New lever machine - club style-Closed Boiler- Second Stage Thread

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sorrentinacoffee

#1: Post by sorrentinacoffee »

I have decided to split my old 'new lever machine' thread into two- as i want to focus more closely on the Closed Boiler design. I have begun discussions with a manufacturer and an industrial designer- at this time the concept is still nebulous but a form is appearing out of the mists...

My talks with the manufacturer have gone well. There is interest in the idea. I would appreciate any help the lever community can offer me on this, and I want to move quickly: technical drawings, links to parts suppliers, ideas regarding improvements to the basic design, indeed any input will all be invaluable in getting this project moving. I need to produce technical drawings and explanations of the basic machine. Any input I get here may well be used and end up contributing to the final machine.

I am now considering a machine along the lines of the Sama type club machine: large enough to operate continuously for multiple shots and sessions- but small enough to be used in a home setting. A closed boiler spring lever- with a high emphasis on simplicity, functionality and build quality. For the purposes of this thread I want to suspend discussions about open boilers, dual boilers, hx's etc. and keep the focus limited to the functional fundamentals of the traditional closed boiler design. If any innovations crop up or seem worthy of attention by all means, but the design starts with the proven system.

for the basic principles we could look to my restored Sama machine- which is a real bare bones, minimalist version of the design.

essentially two main parts:

the boiler with thermosyphon connection, pressure-stat and sight glass, potential for manual or plumbed fill:



and the spring lever group head:



the two joined by a simple structural frame:



Of all the parts the group head in this design is the most worthy of attention- it makes the perfect place to begin any design. It contains the functional elements that give the entire machine its great simplicity, charm and functionality. Choosing or designing the correct group head will be critical.

To begin with I am thinking commercial size: 58mm. Unless someone can tell me why such a group head could not be mounted on a smallish machine.

the next question is: design a new group or source an existing one?

if the latter option is chosen- what are the options? Here I would appreciate any suggestions- or leads to existing groups and designs. Original technical drawings/patents, etc. Any comparisons of the various styles. I have heard the the Kees Idro group is not made by him? If not who makes these group heads and who makes the best ones?

The ideal group should have:

a) a piston that is serviced from the top- and easily removable with simple tools and without un-compressing the spring

b) good thermosypon action, temperature stability, and temperature efficiency (insulated?)

c) an opposable spring mechanism- for user assisted pulls (unless the lever mechanics are sufficient)

d) largish capacity, strong spring, 58mm PF.

and may have

a) some user control over thermosyphon operation?

b) a temperature probe?

If the idea is to design a new one- why? what are the advantages?

I will leave it there for this evening- and see if any ideas sprout by tomorrow.

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timo888

#2: Post by timo888 »

What's your target water-volume per single pull with your proposed 58mm basket?

Do you plan to adhere to the fundamental principle that a single pull should yield a normale with the moderately dosed single basket?

User avatar
Bluecold

#3: Post by Bluecold »

Kees says about some lever machines in his 'earlier work' pages where he got the groups. The straightwalled groups he got from Bezzera and Rossi, and the curvy groups he got from CMA.
Interestingly enough, the Athena lever group for which espressoparts.com lists spares has a lot of parts in common with the CMA group. Which can be completely ordered via espressoparts.
Now comes the surprise, they are special order from Spain, not from Italy, where CMA is located. And the largest player of espresso machine parts i know of in Spain is Ascaso. So if you want one of those groups, i'd try to get a hold of the Ascaso parts dvd.
Still, you won't be able to assist the pulls with those groups.
LMWDP #232
"Though I Fly Through the Valley of Death I Shall Fear No Evil For I am at 80,000 Feet and Climbing."

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sorrentinacoffee (original poster)

#4: Post by sorrentinacoffee (original poster) »

Peacecup- I am not sure about the shot size. I don't think I would mandate a normale from a single pull- if it meant the need to redesign an entire group... to be honest I am not totally unhappy with the shot sizes on my Ponte Vecchio- two pulls doesn't bother me that much. I imagine the servings from the larger commercial groups are considerably larger?

what sort of capacity do the known 58mm commercial groups have?

Roeland- thanks for all those links. I have ordered the Ascanso CD. I wonder if the bezzera group is avialable for wholesale?

Looking at the various group designs posted on coffeeparts- it seems they all have a jacketed piston chamber- with the thermosyphon circulating throughout the entire group? Whereas the ponte vecchio/sama/mcal thermosyphon groups seem to be much simpler.

