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Posted (edited)
33 minutes ago, 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.

Quote

 

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.  

 

 

Edited by phario

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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.

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@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.

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@Blue_Cafe

4 hours ago, 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

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1 hour ago, 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.

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Posted (edited)

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.

 

Screenshot_2020-07-30-12-03-03-020_com.google.android.apps.docs.jpg

Edited by FairRecycler
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0.5 can get easily clogged or ?


CFBG Team

Buying expensive equipment won't make you barista!

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Posted (edited)
19 minutes ago, 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.

Edited by FairRecycler

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Posted (edited)
1 hour ago, L&R said:

0.5 can get easily clogged or ?

See my reference above about the gliceur: 

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.

Edited by phario

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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

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14 minutes ago, 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?

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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?

:)

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1 minute ago, 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?

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Posted (edited)
23 minutes ago, 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

23 minutes ago, 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)

 

23 minutes ago, 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 :)

23 minutes ago, 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.

Edited by FairRecycler
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Posted (edited)
21 minutes ago, 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.

Edited by FairRecycler

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Posted (edited)
19 minutes ago, 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! 🙉

Edited by phario

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19 minutes ago, 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.

22 minutes ago, 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.

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25 minutes ago, phario said:

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

Fair point

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Posted (edited)

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. 

Edited by phario
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@phario

On 31/07/2020 at 00:46, 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.

On 31/07/2020 at 00:46, phario said:

make sure the PTFE system can be capped

M5 16bar plug screw

On 31/07/2020 at 00:46, 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.

IMG_20200801_234118.jpg

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20 minutes ago, 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. 

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