Yet Another Lever Project (with a weird twist) - Page 3

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XS750AU
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#21: Post by XS750AU »

Paul_Pratt wrote:It's a safety valve.

The reason why they there is no pressure switch has been discussed countless times before. You will note that older machines always had 2 elements, a high power and a low power. Once up to temp turn to low power and it will idle away with an occasional hiss from the safety valve.

The missing plunger is easy to fabricate I do those all the time. I almost always use the wobbler weight with a pressure switch. If you machine the mating surfaces of the parts or add a gasket they are silent.

Whilst they may vent some false pressure on start up (you would still need to purge anyway, it would never bleed it all out) they will never open and allow the boiler to cool down to atmospheric pressure and you would still have a sealed boiler with a vacuum.
110% agree with you. If we define a vacuum as the boiler has a lower pressure than the atmosphere, then there is no way that valve can allow the boiler to vent to atmospheric pressure ( if it is sealing correctly).
It does effectively regulate the temperature with the constantly energised low power element. The boiling point of water increases with pressure (this is how pressure cookers work) This valve will most likely be calibrated to 1.5bar which means the boiling point is 111.4C or 232.4F. Once the water reaches this temperature the boiling water and steam pressure will pop the valve. Some just sit there and wobble keeping a pretty regular pressure and temperature. The design relies on the lever group acting as a heat sink and cooling the brew water to 93C when it hits the puck. Or if you really think about it. To make sure the brew water is at 93C when it gets to the puck the boiler water must have a temperature greater than that achievable with atmospheric pressure.

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Paul_Pratt

#22: Post by Paul_Pratt »

IamOiman wrote:If the machine was a daily driver would you still use a wobbler weight or use a modern safety valve?
I use the wobbler weights all the time, once they are all seated correctly they work very well.

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civ

#23: Post by civ »

Hello:
Paul_Pratt wrote: ... all the time, once they are all seated correctly ...
Quite so.
Like any pressure cooker I have ever come across. 8^ )

Cheers,

CIV

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Paul_Pratt

#24: Post by Paul_Pratt »

I thought I had the missing part but the one I had in mind is a little different. You would need to modify the design to include a point on the top.



There are quite a few designs, some with retaining bolts, some without. The triangular shaped lower section seems to be the most common. The 2 at the lower left are ones I made a few months ago.



I like to use the old safety weights as they are fun and I don't mind them hissing from time to time (or when you pull a shot you bump the machine and the weight moves around). I also turn off my machines every day at the office so in the morning I just remember to purge the false pressure out after 20 mins.

If you were at home and had the machine on a timer it would be very useful to install a vacuum breaker, also if you were using it in a shop and left the machine on overnight a certified safety valve and a thermal fuse would be good additions.

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IamOiman

#25: Post by IamOiman »

I've been toying with using a wobbler weight on my Mercurio as I would not intend it to be my permanent daily driver. It's not very hard to switch out the safety valve with the weight and vice versa though, which is why I asked originally.

Not to deviate too far from the thread but how is a triangular shape machined on a lathe (or if it's done via different method)? All of my Faema machines have this triangular piece with the curved surface on top.
-Ryan
Using a spice grinder violates the Geneva Convention
LMWDP #612

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Paul_Pratt

#26: Post by Paul_Pratt »

IamOiman wrote:Not to deviate too far from the thread but how is a triangular shape machined on a lathe (or if it's done via different method)? All of my Faema machines have this triangular piece with the curved surface on top.
I cut the flats on a mill. I use a hex collet block in the vice to hold it securely and so I can get the 3 sides cut.

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karl_a_hall (original poster)

#27: Post by karl_a_hall (original poster) »

Paul_Pratt wrote:It's a safety valve.

The reason why they there is no pressure switch has been discussed countless times before. You will note that older machines always had 2 elements, a high power and a low power. Once up to temp turn to low power and it will idle away with an occasional hiss from the safety valve.

