SPRING Lever Espresso Machine types - defined - Page 4

#31: Post by **JohnB.** » February 6th, 2023, 2:28 pm

baldheadracing wrote: Like the horseshoe HX, from the outside the group mount for the diagonal HX looks like the group is mounted to the boiler like a dipper. However, the inside of the boiler neck is not connected to the boiler water - the neck is an extension of the diagonal HX tube. Thomas calls this neck area a "reservoir" - which it definitely was with the horizontal HX.

So you're saying that the Lapera doesn't have a real water reservoir behind the group like the Bosco??

February 6th, 2023, 3:03 pm

I'm saying that the neck welded to the boiler is the reservoir as the neck is not hydraulically connected to the boiler chamber. The neck's impact is to lower brew water temperature, regardless of HX orientation, or external appearance. An attached cylinder or a wider diameter neck can both be designed to control brew water temperature. They're both real in terms of action; one is just more visible.

#33: Post by **Primacog** » February 6th, 2023, 7:09 pm

RistrettoCapp wrote:I'm just entering the world of spring lever machines, and haven't found any clear definition of the three types: Dipper, Thermosiphon and saturated (are there others?)

I've searched the forums but search doesn't return anything related to defining these types.

Can you spring lever gurus, and users, chime in and define each one of these types, along with their pros and cons?

ADDING DEFINITIONS AND INFO UPDATES HERE FOR FUTURE READERS:
Dipper groups:
Bolted directly to steam boiler, draws in steam boiler water that is hotter than needed and cools, by way of the group-head absorbing/radiating heat, to the correct brew temp.
Subsequent 'flushes' will INCREASE the brew temp, by increasing the group temp.
Video here showing a Dipper Group-head: https://www.baristahustle.com/lesson/em ... -machines/
EXAMPLES:
Profitec pro 800 - with added PID and vibe pump to fill the boiler from the pour over tank
Pompei or Nuova Pompei by Izzo
Alex Leva by Izzo
Bosco Sorrento
Salvatorre machines (CMA group?)

Thermosiphon groups:
Thermosiphon groups use two thermosiphon pipes (a feed pipe and a return pipe) to circulate water from one end of the heat exchanger, around the group with a water jacket behind the sleeve, and back to the heat exchanger via the return pipe of the thermosiphon to be heated up again. It is a passive method of heat exchange, based on natural convection, without the necessity of a mechanical pump. Thermosiphon groups can be mounted away from the steam boiler because they are only 'connected' hydraulically via the Thermosiphon loop pipes.
Subsequent 'flushes' on a Thermosiphon or HX group, will DECREASE the brew temp as fresh, cooler water is drawn into the HX tube AND/OR the group absorbs/radiates heat from the water
EXAMPLES:
Londinium R24
Quick Mill Veloce
Salvatorre machines (VBM group?)

Saturated groups:
Saturated lever groups, like their pump counterparts, are connected directly to a brew boiler and have brew water encasing the group to maintain thermal stability. The main differences between Saturated and Thermosiphon group types is that Saturated groups use Brew Boiler water (Thermosiphon groups run water from the Steam Boiler through the group-head) and Saturated groups are always connected directly to the brew boiler - they are typically PID controlled as well.
Subsequent 'flushes' have no effect on the temp of shots, as the boiler water, group-head and brew water are all maintained closely to the same temp.
EXAMPLES:
Kees van der Westen Slim Jim Idrocompresso

Actively Heated groups:
A newer technology that replaces previous methods of heating the lever group with cartridge or other active heating elements. These are usually used on Dual Boiler, PID controlled machines that maintain the brew boiler temp accurately. Actively heating the group-head allows for even finer control of brew temps as the user can, usually, control the brew boiler temp via PID AND the group-head temp separately.
Subsequent 'flushes' have no effect on the temp of shots, as the boiler water, group-head and brew water are all maintained closely to the same temp.
EXAMPLES:
Nurri L-type Leva (PID controlled dual boiler leva with an actively heated group)
Bezzera Strega

I would add also the point that for the nurri, the groupjead is in fsact insulated from rbe boilers so that the latter have as little effect on the temp of the grouphead as possible except for the hot water flowing from the brew boiler to the grouphead when the lever is lowered. Also many in this category also use pumps to drive the preinfusion rather than line pressure.

