How to Change Lusso/Export Seals: The Ponte Vecchio Way!

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sorrentinacoffee
Posts: 747
Joined: 16 years ago

#1: Post by sorrentinacoffee »

I have often wondered what Ponte Vecchio had in mind when they designed their group head. How did they intend users to change the seals? I had an answer of sorts early this year when they asked me how I changed mine! It seems they were having difficulty describing the process to a customer in the Netherlands...

I used the G clamp method: dirty but effective. Not anymore...

We have seen many different methods discussed on this forum. Some elegant solutions (with contested physics), some rough and ready solutions, and some downright laborious ones....

Well I finally found out just how PV do it themselves at the factory! They sent me the Secret Tool!


I can finally say in all honesty that changing the seals was FUN! seriously- I know I have a warped idea about fun but... if you had messed around with the clamp you will now what I am talking about...

It even has an extra alloy bit just for neatly stamping the filter plate back into place! A turned alloy sleeve holds the seals in place. I changed over two groups in around 40 minutes. The second group took 12 minutes at the most: no muss, no fuss. Under fire I could do it in 8 minutes I should say...

with practice, who can say? :twisted:

It is, I think we will all have to agree, the very best way to do this job! I think the truly dedicated PV lovers are going to want one of these-

OE- I see a tiny market...

here are some pics of the tool- it is a modified portafilter and would be relatively easy for a machinist to replicate:







You can read more about using the tool here:

http://coffeesnobs.com.au/YaBB.pl?num=1307713119

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peacecup
Posts: 3649
Joined: 19 years ago

#2: Post by peacecup »

Damn. So easy... so obvious. Well, now we know why they never fussed about changing the group design.

I am REALLY missing my second Export - the Sama that came second-hand with a leaky sight-glass and bolts rusted to the boiler so it is impossible to change the seals. It's sitting in a box waiting for me to figure out how to get the bolts out, while I drink pump espresso.

PC
LMWDP #049
Hand-ground, hand-pulled: "hands down.."

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RAS
Posts: 536
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#3: Post by RAS »

Hey, what if we could get OE to acquire this kit, and make it available for rental (Doug?!!)
Bob

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sorrentinacoffee (original poster)
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#4: Post by sorrentinacoffee (original poster) »

Sounds like a good solution for North American Lusso owners. Wouldn't be too hard to make one from a standard portafilter.

ziobeege_72
Posts: 308
Joined: 15 years ago

#5: Post by ziobeege_72 »

An absolute revelation Jack. Given the hassles I've had in the past in changing seals, I would pay a pretty penny for it. Life is too short for c clamps, especially in the hands of the mechanically-challenged.

Great write up on the snobs forum too.

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peacecup
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#6: Post by peacecup »

Should be easy enough to drill a hole through the center of a stock PF, then tap the hole with screw threads. The pf would also function fine for espresso afterwards, so it would be no great loss.

One of these days I'll need to make one of these, but I've found the seals to be pretty long-lasting in general.

PC
LMWDP #049
Hand-ground, hand-pulled: "hands down.."

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GB
Posts: 207
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#7: Post by GB »

Jack,

Thanks for sharing this with us PVE & PVL owners. And an additional thanks for your excellent write up in Coffee Geek.

It is such elegant and simple solution. I wonder if the original designer of these machines is responsible?

Jack, what are the dimensions of the thread? It looks like it might be an M8? Also what is its length? Also any other details and dimensions would be appreciated.

The fixture is simple and easily fabricated by a competent machine shop. Probably the largest cost will be in the porta filter. I will definitely make one before my next seal replacement. And will be quite willing to loan it out.

Cheers
Geoffrey
Simply coffee

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sorrentinacoffee (original poster)
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#8: Post by sorrentinacoffee (original poster) »

No worries Geffrey,

the tool is direct from the Ponte Vecchio factory. I don't know what the thread on the brass rod is- I don't have any tools to measure it? How would I go about that? I guess it wouldn't matter what thread you used too much?

There is a nut welded into the base of the PF as well- so I am guessing it is a standard thread.

One of the tricks would be to get the central brass pin/bolt/rod perfectly aligned. On the tool the top of the rod has been ground perfectly flat and horizontal so it doesn't scratch the brass on the base of the piston too much.

I am happy to post more detailed images. They have ground a little metal off the two 'teeth' on the PF as well and ground off both the little 'nipples' that are on the bottom. Other than that it is just a standard PF. The little alloy sleeve for flattening the seals into position is rounded at one end so it slides over the seals easily and is shaped at the other so it mates perfectly with the piston cylinder.

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michaelbenis
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#9: Post by michaelbenis »

Great solution, including the seal sleeve. I imagine the nut is welded in there to avoid the long-term problems of a steel bolt in threaded brass.

Incidentally, Jack, having read the great Coffeesnobs guide, you can get small circlip pliers for little cost in many hardware/tool shops and also of course from Orphan Espresso.

They are very handy for all sorts of lever machines.

Cheers

Mike
LMWDP No. 237

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GB
Posts: 207
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#10: Post by GB »

Jack,

Thanks for the info. I assumed the thread would be metric coming from Italy and my guess on the size was done by trying to visually scale it to the other parts. The correct way to determine the thread size is to measure its diameter with a micrometer and measure its pitch with a thread pitch gauge. Then compare that data in thread tables. Barring that maybe you could compare it to some know sized bolts you may have. But the thread size is not that critical so not to worry.

The fact that they brazed a nut into the porta filter tells me that there may not be enough material in the porta filter to spread the load of compressed the spring. A very important piece of data. Mating steel and brass parts is probably not the issue. It is a well used technique in machine design to reduce wear. Consequent it is common to see a steel shaft in a brass bearing. So I suspect that loading is the main issue. Jack you mentioned that the "threaded rod is brass" is that correct? Just checking because it looks like steel in the photos. Also what material is the brazed nut?

Yes, alignment of the thread to the centerline of the piston is critical considering the forces involved. Even a slight misalignment could translate into the piston being forced against the sides of the cylinder potentially grooving the cylinder walls. Also it will cause bending loads on the screw and nut. So precision is critical. As for the top of the screw being flat, I agree.

You also mentioned the "little alloy sleeve" that functions as a "Seal Compression Sleeve" having features on the other end? If it does would you mind photographing that.

And lastly I am a little unclear on how the recessed aluminum plate functions. Would you mind providing more detail.

Thanks again
Geoffrey
Simply coffee

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