So it's been raining spring-lever machines here at the Lab - well, what would you expect in Seattle - it should snow Super-Automatics?
This is a pretty remarkable commercial 58mm single group machine which has to be close to 30 years old. Imported by the 'Termozona' company of Hartford, Connecticut, it looks to use either a Victoria Arduino or Faema grouphead, has a 5-litre boiler, a massive Sirai pressurestat, and a couple of very heavy-duty soft-close steam valves - note the Marzocco-style pivoting steam wand which has a formed ball-end tensioned against its brass fitting by a spring.
Another shot from the right side - the blessed machine looks like it was brand new inside - the boiler is shiny, there is no corrosion anywhere, and all of the pipes and fittings just gleam.
There are lots of nifty little engineering touches, the inside of the case is insulated with about an inch of pink fiberglass batting - not nasty asbestos - which appears to be remarkably effective and makes working on the machine much more pleasant than having to fight insulation glued to the boiler, there is an overflow line from the inlet valve to the drip tray, if the water supply burps the overflow is directed to the drip tray which has its own outlet tube.
What makes this machine unique, and very interesting to me, is that it uses a Heat Exchanger loop from the water input through the grouphead. My first reaction was "Weird, why would anyone want to use an HX loop on a Lever machine?" After all, the whole idea behind a massive lever group hung out in the air is for it to cool the too-hot boiler water down to an acceptable shot-making range.
Which idea works well, as long as the boiler and grouphead system are in thermodynamic equilibrium, but as any Pavoni Europiccola owner can easily demonstrate, after several consecutive shots it's pretty easy to exceed the capacity of the group to radiate off additional excess heat.
So how does a very clever designer deal with this problem - simple, they pass a small amount of the cool input water through an HX tube in the top of the boiler, and then route it to a water-jacket surrounding the group via a drilled passageway and several small ports above the piston which are exposed when the lever is lowered into its pre-infusion position.
The thinking behind this arrangement is so stupidly clever that it almost makes my brain hurt just following the logic, which I believe goes something like this:
"For the first shot so as not to 'shock' the group with cold water, the HX loop will be at the same temperature as the boiler to keep the group stable."
"For each suceeding shot, the HX water flow will become progressively colder since the HX loop's heat transfer rate is deliberately limited to match the grouphead's thermal transfer rate. Hence, the more shots you pull, the more the grouphead is cooled by the HX loop and thermal stability is acheived"
As a final piece of efficiency, the output of the HX loop isn't to the drain tray. No, as the lever raises the piston for the next shot, it also forces the HX water back along a passage in the grouphead mount into the boiler. Cute, not only is the group held temperature stable, as long as you're just pulling shots and not Americanos, the boiler remains very close to its original level, since the HX water neatly replaces the 2-3oz used per shot.
Using a Scace device mounted in a bottomless Astoria portafilter I was able to tune the machine to show consistent 203-204 degree F shot temperatures with the pressurestat set for 1.2 Bar, and acceptable flow rates. The shot temperature profile was essentially flat for the first 20-23 seconds and then rather rapidly declined to 198-199F after the lever had reached its stop.
This profile is consistent with what I've always been told about the big lever machines, that you need to pull the cup as soon as the lever bottoms out, letting any additional liquid spill into the drain tray - "The shot ends when the lever stops."
The spooky thing is that I was able to pull something like 15 consecutive shots about as quickly as I could manipulate the lever before there was any appreciable change in the water temperature - which went down to 195 F in a hurry as it became apparent I'd exceeded the capacity of the 110V - 1200 Watt boiler element to heat water.
I have no idea how many consecutive shots you could pull with a 220V element, but it would be an exhaustingly large number - far more than I and all of my few friends could drink ....
But enough propellor-head chatter, "How did it taste, Jim?"
In a word, "Fabulous - 17 gram ristrettos
were rich, chewy, and utterly smooth - with no harsh, sour, or bitter notes, and cappuccinos
made with 2oz pours and 4 oz of perfectly microfoamed milk where among the best I've ever had from any machine.
My thanks the Mr Perry, who brought his new baby to the Lab, along with the Scace device and an impressive Versalab grinder and patiently waited while I muttered and talked to myself.
He's had a few days to live with the beast now, perhaps he'll be so good as to post some follow-up impressions?
BTW - information about this machine is very difficult to come by - I've seen an older two-group on Ebay, and a two-group of about the same vintage here in Seattle, but if any of the European members recognise this machine - we'd love to know more.