Cool!

I will add a couple of advantages to having a manual vs spring lever:
1- helps with inconsistency: I am not particularly consistent in espresso routine. I also switch beans and grinders from time to time, and spending time dialing in shots at some times is not option I like to do. A manual lever suits my inconsistencies, and it helps save my shots and my day:)
2- Using a commercial spring lever is not safe in some households/environments. If the user have half knowledge about the thing, he/she might end up hurting self or someone around.

After a week of daily driving the single spring lever and the manual lever here are my observations:

• The feel of the spring lever is like using a powerful machine (even more so with the dual spring installed) that you initiate and let it do the work.

• The feel of the manual lever is like using a finely crafted precision machine where you are directly controlling the work.

• The shots pulled back to back (30 minutes apart so the temperature is the same) are nearly indistinguishable with the manual pull being maybe a little softer.

• Puck prep is equally important in either configuration

• Temperature behavior seems to be the dominant factor impacting taste because the length of preinfusion determines how much heat bleeds out of the water in the cylinder before it is pushed through the coffee - longer preinfusion adds more sour notes proportional to the length of preinfusion time one waits after the sound of water flow stops.

• Achieving the same flow using the manual lever as the single spring provides is comfortable. Archiving the same flow as the dual spring required more pressure than I would like to do on a regular basis.

• For the classic Italian espresso blends I love I prefer the manual lever first, the single spring lever second, and the dual spring lever third

Very interesting findings.

This is really awesome!

I'm in shock nobody has tried to do it before, but the modifications you did look nontrivial.

beer&mathematics wrote: I'm in shock nobody has tried to do it before, but the modifications you did look nontrivial.

If I was a machinist with the right tools it would have been simply making a new cam fork. Since I am not it was quite a bit of grinding and filing.

If I could get a manual pro800 out of the box this would be an end game machine for me

Pizzaman, great work. This seems like all of the temperature stability you'd want from a commercial group, but all of the control you'd want from a direct lever. Question, what sort of shot volumes can something like this achieve? For modern roasts, I have seen that it is a struggle for many La Pavoni users to pull a shot longer than 1:2, even with Fellini. Have you found that you can pull long shots without fellini move and risking puck lifting?

I regularly pull 45 gram shots and have pulled 60 gram shots.

That's RAD! An extreme idea! I had to read it twice . Try to puzzle it together and see if it could work with our parts. Congratulation Curtis!

When you peak Gabor's interest...

Guess we're about to see what kind of pressure a commercial manual group can create!

Graphs and measurements coming our way!