Pino wrote: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).

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

AndyS wrote: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

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.

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.

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/

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.

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

lennoncs wrote: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.

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.