Hey Sean,

I don't have an M3, but I've been staring at the pics for the last several days...

Looking at the burr shaft, I was a little disturbed to see no lower bearing. That shaft is hanging way out there. The bearing housing (where I assume the bearing is, anyway) looks mighty thin too. Even if the upper pulley is hollow and the bearing is in there too, it's still not much room for two bearings, and they certainly can't be separated much. That doesn't leave much resistance to radial loads at the business end of the shaft. Even if they are good bearings with a mighty preload. Plus, those bearings appear to be housed in aluminium, making things even more flexible.

As a side note, the SJ uses two $3 bearings (size 6202, IIRC, shielded, not sealed), but they are 10" apart. They can't support much axial load, but there doesn't appear to be much...

One might ask, yeah, but when does the shaft experience side loads? (at least I asked that....)
One significant time that the case came to mind. When the last bean goes thru, there isn't (necessarily) an even distribution of grinds around the burr, side loads could be significant.

Also, does the shaft move or flex if you tug on it?

Anyway, just a thought....

The proof of the pudding, however, is "in the cup", as they say. And it seems to be doing quite well in that respect.

How long have people had these in use? I know you got yours recently Abe. How about Jim and Andy, how long have you had them?

ciao

lino

lennoncs wrote:I defer to the experts on grain size for optimum extraction to give an exact size of the grains that we want (any time now Jim

Not something most of us are up to measuring: here's a frequently reproduced graph (fair use, I hope) from Illy & Vianni showing grind particle distributions:



The horizontal scale shows particle diameters, The vertical scale shows percentages. The graphs show the number of particles, and the percentages of total volume and surface area at each particle diameter.

The graph's empiric distributions have been successfully simulated by finite element simulations of the grinding of hexagonal cells of simulated cellulose. These tend to break into fragments of single cells (fines) as well as particles consisting of multiple complete cells

The grinding chapter also addresses the underlying design of the M3 explicitly:

1: Grinding takes place in two phases - a crushing phase breaking particles to 1mm sizes, and a shearing phase reducing them to grinds.

2: "Cheap" home and coffee shop grinders use a single set of burr-wheels with unevenly spaced cutting teeth. "Industrial" grinders use either two rollers in sequence, or conical followed by flat burrs to do each grinding phase separately.

If you look at the mini's burrs, you'll see the "cheap" arrangement of widely spaced crushing burrs on the inside of the wheel, and finely spaced shearing burrs on the outside:



Abe's pic of the M3 flat burrs on page 1, shows they have evenly and finely spaced "shear only" cutters.

3: Industrial grinding equipment always finishes with a homogenization step that thoroughly unclumps and mixes the grinds.

I never read the chapter thoroughly before. My take is that the commercial burr grinders we respect are somewhere between substandard and barely adequate by the industrial criteria used by Signor Petracco, the author of the chapter. In contrast, the M3 has each of the three grind phases -- crushing, shearing and homogenization -- covered by an explicit design element -- the conical burrs, the flat burrs, and the sweeper-funnel arrangement.

Perhaps John Bicht read this chapter a bit more thoroughly than we all did.

Thanks for the info on the grinding, very enlightening indeed!

One of the customers I used to visit on a regular basis is a spice grinding concern...I almost wish they would have robot problems so I could check out their cryo-grinders for spices with my new-found interest in grinding. I remember relating to one of the plant guys how nice I found my Mazzer and his only comment was that coffee was another universe away from their grinding. I would like to talk to him more about that comment.

I see the majority in volume is particles of .019" followed by .0013" if I read the chart correctly, do you suspect this distribution holds true for the M3?

Sean

Hi Lino,

I probably need to temper my penchant for precision in some things but I do agree about the bearing spacing...the shaft might not get enough loads in operation to deflect much...I just dont know.
this is most likely a dead issue...

I remember making a cabinet years ago for my girlfriend out of wood...not a succsessful venture if you apply the same standards to wood that you do metal...the first change in humidity and she couldn't even pry it open!


Sean

You should look at pharmaceutical grinders.

I talked to an engineer working on these products. He said that (in his opinion) the current commercial espresso grinders are what was industry standard for his industry around 50 years ago.

Basically, he laughed at the design and described it as "one step up from big heavy rocks and a mule."

lennoncs wrote:I see the majority in volume is particles of .019" followed by .0013" if I read the chart correctly, do you suspect this distribution holds true for he M3?

Yes, it holds true for all grinders and according to Marino Petracco, who also wrote the brewing and tasting chapters (7 & 8 ), the bimodal distribution is required to get proper packing of a perculation mass (perculation is coffee scien-tese for any brewing process, including espresso, that sends water through the grounds). Think about packing with uniform spheres -- can't be done. However, several people have done measurements of the dust from different grinders, and the good and new ones produce less than old or poor ones.

A simple way of doing this, for those who have 1/10 gram scales, was proposed by Steve Ackerman. Brew the same weight of coffee ground for FP (using a pinch test), on several grinders. After you're done, run the grounds through a Swiss gold, then a paper filter. Dry and weigh the grounds in the paper to compare grinders dust output. This is very rough, however, according to Petracco, using a set of gradated precision sieves doesn't work repeatably for coffee, and laser diffractometry needs to be used to generate graphs like the one reproduced above.

I find my collection of tools required by this hobby frightening enough already, and don't want to convert to a lab. So I'll leave the grinds measuring, rough with paper, or smooth with lasers, up to someone else. I know what my tongue tells me, the M3 produces less dust than (my) mini; bank on it.

lennoncs wrote: P.S. Looks like a really nice unit, I am going to have to crash Abe's place to rip his apart

Anytime Sean, and if you do it within the next couple of weeks, I'll let you break apart the new espresso machine I'm testing too .

I love the meter solution. I'm going to look into one that hopefully will fit nicely on the M3. There are quite a few out there. I think an analog dial will go better with the design style of the machine, it is 18 century English style. But a digital meter would be more functional.

lino wrote:Even if the upper pulley is hollow and the bearing is in there too, it's still not much room for two bearings, and they certainly can't be separated much....
...does the shaft move or flex if you tug on it?

I haven't disassembled it, but I was told by John from Versalab that there are two bearing in there.

lino wrote:How long have people had these in use? I know you got yours recently Abe. How about Jim and Andy, how long have you had them?

8 days. A long time, no?

Abe Carmeli wrote:I'll let you break apart the new espresso machine I'm testing too .

Hope it's a good one.

another_jim wrote: I don't want to give anything away until I've racked up about 20 to 30 comparative shots over the next week, but I'd like you to also try some milk drink comparisons if you normally make these.

OK, will do.