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How adjusting my brew pressure fixed everything

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  • gonzo89
    replied
    Yes Mal that is correct I adjust it via the valve on the rotary. Got to love the simplicity of just reaching under the machine to make the adjustment :thumbup:

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  • TC
    replied
    Originally posted by MrJack View Post
    Same thing really. An OPV is a bypass pressure control valve external to the pump.
    Yes- the distinction in a rotary pump machine is that the bypass is normally set to a nominal 9Bar whereas you set the expansion valve to 12 bar- to protect in the case of a faulty bypass. Rocket Espresso actually do it with the vibe pump Giotto PID as well.
    Last edited by TC; 22 April 2016, 08:09 PM.

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  • Yelta
    replied
    Originally posted by gonzo89 View Post
    Hi Yelta,

    I personally think the Galatea was much prettier although some won't agree.. My reason was that I wanted a dual boiler with PID.. I like to fiddle with temperature as a variable.
    Also, my partner likes lattes so I have the option of turning the steam boiler on and off depending on whether or not I am brewing for her.

    Call me crazy I guess
    Cheers
    Al
    Thanks for the explanation Al, yep I agree the cosmetics of the Galatea ain't to everyone's taste.

    They certainly are an easy machine to get good results with.

    Pleased to hear you have R58 sorted out.

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  • gonzo89
    replied
    Originally posted by Yelta View Post
    G'Day Gonzo, you say in your OP "My previous machine (Bezzera D Galatea) gave me beautiful looking shots with the naked pf every time and without the need for an elaborate dosing routine." the first question that comes to my mind is, why did you change from the Bezzera to an R58?
    Hi Yelta,

    I personally think the Galatea was much prettier although some won't agree.. My reason was that I wanted a dual boiler with PID.. I like to fiddle with temperature as a variable.
    Also, my partner likes lattes so I have the option of turning the steam boiler on and off depending on whether or not I am brewing for her.

    Call me crazy I guess
    Cheers
    Al

    Leave a comment:


  • gonzo89
    replied
    Originally posted by Talk_Coffee View Post
    Good stuff Gonzo.

    Just keep in mind the influence of an assumption on which your experimentation was based.

    Happy experimenting...

    Chris
    Hi Chris,

    That is something I failed to mention in my initial post and I wish to reiterate that yes I in no way can tell if what I am measuring is accurate.

    What I can take from the experiments is that even without an accurate reading of the brew pressure, I am going by taste and what seems to be working a lot better and I am quite pleased with the results. I have a sneaking suspicion that my tinkering has simply led to an optimal calibration without any certainty of what it is truly set at since the gauge cannot be relied upon for pin point accuarcy.

    The machine was serviced once and it was after that service I read on the receipt that they had recalibrated the pressure to 8bar. I didn't ask (I should have) if that was done properly or by looking at the gauge.. I now suspect it wasn't done properly.

    Thanks Chris
    Al

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  • Dimal
    replied
    Yep, realise that Mr.Jack but it might cause confusion for people who don't realise this...

    Mal.

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  • MrJack
    replied
    Same thing really. An OPV is a bypass pressure control valve external to the pump.

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  • Dimal
    replied
    Also, doesn't the R58 use a Rotary Pump, not a Vibe Pump?

    That being the case, wouldn't you then use the Bypass Valve mounted on the pump itself to adjust the delivered brew pressure?

    Mal.

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  • TC
    replied
    Good stuff Gonzo.

    Just keep in mind the influence of an assumption on which your experimentation was based.

    In the bench test which would have occurred at the importer before your machine shipped to the place of purchase, your machine would have been set to 9Bar via Scace device and that may well have delivered a gauge reading of 8Bar. System pressure gauges are notoriously inaccurate, so in all likelihood you actually started with 9Bar.

    Happy experimenting...

    Chris

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  • Yelta
    replied
    G'Day Gonzo, you say in your OP "My previous machine (Bezzera D Galatea) gave me beautiful looking shots with the naked pf every time and without the need for an elaborate dosing routine." the first question that comes to my mind is, why did you change from the Bezzera to an R58?

    Leave a comment:


  • gonzo89
    replied
    Although I have read a bit on the topic over the years I still haven't come to understand it in depth but yes what you are saying makes sense. I figured it may be a little too soon to see how this holds up with a variety of beans. After some additional tests today my current set of variables have been tested.

    The 3 different beans I was using at first all behaved in a similar manner (coincidence I guess). So I thought the courser setting might be there to stay with a wide range of beans. I ran through a Nicaraguan bean today (note: only 2 days post roast) and it brought my grinder setting back to where I was originally, 5 bars finer and I had to increase the dose to 22g.

    This hasn't been a problem though for 2 reasons:
    - the result in the cup is still excellent. A well balanced shot. I played with the PID a little to give me the taste I wanted.
    -I still did not require wdt and the extraction is even and pretty

    I will have to wait and see if I return to a coarser setting with different beans as I am stocked up for a few more days. I am keen to see how it holds up.

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  • MrJack
    replied
    It is odd.
    The pressure comes from resistance (pressure drop) over the puck, which increases with flowrate and decreases with (increasing) grind size. So coarser grind should allow greater flow before reaching a higher pressure.
    The OPV operates by providing an alternate flowpath once the pressure reaches the setpoint - diverting additional flow away from the puck, and thus limiting pressure drop across it.

    However, if the additional flow is greater than that the OPV capacity at that pressure (that is to say if the pressure drop in the OPV flow path is greater than 8 bar), the flowrate will increase through the puck (raising the pressure).

    So perhaps a bigger OPV might have made a difference, even at the lower pressure? (I.e. flowrate is still the key variable, pressure being more of an issue w.r.t machine function).

    Just speculating here btw...

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  • gonzo89
    replied
    Hi MrJack,
    Yes I believe you raise an important point about the OPV.
    I know I have changed the flow rate but I did not expect to be grinding that much courser. Most importantly though. With the courser grind I'm getting much more rounded shots but with just the right amount of enjoyable acidity in the shot. I'm not claiming to have done something original, just a story about how my tinkering led to a greater quality shot altogether and if anybody can add their expertise to the outcome by all means do

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  • MrJack
    replied
    Something seems a bit odd here - you are grinding coarser, to achieve a higher pressure drop at a lower flowrate?

    I'm wondering if the capacity of the OPV was somehow coming into play (at lower pressures, the pump will flow at higher rates)?

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  • gonzo89
    replied
    Thanks iggs. I learned to deal with it because it gave me the result I was after. I guess I got jealous of all of you not requiring it at all

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