# Pressure gauge discussion, experiment, improvement



## FairRecycler

Hi Everyone,

I thought I start this topic, to gather as much information as we can, in the hope for an ultimate recipe, to eliminate the vibration of the needle.

I'm far from expert in this topic, so every input would be greatly appreciated.

I'm aiming to start the experiment next week, where I'm willing to test the the following variables on a freshly rebuild machine with a stainless steel 41.3mm (1 5/16") glycerine filled gauge:

- Water filled / air filled capillary tube

- Length of capillary tube (short straight / short single coil / longer 5-10 coils)
_I would appreciate some input on theoretically ideal length, if such exists._

- Height of gauge in reference of sampling point.

- Sampling point: boiler in-feed / outfeed
_Sorry I'm not planning to test the pump outfeed (T piece on PTFE tube), as I can't see it any chance for it being any better by going closer to the vibratory pump._

- Routing
_I would also appreciate some input on this._

I'm open to test other reasonable variables too, feel free to give suggestions

For your reference, I attach photos of my actual kit.

Also link a couple of videos I made last year

Bad one:

https://drive.google.com/file/d/1L7AMSugEXKaGLcr-v-F42RROKnk1gIBC/view?usp=drivesdk

Good one (I suppose):

https://drive.google.com/file/d/1XolCMfJ8JVIQKaKB8Ju-BlzN5GO1QZ0J/view?usp=drivesdk

Thank you in advance for all your support and expertise.

Peter


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## L&R

I like your approach for making an adapter for OPV. Unfortunately for other points I cant say much, maybe only I would use quality gauges like Orman or similar. Do you sell them?


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## FairRecycler

L&R said:


> I like your approach for making an adapter for OPV. Unfortunately for other points I cant say much, maybe only I would use quality gauges like Orman or similar. Do you sell them?


 Hi,

Thank you.

Thanks for your suggestion, I'll look into that.

If anyone have a surplus branded gauge laying around, which I could borrow for a few weeks for testing, that would be great.

Yes these are available on here and on eBay too.


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## Nightrider_1uk

I notice that everybody seems to use thin bore capillary tube for their gauge. Has anybody tried 6mm PTFE tubing?


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## Norvin

Why don't you just use the spare connection on the steam valve found on the Gaggias without the OPV? It wouldn't be too difficult to remove the ball and spring and find a suitable adapter for the capilliary tube. It would then be a straight swap.


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## Blue_Cafe

Good idea for a thread.

As i don't like the idea of meddling with the boiler safety valves in these espresso machines, and, still can't get my head around using the PRVs to control pressure in the puck, i am looking myself at putting a pressure gauge on my Classic.

I've seen a few attempts and mostly, they all work on the principle of taking a tap from the pump discharge and mounting the capillary tubed gauge low down in the machine.

I have a few issues with this.

A) Taking the pressure tapping from the pump side of the boiler is not, i think, best practice. It exposes the gauge to the vibrations and shock from the pump and is as far away from the group head (where you want to be) as possible.

B) Capillary tubing is so small that normal flow into/out of it isn't going to happen. However, i don't think zero flow happens either. Its a dead space/void in the flow path and that's always a bad idea where hygiene or hold up is an issue. I think you will have some movements of fluid but it will be by convection, vibration etc and will be slow. Its a bug pot imho.

C) Putting the Gauge low is again a problem for the issues noted in (B) I see it is common to tee off in a manner which is not free draining, usually with the tee pointing down from the pump tap. Another sump created with a dead head.

I have looked to see how other manufacturers have added pressure gauges to their machines and how they resolve the issues noted above.

Sage, in their Dual boilers take the pressure tap on the boiler side of the system from the multiport block valve (3 way solenoid).

Here is a good video showing the guts of the DB:






I like the gauge fitting etc, but it fails on all of the points i noted above and is not a good idea i think. It suffers from hold up and is on the wrong side of the boiler.

I think the best approach is the Sage DB, but without remanufacturing the valve block footprint, its not possible.

So i would take the tapping of the steam valve or any other boiler port (make one yourself!) and run a normal tube without kinks, up to the gauge which is mounted at a high point above the boiler tapping. I've been looking for slim, vertical pressure indicators, but they are not common.

I shall watch this thread with interest!


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## L&R

Very good idea Norvin, actually I have some old brass valves from Gaggia Coffee laying around will try to braze a capillary tube to the extension cap to see how it will work.


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## Blue_Cafe

Actually,

On the 2015 V2 models, simply tee into the steam valve feed hose with a std compression fitting tee and use the same tubing to route to the gauge.

Easy enough. It's the gauge position and mounting which is the difficult bit.


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## Norvin

L&R said:


> Very good idea Norvin, actually I have some old brass valves from Gaggia Coffee laying around will try to braze a capillary tube to the extension cap to see how it will work.


 Good idea, but for those without brazing equipment there shouldn't be a need to braze anything. There is an internal thread in the valve (1/8 BSP?), it should be possible to find a standard adapter to fit this at one end with an external thread at the other end (1/4 BSP?) to fit the capilliary tube fitting.


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## L&R

This thread will be a problem I don't think it is common, better to use some brass solder stick and a propane torch they are small and will be easy to be welded together.


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## phario

It's good that we can take some of our conversations onto an official thread @FairRecycler.



FairRecycler said:


> Bad one:
> 
> https://drive.google.com/file/d/1L7AMSugEXKaGLcr-v-F42RROKnk1gIBC/view?usp=drivesdk
> 
> Good one (I suppose):
> 
> https://drive.google.com/file/d/1XolCMfJ8JVIQKaKB8Ju-BlzN5GO1QZ0J/view?usp=drivesdk


 Just to be clear, the first video should worry anybody who's doing an install -- a glycerine filled gauge that is vibrating pretty badly. Do you have a guess at the reason for that?

*Routing 1:* I believe that @MartinB has suggested that the best route is one that goes to the right of the boiler. However, because of the distances involved, this basically means you have to bend the capillary tube close to 90 degrees if you're going to mount it to the left. Cue @ratty in here who just answered my question this morning about the 90 degree bend issue.

https://www.coffeeforums.co.uk/topic/52816-gaggia-classic-2013-refurb/page/3/?tab=comments&do=embed&comment=755752&embedComment=755752&embedDo=findComment#comment-755752

I've stolen his pictures below so we have an immediate reference image. However, I also think that his gauge is different---on the glycerine ones you use, I think the distance to the boiler is much more limiting. Also, if I had to guess, his gauge is more centred.









*Routing 2: *One idea that I have not seen discussed, for those that use a T-junction, is to simply move the T-junction further downstream from the pump. Most installs I assume people are cutting their pump-to-OPV pipe and just choosing a location. Some people cut it closer to the pump, some further away. Has anybody tried to simply extend the pump-to-OPV piping and attach the T-junction further away?

It could be that this has little effect because the vibrational issue seems to be a function of the flow itself and not the actual vibration of the pump in the Gaggia case.

*Length of capillary tube:* Unfortunately I bought a gauge from shock_waves_shop recently had entered into a debate with him about the shortened capillary tubes. It is unclear to me the magnitude of the effect of a longer coil, but there is plenty of anecdotal evidence to suggest that a longer coil leads to reduced flutter. Here are a number of people who note that replacing their capillary tubes with a longer version reduces vibrations.

If you are curious the snubber that was linked a bit lower is here -- I believe a 1/4" male to 1/4" female porous snubber; basically a valve with a porous medium in it that should reduce the vibrations. It would probably cost about £10-15 more to install once you deal with all the pipe changes.

The post by HB here explains how flutter is a function of the vibration pump and notes the difference in flutter observed over different machines.

*Wet/dry capillary tube:* In your various install guidance @FairRecycler you note the importance of filling the capillary tube with fluid in order to eliminate air. This is slightly opposed to the links above that have noted that people have taken efforts to dry their capillary tube using a heating gun or butane torch. However, it is not clear to me the effect of either suggestion. See below on the fridge discussion, but it seems you either want a completely liquid filled or completely air filled tube and that's essentially it. If this is the case, then your suggestion is not contradictory to the advice of trying to remove all liquid.

*Block on the radiator:* As most people have noted, you have a unique design of a block on the radiator rather than a T-junction from pump-to-OPV. Again I don't have a huge insight into this choice; as noted, it seems more stable because it is further away from the pump, so at worst, it doesn't seem to hurt. At best, it helps a lot. But the video you linked of the needle flutter (your "bad" video) is interesting because it shows that this isn't a simple fix.

If the effect of the snubber is to essentially remove non-uniformities in the flow, then placing your block after the OPV might have a positive effect. I'm not sure.

*Tapping into the steam valve:* @hugoread has done it and might comment: https://coffeeforums.co.uk/topic/48961-gaggia-classic-pressure-gauge-install-video/

Also see this reference by the Polish blogger and includes clear images of how the tapping can be done: https://gaggiaclassicmods.blogspot.com/2015/12/manometr-raz-jeszcze-podaczanie-do.html

Crucially, note that the blogger stated that he did the steam valve mod because his previous T-junction pump-to-OPV gauge indicated -2 bars less than expected. This was later discovered to be an issue of a malfunctioning gauge, not because of the position.

*Scientific literature: *I tried to turn to the scientific literature for guidance. The main application area for capillary tubing and vibration that is discussed and that might be applicable for us is for minimising noise from refrigerators. For example [1], [2], [3]. However, I'm not sure the applications/results are exactly the same. In the fridge, the capillary tubing is used to pass through the liquid so that it is compressed and pressurised, then moved into an expansion chamber where it turns into a gas. Basically, if I understand the research, then the main theory is that noise is primarily created due to bubbles created at the capillary tubing inlet, which are then 'released' at the outlet and so this produces the noise.

The work, for example, by Daniel Hartmann [2] above and also these people seek to change the inlet to reduce this issue -- i.e. either reduce the diameter of the capillary inlet or lengthen it.

I do not know how this 'jives' with the above questions, but there is some reason to believe that the main vibrational issue is can be dealt with by 'pre-treating' the flow prior to entering the capillary tube, and that this can have a larger effect than what you do with the capillary tubing itself.


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## Nightrider_1uk

Is there room to fit a 0-20 bar Pressure Gauge Snubber to the back of the gauge before connecting the capillary.


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## Blue_Cafe

Capillary tubes are primarily for Gauge positioning. The best place for the gauge is on the vessel itself. (mostly).

The longer the tube, the greater the lag between action and response. This may be explaining why some notice a difference in needle twitch.

Coiling the capillary tube can be a way of providing heat loss (or gain) which will effect the readings accordingly.

I suspect the main difference people are seeing in needle response may be down to some localised flooding in the capillary tubes, with those flooded systems behaving worse then the non flooded ones ( you can't compress fluid)

If you are trying to come from the pump side, perhaps an expansion chamber is needed ( which is the boiler in effect) to dampen out the hydraulics coming off the pump.

In the OP's instance, the brass block is a great idea but on the wrong port. If it was on the solenoid port, you would have the boiler as a buffer.


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## phario

Nightrider_1uk said:


> Is there room to fit a 0-20 bar Pressure Gauge Snubber to the back of the gauge before connecting the capillary.


 Moving on this idea, does anyone know what type of snubber might work with the least number of extra attachments/tube conversions from the normal T-junction route? If I understand correctly, it's silicone tubing with 6mm internal diameter and 9mm external diameter.


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## phario

I tested (non-scientifically) adding additional tubing from pump to T fitter to opv and this seemed to have extremely minimal effect.

https://streamable.com/wg4ld3

The video is misleading because of the camera frame rate. The needle is bouncing very rapidly between the bounces and you're not seeing it. The flutter is about 0.5bars in extent.

Previously when operating this gauge I had about the same (smaller) fluttering as was observed in @ratty recent thread. Then something happened (I've no idea what) that caused a change to worsen the flutter. Air/water mix getting in? Who knows. It's tricky.

I wish I had the money/time/patience/desire to conduct a proper test.


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## Blue_Cafe

As long as you have the tap on the pump outlet, the pressure gauge will likely twitch.


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## phario

Blue_Cafe said:


> As long as you have the tap on the pump outlet, the pressure gauge will likely twitch.


 Well...haven't we established that? See the various references in the thread that have discussed the effects of the vibration pump.

Multiple people have tapped into the pump and observed different levels of vibration. So the question is whether that can be minimised and to what extent and via what factors...

I apologise as I guess I have not been writing very clearly.


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## Blue_Cafe

phario said:


> Well. Yeah.(?)
> 
> The point is that multiple people have tapped into the pump and observed different levels of vibration. And to understand whether that can be minimised and to what extent and via what factors.
> 
> I thought in my first post I gave some references that did clearly note that the vibrating pump was the main culprit.
> 
> Maybe I've not been clear enough.


 Maybe I don't read enough lol, sorry. My bad.

I like the experimental approaches. Tinkering is a dying art.


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## Norvin

This may help..

Here is a picture of my OPV setting gauge









There are two ball valves, one controlling flow out of the outlet and one controlling flow to the gauge. To use it I start with both valves open and start the pump. Once water flows out of the outlet (purging the air) i shut the valve. Pressure builds up and registers on the gauge. At this point the needle vibrates wildly, I slowly close the ball valve to the gauge and the oscillations die down and stop completely when the valve is shut. I mention this because there is a sweet spot just before the valve is closed when there is very little oscillation (and it's not a glycerine filled gauge). That may be a possible answer to the problem, find a way to restrict the size of the connection to the gauge.


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## phario

Norvin said:


> This may help..
> 
> Here is a picture of my OPV setting gauge
> 
> There are two ball valves, one controlling flow out of the outlet and one controlling flow to the gauge. To use it I start with both valves open and start the pump. Once water flows out of the outlet (purging the air) i shut the valve. Pressure builds up and registers on the gauge. At this point the needle vibrates wildly, I slowly close the ball valve to the gauge and the oscillations die down and stop completely when the valve is shut. I mention this because there is a sweet spot just before the valve is closed when there is very little oscillation (and it's not a glycerine filled gauge). That may be a possible answer to the problem, find a way to restrict the size of the connection to the pump.


 Norvin, this is excellent.

This post is maddening for the simple reason that I saw a setup where someone installed a flow limiter in a non-Gaggia machine in order to limit needle flutter and I never clocked its possible importance. In your ball valves, how small is the sweet spot? Do you envision this might be a permanent solution for built-in gauges?

By the way, regarding the theory of using the steam valve in order to reduce vibrations, this is exactly what this person does. The resultant flutter is about the same as I've seen for other pump-OPV T-fitter installs. See the video here. Based on this single video, it's not obvious that the steam gauge location fixes things.


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## FairRecycler

Nightrider_1uk said:


> I notice that everybody seems to use thin bore capillary tube for their gauge. Has anybody tried 6mm PTFE tubing?


 Good question, I think it worth to try. I'll include this one too.



Norvin said:


> Why don't you just use the spare connection on the steam valve found on the Gaggias without the OPV? It wouldn't be too difficult to remove the ball and spring and find a suitable adapter for the capilliary tube. It would then be a straight swap.
> 
> 
> View attachment 42483


 It is probably the best tapping point.

I only have one concern from a manufacturing perspective, it needs - in most cases - a new steam valve, and that's well more expensive than such a kit should be 

I was thinking of a piggyback for the steam valve, but then the cutout for the knob won't line up


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## Norvin

phario said:


> Norvin, this is excellent.
> 
> This post is maddening for the simple reason that I saw a setup where someone installed a flow limiter in a non-Gaggia machine in order to limit needle flutter and I never clocked its possible importance. In your ball valves, how small is the sweet spot? Do you envision this might be a permanent solution for built-in gauges?
> 
> By the way, regarding the theory of using the steam valve in order to reduce vibrations, this is exactly what this person does. The resultant flutter is about the same as I've seen for other pump-OPV T-fitter installs. See the video here. Based on this single video, it's not obvious that the steam gauge location fixes things.