I imagine that the 58mm groups absorb and dissipate a fair amount of heat from the boiler, would they use quite a bit of power? And would covering them with (say) silicon insulation cause them to be more efficient- or to overheat?

this machine by Kees shows a commercial group with a small boiler:

http://www.keesvanderwesten.com/earlier ... resto.html

User avatar
peacecup

#5: Post by peacecup »

Because of the force needed to compress the 58-mm group spring, you'll need to be very careful where you locate the fulcrum. You should be able to get reasonable estimates of the weights and forces involved.

My experience with the PV Export and the Caravel suggest that the designers very carefully considered the effect of the lever pull on machine stability. Both of these litte machines can have the lever pulled with considerable force with little or no counter-force by the other hand (i.e. holding the machine). Can't do that with a Pavoni! With the Export I can have my second hand free to steam milk while I do my usual lever acrobatics (multiple pre-infusions, half-pulls, etc).

RE: shot volume, you should ask a few veterans which groups produce which.

I know some Conti levers have a "coupled" mechanism that allows upward pressure to be applied for stalled or slow shots. I know of no others besides the MiniGaggia.

PC
LMWDP #049
Hand-ground, hand-pulled: "hands down.."

User avatar
Bluecold

#6: Post by Bluecold »

peacecup wrote: I know some Conti levers have a "coupled" mechanism that allows upward pressure to be applied for stalled or slow shots. I know of no others besides the MiniGaggia.
At least the Brugnetti Aurora group, the Gaggia rack-and-pinion, the Unic rack-and-pinion, the La San Marco looks like it too and i'm sure there are a host of other unknown and unloved groups that do the same trick. The other home groups i know of that allow upward pressure are the La Peppina (Comocafe too) and the Campeona.
Also, if you want 'inspiration' for group heating and thermal stability, you might want to check the La Marzocco lever groups, they've got a nifty heatpipeish setup for heating the group.
LMWDP #232
"Though I Fly Through the Valley of Death I Shall Fear No Evil For I am at 80,000 Feet and Climbing."

User avatar
sorrentinacoffee (original poster)

#7: Post by sorrentinacoffee (original poster) »

Of any of those groups you just mentioned Roeland- are any being used today on modern machines?

the La Marzocco diagrams look great- is that an actual machine pictured in them? Unfortunately the group diagrams are not that large...

and the Brugnetti Aurora type group seems to perform very well (decent volume) in these videos- and has a smallish profile/size? Also the lever is not that long?

http://www.youtube.com/watch?v=IpSoXxtu ... re=channel

http://www.youtube.com/watch?v=AHEREzOnrVI&NR=1

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User avatar
Bluecold

#8: Post by Bluecold »

sorrentinacoffee wrote:Of any of those groups you just mentioned Roeland- are any being used today on modern machines?
La San Marco still exists and sells levers, brugnetti doesn't, unic doesn't, gaggia is now owned by Philips and a hollow shell of their former glory, Fiorenzato and Izzo seem to be using similar groups to La San Marco.
the La Marzocco diagrams look great- is that an actual machine pictured in them? Unfortunately the group diagrams are not that large...
You can enlarge the diagrams and read the descriptions. Pretty awesome design. The water doesn't enter the space above the puck from the side, but through the piston, i guess for more even initial water dispersion.
LMWDP #232
"Though I Fly Through the Valley of Death I Shall Fear No Evil For I am at 80,000 Feet and Climbing."

jmc
Supporter ♡

#9: Post by jmc »

There are 2 models of the Aurora head. The earlier one, which I have, with no HX. And the later model which does. Both heads look the same ( beautiful in real life IMHO ).



The later one is loved by those who have them as VERY temperature stable. The height of the head is 250mm
and the length of the lever is 300mm from the pivot point - overall length is 470mm
Perhaps Brugnetti can still make the later model under contract or licence you to manufacture them - or even sell you the moulds if they still have them.

On a different note I really think that be a success as commercial /club as well as a home machine the machine should be auto fill for the boiler. Both home and commercial owners will be afraid of blowing elements if it is not.

If you are in Melbourne any time soon and want to have a play with the Aurora or Cremina, pm me

John
John

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timo888

#10: Post by timo888 »

jmc wrote:There are 2 models of the Aurora head. The earlier one, which I have, with no HX. And the later model which does. Both heads look the same ( beautiful in real life IMHO ).

<image>
John,
That Aurora is a beautiful machine. May I ask its countertop dimensions?