Small flat vs. large flat vs. conical burrs: Taste differences? - Page 2

Grinders are one of the keys to exceptional espresso. Discuss them here.
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Randy G.

#11: Post by Randy G. »

pacificmanitou wrote:Don't all mazzers use the same adjuster though? So the adjustability isn't exclusive to conicals
it is not just being stepless. It is a matter of geometry (I think):
Image
Repeating myself one again, I was an art major, so this may not be mathematically accurate (or even correct). X = adjustment distance and direction of movement. Y = distance (or change is distance) between burrs..

In the first (top) example, the burrs being parallel and the adjustment movement perpendicular to the grinding faces, the vertical movement of the top burr would be equal to the change in gap between them.

In the bottom example I go to an extreme. The burrs' grinding faces are once again parallel as in the top example, but the adjustment movement is in the same plane as the grinding faces. Here, the distance between the burrs remains constant (unchanged) regardless as to how far the adjustable burr is moved.

The middle example represents conical burrs. Now, my math may be off, but I tried to show burrs with faces that are at a 45 degree angle. Here I am assuming that the distance between the burrs changes at a rate that is less then the movement of the adjustable burr. it may take something like a logarithm to be accurate and that is beyond my mathematical or geometrical abilities. one of the engineers maybe can assist as to the ratio of movement to adjustment distance...?

Oh oh.. he is assuming! :shock: My foot's in it now... A friendly pull or push would be appreciated.
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GlennV

#12: Post by GlennV »

You're doing fine.

I think you meant Y=X/2 in your second picture. It's actually Y=X/sqrt(2) for 45 degree burrs. However, the large conicals are closer to 60 degrees, in which case you would indeed get Y=X/2. For my Rossi MC, a whole rotation of the burr carrier corresponds to 1mm of vertical movement, but a change of 0.5mm in burr spacing.

pacificmanitou

#13: Post by pacificmanitou »

Oy, I see what you mean now. My math is far inferior to yours it would seem, but that makes sense.
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Randy G.

#14: Post by Randy G. » replying to pacificmanitou »

Glenn V. - Thanks for the mathematical correction. I knew I had the concept correct but the computation was beyond me. Well, my spelling sucks so let's call it a rub. :wink:
I taught math to 6th-8th grade students (introductory algebra, basic geometry, fractions, decimals, metric system and such) so I excel at the basic math, but that's about all.

I never thought about that benefit of the conical burrs until after the Kony arrived and I started dialing it in over the first few weeks. After so many years with the Rocky it took a bit of time to get my head around the concept.
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FotonDrv

#15: Post by FotonDrv »

Randy G. wrote: I never thought about that benefit of the conical burrs until after the Kony arrived and I started dialing it in over the first few weeks. After so many years with the Rocky it took a bit of time to get my head around the concept.
From a Rocky to a Kony is a mega leap! I use my Kony as a single doser, weighed beans in and single shot out and with RDT it works. It does however take a serious puff of air down the clear acrylic tube to clear it.


RDT really helps the Versalab as well as a bean popper cap.
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walshman

#16: Post by walshman »

FotonDrv wrote: It does however take a serious puff of air down the clear acrylic tube.
I know someone that uses a rubber lens hood as a hopper. When the grinder stops he slams his hand down on the hood collapsing it sending a gush of air down the grinders chute clearing out anything left in the chute.

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FotonDrv

#17: Post by FotonDrv » replying to walshman »

Good idea and worth a try! Thanks for that 8)
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boar_d_laze

#18: Post by boar_d_laze »

The middle example represents conical burrs. Now, my math may be off, but I tried to show burrs with faces that are at a 45 degree angle. Here I am assuming that the distance between the burrs changes at a rate that is less then the movement of the adjustable burr. it may take something like a logarithm to be accurate and that is beyond my mathematical or geometrical abilities. one of the engineers maybe can assist as to the ratio of movement to adjustment distance...?
Whoa!

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.

Referring to a conical burr set: When the upper and lower burrs are stacked vertically, with faces parallel, and the adjustment is made only along the vertical axis, then x = y, just as in the flat burr-set example.

Think of it this way. If the upper and lower burrs in separate conical and flat burr grinders are each separated by 2mm, and the upper burr in each grinder lowered 1mm towards the bottom burr -- isn't it intuitively obvious that the resulting separation would be 1mm for both the flat and conical burr sets? (If not, what difficulties do you imagine?)

The only ways the ratio of movement to adjustment distance could be anything other than 1:1 would be if the movement were not entirely along the vertical axis -- for instance, if tilt were introduced -- which would mean a poorly functioning grinder.

As far as grinders are concerned, the principle geometric difference between conical and flat burr sets is the greater surface area of conical burrs compared to the surface area for flat burrs of the same diameter. For a variety of reasons, greater area is generally conceded to be superior. But let me add, that burr surface area is only one of many important grinder aspects.

So... how do you make the comparison? The surface area of a flat is pi x r squared. The surface area of a cone is pi x r x s, where s is the distance (along the surface of the burr) from the cone's center to its edge. (If you think of a triangle as a flat projection of a cone, you can also think of s as the equivalent of the hypotenuse of a right triangle.) And if you know the angle of the cone (angle opposite the radius) and its radius (and the diameter is always given), you can determine s with ordinary trig.

Hope this helps,
BDL
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drgary
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#19: Post by drgary »

vinhster wrote:I currently have a Mazzer Major side by side with a Compak K10 PB. I've only had the Compak for a few weeks, so I haven't learned its quirks yet...

The reason I got curious about a conical after owning the Major for some time was because most of my shots had a prevalent bitter note. It was present with nearly every coffee I tried, and I wasn't able to make it go away through changes in dose, grind, or anything else. I'd have a good shot from a cafe, where they were pulling from a Robur, most commonly, and buy some beans to try at home. There, I would get shots that have a distinct bitterness to them that wasn't as strong in the cafe. One cafe I frequent uses a Amfin Super Caimano, and I noticed a fairly strong bitter note from their espresso as well.
I want to dispel this before others believe a flat burr grinder will cause bitterness. I have a Mazzer and a Rio Super Jolly grinder. Neither has a tendency to cause bitter shots compared to my Orphan Espresso Pharos, a titan conical grinder. Something else was going wrong there.
Gary
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FotonDrv

#20: Post by FotonDrv » replying to drgary »

When I had my Rocky I could on occasion get a good shot, not consistent but it did happen, so it is not the grinder.

I am with you, something else is going on, like temps, tamps and timing?
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