Building a Portafilter Pressure Gauge - Page 5

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gj91
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#41: Post by gj91 »

gj91 wrote:I have looked at a ton of these now between HB and Coffeegeek. I am going to give a non-liquid gauge a shot. I am going the flow through route. Otherwise I am going to get one of the liquid filled ones. I just don't see the liquid filled ones at local hardware stores. I am going to try HD and Lowes.

I first need to test my Silvia then I will probably have to get the new OPV valve if I need to adjust. It seems that 9 bar without the flow is a good target, that means it's a little less when there is actually flow.
Well, here is my contribution. I used a non-liquid pressure gauge from Sears. It was on the air compressor parts isle.

First I tried to put a bunch of stuff on but there is no room to turn the portafilter so I opted for an Elbow connection and reducer to fit the 1/4" gauge and it worked just fine. No dancing around on the gauge and a solid 10 bar after it touched 11 bar but settled back to 10 bar. This was blind too.

The only time the gauge danced around was when I would test again without emptying the water. Other then that it worked fine.

Now I'm not sure what 10 bar means. Probably around 9 bar if it was flowing through which isn't bad. not sure if it's worth getting an adjustable OPV valve and get it down to 9 bar.

Here is my photos. I need to clean Silvia up.


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HB
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#42: Post by HB »

askay wrote:All went well, except the dry gauge vibrated like hell.
Juanjo wrote:I've try few cheap ebay DRY gauges and they work.
SJM wrote:I'm sticking by mine: dry gauge (on a Gaggia) fluctuated so much that it was untrustworthy.
Allow me to clarify... they're called vibratory pumps for a reason:

Image
Image courtesy of Made in the GARAGE

How much of the 60Hz back-n-forth is reflected in the gauge depends on the machine. For example, if it has a gicleur (orifice) in the grouphead, the gauge will vibrate significantly less. The sensitivity of the gauge itself also comes into play. To dampen needle flutter, manufacturers use a coil of thin copper tubing or snubber (e.g., an inline poreous stone or dampening piston).

As an example, the needle on the portafilter pressure gauge I made from Ace Hardware parts vibrated like a hummingbird's wings when used on my Rancilio Silvia. It buzzed on La Valentina (E61 with gicleur), but was readable. Of course the Scace II has a quality liquid-filled gauge and its reading is rock solid.

Rotary pumps also generate pulses, but they're barely noticeable for most air gauges with no dampening.
Dan Kehn

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Peppersass
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#43: Post by Peppersass »

Need some advice.

I'm about to build a PF pressure gauge for my new Silvia. I've got a Scace-recommended liquid-filled gauge on order. I have a Rancilio bottomless PF and Silvia's stock V3 PF.

I read in this and other threads that you have to remove the basket or there will be leakage between the underside of the basket lip and the PF. But I don't like the idea of forcing the sharper edge of the PF against the gasket. I've seen some vids and pics of pressure gauges that were built by drilling a hole in a blind basket and putting it in a bottomless PF. This approach is appealing to me in that it's kinder to the gasket and won't require removing the spouts from the stock PF.

Is there any problems with the drilled blind basket approach? What kind of adapter is best to use through the hole in the basket? Do I need to take any special precautions to seal the adapter to the blind basket, such as using an o-ring, rubber gasket, epoxy, etc.?

Thanks in advance for any help.

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erics
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#44: Post by erics »

You CANNOT or perhaps, better said, SHOULD NOT use a blind basket because there is ZILCH clearance between the bottom of the basket (on the inside) and your shower screen.

I do agree with you as regards your thoughts on the "sharp" edge of the PF as compared to the smooth rolled edge of the basket BUT, be a little gentle with the PF and all will be well.
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

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Peppersass
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#45: Post by Peppersass replying to erics »

Thanks, Eric. Just the person I hoped would reply!

I'll try to be careful with the PF.

winboot
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#46: Post by winboot »

Sorry for bringing this thread back up but it's the best i could find.

I added a gauge to my portafilter without having a flow and not using a basket either.
When i put my machine (DC Supermini) on, it goes to 8.2 bar alot slower then i expected but then it keeps going further after some while.

Anyone has an idea what may cause this?

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HB
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#47: Post by HB »

I've seen the same thing. In my case, it was caused by inlet pressure that slowly increased. Checking the house's water pressure, I found that it would be the pressure regulator's set point if water was flowing, but would slowly increase to street pressure at idle. The house's pressure regulator was 15+ years old; replacing it solved both problems.

That may not be your problem though; a quick test is to draw water from a bucket instead. If the brew pressure still creeps up, then it's the pump's bypass valve allowing more water to pass from the outlet to inlet side when there's no flow than when there is.
Dan Kehn

winboot
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#48: Post by winboot replying to HB »

Ah ok, i guess i found my problem then. I'm currently drawing from a water reservoir, not using a flojet or line pressure of any kind.

Guess it's time to finally plumb it in then :)

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HB
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#49: Post by HB »

To clarify, if the brew pressure is steady under flow, don't worry about the meandering blind filter pressure. Loosening the gauge enough to go drip-drip-drip will usually eliminate the (false) rising brew pressure measurement.
Dan Kehn

winboot
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#50: Post by winboot »

But still my pressure should be more then 8.2 bar i guess? Or maybe i should only start calibrating after i have tried with flow?