Gaggia Tell 2 Group and Reserve Rebuild

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.

Koffee_Kosmo

This is the theory At our altitude water becomes steam at 100 degrees Celsius So a boiler must reach that temp to make steam and steam collects in the upper section of the boiler This is then released by the pressure to the steam wand Water cools down as it goes through the pipe work to the group head for brewing duties This temp is hopefully at 89 to 92 deg Celsius when actually brewing coffee KK

DMH

Thanks KK. All true. My thoughts are that a pressurestat controls by boiler pressure and the temperature of saturated steam varies according to this pressure. At 1 bar 100C and approx 107C at 1.3 bar. So after thinking about it a bit more both the liquid and steam should be at the same temperature. So it doesn't really matter if the PID measures liquid or steam temperature. I may just measure both temps and see how it goes.

DMH

More cleaning and the polishing is required but I thought I'd temporarily install the boiler and check the available room for the electrics and controls. I think I am now almost committed to a PID/SSR relay with a sirai as an overpressure shutoff so I drilled an tapped a new 1/4'BSP hole in the boiler end plate and direct mounted the sirai. Whilst its in a good and easily accessible position it may get a bit hot so fit a hex nipple and a socket to give me a bit of air space from the boiler. The old 1/4" opening on the opposite site is now available for a thermocouple so I'll get one made up with a 1/4"BSP compression fitting. There is a ton on room under the boiler and I assume that this is for gas fired models. Also the front plate of the machine has a few openings which I assume are for the inspection of the frame. I don't have the controller or the front plate back yet but I'm thinking that I may be able to discretely mount the PID controller and SSR under the boiler so that the display is visible through the existing opening. I'm also thinking of a power light and an element on light also and I'll either drill a hole through the front plate for these or mount these behind the opening also. The machine didn't come equipped with an ON/OFF switch and I need to find a good position for this. I don't want a simple toggle but would much prefer the old fashioned Bremas rotary cam with a black faceplate. [attachimg=1]

DMH

It turns out that my chromed items are ready three weeks earlier than expected so its time to finish off a few loose ends and start assembling the machine. I'm still not sure on the best way to control the machine. I have read on many times that it is common practice to replace the mercury with with a Sirai pressurestat yet I can't understand why. The mercury switch is simply and consistently switches with a deadband of 0.1 bar which is about half of that of my new sirai. To complicate matters I also have also purchased a temperature controller with a SSR. As a complete novice in the field of coffee machines I am asking and would like opinions on which is the best way to go. Option 1 - Mercury Switch Option 2 - Sirai Pressurestat Option 3 - Temperature controller and SSR All items are in stock and ready to go. Also looking at insulating the boiler. I was thinking of using HT Armaflex and planned on picking up a role from their Melbourne office. It turns out they won't sell to non account customers and were a pain to deal with. If anyone has a source of this material it would be greatly appreciated. If not I'll use ceramic fibre which I have ready access to.

Koffee_Kosmo

Option 3 Temperature controller and SSR, is my preferred choice if it can be easily be incorporated into the rebuild from the start KK

DMH

Been a long time since I last posted. The progress on the Gaggia has stalled. The machine is virtually assembled with a Sirai pressure stat and a new old stock Bremas rotary cam on/off switch. A day or so with the wiring followed by the installation of the piston seals and the machine will be ready to go. The main thing holding me up is the size of the machine and the fact that I have nowhere to put it. Also I don't really like the hotel group and would prefer a proper 2 or 3 group lever machine. Playing around on ebay I just picked a 2 group pump machine of the same vintage. For a couple of hundred dollars it was worth a try. Not sure of the model but it is similar to the Gaggia ELE of which there are a few on the German forums. Unlike the German machines which use a Sirai and the more modern round flanged heating element mine is very similar to the Tell and uses Tell type heating elements and a mercury switch. Unfortunately one of the bulbs was broken. This machine is also equipped with a standard 10amp plug. Thinking of replacing my single 3 group 1750w element with the two 2 group elements for a faster heat up on a 10 amp supply. Another thought is turn the 2 group pump machine into a 2 group lever machine. This would involve another go of sandblasting/painting plus the cut and reweld of the stainless steel 3 group front.

DMH

Turns out one of elements in the 2 group is shot. Easiest thing to do now is finish the 3 group and then restore the 2 group boiler and casing and convert to lever later on. The two group boiler is significantly smaller than the three group and makes a lot more sense in a domestic situation. By the way if anyone needs the Gaggia pump groups yell out as I have no intention of using them. [attachimg=1][attachimg=2][attachimg=3][attachimg=4]

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