semi-commercial machines caused by pump design. Machines fitted with good rotary pumps would not noticeably suffer from this issue. I tend to think that if you can feel the pump working by placing your hand on the machine during extraction, there would be some level of pulsation through the water, which in my opinion could influence extraction.

    The data is inferential, but Im sure it wouldnt be too difficult for someone with the time and motivation to setup and record the pulsation or pressure fluctuation (I wont say frequency so that no-one confuses it with that associated with electricity).

    When I first made the Rossa, the quality of extraction made with it was dramatically better and smoother than my Bezzera. This certainly got the mind going to figure out why. The Bezzeras pump is what I consider quite rough, and I always wondered what effect it had on extraction, but was unable to test it. Once I made the Rossa, I was able to replicate the Bezzeras profile, but without the rough pump. I believed that I isolated the pump fluctuation enough for comparison, but one can never be sure. I have since made similar comparisons with many machines, and it seems that the smoother the pump, the more closer the shots are to the Rossa (and I imagine a lever machine; need to keep it objective!). The differences are noticeable both visually and by taste.

    Ive also replicated a type of pulsation fluctuation with the Rossa, and the results start to resemble that of the Bezzera (and other similar machines). Of course there could be other variables at play, but Im quite sure that the slight pressure fluctuations make a noticeable difference (to me anyway). That said, maybe few people can taste a difference. Until I knew better, I thought my old machine was great. Everything is relative!

    Originally posted by 68696E230 link=1327651715/22#22 date=1328239884
    The actual hydraulics of the machine I use has the pump pushing water into a large boiler and the boiler would have headspace - and thus be quite nicely dealing with the otherwise "pulsing" nature of the pump.  Plus the OPV in the circuit will also tend to squish out some of the leading edge of the pressure pulses.
    Maybe someone else could comment on this one, as I havent looked at the Expobar, but I wouldve thought that the pump plumbing associated with the extraction circuit would go through the boiler via a heat exchanger process. Either way, the pressure fluctuation would be there and measurable, unless of course the pump is of very high quality.

    I imagine that this topic would be controversial, and really only apply to those seeking to push the limits in the pursuit of perfection.

    Leave a comment:

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