Custom needle valve for flow control on La Marzocco Linea

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TomC
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Postby TomC » Dec 07, 2016, 5:17 am

I finally finished the installation of my custom needle valve kit from Sean Alcorn. It, paired with the Shureshot, now opens up a lot of capabilities that I didn't have prior, namely flow control throughout the shot. As it came stock, the restrictor certainly looked larger and the whole unit tended to act like a 'water cannon' to coin Nicholas Lundgaard's term for it. I placed a new 0.6mm ruby restrictor into the group neck and it's mated to a needle valve that I can control external of the machine (which is quite nice). Lots of Swagelok fittings and all the tubing is small diameter stainless steel.

Sean really did something quite remarkable, especially since my machine is here in California and he built it on his 3 group in Sydney, Australia. He went with only ruby seals instead of Viton. The pressure gauge now reads an analogue of the pressure at the puck. If I don't have the resistance of a coffee puck, the pressure gauge shows no pressure at all. With either a blind basket to adjust pump pressure or a coffee puck, I can monitor the pressure the coffee is seeing. It'll be interesting to pair this up with a Scace again now that it's installed and see the offset on the gauge.

Here's the first video of it in action. The shot was extremely good, especially for just dialing things in.



I'll keep toying with the various settings, likely increasing the pre-infusion time thru the needle valve longer without lengthening the total shot time. With the Shureshot, I can set each stage at a set time, and choose whether I'm flowing thru the needle valve or bypassing it. I can tail off the end of the shot like a Synesso by either choosing line pressure at the end, or I believe, line pressure thru the needle valve. More playing around to be done on that front.

The faceplate will need to be drilled so I can have the needle valve knob protrude nicely thru the front. It's nice to think I can adjust the restriction on the fly without opening up the machine.

All in all, this cost me about $800 (not including the Shureshot) and I'm glad I was able to get it. This one specifically was a one-off high grade build with all stainless components and better seals. He has others in copper and other more affordable parts he's considering selling. He's not planning on making these fancier ones on a production scale for now. It was a year of back and forth with him around the time I learned about the Shureshot, that I learned that he was also modifying his own 3 group Linea with needle valves that he intended to keep on his bench at work for his own use. I could have had a similar assembly on my machine earlier this spring if I was willing to go with what he already had on hand.

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jgirl125

Postby jgirl125 » Dec 07, 2016, 10:34 am

Very nice. Can you post a few more pictures of the valve assembly on your Linea?

michael

Postby michael » Dec 07, 2016, 12:34 pm

more pictures please

do you know the size of the restrictor that now comes standard on the GS3 MP 8)

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TomC
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Postby TomC » Dec 07, 2016, 3:12 pm

Here's a few shots of the system installed and awaiting installation. The cheesy LED strip light is tacky looking up close, but proved very valuable during the installation, being able to see everything well. I have a permanent kit with two lamps awaiting installation at a later time that will wire directly in to the machines electronics rather than an external power supply.


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And for comparison, the stock setup.

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Before installation. The long thin stainless tube in the upper left is the new line to the pressure gauge. The long straight copper line is the exhaust in case I needed to make a new one, but I was able to reuse the original.

Image

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TomC
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Postby TomC » Dec 07, 2016, 3:19 pm

michael wrote:more pictures please

do you know the size of the restrictor that now comes standard on the GS3 MP 8)


My understanding is that they pretty much all run 0.6mm restrictors. But like I mentioned previously, the stock vs the one I put in looked obviously different in terms of inner diameter.

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TomC
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Postby TomC » Dec 08, 2016, 1:59 pm

The next stage of homework for the Linea is to increase the pump pressure back to 9 Bar against the blind basket again, and then recalibrate the flowmeter down. That should open my range up considerbly and I'll probably be able to grind a lot finer as a result.

I have the Shureshot set at a 8 second pre-infusion stage, but I think it'll be fun to extend that significantly. Getting some feedback on Facebook by other users more familiar with this sort of control has been nice. It seems many users prefer to have as much control over the pre-infusion phase as their primary goal.

ziggomatic

Postby ziggomatic » Dec 08, 2016, 3:29 pm

Awesome, has me dreaming of having this mod for my Linea Mini, guessing thats a bit far fetched at the moment.

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TomC
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Postby TomC » replying to ziggomatic » Dec 08, 2016, 5:12 pm

I think not. Reach out to him. I know he has things in the works specifically for the Mini. He bought one just to modify it and start doing cool things to it.

mivanitsky
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Postby mivanitsky » Dec 08, 2016, 5:27 pm

Looks fantastic, Tom!

I look forward to hearing how your R120 pairs with your "Slayer."

Also very interested in seeing this mod on a LMLM, as that would be a very compact and cost effective way to get that functionality on an office machine.

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TomC
Team HB

Postby TomC » replying to mivanitsky » Dec 08, 2016, 5:29 pm

I think a modified LMLM would find a dominant niche in the upscale home user for sure. Smaller, with equal capabilities. I haven't used the R120 with it yet, I'll probably eventually give it a try, but the R120 will probably end up getting sold soon, if I shift focus back towards the espresso end at home. I already have plenty of other batch brewers and although the R120 is the best at it, It's also taking up some prime real estate in my tiny apartment.