 The sweet spot is just before the valve closes completely, so it must be pretty small. Arranging some set up where you could drill out an obstruction in the line (e.g a washer or plug) with successively larger drills will probably work. Once you find the right size, it could probably be replicated for others. You could also try pinching the capilliary tube, but that is risky.


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## Blue_Cafe

phario said:


> Norvin, this is excellent.
> 
> This post is maddening for the simple reason that I saw a setup where someone installed a flow limiter in a non-Gaggia machine in order to limit needle flutter and I never clocked its possible importance. In your ball valves, how small is the sweet spot? Do you envision this might be a permanent solution for built-in gauges?
> 
> By the way, regarding the theory of using the steam valve in order to reduce vibrations, this is exactly what this person does. The resultant flutter is about the same as I've seen for other pump-OPV T-fitter installs. See the video here. Based on this single video, it's not obvious that the steam gauge location fixes things.


 Well that's an interesting video huh.

He's pumping against a dead head in both scenes. Well, no, if it's operating correctly, he's actually pumping against the PRV setting which should be opening.

This might explain the fact that the needle at the portafilter is steady as it's essentially static.

The needle bounce might be the PRV opening and closing?


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## FairRecycler

> 14 hours ago, Blue_Cafe said:
> 
> Good idea for a thread.
> 
> As i don't like the idea of meddling with the boiler safety valves in these espresso machines, and, still can't get my head around using the PRVs to control pressure in the puck, i am looking myself at putting a pressure gauge on my Classic.
> 
> I've seen a few attempts and mostly, they all work on the principle of taking a tap from the pump discharge and mounting the capillary tubed gauge low down in the machine.
> 
> I have a few issues with this.
> 
> A) Taking the pressure tapping from the pump side of the boiler is not, i think, best practice. It exposes the gauge to the vibrations and shock from the pump and is as far away from the group head (where you want to be) as possible.
> 
> B) Capillary tubing is so small that normal flow into/out of it isn't going to happen. However, i don't think zero flow happens either. Its a dead space/void in the flow path and that's always a bad idea where hygiene or hold up is an issue. I think you will have some movements of fluid but it will be by convection, vibration etc and will be slow. Its a bug pot imho.
> 
> C) Putting the Gauge low is again a problem for the issues noted in (B) I see it is common to tee off in a manner which is not free draining, usually with the tee pointing down from the pump tap. Another sump created with a dead head.
> 
> I have looked to see how other manufacturers have added pressure gauges to their machines and how they resolve the issues noted above.
> 
> Sage, in their Dual boilers take the pressure tap on the boiler side of the system from the multiport block valve (3 way solenoid).
> 
> Here is a good video showing the guts of the DB:


 Thank you for the lot of details

A/ totally agree, this made me make the piggyback to the opv.

B+C/ Thank you for the explanation, I got it now.

Sage/ Yes the front layout allows you to do so. Lucky, unlike the Classic 

Gaggia TS/ I wouldn't mix in HX machines as those boilers half empty, or half full depending on your point of view  So tapping to the top of the boiler eliminates the water issue in the tube.

"This guy's" Classic on YouTube/

Unfortunately not many Classic in use has this old type of steam valve. 

just below that, my version:

As in that time I was stick to the water filled tube, I didn't wanted to let the hot water to the gauge as most of them not rated for such a temperature. I never thought of the cooling effect of the coils, my bad. I'll definitely try one with a sufficient coil size, tapped to a piggyback at the boiler outfeed. This would - unlike the steam valve tapping - allow a self draining system too.

Thanks again


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## phario

And since we might be in the mood for contradictory videos:






That's a dry pressure gauge mounted as close as possible to the pump with almost zero flutter I can see in the video.

Same author as the one who mounted it direct to the steam gauge with the flutter.


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## phario

L&R said:


> This thread will be a problem I don't think it is common, better to use some brass solder stick and a propane torch they are small and will be easy to be welded together.





Norvin said:


> Good idea, but for those without brazing equipment there shouldn't be a need to braze anything. There is an internal thread in the valve (1/8 BSP?), it should be possible to find a standard adapter to fit this at one end with an external thread at the other end (1/4 BSP?) to fit the capilliary tube fitting.











I took a steam valve from a Gaggia Evolution but I'm not sure what connections might be used. The previous nipple has 7mm threads while the male threads that insert into the capillary tube nut I believe is a BSP 1/8 male.


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## L&R

The idea is to braze capillary tube in the cap directly. I have done this but not putting anything just to block the exit in order to use the valve in Classic. I used a small torch w/o oxygen, a bronze stick for welding and flux.


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## FairRecycler

> 11 hours ago, phario said:
> 
> And since we might be in the mood for contradictory videos:


 Haha.

Everything is wrong with this setup, but it works like a treat.

There is also a 90° elbow at the gauge end...

The key is probably the gauge, I can't remember seeing this kind of gauge before.

In his blog he usually details every components - including the polish supplier - used in his mods.


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## FairRecycler

FairRecycler said:


> Haha.
> 
> Everything is wrong with this setup, but it works like a treat.
> 
> There is also a 90° elbow at the gauge end...
> 
> The key is probably the gauge, I can't remember seeing this kind of gauge before.
> 
> In his blog he usually details every components - including the polish supplier - used in his mods.


 One variable no-one mentioned before is the amount of air in the boiler, that highly affects the dampening of the whole system.


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## phario

FairRecycler said:


> The key is probably the gauge, I can't remember seeing this kind of gauge before.
> 
> In his blog he usually details every components - including the polish supplier - used in his mods.


 I was on the same line of thinking as you -- after I saw the video I immediately tried to source the gauge. But I don't know if the gauge is unusual. It's this one on a Polish site. You can find it on Ebay here via its code 1245001 (they also have 1245002 version). Edit: here is a version within the UK with free shipping.



L&R said:


> The idea is to braze capillary tube in the cap directly. I have done this but not putting anything just to block the exit in order to use the valve in Classic. I used a small torch w/o oxygen, a bronze stick for welding and a flux.


 I'd love to have a fitting solution that didn't require any welding. I've held off from purchasing any welding materials and tools. I guess one day I'll want to buy a torch but these things can quickly spiral out of control for the sake of a fix that might or might not work.


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## Norvin

phario said:


> View attachment 42541
> 
> 
> I took a steam valve from a Gaggia Evolution but I'm not sure what connections might be used. The previous nipple has 7mm threads while the male threads that insert into the capillary tube nut I believe is a BSP 1/8 male.


 The sizes are smaller than I remember, I should have taken more note of L&R's comment about it being a problem size. Can you or anybody else confirm whether the 7mm thread is 7mm x 1mm or 7mmx 0.75mm? (easiest to count the number of threads in 1cm and divide by 10). I have a 7mm x 1mm die so may be able to knock up an adaptor.


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## phario

Norvin said:


> The sizes are smaller than I remember, I should have taken more note of L&R's comment about it being a problem size. Can you or anybody else confirm whether the 7mm thread is 7mm x 1mm or 7mmx 0.75mm? (easiest to count the number of threads in 1cm and divide by 10). I have a 7mm x 1mm die so may be able to knock up an adaptor.


 I can do so this afternoon. It's not the easiest thing to measure, because I am not sure where to start counting. I will take a close-up picture. The thread axial length on the nipple is around 5mm (+0.2mm?) and I roughly count 7-8 threads. So I guess that would be around 10/14 = 0.71mm distance. I guess my count would need to be several threads off to be wrong but I can try and provide a picture to confirm.


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## Norvin

phario said:


> I can do so this afternoon. It's not the easiest thing to measure, because I am not sure where to start counting. I will take a close-up picture. The thread axial length on the nipple is around 5mm (+0.2mm?) and I roughly count 7-8 threads. So I guess that would be around 10/14 = 0.71mm distance. I guess my count would need to be several threads off to be wrong but I can try and provide a picture to confirm.


 The boiler and steam valve Allen screws are 6 X 1mm. Hold one against the thread on the insert and see if the threads match.


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## phario

Norvin said:


> The boiler and steam valve Allen screws are 6 X 1mm. Hold one against the thread on the insert and see if the threads match.











Here is the steam valve nipple thread (below) compared to an M6 boiler bolt (above). As I said, about 7-8 threads on a 0.5mm section. Looks to be less than the 1mm divisions on the boiler bolt I'm afraid.


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## Blue_Cafe

phario said:


> View attachment 42544
> 
> 
> Here is the steam valve nipple thread (below) compared to an M6 boiler bolt (above). As I said, about 7-8 threads on a 0.5mm section. Looks to be less than the 1mm divisions on the boiler bolt I'm afraid.


 The steam valve is likely to be a BSP tapered thread used for pressure tight fittings.

The bolt is a std Iso M6 coarse straight thread.


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## Norvin

Blue_Cafe said:


> The steam valve is likely to be a BSP tapered thread used for pressure tight fittings.
> 
> The bolt is a std Iso M6 coarse straight thread.


 Try to keep up. I've already suggested that it may be 1/8 bsp , phario stated that it was too small at 7mm diameter. I don't think that there are any bsp sizes below 1/8 bsp, perhaps you know better? 7mm threads come in two pitches, 1.0 (for which I have a die) and 0.75mm (for which I don't). To see if it was a 1.0mm pitch I advised him to compare it to an easily found bolt that also has a 1.0mm pitch. It looks like the bolt is 0.75 pitch. Gaggia has form for using non standard threads, I remember having problems identifying the thread used on the adjuster in the OPV valve.

If it was 1/8 bsp, presumably phario has already tried screwing the adaptor into the 1/8 bsp gauge fitting.

The next step for me would be to drill out and tap a 1/8 bsp thread in the valve body to suit a readily available adaptor.


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## Blue_Cafe

lol

I am just trying to be helpful

Perhaps email gaggia. They will tell you the thread.


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## FairRecycler

Norvin said:


> Try to keep up. I've already suggested that it may be 1/8 bsp , phario stated that it was too small at 7mm diameter. I don't think that there are any bsp sizes below 1/8 bsp, perhaps you know better? 7mm threads come in two pitches, 1.0 (for which I have a die) and 0.75mm (for which I don't). To see if it was a 1.0mm pitch I advised him to compare it to an easily found bolt that also has a 1.0mm pitch. It looks like the bolt is 0.75 pitch. Gaggia has form for using non standard threads, I remember having problems identifying the thread used on the adjuster in the OPV valve.
> 
> If it was 1/8 bsp, presumably phario has already tried screwing the adaptor into the 1/8 bsp gauge fitting.
> 
> The next step for me would be to drill out and tap a 1/8 bsp thread in the valve body to suit a readily available adaptor.


 I'm just wondering is this 1.0 or 0.75 pitch? I couldn't find it on the specs

NPQH-D-M7-Q6-P10

https://www.festo.com/cat/en-gb_gb/products_NPQH#


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## FairRecycler

It might be silly, but I'm trying to think out of the box

Would this trap all the water when placed near to the tapping?

Mini 1/4" AF2000-02 Air Compressor Line Water Separator Trap Water Trap Filter

https://www.ebay.co.uk/itm/383595649914


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## phario

FairRecycler said:


> It might be silly, but I'm trying to think out of the box
> 
> Would this trap all the water when placed near to the tapping?
> 
> Mini 1/4" AF2000-02 Air Compressor Line Water Separator Trap Water Trap Filter
> 
> https://www.ebay.co.uk/itm/383595649914


 Were you looking to ensure water doesn't get into the capillary?

My understanding is that these are for separating moisture from air, rather than impeding liquid systems.

By the way (not to ignore your question) but one theory I have seen proposed is that the vibrations arise due to water-air mixing in the cap tube. People have advised to use a blow torch to dry any liquid in the cap tube. I have wondered what effect might be from using the boiler to keep heat on the tube so keep it dry


----------



## Norvin

FairRecycler said:


> I'm just wondering is this 1.0 or 0.75 pitch? I couldn't find it on the specs
> 
> https://www.festo.com/cat/en-gb_gb/products_NPQH#


 Yes, they don't say, but the m7 pneumatic fittings on ebay look as if they are the coarse thread (1.0 mm).


----------



## phario

Does anybody want to run a test of the gauge with the minimal pump loop? Basically just examine a gauge and the vibration pump under some pressure.


----------



## FairRecycler

phario said:


> Does anybody want to run a test of the gauge with the minimal pump loop? Basically just examine a gauge and the vibration pump under some pressure.


 Did you meant, without any kind of chamber neither the OPV, but a single tube?


----------



## phario

FairRecycler said:


> Did you meant, without any kind of chamber neither the OPV, but a single tube?


 I think we want to minimise as many effects as possible but we'll probably want a limiter for the pressure.

So if you have a T fitter, I guess you could test the usual pump to T (to gauge) to OPV to something that blocks the flow.

Alternatively could do pump to OPV to gauge.

Basically remove as many components as possible till we understand the issue and build it back up.


----------



## phario

I realise that I may be excessively posting, but it is better to collect thoughts here rather than lose them, I suppose.

So the question here is if we can simply isolate the main needle flutter as a function of the vibration pump. Specifically, is it the case that the needle flutter is a consequence of pressure pulsations (and not, say, other mechanisms like air-liquid flow going unstable). Some additional reading from Chap. 5 of the book by Nakamura et al.



> Pulsations in piping can be reduced by various methods: installation of an orifice that adds fluid damping, adjusting piping length to change the resonance frequency, installation of a pulsation suppression device (snubber) that reduces the pulsation itself, and installation of a 1/4 wavelength branch pipe that aims to reduce a particular frequency component


 See the image below of their Table 5.7 that indicates various ways of reducing pressure-induced vibrations.















Some of the suggestions are quite interesting, and they largely relate to pre-treatment of the flow before it hits the gauge or the modification of the pump-OPV distance. Some of these recommendations seem unrealistic for the community (like those suggestions that relate to knowing exact properties), but suggestions of inserting an orifice, snubber, or side branch might be applicable.


----------



## FairRecycler

phario said:


> I think we want to minimise as many effects as possible but we'll probably want a limiter for the pressure.
> 
> So if you have a T fitter, I guess you could test the usual pump to T (to gauge) to OPV to something that blocks the flow.
> 
> Alternatively could do pump to OPV to gauge.
> 
> Basically remove as many components as possible till we understand the issue and build it back up.


 I've just bought and ordered some tools and bits needed, and made a sketch of the piggyback design for the solenoid valve. I decided to tap on the piggyback with an M5 connector, this way I can change the setup between the capillary tube and PTFE tube easily without changing any other variables.

I want to test a long (1m) PTFE tube, as I'm curious how would this 2nd "dampening chamber" affect the issue.

While I'm waiting for the bits, I'll try the above mentioned scenarios.

Ohhh I have to make up a machine first.

It looks like testing won't start before the weekend.

I'm thinking... I should start with a badly fluttering needle shouldn't I?
I bet as now I'm aiming for this, it will be still at the first time 😂😂😂

Would you guys advice to look into the pump as well? In my experience, half of the used machines I bought, came with a broken spring in the pump, but apart from 1-2 exemption they all did work happily.

I'm planning to get a flow reduction at the inlet of the piggyback (0.5mm nozzle) to reduce the flow to the gauge and also to the brew head. This would also reduce the chances of channelling.
I know it would be easier to use a valve as others did, but I'm not the fan of the idea having an in-line tap laying around in my machine.

Any pros cons on these?

Thank you
Peter


----------



## phario

FairRecycler said:


> Would you guys advice to look into the pump as well? In my experience, half of the used machines I bought, came with a broken spring in the pump, but apart from 1-2 exemption they all did work happily.
> 
> I'm planning to get a flow reduction at the inlet of the piggyback (0.5mm nozzle) to reduce the flow to the gauge and also to the brew head. This would also reduce the chances of channelling.
> I know it would be easier to use a valve as others did, but I'm not the fan of the idea having an in-line tap laying around in my machine.


 All interesting ideas, Peter.

I know you prefer non-inline examples, but what are examples of inline flow limiters?

