La Cimbali M15 refurbishing

[renier]

Hi, I have just bought this lovely 3group La Cimbali M15 TC and I am going to refurbish it or at least try. When I first saw the machine I fell in love with these strange hydraulic groupheads. Though it is not a vintage machine I do feel it did play a part in the history of the espresso machine and there for worth restoring/refurbishing . The machine was made in 1976 and I think one of the 1st machines that automatically measured the shot volume. refurbishing this machine is going to be a 1st for me. I do have some technical background and I am working as a barista at a small coffee shop my wife and I own.
I have been looking for information on this machine on the internet, but there is very little to be found or at least I can't find someone that actually knows how it works. luckily there is still some parts available. I have found some drawings of its heads an boiler but it still does not explain its workings.

The first thing I don't understand about the M15 is that it has two inlet hoses - one going into the boiler where the head is attached to boiler, and one that goes directly into the grouphead. I know the machine should have a external pump but the previous owner misplaced it somehow. He also told me one can use almost any pressure pump since all that this pump does is to fill the boiler. The boiler has no auto water levelling device and this is done manually. He also clams that he plugged the second inlet straight into his normal plumbing cold water supply (±3bar pressure), and this is sufficient to drive the hydraulic heads.
To me this sounds wrong. I would imagine it the other way around with the external pump driving the hydraulic system and surely 4bar would be enough to be able to fill the boiler that runs on ± 1.2 bar of pressure. Please see the attached images

I also want to examine the possibility of converting the machine from three phase electricity to single phase. I am sure it can be done since it is only the boiler element and the very old pressure switch controlling the element that runs on electricity.

I am thinking of stripping down the whole machine and descaling everything but I would first try to get it running just to be able to assess what needs to be replaced and what it will cost.

If anyone knows anything about this machine please let me know.

[Paul]

hi renier,

your machine works almost (not quite) like a lever machine. A piston is used to compress water thru the puck. Your fella has two pistons per group. Cold water at mains pressure is fed into the upper chamber actuating a large piston. This is attached to the same shaft as a little piston below it. The lower piston forces boiler water thru the puck. Now, the surface area size difference between the pistons is how the machine turns 4 bar (water inlet presssure) into 9 bar (brew water in the group).

so . . . your man was right when he said that both inlets are fed from the mains supply. Clear as mud?

parts - afaik, most bits are available for this machine. I can recommend some suppliers if you like.

3ph -> 1ph: easy, either requires a new element or a simple rewiring of the existing one.

Cimbali hydromatics have a good reputation and were made in some form from about the early 60s to early 90s.

good luck

[renier]

Thanks a million Paul

For the 1st time I understand how it works, its quite an amazing concept. I did not realize there is two pistons in each head

I am still not convinced that the external pump of this machine is used to fill the boiler. It still make sense that it should be used to drive the hydraulic system instead. Surely water pressure from ones main supply will vary from time to time and will cause the brew pressure to vary as well. The external pump will deliver a consistent pressure instead. I suppose when I have the new external pump I will be able to test my theory.

I am 1st going to do the rewiring and install a new pressure release/safety valve. Then I am going to try to start-it-up to see what happens.

Is there anything els that I should do before attempting to switch it on?

[Paul]

Do try with just mains pressure first. The whole design purpose behind this kind of machine was to automate the process somewhat (compared to a lever machine) without resorting to using a pump. I am worried that if you supply water at too high a pressure (say >5 or 6bar) that you'll end up damaging something.

Aside from that, If I ever get the urge to try out an old machine before tearing it down, I always run the heating circuit across the multimeter to check the element resistance and to look for earth faults.

[703Eric]

Hi Renier, Welcome to the club! I for one love to rebuild machines. If its not two much trouble I would really enjoy seeing the break down and rebuild! Good Luck!
Eric

[renier]

Hi Paul
I will try it first with just mains pressure only and will also get my friend to check the heating circuit for faults.
Thanks for the sound advice.

Eric
I will take photos and post them as I go along. Have to warn you though it might take me a long time to complete.

Cheers
Renier

[renier]

I have striped down all the cover/panels, but the rest I have left all in tact.


It has a old mercury pressurestat. What an amazing device! another first for me.



