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Thread: WANTED: Volunteer to do a test for me, to help me calibrate my EM6910 pressure gauge

  1. #1
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    WANTED: Volunteer to do a test for me, to help me calibrate my EM6910 pressure gauge

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    I would like assistance from someone who has access to an espresso machine that can easily vary the brew pressure, and that can accept the 58mm Sunbeam Cafe Series (e.g EM6910) filter baskets. You can use your own portafilter, but it must be compatible with the Sunbeam filter baskets.

    Here is the test:

    1. Fit any Sunbeam 58mm Cafe Series DUAL-WALL(pressurised) basket to a machine that can vary the brew pressure accurately. Do not put any grinds in the basket at all.
    2. Make sure the machine is set for a constant brew pressure after any ramp-up.
    3. Start a shot, and wait for the pressure to stabilise.
    4. Once the pressure has stabilised, put a container under the portafilter and start collecting the pour, and at the same time, start a timer on a stopwatch.
    5. Time how long it takes to gather 60mL.
    6. If it is 16 seconds, report the brew pressure. (end of test)
    7. If the time is longer than 16 seconds, empty the container, increase the brew pressure, and go to step 2.
    8. If the time is shorter than 16 seconds, empty the container, reduce the brew pressure, and go to step 2.

    Greg.

  2. #2
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    Why?

    Are you trying to get a feeling of what your gauge does? Gauges vary- a heap.

    The only prosumer machine on the market which can vary the brew pressure is the Ambient&spresso Vesuvius. There are 2 of them in the country.
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    Yes - I want to get a feeling for how my gauge behaves.

    Yikes - I had no idea that it was so uncommon to be able to vary the brew pressure!

    Do you know whether that Greg Pullman pressure gauge is compatible with the EM6910's portafilter? I have two portafilters - one has a coarse thread for the spouts, and the other has a fine thread.

    EDIT: Hang on a minute - it doesn't have to be a prosumer machine - I was envisaging a PROFESSIONAL machine. I want someone who has access to ANY machine that can vary the brew pressure fairly accurately.

    Greg.

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    The other problem is pressure out of the group head does not necessarily correlate to flow. You can have the same pressure - eg 9bar - and get very different amounts of flow depending on how many, how large, and just generally how the flow restrictors in the machine are set up. Unfortunately this test will tell you nothing you can use.

    Only way achieve what you are trying to do is get a PF with a pressure gauge on it. Try this - http://coffeesnobs.com.au/brewing-eq...auge-road.html
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    Bames: I've thought about it, and I think you are incorrect. A given flow through the filter basket will produce a constant pressure in the filter basket. My test should work. (I know it's not ideal, but it would be a start)

    And yes, according to this post, Greg Pullman's pressure gauge will fit the EM6910, which is great! http://coffeesnobs.com.au/brewing-eq...tml#post409265

    Going away soon - will send the email to get in the queue for the pressure gauge in a few weeks. (I'd hate to hold others up if it arrives while I'm away)

    In the meantime, if someone can do the test, I'd really appreciate it.

    Thanks,
    Greg.

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    Bames: I think I understand what you're saying now. You're saying that the WAY the water flows through the group head and through the basket might affect the resulting pressure? I.e, if it's turbulent, or very even ("laminar"). Any idea roughly what percentage difference this could make? I'm still wondering whether the test is quite as useless as you seem to be implying though. I guess if some kind of mechanical resonance occurred, and the pressure did NOT stabilise at all, then of course it would be pretty useless, unless the average pressure could somehow be ascertained perhaps.

    Greg.

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    Just had a quick look at your other thread asking about this too.

    you said in that thread "At the moment I'm a bit puzzled, because in order to produce a 25 second shot for the double (single wall) basket), the pressure gauge has to be a fair bit higher than the centre of the recommended range." This is because without a modification like Pete suggested, you will almost definitely be getting more than 9 bar through your coffee when pulling a shot. I would estimate to get 60 ml in 25-30 seconds from the stock EM6910 single wall basket (which normally holds ~20g of coffee??) your machine will putting about 11 bar through your coffee. True story.