The pump issue is interesting. I did a very non-scientific test of putting the gauge into both a machine running the older orange Invensys pumps and the newer Ulka pumps (though both old machines) and I did not see much difference. What I have read though is that the Invensys pumps are slightly quieter (see this video: 



 Ulka at 80 dB and Invensys at 77 dB). There are various threads about people trying to reduce vibrations on the pumps by tying them in different places.

However, when I did my (poor!) test, I had a suspicion that gauge vibration was not because of object vibration, i.e. it doesn't much matter how you hold the pump or hold the gauge. It is coming from within the flow itself.

The other thing to keep in mind when doing a test is that I think a major issue with initial gauge vibration is air in the tubes. The test needs to be run a number of times and the vibration tested as the air begins to evacuate from the system. I do not know if there is a way to vent the air on the very first press of the button!

So long story short, in my view, there is not much advantage to trying different pumps. The key issues seem related to flow quality, and at least in my tests, these were replicated over the two different pumps I had.


----------



## Norvin

Norvin said:


> The sweet spot is just before the valve closes completely, so it must be pretty small. Arranging some set up where you could drill out an obstruction in the line (e.g a washer or plug) with successively larger drills will probably work. Once you find the right size, it could probably be replicated for others. You could also try pinching the capilliary tube, but that is risky.


 Following on from this idea. I've just come across this: https://ashcroft.com/productinformation_pdf/upload/pip-ash-pi-7b-gauge-throttle-plug-selection.pdf

You can buy throttle plugs or screws to vary the size of the orifice, it seems some already have throttle plugs built in.


----------



## phario

In a PM I mentioned to @FairRecycler that we should take care not to assume that the liquid filled gauges are free from defects and to ascribe vibrations to the system rather than the gauge (this has largely been what we have done---trying to diagnose the system rather than consider if the gauge is, itself, the culprit).

To that end, here is a cheap dry gauge, mounted direct to the pump-to-OPV line with almost no vibration perceptible to the eye.

https://streamable.com/0ixshv

This is the same gauge I mentioned in my "contradictory" post:

https://www.coffeeforums.co.uk/topic/53171-pressure-gauge-discussion-experiment-improvement/?do=embed&comment=757635&embedComment=757635&embedDo=findComment

Additional details for my reference:



The liquid-filled gauges linked in the original post has hole diameter 41mm but requires about 37mm of space behind the gauge when you install it into the Gaggia case. This means you have to be careful with rear clearance to the boiler.


The gauge above is linked here but I have not been able to find a Chinese supply source (as you would expect there to be). The necessary case hold diameter is marginally smaller, at 40.6mm, but it has the advantage of much less needed rear clearance, and you only need about 30mm of space behind.


----------



## Agentb

I've been following this thread with interest.👍



phario said:


> Some of the suggestions [to damp vibrations] are quite interesting, and they largely relate to pre-treatment of the flow before it hits the gauge or the modification of the pump-OPV distance. Some of these recommendations seem unrealistic for the community (like those suggestions that relate to knowing exact properties), but suggestions of inserting an orifice, snubber, or side branch might be applicable.


 This reminded me of pre-heater mods where a coil of tubing was wrapped around the boiler or a little pre-heater sump installed. You could easily modify the diameter, length or composition of the pump-OPV and see what effect on damping out the vibrations. 👍

edit: if the pressure is fluctuating - isn't that something you would want to see on the gauge?


----------



## phario

Agentb said:


> edit: if the pressure is fluctuating - isn't that something you would want to see on the gauge?


 Funny. My partner asked me this exact question.

The pressure is not fluctuating in the way you think. It's like using a flag to measure wind speed. You'll measure it with respect to whether the flag is largely flat (0 degrees) or 90 degrees. But you don't necessarily want a wind speed reading that is fluctuating 31.3, 29.8, 32.2, etc because the flag is fluttering. You have some notion of wind variation and you don't want variations on the order of fractions of seconds.

You might argue that this 'fluttering' is part of the wind, or you might say that the wind has caused this fluttering to appear. You can also consider how designing a stiffer flag might get rid of it. Or maybe some sort of funnel to channel the wind before it reaches the flag.

Here, the pressure guage is vibrating because there is a secondary instability. It's hard to say if this is part of the flow or part of the gauge construction.


----------



## Agentb

From memory the Classic i think mostly uses the Ulka EP5 Vibration pump, and these are a simple back and forward piston - so we should expect flutter if a pressure gauge is working properly.



phario said:


> It's hard to say if this is part of the flow or part of the gauge construction.


 Maybe some ways to tell. Record in slow motion the gauge and the audio, if it vibrates with the same frequency as the motor - we can presume it is motor related.

If there is no pressurized water flow, or you use some other method to pressurize the gauge - does it flutter when the motor is running? (some pump vibration rattling the needle).

Introducing damping to hide oscillations in pressure means you will lose pressure oscillation information.

Introducing damping upstream to provide a steadier flow (i presume this would be a good thing ?) would not be visible on such a damped gauge.


----------



## phario

Agentb said:


> From memory the Classic i think mostly uses the Ulka EP5 Vibration pump, and these are a simple back and forward piston - so we should expect flutter if a pressure gauge is working properly.


 Did you see the most recent videos I showed of the zero-flutter gauge? Would you say that this gauge is accurate or inaccurate?

I don't really agree with your statement. Let's try and be a bit more specific.

Suppose that the pump produces a pressure with a certain deviation. So let's say that, it produces a pressure signature that looks like this:



> p(t) = 10 bars + A*cos(wt)


 so essentially a mean value of 10 with some deviation measured by a frequency w. You can imagine that, as a function of the complicated pipes and other things, the above function has extra errors in it (more oscillations). But let's just imagine a single one for simplicity. In general, this signal is then fed to the pressure gauge. However, it's not obvious at all that within the pressure gauge, it would display the same formula above:



> p(t) = 10 + A*cos(wt)


 which is what you're asking (about whether an 'accurate' gauge can go on to replicate exactly the flutters generated by the pressure pump).

It could be that the pressure gauge is poorly constructed. Consequently, the lone oscillation above tends to excite other vibrations. For example, within the pressure gauge, you then see this:



> p_gauge(t) = 10 + A*cos(wt) + 10*A*cos(10*w*t)


 in other words, the construction of the gauge has caused an instability that produces another ripple---this one at 10 times the frequency of the original. It is technically correct to say that the secondary ripple emerges as a function of the pump. However, the point is that the construction of the gauge can serve to eliminate either the primary or secondary flutter. You can think of pre-treating the flow (possibly piping it differently, inserting chambers, changing the pump, etc.) as decreasing the value of 'A' that is then fed to the gauge. However the gauge may itself do something with this value (amplify it and produce additional oscillations).

The example I gave of the wind hitting the flag is apt. Did you consider that? Imagine wind that occurs at high velocity hitting a flag. say at 50km/h. Because of the amplification of noise, the flag ripples wildly. This ripple may not be necessarily present in the wind itself. It may be something that is essentially produced because of the flag's construction and the circumstances that lead to the interaction.

Returning to the original discussion I think this is neither here nor there. The point is that aesthetically, we would like a gauge that shows the average pressure, as well as any slow swings. We don't want a gauge that vibrates wildly. Whether or not it is technically 'accurate' is besides the point.

Thanks for the interesting discussion


----------



## Agentb

phario said:


> Did you see the most recent videos I showed of the zero-flutter gauge? Would you say that this gauge is accurate or inaccurate?
> 
> I don't really agree with your statement.


 I did see the video, i would say the plumbing added was different to other videos, (probably also a different meter) and it looks to be measuring pressure further away from the flow. How can i say it is inaccurate or accurate. If that's the gauge you want go get it!👍

As you don't agree with my convoluted statement .. i know you're not arguing about what pump is in the Gaggia, so i guess it is the next bit "we should expect flutter if a pressure gauge is working properly"

I'm sure you have looked into the construction of a vibratory pump (a solitary piston). I'll assume you agree with me that the pump generates oscillating pressure. If you think it is constant, then this is a sticking point - it will be easy for you to research and test. In fact it would help know exactly what the frequency and shape is, as it would help to achieve some of the other suggestions. I'd be surprised if it is constant, but happy to be proven wrong.

You seem to be concerned there are phantom oscillations caused by other things, and this may be true, but until you put gauges to the test you have to assume gauges do what they claim to do. A pressure gauge measures pressure (where it is connected), and if the pressure profile is ugly you would like it to show as ugly 

All that's left, i can see is the discussion about introducing plumbing between the flow and the gauge to dampen these oscillations, or use a gauge which is less sensitive and slower to respond to them - for aesthetic reasons. The flow pressure oscillations are still there, if you don't want to see them that's fine - but i do - i guess you and i differ in our requirements. 😸

All i'm saying is perhaps better to introduce plumbing to reduce flow oscillations - rather than reduce needle oscillations, then your needle AND flow will be more aesthetically and functionally pleasing. 

A similar argument might be i don't like my PID showing 0.1 degree fluctuations - to stop that i'm going to move the thermostat 2mm away from the boiler and wrap it in insulating material. It looks more stable, but a better solution would for example be perhaps insulate the boiler.

👍


----------



## phario

Agentb said:


> I did see the video, i would say the plumbing added was different to other videos, (probably also a different meter) and it looks to be measuring pressure further away from the flow


 I did the experiment with a few different piping length arrangements. Also different resting arrangements.



Agentb said:


> If you think it is constant, then this is a sticking point - it will be easy for you to research and test.


 I don't think I ever stated that...

Anyways, I think that's all. There's not much more to say to be honest. I did my best to explain the theory as I understand it.

Thanks for the discussion.


----------



## Blue_Cafe

Agentb said:


> I did see the video, i would say the plumbing added was different to other videos, (probably also a different meter) and it looks to be measuring pressure further away from the flow. How can i say it is inaccurate or accurate. If that's the gauge you want go get it!👍
> 
> As you don't agree with my convoluted statement .. i know you're not arguing about what pump is in the Gaggia, so i guess it is the next bit "we should expect flutter if a pressure gauge is working properly"
> 
> I'm sure you have looked into the construction of a vibratory pump (a solitary piston). I'll assume you agree with me that the pump generates oscillating pressure. If you think it is constant, then this is a sticking point - it will be easy for you to research and test. In fact it would help know exactly what the frequency and shape is, as it would help to achieve some of the other suggestions. I'd be surprised if it is constant, but happy to be proven wrong.
> 
> You seem to be concerned there are phantom oscillations caused by other things, and this may be true, but until you put gauges to the test you have to assume gauges do what they claim to do. A pressure gauge measures pressure (where it is connected), and if the pressure profile is ugly you would like it to show as ugly
> 
> All that's left, i can see is the discussion about introducing plumbing between the flow and the gauge to dampen these oscillations, or use a gauge which is less sensitive and slower to respond to them - for aesthetic reasons. The flow pressure oscillations are still there, if you don't want to see them that's fine - but i do - i guess you and i differ in our requirements. 😸
> 
> All i'm saying is perhaps better to introduce plumbing to reduce flow oscillations - rather than reduce needle oscillations, then your needle AND flow will be more aesthetically and functionally pleasing.
> 
> A similar argument might be i don't like my PID showing 0.1 degree fluctuations - to stop that i'm going to move the thermostat 2mm away from the boiler and wrap it in insulating material. It looks more stable, but a better solution would for example be perhaps insulate the boiler.
> 
> 👍


 Technically, a good reply and I agree.

I don't like the idea of measurement at the pump so far away from the puck. Too much noise in the way


----------



## FairRecycler

phario said:


> trying to diagnose the system rather than consider if the gauge is, itself, the culprit)


 And it is confirmed there is an orifice of 1.0mm on my gauges, which is miles away the desired diameter.

If anyone knows an affordable machinist who turns and mills as well please PM me.



phario said:


> I know you prefer non-inline examples, but what are examples of inline flow limiters


 As seen on this or on @rattys topic inline taps/valves been used to reduce flow.



phario said:


> However, when I did my (poor!) test, I had a suspicion that gauge vibration was not because of object vibration, i.e. it doesn't much matter how you hold the pump or hold the gauge. It is coming from within the flow itself.


 I can't see it's caused by object vibration as my piggyback version should not suffer of that, being bolted to the brew group (well it's only an assumption , but I can't see much chance for that)



Norvin said:


> Following on from this idea. I've just come across this: https://ashcroft.com/productinformation_pdf/upload/pip-ash-pi-7b-gauge-throttle-plug-selection.pdf
> 
> You can buy throttle plugs or screws to vary the size of the orifice, it seems some already have throttle plugs built in.


 Wow that's a great one. I thought the 0.5mm orifice will be sufficient, but according to this I should go down to 0.15mm with an air "filled" capillary tube.

Good job I've just finished the 0.5mm piggyback 

@phario I have a few good reason to stick with the gauges I'm using now, like build quality (full stainless steel body), aesthetics (streamlined professional look)

I admit the gauge you linked could work 10/10 times out of the box, but that chrome effect plastic screams at it's designer, no mention of the stickout at the front. I would rather do the extra mile to sort the 41.3mm one out. Obviously it's my personal preference.


----------



## phario

FairRecycler said:


> I admit the gauge you linked could work 10/10 times out of the box, but that chrome effect plastic screams at it's designer, no mention of the stickout at the front. I would rather do the extra mile to sort the 41.3mm one out. Obviously it's my personal preference.


 To be completely honest, I bought the second gauge because I was intending to steal the capillary gauge and bracket, then spend £5-6 or whatever it was to get the liquid-filled ones...only to discover that the rear nut of my recent one can't obviously be threaded into the rear of the liquid-filled ones. Dear lord. It never ends. By the way, I just tried and a magnet sticks to the outer chrome casing, so it is apparently some sort of thin metal. That said, I agree it does not look as good and professional (and it seems much lighter).

Just to be clear, I'm not here to try and convince anyone to take one gauge over the other or to peddle any particular product.

I think the intention of this thread was to discuss the mechanisms behind the vibrations. I'm providing the links to the product because I thought it would be useful for people as a reference point.


----------



## FairRecycler

Agentb said:


> I did see the video, i would say the plumbing added was different to other videos, (probably also a different meter) and it looks to be measuring pressure further away from the flow. How can i say it is inaccurate or accurate. If that's the gauge you want go get it!👍
> 
> As you don't agree with my convoluted statement .. i know you're not arguing about what pump is in the Gaggia, so i guess it is the next bit "we should expect flutter if a pressure gauge is working properly"
> 
> I'm sure you have looked into the construction of a vibratory pump (a solitary piston). I'll assume you agree with me that the pump generates oscillating pressure. If you think it is constant, then this is a sticking point - it will be easy for you to research and test. In fact it would help know exactly what the frequency and shape is, as it would help to achieve some of the other suggestions. I'd be surprised if it is constant, but happy to be proven wrong.
> 
> You seem to be concerned there are phantom oscillations caused by other things, and this may be true, but until you put gauges to the test you have to assume gauges do what they claim to do. A pressure gauge measures pressure (where it is connected), and if the pressure profile is ugly you would like it to show as ugly
> 
> All that's left, i can see is the discussion about introducing plumbing between the flow and the gauge to dampen these oscillations, or use a gauge which is less sensitive and slower to respond to them - for aesthetic reasons. The flow pressure oscillations are still there, if you don't want to see them that's fine - but i do - i guess you and i differ in our requirements. 😸
> 
> All i'm saying is perhaps better to introduce plumbing to reduce flow oscillations - rather than reduce needle oscillations, then your needle AND flow will be more aesthetically and functionally pleasing.
> 
> A similar argument might be i don't like my PID showing 0.1 degree fluctuations - to stop that i'm going to move the thermostat 2mm away from the boiler and wrap it in insulating material. It looks more stable, but a better solution would for example be perhaps insulate the boiler.
> 
> 👍


 I see what do you mean, and as it has been discussed earlier, it is really important to tap to the right place to allow the gauge represent the actual brew pressure instead of the "ugly pressure" coming from the pump. On the other hand we also aiming to make the actual pressure readable. Silly example I know but I think it is a good one. Your car has a numerical speedometer and obviously you want to know your actual speed exactly, but the meter rounds the value, as showing your actual speed with 4 decimal point accuracy would be confusing and unreadable. As the pressure gauge is analog, we can't round it, hence the aim for dampening.


