Riviera Two Group piston seal problem - Page 2

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
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cuppajoe (original poster)

#11: Post by cuppajoe (original poster) »

What has been puzzling me is it looks like the function of the center seal is to prevent water from moving out through the group, so why would they engineer it so the water enters below the sealing surface of that seal? If the piston was adjusted so the center seal is below the water port, the bottom of the piston is beyond the shower screen.
David - LMWDP 448

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RobAnybody

#12: Post by RobAnybody » replying to cuppajoe »

my best guess is that it allows for compartment of water around the piston which would help it to warm up with the rest of the group and not act as a heatsink during a shot.
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RobAnybody

#13: Post by RobAnybody »

those vertical gouges are most likely the cause of the leak from the grouphead. If they aren't to deep you should be able to polish them out without widening the bore to much.

On a side note, If you happen to have more pictures of the machine and its parts I would bet Francesco Ceccarelli would love to have them to update his website. He only has a very small pixellated image of a two group Riviera in there now.
Cheers,
Rob
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cuppajoe (original poster)

#14: Post by cuppajoe (original poster) »

Thanks, you may be right about the engineering and the seal is supposed to be robust enough to withstand 1 bar pressure working against the seal design.

The gouges do seem a likely culprit for the leaks. They are deep enough that honing the cylinders may work, but would have to be very careful with that. There is also the possibility that the low point in the ridging is compromising the seal. New replacement groups are available, but would run between $300 and $350 for the pair with shipping. It would be the client's call.

I have been in conversation with Francesco, he's also stumped. He said he doesn't have much experience with the Riviera beyond his own. I'll ask him if he would like pics of the machine.
David - LMWDP 448

My coffee wasn't strong enough to defend itself - Tom Waits

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drgary
Team HB

#15: Post by drgary »

I might try one more thing, shimming the piston gaskets by wrapping some PTFE tape underneath them. If they flare out a bit more they may provide a waterproof seal.
Gary
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cuppajoe (original poster)

#16: Post by cuppajoe (original poster) »

I have tried shimming, but it didn't stop the leaking. I've got a cylinder hone on the way for a last ditch attempt. The customer is balking at the extra $300+ for new groups.
David - LMWDP 448

My coffee wasn't strong enough to defend itself - Tom Waits

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drgary
Team HB

#17: Post by drgary »

Is it possible to braze material in the pits before honing? And if there's still a gap, I wonder about chroming the inside of the cylinder? Otherwise it's an awesome display piece.
Gary
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RobAnybody

#18: Post by RobAnybody »

cuppajoe wrote:I've got a cylinder hone on the way for a last ditch attempt.
If you switch to the new style seals after honing it should buy you a few extra microns to get rid of the gouges.
cuppajoe wrote:The customer is balking at the extra $300+ for new groups.
I guess widening the bore even more and brazing in a new pipe with the right inner diameter would cost more in terms of work hours than getting a new grouphead. :wink:
cheers,
Rob
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cuppajoe (original poster)

#19: Post by cuppajoe (original poster) »

I have already installed the new style seals, so hoping I can take out just enough material so they still seal.

I had thought of sleeving the cylinders, but it would probably run more than replacing the groups. The major divots are above the seals, so have no impact. The longitudinal gouges seem to be the main problem.

Thanks for the replies.
David - LMWDP 448

My coffee wasn't strong enough to defend itself - Tom Waits

RobAnybody

#20: Post by RobAnybody »

A thought occurred to me last night while walking the dogs
(as they more often do). Would it be possible to (over)fill the gouges with silver-solder by brazing using a clay mould to fill the piston bore? With the right solder the temperature should stay below the limits of the chrome coating.
In the ideal case it would only need some smoothing afterwards. (Honestly I've never brazed myself, but based on the theory and physics behind it it might just be possible)
cheers,
Rob
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