A few pictures of the Zerowatt CA 310

[hbuchtel]

I finally got my hands on my Italian Ebay'd Zerowatt and Caravel, here they are together-



And the inside-



It is a single boiler, with two thermostats for brewing and steaming. I'm staying in hotels at the moment so I haven't been able to do much with them, but in cleaning out the Zerowatt's boiler it seems there is a lot of black crud inside- if it is old coffee that would indicate a similar piston to the MiniGaggia, one that allows coffee grounds to be sucked back into the boiler.

More later when I get it cleaned up!

Henry

[happytamper]

They look super cool. Enjoy them.

[timo888]

I especially like the form-factor of the Zerowatt, Henry. Two very different machines. The Caravel makes a tiny shot, and didn't you say the Z has a gigantic basket?
Regards
Timo

[hbuchtel]

Thanks for the encouragement guys!

The Zerowatt is producing great espresso. I've been using the single basket exclusively, which in spite of its ~60mm ID only holds about 10g of coffee.

I'm a bit surprised it is tasting so good, as the spring seems very weak and there is no crema. I'm hoping to replace it when I have time.

Henry

[valrie4631]

Hello hbuchtel,

I would like to buy a ZeroWatt CA310 like yours. Can you tell me how much does it cost ?

Thank you
Best regards

Valrie

[hbuchtel]

Hello hbuchtel,

I would like to buy a ZeroWatt CA310 like yours. Can you tell me how much does it cost ?

Thank you
Best regards

Valrie

Hello Valrie, I bought mine second-hand on ebay Italy and paid about 70 Euros. Since then I've seen no mention of this model anywhere on the web so I don't know what your chances are of getting another one are . . . but it is quite similar to the MiniGaggia (except for the steaming) which is more common. Or you can wait a while and get "The Beast."

Good luck in any case,

Henry

[hbuchtel]

I opened the Zerowatt up for some overdue cleaning/spring replacement/finding-out-how-it-works, here are a few pictures of the more interesting details-

First, the 'piston-chamber'



As you can see it is not a closed chamber but rather a sheath or collar that extends about 2.5cm into the boiler. The hole that you can see is one of four through which water flows when the piston is raised. At both ends the inner wall flares outward, presumedly to make the piston's travel easier. At the lower mouth the ID is 49~50mm.

Next the piston/spring/lever assembly



The spring is flat on both ends and is held between the piston and the ceiling of the boiler. The piston shaft is about 9cm long, 5cm of which is contained within a hollow tube extending down from the top of the boiler. (see below)



The piston is brass, screws off of its shaft, and has two gaskets 'facing' in opposite directions. It is about 48~49mm in diameter.



What a fun evening!

Henry

[mogogear]

Wow , that sure is a short cylinder!

[timo888]

Wow , that sure is a short cylinder!

You know what Lincoln is reported to have said in reply to the question, How long should a man's legs be?

Regards
Timo

[mogogear]

"Longer than his lever?"

[hbuchtel]

"Longer than his lever?"

"in proportion to his waist" ?

Henry

[mogogear]

I heard you giggle all the way over here!

[timo888]

"Long enough to reach the ground."

[hbuchtel]

I finally got around to getting a new spring made for the Zerowatt to replace the old one. First, a picture of the two springs-

(L: new R: old)

First off, the guy at the factory office said the stainless steel they had was not as good quality as the original Zerowatt spring. (I'm not sure how the quality relates to the springyness)

When I picked up the new one I was surprised to see that the top and bottom had not been filed off like on the original. They guy said he couldn't do it because grinding it flat would cause it to heat up and expand. I think this is a problem... I can see and feel that the shaft of the piston is rubbing one side of its ?carrier? and I think this is due to the spring not being perfectly straight.

Here are the dimensions of the two springs-

Height: 107mm (new) 87mm (old)
OD of Wire: 6.0mm (new) 5.5 (old)
OD of Coil: 470mm (new) 465mm (old)
ID of Coil: 360mm (new) 350mm (old)
Weight: 171.5g (new) 135.5g (old)

Using this formula I calculated the pressure that each spring produces.

There's a much simpler method, measure the distance the lever handle travels, and the volume of water dispensed.

Say, for simplicity, 45 mL water, and 22.5 cm of travel, then the "tube" of water being pushed on the lever side of an imaginary hydraulic pump is 2 cm-square. A bar is roughly 1 Kg per cm-square, so you'll need 2*9 or 18 Kg.

So here are my calculations (please check for errors!)

The piston is diameter is just short of 50mm and travels 20mm with a lever travel of 305mm.

1. Volume of original-
V=pi*r2*h
V=3.14*625*20
V=39,250 cubic mm

2. Radius (sq.) of "imaginary"
r2=V / pi / h
r2=39,250 / 3.14 / 305
r2=40.98mm

3. Area of "imaginary"
a=pi*r2
a=3.14*40.98
a=128.7 sq mm
or
a=1.287 sq cm

Ok, I put the machine on a scale and measured how many kilograms of pressure it took to hold the lever at its lowest position. (for each spring)

Old=5kg
New=7kg

4. Bar produced by each spring-
a (in cm2) * ? =7kg
or
5kg / 1.287cm2=3.9 bar
7kg / 1.287cm2=5.4 bar

Old=3.9 bar
New=5.4 bar

This only shows the maximum pressure, next I will take measurements with the lever at different positions to show how much pressure is produced at the beginning and end of the shot.

No I haven't tried making any espresso yet... My grinder doesn't do courser grinds very well (too many fines) but I'll be trying it out in the next couple days!

Henry

[mogogear]

My head is spinning from that calculation!

I don't see why you cant get someone to grind the ends taking care not to take the "temper" out of the s/s!

[hbuchtel]

My head is spinning from that calculation!

heh heh it took me &*$&* ages to finish! Haven't done anything like that for ... about 10 years?

I don't see why you cant get someone to grind the ends taking care not to take the "temper" out of the s/s!

Do you think that would work? I don't know anything about steel, temper, grinding etc...

Henry

[mogogear]

That is how the other spring was done. Someone can chime in - it is either let it cool down slowly between brief grinding or grind it all at once and then plunge into water- Espressme? Are you out there - Richard and others know the simple answer to this riddle