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Building a Portafilter Pressure Gauge

Postby TroyR on Thu Jun 14, 2007 10:49 pm

So I ran off and bought a pressure gauge, elbow and adapters to piece together a portafilter pressure gauge for myself.

When I got home and put it all together, I realized (eventually) that my current configuration of: basket -> portafilter -> 3/8"x3/8" elbow -> 3/8"x1/4" adapter ->1/4"x1/8" adapter -> 300 PSI gauge just wasn't going to work. :?

I had completely forgotten that I do not have a seal between the basket and the portafilter itself!
Lets not worry (for now) about the fact that I have forced together the 3/8" parallel threads of the portafilter and the 3/8" NPT on the elbow. :oops:

Does anyone have any advice to make a seal between the basket and portafilter?

Cheers,
Troy
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Postby HB on Thu Jun 14, 2007 11:02 pm

TroyR wrote:Does anyone have any advice to make a seal between the basket and portafilter?

Why not remove the basket? The portafilter should seal against the gasket without it.

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Bob Roseman's DIY portafilter gauge (link)
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Postby TroyR on Thu Jun 14, 2007 11:20 pm

My stock Bezzera PF has a two notches in the lip positioned near the centre of each ear. Apparently this is not common I guess.
My bottomless PF has no notches, but that presents a whole new set of problems for this application.

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Postby HB on Thu Jun 14, 2007 11:30 pm

Too bad, the old Rancilio portafilters for Silvia had similar notches. In the photo below, its blind basket is drilled:

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alt.coffee's traveling portafilter, current whereabouts unknown

I've seen photos of similar portafilters with the notch brazed over (example). I wonder if a big, thick o-ring under the basket rim would get a good enough seal to measure the pressure. While not a direct answer to your dilemma, Testing Brew Pressure offers some other options.
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Postby TroyR on Fri Jun 15, 2007 12:18 am

Thanks Dan, I kind of like the idea of T'ing in rather than (or before) brazing the notches. Since the panels need to come off anyway to make the adjustment it shouldn't matter if the gauge is external or internal.
With a 116 deg C max operating temp the gauge should even be able to reside inside the machine.
Cheers,
Troy
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Postby cannonfodder on Sun Jun 17, 2007 5:55 pm

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Dave Stephens
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Postby GRB on Mon Jun 18, 2007 7:45 am

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Postby Designer on Mon Jun 18, 2007 3:08 pm

GRB wrote:<image>



Hi GRB, Is that a needle valve?
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Postby GRB on Mon Jun 18, 2007 9:22 pm

Hi GRB, Is that a needle valve?


Yes. Allows me to simulate the shot flow and measure pressure at the same time.
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Postby TroyR on Mon Jun 18, 2007 9:38 pm

Well, I found a post on CG (I think) that said the poster was able to get a Bezzera PF to seal with the basket using Teflon tape around the outer side- wall of the basket.
Sure enough, 3 miles of Teflon tape later I got a seal between my single basket and the PF. Now just to dial it in, the stock OPV setting was ONLY 13 bar. :shock:
It was surprising to see how the pressure ramps up slowly though, I thought it would have been quicker than it is. Granted, this closed system is entirely different than a basket of coffee.

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Troy
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