All this computation of brew pressure is academically interesting but missing the point with a lever which is that you get an intuitive feel for what works without higher mathematical though. At least that's what I get out of it and why I didn't even bother to add thermometry or gauges to my Faema Faemina.

What I get out of levers is great tasting coffee.
I also get more direct control over more parameters, which gives me more flexibility, but since humans are notoriously bad at consistency through repeated tasks all the thermometer and gauges I hook up to mine help me achieve that consistency.

I went through this a long time ago, when we'd had our Europiccola for a while and I wondered about pressures.

The official standard for espresso calls for 9 bar pressure. Whether that's a good number or not, it isn't immaterial - pressure does matter, and there's a widespread notion that lever machines generate lower pressure. So it's interesting to actually have some real knowledge about it. The inquiry doesn't imply any particular intention to use that knowledge in any particular way. So far I haven't noticed any mention of using it, at all - I guess you'd have to hook up a scale?

jonr wrote:b) it's not clear that people press straight downward (versus in an arc).

For the records, here the result for a constant force perpendicular to the lever (following an arc rather than straight downward), it also produce a profile.



The "real" profile is certainly between the two, since the force applied is depending on the factor "I don't want the machine to tip".

As donn mention, all this is just to improve the knowledge about the machine conception, not to actually use it to extract espresso.
It also demonstrate how the Dottore Salati's piston is brilliant: it is incredible how his conception is able to produce so much efficiency and piston travel in such a tiny space.

donn wrote: So far I haven't noticed any mention of using it, at all - I guess you'd have to hook up a scale?

I have simply put the batroom scales under the machine to get the feel of the force.
Same thing tamping.