    The EM6910 does not have a pressure reducing valve (aka an OPV), so for example when you choke your machine (grind so fine as to get no flow), your coffee will be being hit with around 14-15bar from your 15bar vibe pump.

    On a machine like this with no OPV (and installing one would not be worth the effort - trust me I did it on an Oscar), you need to completely forget about hitting a particular pressure. Seriously. Put duct tape over the pressure gauge. I'm not even kidding.

    Instead, to get the most out of your machine, manage your grind and dose to achieve tasty espresso. Seriously that's it. Get some digital scales and weigh (ideally down to 0.1 of a gram) as this will allow you maintain a consistent dose. Then change your grind until you get the taste you like. Try 20 seconds, 25, 30 etc.

    Also, if you have scales, a more accurate way to measure what comes out is by weight rather than volume (ml). Aim for double the weight of espresso out than ground coffee in as a starting point, and then adjust based on tastiest result.

    All the best!

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    Bames: Yes, I know it doesn't have an OPV, and everything you say makes perfect sense - thanks. (and I have no trouble believing that 11 bar figure for 60mL in 25-30 seconds, assuming roughly 12 o'clock is 9 bar, which according to a post I saw elsewhere was the case for at least one machine on which a proper gauge had been fitted)

    Now if someone could do the test, I'd appreciate it. Chop chop.....

    Greg.

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    I think you need to keep in mind what you hope to gain from this. Sure, it will interesting to know what pressure you are extracting at, but how will it help? I have a hard time getting my head around the variables in the system, but I found moving from the sunbeam to a fixed pressure (rotary) machine, changes in the grind had a more dramatic effect on extraction times. With the Sunbeam if you overdosed/ground too fine it would still pump it through, in extreme cases dripping out pure oil! I figure the pressure behind the puck was atleast 13 or so barr. In my rotary or gaggia (OPV) these would simply choke the machine and nothing would come through.

    In theory one could adjust dose and grind to get 9 barr shots on the sunbeam, but then the flow rate might be too high giving fast shots? I have a feeling that a nice, syrupy shot on the em6910 is around 10.5 barr. Hah once again complete guesswork.

    I'm not having a go at you or anything, I would also love to learn more about how the system works, I'm just not sure how it will help you. Someone like Chris (talkcoffee) would have experience playing around with pressure profiles on prosumer machines and the impact it has, I expect there are more important variables than a 1 bar difference in pressure. I will say though that while my lattes haven't changed much with the new machine, the espressos are significantly better.

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    Also, let's say I did stick to Sunbeam's recommendation (ignoring your advice), and tried to keep the pressure in the recommended range (ideally near the centre). Is it possible to produce a relatively fast shot that is roughly equivalent in taste, to a shot that is taken with a higher pressure, but for a longer time?

    Greg.

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    It's weird. There is very little sensible response in the other thread, and oodles of it here.

    All this talk of laminar and turbulent flow... you're not an undergraduate engineering student by chance?

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    Still not trying to hit your experiment on the head, but Bames is right - the pressure gauge is a waste of space. The 6910 pressure gauges are notoriously useless. But have fun experimenting. As you say in your other thread, you will learn a lot.

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    burr: Sorry - I had replied before noticing your reply. As you can see, I have the same kind of questions you do.

    I'm wondering whether the concept of "extraction energy" might be useful for espresso making. I.e - just perhaps, it might be possible to produce a fast high pressure shot that is approximately equivalent to a slow, low pressure shot - in both cases the total ENERGY imparted by the water to the grinds might be the same.........

    Greg.

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    Just do the test someone. This isn't my fault - it's Sunbeam's fault for not including a calibrated pressure gauge.

    Greg.

