Versalab M3 Grinder - Page 10

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Abe Carmeli (original poster)
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#91: Post by Abe Carmeli (original poster) »

The latest on the dial stop consistency problem: Versalab believes they have resolved it. They are replacing the lock knob with an upgraded one. According to John's measurement, it will deliver dial stop consistency within less than a micron. That should be more than enough for a very precise dial. I should be getting it early next week and will report my results.
Abe Carmeli

Abe Carmeli (original poster)
Team HB

#92: Post by Abe Carmeli (original poster) »

Day 7

I've talked about the grinder's even distribution, and today I took some photos to illustrate how it all comes together when pulling a shot.

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I promise, no more naked shots

The above image was taken 20 seconds into the shot using a ridgeless double basket and 14.5 grams coffee. This is just about as perfect as a shot can get. The jet is perfectly centered, note how dark the extraction is so close to the end of the shot, how evenly the stripping is, not a hint of channeling, and best of all - this is not your standard triple basket 21 grams naked shot. it is only 14.5 grams of coffee in a double basket. That one was yummy.

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In the cup - They just don't get much prettier than this one

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My afternoon shot - like molten chocolate

All shots were pulled on the Brewtus.
Abe Carmeli

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default

#93: Post by default »

wow! it looks very reddish. what coffee is that?

the white cup is beautiful, what brand is that?

i'm not sure whether someone has asked about popcorn effect on this grinder, any comment please?

Abe Carmeli (original poster)
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#94: Post by Abe Carmeli (original poster) »

default wrote:wow! it looks very reddish. what coffee is that?
It is my home roasted blend: 40 % Daterra Reserve, 30 % Sulawesi 30 % Harrar. Roasted to Full City, after 3 days of rest.
the white cup is beautiful, what brand is that?
It is Danesi. It is shaped like a ball with the top cut off
I'm not sure whether someone has asked about popcorn effect on this grinder, any comment please?
The only way I can verify the existence of the popcorn affect is in the cup and sometimes in the extraction. I haven't detected it with the M3 grinder, but it still could be there.
Abe Carmeli

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another_jim
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#95: Post by another_jim »

The M3 has arrived at its new temporary home, a person whose tasting and grinder tweaking acumen I trust far more than my own. With luck, we'll get a more authoritative tasting report than I can provide.

I completed my taste tests using SOs. Although my subjective impression was that the M3 stood out more in this area than with regular espresso blends, my scores were completely in-line with those posted on my taste report.

And that brings me to the subject of the post.

I took the grinder apart prior to shipping it. I wanted to check how much grinds it retained, and what their condition was. The inspection confirmed Versalab's claims about grounds retention -- I swept the lot into a container, and it was less than what stays behind in my doser after I sweep it out, maybe 3 to 4 beans worth of ground coffee. It was hard to tell from their condition how cool the grinder is running. However, the grounds seemed brown and dry, rather than the black, oily double shot's worth of compressed grinds I find when cleaning the Mini's chamber.

As I was doing this, I chanced to look at the way the conical burrs were spaced. First I looked at the upper burrs with the lower ones removed:

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Hmm, I thought, the outer conical burr is really far back. So I mounted the lower (inner) conical burr, and could still see a lot of daylight.

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If you look at the left side, you'll see the amount of clearance. In fact, you can toss through the coffee beans ...

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... and they emerge completely unscathed. A little testing confirmed it, the conical burrs are too widely spaced to affect the beans if the flat burr is not in place.

On the other hand, trying to grind coffee without the inner conical mounted turns into a failure too, the beans simply won't enter the flat burr set, which is too narrowly spaced to admit a whole bean. I tried to examined the beans mid-grind (with the grinder properly assembled) trying to disassemble it so the beans being ground remained in position. I made a mess of it and wasn't able to get good photos. It does appear that the conical burrs augur the beans down against the flat burr entrance, where they get crushed against one another, and the metal walls, into pebble size.

Schomer has written a lot about conical grinding and its wonders, especially in connection with this burr-set. Most of this appears to be complete nonsense. Basically, grinders force the beans into a more and more constricted space, so they break into finer and finer particles. The burrs don't do much cutting, they are merely paddles that criss-cross like scissors, pushing the bean fragments into the tighter space.

Here's a schematic cross-section for flat burrs:

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The typical burr grinder has three angles where the bean breaking, coarse and fine grinding respectively occur. As the burrs are put together, these angles create a progressively constricted space the beans are forced into. At the outer diameter, the grindstones are perfectly parallel for the final grind to a powder.

