And the spent puck using my dispersion disc mod. This won't look that smooth to anyone who hasn't used an OWC - but if you've ever seen the puck from a stock OWC, there would have been a deep pit the size of your finger in every puck without the disc I added.
Also - I stuck a digital thermometer on the boiler and the temp didn't drop hardly at all during the shot after switching to the new inlet location. Prior to this the temp would have plummeted during the shot and the heater would have cycled on again about 5 seconds into the shot. With the new inlet (so that the OPV no longer bleeds hot water from the boiler) the heater did not need to cycle on at all during the shot. The larger volume boiler really holds the temp quite well now.
Those shots look great I like the end result in the cup thats one fine shot if I do say so all from this 30 yr old machine thats awesome! I'm in the process of trying to get a 1/4 in brass plug I got from home depot to use to plug up the OPV hole. I removed the OPV and instead used the OPV from the grangaggia that sits on the pump. I'm waiting for my machine to cool because I dont have the plug quite seated yet and there is some water trickling out. Im wondering if its because its brass and not copper like the OPV so its not expanding as much. I was trying to figure your dispersion screen out there with the beer can thats what I was gonna use too . Have you seen where a person has tried to wrap their boiler with copper tubing to make a preheater? I'm wondering if that would be effective or not. I still have the orig ULKA pump! I think this machine can be tweaked to produce some great results!
If you are using another OPV valve on your pump, there is no reason to plug up the original OPV. Simply crank the adjustment down really tight on the original OPV and then it won't bleed anything off. But if you've already got a plug in there - you probably want to use some teflon tape. The threads may not match either.
The beer can aluminum disc, I just used the point of a sharp knife to make several triangular shaped holes (small ones) by stabbing the disc lightly while it was on a wooden cutting board. Just don't make any hole right underneath where the water comes spurting out of the group. It's sort of trial and error. I put half the holes on one side of the disk and then the other half from the other side. That was so there would be raised sections on both sides to prevent the pressure from pushing the disk against the screen when pulling the shot and from pressing the disc against the group when backflushing.
Wrapping a boiler with copper was a trick for the smaller boilers on the new Gaggias - but this old boiler is about twice as big and doesn't need a preheater IMO - I was amazed at how well it holds the temp once you prevent the silly OPV from flushing all the hot water back into the reservoir.
I also have a Classic but with these mods I'm liking the OWC better.
Posted Sat Jan 1, 2011, 8:08pm Subject: Re: Gaggia OWC mods
I tried the dispersion screen works well thanks! I finally got the plug im after sitting on my machine and torquing the plug down. Im not cool with hot ptfe in my espresso so no tape on the threads! My thermometer reads 195 at top of boiler it kicks on at 189 if I pull a shot its sour so im guessing it was an accurate read. I throw rhe steam switch on so its up to 220 and pull and no more sour. My opv valve is hard to adjust I tightened it down with my pliers and it still bled h2o. so I removed it im wondering if I should T the orig opv in or keep use the grangaggias. The gran gaggias is way smaller I wish I knew more bout espresso machine engineering I like the quickmill opv mod but I cld really just use mine. There was an article about opvs where they are specific for diff pumps I know ours is a strong pump so maybe it needs a big opv? Oh yea my shots dont look as awesome as yours they are kinda watery and lighter maybe its my month old black cat I just bougjt from wholefoods
ribozymer Senior Member Joined: 2 Jan 2011 Posts: 15 Location: San Francisco, CA Expertise: Just starting
Grinder: Rocky Rancilio (working on...
Posted Sat Mar 19, 2011, 4:29pm Subject: Re: Gaggia OWC mods
Do you remember what size brass plug you bought, and what size tap you used? Also, do you think there is a need to increase the pressure on the OPV since the pump practically pumping directly into the OPV?
When I went to the hardware store with the water inlet elbow they told me it was an 1/8th. I was pretty sure it was metric but it was all they had. I used the 1/8th tap to bore out the water inlet hole a bit more to fit the 1/8th brass plug I bought. Since the tap was tapered the new inlet I tapped under the OPV fit the old elbow water inlet. I was careful not to make the hole to close to the boiler and there was plenty of room to screw the inlet elbow in. Overall pretty easy procedure. Thanks.
Now for the second issue. I also keep seeing the deep channel in my puck where the grouphead outlet is. I tried the beer can trick but I get water spraying out the side of the water screen. It seems the extra width the beer can adds creates a gap along the edge of the water screen. Any suggestions? I'm at a loss here. thanks
The pressure would not have changed any - though it is still a good idea to adjust the pressure if you have a portafilter gauge - but it should still regulate the pressure exactly the same as it did before. The big difference is that the water it bleeds off now will be cool water entering the boiler instead of water that has already been heated by the boiler.
As far as the beer can disk leaking on the edges ... I don't experience that. But it was a lot of trial and error to get the small holes pierced to a size and location so that the spray seemed even. You can see this just by looking at your dispersion screen while running the pump. The stock setup would have all the water shooting out right under the outlet hole ... but if you get the beercan screen made correctly you will see water drops forming evenly over the entire shower screen.
Posted Sat Jun 9, 2012, 11:16pm Subject: Re: Gaggia OWC mods
I've done the dispersion disk several different ways since I last posted here. I finally have something that seems to work really well ... so I thought I'd post some pics. I used some food safe, hi temp RTV to seal the disk to the group at the outer edges. It's really easy to remove if needed - but I never really need to take it off. The RTV is just a thin ribbon right at the edge of the disk and acts like a gasket - so even if I were to pry the disk off to clean better underneath, I don't need to reapply since it stays on the disk and seals just fine when the shower screen is screwed in place.
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