I have converted the Cimabali from three phase to single in the way it makes sense to me. It has four wires Blue, Black, Brown and Green-earth. I have only use the Blue Brown and earth.
The element thus only run on 2000w and not 5000w. It works but takes forever to heat-up. It has taken 5 hours to get to 90 degrees Celsius. I wonder if it is at all possible to heat it all the way if it is configured like this.

[mhoy]

You may want to insulate the boiler to help out heat loss when running at much less than the original power.

Mark

[renier]

Good idea, It is quite a large boiler and it does radiate lots and lots of heat. Thanks

A friend of mine will still help me to rewire it properly so it can use 100% of the element.

It did reach 0.5 bar pressure and was enough to show a leak on the element gasket. I think I should first replace it before starting up again. I am also very curios to see how bad the scaling is inside the boiler.
I know it is still early days but I find this project quite exiting. Every step is a new discovery that leaves you amazed with the simplicity yet cleverness these machines were build with.

[renier]

Ok, I have gone ahead and took out the element. I was really expecting the worst, with thick scaling all over. To my surprise there is absolutely no scaling. Quite strange for a machine that is 30 years old. Unfortunately I don't know it's history. I suppose it could be possible that it was standing in a store room for most of it's 30 years.


All three its portafilters appears to be evenly worn. This makes me think that it could be its original PFs and it does not look like it worked all that much. however it may be it's great news for me


We also realized it will be easier to buy a new 220v single phase element than using the existing one. I will phone around for prices next week.

[renier]

I now know the following: The pressurestat seems to be fine, though I could not get the machine warm enough to test it. The boiler is 100% only need a new gasket for the element. The element is working but I am going to have to replace the 380V one with a 220V element. The steam wands is working fine but will still like to replace them with brand new shiny ones. The hot water outlet is still perfect. The boiler inlet lever and valve is working 100% and my normal water supply should be sufficient pressure and I don't need an external pump to be able to fill the boiler.

Here is the bad news and the things I don't know:
The hydraulic heads
I have no idea how they should be operated. I have no user manual (have requested one from Cimbali about a week ago).
I have plugged the my main water supply into the heads inlet and water immediately runs out from two bottom screws in the distributor (the gadget attached to the head where one can choose between a single or double shot and also consist of a small lever that activates the flow.
I have no idea why this is happening and I suppose I will have to open it up to be able to see what's happening.
Here is a link to the diagrams of the hydraulic group and the distributor:
http://www.purecafe.co.za/thejam/CIMBALI_M15_grouphead.pdf Hopefully it is just some gaskets that needs to be replaced.

[renier]

I opened one of the hydraulic groupheads, starting from the top. It was quite easy and I will be able to put it back without having to replace any seals.
Now that its open one can see how it actually works. The top chromed dome is a cylinder with a piston inside. This piston is connected to a rod that is also connected to a smaller piston that can be seen when you remove the shower screen. So pressure from the top forces both the pistons down simultaneously. One only need a little pressure in the large top cylinder to be able to produce 9bar of pressure in the bottom cylinder, basic hydraulics.

This part is simple to understand and there is view parts involved. The distributor on the other hand seems far more complex. This mechanism sets the piston position to poor a single or double shot. It has a lever to activate the flow. It also has to redirect the water to push the pistons back into position once the portafilter is inserted. To take them apart will be my next step.

[renier]

I have opened up all the groupheads and is currently busy descaling all the parts.
I now know what parts I need to get this baby up and running. It is mostly gaskets.
Here is a photo of all the parts I need to get per grouphead:


I have contacted the supplier that initially told me it wont be a problem to get these parts and now it seems it is not so commonly available and nobody in SA have stock for these parts. They now have to ship the parts in from Italy. I am waiting for there quote and in the meantime I am calculating what it will cost me to bring the parts in myself. With high shipping costs it will be better to buy all the parts from a single supplier. But so far I have not found a supplier that stock all the parts I need. If anyone have suggestions to where I can buy these parts, please let me know.

[renier]

Just a photo of some of the grouphead parts:

[coffeewarbler]

I just got one like yours but 2 grups or heads. Same color in Vancouver Canada, I will tested tomorrow. How your's gping with the parts?
I am nw in this but any advise will help. The last owner told me they change all the piston and heat element, Was serve but he got a new one cimbali and storage this for long.

Fidias