----------



## FairRecycler

phario said:


> only to discover that the rear nut of my recent one can't obviously be threaded into the rear of the liquid-filled ones.


 Just cut it off and solder them back together. I don't mind doing that for you. Obviously I have the liquid filled one on shelf too.


----------



## phario

FairRecycler said:


> Just cut it off and solder them back together. I don't mind doing that for you. Obviously I have the liquid filled one on shelf too.


 I appreciate the offer, Peter. 😬

Some days I think it's easier just to jump in my car and drive the 2.5 hrs to Loughborough and just have you do it for me from the get go!

Anyways, it wasn't a terrible experiment. I'll be pleased to ship back the shock_waves gauge for a refund, despite the £5 loss or whatever it costs.


----------



## FairRecycler

The boiler infeed and boiler outfeed piggybacks ready to test.

This morning I'll get a machine done and start this test.

It's not a fair comparison as in the outfeed version there is a 0.5mm orifice as well to reduce the brew flow (I wanted to try it for so long), I'm hoping to get good results with that setup. I left the length of the capillary tube similar for now.

I'm struggling to source push fittings for the PTFE tube version (which I believe to be a great solution) as not many fittings standing both 10-15bars and 150°C.

I found these, but they're sold in a box of 10 or 100. Iv tried several resellers and FESTO UK too with no joy 

QSF-1/8-6-B-100

NPFC-R-G18-M5-MF

NPQH-D-M5-Q6-P10

NPQH-D-M5-S6-P10

NPFC-R-G18-M5-FM

MA-40-16-1/8-EN-DPA

If anyone has a clue on getting 1 of each, that would be great.


----------



## phario

The other question is that I've wondered exactly how hot the pump to OPV water gets. A simple experiment would be to just measure the OPV ejection. It can't be any hotter than that. The point I'll make is that the pump is not rated for hot water. I doubt it gets higher than 100C but it would be good to know so we can choose the tubing accordingly.

I'm unreasonably excited to see your test. I hope it sheds light.


----------



## Blue_Cafe

FairRecycler said:


> The boiler infeed and boiler outfeed piggybacks ready to test.
> 
> This morning I'll get a machine done and start this test.
> 
> It's not a fair comparison as in the outfeed version there is a 0.5mm orifice as well to reduce the brew flow (I wanted to try it for so long), I'm hoping to get good results with that setup. I left the length of the capillary tube similar for now.
> 
> I'm struggling to source push fittings for the PTFE tube version (which I believe to be a great solution) as not many fittings standing both 10-15bars and 150°C.
> 
> I found these, but they're sold in a box of 10 or 100. Iv tried several resellers and FESTO UK too with no joy
> 
> QSF-1/8-6-B-100
> 
> NPFC-R-G18-M5-MF
> 
> NPQH-D-M5-Q6-P10
> 
> NPQH-D-M5-S6-P10
> 
> NPFC-R-G18-M5-FM
> 
> MA-40-16-1/8-EN-DPA
> 
> If anyone has a clue on getting 1 of each, that would be great.
> 
> View attachment 42956
> 
> 
> View attachment 42957


 Fantastic work


----------



## FairRecycler

phario said:


> The other question is that I've wondered exactly how hot the pump to OPV water gets. A simple experiment would be to just measure the OPV ejection. It can't be any hotter than that. The point I'll make is that the pump is not rated for hot water. I doubt it gets higher than 100C but it would be good to know so we can choose the tubing accordingly.
> 
> I'm unreasonably excited to see your test. I hope it sheds light.


 By experience it's around room temperature.

Why is it unreasonable??? 😅😅

At this point I'm not too keen on shedding lights light, but promising results. The amount of time in this project makes me feel, I'm aiming for something impossible... I want that baby with no more labor. 😂😂

Yes I do know it doesn't work like that, but the amount of research on applicable push fittings with no joy (knowing I found them, but those not for sale individually), did put me off a bit.


----------



## FairRecycler

@Blue_Cafe

Thank you


----------



## FairRecycler

The reason I really wanted to try PTFE tubing is the impact of a self draining tapping. In my understanding no matter how vertical the tapping is while using capillary tube, as the capillary action will beat gravity with water in a 1.0mm ID tube.

Due to the difficulties I faced sourcing fittings for this approach, I thought I could try to solder in a 6mm OD copper tube into the piggyback vertically, and at the boiler top height I solder in a 2mm capillary tube into the end of the 6mm tube leading to the gauge. In my understanding this would make a practically self draining system. Also with the benefits of a second chamber, and Vvertical tube(12cm)=1.5cm3 related to a 25cm 2mm OD 1mm ID capillary tube with V=0.2cm3, in theory water will have no chance to enter the capillary tube.


----------



## FairRecycler

It's not the luckiest pick of a machine I suppose...


----------



## Agentb

FairRecycler said:


> If anyone has a clue on getting 1 of each, that would be great.


 Just a clue - but they do sell singles.

Eg.

https://www.rowse-pneumatics.co.uk/festo-npfc-r-g18-m5-fm-8030314.html

👍


----------



## Blue_Cafe

FairRecycler said:


> It's not the luckiest pick of a machine I suppose...
> 
> View attachment 42967


 How you gonna get them studs out?

Stud extraction?

Asking because some idiot in Gaggia thinks Galv bolts are a good idea in a portafilter...


----------



## ChilledMatt

Blue_Cafe said:


> How you gonna get them studs out?
> Stud extraction?
> 
> Asking because some idiot in Gaggia thinks Galv bolts are a good idea in a portafilter...


Yeah...what do Gaggia know?

Sent from my SM-A705FN using Tapatalk


----------



## FairRecycler

They are soaking in AC-90 a while ago and I keep tapping them with a hammer every now and then. I've just finished cleaning everything else apart from the shell. Once I'm done with that I'll give it a go with some heat.

Thanks God I have only seen this once before, but the stud came out nicely after soaking and tapping that time. It won't be the case this time I'm afraid.

I'm not sure what would be a good solution, as the stainless bolts (what I'm using) will suffer from galvanic corrosion there by time, I believe.

I'm not the friend of stud extractors, once I broken one in, it only took me a full day to get it out...

If no joy with heat, I'll drill them out


----------



## FairRecycler

Agentb said:


> Just a clue - but they do sell singles.
> 
> Eg.
> 
> https://www.rowse-pneumatics.co.uk/festo-npfc-r-g18-m5-fm-8030314.html
> 
> 👍


 Thanks for this, you right here, they sell most of them individually.

Will order them later on.


----------



## phario

FairRecycler said:


> The reason I really wanted to try PTFE tubing is the impact of a self draining tapping. In my understanding no matter how vertical the tapping is while using capillary tube, as the capillary action will beat gravity with water in a 1.0mm ID tube.
> 
> Due to the difficulties I faced sourcing fittings for this approach, I thought I could try to solder in a 6mm OD copper tube into the piggyback vertically, and at the boiler top height I solder in a 2mm capillary tube into the end of the 6mm tube leading to the gauge. In my understanding this would make a practically self draining system. Also with the benefits of a second chamber, and Vvertical tube(12cm)=1.5cm3 related to a 25cm 2mm OD 1mm ID capillary tube with V=0.2cm3, in theory water will have no chance to enter the capillary tube.


 I really like the expansion idea though. Are you imagining a similar expansion chamber to what we discussed--which then feeds to the cap tube?


----------



## FairRecycler

FairRecycler said:


> but the stud came out nicely after soaking and tapping that time. It won't be the case this time I'm afraid.


 And all 3 did came out without heating.

Happy day


----------



## phario

FairRecycler said:


> And all 3 did came out without heating.
> 
> Happy day
> 
> View attachment 42976


 Get that experiment done!


----------



## Blue_Cafe

FairRecycler said:


> And all 3 did came out without heating.
> 
> Happy day
> 
> View attachment 42976


 Great to hear.

I'll be doing this myself although my stud broke below the surface


----------



## FairRecycler

phario said:


> Get that experiment done!


 Haha, There are a few things I don't do and rushing is definitely one of them. 

the group head is in soak now and I'm just about to start to the fun part of the boiler:



Blue_Cafe said:


> Great to hear.
> 
> I'll be doing this myself although my stud broke below the surface


 Ohhh that's a bad one. Good luck with that. Are you going to use an extractor?


----------



## Blue_Cafe

FairRecycler said:


> Haha, There are a few things I don't do and rushing is definitely one of them.
> 
> the group head is in soak now and I'm just about to start to the fun part of the boiler:
> 
> Ohhh that's a bad one. Good luck with that. Are you going to use an extractor?


 Ha. Dunno. It's gonna be a small one and they are brittle at the best of times.

WD40, light heat, a small drill hole and a drift punch is my current plan.

Probs be followed by swearing and a new portafilter but we can only try!


----------



## FairRecycler

I've done the first test. I thought as there are 2 separate piggybacks I can install both at the same time.

My former kit on the right (piggyback on OPV/boiler infeed) 10" 1mm ID air filled straight capillary tube. Little bit of fluttering.

Piggyback on Solenoid valve with 0.5mm orifice at boiler outfeed to reduce flow to gauge and also to the brew group. 10" 1mm ID air filled straight capillary tube. No flutter at all.

https://streamable.com/v1tdyc

So tapping on boiler outfeed definitely helps, thank you for everyone suggesting this.

Tomorrow I'm willing to test the infeed tapping only to see how the flow reduction impacts that end, if it does.

I'll also test the water filled tubes.

And swap the instruments too to ensure the difference isn't in the gauge itself.

Later on tonight I'll order the push fittings to test with the PTFE too.

A longer capillary tube test is on the list too.

Shall I get the brew group out and check the results with the gauge level simulating the panel mount versions?

I'm still uploading it, unfortunately from my phones internet connection, so it might takes a little while to become available.


----------



## phario

Still waiting for that video to show Peter, but did you try switching the piggyback so the smaller orifice was on the other one?


----------



## FairRecycler

phario said:


> Still waiting for that video to show Peter, but did you try switching the piggyback so the smaller orifice was on the other one?


 There is only 1 orifice on the solenoid piggyback, and that isn't on the tapping, but on the main flow, just before the tapping. I can't swap them as the piggybacks not interchangeable.

It is around 60% now, really really slow


----------



## Blue_Cafe

FairRecycler said:


> I've done the first test. I thought as there are 2 separate piggybacks I can install both at the same time.
> 
> My former kit on the right (piggyback on OPV/boiler infeed) 10" 1mm ID air filled straight capillary tube. Little bit of fluttering.
> 
> Piggyback on Solenoid valve with 0.5mm orifice at boiler outfeed to reduce flow to gauge and also to the brew group. 10" 1mm ID air filled straight capillary tube. No flutter at all.
> 
> https://streamable.com/v1tdyc
> 
> So tapping on boiler outfeed definitely helps, thank you for everyone suggesting this.
> 
> Tomorrow I'm willing to test the infeed tapping only to see how the flow reduction impacts that end, if it does.
> 
> I'll also test the water filled tubes.
> 
> And swap the instruments too to ensure the difference isn't in the gauge itself.
> 
> Later on tonight I'll order the push fittings to test with the PTFE too.
> 
> A longer capillary tube test is on the list too.
> 
> Shall I get the brew group out and check the results with the gauge level simulating the panel mount versions?
> 
> I'm still uploading it, unfortunately from my phones internet connection, so it might takes a little while to become available.


 Super news. If this is repeatable, you can see why Sage does it this way for the DB.

I was thinking about the dead space on the right of your panel.

I think it would be a great place to put a pressure control knob. Simple enough really, you are at a high point in the system for free draining, and your divert water is easily ported to the reservoir.

As a bonus, you could keep the safety valve untouched as it should be.

Yours would be a temp and pressure controllable device done properly and with no hacks where they don't belong.

Not quite sure how you would do the pcv 'ing to best suit. You could do the OPV dump route using an panel mounted valve. You could add a flow control valve on the pump outlet and panel mount that. You could use the DC power for a solenoid actuator system, etc.

I had a look for a panel mounted, 1/4", knobbed pcv but didn't see anything !


----------



## FairRecycler

@Blue_Cafe

Also, once it's proven to be repeatable, the next challenge is to adopt good results to the lower mounted gauge scenario, for those whom still prefer to mount the gauge into the machine.

Thank you for the idea, as I mentioned on the BoostBox topic, I'm not planning to include more features in the first version, however I'm working on a microcontroller - actually a good friend of mine does, as I don't now much about these - we thought the pressure regulation should be done by a triac generating PWM signal to drive the pump.

Any thoughts on that would be appreciated too.

Is there any particular reason not to reduce the flow to the brew group? I think it reduces the chance of channelling, however I haven't pulled a shot with it yet - I prefer to hook up the PID first to let me compare it, with my machine - are there any cons of flow reduction?

Any suggestions on food grade PTFE tubing? What I found is way more expensive than I thought initially.

I'm still looking for an affordable machinist to outsource the piggyback and to make a coupler for the gauge for the PTFE tubed version.


----------



## phario

FairRecycler said:


> we thought the pressure regulation should be done by a triac generating PWM signal to drive the pump.


 I guess there are plenty of topics on either Classic or Silvia Arduino modifications so it's more a case of finding the right sources?



FairRecycler said:


> Is there any particular reason not to reduce the flow to the brew group? I think it reduces the chance of channelling, however I haven't pulled a shot with it yet - I prefer to hook up the PID first to let me compare it, with my machine - are there any cons of flow reduction?


 It's not entirely obvious to me what is the effect, and I actually do wonder if your outlet modification changes the flow rate significantly. Can you do an experiment and measure the flow rate using your outlet and without the outlet? I guess in theory you would need to restrict the flow (with coffee grounds) but the experiment is worth doing in both cases of unrestricted flow (just shower screen) and restricted for the below reasons.

This is a very useful image presented in this article, though I do not know if these numbers are made up. Anyways, P_i corresponds to the pressure at different points and R_i corresponds to the size of different orifices. Notice that R_v (at the puck) is changing. That's because as the coffee bed wettens, the flow becomes increasingly restricted.









Basically, in relation to your question:



Your small orifice will change the pressure profile and flow rates mid-way through the cycle (wetting, pre-infusion stages).


At steady state (infusion/extraction) it shouldn't matter as much (see quote below). This is the state where the pressure is pretty much the same everywhere in the system.


From the article:



> The last restriction of flow in the machine is really the only one that counts: The coffee filter bed.* It's much lower flow rate reduces the effect of upstream orifices to near zero. If the flow of through the puck is too great, the upstream orifices will come into play and lower pressure in the brew chamber. *This is why, in the diagram below, the restriction of the puck is V (variable). Ensuring consistent quantities, particle sizes and distribution is the single most important factor in espresso quality.


 So basically, your flow limiter may have an impact on the wetting or pre-infusion stages, with more minimal effects as the coffee bed reaches its wetted state. This is why I suggested measuring unrestricted and restricted flow rates. It might be, for example, that you find out that the unrestricted (no coffee) flow rate is different, but the restricted (coffee) flow rate is largely the same.


----------



## FairRecycler

Swapped the gauges, I'm glad it didn't change the result 

https://streamable.com/w9j9by


----------



## Blue_Cafe

FairRecycler said:


> Swapped the gauges, I'm glad it didn't change the result
> 
> https://streamable.com/w9j9by


 Both look ok tbh.

I think you have cracked it!


----------



## FairRecycler

Blue_Cafe said:


> Both look ok tbh.
> 
> I think you have cracked it!


 Thanks but I don't think I'm there yet. Probably my phones camera helps smoothening the results. The boiler infeed is fluttering a tiny bit, but you need to go quite close to notice.

Today I checked the water filled tubes and the boiler infeed on its own so without the orifice. These all shown identical results still needle on the boiler outfeed, and very tiny fluttering on the boiler infeed.

I'm in the process of replacing the 10" capillary tubes to 40" ones to get sufficient cooling, and to route it in a manner to avoid water and air mixed when the gauge is mounted into the machine.

