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  1. #31
    Join Date
    Sep 2012
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    North Yorkshire UK
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    I know Bob, use some translucent tube and put some coloured LEDs in the bottom, a few strips of reflective tape on the spindle and you have a light show. Should look good in a dark cupboard...
    Best Regards:
    Baron J.

  2. #32
    BobL is online now Member: Blue and white apron brigade
    Join Date
    Feb 2006
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    Perth
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    As suggested by BJ.

    from a piece of olycarbonate 1mm thick scrap sheet.
    Pumpscreen2.JPG

    I also found some beaut 10mm ID, 1mm wall, SS tube and turned the bits all to the same length and used it as a more accurate way of aligning the pump and motor and this helped reduced the vibe a bit more.
    Pumpscreen1.JPG

  3. #33
    Join Date
    Sep 2012
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    North Yorkshire UK
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    Hi Bob,

    I like that clear 1 mm sheet tube that you have made ! Much better than leaving it open and exposed, dropping a cloth or something on that rotating shaft could cause problems. Those tubular spacers are a much better way of lining the two surfaces up as well. You now can guarantee that the plates are parallel to each other.

    Nice to know that the vibration has reduced. What little is left could be the coupler itself.

    PS. You know that my suggestion about the LED's was not a serious one
    Best Regards:
    Baron J.

  4. #34
    BobL is online now Member: Blue and white apron brigade
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    I finally got back to this project and was for a few days stuck on why nothing was working.

    I hooked up the VFD and a water supply to the motor/pump and the first obvious thing is that water flows straight through this pump but of course it's a pressure addition pump.

    Then, changing the speed of the motor didn't change the pressure much, and hardly changed the flow rate at all.
    Varying the VFD from 30 to 70 Hz only changed the pump pressure by ~15% and the flow rate changed by <5%

    After wondering what was going on, it struck me that of course, this is EXACTLY how these pumps are supposed to work so that if someone flushes the loo or turns on a HWS etc which can change the incoming water pressure which will throw the pump pressure out as it's a P-adder pump. But I don't need this as I already have a highly regulated water supply - what I want to be able to do is control P&F with the VFD.

    Opening up the press regulation mechanism I could see how it worked.
    Plunger P sits in a passage connecting the pump outlet back to inlet.
    Spring Sp supplies a back pressure to seal P inside the passage at the outlet end with the tension of the spring determined by screw S position.
    As the pump pressure builds up, once the pressure starts to overcome the spring tension this opens up the passage from the outlet water back to the inlet.
    Final flow is limited by any pump outlet restriction but if that is fixed it will maintain a fixed flow at a fixed pressure.
    springrep.JPG

    To get around this I replaced the 7mm diameter x 19 mm long screw with turned brass cylinder C, the length off C is adjustable by a short screw on the end.

    Then here is the testing setup
    I = incoming water
    WR - water regulator set at 4bar
    IWP = gauge shows input water pressure
    P = pump
    OWP = gauge showing putt water pressure
    NV = Needle valve to supply a back pressure
    V = VFD

    All I did was set the motor speed and record the OWP and measured the amount of water delivered by the pump by catching the water stream into a container for a set time period.

    Setup.JPG

    Replacing the the spring with the brass cylinder effectively removes/decouples automatic pump pressure/flow control enabling these now to be controlled by the VFD.

    Below you can see with the VFD ranging from 30 to 70 Hz the pump output pressure more than doubles (+122%) while flow increases by ~70%

    This means a barista can now control P & F even during a shot/extraction depending on their specific requirements.
    P&Flow.jpg

    Some more testing to do to determine the optimum position of the length screw on the brass cylinder.

    I have spoken to SWMBO about giving up some valuable kitchen cupboard space to accomodate said pump and she was surprisingly positive about it!
    Attached Images Attached Images

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