I've been pondering this question and can't come up with a good answer. Seems that a thermally stable group is what is lacking on most lever machines. If the water could still be provided by a lever operated pump inside the boiler, what would be the pros and cons? Would this be the ultimate machine or not?

I agree the machine above is a thing-of-beauty. But what about a La Marzocco group and submerged manual pump inside the boiler? I'm wondering why no one has gone there before....or have they and I've not found any?

Hi Ralph,

one thing to consider is that big groups (like the CMA ones Kees uses in the machine above) have a whole lot of brass. Once up to temp, these have the effect of keeping the water at a very stable outlet temp. Many are also saturated (in a way) via the inclusion of thermosyphon loops.

starry wrote:I agree the machine above is a thing-of-beauty. But what about a La Marzocco group and submerged manual pump inside the boiler? I'm wondering why no one has gone there before....or have they and I've not found any?

No reason you couldn't do something like that with a 1-group. You'd have to fabricate the pump. I've thought of doing that with my old PID'd Silvia that I still have. WRT 'zocco's, multi-group machines would be harder to do. In the case of a 1-group you'd be quite flexible where to put the pump. I don't think that it would be smart to mount it onto the group neck or group since these parts were not designed to have lever loads exerted on them. You'd wanna mount the pump upstream of the brew boiler. With a two group you'd have to have a scheme for switching between two-groups with one pump. Obviously that's done electronically with the multi-group LMs. You'd have to either switch electronically and pump by lever, or install dedicated pumps in the flow system upstream of the group delivery banjo tube. I would think that doing so would pose significant heat sink issues and it wouldn't work well. Better to pump cold water into the boiler rather than heated water from the boiler to the group.

Presumably you're familiar with marzocco innards and know that the water in the neck isn't necessarily the water that makes its way immediately to the shower screen. Lineas pick up water from the main body of the brew boiler, flowing the water through a tube to the group solenoid, then to the group via a copper tube contained within the neck. The heat lost from the water as it goes through the group solenoid is supposed to be regained as the water flows up the neck, but Lineas tend to run cold in intermittent duty because some of the brew water sits outside of the boiler in the tubing and group solenoic. Semi-auto Lineas are better in this regard than full autos, which also have an exposed flowmeter. The new GB5 completely fixes this problem by integrating the group solenoid into the top of the saturated group. No water ever leaves the boiler and neck, so these machines produce consistent temperature regardless of duty cycle. Again, a lever operated water delivery system that didn't muck with the good thermal characteristics of the saturated group should be mounted upstream of the brew boiler.


-Greg

Excuse the hijacking of this thread. Similar question.
The combination of my ignorance & the simplicity of the following concept probably means it has been already considered and it's full of problems.

Two boilers and massive groupheads with a thermosyphon loop. One boiler for steaming. One boiler with an HX unit that is direct plumbed. Household water pressure with a reduction pressure valve to keep the water pressure within the HX at 30psi or whatever is needed to allow passive filling of the grouphead. No need for pumps since the water pressure loads the grouphead when the lever is pulled (spring lever machine), the spring generates the pressure as in a normal spring lever machine. With the exception of steam from the steam boiler no water is being drawn from the boilers. Sorry, no water wand. Sight water level glasses for both boilers. The need for manual refill of the boilers would be minimal. Use of distilled water would reduce scale deposits. Easy access resetable thermal safety fuse, commercial quality vacume valve, pair of pressure gauges and an easily accessible commercial quality pressurestat. Not much else in terms of electronics. Twin 49mm groupheads would allow a tag team approach reducing the wait or dealing with portafilter sneeze.

Why not?

Paul wrote:one thing to consider is that big groups (like the CMA ones Kees uses in the machine above) have a whole lot of brass. Once up to temp, these have the effect of keeping the water at a very stable outlet temp. Many are also saturated (in a way) via the inclusion of thermosyphon loops.

Thanks for the input Paul, one thing I've learned from PID'ing my Cremina is that yes, the "mass of brass" does hold it's temperature fairly well, but with just a single pull of the lever when the machine is up to temp I see a corresponding drop in the boiler temp of as much as 5 degrees with the boiler about two-thirds full. In-turn, the group heats up some. After that of course, the boiler resumes heating until it reaches the set temperature, but the group hasn't lost all the heat it's just gained. That's why I asked the original question. I'm thinking that a saturated group would work even better.

gscace wrote:Presumably you're familiar with marzocco innards

I am somewhat familiar but don't have a working knowledge of LM's innards. If one isn't "in the business" is there a way to learn about the innards other than just trying to make sense out of the drawings that can be found online in the LM manuals? I would LOVE to get my hands on an old LM group somewhere or even a whole machine that's been trashed. Surely there must be an espresso machine "junk yard" somewhere! I'd like to tackle a project like this but wouldn't do it without becoming intimately acquainted with the vital parts. If someone knows where a wrecked LM machine is, please PM me.

I suspect that different flavors are brought out by the slight variation in temperature that occurs with most espresso machines. Although I think its important to experiment with temperature and to maintain a certain level of consistency, I just don't see thermal stability as the Holy Grail that most seem to view it as. Even the solid chunk of brass that comprises the little 45-mm group of my Ponte Vecchio affords enough stability for my taste, although I'll admit to a certain amount of envy for those CMA groups. The Pavoni, on the other hand, I found to be less satisfactory in this regard, and I suspect the Cremina is similar in group size.

I guess I just love drinking the stuff too much to get too fussed over brewing it.

PC

peacecup wrote:I suspect that different flavors are brought out by the slight variation in temperature that occurs with most espresso machines. Although I think its important to experiment with temperature and to maintain a certain level of consistency, I just don't see thermal stability as the Holy Grail that most seem to view it as.

Peacecup, I suspect you are right. I've not seen any formal discussion on this, but if it's a fact, then I will speculate that it is still important to find what range of temperature produces the best results in the cup. It would be an interesting and complicated exercise, but I think a worthwhile experiment.

On a side track.... That is why I prefer hx machines to the more talked about twin boilers. Besides the water quality issue which could be argued all day, I have found that shots pulled on mazoccos and synessos tend to focus in on one particular flavour, especially when temp tuned, and the trade off for this is complexity. The clean water of a hx coupled with slightly variable temperature (more slightly in some than others) gives the espresso more complexity.

On topic, I have been given a Silvia with a leaky steam arm, not the seals. I could just use the Silvia as is and the Pavoni as is, but I'm a tinkerer. I've also fallen in love with the direct lever espressos and process. I've been wondering how I can couple this with my Pavoni to have a machine that can produce multiple shots. My only complaint with the Pavoni being recovery time between the whole process and doing it again later. I'd love to have something I could leave on and pull a shot on when I felt the urge. I'll probably tackle the project in the new year but will be sure to post the results when it happens. Any suggestions / tips?