I returned from the holidays to find an envelope from Francesco, much faster than he thought the post would take. Merry Christmas! The piston o-ring and the portafilter gasket both fit well, and were well worth the reasonable price.
I had a neighbor help me reload the spring (thanks for the offer drgary; we'll have to meet up sometime) and the Arin is back together and ready for the morning. Now back to optimizing my methods...
Maybe I'm doing something wrong... piston o-ring has already busted, after just a few days use.
I looked around here a bit and there was some talk of putting too much pressure on the handle. The Arin is a spring lever but I do assist it when I overpack it. I have pulled up pretty hard at times... does this mean I'm going to have to relax and let the spring do the work? The fella from Orphan Espresso posted that it takes a scrape or a pinch to bust an o-ring so I'm not sure about this.
Not sure if the 0-ring should be lubricated but I do have some food-grade lanolin from New Zeland that should work. I just wonder how often to lube because it can't last long with the hot water and such.
Speaking of hot water, might I be letting the water get too hot for the o-ring? I have been letting the water boil (about 10min with my Arin from cold) and then letting it cool for 30sec before raising the piston. Could the heat be degrading the o-ring after only a few days? Is there one material better than another? (EPDM is mentioned alot)
As I mentioned above I also began raising the piston a few extra times to get more water in the cylinder. I suppose this could allow the pressurized portion of the routine to start when the piston is higher in the stroke, and maybe when the o-ring has not yet seated in the cylinder. This is sounding like a bingo at the moment.
In order for water to enter the cylinder the piston has to be high enough to catch the o-ring on the top edge of the cylinder. Arin is probably designed to let the piston o-ring fully enter the cylinder before it pressurizes, saving it from being exposed to the upper edge of the cylinder when expanding.
Did the O ring go on easily, or did it have to be stretched pretty tight? I'm just fishing for some clue to what might have gone wrong, which seems to me would most likely be either damage during installation (if it's a super hard fit), or, conversely, it doesn't fit so tight and gets caught out of place during use.
the o-ring went on easily. Its right at the bottom of the piston, and a simple o-ring.
My guess is the method change I outlined above, pumping the piston during infusion to let more water into the cylinder likely put the piston higher in its stroke and may have left the o-ring out of the cylinder when compression started, which could have cause it to be pinched... it did fit snugly when installed, but I assume the compression would cause it to deform.
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