Gaggia Tell 2 Group and Reserve Rebuild

Brett_H

Holy cow what a palava! I reckon when these things try us the coffee must be so much sweeter!

DMH

Yes I'm looking forward to getting this machine running. Hoping to be using this monster at the family dinner at Christmas. Looking at previous threads on HB I have seen two or three month delivery of various group components and I certainly can't be bothered waiting this long. Provided that the pistons can be saved I should be OK. I striped the valves and the reserve group over the weekend. No dramas here I just need to source the valve seat gaskets and main body gaskets which don't appear to be available locally. I can probably get these made up. Also the reserve group handle has a broken plastic pin which can readily be replaced with SS.

kofekitt

Pistons are available from a couple of places, but they all originally come from Ascaso in Spain. Quality of them is sketchy at best with usually a few dings in the chrome when you get them 🙁 I sympathize with your efforts getting the original pistons off, i had a hell of a time with mine, got one off, eventually gave up on the other one and ordered 2 new ones. I know a supplier in Germany who usually delivers within a week or 2, if they have stock

DMH

At the fabricators now. Does anyone know the thread size of the mild steel piece into the piston.? It's a weird size.

Koffee_Kosmo

DMH wrote:

At the fabricators now. Does anyone know the thread size of the mild steel piece into the piston.? It's a weird size.

If it's Euro - then it should be metric However in those days it's possible they may have used UNC/UNF threads This is good chart to print out http://97.74.32.155/files/tchart.pdf KK

DMH

Thanks for the chart. Since I was intending to draw up and fabricate new connecting pieces we cleaned up the pistons and tapped new threads to suit the thickness of the material available. These ended up being M18 x 1.5mm. Whilst the castings are off centre the existing and new threads are central to the piston. Amazing what can be done with a lathe and a skilled operator in less than an hour. I was going nowhere fast with a drill and a dremel. [attachimg=2] [attachimg=1]

DMH

It appears that the upper geared shaft is shot. I'm having problems sourcing a replacement and have been advised that this part is no longer available. It looks like I will need to have the worn teeth rewelded, manually filed to shape and then the shaft rehardened. If anyone has a spare that they would be willing to sell I would be most appreciative. [attachimg=1]

Koffee_Kosmo

DMH wrote:

It appears that the upper geared shaft is shot. I'm having problems sourcing a replacement and have been advised that this part is no longer available. It looks like I will need to have the worn teeth rewelded, manually filed to shape and then the shaft rehardened. If anyone has a spare that they would be willing to sell I would be most appreciative.

My engineering hat is on Can you source just the gear ? If so - what I recommend is - on a lathe remove old gear Insert new gear after the appropriate interference ( heat fit ) hole is cut on a lathe Weld top and bottom for final gear placement Lathe again the weld line to a flush finish KK

DMH

Its worth considering however to the bottom of the teeth are almost in line with the actual shaft leaving virtually no thickness for the lower ring of the gears.

DMH

Managed to pick up a brand new pinion shaft from Coffee Mio in Melbourne. Also purchased a couple of new pistons.

Koffee_Kosmo

DMH wrote:

Managed to pick up a brand new pinion shaft from Coffee Mio in Melbourne. Also purchased a couple of new pistons.

That's great news - makes progress a little easier and a headache averted :thumb: KK

DMH

Dropped off all the items shown below to the chrome platers. Funny thing is he had an older Gaggia 4 group lever waiting to be rechromed that he had been told was worth 50K. [attachimg=1] I decided not to do the reserve group at this stage and I will probably just clean it up and install it as an interim fix. Chrome is going to take about 5 or 6 weeks so I have plenty of time to clean up and install the boiler, piping and other bits. [attachimg=2] I have frame and outer panels back from the powder coaters and expect to have the brushed finish stainless panels back in about a week. I also now have virtually all the required parts in stock. With the exception of the V-rings in the group seals, which are being generously supplied by Paul Pratt in Hong Kong, all other parts have been supplied by Coffeeparts in Sydney, Coffee Mio in Melbourne and a few general industrial supply businesses.

Brett_H

Wow... Just wow!

C-man

Super! Is this a full manual lever, or does it have a spring?

DMH

Spring lever. The previous page has photos of the old springs. These shall be replaced with new ones.

Kevohere

Brett H wrote:

Wow... Just wow!

Gotta agree with that Brett :exclaim: Good luck with the rebuild DMH. I shall be watching this "job" in awe as it progresses. Thanks for sharing. :thumb:

DMH

Now that I have a five to six week wait for the chrome I need to decide how exactly I plan to control this brute. The machine originally was direct wired and the elements controlled on/off via a mercury actuated pressure switch. I have purchased a sirai pressurestat to replace the mercury switch but I am tempted to go a bit further. One option is fit a proper ON/OFF switch and also a PID controller with a SSR. If I do this I will retain the sirai for use as a overpressure shutoff prior to the pressure relief valve kicking in. Since the PID is used to control boiler steam temperature which in turns controls the boiler pressure is there any other advantage, apart from cost, in using a temperature element as opposed to a pressure transmitter. I have also seen similar machines where a level probe is fitted directly into the boiler sight glass and may go this way also.

C-man

Kevohere wrote:

Gotta agree with that Brett :exclaim: Good luck with the rebuild DMH. I shall be watching this "job" in awe as it progresses. Thanks for sharing. :thumb:

If you change the springs, will that change the extraction pressure?

DMH

Yes. Most likely. I would assume that the old springs have lost a bit of their kick over the years and the news springs, which are still readily available, would be consistent with the original design.

DMH

On PID systems is it normal to measure the liquid or steam temperature in the boiler and is there a difference? I already have a spare port which can be used to measure liquid temperature but would need probably need to drill and tap a new opening in the end plate to measure steam temperature.

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