Hello:

I have recently acquired an older Cimbali Junior D/1 with a matching Cimbali Junior Max grinder, both in almost new condition (both manufactured in 2000) and for a very (very) reasonable price.

The D/1 is the plumb in model with dosing device, autofill and vibe pump, fortunately with no electronics.
One thing I can say is that everything I was led to believe a Cimbali machine was in terms of quality, design and craftmanship is true.

This does not mean that I will be leaving my favourite lever, a La Pavoni Shirley that makes my morning espresso every day, but I digress.

From what I have read at HB (and experienced first hand), the Junior has to be studied and understood to be able to produce the great shots it is capable of, an important part of that process being temperature monitoring.

I think (?) I have found a place where I can place a probe, much in the way the E61 probes are placed in many HX machines here at HB.

Here's a drawing originally scanned from a La Cimbali manual, published by Dan Kehn, downloaded and modified by me. It shows a longitudinal section of the D/1's brewhead which I have (up to now) found to be accurate although a bit more exploration on my part is needed.



Here's a close up:



What I can say for sure is that, once the M6 screw is removed, I can insert a full 120 mm. of stiff wire inside it, practically up to where the three way solenoid valve is located, although I still have to find the exact point where the brew-water path can be intercepted by the probe.

My guess is that a Swagelok / Omega thermocouple combination will work well to get good readings from that point.

The question is: has any owner of a Cimbali Junior done something like this before?

Thanks in advance,

CIV

Edited 02/03/10 @ 20:00 - added close up photo.

Maybe it's possible to use the same custom fitting as for the e61? It would be really nice if it's just plug 'n' play

Here's a thread about the fittings:
Monitoring Brew Temperature - E61 & Silvia

Hi guys,

it should work, the only problem I see here is getting a leak proof tight connection between the Swagelok fitting and the surface of the brass element the screw sits in. That element is round on the outside, so you would have to somehow make it flat on the front, at least the area around the hole, so that the compression fitting can make a seal with the brass surface.

Regards,
dsc.

Yes, I have a fitting and a thermocouple to fit the La Cimbali and yes, I have NO PROBLEM shipping to your beautiful city. Tom - that screw fortunately has a machined counterbore so no problem with sealing.

Keep in mind that I have never operated a La Cimbali but I do believe the temperature readings at the port will provide useful information. Certainly email me at erics@erols.com for more info.

With Eric's help I have installed this type of device in both of my Cimbalis.

I must disagree, however, with the length of the probe. I had considerable experience using probes located in this exact place, using a dual channel digital thermometer and datalogger, and compared in real time to a Scace device, from time to time.

My opinion, for what it is worth, is that the probe is too long if your goal is to monitor a temperature that will mean something in the temperature management of the machine. The design of the Cimbali is such that there is tremendous influence of the group head temperature on the shot temperature, and the group head temperature is very much influenced by the ambient temperature in the room in which the machine is used. This is especially important if the ambient temperature in the room is variable.

It is true that with your suggested probe location, the same as Eric's, that you will monitor more precisely the temperature of the flowing water as it flows out of the boiler. The problem is that by the time the water starts to exit from the group head screen, it can be different by SEVERAL degrees in the worst case scenario, depending upon ambient room temperature.

The probe placement that you have suggested is similar to what I have with my probes as I received them from Eric. What you will get in this placement will correlate very closely with the boiler temperature, which is related only minimally to the grouphead and to the shot temperature and will not vary with ambient room temperature. So, if you never have a change in your ambient temperature it will work ok. But, if your ambient room temperature varies your group head temperature will vary, and so will your shot temperature. I believe that the extensive experience with Eric's TC device in E61 machines cannot be directly extrapolated to the Cimbali grouphead, whose thermal characteristics are quite different.

What I would do if I was to do it over is to use a probe that is much shorter, perhaps centered right over the group screen screw. In this location I think that the temperature that you get will be much more representative of the group head temperature itself, which will allow you actually use the observed temperature in your temperature management plan.

ken

Hello:

First, thanks a lot to all of you for the input.
Much obliged. =-)

ragwo wrote: Maybe it's possible to use the same custom fitting ...

