by AssafL on Sun Jan 03, 2010 6:50 pm The combination is certainly capable of pulling great espresso shots when using proper barista technique. Unfortunately, I wasn't there. Pulls turned blonde very early and naked portafilter revealed the reason - pulls always channeled towards the back, indicating uneven distribution. Clearly my distribution technique was not good enough. Both David Schomer's and Stockfleth's techniques did not improve the results. Of all the different distribution techniques discussed here, the only one that resulted in even pours was the Weiss method. Odd.
Clearly the ground coffee from the Mazzer was not evenly distributed. Perhaps the cause was static, perhaps humidity, perhaps it is the type of coffee I purchase - I do not know. But fluffing the grinds with a chopstick or shaking them in a mason jar did the trick. I had a solution, but it was not as convenient as using the Mazzer as originally intended.
So I decided I would not give up on the Mazzer and would try to find a way to fluff the grinds automatically. As I see it, there are two main problems with this grinder:
1. Coffee grinds seems to be sorted and sometimes even clumped.
2. Position of the chute is off center of basket (for 58mm portafilters - it might be okay for smaller portafilters).
Tackling Problem 1 - Fluffing the Grind:
Design goals were:
1. Fluffy grinds, style Versalab grinder
2. Automatic
3. Stable and easy to clean
I tried various contraptions: i. A spinning tie wrap proved that a solution was possible, and that this wasn't it. ii. A spinning plastic k beater proved too dangerous after shaking itself loose and flying across the kitchen. iii. grating with a shaker attached proved adapt at collecting grinds but not letting them through. iv. Spinning wiper (like the Versalab) worked but was too finicky and tended to scratch the chute. v. Spinning grating worked - and worked great!
Starting with the results, the following is a picture of the grinds after the spinning grating. The evenness of the grind is felt during tamping:
Distribution still off center and should be improved. "La Maccina Fluffinata" is nearly here.
The motor for the Fluffinator was purchased first. It is a US made Globe 12VDC model 405A391 acquired NOS (new old stock) at surplus electronics store Halted Specialties Electronics in Santa Clara, CA for less than $2. The motor shaft diameter was measured at 5/32" and the rest of the parts were all selected for this diameter.
At the heart of the Fluffinator is a spinning grid of zinc (source: Home Depot - used for vents) cut into a circle 58mm wide. It is held on a 5cm long, 5/32" stainless steel shaft by two collars and two NSF approved silicon O-rings (source: McMaster-Carr, see BOM below). The advantage of using a grid is that unlike a wiper, it is rather balanced at low RPM. This is important since the shaft is supported only at the top by the chute cover - it is rather long and any imbalance will set it swinging.
In the picture below it is clear where the grid edges hit the sliding coffee, sending it swirling around the chute. Coffee grinds start as a donut shape pile in bottom of portafilter and eventually pile up to make an off-center pile.
The shaft is connected to the motor by a flexible coupler (source: McMaster-Carr) which reduces vibration greatly. The motor is centered by the top lid of the chute. The center of the lid was conveniently pre-marked by the plastic injection mold, and then drilling and using a taper/reamer to widen the hole for the motor rest. A center punch and micrometer were used to position the screw holes which were then drilled.
Remember to use a reamer or large drill to remove any plastic burrs, or they will end up in your coffee. (o-ring on motor shaft was intended to prevent coffee from getting into motor, which proved not really necessary)
The flexible coupling is the only delicate component in the contraption. It is indeed flexible, and giving it a tug will send it into plastic deformation. One nice aspect of it, is that it is 19$ at McMaster Carr. It is not a once in a lifetime find in a junk lot so it can be replaced within 24 hours.
A picture of "La Maccina Fluffinata" installed on the Mazzer:
BOM (bill of materials):
McMaster-Carr
1 9861T109 Alum Helical Beam Set-Screw Shaft Coupling 5/32" X 5/32" Bore, 1/2" Length, 3/8" OD $19.95
1 1263K145 Miniature 316 Stainless Steel Drive Shaft 5/32" OD, 5" Length $5.50
2 9946K3 Aluminum Set Screw Shaft Collar 5/32" Bore, 7/16" Outside Diameter, 1/4" Width $5.78
1 Pack 9396K136 Silicone O-Ring AS568A Dash Number 105, Packs of 100 $8.56
Halted Specialties
Motor Globe 405A391 12VDC: 1.95$
Home Depot
Building exhaust - or perhaps a concrete mold (source of the zinc grating): 4$ at home depot.
Total with shipping ~ 60$
Electrical set up:
For safety, use a UL approved wall wart and a switch.
Want more automation? Well, you can indeed electrocute yourself, or grind a finger away, or inhale stuff known or unknown to the state of California or Europe or believed by someone to cause or not cause a disease or a cancer or brain problems. And you can probably grind your warranty away... So you are on your own. (But if you insist here are some hints: I connected the motor to the timer circuitry located in the base of the grinder. I did not connect the motor in parallel to the relay as the transistor used to trigger the grind relay was not adequately spec'ed for the motor draw current. Instead I hooked a miniature 12V transformer *potted! and shrink wrapped!* in parallel to the grind motor. This then operates the DC motor.)
Tackling Problem 2 - Chute Alignment:
The chute seems to have been designed for a Type A grinder (buttons on top of chute). A 58mm portafilter, resting nearly against the body of the grinder is indeed centered under the chute. For a Type B grinder, this doesn't work since the grind activation button is behind the portafilter and pushes the portafilter out about a centimeter.
The button is a spring loaded cam that pushes a lever microswitch located inside the grinder. Adding a few washers (about 5.8mm worth) should do the trick:
If you are wondering, use an 8mm spanner for the internal lock nut, and a 13mm spanner for the button side. To get to it, you'll need to remove the power switch and the entire switch/trimmer assembly (2 screws below).
Installed, it looks like this:
It is important to verify that the electrical switch still functions correctly: if the button is pressed because of the washers, your grinder will run until the motor burns out. Twist, pull and push the button to verify the switch will always return to the 'off' state.
And the results - centered and fluffy. And a very nice pull indeed!
Happy tinkering!
