Small flat vs. large flat vs. conical burrs: Taste differences? - Page 3

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cpreston
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#21: Post by cpreston »

boar_d_laze wrote: Your analysis is WAY off, so is Glenn's, and so is the verbal representation I quoted immediately above. Consequently the calculations do not apply.
I believe Glenn's analysis is in fact correct, per basic trigonometry.

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boar_d_laze

#22: Post by boar_d_laze replying to cpreston »

With respect, no. And for this situation we don't need trigonometry. All we need is a frikkin' ruler.

You have two identical cones, 1 and 2, oriented along a single axis, aleph, facing the same direction, so that:
  • The inner face of 1 appears to be a mirror image of the outer face of 2; and
  • 1's outer point P is separated from 2's inner point Q by distance x.
Also, for any point alpha on cone 1, there is a respective point beta on cone 2, such that alpha is separated by beta by distance x.

A is moved along aleph towards B by distance y, such that the new distance from P to Q is z.

z = x-y. QED.

If you're telling me that z is not x-y (for P, Q AND for all points alpha and beta) you've got some 'splainin' to do. For heaven's sake get some paper, cut out two identical triangles, orient them along an axis so that their apexes face the same direction and their respective sides are parallel, and move one towards the other along the axis on your desk. Now, tell me again that z is not x-y.

Don't just tell me what you believe. Sadly, math is not a poll. Explain how and why the distance between any alpha (including P) and its respective beta (including Q) would vary according to the square root of anything.

Moral of the story: Mind your Ps and Qs.

BDL
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dpiette

#23: Post by dpiette »

I went back to try and figure out what question was being asked/answered.

Not as simple as it may sound, but by my interpretation, it is does a conical burr set react to a stepless adjustment differently than a flat burr set?

If the adjustment is truly stepless, then it doesn't matter a whit about the characteristics of the burrs.

Think of Zeno's Paradox. You have to go through every conceivable spacing to get from coarse to fine, so it all has to do with how delicate your fingers are in adjusting the dial that controls the grind.

Unless, of course, I am missing the question. In which case I will almost certainly fall back on the Mean Value Theorem, since it is the basis of all calculus.
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aerojrp

#24: Post by aerojrp »

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.

What is interesting, is that the flat burr sets each have large opposing angles. That means the space is very wide at the center, and pinches together to the finest setting at a single point. I don't have a set of conical burrs to look at, but I think the passage starts wide and then gets gradually narrower until the smallest part is at the outlet. This means the grind is slowly getting finer and finer up to the set final distance. I would think that this design, would be less succeptable to having larger chunks slip through the final pinch point.

As to grinding surface area, yes, there is a lot more on the conical set, and it's effective result is magnified by the completely different way beans get pinched to the final set point.

What all this means to the coffee, I don't know. I just hope you all don't get me convinced that I now need a conical grinder... the wife would kill me!

Jim

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Randy G.

#25: Post by Randy G. »

dpiette wrote:If the adjustment is truly stepless, then it doesn't matter a whit about the characteristics of the burrs..
Yes it does matter. If the thread pitch is the same for both, for a given grind-particle size change, the conical should have a wider range of adjustment lever movement. if anyone has the thread pitch for the Rocky as well as the Kony, that would be a good data point from which to compare.. maybe... not that I want to throw another handful of sand into the thread(s). :wink: see what I did there?
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Terranova

#26: Post by Terranova »

Looking at the grind path of 2 different sets of 83mm (Mazzer Robur vs Mazzer Stark) I still doubt that the conical grind path is any bigger.

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dpiette

#27: Post by dpiette »

Randy G. wrote:If the thread pitch is the same for both, for a given grind-particle size change, the conical should have a wider range of adjustment lever movement.
It is not quantum.

There is not a minimum amount you can twist a thread, unlike the stepped adjustments.

You just have to be very careful.

Now, of course, it would be easier if you would have some sort of a step down mechanism so you can use one adjustment for the coarse work and another for the fine work, but if you are careful you should be able to make ANY adjustment.

Most stepless grinders I have used make it very easy to make tiny adjustments, and hard to make large adjustments. Probably to give you the control you want.
you can't win,
you can't break even,
you have to play.
-the three laws of thermodynamics

aerojrp

#28: Post by aerojrp »

dpiette wrote:It is not quantum.

There is not a minimum amount you can twist a thread, unlike the stepped adjustments.

You just have to be very careful.
But, mechanically, it does really matter. You can be as careful as you want to be, but the slop in the motor shaft (bearing play) or adjusting thread will start to fight you. Heck, the act of locking the system could even change the adjustment. A system that is less susceptible to distance deviations will allow you to achieve and keep a more accurate setting. Play and distortion are real. I can show you pages and pages of calculations that manufacturers go through to minimize its effect, but it's real. Perhaps this is why conicals tend to need fewer adjustments???

The path is still different enough that I wonder what its effect is. The conical with it's gradually narrowing of the passage where the grains leave the cutter and go right to the chute, or the flat with a single narrow cutting area and than 2 flat non-cutting planes that might polish the grains some.

Jim

cpreston
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#29: Post by cpreston »

boar_d_laze wrote:With respect, no. And for this situation we don't need trigonometry. All we need is a frikkin' ruler.
BDL
FWIW, Mgrayson and aerojp are in fact correct in their posts above regarding the trig. Though I doubt you are convinced.

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Randy G.

#30: Post by Randy G. »

ENOUGH with the math already. Here's a graphical representation without the numbers that should get my point across:

Image

At the top we have "A" and "B" which is a set of flat burrs.
At the bottom we have "C" and "D" which is a set of conical burrs.

In examples "B" and "D" I have moved one burr a given distance. Burrs moves in a vertical plane, so in each example I have moved the burr closer to the other, vertically. The green arrow "1" indicates that portion of the diagram showing that the burrs have moved the same exact distance. I created this image in Photoshop and moved each of the burrs (the lines), vertically, using the keyboard and using the same number of keystrokes each time.

Note the Blue arrows in A, B, C, and D. These indicate the distance between the burrs before and after the movement. I then copied those four arrows and placed them in a separate layer for comparison. Those comparisons are shown at "2" and "3."

In example "2" you can clearly see that the change in the distance between the burrs is quite great- the difference being equal to the distance the top line had moved.

In example "3," even though the burrs was moved EXACTLY the same amount as in Example "B," the change in the distance between the "conical" burrs is far less in comparison to the flat burrs.

If we assume that the thread pitch is the same in the grinders represented here in this lesson, the same number of degrees of movement of the adjustment lever in a flat burr and a conical burr grinder will result is two very different results in terms of the change in grind particle size.

It is true that in conical burrs the entire grinding path is not at such an angle and so it is not such a matter of black and white, but even the "finishing" area of the conical burrs is still at an angle. To some extent, in flat burrs, the initial grinding area is cut at an angle, albeit a shallow one, but the final grinding faces are parallel and perpendicular to the adjustment direction.

Even taking that into consideration, the fact that a quality conical grinder (at least in my limited experience) provides the user with a greater number of degrees of rotation for any given adjustment in comparison to a flat-burr grinder.
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