La Pavoni Ideale 1929 - Page 2

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Paul_Pratt (original poster)
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#11: Post by Paul_Pratt (original poster) »

I am still working on the boiler when I have time. There are 10 rivet shaped bolts that hold the end plate onto the boiler. You can see some of them here:



So I have been busy making them in my lunchtimes. It would have been easy to use modern hex head bolts but it would be a crime. I will give the bolts an oil black finish.



The base of the machine is cast iron and cleaned up nicely with just soap and water.



After a quick wire brush I gave it a quick spray of some rust inhibitor. Again some paint would be the easiest way but just not appropriate. This rust inhibitor is basically just oil, so quite a conservative method or protection. It can be wiped off with acetone.

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cedar
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#12: Post by cedar »

Absolutely love the hammered copper...

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Paul_Pratt (original poster)
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#13: Post by Paul_Pratt (original poster) »

I had finally finished disassembly of the boiler end plate and the heating elements. This was the last dirty job left and it was quite tricky. The heating elements are early "mica strip heating elements" and can be seen at the top left in the plastic bag. Presumably the paper inside contains asbestos so it went into the bag. So the element slides into the tubes (they look like heat exchangers and thermowell is probably the best description for them) and then there are 3 cast iron fingers that go inside the element. By inserting the tapered bolt and tightening it, it forces the 3 fingers apart and pushes the element tight against the inside of the tube.



My aim is to have 2 new heaters made and reuse this old system. The steel boiler end plate is toast and I have already purchased an 8mm $300 thick slab of brass to make the new plate from. I will hold off cutting the plate until I know which heaters I will use.

One of the thermowell tubes was completely stuck inside the end plate. The tubes are copper and brass but the plate is steel. What had happened is the end plate had rusted and pinched the thermowell around the entire circumference. In the end I put a few dodgy weld beads around it and it was enough to expand the steel, break the rust and allow me to remove the thermowell. I can remove the weld later and keep the original plate for safekeeping.


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Paul_Pratt (original poster)
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#14: Post by Paul_Pratt (original poster) »

I am still waiting for my heating elements to arrive. In the meantime I did a bit of work on the valves and sight glass. The steam and water valves are very similar to later faema and gaggia valves. I rebuilt the shaft and the seat assembly, all I did to the main body was a quick clean and to remove the old sealing cord. There is one interesting difference I can see and that is regarding the sealing packing for the shaft - you can see the packing compression ferrule in the middle at the bottom. The gap between the shaft and the body is 1-2mm max, it is very tight in there and thin packing string is the only thing you can use. I guess you could use a very thin o-ring but it would have to be extremely thin.



The most amazing part of the whole machine is the boiler safety valve. It is the very top of the machine, a large and heavy cast brass piece with leaf (acanthus?) decoration. What is interesting is that this valve has a spring just like a modern safety valve. So inbetween this machine and the 1970's they used a fixed release pressure lead weight.



You can adjust the release pressure by adjusting the spring tension, by threading the top nut in or out.




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Paul_Pratt (original poster)
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#15: Post by Paul_Pratt (original poster) »

I had a few free hours this afternoon to draw up the boiler lid. The strip heaters arrived yesterday but sadly they will not work, I will definitely have another go in the future but for now I need to go ahead and get this done. So some off the shelf Gaggia elements I have in stock will do for now.

Sorry for the photo of the screen :D The old pc I use for the CNC machine is not connected to anything other than the CNC. That was about 45 mins of work to measure the boiler and the old boiler lid and get it all into the program. Then I had to work out the placement of the new style elements and then measure those too.



The file for the gaskets is more or less the same. I cut the gasket first to make sure all the hole placements were good. I am using 2mm Klingersil sheets.



I also designed and cut the top boiler gasket. Fits like a glove. I will tidy up the fluffy edges tomorrow.



