5: Generation 2 Steam Heated Group Head - La Pavoni Lever Espresso Machine
Вставка
- Опубліковано 15 вер 2024
- Join me online here:
/ lapavonienthusiastsgroup
An exploration of the OnShape CAD model of the La Pavoni Espresso Machine to see how the generation 2 group head draws water directly from the boiler for brewing coffee, which may be a bit too hot for some.
More here:
• La Pavoni Lever Espres...
as a person who has spent some time making cad models before, your skill and attention to detail are amazing!
Wow, thank you!
Wow... I really thought this version of La Pavoni was the best one until seeing this video. That's my dream machine torn to shreds... Otoh, it will help me gauge more carefully the right pressure for a shot. I hate to admit it but I may have been scalding my shots even when I was under the impression I was managing the temperature.
Stelios,
It may be that the generation 2 is indeed the best. I'm just sharing my thoughts. There is always so much more to learn!
@@JohnMichaelHauck I seem to be going round in circles. I thought I was scalding my shots so I was not letting the water reach boiling temperature. Then I started purging the air in the boiler again (which made the water reach boiling temperature) and discovered my shots became much better. I think in order to reach consistent results, there's no escaping the need to follow a systematic procedure and to acquire the right tools. So eventually I will have to find a way to gauge the water temperature inside the head as a first step. Elsewhere on yt people told me it's brand coffee which is the reason for not getting crema. Then I remembered I was getting more crema using the same coffee with a cheap bottom of the range espresso maker. There are just too many variables (I have counted at least 7 so far) and a systematic approach is simply not feasible time-wise.
I have GEN 2 and GEN 3. Like Gen 2 more:
- Love the steam heating. 7-8 minutes and everything is up the temperature. No need to waste water flushing the group head.
- No sleeve means less isolation, measuring the group head temp gives more precise water temp.
- No trapped air problem (Spongy lever)
It's fun having more than one machine to experience the difference in designs. I've heard many people prefer the generation 2 over the 3. It is a rare bird, however, that prefers generation 1. Enjoy your journey!
Great video thanks for putting this together. I seem to get a lot of steam and over pressure even at .7bar for my gen 2 so trying to diagnose that.
Nice explanation.
Hi John. I have just bought a gen 3 la Pavoni. A technique I have been using to bring the group up to temperature is to do 5 or 6 half raises of the lever. Not high enough to allow water to exit. I am assuming I am introducing steam to the group above the piston but I don’t really understand how that is happening. It would be great to see that explained.
Rod,
Thanks for the suggestion on another video about temperature. It is good that you clarified which generation machine you are talking about because they really are very different. My thoughts on raising the lever half way is that you are pushing the cooler water above the piston back through siphon tube into the boiler. Then when you lower the lever, hotter water re-enters the group head. This will then indeed raise the group head temperature.
Understand that your procedure cannot remove any air trapped in the group head. I believe that raising the lever to allow steam, water and most importantly air to escape is critical to pulling a good first shot without a spongy pull.
In any case, to collaborate with people that have these and alternative views, I would suggest plugging in to this friendly group: facebook.com/groups/lapavonienthusiastsgroup
Hi, I’ve just inherited a 1976 La Pavoni, what is Francesco’s website please.
Congratulations!
www.francescoceccarelli.eu/
These are also a useful resources:
www.home-barista.com/levers/
John Hauck Thanks, I’m not on social media so the website is great. And, I’m very excited to have it, I need to do some minor maintenance- a little surface rust under the rubber skirt, before I fire it up.
nice got it
So the steam in the boiler is actually going through 2 tubes?
First tube is the one to preheat the group head/portafilter and the 2nd one is for the steam to escape into the air?
Adam, just to be clear, we are talking about the Generation 2 group head only. See video "2: Four Generations of Group Heads" (ua-cam.com/video/ViNrag4lYJg/v-deo.html) for a comparison with the other group heads.
So, to try and respond to your question, there is only one "tube" - the copper siphon tube. One end of the tube connects to the holes in the group head that lead to the brew chamber (below the piston) when the piston is raised. The other end of the tube is submerged in the boiler water. When the piston is raised completely, the pressure in the boiler forces water up through the tube and into the brew chamber. When the piston is lowered, the water in the tube falls back down to the level of water in the boiler (like an open straw in a glass). The top of the group head and the top of the boiler are filled with steam (no air).
Steam can transfer through the upper hole (not connected to the copper tube) between the boiler and the top of the group head. When the piston is lowered, steam is drawn in because more space is opened up by the piston going down. Vice-versa when raising the piston.
