1958 La Cimbali Gran Luce Automatica (Hydraulic) [Finished] - Page 11

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

She's absolutely beautiful Ryan. Inside, and out. Well done man, well done!!!

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

Heavy duty testing

Today I had some friends over, where we pulled lots of shots on the machine, including some fancy light roasts just to see if the Gran Luce could compete with today's machines. Apparently it competes pretty well :lol: . We also did some turbos, and were getting 90g shots. Saka was just pulled at the minimum volume of 20g for now. We had a livestream done, and will have some videos produced in the future.






The right group (with the chrome cap) squirted water when we pulled a max volume shot. I do not know if it came from the big piston or little piston, so afterwards I kept the volume on the short side without issue.

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

More testing

Over the past week I've been trying out different ratios and grind settings with the Gran Luce. I think I'm getting the impression that increasing the pressure line and tightening the grind is the way to go because the quicker piston travel will not allow the coffee puck to get as saturated as a slower (and lower pressure) stroke, and the tighter grind further reduces the puck saturation.



I also decided to play with the double sized shot after making this tigher adjustment. I simply end the shot early/remove the cup before the group is fully finished extracting.



I also wanted to show what happens if I don't keep tightening the group nuts between use. The gaskets and studs seem to settle on the groups each time I turn off the machine and allow them to cool. This may reduce the compression forces of the two gaskets (inside and outside), and when I forgot to tighten the gaskets for two heat/cool cycles in a row earlier this week, residual water that got between the group gasket when the machine was cold oozed out when heating up the machine yesterday. When I turned off the machine and allowed it to cool, it was almost finger loose.

I'd say at this point I have re-tightened the nuts 5 times, but when I was working with the Cimbali Eleva I had to do similar tightening with its curved gasket profile. Thus I am not super surprised. I'm dealing with double the gasket material thickness on the Gran Luce, and I may have to slightly tighten even a few more times after this. I try tightening the nuts to around 13-15 Nm for reference.

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

Explanation of the Hydraulic Group
I created three drawings to hopefully show how the hydraulic groups work. Two figures are in the drawings. The first one is a cross section of the group from a side view, where it does not show the group valve block, and the pipe that goes to bottom of the upper group is moved from its normal position to better explain the Hydraulic Circuit. The second figure is a diagram of the group valve body. Red arrows mean water is being pushed out to the Hydraulic Circuit exit, and blue arrows mean water is entering from the Hydraulic Circuit Inlet. There is a third drawing that shows the entire Hydraulic Circuit too.



There are two stages involved, the Resting/Extraction Stage and the Preinfusion Stage. By default the groups are in the former, where the big piston is forced to remain at the bottom of its housing by the Hydraulic Circuit. This also means the little piston is at the bottom of its respective group bore. The black knob that begins the shot extraction process is in the upright position.



The Preinfusion Stage begins when I turn the big black knob that actuates the group valve block into this stage. When the little piston is high enough in the group bore, it will push a pin that releases the group valve block and returns the black knob to its resting position. This also returns back to the Extraction Stage that forces the big piston back down. The resistance that the little piston pushes against ground coffee is what creates the brewing pressure, multiplied by multiple factors (around 4 I guestimate) from the Hydraulic Circuit Pressure due to its smaller diameter of 52mm compared to the big piston's 128mm diameter face.



This does differ from the patent just a tiny bit, but that is because the four plungers inside the valve block are flipped upside down compared to mine. The function is identical, but items 28 and 29 are flipped on my block. The casting valve block itself is the same from the two diagonal tubes, two horizontal tubes, and four big threaded holes for pipes and little holes for cap screws.



-Ryan
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pizzaman383
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#105: Post by pizzaman383 »

Very cool!!

I notice that this gives line pressure preinfusion and the inlet water path looks quite similar to that of a spring lever group head.
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IamOiman (original poster)
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#106: Post by IamOiman (original poster) »

Preinfusion pressure should be whatever the boiler is at during that time, but the path itself is very similar to levers. There is a one way valve that can act as a shutoff valve if the rod is screwed down all the way.
-Ryan
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#107: Post by IamOiman (original poster) »

Checking out the leaky pistons

So with the right group spittling water every so often when I pull a shot, I decided to pop off the piston assembly. It's actually pretty simple to do (relatively). I simply undo the four 1/4 inch nuts securing the upper group and two pipes, and the entire piston assembly will just pop up and out. However, this had water in the bore, so I had to drain it away first with a syphon tube before it could come all the way out.






I could see that coffee residue was on the top piston seal, which means water was getting to the top of the piston during extraction. It could also be the cone gasket inside the big piston assembly but I think it is primarily the little piston seals being too small (also indicated by occasional dripping when the boiler is at pressure).





For good measure and comparison I also took out the other group too just to check it out. It was less leaky but water residue was still present.


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

Further troubleshooting and questioning continuing to use the Gran Luce

I went deeper just to see how the cone gasket was faring, and also to show how I drain the upper groups of water. Even when the Hydraulic Circuit is off, water remains in the group until I empty it. I simply push the piston up and down by hand over a bucket to squeeze out the water. Then I can undo the six bolts securing the aluminum ring against the big bell housing and pop everything out.









Honestly what I saw reminded me that having aluminum parts in contact with water is sort of not a good thing (just like the microcimbali). Even though they were wet still, I could see hard water deposits and a little corrosion action going on inside from just a few weeks of on and off use of the Gran Luce. Even with a filter this would slow the process against the aluminum. Seeing this is making me really ponder how much I want to focus my efforts on resolving my issues. I have the new measurements for the improved piston gaskets along with the cone seal, but I don't think I really want to use this machine that results in its slow decline to inoperability.




I will still test to see if the piston seals are the main culprit. I placed both little pistons attached to the rods back into the groups in the resting position. I will turn on the machine and can observe from above if water is being pushed up past the top seal.

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

I will be playing with this machine in the future most likely, but I completed my original goal. I wanted to bring a hydraulic machine back to life, one that as of today I know of only three others that even work (or have worked in the past few years). I completed that and was able to try out some espresso shots, and document the entire process and showing the group in action with diagrams and explanations promulgated so that others may hopefully see what I experienced and saw.

For the aluminum question, I think long term coating it would be the solution along with using a filter for the hydraulic circuit line. For now, I have prepped the Gran Luce Automatica for display and drained the groups and boiler fully. Before draining the boiler I confirmed this morning that the piston seals do leak after turning on the machine, and will order larger diameter ones.


I will leave this last post with the fully assembled machine, all body panels attached except for the sight glass plastic (I'm too nervous to bend it back into place right now if I am going to work on this machine in the future, as I need to take it off everytime I take off the body panels). I kept the upper group loosely assembled, hand tight for most nuts and pipes, so that I can easily take everything off again when I get the updated seals.

This is without a doubt the coolest espresso machine I have worked on so far from a technical standpoint; damned be the water usage and 49 gaskets per group :D .





-Ryan
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pizzaman383
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#110: Post by pizzaman383 »

Did this machine come to market before the spring lever machines or after?
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