The lower gasket



For the main plate I mainly use the CNC machine to mark and pilot drill the holes and cut the main OD to full depth. There are 10 x 12.5mm holes in the flange, I prefer to drill those to size at the manual mill rather than use the CNC for everything as it is a bit too much for my little machine to handle and it takes ages. I will finish the machining tomorrow but the basic layout was done and the elements fit perfectly. That took a bit of brain power to measure the correct layout of the element.



Backside of the elements. The 3 holes for each element were nor drilled all the way through, I think I drilled to 7.5mm (plate is 8.0mm) in the hope I can drill and tap tomorrow for the studs.


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Paul_Pratt (original poster)
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#16: Post by Paul_Pratt (original poster) »

Almost finished the boiler plate today. It is looking good even if I do say so myself :D



I decided the 8mm thick plate did not enough for the M8 studs if I did not thread all the way through. So I drilled and threaded all the way through then counterbored a small recess in the top - I added that just so when I come to solder some covers on they can sit in the correct place and will not wander around. I can add those after the holidays.


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Paul_Pratt (original poster)
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#17: Post by Paul_Pratt (original poster) »

I added some nubs to the back of the boiler plate today, just soft soldered onto the back. These are not structural, just preventing the water leaking through the element stud holes.



I have taken apart the actual 3 way brew valve on the group. Here is a view down the group. Hole 1 is the path down to the coffee. A valve diverts the water to/from the coffee and has 3 positions. At 2 this is what we would know as the exhaust position, like the down lever on an E61 group. Position 3 is for steam, position 4 allows hot water from the boiler down to the coffee.



The diverting valve is quite familiar to me, I have seen it used in many machines and they can be major pain to deal with. The 2 holes are joined together inside the valve and you turn it to the 3 positions as above. The seal on the end is some sort of plastic, could be bakelite.



These sort of valves rely on the material surfaces being perfect to create a seal. Any kind of corrosion or scratch will result in a leak. Anyway I made some new seals and resurfaced the brass valves. One was broken anyway. The small hole is for a pin, this stops the seal from moving around. Both were rusted in place and I had to drill them out.



Anyway they are done, I made the new seal out of POM, we shall see if they work in due course.


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Paul_Pratt (original poster)
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#18: Post by Paul_Pratt (original poster) »

A little progress. The boiler is now back together and I have heat cycled it a few times and then retightened the end plate bolts the next day - once the machine is upright there is no way you can access the bolts so I did that first.

All the electrical had to be done now as well as there is no access to it once the machine is the right way up. I tried to be clever and have a Sirai switch accessible from the small notch in the base...then after I installed the drain pipes that plan went out the window. I had even made the copper pipes and everything :oops:



So it now looks like this, again a little compromise with the modern Sirai switch and the elements as it is impossible to be tweaking things once this machine is upright.



I am very pleased with how my custom rivet style bolts worked out, just like the originals.



And that was it for today. I stamped the boiler plate that I made with the date. I wonder who will be the next person to find that??


mborkow
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#19: Post by mborkow »

I love waking up and seeing these photos from your day's progress (at which I vicariously marvel knowing I could never accomplish it myself).

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Paul_Pratt (original poster)
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#20: Post by Paul_Pratt (original poster) »

My valve packing came in. I ordered 2 types one with PTFE and one with graphite. I went with the PTFE first.



Valve packing seems to come in imperial sizes so I measured the gap and as luck would have it it matched a standard 5/16" size. It took 3 rings of cord all with the joins at different places. The green you can see is from the compression gland verdigris, I removed it for the photo.



And here it is with the compression gland in place.



I am confident that they will seal nicely and the brew lever and stem all move smoothly. The portafilter gasket has been worrying me as it is much larger than a standard gasket, around 96mm OD. The original gasket can be seen here :shock:



I thought I would see if the packing will work, and again the 5/16" is a perfect fit. I would rather keep the style the same and not have some rubber or silicone seal. I managed to do one group today. They really look like the originals but without the toxic minerals!