Also another example of a saturated group grouphead lever is the LM LEVA X.

#34: Post by **pizzaman383** » February 6th, 2023, 8:21 pm

One can make a classic lever machine group perform like a saturated group head by adding a silicone band heater around the group head bell. I liked the idea and added one such that my group head is heated at the neck and at the bell. The result is that it behaves like a saturated group head. It has made the espresso much more consistent from shot to shot.

February 7th, 2023, 12:47 am

Your modified lever arrangement would therefore fall under the category of actively heated levers under the OP'S taxonomy.

February 7th, 2023, 2:40 am

Which would be one of the shortcomings of the first post.

Electrically heating a group that has a water jacket around much of the brew chamber in a way that emulates a saturated group is very different from electrically heating the group's neck to emulate the heat path of a boiler-mounted group.

February 7th, 2023, 10:39 am

Except for the fact that the brew chambers (and water jackets) are not like that. Plus there is the the flow aspect and passing a thin layer of water down the group outer chamber sleeve and then a bottom fill for the group on LSM style machines.

Also electrically heating the neck of the group is absolutely not the same as the heat path of a boiler mounted group. It's quite a bit more complex than that. I know because I help design these things.

February 7th, 2023, 11:11 am

You helped design the Strega?

Regardless, I wasn't talking about the LSM group. The LSM group is not the same as the modern lever group - as I am sure that you are aware of. However, I am not sure that you are aware of all the mods Curtis has made to his group and machine.

ETA: The underlying point is that taxonomies have some simplification, depending on their goals. As far as purchase decisions are concerned, I don't see the value in putting the Strega and Nurri together just because they both have electric heating of the group. (The ACS and Leva X aren't mentioned/included in that section of the taxonomy.)

#39: Post by **Oskuk** » February 7th, 2023, 5:57 pm

All groupings of types are having some broblems.

These technical wiews of these machines are interesting. But, even so,
these does not help plenty of one wanting to buy one.

Are we perhaps forgetting milk? The machines qualities for milk-frothing are not the same.
But, if we are talking only the espresso, I'd just say that any of the technical version of the theme one can make just like the coffee one wants to.
It hardly is in the machines type, which makes bad coffee, or good -it is the dude and the beans.

One grouping style of differentiate machines could also be: which machine has what annoyancies and how many of those?

But still: these are very interesting. Why someone ended on which technical solution on particular machine etc...

#40: Post by **pizzaman383** » February 9th, 2023, 8:33 am

baldheadracing wrote: [snip]
Electrically heating a group that has a water jacket around much of the brew chamber in a way that emulates a saturated group is very different from electrically heating the group's neck to emulate the heat path of a boiler-mounted group.

and

DaveC wrote:Except for the fact that the brew chambers (and water jackets) are not like that. Plus there is the the flow aspect and passing a thin layer of water down the group outer chamber sleeve and then a bottom fill for the group on LSM style machines.

Also electrically heating the neck of the group is absolutely not the same as the heat path of a boiler mounted group. It's quite a bit more complex than that.
[snip]

Based on my experience both of these statements are true. The thermodynamic characteristics of the group head, the method of heating the group head, the group head shape and materials, the method of heating the water, and the combined water path all come into play. One needs to design them together as a system. The group head is probably the thing that sets the most constraints on the other components. I learned this by successive experimentation, design, and measurement steps. It is very likely that DaveC, ACS, and Vostok have also experimented, learned, and adjusted as clearly Kees and LM did when they designed their modern saturated group levers. Unless you are willing to experiment and modify/build an espresso machine you need to pick the combination of components each machine has then you'll adapt your espresso-making to the machine you buy.

I have found that the espresso machine, the grinder (and burrs), the coffees, the filter baskets (and puck screens/papers), and the prep methods used all interact substantially. Changing out one may mean that you need to change one or more of the others to get results as good or better than before you made the change.