HB wrote:Given a rotary pump's high flow rate, some dribbling won't affect the displayed pressure reading. I cannot say if a "mini-geyser" would invalidate the reading entirely.

Thanks-I figure that am losing maybe 1oz over a 12-15 second pull with the gauge. I wouldn't be surprised to find that my reading ended up .5 BAR off. Still, that would be within target (about 9.5 BAR).

The picture you posted of the naked extraction "beauty" shot: was that tongue-in-cheek, or is that what a good naked shot looks like? Most pics I see are of a single stream, although mine look just like your picture when starting out (1st 8 seconds).

If it's dribbling only one ounce in 15 seconds, the reading is trustworthy. True "dead head" readings on a rotary pump creep up. Bob explained how to get a more accurate reading in Help with La Cimbali Jr.:

bobroseman wrote:It seems to me that if your going to measure brew pressure and make adjustments, then you need to know the exact pressure that you have while pulling a shot. Most portafilter gauges measure only the static pressure at the brew head when the by-pass valve has opened. That is not the pressure you are getting when you are brewing espresso. The attached photo is a simple mod I made to the gauge I bought from Chris Coffee. I can adjust the needle valve to allow precisly 2 oz of water to flow in 25 seconds while reading the pressure. On my machine, the resulting pressure is 8 bar, as seen in the inset.

Bob



here it is in use:

As for the "beauty shot" I posted earllier, the article explains that it's beautifully flawed. There's gigabytes of pictures of proper extractions posted on the Internet, but in my opinion, there's not enough instructive improper extractions.

Indeed, I've had a lot of shots like that. I've been berating myself for my distribution (and in truth, a lot of it was probably deserved) but I finally got around to checking today and yes, my Bric was at 11 bar.
Now, that's 11 bar with a grouphead gauge with no needle valve. When folks say "8.5-10 bar" as ideal, is that the measurement they mean? Or should I mentally add a bit to that 8.5-10 bar to compensate? If I was letting through 2 oz. in 30 seconds, then my reading would be somewhat lower, but I sure don't know how much.

Perhaps there's some bright side of having it too high for a while -- I feel a bit better that, if I can distribute enough to not channel under very high pressure, perhaps I'm well-trained to do it at 9.25 bars. Like training for track meet with a weighted vest. Maybe.

matt wrote:Now, that's 11 bar with a grouphead gauge with no needle valve. When folks say "8.5-10 bar" as ideal, is that the measurement they mean? Or should I mentally add a bit to that 8.5-10 bar to compensate?

The reading I've seen on a rotary pump from such a (non bleeding) gauge will "creep" upward, so it's hard to generalize about the static versus dynamic brew pressure. You'll get a more accurate reading if there is even a tiny flow. In a pinch I've loosened the portafilter gauge slightly so it drips and that's enough for a steady reading (of course don't loosen it too much or you may get sprayed!).

On my Bricoletta (after adjusting the pressure), with a fluid filled gauge directly on the PF and no leakage at all, it reads a little over 9 Bar, and does not seem to creep up at all...the gauge goes from 0 - 9 bar in a few seconds, and doesn't move from there...at least in the amount of time I have left it (about 15 seconds maybe).

Grant

Sounds good. I didn't remember seeing any creep on my gauge (on a Briccoletta), but I figured I may not have watched it long enough.
I'm not in front of the machine now, but unless someone corrects me, I'll plan on using the reading from a sealed gauge if it's holding steady, and giving it a bit of a leak if it creeps upwards.

Thanks a lot, guys.

Grant wrote:On my Bricoletta (after adjusting the pressure), with a fluid filled gauge directly on the PF and no leakage at all, it reads a little over 9 Bar, and does not seem to creep up at all...the gauge goes from 0 - 9 bar in a few seconds, and doesn't move from there...at least in the amount of time I have left it (about 15 seconds maybe).

My experience mirrors that of Grant. On two different rotary pump machines, using a nonfilled PF gauge and blind filter, the pressure reading ramps up to the max setting (9 bars) over a few seconds and then holds rock steady. I'm getting approximately the same reading on my builtin Vetrano pressure gauge (hard to read with any precision, the markings only run 0, 8, 12, and 15 bars), perhaps a bit less under typical espresso flow.

I FINALLY got the Shurflo accumulator installed (I was over in Japan for awhile, which is another story (amazing drip coffee (made to order), horrible espresso). Getting the required installation parts locally was a pain: I had to use a bunch of fittings and runs of the 1/4 tubing to connect them all, as the local Home Depot didn't have what I needed, and they have run all of the plumbing places/hardware stores out of business.

The water hammer is definitely gone, but I am getting the pressure creep mentioned above. After pressurization (3 seconds or so) the pressure gauge comes right to 9.25 Bar, then keeps slowly heading up, to 12 Bar in about 20 seconds.

Isn't the whole point of the pressure adjustment to adjust a blow-off valve? Therefore, the pressure cannot move past that point? If so, why am I heading above that pressure (up to 12 Bar)? Or do rotary pumps work differently than Vibe pumps?

Also, is there any way to somewhat estimate my likely ristretto brew pressure without having to buy the flow regulator kit that Bob mentions above? Close would be good enough: I am not that worried if the brew pressure is reading 9 when it is actually 9.5 Bar at this point, but if I am seeing 9 Bar and the actual brew pressure is only somewhere between 6 and 12 Bar, it doesn't tell me much.

dawgcatching wrote:Also, is there any way to somewhat estimate my likely ristretto brew pressure without having to buy the flow regulator kit that Bob mentions above?

Didn't I respond to this earlier?

HB wrote:You'll get a more accurate reading if there is even a tiny flow. In a pinch I've loosened the portafilter gauge slightly so it drips and that's enough for a steady reading (of course don't loosen it too much or you may get sprayed!).

You can also measure it while pulling a shot.

Sorry, I missed the end of that earlier reply. Hey, it was late on a Saturday night, give me a break....

The good news is with that Shurflo accumulator, things are MUCH improved already. The occasional little squirties that I used to get with a bottomless double (and which seemed to accompany nearly every shot, good or bad) have disappeared. Plus, my FloJet isn't kicking on and off every 5 seconds. Thanks everyone!