1958 La Cimbali Gran Luce Automatica (Hydraulic) [Finished] - Page 8

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austinado16
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#71: Post by austinado16 »

These updates are fantastic! I'm extremely impressed with your mechanical and restoration skill! I can't wait to see it all finished, and I hope you post a video, because it's going to amazing to listen to all the noises this makes during warmup and during brewing. It's quite an engineering masterpiece.

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

The US Patent on the Cimbali Hydraulic Group

I was dead wrong actually as to why the hydraulic group was made, at least according to the design patent. I found the US patent of this group, filed on 24 March 1959 number 2878747. The official inventor is Vittorio Cimbali, filed with the aid of an attorney. The official declaration as to why this group design exists is to reduce overheating of multiple coffees pulled in a short time period by using the colder water of the hydraulic circuit to cool the group, which is stated in the first few paragraphs of text and at the end on the last page.

The group itself is a little different in appearance compared to mine, and I had to look a little closely. The group valve block camme and pipe connections are a little different. Specifically, Item 28 and Item 29 are flipped on my group. Item 29 in the patent is the chamber below the large piston with 128mm seals, and Item 28 is the chamber above this same piston. The patent goes on to describe the action of brewing espresso. The resting state of the group from a valve perspective is Figure 7 (where the piston is at the bottom of the group bore/chamber).

The camme/valve settings are a litte different on my Gran Luce, but the theory of operation is identical.
  • When in resting state (Fig 1 and 7), the big piston is forced to the bottom by the entry and pressure of water above it from item 28.
  • When the knob is turned to activate the group and begin extracting espresso (Fig 1 and 8 ), the valves are adjusted by the camme such that water pressure from the mains line (marked by E in Fig 4, 7, and 8 ) will begin entering item 29, forcing the water out in item 28/above the big piston and into the drain circuit (marked by S in Fig 4, 7, and 8 ).
  • When the small piston is high enough, there is a lever arm (Item 23, 24, and 26) connecting to a pin inside the group bore (item 27) that will actuate the camme when the small piston comes into contact with the bottom of the pin, returning the valve position back to Fig 7, where water entering the top will force the big piston downwards.
This last bullet point is what creates the actual brewing pressure via Pascal's Principle, where a big diameter piston with a small pressure can cause a small diameter piston to have a large pressure. The operating pressure of the hydraulic circuit is circa 2 bar, and will multiply it by 3-4x to achieve the necessary brewing pressure for espresso.




The patent states that during this cycle of operation, the group is cooled from the water drawn in the hydraulic circuit. It is a self regulating group that in theory would not overheat as a result. I am super interested in seeing how accurate that is when I can begin pulling shots. I still need to figure out how to set up a pressure line of around 30 PSI. I think I need an accumulator tank that can expel 1 liter of water in circa 25 seconds without losing pressure + a pump that can supply that tank. Am I going in the right direction with that?

Here is the full text from the same patent if you want to take a look yourself. I will also try to demonstrate the step process of extraction and operation of the group.

-Ryan
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LittleCoffee
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#73: Post by LittleCoffee »

OMG!!!!!!
Vittorio was one of us! Relentless pursuit of THE God shot no matter what the complexity!

So what you're telling me is that you're restoring the 50s equivalent of the Decent?!? Incredible!

Ps this is also my favourite thread on HB so thanks for taking the time and effort over it!

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

The selector assemblies

The Cimbali Hydraulic group has a selector rod assembly that allows the barista to pull 1 or 2 espressos in terms of volume. There is a brass rod with a hook that is secured by an L shaped chromed housing, and is secured with a little pin. The little pin can secure the selected setting by tightening a 1/4" screw pushing a black felt cushion. I do not know yet if the screw needs to be tightened during operation to keep the selected setting. In the patent above it's analagous to Item 23, 24, 26, and 27.

On top is a brass piece that has a long, narrow pin which is what actuates the assembly when the piston inside the group bore presses up against it.





The selector assemblies attach to the aluminum housing that rests on top of the lower group via a grooved shaft with c clips. The L gaskets are now cut so the selectors can fit.





Normally, the selectors are secured in a neutral position by a small spring, but I wanted to show how the selectors work. To select 1 coffee, the brass rod is pushed inwards. For 2 coffees, the rod is pulled outwards. These following two pics show how the pin inside the group bore will be in a higher position with the latter (2nd pic).