I should have started with the long ones to be fair, it would be easier to cut them to size and only solder the gauge end. Too late now 

I'm looking forward receiving the bits for the PTFE tubed version. It looks like I found a machinist locally, I'll try to see them tomorrow with the drawings.


----------



## FairRecycler

Both soldered up, and I also played with routing options, might going to need even longer tubes. Ready to test these in the morning.


----------



## phario

@FairRecycler

Here is a little calculation that will help (I mean no offense if you already know this).

If you assume that within the capillary tube, the only two significant forces are surface tension or gravity, then you can estimate the liquid rise using a simple formula relating the height of the rise, 'h' with the radius of your tube, 'r'. Reference.

h = 2*sigma*cos(theta)/(rho*g*r)

We can use (I took numbers at 60deg C):



> g = 9.8 m/s^2
> r = 1mm (I think you use half this)
> sigma = 6.62 10^-2 N/m
> rho = 0.98 10^3 kg/m^3
> theta = pi/4*


 This gives a rise of about 0.0097m or only 1cm.

*The contact angle is really quite a difficult parameter to estimate, as it depends on temperature, surface, and surface treatment. I've used around the 52 degrees that is noted by this paper.

Anyways, the point of this is to just note that the rise you can expect is generally going to be very small. Making the capillary tube thinner has the effect of making the rise higher (because surface tension is stronger). This seems counterintuitive (since you think thinner = better). However, it does not take in account the fact that a thinner tube makes it more difficult for liquid to enter in the first place.

I should say that, if there is liquid entering into the capillary tube, it's not clear to me how this would be estimated off the back of the envelope since it's a pretty hard problem. There are also forces in addition to surface tension and gravity. This includes pressure induced by the pump and also forces induced by temperature differences (convection).


----------



## Blue_Cafe

I have to say that the level of diy'ery in this thread is amazing. (from all involved). The Brass block manifold is by far my favorite mod on the classic i have seen to date. Its such a clean, well thought out idea. 

Keep going!


----------



## FairRecycler

@phario

Thanks for this.

It's a very good explanation.

I'm hoping I won't have to worry about this too much with the PTFE tubed version.


----------



## Blue_Cafe

FairRecycler said:


> @phario
> 
> Thanks for this.
> 
> It's a very good explanation.
> 
> I'm hoping I won't have to worry about this too much with the PTFE tubed version.


 I am rather hoping the larger bore dampens down the whole thing. I look forward to the results!


----------



## FairRecycler

I think I found a major issue according to constant ID (either 1 capillary tube, or 1 PTFE tube) routing for machine mount (only applies to dry tubing)

My very limited memories from school throwing me random things. Here is Boyle's law: p1*v1=p2*v2. 10 bar pressure will compress the air in the tube to 1/10 of the tube's volume, so in a 40" tube I'll have 4" compressed air (preferably at the gauge end) and 36" fluid. When the applied pressure is relieved the air is willing to expand to its former volume (ignore temperature at this point), however - warning rough assumption here - due to the capillary action it is likely to trap some fluid in the tube surrounded by air. At the next cycle these "teardrops" would probably cause issues.

I think this is the point where we would need self draining to help us out, however as @phario explained, gravity won't suffice in a 1mm ID capillary tube, but will it be sufficient in the 4mm ID.

So in my understanding I should make a vertical chamber 6-8-10mm ID from the piggyback to the highest possible point, the aim is to make this "chamber's" volume larger than 90% of the entire tubing and to get it self drain when the applied pressure relieved. At the highest point where water should never reach I connect a capillary tube 1mm ID, as short as possible - in order to keep the added volume below 10%. This way it shouldn't matter how I route from here.

I'm hoping the water filled PTFE tube will work fine.


----------



## Blue_Cafe

FairRecycler said:


> I think I found a major issue according to constant ID (either 1 capillary tube, or 1 PTFE tube) routing for machine mount (only applies to dry tubing)
> 
> My very limited memories from school throwing me random things. Here is Boyle's law: p1*v1=p2*v2. 10 bar pressure will compress the air in the tube to 1/10 of the tube's volume, so in a 40" tube I'll have 4" compressed air (preferably at the gauge end) and 36" fluid. When the applied pressure is relieved the air is willing to expand to its former volume (ignore temperature at this point), however - warning rough assumption here - due to the capillary action it is likely to trap some fluid in the tube surrounded by air. At the next cycle these "teardrops" would probably cause issues.
> 
> I think this is the point where we would need self draining to help us out, however as @phario explained, gravity won't suffice in a 1mm ID capillary tube, but will it be sufficient in the 4mm ID.
> 
> So in my understanding I should make a vertical chamber 6-8-10mm ID from the piggyback to the highest possible point, the aim is to make this "chamber's" volume larger than 90% of the entire tubing and to get it self drain when the applied pressure relieved. At the highest point where water should never reach I connect a capillary tube 1mm ID, as short as possible - in order to keep the added volume below 10%. This way it shouldn't matter how I route from here.
> 
> I'm hoping the water filled PTFE tube will work fine.


 Sounds reasonable.

I think this is where free draining is key and why a coil is bad and why Breville uses the PTFE tube (although the Gaggia TS is a coiled capillary tube lol).

On depressurisation, your system should be self evacuating as gas compression at the gauge end, will expand pushing out the fluid back into the open boiler cavity.

As always in these things, it's usually not the fine detail that kills you. I would be worried about dead space hang up and stagnation/ bio growth more than some pressure variability at the gauge.

I would be tempted to say you keep the manifold block, but instead of soldering in a capillary tube, just tap in a nipple (would be easier as well, no?) and run the PTFE tubing up to the Gauge. Job done. Hopefully this reduces, rather than encourages, twitch....


----------



## FairRecycler

Blue_Cafe said:


> I think this is where free draining is key


 Very true, but it's hard to achieve with the common front panel mount layout, where the gauge is located low. I'm aiming to get to a solution to all scenarios.



Blue_Cafe said:


> although the Gaggia TS is a coiled capillary tube lol).


 As I mentioned earlier that is a heat exchanger machine with the boiler always half empty - roughly - and the gauge is tapped to the top of the boiler so water has no chance to get into the tube at all.



Blue_Cafe said:


> compression at the gauge end, will expand pushing out the fluid back into the open boiler cavity.


 My only concern here is compressed air will try to find the less resistance and would rather push through the centre leaving some remaining water "stuck" to the sidewalls due to capillary action.



Blue_Cafe said:


> I would be worried about dead space


 Thank you for reminding me again. I keep skipping this, however I totally agree with you on this.



Blue_Cafe said:


> tap in a nipple (would be easier as well, no?) and run the PTFE tubing


 The fittings will be delivered tomorrow, I'm also going to see a local machinist to get a fitting to the gauge directly to skip the snubber - designed for fluid - it comes with. I have some PTFE tube to test with but I'm struggling to find supply of food grade PTFE tubing on an affordable price  I'm hoping to find a routing for the PTFE for the front panel mounted approach too, which ticks all the boxes.

Thank you for your ongoing support, you helped me a lot too.


----------



## Blue_Cafe

FairRecycler said:


> Very true, but it's hard to achieve with the common front panel mount layout, where the gauge is located low. I'm aiming to get to a solution to all scenarios.
> 
> As I mentioned earlier that is a heat exchanger machine with the boiler always half empty - roughly - and the gauge is tapped to the top of the boiler so water has no chance to get into the tube at all.
> 
> My only concern here is compressed air will try to find the less resistance and would rather push through the centre leaving some remaining water "stuck" to the sidewalls due to capillary action.
> 
> Thank you for reminding me again. I keep skipping this, however I totally agree with you on this.
> 
> The fittings will be delivered tomorrow, I'm also going to see a local machinist to get a fitting to the gauge directly to skip the snubber - designed for fluid - it comes with. I have some PTFE tube to test with but I'm struggling to find supply of food grade PTFE tubing on an affordable price  I'm hoping to find a routing for the PTFE for the front panel mounted approach too, which ticks all the boxes.
> 
> Thank you for your ongoing support, you helped me a lot too.


 The free draining thing is a bugger with the gauge low, huh.

a key advantage of your manifold block is that it is ( i think) at the lowest point possible in the system, so if its going to free drain at all, its going to to here 

Great job.


----------



## FairRecycler

Some footages from today. There are some interesting things captured.

For brewing I ground too coarse to see what the flow reduction does.

Infeed only, coarse ground, gauge

Indeed only coarse ground brew

Both coarse ground gauges

Both coarse ground brew

Free flow pressure deviation


----------



## Blue_Cafe

FairRecycler said:


> Some footages from today. There are some interesting things captured.
> 
> For brewing I ground too coarse to see what the flow reduction does.
> 
> Infeed only, coarse ground, gauge
> 
> Indeed only coarse ground brew
> 
> Both coarse ground gauges
> 
> Both coarse ground brew
> 
> Free flow pressure deviation


 I'll make a guess that the high reading gauge in the last video was on the safety valve manifold?


----------



## FairRecycler

Blue_Cafe said:


> I'll make a guess that the high reading gauge in the last video was on the safety valve manifold?


 Yes you right there


----------



## FairRecycler

I'm wondering if it's down to the orifice between the 2 gauges?

However on the brew videos the flow looks identical so does the infeed boiler reading, but when it's the only gauge, there is no orifice in the system - apart from the solenoid valve.

Once I finished all tests I'll get rid of the orifice and re test it to see if it caused by that or simply the location.

Exciting


----------



## Blue_Cafe

FairRecycler said:


> Yes you right there


 3 barg differential is some internal resistance huh. (why is your gauge resting at 3barg ?)


----------



## FairRecycler

Blue_Cafe said:


> (why is your gauge resting at 3barg ?)


 Heating up cold water in the boiler after a brew.


----------



## Blue_Cafe

FairRecycler said:


> Heating up cold water in the boiler after a brew.


 oh right, Steam at 3 barg is 145c which is the steam temp trip. Interesting.


----------



## FairRecycler

I've installed and tried numerous pressure gauges on the Classic, but surprisingly, none of them showed such a decrease in the pressure. I guess I've never seen the actual brew pressure before.

I'm really keen on others experience on this

Here is the link again just in case 5 is too much at a time for some.

Brew pressure Vs pump pressure?


----------



## phario

FairRecycler said:


> I've installed and tried numerous pressure gauges on the Classic, but surprisingly, none of them showed such a decrease in the pressure. I guess I've never seen the actual brew pressure before.
> 
> I'm really keen on others experience on this
> 
> Here is the link again just in case 5 is too much at a time for some.
> 
> Brew pressure Vs pump pressure?


 Sorry. I turn away for a moment and I see there's been a flurry of activity. For my benefit and for others, can you summarise the key issues, findings, questions? It can be difficult to follow the plot, and to know what the videos are in reference to.


----------



## FairRecycler

Blue_Cafe said:


> oh right, Steam at 3 barg is 145c which is the steam temp trip. Interesting.


 I suppose it builds up to higher pressure, If I remember well when you fill up a cold boiler with cold water and heat it up to steam temp (145°C at the stat) you normally hear the safety valve engaging to release pressure, unless you have a leaky steam valve or solenoid. I tried it on my machine but both leaking hahaha it's just typical


----------



## Blue_Cafe

FairRecycler said:


> I suppose it builds up to higher pressure, If I remember well when you fill up a cold boiler with cold water and heat it up to steam temp (145°C at the stat) you normally hear the safety valve engaging to release pressure, unless you have a leaky steam valve or solenoid. I tried it on my machine but both leaking hahaha it's just typical


 The pressure is regulated by the thermostat. Pressure and temp are a fixed quantity.

The thermostat hack some do on these machines raises the steam pressure generated in the unit by 50% from 3barg to 4.5barg (and is probably a reason why their steam valves leak and wear so quickly) If you assume a 5c tolerance, then the max pressure becomes over 5 barg

The only time pressure is dumped is if the safety valve rating is exceeded or the brew group is opened.

I believe, anyways


----------



## FairRecycler

phario said:


> Sorry. I turn away for a moment and I see there's been a flurry of activity. For my benefit and for others, can you summarise the key issues, findings, questions? It can be difficult to follow the plot, and to know what the videos are in reference to.


 Sure.

Flutter wise no changes. So far I tried both the boiler infeed tapping and the boiler outfeed tapping with the orifice built in the main flow with the setups below:

10" capillary tube dry

10" capillary tube water filled

40" capillary tube dry

40" capillary tube water filled

Also tried the infeed tapping without the other one to set the flow back to factory.

All cases showing similar results boiler infeed tapping with tiny flutter of the needle, boiler outfeed tapping still as we want it.

Today I brewed 2 doubles as well grinding a bit too coarse to see the effect of the flow reduction - couldn't see any benefits TBH, BUT captured more than 3 bar difference between the 2 gauges towards the end of the shot.

To me it seems like, if you tap before the boiler, you simply not seeing the brew pressure, but the raw pressure from the pump / OPV.

I'm really excited.


----------



## FairRecycler

Blue_Cafe said:


> The pressure is regulated by the thermostat. Pressure and temp are a fixed quantity.
> 
> The thermostat hack some do on these machines raises the steam pressure generated in the unit by 50% from 3barg to 4.5barg (and is probably a reason why their steam valves leak and wear so quickly) If you assume a 5c tolerance, then the max pressure becomes over 5 barg
> 
> The only time pressure is dumped is if the safety valve rating is exceeded or the brew group is opened.
> 
> I believe, anyways


 On a standard thermostat (145°C-15) Gaggia Classic builds pressure up to 8.5-9.0 bars and then cools down to 2 bars before it engages the heating element again. So if your OPV is set to 8-8.5 bars it's likely to trigger.

I've just checked it.


----------



## Blue_Cafe

FairRecycler said:


> On a standard thermostat (145°C-15) Gaggia Classic builds pressure up to 8.5-9.0 bars and then cools down to 2 bars before it engages the heating element again. So if your OPV is set to 8-8.5 bars it's likely to trigger.
> 
> I've just checked it.


 Really?

That's interesting!

I wonder what's going on there?

Edit: Expansion perhaps.


----------



## phario

FairRecycler said:


> Sure.
> 
> Flutter wise no changes. So far I tried both the boiler infeed tapping and the boiler outfeed tapping with the orifice built in the main flow with the setups below:
> 
> 10" capillary tube dry
> 
> 10" capillary tube water filled
> 
> 40" capillary tube dry
> 
> 40" capillary tube water filled
> 
> Also tried the infeed tapping without the other one to set the flow back to factory.
> 
> All cases showing similar results boiler infeed tapping with tiny flutter of the needle, boiler outfeed tapping still as we want it.
> 
> Today I brewed 2 doubles as well grinding a bit too coarse to see the effect of the flow reduction - couldn't see any benefits TBH, BUT captured more than 3 bar difference between the 2 gauges towards the end of the shot.
> 
> To me it seems like, if you tap before the boiler, you simply not seeing the brew pressure, but the raw pressure from the pump / OPV.
> 
> I'm really excited.


 Hi Steve. Nice to see you excited. 

Just to be clear, the main point you wanted to make is in this video? https://streamable.com/1dvpyn (Be careful as I think you are sometimes linking the wrong one). So the point that you are making is that the gauge measurements before the boiler differ from gauge measurements after the boiler using a coarse grind?

I'm not being rude, but just making sure we're on the same page: isn't this what I said was going to happen with reference to the article?

https://www.coffeeforums.co.uk/topic/53171-pressure-gauge-discussion-experiment-improvement/page/4/?tab=comments&do=embed&comment=760296&embedComment=760296&embedDo=findComment#comment-760296

When a coarse ground is used, there is not enough resistance at the portafilter side to equilibrate the pressure everywhere in the system. So you're going to see pressure differences, particularly between areas where there are big differences in orifice sizes. The same is true for the free flow experiment you have---there is pressure in the system somewhere that is being kept there due to the various arrangements. This is further exacerbated by the fact that you're using the flow limiter.

