1958 La Cimbali Gran Luce Automatica (Hydraulic) [Finished] - Page 7

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
austinado16
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#61: Post by austinado16 »

:shock: WOW!!

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IamOiman (original poster)
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#62: Post by IamOiman (original poster) »

Assembling valves

I put together the big group valve blocks, 28 gaskets per block :shock: .

6 x 1.5mm o ring x 7
26x20x2mm PTFE gasket x 4
Custom U cup gasket x 4
12x7x2mm PTFE gasket for u cup gasket shim x 4
8x6x2mm PTFE gasket x 1
15x6x4mm gasket x 4
11.5x6x2mm PTFE gasket x 4 (for sealing pipe connectors)

I had to punch a tiny 8x6mm gasket for one of the screws in each valve block as the o ring was too small to seal properly in a countersunk hole of a little 1/4" hex bolt. All of the valves I am assembling will be tested with my FloJet before I actually install them.







The hot water and steam valves are identical, and are a little simpler than the group valve block. It uses the same gaskets as noted above. The bushing/gasket holder for the 15x6x4mm gasket has a little copper washer that lies against a much bigger spring than what is used on the group valve block.
26x20x2mm PTFE gasket x 1
Custom U cup gasket x 1
15x6x4mm gasket x 1





Here is the shutoff valve in a little more detail. It's just like the one way ball valve in the dipper tube, but in addition there is a threaded rod above that will push the ball against the teflon gasket and force a seal against it when tightening that rod.

-Ryan
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IamOiman (original poster)
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#63: Post by IamOiman (original poster) »

Switch assembly and gasket fit test

The original power switch was cleaned up. With the new heating element I am using, it will be at the top end of the rated current for the power switch of just above 15A (It's a nominal 3400W element at 220V). I cleaned up all the terminals and contactors for each pole, and cleaned off the rust on the turning mechanism. I lightly lubed it with some WD-40. I kept note of how I installed each pole selector, and tested each one after with my Multimeter; the 0.2Ω on the screen is just a bias and not the actual resistance of each pole. I intend just to have an On-Off configuration so I only focused on the 0 and 1 position.










I noted the piston seals I ordered were quite tight, too tight actually for me to easily move the piston up and down in the group. It is very difficult to insert the piston with these new 53mm seals into the bore, and becomes very, very difficult to remove the piston once the seals are squished in. I had three original seals that were still pliable, and they fit very easily without issue (the seals on the left piston), but keep in mind the original seals may have a slightly smaller diameter than their original specs from age/use. It is also a very tight fit between the piston OD (51.9mm) and bore ID (something like 50.025 or 50.05mm), which surprises me in how tight of a tolerance I am seeing. I am working on a solution for that, possibly trying 52.5mm for an OD on the piston seal.



-Ryan
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IamOiman (original poster)
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#64: Post by IamOiman (original poster) »

So it turns out the piston seals were made out of spec, which is why they were so tough to install and remove into the group bore. I have new ones coming over soon but that was good to confirm with the manufacturer.

Group valve block testing and new element
With the arrival of another parts order, I was able to test the group valve blocks under pressure for the first time. The big question I had was whether the u cup seals worked. Turns out the brass caps were not threading in deep enough, and I needed to insert homemade PTFE shims (12x7x2mm) to ensure the u cup gasket could be compressed to make a good seal.




I discovered that if I don't have something covering the top of the four rods, they will launch themselves from the pressure of the flojet (2.7 bar circa) :shock: . They did not go far but it was a big surprise for me as I was met with a squirt of water before turning off the pump. After securing the pins, I connected the pump line to different parts of the valve, and I also pressed down the pins to distribute the pressure among the entire block valve multiple times and checked after a little water for leaks. There was one other little leak from a nut that just needed tightening, but overall the blocks appear to seal pretty well now.







I got my new heating element in a different order. It is from April 2007, and I measured a total resistance 15.8Ω. This is a little over 14A and 3600W on 240V.

-Ryan
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IamOiman (original poster)
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#65: Post by IamOiman (original poster) »

Complete group valve block assembly

I fully assembled one of the group valve blocks this evening. The four pins are pressed by a big brass camme on top with a shim plate between the pins and cammes. I lubricated everything with my food grade grease since water should not contact these areas. The camme is secured to the toggling rod with the bakelite knob via friction and a 3x16mm roll/spring pin (it's actually the same pin as used on San Marco lever group to eye piece). There is a spiral torsion spring that keeps the assembly under a specific orientation, but with it not installed on the group it will not be in the right position at rest.









This block now contains 28 gaskets with the added ptfe shims, really crazy design Cimbali made for brewing espresso!


-Ryan
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Ben Z.
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#66: Post by Ben Z. »

This is my favorite thread on HB.

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IamOiman (original poster)
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#67: Post by IamOiman (original poster) »

8) I got frustrated when I couldn't find great examples going into detail how the Cimbali hydraulics work (besides one Kaffee-Netz thread), so I decided pull a Thanos and say fine, I'll do it myself
-Ryan
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pizzaman383
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#68: Post by pizzaman383 replying to IamOiman »

I am very interested in how these work.
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Chert
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#69: Post by Chert »

I'm astonished such a type of machine was ever produced. It seems over the top complicated to produce relative to other designs of the era.

Ryan, do you agree, or have you been asking yourself why such a design came to production? If so, why do you think the designers thought it was worth it.

Great thread, and thanks for sharing.
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IamOiman (original poster)
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#70: Post by IamOiman (original poster) »

I think it was to reduce the training needed on the barista to use this machine compared to levers, where the barista only needed to twist the group valve block knob to start pulling espresso. However, I feel like it's a minimal difference in skill for the amount of design and maintenance needed on a hydraulic machine. I can't imagine needing the service this machine in a commercial environment. Lots of little things that don't assist with servicing ease. I have no idea how this was approved by Cimbali upper management :shock: .

The arrival of the E61 not long after hydraulics were introduced sidelined these machines, so I can't say how much a negative response would have developed over time, but perhaps the newer Cimbali hydraulic machines starting with the M15 was a reflection of how to improve and simplify the original design (and not use aluminum in the upper group). The Gran Luce and Pitagora used the style I am working on now.

But then again perhaps it was just for flexing technical know-how, where it's a pain to service but looks cool when working (hint hint, Italian supercar design theory :lol: ).
-Ryan
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