Time to retire vibe and rotary pumps?

[Abe Carmeli]

A convincing experiment to determine the effects of vibration would be a rotary pump versus an air pressure-driven water chamber. I recall someone saying the new Techno had such a beast, but I didn't check it out at the SCAA conference.

Yeah, I was the one who posted it. It is not a standard feature of the new Techno. A small company from Taiwan The Formosa Coffee Company used a Techno to illustrate the effect of an air pump. They were looking for distributors for their air pump and concept. The crema coming out of that Techno was Versalab crema. The blend they used had no Robusta in it. I attributed it to the air pump, as a default hypothesis since the only other variance on that machine was PID. As I pointed out on a previous thread, that experiment leads me to believe that pump pressure technology is worth exploring. It appears that the flat (as opposed to vibrating) pressure of an air pump may make a difference. Another idea would be a pressure profile programmed into the pump by the Barista. 1 bar during pre-infusion, slow ramp up thereafter, a hump, a descending profile etc. It is only hypothetical at this stage but worth exploring.

[espressobsessed]

Excellent!

This is one area where machines are potentially lacking. I mean, temp stability is great, but what is the next phase?

The problem with LMs remain with the procon and the so-called 'ramp-up'. Then there is the dispersion screen design. The water line terminates at a screw with three holes in it - where the water flows out, a mere few mms above the screen. The potential* problem with this is an unnatural extraction. The shop I worked at used a Rancilio Z11 hydraulic machine: that is, a larger piston pushed down on the smaller brew water chamber. The beauty of the brew water chamber is the volume would rush in from the 18 liter boiler, into that space, essentially creating what should be a relatively stable (ie: not line fed) mass of water. Of course, the Zed isn't a perfect machine, and requires a lot of work, but it pulled a really nice shot, that, IMHO, was technically superior to the offerings of the local shops running synesso or LM.

[another_jim]

The conventional wisdom has always been that vibrations aid crema formation, for instance, that vibe pumps create more crema than rotary ones. It's something I didn't notice when comparing the vibe and rotary Jjuniors side by side. It could be an effect of the slower ramp up of vibe pumps when the gicleur is large (like in LMs). The Juniors have tiny gicleurs and long dwell times, so that may have been a factor.

I think there is something to the idea that no vibration at all produces superior taste. It would be nice to side by side the tricked out Reneka against a conventional rotary one.

[Abe Carmeli]

I think there is something to the idea that no vibration at all produces superior taste. It would be nice to side by side the tricked out Reneka against a conventional rotary one.

Another advantage of their air pump design is that it draws water out of the Brew Boiler during a shot, unlike all other pumps that push water into the brew boiler. It adds to temp stability. At idle time, it refills the boiler. I'm going to shoot an Email to that guy and see if they have a model we can test in the U.S.

[HB]

Good point, Abe. Then you could also use a smaller boiler for prosumer units since incoming water temperatures aren't an issue. Now that I think about, shouldn't an air driven pump behave a lot like a commercial spring lever machine w.r.t. pressure?



(Elektra La Taravisium Leva; also see larger back photo on CoffeeGeek)

And the tricked out modern rendition (which earns my vote as most lust-worthy espresso machine on the planet):


(Image courtesy of Kees van der Westen)

The BGA booth was supposed to have a lever machine from Kees at the SCAA conference, but it got held up in shipping. That was a big disappointment. I wonder why commercial lever machines haven't made a comeback? Maybe worries over occupational overuse... ?

[espressobsessed]

Dan,

I was very disappointed that there was no lever at the show. If the internals performance was comparable to a mirage, I would have seriously considered one for opening my own shop.

Sigh....

-jimmy

[lino]

I'm not sure I understand perfectly how the air pressure systems work...

But, if they are a chamber that contains water and pressurized air together, then the pressure is used to push the water out the bottom thru the coffee...

Then a significant factor in taste, crema generation, etc. would be that the brew water would have a *much* higher dissolved air content than your typical boiler setup, which tends to remove dissolved gasses.

9 BAR of air over water and you're gonna get some pretty good "nitrogenation" (among others), then during extraction, that would tend to come out. I'm not an expert on coffee extraction, but I'd bet my left.... uh..leg, that there would be a significant effect on flavor and feel between the two methods....


ciao

lino

[Pino]

Hi,

My first thought when reading this thread was the http://www.illy.com/Illy_En/Company/History.htm illetta .
I remember reading this in Illy's first book on Espresso 12 years ago.
This method uses compressed air. I asked myself then why this method never became popular.

Arthur

[AndyS]

Then a significant factor in taste, crema generation, etc. would be that the brew water would have a *much* higher dissolved air content than your typical boiler setup, which tends to remove dissolved gasses.