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    Hi dont mean to but in. I have been playing around with my sunbeam 6910 for years but the only time I got a consistent tasty shot was when I pumped the pressure past sunbeams guidelines

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    Thanks thewoodensquirrel. Maybe that means shot TIME might be more important than shot PRESSURE. (others have kind if implied that, but not very clearly)

    Greg.

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    And just as a matter of reference our wega that we have in our cafe generally stays within 10 bar give or take (its temperamental)

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    Something else that might interest you - once you make the pressure high enough, the shot actually slows down again (for a give grind and dose). Can remember when this starts to happen, but I'm pretty sure its in Illy's book somewhere (my copy is packed at the moment). If you do a bit of searching you will find a lot of info about the influence of pressure in espresso. But as said before, the variables associated with the 6910 will outweigh anything due to shot pressure.

  19. #19
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    Agreed Pete,

    My opinion? This one's a red herring and with a Sunbeam, not worth the effort anyway. The best shot will occur with the gauge well beyond what Sunbeam labels as the "optimum zone".

    The right answer is when the palate determines a balanced shot.

    Skip- My reading of this one is that some training on the machine will benefit you much more than a reading from any gauge- be it portafilter pressure gauge or Sunbeam's moving arrow against some pretty colours.
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    Quote Originally Posted by Pete39 View Post
    Something else that might interest you - once you make the pressure high enough, the shot actually slows down again (for a give grind and dose).
    I don't understand what you mean, exactly. The pressure is DEFINED by the dose, grind, and tamp. The more resistance the puck has, the higher the pressure will be, and the slower the shot will be. Is this all you mean?

    Anyway, someone PM'd me this link: Set up and initial use Nic's Stuff (I hope the PMer doesn't mind me posting it here) According to them, the dual-wall basket produces 9 bars.

    MrJack: Not a student, no, but I did get my EE in 1988, did a bit of engineering, lot's of paperwork, and am now a full time limo driver. Make of that what you will.

    Greg.

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    Quote Originally Posted by Talk_Coffee View Post
    Agreed Pete,

    The best shot will occur with the gauge well beyond what Sunbeam labels as the "optimum zone".

    The right answer is when the palate determines a balanced shot.
    Couldn't agree more. My shots were never within the marked "safe zone". The needle was always way past.

    The only way I could keep it within that zone would be to under dose, resulting in a fast flow with little crema. A whole lot of experimenting with that machine before I upgraded to a HX..
    I found the "sweet spot" to be using 21grams of coffee, with a light, even tamp. The needle would almost be in the red, but the flavour was good and crema was decent.

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    I use the gauge purely as a relative measure. Like others I get my best shots well above SB's recommended point. For me the best is when the needle sits just above the top of the 2 segments for 'best' - if my shot varies from that position so does the quality. I dose at ~15g - 16g in both the SB double (for decaf) and my VST 15g (for my coffees) which gives a level about 5mm down in the basket.

    I've been trying some different beans over the past few days and now I think of it, I haven't even checked where the gauge is for them. I use the output as my measure of whether I've got it right or not. I have a trick I use if I get the dripples (coffee gives ongoing drips rather than forming a stream) and that is hit the button to stop the flow then immediately again to restart. Seems to let a better flow happen.

  23. #23
    Senior Member chokkidog's Avatar
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    Quote Originally Posted by Skip View Post
    Now if someone could do the test, I'd appreciate it. Chop chop.....
    Quote Originally Posted by Skip View Post
    Just do the test someone.
    10 posts in the thread and not a 'please' to be seen?? Steady on old chap!!
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    Please, and thanks in advance.

    Now off you go and do the test - there's a good chap.

    ;^)

    Greg.

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    Quote Originally Posted by Skip View Post
    Please, and thanks in advance.

    Now off you go and do the test - there's a good chap.

    ;^)

    Greg.
    With an attitude like that you come off as VERY gen Y, but you're far too old for that so no excuses mate.
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    The wink means I was just joking! In all honesty, I was just trying to be playful.

