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Technically and Mechanically  - Conical vs Flat Burrs
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Discussions > Espresso > Grinders -... > Technically and...  
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JonR10
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JonR10
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Posted Sun Jul 5, 2009, 8:51am
Subject: Re: Technically and Mechanically  - Conical vs Flat Burrs
 

cappuccinoboy Said:

...first and most important on same size OD (outside diameter) and same number of rotations conical have a much lower peripheral speed = less heat generated, "softer" contact with the bean ...

Posted July 5, 2009 link

While it seems you have learned a bit about burrs (apparently what is generally purported by machine manufacturers), here you are technically incorrect about the physics of rotation. The relationship is determined by a simple law: Two objects with the same outside diameter and rotational velocity will have the same peripheral speed:    

            r x w = v         Where r is radius, w is angular velocity, and v is peripheral speed.  

But there is no change in heat transfer to the grounds due to burr rotational velocity.  In home use these professional grinders run for very brief periods, not long enough to build any heat.  Experimental measurements have shown that the Mazzer Major at 1600 RPM doesn't heat the grounds any more than the Mazzer Robur at 500 RPM.  

It is true that the larger grinding surface of conicals can allow a conical burr to grind the same amount per unit time at lower rotational speed in many cases.  For example, the Macap 68mm conical grinds a regular double shot a tad faster at 400 rpm than the Mazzer Super Jolly 64mm flat burr at 1600 RPM.  Conicals can also be more forgiving in terms of adjustment.

But the Mahlkönig has 65mm flat burrs and grinds more than twice as fast as the Macap 68mm conical (albiet the Mahlkönig runs at 1600 RPM). In this case the difference in grinding speeds between the Mahlkönig  and Super Jolly can be attributed to the burr design having more aggressive cutting angles, and if you were to install the new Titanium alloy burrs available for the Super Jolly (with similarly aggressive cutting angles) it would grind as fast as the Macap conical or the Mahlkönig K30.  


cappuccinoboy Said:

...Noise I believe is strictly a matter of housing because when you "impact" a bean logics say that at higher speed you produce more noise, and this could mean that a conical is supposed to be quieter, and that does not always happen in real life, but you can always verify that by placing your noisy grinder into a cardboard box......

Posted July 5, 2009 link

You're correct that noise is mainly due to the build specifics.  Noise can be attributed to a number of things, but not speed of burr rotation.

My fastest-motor grinder is also by far the quietest. It's not the housing per se, but rather seems related to burr geometry and motor mounting.  For example, the less expensive conical grinders are some of the loudest available...sounding like an airplane jet engine but the German flat burr grinder has rubberized motor mounts to isolate the motor assembly and it is amazingly quiet

 
Jon Rosenthal
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cappuccinoboy
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Posted Sun Jul 5, 2009, 11:05am
Subject: Re: Technically and Mechanically  - Conical vs Flat Burrs
 

JonR10 Said:

While it seems you have learned a bit about burrs (apparently what is generally purported by machine manufacturers), here you are technically incorrect about the physics of rotation. The relationship is determined by a simple law: Two objects with the same outside diameter and rotational velocity will have the same peripheral speed:    

            r x w = v         Where r is radius, w is angular velocity, and v is peripheral speed.  
...........................
You're correct that noise is mainly due to the build specifics.  Noise can be attributed to a number of things, but not speed of burr rotation.

My fastest-motor grinder is also by far the quietest. It's not the housing per se, but rather seems related to burr geometry and motor mounting.  For example, the less expensive conical grinders are some of the loudest available...sounding like an airplane jet engine but the German flat burr grinder has rubberized motor mounts to isolate the motor assembly and it is amazingly quiet

Posted July 5, 2009 link

jon you should know better : flat burrs are individually  precision machined and both have the same OD, conical burrs are machined in set of two where the outside diameter refers to the upper burr, while the lower burr (the one actually rotating inside the upper one) is much smaller.
I guess (but tomorrow I will be precise because I am actually going to calibrate), that in a 63mm conical the lower burr diam. is no more than 44-45, in a 47mm the lower burr is no more than 32-33, and in a 38mm the lower can be 23-24 : if you put in the right facts I bet even your formula will give a much lower peripheral speed of conical burr.....
You are right about what you call German grinder : the day Italian manufacturers do realize that they can get higher price for "better" grinder, they will come out with something comparable,... and it is the sole way to go since most of the world can build a cheaper piece of equipment (of any kind), and the Know how we have can only be used to build better .......
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JonR10
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JonR10
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Posted Sun Jul 5, 2009, 11:37am
Subject: Re: Technically and Mechanically  - Conical vs Flat Burrs
 

cappuccinoboy Said:

jon you should know better......

Posted July 5, 2009 link

Actually, I do know better already  :-)  
The formula given is generic and absolutely correct in the strictest sense.  