9 BAR of air over water and you're gonna get some pretty good "nitrogenation" (among others), then during extraction, that would tend to come out. I'm not an expert on coffee extraction, but I'd bet my left.... uh..leg, that there would be a significant effect on flavor and feel between the two methods...

The solubility of air in water is only about 1/10th as much at 200F compared to the solubility at room temp. So your...uh...leg may or not be safe.

Have you had kids yet?

[Pino]

In winemaking nitrogen does not dissolve in wine. CO2 and O2 do. CO2 is not a problem but O2 is, because of oxidation. I would think that the ratio of air to water is so small that it would not impact flavour. Any further opinions are welcome.

Cheers,
Arthur

[AndyS]

My first thought when reading this thread was the http://www.illy.com/Illy_En/Company/History.htm illetta .
I remember reading this in Illy's first book on Espresso 12 years ago.
This method uses compressed air. I asked myself then why this method never became popular.

I assume it never became popular because:
1. Development of espresso technology was driven mainly by commercial concerns, not by a geek's obsession with achieving the last 1% of espresso quality
2. Compressed air is impractical for commercial use, because you have to stop every x number of shots to refill and reheat the boiler (just like the Versalab is impractical for commercial use).

[Pino]

I assume it never became popular because:
1. Development of espresso technology was driven mainly by commercial concerns, not by a geek's obsession with achieving the last 1% of espresso quality
2. Compressed air is impractical for commercial use, because you have to stop every x number of shots to refill and reheat the boiler (just like the Versalab is impractical for commercial use).

Hummm, interesting I had not looked at Ernesto Illy as a Geek. Although if he had put his time, energy, passion and scientific approach into the development of espresso machines as he did into coffee who knows how that would have influenced espresso machine technology.
Compressed air would be a bit of a nuisance having to lug a cylinder once in a while. Although, the usage of air would be low.
Regards, Arthur

[lino]

The solubility of air in water is only about 1/10th as much at 200F compared to the solubility at room temp. So your...uh...leg may or not be safe.

Have you had kids yet?

Hey Andy,
In an effort to save my "leg" ...
You make an excellent point (that I missed) regarding the solubility at higher temps, but...
Beer, as an example, is typically carbonated with only 12-30 psi (IIRC) of CO2 (the pressurization varies widely among beers), we're talking about the 140-150 psi ball park for espresso, about 10x that of beer...

However, also of note is that nitrogen is about 80 times less soluable in water than CO2.

Anyway, my point was not that the air pressure style coffee would come out as fizzy as a coke, but that it would have more disolved gasses than the current method and that I think that would affect the taste, quite possibly in a good way.

The short answer is that I do have a child, so if I lose my "leg" all is not lost

[DanBollinger]

In a commercial setting, compressed air powered machines would be detrimental if for no other reason than the noise of an air compressor, even if sound insulated. It's not like coffee shops have basements or can easily mount the compressor outside. Using pressurized tanks would be excessively costly and changing out tanks is not an easy task.

I recall that there were machines that there used to be water main pressure to make a shot using what is called a pressure amplifier. Basically, a large diameter piston and cylinder is mechanically linked to a small diameter one, which forces water into the PF.

Lever spring machines are self-contained and have achieved romantic status. Spring powered machines develop higher pressure at the beginning of the shot and much less near the end. I've always wonder what effect, if any, this has on the shot.

[espressobsessed]

Re: the dissolved water theory

Do we know what the internals of the machine actually are?

It is possible the machine operates more like a lever machine, and less like a pump machine, in that the water chamber/lever design is maintained, and instead, it is air pressure driving the piston, and not a spring. The rancilio z hydraulic machines were similar, but used water instead.

Of course, I'm speculating, but since we're all talking theoretically, one more monkey joining the pile wouldn't hurt.

[malachi]

Once again I raise my suggestion that people evaluate the linear hydraulic pumps for this purpose.

For samples...

http://www.vindum.com/
http://www.michael-smith-engineers.co.uk/

[wookie]

There are air-impeller pumps where the air drives only one side of the impeller. Water being pumped on the other side of the impeller would be pretty much free of vibration and completely untouched by the pressurized air. Might not be inexpensive, though.

[lennoncs]

You need a device like this:
it is a voltage controlled pressure regulator

0V=0 Psi
10V=Max out
+- .2% FS

They do a very nice job of closed loop pressure control of an air over hydraulic system

Cheers,
Sean

[Abe Carmeli]

You need a device like this:
it is a voltage controlled pressure regulator

Sean,

How do you do that Dude? Only yesterday you sent me pictures of your piston pump running on a completely different motor . It must suck being you. That's a very nice & compact setup for an air pressure engine.

[Abe Carmeli]

Out of the blue, I got an email from the Formosa Coffee company. It is those guys who fitted the Techno with an air pump in Seattle. They want to meet me in NY in September. I'll keep you posted.