In order for you to reset this, you need to block the portafilter side at a higher pressure than what's occurring in the system. This isn't happening with either the coarse ground or the free flow. Hence the results.

Regarding the free-flow experiment (https://streamable.com/pxiupo), then assuming that the gauge on the left is the outfeed, then this makes sense. The outfeed gauge has zero resistance. The infeed gauge has some sort of internal resistance that is reluctant to vent.

Would you agree with the above? Have I misunderstood some other aspect of what you were saying?

Assuming that we are not misunderstanding, there are a lot of benefits to your setup since tapping to the boiler outflow with a flow limiter essentially provides more accurate (and stable) measurements over a wider range of grinds. It is essentially the closest pressure to the portafilter. The flow limiter also helps given what we know about the OPV mod and the lower pressures desired (cross my fingers not to enter into a discussion here). Finally, what your experiment indicates is that there is some worry that pressure readings are wrong for people who use coarse grinds, and that moreover, your setup may be important for people who are using dimmers or pressure profilers.


----------



## FairRecycler

phario said:


> I'm not being rude, but just making sure we're on the same page: isn't this what I said was going to happen with reference to the article?


 Of course I knew, I just had no idea... 

I didn't expect to have such a huge difference.



phario said:


> I think you are sometimes linking the wrong one)


 Yes you right there too.

Yes I agree with all, I just didn't expect to see a gauge climbing up to 6 bars while thee is a free flow, nor more than 3 bars difference on the 2 ends of the boiler. Yes obviously the majority is caused by the orifice.


----------



## FairRecycler

It is tempting to drill out the orifice, to see the difference between the differences  But I'll do the PTFE testing first with the same setup, I can't wait.

@phario

Do you have any input on my concern regarding the front panel mounted gauge scenario?


----------



## phario

FairRecycler said:


> Yes I agree with all, I just didn't expect to see a gauge climbing up to 6 bars while thee is a free flow, nor more than 3 bars difference on the 2 ends of the boiler. Yes obviously the majority is caused by the orifice.


 I'm not sure of the second statement you made there. I think it is a mixture of different things, and the orifice does have an effect. However it might not be as drastic as you might think. In the case of free flow, what you saw was that gauge B was stuck at 6, and gauge A at 0. Gauge A = 0 makes sense because it's essentially a clear tube and the pressure is atmospheric. As the tubes began to refill, the gauge A started to increase. You stopped the machine a bit too early, but eventually they would agree (I would think). The question you're asking is whether the fact one is at 0 and the other at 6 related to the flow limiter? I don't know. I would not be surprised if you could get the same in your inflow/outflow system without the limiter.

By the way, these experiments do convince me that the capillary tube length has little to do with it. I largely agree with this, except for possibilities related to heat (long tubing being more exposed to heat).

Now I'll go read over your front panel question...


----------



## FairRecycler

phario said:


> (long tubing being more exposed to heat).


 That's interesting, I thought a longer tubing restricts heat impact of the manifold to the gauge - these gauges not rated for high temperature, but the manifold is near to the brew group's temp especially the outfeed one. With the 10" tubes I felt the gauges to get warm. With the 40" tube there is no heat conduction to the gauge at all.


----------



## phario

FairRecycler said:


> That's interesting, I thought a longer tubing restricts heat impact of the manifold to the gauge - these gauges not rated for high temperature, but the manifold is near to the brew group's temp especially the outfeed one. With the 10" tubes I felt the gauges to get warm. With the 40" tube there is no heat conduction to the gauge at all.


 Sorry I was referring to longer tubes being routed in a manner near or away from heat sources like the boiler.


----------



## phario

Okay, so let's get to this issue of free draining. I have yet to see anybody on the forums explain free draining in any clear way as it pertains to this problem. Because these are closed systems subject to large flows, pressures, and temperature changes, I'm not even sure of the basic mechanisms that are important. I understand that most people are simply thinking gravity = good, but it is not so obvious---at least to me.

*Question:* given a volume of liquid that exists in a small capillary tube, what is the effect of gravity on that volume. Is elevating the tube will be enough to drain the fluid? If so, then at what height should it be raised?

*Assumptions:* The most basic model is:



Neglecting how the liquid appears into the cap tube.


Neglecting the effects of temperature differences.


Neglecting the effects of the pump


Only including surface tension (capillarity) and gravity


Ignoring dynamics (you're not going to discuss movement---just equilibria); dynamics are more complicated.


*Physics: *I'm going to give a basic lesson on physics of surface tension in case people don't know. In a given liquid, all the molecules are pulling towards each other. Those at the interface have an imbalance of force. Surface tension (or capillarity) is that force. Wiki: surface tension. 

There are two situations you might envision.

*Case 1:* Basic capillary rise.









In the most basic situation, you have a capillary rise direct from the T-junction or inlet to the capillary tube. It looks like the picture above. The maths here are very simple. There is a law that indicates how high the fluid will typically rise due to surface tension (pulling up) until it comes into balance with gravity. In a separate post, I gave a calculation of how high you might expect the fluid to rise in a system where you have a 1mm capillary tube. This is only about 1cm. Even if some of the numbers are off, we would probably expect this to be largely accurate---you're not getting more than a handful of centimeters of rise.

Compare with this graph and you can see my estimate is about right. https://www.engineeringtoolbox.com/capillarity-d_961.html









Therefore, anything more than a few centimeters won't have the surface tension causing an increased pullup.

*Case 2:* Slug flow

The situation gets more complicated if the fluid separates and forms a slug, as is illustrated below.









I won't get into the details of this problem because it is much more complicated. Basically what can happen is that the surface tension forces are able to hold the slug up against the force of gravity. Predicting this, however, is extremely complicated and highly dependent on the surface properties (how smooth or rough it is). If you are truly interested, you can read more from the classic reference "Capillary and wetting phenomena":









The point of sharing the above is to show you that there are a lot of unknowns here, notably the angles theta_R and theta_A. These are only known for very carefully conducted experiments with carefully prepared surfaces. No-one knows these numbers for the interior of a dirty capillary tube you bought from AliExpress!

*Conclusions:* ...I don't know. Based on what we know about the simplest scenario, you might argue that free draining will take place as long as the capillary tube is raised at least a few centimeters from the inlet. However, there are a lot of factors that aren't being included. The liquid may break up into a slug and then this slug's behaviour is much more complicated.

I think in general though, there is agreement that raising the gauge is good, but the degree of 'how good' might turn out to be negligible.


----------



## Blue_Cafe

In my case, i am simply commenting on free draining for hygiene reasons. Trapped water can be a problem for stagnation and mould.

The coils in the supplied tubes are mostly for packaging purposes no?

I doubt these systems need pigtailing but i've no idea of the temp ratings of the gauges.


----------



## FairRecycler

phario said:


> Okay, so let's get to this issue of free draining.


 Thanks for this.

My major concern is the pressure compressing the air to the 1/10 of the tube volume filling it up with water, and we don't know much about what happens after that would be great to at least test it with clear or transculent tubing (any idea?). I'm worried about potential slug development in the tube after some use. It would possibly lead to a fluttering needle, no mention of the food hygiene perspective as that isn't negligible for sure.



Blue_Cafe said:


> The coils in the supplied tubes are mostly for packaging purposes no?


 I don't know why "T piece tapped" units having coils. Mine only had 1 coil to ease installation.

The recent boiler outfeed version requires coils, they do a great job in cooling - the piggyback end is really hot, but after the coils it's not even luke warm.

Higher temperature rated gauges are quite pricey - at least the ones I found, but I would be happy to be proven wrong on this.

The gauges I'm currently using, are rated for 60°C that's pretty much the ambient temperature inside the machine anyway. If you add extra heat through the copper tube it could affect the accuracy of the gauge.


----------



## phario

FairRecycler said:


> The recent boiler outfeed version requires coils, they do a great job in cooling - the piggyback end is really hot, but after the coils it's not even luke warm.


 That's really interesting.



FairRecycler said:


> My major concern is the pressure compressing the air to the 1/10 of the tube volume filling it up with water,


 I read your argument and I had to table it for further thought. I think I understand your issue though, which is that as the system pressurised, the air inside the cap tube compresses and pulls liquid into it.

However, is this easy to test? After a few experiments, can you confirm whether the tube does in fact fill with water?


----------



## FairRecycler

I've checked the cap tube for water residue and found 0.9g in the 40" tube. After a quick calculation I realised it was full of water...

Of course it was the water filled version... 😂😂😂

I'll have to do it again.

Bad news:

I drilled out the orifice from the boiler outfeed manifold, as I'm willing to control brew pressure with a PWM signal on the pump in the future (pressure accumulation in the boiler due to restricted outfeed flow, would cause delayed pressure change at the brew group, and that's unacceptable), and I prefer to do get the pressure gauge done this time completely, without the need of further revisions.

I hooked up the PTFE tube version and the boiler infeed needle has the tiny flutter what it always had (still connected via a 40" water filled cap tube), but the PTFE tubed boiler outfeed needle flutters really badly 😭.

However I expected this to happen, so couplers for the gauge will be made by a machinist on Monday, BUT I'll have to test orifice sizes (I doubt the same 0.5mm one would be sufficient as we have air at that end of the tube, not water) And the machinist can't drill anything below 0.7mm so it will be my pleasure to drill 0.5-0.4-0.3-0.2mm holes. I'm hoping to get good results with the 0.5mm, I really do.

Anyone has a good supplier of STEEL drill bits below 0.5mm? The carbides just too rigid for these needs I'm afraid.

PTFE TEST no orifice


----------



## phario

Not surprising that would be unstable. Big drainage on that ptfe route certainly though.


----------



## phario

Some quick thoughts, since I wrote the previous one in haste.



As I've said before, I partly like the PTFE design because it would be good to have a design where the copper cap tube is not permanently afixed to your block. With a permanent fixture, it is a pain to service---both for routine maintenance and also for longevity services where you don't want to braze. Servicing the PTFE-cap-tube design is a cinch: you pull off the tubes at either end.


The other thing that occurs to me is that ensuring serviceability is also crucial in your top-lidded design because it would be a giant pain for people to be removing a top that is linked by a cap tube direct to the outfeed (You have probably thought of this yourself and so that's why you're going down this PTFE path). It would be easier if there were PTFE slack and that allows people to pull the lid off, reach in, and remove the PTFE tube from one of the push fittings. Still, you should consider how easy this is to do, and the perils of doing so. That is, how easy is it to even reach in when all the internals are in and remove a push fitting?

We never think of this in the front-mounted gauges because they're linked so expediently to the Pump-OPV line and the gauge is never really touched.


Obviously though it increases the number of fittings, as you'll probably agree that the cap tube is a good thing. (Yeah yeah it's still a question mark, but see below).


Remember that for those with front mounted designs, there are clearance issues if the gauge lies in front of the boiler. You only have, I believe, around 35mm of space from the back of the case to the boiler. So those straight PTFE-to-gauge designs won't work.


I am embarrassed to say that I never even thought of the challenges of drilling that small (0.1mm).


The number of variants you're working is quickly spinning out of control.


----------



## FairRecycler

@phario

Yes we have very similar thoughts according to the importance of servicability / access.

I made a close-up and tried not to shake the camera that much this time 

I'm not sure I have to go any further to be honest.

I'll still try the coupler with 0.5mm orifice.

PTFE tube without orifice

I don't think I'll offer the PTFE tubed version to front panel mount, due to food hygiene concerns @Blue_Cafe mentioned.

I never thought drilling tiny holes could be this challenging.

I'm getting closer day by day


----------



## phario

FairRecycler said:


> PTFE tube without orifice


 That looks great. Be careful to specify exactly what you mean...there are a few orifices around!

So to make sure I understand:

Left gauge = PTFE to outfeed with no flow control orifice and no cap tube

Right gauge = cap tube to infeed

Both look solid, to be honest. Have you emptied the cap tube now?

I know this seems to go back-and-forth, and we've discussed the flow control aspect via PM and it seems like it's a good thing. However, one fear I have is that you're putting in a pretty big change. You should be relatively sure of the consequences of this change (beyond just the pressure gauge). It would also make calibration between individuals complicated since, when diagnosing their espressos they might wonder if some aspect is due to the flow limiter. Just to be clear, from your flow experiment, I don't think there is an effect---i.e. with the smaller orifice, you're still getting the same grouphead flows as expected because it's the coffee grounds that controls the flow.

*Edit:* I did some more reading on this. The name for the boiler outfeed orifice is called a gliceur, with typical sizes 0.6-0.8mm. There is a nice discussion here of installing flow limiters which led me to the reference on the gicleur size.



> *What Is a Gicleur? Why Is It So Important?*
> 
> A properly designed espresso machine has a restricting aperture inserted into the path of the pressurized water to control the amount and rate of its flow. The technical name of that device is "gicleur." Although it is often referred to as the "gicleur valve," it is not a valve at all; instead it is a limiting aperture, normally between 0.6 mm and 0.8 mm in diameter.
> 
> The gicleur plays several important roles in the functioning of a properly tuned espresso machine. First, it limits the amount of water that flows into the porta filter in a given period of time. Slowing down the flow of water is important for production of quality espresso. Always remember that making espresso is not a speed contest.
> 
> Second, it protects the coffee in the porta filter from being blasted by the initial pressure wave that emanates from the pump as soon as it is turned on. This pressure wave travels down the tubes and impinges on the top of the coffee in the porta filter if the restrictor is not in place to dissipate this wave. In the absence of the gicleur, the initial blast of water creates a crater on the top of the coffee puck, thereby making the center portion of the puck much thinner than the surrounding portions. This causes most of the water to channel through this thin coffee in the middle of the puck. When that happens, the resulting liquid will be weak and bitter because the center portion of the puck would have been over extracted and the surrounding portions of the puck left under extracted.
> 
> When the gicleur is installed, the 140 lbs/square inch pressure wave reaches the pump side of the aperture, and the entire pressure drops across this orifice, with the pressure on the other side being zero. As some water passes through the aperture, water pressure slowly build up behind the aperture, on top of the coffee. Thus the water pressure that the coffee is exposed to builds up gradually from zero to 140 lbs/square inch with minimum disruption of the coffee puck surface. This gradual build up is important to maintain the integrity of the puck for quality espresso extraction.
> 
> It is not uncommon for the gicleur to be opened up to 2 mm or larger or to be left out altogether when people focus on production rate rather than on espresso quality. Some of the espresso machines used by the large chains fit this description.
> 
> The simplest way to determine if your machine is equipped with a gicleur is to make a "water debit" measurement. This is a very simple, common sense based, concept and is described in the next section of this news letter. Though based on common sense rather than exact science, it is nevertheless a very useful measurement to make.


----------



## Blue_Cafe

I like the PTFE/Expansion valve manifold/top mount gauge arrangement. It just looks "right".

Agreed with the rejection of the low mount option, although you could try a diaphragm seal in the line??

(Dunno if that's feasible).

Now that you have the PTFE / manifold block sorted, I wonder how adding a 9bar bypass on the this line to the gauge would work? Whilst the additional bypass resolves my own (well documented lol) hang up about using the safety valve as an opv, it would be on the group head side of the boiler (as opposed to the pump side in the normal opv mods) and the boiler void may act as a buffer to the bypass, enabling a bit of a smoother, more laminar flow at the puck?

You've tapped into the boiler and done the hard work. Just tee into the Gauge line, add a inline OPV and route back to the tank.

Just a thought 

keep up the good work.


----------



## FairRecycler

@phario

Thank you for all this, you digged out some very useful information again.

Just to clarify, I decided to pull away from adding an extra orifice - the ones in the solenoid valve and the brew head ( both 1-1.5mm diameter by eye) are still in place obviously - simply beacause, my plan is to regulate pressure in the near future with a PWM signal on the pump. This 0.5mm orifice made a significant pressure differential between the pump end and the brew head, leading to a delayed reflection of a pressure decrease at the puck, when the pump is controlled.

The main aim of this experiment is to sort the pressure gauge out. I added this extra orifice, as I was interested in the affects. In my opinion the flutter is near enough to the acceptable level, however I'll still try a purpose made snubber at the gauge end.
On the other hand I find the article really useful to set the steep beginning of the pressure profile accordingly.


