The new lever group thoughts - Page 3

A haven dedicated to manual espresso machine aficionados.
samuellaw178
Team HB

Postby samuellaw178 » Jun 03, 2016, 12:40 am

Wow Paul, thanks for the in-depth go-over!

The 12-14 bar spring force is weird. Are you using line pressure or purely boiler pressure generated by steam? That bit wasn't clear to me. I have a theory myself after trying both boiler-preinfused and line-pressure pre-infused levers. You need a higher spring rating for boiler-preinfusion (0.8-1.2 bar) compared to line-fed (2-4 bar). The reason is the higher initial pre-infusion removes more air from the group and the lever kicks in earlier (because less air to compress). If your boiler is pressurized by line pressure, it could be the reason. Boiler pressure= use a high spring rating ; Line pressure = use a low spring rating. I've measured a recent Bosco-style group (on a Profitec 800). It's about 9-10 bar with flow (it needs a good pull strength so I believe it's double spring).


As for the E61 screen sitting too low, it can be made to work but not easy (for us - probably easy pie for ya :D ). Rick (Coffee_machinist) has trimmed some material from the sleeve so the screen can sit higher - best of both world.

2nd post pic no. 8.
http://coffeesnobs.com.au/brewing-equip ... ution.html

After seeing your photos, I have to say I am glad to have an older style lever grouphead with pop-on screen. :P Never seen that much build up on mine! And completely agree with you that levers should be easy and no thoughts required.

p/s: I love your Cafelat silicone grouphead seal and lucky me, it fits my Brugnetti Aurora with a bit of help. Can't wait to try your silicone piston seal IF(big if) that's in the pipeline. It uses Faema's W and V seals.

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Balthazar_B

Postby Balthazar_B » Jun 03, 2016, 12:45 am

It's a few years old, but FWIW here's an article on shower screen removal on a Bosco Sorrento:

https://comingsooncoffee.wordpress.com/ ... -cleaning/
- John

LMWDP # 577

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TomC
Team HB

Postby TomC » Jun 03, 2016, 12:47 am

Paul, your posts are solid gold as always.

I've long wondered what my San Marco group would be like if I were to remove the second spring as well. Unlike the other 58mm lever groups, as you know, we're stuck with fewer options, but the circlip retained screen does sit higher than a regular e61 screen on mine would. Mine's been maintenance free since the day I got it. I also was given some prototype shower screens by IMS a year or so ago, and although they're nice to look at, I don't see much a difference in the ultimate results, the cup.

I note on my San Marco group that the inner group sleeve seems to stick quite low in the whole group, so that a large, tall dose isn't really possible. So that means a finer grind to resist those two powerful springs, and occasionally, duller shots.

Hint, hint: if you ever feel like making silicone seals for the San Marco group, please let me know!

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IMAWriter

Postby IMAWriter » Jun 03, 2016, 1:25 am

Awesome post, Paul.
As regards the IMS screen, for whatever reason the bezzera Strega group doesn't seem greatly change as the Bezzera OEM and IMS install the same, beneath the gasket. I didn't measure, but I noticed no difference in puck contact with the screen with the same 18 gram dose in the HQ double, or VST double, dose being comparable as before the screen switch.

I guess the Bezzera group is significantly different in certain ways to the group(s) you displayed. I have to say I find the black cowl butt-ugly. Of course the pseudo SS plastic cowl on the Strega ain't much better. Still, I'll be most happy to trade machines with you "warts" and all. :lol:
Rob
LMWDP #187
www.robertjason.com

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drgary
Team HB

Postby drgary » Jun 03, 2016, 1:26 am

Fascinating thread. Thank you Paul and everyone else who created this treasure trove of information. Looks like a FAQ to me. :D
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

mathof

Postby mathof » Jun 03, 2016, 5:27 am

The Londinium comes with only one spring in the group. Reiss has written in his blog that he tried the two-spring configuration but didn't like the coffee that it produced. Like Paul, he observed that it tasted more like espresso from a pump machine.

Matt

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Paul_Pratt

Postby Paul_Pratt » Jun 03, 2016, 6:02 am

samuellaw178 wrote:The 12-14 bar spring force is weird. Are you using line pressure or purely boiler pressure generated by steam? That bit wasn't clear to me. I have a theory myself after trying both boiler-preinfused and line-pressure pre-infused levers. You need a higher spring rating for boiler-preinfusion (0.8-1.2 bar) compared to line-fed (2-4 bar). The reason is the higher initial pre-infusion removes more air from the group and the lever kicks in earlier (because less air to compress). If your boiler is pressurized by line pressure, it could be the reason. Boiler pressure= use a high spring rating ; Line pressure = use a low spring rating. I've measured a recent Bosco-style group (on a Profitec 800). It's about 9-10 bar with flow (it needs a good pull strength so I believe it's double spring).


I made a twin boiler system. Both boilers are completely separate from each other. The coffee boiler like I said is the same as say a marzocco saturated system. It is fed by line pressure, which becomes the pre-infusion when you pull the lever down. Since the coffee boiler is 100% full of water and no air, I added an expansion valve to open around 12 bar, during the normal operation the pressure in the coffee boiler idles between 1.5 and 12 bars.

When you pull the lever down the pressure will drop immediately to line pressure. I have line pressure set to just over where a traditional steam boiler would be at, around 1 - 1.2.

Personally I have never considered that the 1 spring or 2 spring was anything other than, 1 is good so 2 must be really good. I would estimate 99.9% * of levers in existence are "dippers" and a miniscule amount are HX fed from mains water. * Total random exaggeration of course.

Javier

Postby Javier » Jun 03, 2016, 8:14 am

a long story short...
The seals don't work
The spring pressure is far too high
The E61 shower screen is not suited to this group


Hi Paul!

Thank you for bringing so much knowledge about lever machines to the forum.

I recently bought a Londinium L1. Will you be selling that pop-on/pop-off screen through Cafelat? And, are you currently selling the same type of silicone group "V" seals/rings that you just installed in that group?

Always a pleasure to have you in H-B forums!!

Javier
LMWDP #115

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JohnB.

Postby JohnB. » Jun 03, 2016, 9:10 am

My only experience with this group is on my Sorrento. Bosco uses a single spring giving a peak measured pressure of just over 8 bar. When I updated my 2011 group with the later style 4 seal piston/silicone seals in Jan. 2015 the original rubber seals installed in 2011 were still sealing just fine.

Finicky doses? I use an IMS 200 screen & dose 18g in an HQ 14 basket, 20 grams in an HQ 21 double basket & haven't had head space issues. I do flush after every shot just as I do with the Speedster but I've never seen a build up on the side of the screen. The IMS 200 screen will give you a little more headspace due to the flat screen.

Also when I asked Roberta Bosco what was required tool wise to remove the piston she sent a video of one of her workers removing & replacing the piston by hand. I ended up using an adjustable pin wrench to get it started & then unscrewed & replaced it by hand. Another Sorrento owner who updated his group at the same time said his came apart by hand with no tools required.
LMWDP 267

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Balthazar_B

Postby Balthazar_B » Jun 03, 2016, 10:29 am

JohnB. wrote:My only experience with this group is on my Sorrento. Bosco uses a single spring giving a peak measured pressure of just over 8 bar. When I updated my 2011 group with the later style 4 seal piston/silicone seals in Jan. 2015 the original rubber seals installed in 2011 were still sealing just fine.


John, who sells the silicone piston seals?
- John

LMWDP # 577