The missing plunger is easy to fabricate I do those all the time. I almost always use the wobbler weight with a pressure switch. If you machine the mating surfaces of the parts or add a gasket they are silent.

Whilst they may vent some false pressure on start up (you would still need to purge anyway, it would never bleed it all out) they will never open and allow the boiler to cool down to atmospheric pressure and you would still have a sealed boiler with a vacuum.
I'm honored to have Paul jump in. Glad you confirmed that adding a gasket will help with noise... that's what I had cad'd up (cousin is a machinist and wants cad... thou I was taught mechanical drafting in engineering school and wish he liked hand drawn...). I'll take a look as to the convo on pressure switches. Do you have a personal preference when adding one as to specific brand/model? I have a spare new one from an old project... but was curious your thoughts.

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karl_a_hall (original poster)

#28: Post by karl_a_hall (original poster) »

A more general update... I got delayed on working and posting with a super busy season at work, installing a whole home humidifier, and a sick kiddo. But anywho... progress...

Completely disassembled with body panels currently at powder coat and some walnut purchased for a few wood panels I'll be fabricating.





I also finally got around to making a jig to hold the group so I could attempt to get the plunger off. It was a heck of a janky setup, and I did wrap the spring with a Kevlar band when actually working on it (not pictured)... but eventually got the plunger off without too much issue.





One question... from the thread I mentioned in the OP... I bought these springs https://www.espressoparts.com/faema-fu ... on-spring . But despite the helix seeming really similar the new springs are mega long. I've been surprised by spring set before so was hoping someone can tell me that amount of set seems right and therefore the new springs are correct... honestly the research I've done makes me think they are but was hoping for a gut check.



Thanks again everyone! Stay tuned as the frame pieces should be back soon and the group parts back from the polisher as well.

Thank you again so much!

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civ

#29: Post by civ »

Hello:
karl_a_hall wrote: ... despite the helix seeming really similar ...
... that amount of set seems right and therefore the new springs are correct...
This type of spring is a compression spring and the main physical characteristics are OD, ID, wire diameter, pitch and length.
From what I see in the photo you posted, the original spring seems to have ten turns/coils and the one you purchased seems to have twelve, so even if all the other physical characteristics match, the length is not the same so I do not think it will fit correctly.

There are other characteristics that are part of a spring's specs which have to do with how it behaves when compressed such as the different lengths it can have under different load scenarios.

Check this web page for more compression spring information.
You could drop them a line and see if they can help you with the right springs for your machine.

Cheers,

CIV

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karl_a_hall (original poster)

#30: Post by karl_a_hall (original poster) »

civ wrote:Hello:


This type of spring is a compression spring and the main physical characteristics are OD, ID, wire diameter, pitch and length.
From what I see in the photo you posted, the original spring seems to have ten turns/coils and the one you purchased seems to have twelve, so even if all the other physical characteristics match, the length is not the same so I do not think it will fit correctly.

There are other characteristics that are part of a spring's specs which have to do with how it behaves when compressed such as the different lengths it can have under different load scenarios.

Check this web page for more compression spring information.
You could drop them a line and see if they can help you with the right springs for your machine.

Cheers,

CIV
Thanks CIV... I'm quite familiar with spring characteristics... what I'm not used to is not knowing initial conditions. Many replacement springs will have different coil numbers but still have the same initial performance characteristics... at least in the world I come from. In small wire applications we use helix vs pitch in our vocab... hence the misstatement earlier. What usually isn't difference is initial length. Hence why I was curious about common set lengths in this application. I usually see spring sets that can be up to 50%. So what I'm not as familiar with is common sets that lever springs might take... in searching the forum, I see some similar set amounts from before and afters.

The real issue I'm imagining is that my overall compressed length will be too long so that I won't hit the toggle position... and I think that alone might rule out a 12 coil spring unless the coils are smaller diameter (gotta measure that).

I guess this is what I get for buying a machine that didn't have large production numbers or good documentation.

Thanks again CIV!!!!