----------



## FairRecycler

@Blue_Cafe



Blue_Cafe said:


> diaphragm


 I've just checked what this is 

Sounds like a good idea to me, however I have no idea if I can find one for this application - an M5 male to M5 female would be just perfect or something with 6mm push for. I doubt any of these existing.

I don't understand your concern according to the safety valve I'm afraid.

I thought the boiler void acts as a buffer with the current setup anyway. Also there is an orifice in the solenoid valve ( just checked it's 1mm, and I was wrong the in the brew head there is a 2.5mm hole so that won't act as an orifice in my understanding ) to smoothen the flow to the puck.

The few commercial machines I've seen has the OPV at the pump outfeed too.

May I ask for further explanation please


----------



## Blue_Cafe

FairRecycler said:


> @Blue_Cafe
> 
> I've just checked what this is
> 
> Sounds like a good idea to me, however I have no idea if I can find one for this application - an M5 male to M5 female would be just perfect or something with 6mm push for. I doubt any of these existing.
> 
> I don't understand your concern according to the safety valve I'm afraid.
> 
> I thought the boiler void acts as a buffer with the current setup anyway. Also there is an orifice in the solenoid valve ( just checked it's 1mm, and I was wrong the in the brew head there is a 2.5mm hole so that won't act as an orifice in my understanding ) to smoothen the flow to the puck.
> 
> The few commercial machines I've seen has the OPV at the pump outfeed too.
> 
> May I ask for further explanation please


 Just ignore me. I'm flogging a dead horse with it.


----------



## FairRecycler

Good news 

While I'm waiting for the machined couplers I thought I'll try to make one myself, in order to carry on with testing. After a 2 day torture I managed to get 1 piece done, and Eureka it's holding pressure.

My assumption is confirmed now, the 0.5mm orifice in the gauge coupler 100% eliminates the needle flutter, yet it is really responsive to pressure changes, so reflects the actual brew pressure punctually.

Later on today I'll film it as well, to let you guys see the result.

I'll test it in the next few days and hopefully than I can order the first batch of these couplers.

Attached a photo of the latest design, the only difference is the orifice diameter is 0.5mm not 0.2mm.


----------



## Blue_Cafe

I can't like this thread enough to be honest.

Utterly amazing work fella!


----------



## L&R

0.5 can get easily clogged or ?


----------



## FairRecycler

L&R said:


> 0.5 can get easily clogged or ?


 That's the gauge end of a 4mm ID dry PTFE tube, so there is nothing but air at that end.  At least that's what I'm hoping for.


----------



## phario

L&R said:


> 0.5 can get easily clogged or ?


 See my reference above about the gliceur:

https://www.coffeeforums.co.uk/topic/53171-pressure-gauge-discussion-experiment-improvement/page/6/?tab=comments&do=embed&comment=762141&embedComment=762141&embedDo=findComment#comment-762141

So according to that 0.6mm-0.8mm is normal for a boiler outlet (the bit that goes to the grouphead). Of course, this is different than the coupler that @FairRecycler mentioned, which is not directly connected to the grouphead. But it seems that 0.5mm holes aren't atypical even in the primary flow. Your question though does make me wonder what is the diameter of the solenoid hole?

I was curious so I looked up sewing pins to get an idea of sizes. The typical patchwork pin is 0.4mm and dress sewing pins run around 0.5-0.8mm it seems.

@FairRecycler why was it so difficult for you personally to make the coupler? Was it the 0.5mm drilling?

As noted, this is quite exciting and interesting. It's not unusual though (and the principles are in other machines). But it's unusual to see someone thinking so deeply about this. Great job.


----------



## FairRecycler

So here is the video what we made with my son (he is 3 yeas old  ) this afternoon.

Left infeed cap tube, Right outfeed PTFE with 0.5 orifice @ gauge end


----------



## Blue_Cafe

Rock steady


----------



## FairRecycler

I`ve been observing the water in the PTFE tube, and I`m not happy.

The PTFE tube fills up completely (obviously I didn`t count with the volume of the gauge itself) This could possibly lead to clogs as @L&R questioned, also calcification can build up in the orifice itself, and it also transfers heat to the gauge, possibly causing inaccuracy. I`ve also spotted slugs in the tube after depressurising it, however it doesn`t seem to affect the needle at all (not yet at least, however after repeating the cycles several times the occurences seem identical

To say something good too, I`ve found a supplier providing the parts on a reasonable price, however I have to buy 100m of the PTFE tube  I need 40cm / unit. LOL


----------



## Blue_Cafe

FairRecycler said:


> I`ve been observing the water in the PTFE tube, and I`m not happy.
> 
> The PTFE tube fills up completely (obviously I didn`t count with the volume of the gauge itself) This could possibly lead to clogs as @L&R questioned, also calcification can build up in the orifice itself, and it also transfers heat to the gauge, possibly causing inaccuracy. I`ve also spotted slugs in the tube after depressurising it, however it doesn`t seem to affect the needle at all (not yet at least, however after repeating the cycles several times the occurences seem identical
> 
> To say something good too, I`ve found a supplier providing the parts on a reasonable price, however I have to buy 100m of the PTFE tube  I need 40cm / unit. LOL


 Any tube will have to fill up regardless as it's the liquid acting as the piston to compress the air and expand the burdon tube.

The good point for the tube Vs copper is that the tube size won't allow capillary action prevent free draining.

That said, you may have allowed air to flow out under compression?

Is the line from the manifold to the gauge straight and clean and vertical?


----------



## FairRecycler

It seems, I won't get away without making that water accumulation chamber on top of the manifold. At least now I have a tiny bit of room in costs, however I was hoping to make it cheaper than the current version with outsourcing the machining to Eastern Europe.

On the other hand it would cover the front panel mount version too, and probably I could get rid of the PTFE tube as well, saving funds sitting on the shelf in the form of a 100m roll. 

It's a never ending story isn't it?


----------



## Blue_Cafe

FairRecycler said:


> It seems, I won't get away without making that water accumulation chamber on top of the manifold. At least now I have a tiny bit of room in costs, however I was hoping to make it cheaper than the current version with outsourcing the machining to Eastern Europe.
> 
> On the other hand it would cover the front panel mount version too, and probably I could get rid of the PTFE tube as well, saving funds sitting on the shelf in the form of a 100m roll.
> 
> It's a never ending story isn't it?


 Water chamber?


----------



## FairRecycler

Blue_Cafe said:


> Any tube will have to fill up


 I supposed it'll only fill up to 90%, as the air in the tube will be compressed 1:10 @10 bar



Blue_Cafe said:


> prevent free draining.


 Very true, but as it fills up completely we can assume it goes through the orifice too and that part of the water won't freedrain for sure, due to the vertical position, and the orifice itself)



Blue_Cafe said:


> That said, you may have allowed air to flow out under compression?


 I don't think so, I'd rather bet on the volume of the gauge inside (from gauge inlet coupler to bourdon) is greater than the 10% of the whole tapping system 



Blue_Cafe said:


> Is the line from the manifold to the gauge straight and clean and vertical?


 That's impossible mate

At least it is to the best of my knowledge, in the Gaggia Classic, in my top extension mount application.


----------



## FairRecycler

Blue_Cafe said:


> Water chamber?


 I was thinking of a 1/2" copper tube from the top of the manifold to the top of the boiler as a water accumulation chamber with a cap tube on top of it leading to the gauge (which in theory would never get water fed into it due to the increased volume of the tapping system).

As water level couldn't reach the top of the chamber (the chamber itself should be sized greater than 90% of the volume of the whole tapping system -BTW I assumed the PTFE tube version would comply with this, obviously I didn't count with the volume of the gauge itself), we could consider the cap tube "dry", so routing, cooling coils, and lower mounting shouldn't be an issue neither.

It should also have a good affect on the main flow as a buffer.

On the flip side it greatly increases man hours.


----------



## phario

FairRecycler said:


> I was thinking of a 1/2" copper tube from the top of the manifold to the top of the boiler as a water accumulation chamber with a cap tube on top of it leading to the gauge (which in theory would never get water fed into it due to the increased volume of the tapping system).
> 
> As water level couldn't reach the top of the chamber (the chamber itself should be sized greater than 90% of the volume of the whole tapping system -BTW I assumed the PTFE tube version would comply with this, obviously I didn't count with the volume of the gauge itself), we could consider the cap tube "dry", so routing, cooling coils, and lower mounting shouldn't be an issue neither.
> 
> It should also have a good affect on the main flow as a buffer.
> 
> On the flip side it greatly increases man hours.


 I'm not sure what was the size of the Hungarian expansion chamber idea we discussed, Peter, but the author notes drainage issues, so that's worth keeping in mind. As in he noted that the chamber would have to manually 'drained' (by periodically venting the boiler I think).

It's not clear to me that you're not swapping one set of drainage and maintenance issues with another.

One point to make is that the capillary tube design must be in tens of thousands or possibly millions of espresso machines around the world.

Well done on the ptfe and coupler design! 🙉


----------



## FairRecycler

phario said:


> As in he noted that the chamber would have to manually 'drained' (by periodically venting the boiler I think).


 Yes I thought about that, however I can't understand it. If there is no leak in the tapping system, the level of fluid (level with the tapping point when installed) should be constant @ standard circumstances.



phario said:


> One point to make is that the capillary tube design must be in tens of thousands or possibly millions of espresso machines around the world.


 It is the best approach as long as water can't get into the cap tube (in my understanding) hence it's commonly used on HX machines where the boiler is only half filled.


----------



## FairRecycler

phario said:


> It's not clear to me that you're not swapping one set of drainage and maintenance issues with another.


 Fair point


----------



## phario

Sorry, I realised I completely misread the flow of conversation. The point you were making was that the PTFE tube does fill with water so the drainage issue is in reference to that. For some reason, I was stuck into thinking about the cap tube.

I guess the natural question to ask is how much of that PTFE fluid remains static from shot to shot.

I personally don't know how much it is important to modify the current setup, which I think is great. So outflow manifold to a short length of PTFE tube to coupler to cap tube. This setup has the advantage of being flexible and serviceable. If you want to drain the system, just pull out the quick fittings and it can be done in seconds. If you want to change the PTFE pipe length, you can. It's quite modular.

The other thing you might consider is to make sure the PTFE system can be capped, i.e. it would be good to be able to cap the outlet to the pressure gauge in case the gauge wants to be disconnected (temporarily or otherwise). Can people buy a cheap end cap that can be pushed into the push fitting on the manifold? Remember that the lid design you have will need to be removed, so of course people will want to disconnect the gauge and potentially service the machines with the lid off (PID wires hanging).

I guess it's a minor concern, but it's still a concern if you think of how most people use a pump-to-OPV T-junction and that's completely removable.

I think these are also minor issues as well.


----------



## FairRecycler

@phario



phario said:


> I guess the natural question to ask is how much of that PTFE fluid remains static from shot to shot.


 There isn't a lot of water remaining at all. What I noticed was a 1-2mm long slug. After numerous shots I can't see water accumulation in the PTFE tube neither.



phario said:


> make sure the PTFE system can be capped


 M5 16bar plug screw



phario said:


> Remember that the lid design you have will need to be removed,


 This why the flipping over approach is in place. The PTFE tube won't need to be disconnected to open up the machine, it is designed to reach in the flipped rest position - see attached photo.


----------



## phario

FairRecycler said:


> This why the flipping over approach is in place. The PTFE tube won't need to be disconnected to open up the machine, it is designed to reach in the flipped rest position - see attached photo.


 That is sweeeeet.


----------



## Strumph

Hi. What is the best way to test pressure with pressure guage in portafilter. Must be without basket or with basket test?

My best results is with no basket inside.


----------



## FairRecycler

@Strumph

Yes that's the best approach, it's tend to leak with a basket in place.


----------



## FairRecycler

Well behind with updates here 

so the PTFE tube didn't work out.

When air filled: water keeps climbing up in the tube after a few days of usage resulting water slugs in the tube (due to capillary action) causing needle flutter 

When water filled: water conducts a lot of heat to the gauge, leading to possible inaccuracies in reading.

General: the stiffness of the PTFE tube pits a lot of stress on the gauge and so it is hard to maintain the correct orientation of the dial.

Manufacturing of the fittings between the push fitting and the gauge is a major issue cost wise. 

So the PTFE tube version is CEASED.


----------



## FairRecycler

So I moved back to the capillary tube version (1mm ID).

I made the tube threaded (drilled through an M5 brass bolt, and soldered the captive in) allowing replacement if ever needed. Big shout out for @phario as the replacable cap tube idea originated to him, thank you 👍

At the gauge end I only drilled a pocket in the M5 brass bolt then soldered in the cap tube and at the end I drilled the 0.5mm orifice from the stud end of the bolt. This tube water filled giving me perfect results for months now, however drilling the 0.5mm hole from the stud end, aiming for the centre of the soldered in 1mm ID cap tube is probably as problematic as it sounds 🤣

I've found a 1.6mm OD 0.6mm ID cap tube. With this I don't have to touch that 0.5mm drill bit anymore, however as it's 0.6mm all the way through, there is a higher risk of getting clogged at the boiler end.

To go all-in I revisited the solenoid manifold and tapped into the other line (Solenoid to group head, not boiler to solenoid as I did previously).

This is the line where coffee residue builds up by time, and also the final point where you can physically tap in, on the flip side here you can read the actual pressure on the Coffee puck.

Now I'm in long term test mode (since the end of October) with my own machine. I'm trying to model the worst case scenario and not even backflush the machine for months? To see if coffee residue will clog the cap tube or not, and if it does, could it be unblocked by several backflushing, or by simply unscrewing the dial and purge it out with pressure?

Photos are of a 1mm ID cap tube with a manifold going between the OPV and the boiler. This is the latest trusted version.

I know it's not the most elegant way of sealing the bolt, there is a nicer approach on it's way, if the usability/reliability gets approved.


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## phario

Just to be clear, this is just @FairRecycler's perfectionism at play.

I have have one of his older PTFE designs (the 'failed' ones) that has served well and with largely minimal (but non-zero) flutter. It's pretty darn good.

That said, I look forward to getting my hands on one of the newer designs


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## little_rob

This is an exceptional thread. Thank you all for stretching my grey matter trying to keep up.


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## FairRecycler

Black Friday deals

I wanted to note, finally I'm launching my upgraded individual panel mount pressure gauge kit on eBay (also available here with 10% discount) regarding to the experiments detailed in this thread.

I'll offer 2 different kits (both blocks goes between the over pressure valve and the boiler).

KIT 1: exactly the same as it was: 1mm ID 10" cap tube soldered to the block and to the gauge's snubber. With very little flutter.

From midnight it goes for £25 + £5 P&P (2nd class signed for) on eBay; £27 posted here. Only available for pre-order at the moment, I'm awaiting for delivery, by the end of next week I'm afraid.

KIT 2: similar as above but the 0.6mm ID 10" capillary tube soldered to M5 brass bolts and those threaded into the block and the gauge's snubber, bolts sealed with o rings at both end (pockets milled for the o rings)

100% flutter free

I'll upload photos upon delivery of the first batch by the end of next week, until than see photos 3 posts above, add CNC accuracy to e block and take away the washers keeping the o rings in place 

Goes for £35 + £5 P&P (2nd class signed for) on eBay and, £36 on here.

The first batch is very limited, I take pre-orders from here until midnight and list the remainder on eBay at that time. Hopefully a larger second batch is going to be delivered by the end of this month.

It's not a real Black Friday deal, as these prices are going to remain the same for a good while (hopefully for years).


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## MrSmartepants

Sounds like a great mod. I'm interested though I'm not sure which kit to get for my classic.


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## FairRecycler

MrSmartepants said:


> Sounds like a great mod. I'm interested though I'm not sure which kit to get for my classic.


 Both 😁

Go for the better one, it only cost "250g (half)decent beans" more, but no flutter, replacable and cleanable cap tube, without glycerine spillage upon installation or disconnection, due to any service/repair/upgrade requirements of the machine.


