Gaggia Tell restoration

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
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Carneiro

#1: Post by Carneiro »

Great restoration from Paul, as long as with Lyndon and Ed's and Oliver's too.

I'm just about to start one half way done. A friend that used to be a hobbyist and now works with commercial machines here brought one 75 Orione from Germany and I got it from him as he has no time to do it (I'll have to restore his Velox as part of payment, but this will be a pleasure). The group is already strip down, but the spring was very rusted and maybe 1.5 coil is stuck inside the piston... Nothing new, but I'm not sure how to remove it. Maybe some magical compound to dissolve the gunk or some physical intervention with a drill...





It has a seal kit with the fiber washers but I'd like to borrow Oliver stack idea... And the new spring I have in hands doesn't seem to be strong as it should be, I'll take measures to try to estimate its power. I don't know where it came from. The piston diameter is 5.4cm, so it seems the area is 23cm², that would require something like 210 kgf so the group can reach 9 bar...

I'm not sure if I should start a new thread for just another Gaggia restore, but I don't want to hijack Paul's great one!

Done new thread, by Dan's suggestion! :mrgreen:

Márcio.

EDIT: I just found out that this model is the Gaggia Tell...


...split from Gaggia Orione restoration by moderator...

User avatar
Carneiro

#2: Post by Carneiro »

I've done some measures on the spring I have. Its 167mm long, 46mm external diameter, 7mm wire diameter, 12.5 coils, 14.85 pitch. The calculator I use says the rate of the spring is around 4 kgf/mm, if this is carbon steel.

What's the size of the spring when installed and how much it's compressed when it seals the chamber? If the chamber is 23cm² it would require 210 kgf and that should be around 53mm total displacement of the spring. Of course it would compress more when the lever is pulled all the way down. The limit of compression for this spring, in theory, is 63-65mm.

Márcio.

User avatar
Carneiro

#3: Post by Carneiro »

Finally I took off the piston shaft etc. Nasty rust, but now I understand the spring sit on the brass piece and the little pin is not tense when pulling the lever, only when pushing the water down - not even that, when the whole thing pushes the water the bottom part that screws into the piston is forced against the shaft, so the pin works only to pull the piston up.

But I've measured the thing and it seems the spring is 114mm installed! :shock: That would be something like from 12 to 9 bar, but maybe I'm not counting other factors and, of course, the spring could be lot less than 4 kgf/mm. But in fact this spring will be almost solid when fully cocked.

Anyway, the group design is fantastic - it would be easy to replace the shaft for a longer one and adjust the top cap to have less power, for instance. I don't know if this variety of configuration was available in those days...

Márcio.

jmc
Supporter ♡

#4: Post by jmc »

Carneiro wrote: But I've measured the thing and it seems the spring is 114mm installed! :shock: That would be something like from 12 to 9 bar, but maybe I'm not counting other factors and, of course, the spring could be lot less than 4 kgf/mm. But in fact this spring will be almost solid when fully cocked.
I have a brand new replacement from Composants in my hand and the length ( uncompressed ) is 165 mm, wire is 7 mm and it has 12 turns. Hope that helps.

John
John

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Carneiro

#5: Post by Carneiro »

Hi, John, same dimensions as mine. I was suprised to know that it's 114mm when installed, and, if this spring is indeed 4 kgf/mm, considering 50mm compression, that would be around 200 kgf! Maybe the spring is not so strong as the software tell me...

Márcio.

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HB
Admin

#6: Post by HB »

UPDATE: Split to new thread per Márcio's request. See Gaggia Orione restoration for Paul's writeup.
Carneiro wrote:I'm not sure if I should start a new thread for just another Gaggia restore, but I don't want to hijack Paul's great one!
It's up to you, but per the Guidelines on mega threads, I recommend starting your own if your reports will be more than a few posts so it's not "buried" in an already long thread.
Dan Kehn

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Carneiro

#7: Post by Carneiro »

The picture is not good as it was from Paul (the previous owner) and the chrome seems nice. But no, it was beaten. I've took all the chrome parts today to the shop, I hope they make it pretty again!

Now I have to remove the boiler plate heat element studs - 2 of them were easy, 4 are stuck... Work on the boiler, work on the stainless steel panels etc. I don't know if I try some Autosol paste or if I look for a professional job (that way is less fun)...

Márcio.

User avatar
Carneiro

#8: Post by Carneiro »

Just some work done on the boiler. Studs (the 4 upper ones are stuck):



Time and bad care:





During a acid bath:



Take a look at the boiler to group flange... It's different from older Orione like Paul's. I don't think the traditional gasket available is appropriate, but I'll get one. A great HB fellow is making a PTFE washer to fit at this outside part, maybe this would seal better with the group. If anyone have any tip, I'm all ears. I've seen Oliver blog pictures and his boiler is similar to mine, but I don't understand how he assembled this.

Just another question... The boiler is gray outside, and inside is nude copper only half, where the water level was with a lot of scaling. The upper half seems to be this metal too, but darker, maybe oxidised. What is this plating? Is this tin? I've read about tin or chemical nickel plating for food machinery parts, and it doesn't seem to be electroplated nickel. Considering the time I left it on a high concentration citric acid bath, I think nickel would be removed, at least some part. As far as I read around, tin plating should be very resistant to acid.

Márcio.

spyderxxx

#9: Post by spyderxxx »

What I did to remove the grey coating was 150 grit sand paper on a pad sander. I was able to get about 95 percent off in reasonably short order. You might want to try some polishing compound on the grey first to see if it gets shiny.

Ed

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Carneiro

#10: Post by Carneiro »

Hi, Ed.

I don't care much about the outside, I was even thinking about a thermal sheet. But inside there, the upper half is coated, and I think it would be almost impossible to remove all of it, at least the part close to the flange with 10 holes.