orphanespresso wrote:You are describing .................. no substitute for the obervational skills and barista technique needed for any good espresso production from either the most complex or the most simple machines.

Thanks Doug! This info is pitched just right - exactly what I was hoping for. And good to hear that it's the man, not the machine that counts. Some more naive questions for you: (i) Am I right in thinking that only a boiler pressure gauge will allow me, or a good barista, to use the machine as you describe? I want to use as few devices as possible, but good ones. (The CMA lever Rapallo, which is what I am basing my machine on, only uses a pressure gauge, as far as I can tell, but (ii) presumably there is a thermostat, although with no visual temp indication?). (iii) How does the barista control the pressure/temp in the boiler on this kind of dipper machine as you describe? The only controls I see are manual on/off on the boiler heating element, steam out, water out and water in. Apart from pulling shots.

Sorry the questions are so elementary, but going through the CMA parts diagrams doesn't show me any more controls than I've listed and I don't want to build a machine only to discover I've missed off something vital like the group or a way to get water into the boiler. I'm more used to building old Italian bikes than old Italian coffee machines and that's more obvious - stop, go, left, right, engine in the middle, wheel at each end.

Thanks again.

At the very least, you need everything an Elektra MCaL has.
-boiler
-group
-element
-some form of element control, be it a pressure stat or a thermostat
-Pressure gauge
-frame
-water level sight glass

Tim....just as Bluecold listed, add a few small bits such as a power switch and a pressure safety valve on the boiler, some valve to fill the boiler etc and you will have a lever espresso machine. As far as the way it works....the "temperature" will be controlled by the pressurestat, the pressure gauge only reflects the current pressure in the boiler, and to a small degree the temperature. If you use a Sirai pstat, this will have a range of about .2 bar between on and off, so if it is set to be 1 bar off you can control the water temp a bit by watching the gauge and pulling the shot when the element turns back on at .8. This type of approach has a small effect since the group is large and retains heat so basically, one just gets the pressure set and uses the machine. If you do not connect the group directly to the boiler, the group will require warming flushes etc to get the temp right but seems like you are proceeding to an understanding of the mechanics of the machine. Makes me want to start dabbling with some projects of my own here.

Perfect! Thanks Bluecold. Thanks Doug.

Please keep us posted on your progress. This sounds like an interesting project.

Certainly will. Next is to work out best 3/8 copper tube to use, how to bend it neatly and where to source brass 3/8 connectors. I'll post some photos as I progress. All guidance, tips etc. gratefully received.

I agree with doug- you definitely want a pressure gauge.

If the pressure drops below 1 bar in the boiler, won't it suck air in rather than pushing water or steam out? Or does the pressure in the group from the raising piston drop even below .8 bar? But the steam and hot water?

The gauge displays the pressure difference between the surrounding pressure and the boiler pressure. So 0.8 bar actually means 1.8 bar.