@DaveCThank you very much for the very interesting description of the design process. It is remarkable that you have managed to get the LSM brewing group to perform as intended despite the "manufacturer's statement".
I know that everyone who visits this thread frequently is impatient to read/(watch the videos) your review.
Stays safe!
Don't misunderstand, it's the commercial spring levers in a prosumer single spring configuration that don't work as intended. They were designed with 2 springs and approx 2 bar preinfusion for a reason. it does make them significantly harder to pull, so this places more challenges on the case and machine design.
To give you an example a typical single spring configuration maxes out at around 8 bar (that's against a blind filter), against coffee it might not even quite make 8 bar, then will drop
very rapidly, with a large proportion of the shot produced at sub-optimal pressures. Certainly nowhere near design pressures.
A double spring maxes out at 10.2 to 11 bar depending on spring age (the group in Frankenstein is probably 10+ years old and came out of a well-used commercial machine). The profile is also quite different. A single spring prosumer config can have the lever cocked with your little finger...with a professional 2 spring set up....no way, you won't even move it more than 5mm..It's why commercial spring levers are mounted up on higher counters, to make them more comfortable to pull.
When you get that great shot on a commercial machine in a hi end coffee bar and want to replicate it at home, it's pretty hard because their setup and the prosumer one is so different. My involvement in levers started with the Izzo Pompeii over 15 years ago, which was a LSM style group, dual spring. Always produced a great shot, but the single group was too large, so I gave up on owning one. 🤣
Paolo at ACS has considerable experience in levers over many many years, long before the more standard pumped machines..