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## little_rob

@FairRecycler

Don't know if I've got enough clearance to get one into my Tebe. What are the dimensions of the block? Specifically the depth - the mounting bracket for the boiler & group on the Tebe leaves very little room behind the OPV / solenoid and I don't know if I can squeeze it in without modification.

If it fits (or even if it doesn't but I can work out how to engineer it) I'm in the market for a Kit 2 😄


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## FairRecycler

little_rob said:


> @FairRecycler
> 
> Don't know if I've got enough clearance to get one into my Tebe. What are the dimensions of the block? Specifically the depth - the mounting bracket for the boiler & group on the Tebe leaves very little room behind the OPV / solenoid and I don't know if I can squeeze it in without modification.
> 
> If it fits (or even if it doesn't but I can work out how to engineer it) I'm in the market for a Kit 2 😄


 Hi,

The block is 13*13*33.5mm.

I have a Paros on shelf, but never had a chance to have a look at it from the inside


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## little_rob

FairRecycler said:


> Hi,
> 
> The block is 13*13*33.5mm.
> 
> I have a Paros on shelf, but never had a chance to have a look at it from the inside


 If you did, you'd have already come up with a sparkling fix for my problem and I wouldn't have to stare at it scratching my head.

I'll dry assemble (currently waiting for new gaskets, having sanded the pitted boiler face) and measure up this afternoon. I've a feeling 13mm won't fit, but I'll take pics and seek hive mind input.


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## little_rob

little_rob said:


> If you did, you'd have already come up with a sparkling fix for my problem and I wouldn't have to stare at it scratching my head.
> 
> I'll dry assemble (currently waiting for new gaskets, having sanded the pitted boiler face) and measure up this afternoon. I've a feeling 13mm won't fit, but I'll take pics and seek hive mind input.


 Probably won't be able to get the opv lock nut off once in situ, but looks like it will squeeze in.


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## Rebel

I'm interested in Kit 2. Currently, I have an Ebay pressure gauge installed that uses the T-fitting on the PTFE tube from the pump. The needle flutter is indeed annoying. Would your kit swap out with this? IIRC the hole size is 40mm. And do you have replacement PTFE tubing since I had to cut the original? Lastly, will you ship to the US?


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## FairRecycler

little_rob said:


> Probably won't be able to get the opv lock nut off once in situ, but looks like it will squeeze in.
> 
> View attachment 48429


 I wish I kept my mouth shut, now I could have said it's been designed to fit the Tebe and Paros too 🤣

You will be fine with the OPV nut I'm sure.

@Rebel

Yes you can swap it to mine, however you will need to enlarge the hole diameter to 41.3mm (1 5/8"), and the new PTE tube, which I can include for £3.

I'm happy to ship to the US, however it costs £10 more (tracked & signed for service) than the included UK shipping service.


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## FairRecycler

Just in case anyone interested, these will be restocked at some point today on eBay.


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## Emmodd

Hi all. Can someone explain to me (or point me to an explanation) as to why a pressure gauge is useful? Is it not a case of 'set and forget' once you adjust the opv? If not, if the pressure isn't as expected/desired how do you alleviate that issue? Sorry if this is somewhere in the thread already but starting at the start it's clear it's a bit technical and I'm wanting to get to grips with the why before the how right now. Thank you.


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## FairRecycler

Emmodd said:


> Hi all. Can someone explain to me (or point me to an explanation) as to why a pressure gauge is useful? Is it not a case of 'set and forget' once you adjust the opv? If not, if the pressure isn't as expected/desired how do you alleviate that issue? Sorry if this is somewhere in the thread already but starting at the start it's clear it's a bit technical and I'm wanting to get to grips with the why before the how right now. Thank you.


 Hi,

The dynamic pressure gauge gives you insight on what happens in the portafilter while brewing. Not only is it important to pull the shot at the right pressure, but the gauge supports your understanding of good preparation, by indicating channelling (sudden drops in pressure while pulling the shot), and helps fast-track your learning curve.

It also allows traceable pressure profiling, either by opening the steam valve slightly, or by a pump dimmer modification.


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## Emmodd

@FairRecycler thank you for the explanation. Apart from drilling a hole in the casing for the gauge, do the Kita essentially just 'drop in'? Thank you.


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## FairRecycler

@Emmodd

Unfortunately it's not a that easy.

The overpressure valve should be removed in order to fit the block, and the locking ring is quite fiddly to get on.

I would consider it an intermediate level mod.


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## Emmodd

@FairRecycler if I'm adjusting the opv anyway, is it straightforward enough to do at the same time?


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## FairRecycler

@Emmodd

Yes, I'm not claiming you'll save a lot of effort this way, but it makes sense to do them at the same time


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## GiovaD

Hi all! very interesting things you're discovering here, thank you for sharing your knowledge.

I have an idea that is going in my mind since a while but unfortunately I can't try it out. About adjusting the flow of water while brewing.

So what I'm talking about is fitting a pressure reducing valve (like this one: Water pressure regulator or this one: Water pressure regulator AliExpress) to the tube connected to the pump, in order to have incoming water pressure up to 12 - 15 bar and the outgoing pressure to be set during brewing dynamically. Of course that means fitting a nob that goes outside the machine in order to screw and unscrew the upper part of the valve.

In case you're wondering that's more or less how a pressure regulator works: pressure reducing valve YouTube

In my knowledge I believe this mod would be actually very similar to the Flow regulator mod you can install on a e61 Group head (with this kit: e61 Group flow control device) and would be more appropriate than a dimmer which regulates the current going to the pump or by opening the steam valve to let water outside of the machine.


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## FairRecycler

GiovaD said:


> Hi all! very interesting things you're discovering here, thank you for sharing your knowledge.
> 
> I have an idea that is going in my mind since a while but unfortunately I can't try it out. About adjusting the flow of water while brewing.
> 
> So what I'm talking about is fitting a pressure reducing valve (like this one: Water pressure regulator or this one: Water pressure regulator AliExpress) to the tube connected to the pump, in order to have incoming water pressure up to 12 - 15 bar and the outgoing pressure to be set during brewing dynamically. Of course that means fitting a nob that goes outside the machine in order to screw and unscrew the upper part of the valve.
> 
> In case you're wondering that's more or less how a pressure regulator works: pressure reducing valve YouTube
> 
> In my knowledge I believe this mod would be actually very similar to the Flow regulator mod you can install on a e61 Group head (with this kit: e61 Group flow control device) and would be more appropriate than a dimmer which regulates the current going to the pump or by opening the steam valve to let water outside of the machine.


 Hi,

Yes, indeed it is the ideal way, and I'm sure I've seen it done on a classic before (others will probably find links too from here). My major concern is the size of these pressure regulators, at the time I was considering this option I couldn't find any compact version available on a sensible price. The installation would also be quite painful, in my opinion.

Meanwhile the dimmer mod what you mentioned is much easier and more affordable to implement and - to me - that gives satisfactory results. Not to mention, a dimmer mod could - or equivalent - potentially be controlled by a microcontroller, opening a bunch of exciting doors.

Don't get me wrong, I'm looking forward to hearing from your project if you decide to proceed, it is definitely a field worth to discuss here.


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## GiovaD

FairRecycler said:


> Don't get me wrong, I'm looking forward to hearing from your project if you decide to proceed, it is definitely a field worth to discuss here.


 Thanks a lot! Interesting to hear you have actually thought about it and looked at the possibility of implementing this.

Yes I would really like to try this out in the future, indeed I am planning to get a used Gaggia and try everything on it. Possibly in a few months I could really get my hands on it. In case I do, I will definitely post in this forum to spread some more knowledge


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## FairRecycler

Sounds like a plan.

I would also recommend to do some research on here and on other forums, I'm sure I've seen at least a couple of post about such a mod before.


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## GiovaD

FairRecycler said:


> I would also recommend to do some research on here and on other forums, I'm sure I've seen at least a couple of post about such a mod before.


 I have tried a few times with very scarce result.. in case you find something about this I would be very happy if you could link it in a new post 

Keep up the good work man!


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## PACMAN

@FairRecycler Are you still selling the pressure gauges? I need to sort the pressure on my new (to me) GC and the portafilter that came with it can't accept a pressure gauge, so I might as well just fit one into the case and be done with it. At least then I can set the OPV to 9 Bar and remove one variable. Is it still necessary to use a backflushing basket and set to 9.5 or 10 bar (ie static) or should I be 'making espresso' and check / set the pressure to 9 bar that way?


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## FairRecycler

Hi @PACMAN

Yes these are still available on eBay.

Yes, to set the OPV you'll need the blank basket, as the dynamic pressure would highly depend on grind size and preparation of the puck.


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## PACMAN

FairRecycler said:


> Hi @PACMAN
> 
> Yes these are still available on eBay.
> 
> Yes, to set the OPV you'll need the blank basket, as the dynamic pressure would highly depend on grind size and preparation of the puck.


 Thanks Peter. Fortunately the blind basket is one thing I do have (grinder, PID, tamper, beans, naked PF - the list of what I either still need or am waiting to arrive goes on - mostly still waiting for them to arrive)


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## light87

Hi there

Yesterday evening I just turned on my Gaggia Classic that I have restored over the last months. I have installed a pressure gauge flutter free from fairrecycler on the machine.

So I have just tried 2 shots yesterday and of course I also need yo adjust the OPV valve but I have seen that the pointer of the pressure gauge move with a lot of lag so It basically goes up when the shot is already finished.

Also when I adjust the OPV what I do if I screw its piston counterclockwise, do I lower pressure? Or the contrary?

Thanks


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## light87

light87 said:


> Hi there
> 
> Yesterday evening I just turned on my Gaggia Classic that I have restored over the last months. I have installed a pressure gauge flutter free from fairrecycler on the machine.
> 
> So I have just tried 2 shots yesterday and of course I also need yo adjust the OPV valve but I have seen that the pointer of the pressure gauge move with a lot of lag so It basically goes up when the shot is already finished.
> 
> Also when I adjust the OPV what I do if I screw its piston counterclockwise, do I lower pressure? Or the contrary?
> 
> Thanks


 Doesn't matter I have solved then.


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## PeteT

FairRecycler said:


> Hi @PACMAN
> 
> Yes these are still available on eBay.
> 
> Yes, to set the OPV you'll need the blank basket, as the dynamic pressure would highly depend on grind size and preparation of the puck.


 Hi @FairRecyclerany kits listed on eBay at the moment?


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## FairRecycler

PeteT said:


> Hi @FairRecyclerany kits listed on eBay at the moment?


 Hi,

I have postponed the eBay shop for a while, but I am happy to fulfill individual orders.


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## PeteT

FairRecycler said:


> Hi,
> 
> I have postponed the eBay shop for a while, but I am happy to fulfill individual orders.


 Thanks, I'll be in touch.


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## Sheffy

FairRecycler said:


> Hi,
> 
> I have postponed the eBay shop for a while, but I am happy to fulfill individual orders.


 Hi,

Don't suppose you can drop me a message? I can only send one per day.

Thanks


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## bbstrikesagain

Having just done a big mod (pre-heat coil, dimmer, gauge, PID brew and hysteresis steam temperatures, lighting), I have an observation about gauge needle flutter. I don't think I've seen all these points together anywhere in the previous pages, so here goes.

I'm using an Orman gauge with long demountable capillary tee'd into the boiler inlet hose. Can't seem to post pictures at the moment, but never mind. My gauge needle is fast responding, yet rock solid while ever the pressure is regulated by the pump or puck. Once I reach OPV opening pressures the needle flutters...

Originally, from before the big mods, I still had the "6.5 bar" spring in the OPV, and the needle was pretty stable, just a hint of a waggle at 7.5 bar with the OPV opening.

I changed to "9-bar" spring, thinking 9-bar could be a sensible extraction limit, but this made quite noticeable flutter at 10-bar.

My theory is that the capillary and/or gauge inertia, is enough to fully filter the mains frequency pressure pulses that come from the pump, so they don't reach the gauge, but once the pump mounted OPV opens the OPV is itself chattering, seating pseudo-randomly thanks to the vibes and pressure pulses, creating low frequency fluctuations in pressure, low enough to get through the effective low pass filter of the capillary and gauge.

It all makes sense now. More pressure and more vibration energy in the pump, more OPV chatter and therefore more gauge needle flutter.

Aside: The lower pressure OPV springs also left a lot of the dimmer's top end range wasted, merely varying flow in the already open OPV. My dimmer has a trim-pot to dial up the minimum setting, but I'm feeling it might be nice to have a another trim-pot to dial down the maximum too, so there's more precision in the mid range. Could then set dimmer max to not quite open the OPV, and therefore never ever see any flutter. Maybe time for a home-brew dimmer PCB, or circuit edit... Or might dialing back the maximum also affect flow for de-scaling or priming?

Upshots



I'm back to 12.5 bar OEM spring in (GCP pump mounted) OPV as more "dimmer+gauge friendly"


The OPV is back to its original purpose: a safety valve that doesn't open even during huge thermal overshoots in steam mode (that occur if you reach steam stat opening temperatures)


Pressure is now regulated by the dimmer and pump alone (unless I try to dial more than 12.4 bar...)


Gauge needle is rock solid (unless I try to dial more than 12.4 bar...)


Easy to demo the OPV flutter by sticking in a blind basket and turning up to 12.4 bar...


Like many, I do now have a dead-end capillary to the gauge, presumably now full of water. That nags a little, but I guess it's a common solution and, as it's pre-boiler, any tiny back flow water does at least get heated above 100°C...


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## FairRecycler

@bbstrikesagain

Wow, this is really impressive. I have never thought about this. Bear in mind I tested my versions without a dimmer on pre 2015 machines with the adjustable opv set to ~10bars , so I think the tube diameter or other orifices still has a lot to do with filtering the uneven pressure generated by the vibratory pump.

Do you know the ID of the capillary tube used in your setup.

BTW this setup sound brilliant, well done.

Thank you for sharing.


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## bbstrikesagain

FairRecycler said:


> @bbstrikesagain
> 
> Wow, this is really impressive. I have never thought about this. Bear in mind I tested my versions without a dimmer on pre 2015 machines with the adjustable opv set to ~10bars , so I think the tube diameter or other orifices still has a lot to do with filtering the uneven pressure generated by the vibratory pump.
> 
> Do you know the ID of the capillary tube used in your setup.
> 
> BTW this setup sound brilliant, well done.
> 
> Thank you for sharing.


 @FairRecyclerThanks. I made one schoolboy error and broke my timer. I'll post my full mod when its all together including timer. Just need a spare OEM basket to turn into a live espresso slurry thermometer too.

No idea the capillary size, but it is small. Seeing as it's you, I'll pop the lid and measure the OD, hang on... ..2.24mm OD. I recall the fitting holes at either end looked pretty small, less than a millimeter, but I'm not going to cut into the capillary. The gauge is really smart IMO, came as a kit, but I only used the capillary and gauge:

https://www.ebay.co.uk/itm/402272902041


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## bbstrikesagain

FairRecycler said:


> Bear in mind I tested my versions without a dimmer on pre 2015 machines with the adjustable opv set to ~10bars


 @FairRecycler Aye. The old OPV may be better, and is certainly mounted in a more stable spot, but could it still chatter in response to pressure pulses? The hose in the old models will have a lot less give too, so pump pulses may be stronger at the tapping point, but they should still be at pump frequency and so easyish to filter. Is there a good reason not to set the old OPV right out of the way, maybe 12.5 bar, when using a dimmer?

Another more subtle difference is the new model's CEME 3-way is supposed to be faster and have bigger less blockable internal orifices. I haven't checked that, I only have my own machine and didn't open the 3-way, but it could mean that boiler pressure is a little closer to brew temperature on the GCP? Is the CEME a useful upgrade for pre 2015?

When I dim my pump to 6-7 bar it has a really slow ramp up, maybe 10s to soak my puck, a sort of auto pre-infusion or poor man's gicleur? Maybe a good thing with the high flow 3-way?


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