Posted Sun Jun 10, 2012, 8:05am Subject: Re: Gaggia OWC mods
Also ... here is a YouTube video where I show the variable pressure mod on the OWC so I can pressure profile and pre-infuse. And I also demonstrate that with the larger boiler of the OWC - and a Thermofilter to monitor temps during the shot - I am able to to pull back to back shots while keeping the brew temp steady. I'm just hitting the steam switch at the end of the shot for a set count (about 10-15 seconds depending on the target brew temp I'm after) then waiting another short count before starting the shot. I could pull back to back shots until the water tank is empty using this routine (the mods I've done to the OWC help it hold the temp)
Hey Andy what did you use for your.shower screen another beer can cutout? I want to do ur mods I don't think my brass plug works very well bcuz the threads don't really match. I might go to ur solution for the opv. I really need to measure my psi too
I went to the hardware store and bought a sheet of brass ... if I were doing it again I might buy stainless or maybe copper - they had this in several different metals and different thicknesses.
I've tried it with many different arrangements of holes and sizes of holes. It seems to work the best if you keep the size of the holes pretty small and I found this pattern has worked really well. (six holes around an outer circle and six more holes around a mid circle but alternating (see the photo in earlier post).
The beer can works OK too ... especially when I was trying to keep the thickness down ... but in the end, I noticed that this OWC actually has more shower screen clearance than my other, newer Gaggia machines. So I decided to not worry about trying to keep it super thin. The brass sheet is thicker than beer can material but still fairly thin - and I have some RTV material making a gasket/spacer between the brass disc and the shower screen. That allows it to make a tight seal at the edges. The shower screen hangs about 1mm lower than it used to - but I find this is just about perfect for the way I dose and seems to match the same dose level before hitting shower screen as my newer Classic.
One workaround you may want to do other than changing the OPV and the intake water location ... I have started adding a rotary lamp dimmer to the pump. The intent was so that I could pressure profile or at least do a gentle ramp up for preinfusion. But I have noticed that when I use this, I get the best shots when the pump is running at about half power and it still ramps up to a full 9.5 bars but it doesn't drain any water from the OPV since the pump isn't pushing out such a large volume as it does at full power. You may find that there is no need to reroute your incoming water and OPV if you go this route since the OPV won't be bleeding off anything anyway.
There are a couple of other recent mods on this machine that aren't discussed in this thread. I don't know how many people are interested in this old machine ...
I have modified the stand pipe inside the boiler so it is now like the Classic and other modern machines. The way it came, stock, it was letting water from the bottom of the boiler go to the brew head rather than only water from the top of the standpipe where it is hotter. After making that mod, the brew temps were pretty hot so I switched to a cooler T-Stat (the OWC uses a 112C T-stat stock - at least my two OWC machines both do) and I've lowered it to a 107C .. still a smidge too hot, but 100C was too cool and I couldn't find anything between (PID one of these days).
wow a dimmer switch I'm gonna change try that and the dispersion screen when i get a chance. I recently took my keurig mini apart and havent gotten it back together yet so i might want to finish at least one of my projects....but the OWC is always a work in progress. The dispersion screen has always been the weak spot on this machine I thought. I'm trying to find a way to mod the thermostat on the keurig so brews hotter lol. HERE is the link over to single coffee forums if you want to check it out. Maybe you could throw some input. Seems the thermostat is just a conductive one that is fitted to the outside of the tank.
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