-Ryan
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austinado16
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#75: Post by austinado16 »

Seriously: You put a steering wheel on this and it's a Ferrari. You put an espresso cup in front of it, and it's an espresso machine.

It's incredible.
Thanks for sharing the patent info, and for the latest restoration photos/update.

Also, good luck ever making coffee with it. 1) It's way too nice 2) You'll need some sort of upper level education :roll:

Jed
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#76: Post by Jed »

Echoing what others have said, thank you for documenting this. Your work is fantastic and it is (to me) the most fun thing happening on this site. I love a good project but have been too swamped with work to take on anything in the last few months. I appreciate getting to live vicariously through you.

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

It's certainly pretty unique if nothing else, and I am really enjoying what I am finding in the process.

Dipper anatomy and water inlet
I really quickly wanted to show the dipper tube of the group. It has a one way flow ball that is (as far as I know) the earliest model of machine that a modern Astoria seat can fit. As stated earlier the 3mm thick PTFE gasket is only purchaseable with the brass piece, but I needed to replace two of the four seats anyways. One of the two dippers has a CIMBALI MILANO written on the nut, a fun little detail normally hidden from view.



The water inlet has similar gaskets to the prior assembled valves, but instead of the u cup gasket I needed to use packing cord for the plunger rod. I had to replace two rods that are the pinions for the inlet lever, one 6x20mm Grooved Pin Shaft and one 5x25mm Grooved Pin Shaft. The inlet handle can extend out for additional leverage, and can turn 90 degrees when not in use to rest against the front of the machine.



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

hydraulic group assembly

I was going back and forth on whether to assemble the groups after they are on the machine, and decided to assemble one before doing that and partially assemble the other group. The groups received new 1/4 x 2" UNC headless studs with a tiny 1/8" allen socket drive on top for easy installation. I reused the original brass nuts and washers for holding the group block valve and upper group. The portafilter gasket is a modern cimbali conical style made of silicone that I decided to use over the original flat rubber ones.







After inserting the piston rod and lubricating it, the upper aluminum group could slip one. I made sure to keep it centered to minimize rubbing between the rod and brass sheath within the group. The custom cone gasket is under the red plastic cap with four pin holes.



The big piston was installed as shown in the following pics. I was very happy that I can still get the big 128mm seals without issue (they were €4 each on eevad roughly). The entire assembly was secured by the top brass cap and tightened.





It is a little hard to see, but the piston selector will create a maximum piston height delta of around 6mm for additional volume of the espresso shot. I am not going to install the big group cap until I confirm the custom piston seals on the bottom of the rod actually seal correctly.


-Ryan
Using a spice grinder violates the Geneva Convention
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IamOiman (original poster)
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#79: Post by IamOiman (original poster) »

Cackles maniacally

I am waiting for a few BSP parts, but here is the gist of my setup for the hydraulic circuit. As stated above, I have a hose faucet that is near my workshop area that I intend to use to supply water for the hydraulic groups. I needed a hose to reach the distance between the faucet and my test bench area, and after that I have the following setup:


Going from left to right (roughly):
  • 25 foot hose with 3/4 Hose Thread
  • 3/4 FHT to 1/2 NPT adapter
  • 1/2 FNPT T fitting, where a purge valve will be installed (all 1/2 NPT)
  • 1/2 MNPT straight fitting
  • 1/2 to 3/4 NPT adapter
  • 3/4 FNPT Pressure regulator that allows me to set my pressure (in theory) that is not the inlet water pressure
What I don't have yet is an NPT to BSP adapter and a BSP braided hose going into the hydraulic inlet of the Gran Luce. This is not the optimal efficiency with fittings, but it's what I can quickly scrounge up. I will definitely be doing leak tests since it is my first time dealing with NPT.
-Ryan
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IamOiman (original poster)
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#80: Post by IamOiman (original poster) »

So this is how the fittings go together. There is a 3/8" BSP thread on one end that will connect to the hydraulic inlet (shown in the photo with the red circle), and the other end attaches to a hose. When my sealant cures I'm hoping it will hold the 50-60 PSI the house inlet water pressure is likely set to. I hand tightened each fitting and cranked 1-2 turns additional post finger tight for the npt fittings. I used loxeal 18 as my sealing assistant.


-Ryan
Using a spice grinder violates the Geneva Convention
LMWDP #612