Now, armed with this mental schema, lets look at the DRM/M3 burrs and the Mini Mazzer burrs (standing in for all flat burr configurations):

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Looking at the Mini burrs, you can see the three zones very clearly, in the breaking zone (marked by green shading) the burrs are widely spaced. as one transitions to the coarse grind zone (blue shading), the burrs become tightly spaced, creating a narrow channel for the grinds, the final fine grind stage (red shading) is a very narrow outer perimeter.

Now over to the DRM flat burr. The fine grind area is equally narrow. But there's no bean breaking area, and the coarse grind area is huge in comparison to the mini's. So where's the green bean breaking area? That's where the conical burrs come in. They force the beans into the flat burrs, breaking them as they enter.

In other words, the only thing the conical burrs do on this grinder is allow the flat burr to have a much enlarged coarse grinding area. Whether and how this contributes to an improved grind is anyone's guess.

A final thing caught my eye that may be relevant to the discussion of particle distribution in espresso grinds. On the DRM grinder, the burrs are not cut all the way to the perimeter; instead there are little channels that allow some coarse particles to escape. On the Mini, the burr channels are cut all the way through, also giving an escape path for some coarse particles (see enlarged sections). I'm wondering if grinder manufacturers can "tune" their grindstones by varying the size of these escape channels, in order to affect particle distribution?

lennoncs

#96: Post by lennoncs »

very interesting post...you have my undivided attention.

nice work!


cheers
Sean

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another_jim
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#97: Post by another_jim »

lennoncs wrote:very interesting post...you have my undivided attention.
In that case ... I wasn't planning on continuing the grinder 101, but here's a look at a pure conical burrs grinder. This is the Trespade burr set from the Lux, Pavoni, Innova home grinders and the lowest end commercial model from Iberital. The burrs are quite tiny, but the configuration of the grinder is commercial, albeit cheap. BTW, at around $150 to $200, these grinders are the true entry level for serious espresso grinding -- loud, messy, slow, but grind quality equal to the mini's.

Here's the grind chamber from the Pavoni PGC, my travel grinder, with the static outer burr removed.

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As you see the layout is conventional, including the mass of grinds not spat out by the paddles.

Here is the outer burr assembly:

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The mount is hard plastic instead of brass, and the mounting threads aren't tight, but the burr is well attached by two screws. The assembly is driven by a worm gear driving the teeth shown on the outside. Despite the poor threads, this gives very good grind adjustability.

Now to the business side. the burrs are slightly out of focus, but (starting from the bottom of the picture) the bean breaking, coarse grinding and fine grinding areas are apparent. Note that the outer burr is roughly tube shaped, whereas the inner burr is conical, so one has the same constricting space as with the flat burr.

The grinding areas on the inner burr are a lot clearer:

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Again note the changing surface angles as one moves from the bean breaking to coarse to fine grinding zones. One of the reasons conical burr grinders may be better than flats is also apparent here -- this is a tiny burr set, yet the coarse grinding area is larger than the mini's (although not as large as the M3's. On a true commercial conical like the Conik or robur, these areas must be huge.

It also becomes obvious that the DRM/M3 conical is missing the coarse and fine grinding zones, and only has the augur-like bean breaking section.

When one puts the burrs together, one finds the same flush contact along the fine grinding zone as in the flat burr grinders:

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OK, that's it for grinder 101. I'm not sure if this tells one which grinder is best; but it does let one at least see what's going on with the grind stones.

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another_jim
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#98: Post by another_jim »

OK, one more 101.

How about less then steller grinders:

Scoot on over to long time altie Ken Wilson's page on burr sets, which includes all the cheapies.

http://www.kwilson.fsnet.co.uk/burrs.htm

The low end flat burr grinders seem to missing anything but the bean breaking part. The Solis conicals don't have a fine grind section. The Zassenhaus burrs on the other hand look perfectly legit -- I suppose motorizing one of these could save someone some money compared to going with that 1K plus commercial conical.

Abe Carmeli (original poster)
Team HB

#99: Post by Abe Carmeli (original poster) »

Jim,

Thanks for the great post. I was sure the conicals do more than just funnel the beans against the flats, and that was a real 101 for me. One thing we did not discuss is how wear and tear plays a role here. It will dull the flats, I'm sure, but the conicals on the M3 seem to be immune to wear and tear as they really do very little work. What's the lifespan on the flats? I need to ask John that question.
Abe Carmeli

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barry

#100: Post by barry »

another_jim wrote:The Zassenhaus burrs on the other hand look perfectly legit -- I suppose motorizing one of these could save someone some money compared to going with that 1K plus commercial conical.
i have seen that setup in some cupping labs... a zass type hand grinder with a pulley on the upper shaft, connected by belt to a small motor mounted on the bench.