Not the same one, it's probably too long.
I am now in the process of boring through and modifying the head of a M6 SS bolt to solder a 1/8" brass tube which will in turn harbour a small NPT probe connected to a readout, all from a digital thermometer I took apart. Ken's sound observations tell me that the length (ie: exact position of the probe) has to be though over thoroughly. The hexagonal head mod is just to help it seat properly.

dsc wrote: ... getting a leak proof tight connection ...
That element is round on the outside, so you would have to somehow make it flat ...

The risk of a leak can be adverted with some teflon tape or the right sealing goop (blue, not red). I have already tried it out with the bolt in place and it does not leak with a stabilised machine and brewing.
With respect to the brew-head being round ...

erics wrote: ... a thermocouple to fit the La Cimbali and yes, I have NO PROBLEM shipping ...

Thanks a lot for your offer (and the compliment for BA), but these days the customs charges would make it a rather expensive proposition.

erics wrote: ... that screw fortunately has a machined counterbore so no problem with sealing.

Quite so. Which is why I am having about 0.75 mm of the bottom part of the bolt's head turned so it will seat flat inside the counterbore you mention.

Ken Fox wrote: ... disagree, however, with the length of the probe.
... I had considerable experience using probes located in this exact place ...
... the probe is too long if your goal is to monitor a temperature that will mean something ...

If anyone out there knows about how the Cimbali Junior behaves it's you, so I cannot but to agree. =-)
I had doubts about where the probe should go, hence the post.

Ken Fox wrote: ... design of the Cimbali is such that there is tremendous influence of the group head temperature on the shot temperature, and the group head temperature is very much influenced by the ambient temperature ...

I have recently discovered this to be exactly as you say.

At this moment, I have all the panels (back, side and top) taken off for the purpose of studying how to add adequate insulation in a painless and repeatable manner. By 'painless and repeatable' I mean easy to put on (without having to take the unit apart), to take off if needed and then put back on again, with no destruction of the insulation in the process.

While attempting to ID the places where the Junior loses the most heat while idle / brewing, I discovered that the brew-head is a very important part of this process, probably more than the boiler itself. A probe lodged between the frame and the brew-head (where it is bolted to the boiler) will read a whole 7.5° C more if I cover the brew-head with some ceramic wool, with the obvious influence this has on shot temperature and boiler cycling.

Ken Fox wrote: ... especially important if the ambient temperature in the room is variable.

So I have seen.

I hope to be able to control this somewhat by placing thermal insulation under the shield that covers the top and the back of the boiler, on the inside of left hand panel but only where it covers the end of the boiler and also under the warming tray, albeit only in the area where it covers the boiler and brew-head so as not to cause damage to the three-way valve's coil. I would want that this thermal insulation be a permanent part of these panels so that it comes off with then.

Ken Fox wrote: ... will monitor more precisely the temperature of the flowing water ...
... problem is that by the time the water starts to exit from the group head screen ...
... experience with Eric's TC device in E61 machines cannot be directly extrapolated ...
... Cimbali grouphead, whose thermal characteristics are quite different.

Yes, I think you are quite right.
I have never seen a E61 but the photos and drawings on the web tell me that it is a much more complex design (chambers, siphons, etc.), a different animal altogether.

Ken Fox wrote: ... use a probe that is much shorter, perhaps centered right over the group screen screw.
... the temperature that you get will be much more representative of the group head temperature ...

I agree.
When I first experienced the difficulties this type of machine presents the new user, the first place where I thought I could put a probe was in the small protuberance at the top of the brew-head (problem: hole needed) but then I discovered the cross section on the web, different from the one in the manual that came with my Junior and the threaded hole at the front.

After reading your posts, I am also studying the possibility of adding a PID/Pt100 combo I have to the boiler while keeping the Sirai as a back-up at 1.5 bar. I have now set up a digital timer to switch on the Junior at 05:30 so I can play with it in the morning before I go to work, but I would really like to sleep till 07:00.

My apartment is rather small and the Sirai's 'clack/clack' drives me nuts. =-/

I will post photos as I advance with this project, slowly but steadily.
Once again, thank you all for your input.

Cheers,

CIV

Hello:

Update ...

I have finally finished the probe port.
It was made with a drilled out M6 x 1.0 SS bolt and a piece of 1/8" brass tube to hold the probe.



The base of the head was modified so it will seat properly in the brew-head recess.
It can be screwed in place without using any teflon or sealing paste, resisting the pressured resulting from a back-flush at idle temps without any signs of leaking.

