About lever machines & group pressure.

[Tex]

After I rebuilt the last lever machine (Rancilio 2-group) for a friend, I kept it for a few months (my price for doing the work at cost - with my La Cimbali M32 standing in for him).

I liked the mechanics and feel of the machine and I liked the quality of the coffee it made. One thing I could never figure is how to adjust the group pressure? When I checked it with a manometer it was a constant 8.4 bar static pressure (~7.5 bar dynamic pressure).

There didn't seem to be a way to conveniently, or even safely, change the preload of the spring. Other than changing the springs, how are these groups tuned for brew pressure?

[Warrior372]

The springs in spring loaded levers range from 8-10 bars depending on the manufacturer. I am assuming they have a performance / taste in mind and end up manufacturing specific machines with springs that cater to those requirements. Something you can do with a spring lever is add your own pressure if you are not content with the pressure on any given pull of the lever. Outside of that you would have to just install a different spring. Did you install a new spring when you rebuilt your friends machine? I am not sure what exact pressure Cimbali's are supposed to function at through a shot.

[Tex]

The springs in spring loaded levers range from 8-10 bars depending on the manufacturer. I am assuming they have a performance / taste in mind and end up manufacturing specific machines with springs that cater to those requirements. Something you can do with a spring lever is add your own pressure if you are not content with the pressure on any given pull of the lever. Outside of that you would have to just install a different spring. Did you install a new spring when you rebuilt your friends machine? I am not sure what exact pressure Cimbali's are supposed to function at through a shot.

The lever was a Rancilio (CMA??). The springs were only 3 years old when I rebuilt it (it got caught in hurricane Ike surge). I was considering having some shims made so the preload could be higher, but in the end I figured if he liked it before I might as well return it like that.

It just seemed strange (after working with so many rotary pump machines) that the things have no provision for changing group pressure?

[Warrior372]

The bar pressure of a lever is supposed to be one of the main highlights of the machines. I think I misread your first post. The spring statement I made is valid, but the pressure profile of a lever itself is meant to be linear starting high, when the lever is pulled all the way down and the spring fully compressed, and finishing at 0, when the spring is again fully relaxed. This pressure profile is viewed as very desirable by many and is one of the reasons the manufacturers of the Slayer wanted to be able to pressure profile. A lot of individuals also attribute the nuanced shot of most levers to this pressure profile.

[Tex]

The bar pressure of a lever is supposed to be one of the main highlights of the machines. I think I misread your first post. The spring statement I made is valid, but the pressure profile of a lever itself is meant to be linear starting high, when the lever is pulled all the way down and the spring fully compressed, and finishing at 0, when the spring is again fully relaxed. This pressure profile is viewed as very desirable by many and is one of the reasons the manufacturers of the Slayer wanted to be able to pressure profile. A lot of individuals also attribute the nuanced shot of most levers to this pressure profile.

So, if I'm understanding you, there is no way to accurately measure the group pressure because it's constantly changing throughout the pull? That's what I figured was happening, which is what frustrated me the most - I am used to the constant pressure profile of the rotary pump and tailoring the group pressure to slightly less than 9 bar. So it's not possible with a lever?

Well, if I ever find my Visacrem lever I suppose I can get used to that.

[Warrior372]

There is one for sale on CL. It has been up for about 2 weeks now. They are asking $2,000, but it is not moving. . . . . I think it was in Tulsa, OK.

[Tex]

There is one for sale on CL. It has been up for about 2 weeks now. They are asking $2,000, but it is not moving. . . . . I think it was in Tulsa, OK.

It's close, but not the model I want. I'll just work with what I've got 'til one turns up. Thanks anyway!