Randy G. wrote: greater number of degrees of rotation for any given adjustment in comparison to a flat-burr grinder.

Assuming that the linkage from the adjustment knob to the burr adjustment mechanism is the same, this is true.

But even with that assumption, the burrs still move in a linear fashion. They do not jump. It is an analog, not a digital, movement.

It may be a matter of convenience, and as Jim (aerojrp) says, a matter of mechanical "fineness" but the gap is traversed continuously. So if you are adroit, you can land on any distance.

The better question is, "What is the taste consequence of a different grind path?"

aerojrp wrote:ok, I can't begin to comment on which produce better results, but I couldn't resist posting since the math in this post is a mess!!!

I'm an engineer who designs products similar to these, so I'm very familiar with the math part. In reality, the equation is the effective distance between the cutting edges is vertical distance x sin(90-angle). For example, at 45 degrees, for 1mm of vertical adjustment, the burr gap in a conical system will separate by .707mm. As the angle gets steeper, the separation gets less, so at 60 degrees, 1mm vertical means .5mm in gap change. The flat burrs separate exactly by the vertical adjustment, which would be 1mm. What this means is that for the same thread pitch, the same rotation change on a conical system would make a smaller gap change that that on a flat system. While theoretically both systems could make the same adjustment in distance, it is easier to be precise with the conical one and the conical one would be less succeptable to slop in the parts or the locking system.

You should have resisted.

Here's a picture of the lower conical burr in a Versalab (from an old thread):

Please note the orientation of the shaft's long axis.

Here's another picture with the upper conical burr installed on the shaft:


According to your algorithm, if the angle is 60deg*, 10 miles of vertical adjustment = 5 miles of gap change. Either you're not writing what you mean, or those burrs must be made of something very special.

As a general rule, the term cos(theta) is preferred to sin(90-angle).

And my math is a mess.

BDL

*You failed to specify exactly what is angled at 60 degrees, but I assume you refer to the conical burrs' vertex angle.

I don't follow your reasoning, but for sake of clarification, allow me to interject.

boar_d_laze wrote:Here's a picture of the lower conical burr in a Versalab...

The Versalab M3 uses a hybrid burr design with the conical burr set used for bean breaking and then a flat burr set for the final grinding. When you adjust a M3's grind setting, you're tweaking the distance between the flat burrs. The math in the last few pages is confusing enough without changing from a conical burr grinder (Compak K10, Mazzer Robur) to a hybrid burr grinder (Versalab M3).

Jim refers to the hybrid design as DRM in Grinder burr types explained. Below is a photo of the Versalab M3's burr stack:


From Versalab M3 Grinder

Dan,

It doesn't matter if the burrs in the picture are used for actual grinding or not. The purpose of using the illustration was showing the relationship of a burr set along a vertical axis.

The actual math is not complicated. The bad math is complicated because it's nonsensical.

Rich

Math aside.

If you go about a large conical like the k10, for example, and don't want to single dose every time what is the method of controlling the dosing accurately with hopper full of beans? Is there an accurate timer or something else that does the job? In my case I would like to control my doses between, say, 14-19g depending on the coffee.

I like the convenience of my varios timer, but the grind adjustment system is killing me. I am wondering if I could get the same kind of convenience from a large conical like the k10?

dpiette wrote:The better question is, "What is the taste consequence of a different grind path?"

In terms of "path," are you referring to conical vs. flat? I have experienced what others have reported. In terms of my Rocky vs. my Kony, that the flat burrs give a more, and excuse the term, generic coffee taste. The chocolate comes through more readily, but the more subtle notes of fruit and acidity get muted. When the Kony first arrived I changed my blend a little, using more Brazil and less of the "exotic' origins (African and Asian primarily). As time went by and I got better at roasting and started enjoying some of the more varietal notes, I slowly changed back. I have not used any Brazil in my last few roasts and am leaning more heavily towards blends with a majority of the beans from Africa mainly. I am not talking about lip-puckering acidity sourness, but pleasing notes of lemon and orange with a touch of sweetness.

This is certainly a matter of taste, but I also prefer Macallan to Glenlivet preferring the fruiter, sweeter taste of the former over the smokier of the later.

And a final argument for conical burrs as I previously diagrammed, it is like having a throttle pedal with five inches of travel doing the same thing that one with 1/2 inch of travel does. Which would you prefer? And that's a rhetorical question because I grow tired of this.

boar_d_laze wrote:The actual math is not complicated.

Probably not. It's hard to believe that I once understood calculus, but I have old college notebooks in my own handwriting to prove it. Anyway, I reproduced what Randy described with two magazines on a table and a ruler. That is, for a delta X of vertical movement of one magazine, the distance between their two parallel edges increases/decreases by less than X if they're at an acute angle to the direction of movement, unlike when the two edges are perpendicular to the direction of the movement.

When you lower the conical burrs, a particular point on the movable burr moves by the same amount as the flat burr for the same vertical adjustment, but with the conical burr, there is a sliding motion so that that particular point is now aligned with a different, lower part on the lower burr which explains why the change in gap is less with conical than with a flat burr.

Maybe these will help... but honestly now, the math isn't so complicated after all. Randy's pictures should have been clear enough.

Jim

aerojrp wrote:Maybe these will help... but honestly now, the math isn't so complicated after all. Randy's pictures should have been clear enough.

After being corrected so many times as I have been in this discussion, I had to check all the user names as I certain that my wife was participating in the thread.

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