Ken Fox wrote: ... probe that is much shorter, perhaps centered right over the group screen screw. In this location I think that the temperature that you get will be much more representative of the group head temperature ...

This is a photo of the short version that centers over the group screen screw.

Ken Fox wrote: ... placement that you have suggested is similar to what I have with my probes as I received them from Eric. What you will get in this placement will correlate very closely with the boiler temperature ...

I have also made another longer one that goes back to that spot to see how it goes.

Cheers,

CIV

Nice job on the machining. I would still opt for a copper sealing washer (or teflon washer) where the screw meets the grouphead even though it is leak-free today.

Locating the probe tip at the intersection of the drilled passages was ORIGINALLY intended to measure the brew water temperature at that point. However, as the years went by and more knowledge was gained, that particular location became important because it happened to be at a point which I termed the thermogravimetric center of the grouphead. So, even when water is NOT flowing, you are measuring temperature at a point that is very representative of the entire grouphead mass. Measuring the temperature at a location closer to the point of dispersion as Ken suggested may prove better. The idea should be to produce shots with no discernible difference in taste (due to temperature alone) and any probe location that enables that is good.

I am genuinely interested to see how useful the different measurement points end up being as regards shot temperature management, which is the only thing that really matters and the only potential real benefit of modifying the machine this way. I can see a real potential benefit to the shorter probe, but not having tested it in actual use this remains merely my unproven, hopefully educated, guess.

Please keep us informed! Good work!

ken

Hello:

erics wrote: Nice job on the machining.

Thanks ... But like in the case of my Pavoni Shirley's new tamper, it was my friend Michele D'Appolito in charge of the lathe. I only had the idea.

See it here:
My Pavoni Shirley's new tamper

erics wrote: ... a copper sealing washer (or teflon washer) where the screw meets the grouphead ...

I keep an eye on that at all times. The original screw in the brew-head has a ~12 mm. thread and this adaptor has more than twice that length. I doubt it will ever leak, but I don't discard the possibility.

erics wrote: ... the probe tip at the intersection of the drilled passages was ORIGINALLY intended to measure ...

Indeed ...
That's exactly where the brew water coming from the HX, not being able to follow the alternate route, goes towards the shower screen.

erics wrote: ... the thermogravimetric center of the grouphead. So, even when water is NOT flowing, you are measuring temperature at a point that is very representative of the entire grouphead mass.

Good to know.
It's evident that you've done a great deal of R&D, sharing it with us all.
Thanks a lot for that.

erics wrote: ... at a location closer to the point of dispersion as Ken suggested may prove better.
... to produce shots with no discernible difference in taste (due to temperature alone) and any probe location that enables that is good.

The jury is still out (and will probably be for a while) on that one.

I'm still trying to establish the relation between boiler temp and shower screen output temp (= taste).
At the moment what I 'can' say is that a thermally stable Cimbali's brew-head needs to be flushed to be heated in contrast to the E61 which (from what I have read) has to be flushed to cool it.

It has also become evident that, like Ken Fox pointed out at some time, environmental variables affect how this happens quite a bit.

Ken Fox wrote: ... interested to see how useful the different measurement points end up being as regards shot temperature management, which is the only thing that really matters ...

Me too. And I fully agree: it's the only thing that really matters.

I am now in the process of setting up my PID/Pt100 rig to control the boiler. I will keep the Sirai working at a higher temperature (ie: pressure) to act as a back up. I'd be very obliged if you'd let me know which of the heater coil wires you intercepted to connect the SSR ie: the one before the coil (coming from the Sirai) or the one after the coil (to the On/Off rotary switch in the box under the drip tray).

In a few days I will also be changing that rotary switch for a three position model: 1/0/2 instead of 0/1.
Position 0 will remain at centre as 'Off', Position 1 (left) will power everything 'but' the heating element and Position 2 (right) will power everything, like Position 1 with the old switch.

I was really not very comfortable doing maintenance (eg: boiler cleaning, emptying and re-filling) knowing the heater coil was on.

Ken Fox wrote: Please keep us informed! Good work!
ken

Will do.
And thanks for the compliments =-), but it's small stuff compared to what I have seen here at HB.
I think I still have a long way to go.

Thanks a lot for the imput.

Cheers,

CIV