    Cheers,
    Greg.

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    Honestly Skip....The cafes with pressure profiling machines most likely couldn't give a toss about your machine and they're not going to "chop chop" anything for you mate- regardless of how much your tongue makes your cheek protrude.

    Your early posts indicate you could train some and learn some- or not- as you please.

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    Thanks Talk_Coffee - there's less need for the test now anyway, given the link provided to me by that kind PMer (and Bames' estimate of the pressure), but it would still be interesting to do it anyway. Hopefully a person with the right kind of machine will be interested. The very best thing for me to do, though (regarding the gauge calibration), would be to rent that Pullman pressure gauge, and as I said, I will do that soon as well. I will certainly consider getting the training as well - thanks.

    Greg.

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    Quote Originally Posted by Talk_Coffee View Post
    Honestly Skip....The cafes with pressure profiling machines most likely couldn't give a toss about your machine and they're not going to "chop chop" anything for you mate- regardless of how much your tongue makes your cheek protrude..
    Do you need pressure profiling? Can you not turn a rotary pump up and down?

  30. #30
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    Sure can. Would you care to bother when it's not going to provide anything whatsoever of use? Probably not... A p/f pressure gauge will do the job.

    FWIW, I have never done anything more with a Sunbeam other than train people to get a good shot out of them. Do they have any mechanism of adjusting brew pressure anyway?

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    Quote Originally Posted by Talk_Coffee View Post
    Honestly Skip....The cafes with pressure profiling machines most likely couldn't give a toss about your machine and they're not going to "chop chop" anything for you mate- regardless of how much your tongue makes your cheek protrude.

    Your early posts indicate you could train some and learn some- or not- as you please.


    This piece of advice makes sense. Along with most of the advice here.

    Just for all who are interested. Manners get you a long way. "Words on a page" are easily misinterpreted. A sense of humour is an individual thing (Not everyone will "Get" the cut of your jib")

    So when asking for advice, be nice. You will get plenty of free advice if you do.

    Reminds me of a saying "We don't see things as they are. We see them as "We are". For the philosophical out there.

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    Quote Originally Posted by Talk_Coffee View Post
    Sure can. Would you care to bother when it's not going to provide anything whatsoever of use? Probably not... A p/f pressure gauge will do the job.

    FWIW, I have never done anything more with a Sunbeam other than train people to get a good shot out of them. Do they have any mechanism of adjusting brew pressure anyway?
    I wasn't saying it was a good idea, merely that you don't need a Vesuvius to alter the brew pressure on a prosumer machine (as long as you keep the same pressure through the entire shot).

    What I don't understand is why sunbeam/breville are going for all this preinfusion malarkey when fitting an OPV probably gives better results in the cup.

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    ....and preinfusion has what to do with the presence or absence of an OPV??

    I'm out. This thread started silly and has not improved at all.
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    Quote Originally Posted by Hildy View Post
    What I don't understand is why sunbeam/breville are going for all this preinfusion malarkey when fitting an OPV probably gives better results in the cup.
    For the 6910, its probably because the "preinfusion" (ie, pulsing the pump a few times before the continuous run for the shot) is much cheaper than fitting an OPV.

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    I'm not sure to what extent the two (OPV & pre-infusion) are related. For example, the BES920 has both these functions.

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    Sheesh...

    Talk about the blind leading the blind; I'm not even going to try...

    Mal.
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    The whole sorry mess just makes my head hurt!
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    Behmor Brazen - $249 - Free Freight
    Quote Originally Posted by Hildy View Post
    I wasn't saying it was a good idea, merely that you don't need a Vesuvius to alter the brew pressure on a prosumer machine (as long as you keep the same pressure through the entire shot).

    What I don't understand is why sunbeam/breville are going for all this preinfusion malarkey when fitting an OPV probably gives better results in the cup.
    What the...?!?!?!
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