When steam cools, it condenses to liquid water. Liquid water takes a lot less room than steam. Because of this contraction, the pressure inside the boiler decreases. The heating element is connected to a pressure sensor. When the pressure is too low in the boiler, the heating element turns on, converting some water back to steam (and increasing the pressure).
Did I even get close to addressing your thoughts?
@@JohnMichaelHauck my bad I should have clarified but I just meant the second tube as the steam wand itself,
That all makes sense though very helpful, I did not realize there is a pressure sensor included, does this mean when it gets too hot it also stops heating?
And is this in all the models? Or only more recent ones
@@adambromley6972, Yes!
Peek at video #9 in this list ua-cam.com/play/PLPX9KWMNFMwNk_aBK7plrFBF1VJx0OMVw.html
There you can see when La Pavoni went from a high/low switch to a simple on/off switch with what is called a "pressurestat". The pressurestat is mounted to the bottom of the boiler. If the pressure is too low, the switch turns the heating element on. Then it turns it off when the pressure is too high. Over the years La Pavoni would turn on a light when it is heating, or turn off a light when it is heating - go figure which is best! Before the pressurestat introduction, if the boiler pressure was too high, the valve on the top would open more and let even more steam out. These early machines would constantly hiss. Very alive! The new machines only hiss a bit to let out air (not steam) when first heating up. Then the valve only serves as a safety release, should the pressurestat get stuck on.
@@JohnMichaelHauck I’m learning so much thanks a bunch :)
What I am really trying to understand is how does the "sleeve" design of the gen 3 impact the water temperature/stability? What effects does it have overall? Thanks for any help!
May I recommend taking a peek at video #13 "Flow & Temperature Simulation".
ua-cam.com/video/eQuEZDY6Awo/v-deo.html
The first minute and a half of the video shows how the generation 3 sleeve design cools the water from the boiler before it enters the brew water chamber. (I'm using "brew water chamber" to mean the water directly under the piston and above the coffee grounds, that will actually be part of the shot.) The generation 2 group head's siphon tube flows directly into the brew water chamber. The quick conclusion is that if the output of the the siphon tube in both generations is 120C, then the generation 3 brew water chamber will consist of cooler water than the generation 2. However, (as it's good not to draw quick conclusions) other factors are at play. The starting temperature of the group heads (the metal) can have a big effect on the final water temperature in the brew chamber.
I could work on a simulation of generations 1 and 2 too, if there is interest.
@@JohnMichaelHauck Simulations YES PLEASE!!!! Also that video is amazing! Thanks!
One question that raises however, is the although it might be cooler on initial runs, what does the overall temperature stability look like when comparing the designs. It's hard to tell if gen 2 has more thermal mass and how that would come into play. It looks like since the water is taking a longer route through the grouphead in gen 3 that it would be cooler, however does that mean that it would STAY cooler over several shots, or would the temperature stability have more variation due to the longer route?
Or I could be completely misunderstanding all of this...
You are not misunderstanding this. You are going down a rabbit hole. Welcome!
Take a close look at the generation 2 group head. It is, as some call it, "steam heated". That means it not heated just by the water that enters the brew water chamber, but mainly by steam directly from the boiler. I believe this plays a big role in why a generation 2 group head is generally hotter than a generation 3 group head. It was helpful to reacquaint myself to how steam works - well - at a high level at least. As steam enters the generation 2 group head, it will condense into water as it cools (and the group head heats up). As it condenses to water, it occupies less space. This then opens the door for more steam to enter the group head, to heat it up more. This is the cycle of steam heating the group head. Excess water in the group head (above the piston) drains back into the boiler to be heated back into steam again.
As for the generation 3 group head, it does get hotter on successive shots, but not as much as a generation 2.
As you are wondering, yes, thermal mass plays a large part in this, but I don't have anything quantitative to offer. IT is interesting that the generation 4 group head was designed with even more thermal mass, but the same inner workings as the generation 3 group head.
@@JohnMichaelHauck That seems to be my practical experience as well. When I installed the Bong isolater in my gen2. The first shot was so cold that I now make it a habit to run some water through the grouphead so that the shot itself isn't cold. The subsequent shot that I pull is definitely less burnt tasting than without it.
But I wonder how narrowing down the variable to just having a water cooled grouphead with a sleeve (gen 3), vs having a water cooled grouphead that pours directly into the brew chamber (gen 2)
@@Wyrdrock in other words, more simulations, including the Bong Isolator. You are heaping on, you know. :)