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Gaggia Classic - Portafilter Pressure Gauge - OPV mod

92K views 227 replies 93 participants last post by  MrShades 
#1 ·
I got around to making a pressure gauge for my Classic.

I was looking for the parts to make it and found an ebay seller that had everything I needed - cpmpneumatics. It turned out the seller was only a couple of miles away so I called in and picked them up.

Anyway I thought I'd post the details so anyone can order them and make their own. The only extra you'll need is some PTFE tape to seal the threads. I only needed it on the portafilter.

Please note: This assumes your PF thread is 3/8" BSP

Pressure Gauge

Reducing Bush

If you need PTFE tape they even do that

PTFE Tape

Here is the finished article.

attachment.php?attachmentid=1164&d=1336677782
 
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#6 ·
MikeHag said:
Just a thought... have you considered adding a ball valve to the setup, which would allow you to let water flow out at a rate simulating an espresso shot?
I have thought about this quite a bit and have done a bit of digging on the interweb. I was trying to get to the source of the 10bar static pressure = 9 bar brew pressure myth.

A ball valve apparently is not the best option as it is difficult to control flow, but needle valves are a little pricey. Some have suggested open the steam valve which is something I am going to try. Others say it is almost impossible to replicate the espresso shot in any case and it is best to experiment with various static readings and choose which tastes best.
 
#7 ·
I have tried the steam valve method and there is no more than 0.4 bar difference (disclaimer: on my machine). I cracked a leak on the portafilter gauge itself at about the same flow rate, just to check it mattered where the pressure relief was located, but it made near as darn no difference.

I adjusted down to just below 9 bar. First shot was a choker so dialled the grind a bit coarser. Second shot definitely was about right (40g from 18g in 25secs) and there was no doubt a LOT more crema, but it looks and tastes a little over extracted. Still good, but certainly leaning that way. I have found that pressure does have quite an effect on temp surfing, so will have a play and make sure I'm not runing too hot.
 
#9 ·
He he. That is by far the hardest part of the exercise. It has some loctite on it or similar.

I don't have a vice. I found a screwdriver that fit through the spout. I felt sure I was going to snap it on a number of occasions.

It was not a case of cracking the glue and wind it off either. It took several turns before it got any easier and several times I feared it was stuck solid, I couldn't even wind it back. Anyway perseverance go me there in the end.

It would be a lot easier with a vice
;)
 
#13 ·
nobrob said:
A screwdriver will damage the surface of your spout!

Take a hammer and a piece of wood. Lay the wood on one side of the spout and tap with the hammer.

It will budge
:)
Lol I hate to think what you thought I meant to do with the screwdriver. You pass it through the hole in the spout it should be a nice tight fit thus giving you good purchase to unscrew the spouts no chance of damaging the surface or squashing the spouts
 
#17 ·
Just did the mod. Improvised by putting the round handle of a can opener through the spout and bashing it with a hammer until the loctite came off.

My Classic was running at TWELVE BAR. Got it down to just over 9 in two attempts.

Thanks everyone for your help. This is a great forum!
 
#20 ·
So my gauge parts arrived today - turns out my opv valve was set at 14 bar! I had guessed it might be a bit high as I'd been having quite a lot of channelling and had to grind really fine to slow the flow down.

I really think anyone with a classic that isn't using pods should do this mod.

Also, opening the valve on the steam wand does work for pre infusion - with the gauge attached and pump running you can effectively pressure profile with a bit of a twist of the steam knob. Not something I'm that bothered about at the moment but interesting none the less.
 
#23 · (Edited by Moderator)
Now I have done the mod I'm happy to lend my gauge around to forum members. I'd like it back at some point but if anyone is interested then post up.

I know they're pretty cheap but once the adjustment is done its just going to be sat on my shelf. If the demand is anything like last time a gauge was sent around then we can come up with a system. Otherwise just £2 via PayPal to cover postage is fine with me. I'd rather it isn't just totally random people from the internets so I'll put an arbitrary limit of 10 genuine posts to be able to borrow.

List:

1. Jason1wood - done

2. Obsy - has gauge

3. Oldman

4. MartinB
 
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