DIY Commercial Group Manual Lever (now with videos) - Page 2

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MemPast

#11: Post by MemPast »

You rock, Curtis!

I have a couple of La Pavonis, and I struggled with temp management. I then bought an MCAL, and liked the temp stability compared to La Pavoni, since the group head is bigger. However, did not like the shots from it--they were weaker than my La Pavoni's shots. It might have been a weak spring, or issues with the orings, but I gave up early. I thought about converting the MCAL group to manual, but did not have the resources then, so sold it.

Wish to see the fruitful work in the Bosco group case. (I have one myself, but DIY smallish machine with a Bosco group is in the works since 3 years--I am just lazy).

Wish to see more details (pics and detailed descriptions) about what you did to the group to make it manual.

pizzaman383 (original poster)
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#12: Post by pizzaman383 (original poster) »

MemPast wrote:You rock, Curtis!

Wish to see the fruitful work in the Bosco group case. (I have one myself, but DIY smallish machine with a Bosco group is in the works since 3 years--I am just lazy).

Wish to see more details (pics and detailed descriptions) about what you did to the group to make it manual.
I will post some pics next weekend after using it for a week. I will need to take it apart to get the pictures.
Curtis
LMWDP #551
“Taste every shot before adding milk!”

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Giampiero

#13: Post by Giampiero »

Ok, clear, i misunderstood your first post :D

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redbone
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#14: Post by redbone »

Wonder how this is different from retarding a spring machine. Having done this many times especially on second pulls whereby the spring rate is too strong.
Between order and chaos there is espresso.
Semper discens.


Rob
LMWDP #549

pizzaman383 (original poster)
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#15: Post by pizzaman383 (original poster) » replying to redbone »

It is very similar so if you are comfortable with retarding the spring lever then it has no additional value.

I never warmed up to retarding the lever and I wanted another project to try and this was it :lol:
Curtis
LMWDP #551
“Taste every shot before adding milk!”

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redbone
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#16: Post by redbone »

Can't argue against projects as I have pursued many, always a great learning experience. Having a few manual and spring prosumer lever machines it's nice to be able to rotate them monthly. One develops a feel with the full manual machines that although takes a while it then becomes second nature to repeat like riding a bike even months later. Will be following project as you may be the first with a commercial group.
Between order and chaos there is espresso.
Semper discens.


Rob
LMWDP #549

pizzaman383 (original poster)
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#17: Post by pizzaman383 (original poster) »

So, I pulled quite a few shots (real and fake) with the manual lever, yesterday. Compared to the smaller lever machines this requires less effort on the lever to achieve the normal range of pressure. You can achieve very high pressure (enough to blow past the portafilter gasket seal - don't ask :oops:) all the way to a very low pressure.

One benefit is by watching the shot weight near the target weight and easing the lever it makes it easier to reach an exact shot volume when doing the cup swap than when using the spring.

There is one discernible negative. It is still a little odd to have to continue the pressure until all the water bleeds out through the puck after the shot is done.

All in all it is kind of fun to pull the shots manually. From what I can tell, the espresso is basically the same. I tend to favor classic italian blends pulled the same way every time and I haven't noticed any substantive differences in the espresso.

As I said, I did this as a fun project and so far it has been fun and effective.
Curtis
LMWDP #551
“Taste every shot before adding milk!”

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LObin

#18: Post by LObin »

Here's a senario where I could see this be beneficial:

- When pulling a coffee that seems either too bitter or too sour, softening the pressure curve and lowering the peak pressure to 5-7 bars usually improve significantly the shots. At least that's my experience having pulled the same coffee on my Londinium and then on my Europiccola, Robot or La Peppina.

When I don't like the flavours I'm getting from a certain roast (either too dark or too light and acidic) on my Londinium, the shots are usually much more enjoyable on my Europiccola or Robot.

I say usually because we've all had coffees that were only good to season new burrs...
LMWDP #592

pizzaman383 (original poster)
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#19: Post by pizzaman383 (original poster) »

Here are some pictures of the parts I modified. The first picture is the unmodified parts.




As you can see, I tried to keep the distance of shaft hole the same distance from the center of the bearing hole but since I lack a milling machine I had to drill just a bit further off center to keep the drill bit fully in metal. I removed about 3/16" of material from the ring. This made it quite thin in some places but whereas the ring pulls up against the spring in its normal configuration with the lever action reversed the ring just pulls the piston upwards with just the friction of the lubed seals against the cylinder so it is plenty sturdy enough for that.

Edited to add: Another important change was made but it didn't require any modification to the part. I reversed the group cap so that the pivot point is now in the back where before it was in the front. You can see this if you look closely in the pictures earlier in the thread. The fact that I was able to do this made this project possible for a non-machinist to accomplish.
Curtis
LMWDP #551
“Taste every shot before adding milk!”

pizzaman383 (original poster)
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#20: Post by pizzaman383 (original poster) »

After a week of using the manual piston assembly as my daily driver I'm really liking it. I find it very easy to modulate the lever pull to control the flow.

I did some comparisons to my spring piston assembly and found that I was generally pulling the lever with less force than when pulling against the double-spring. So, I took out the inner spring and put things back together. I got some spring groaning after reassembly. After a couple of tries I realized that the spring gets twisted as the piston is screwed on. I used some lube on the ends of the spring which reduced it but I also drew a line down the length of the spring coil and used pliers to twist the spring until that line was straight. After that, there was no groaning.

I will be switching back and forth for a while to see which is my favorite configuration but I have to say that I'm really pleased that I now have both options. All in all, a fun and successful prototype.
Curtis
LMWDP #551
“Taste every shot before adding milk!”