In a way, I was just poking fun at your words.  It sometimes seems like you quote advertising literature from manufacturers like scientific facts when in general such information is not supported (or maybe only partially true).  

It's true that the higher-end conical grinders are generally made to run at slower RPM and therefore have slower tangential speed at the point where the burr meets the bean (you called this peripheral speed).  


cappuccinoboy Said:

the day Italian manufacturers do realize that they can get higher price for "better" grinder, they will come out with something comparable,... and it is the sole way to go since most of the world can build a cheaper piece of equipment (of any kind), and the Know how we have can only be used to build better .......

Posted July 5, 2009 link

I guess I don't understand your point here.  Are you saying the Italians don't build expensive grinders?  
Have you seen THIS ONE and THIS ONE, and what about THIS ONE??

 
Jon Rosenthal
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IMAWriter
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Posted Sun Jul 5, 2009, 12:14pm
Subject: Re: Technically and Mechanically  - Conical vs Flat Burrs
 

Cap boy.....methinks you might want to gracefully withdraw from THIS battle! LOL
Jon is an engineer, but in true R10 fashion is giving you a gentle pat on the posterior, but at the same time questioning your scientific method.
besides, this conical/v flat burr thing is to me, all about taste anyway.
By the way, you list yourself as a professional, yet your gear appears to be pod oriented.
Whoops...don't want to get into THAT discussion.
However, as a manual grinder owner, I do agree with you that for whatever reason, a somewhat miniature in stature conical in my manual does pretty much as superior a job as does a Mazzer mini, close to an SJ.

 
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cappuccinoboy
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Posted Sun Jul 5, 2009, 12:22pm
Subject: Re: Technically and Mechanically  - Conical vs Flat Burrs
 

JonR10 Said:

Actually, I do know better already  :-)  
The formula given is generic and absolutely correct in the strictest sense.  
In a way, I was just poking fun at your words.  It sometimes seems like you quote advertising literature from manufacturers like scientific facts when in general such information is not supported (or maybe only partially true).  
It's true that the higher-end conical grinders are generally made to run at slower RPM and therefore have slower tangential speed at the point where the burr meets the bean (you called this peripheral speed).  
I guess I don't understand your point here.  Are you saying the Italians don't build expensive grinders?  
Have you seen THIS ONE and THIS ONE, and what about THIS ONE??

Posted July 5, 2009 link

*You insist on poking fun at my words (but beware of boomerangs..)... at same RPM tangential speed is lower because lower burr in conical is of much smaller diameter:
I do not read much manufacturers advertising literature (BTW you did not answer my post answering yours in :Fully automatics....), but in Naples they have a say stating that every mother finds beautifull her ugly son .....(I can say but not write in actual Neapolitan words)
*I was only referring to the fact that I understand, although I could be wrong, that the Malkhonig is the most expensive grinder out there :the three examples that you give me kind of support what I said.
*With ref. to noise in a grinder you get the mechanical noise of motor and the noise of beans actually beeing ground : motor noise can be dampened (like the Germans did), noise of beans is just a metter of sound transmission (body shape and size)
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JonR10
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JonR10
Joined: 26 Apr 2004
Posts: 10,376
Location: Houston, Texas
Expertise: I love coffee

Espresso: E61 Legend, Livietta,...
Grinder: Robur, B-Vario-W
Vac Pot: Hario Tabletop, Yama...
Drip: Technivorm
Roaster: 1-lb US Roaster, Behmor 1600
Posted Sun Jul 5, 2009, 12:44pm
Subject: Re: Technically and Mechanically  - Conical vs Flat Burrs
 

cappuccinoboy Said:

...at same RPM tangential speed is lower because lower burr in conical is of much smaller diameter

Posted July 5, 2009 link

This is a re-statement of the formula, of course it's true.


cappuccinoboy Said:

*I was only referring to the fact that I understand, although I could be wrong, that the Malkhonig is the most expensive grinder out there :the three examples that you give me kind of support what I said.

Posted July 5, 2009 link

Two of the three were roughly the same price at the Mahlkonig, and the Mazzer Robur-E is 50% higher.  


cappuccinoboy Said:

*With ref. to noise in a grinder you get the mechanical noise of motor and the noise of beans actually beeing ground : motor noise can be dampened (like the Germans did), noise of beans is just a metter of sound transmission (body shape and size)

Posted July 5, 2009 link

I disagree heartily.  If you'd seen the evidence and personally tested and compared grinder designs then you'd most likely not make such an assertion.  The science of vibration and noise is very complicated

The Germans clearly did some engineering work to make the Mahlkonig so quiet, it's not just a matter of dampening motor noise (electric motors run VERY quietly themselves unless something is horribly wrong mechanically)  

Pietro - perhaps you claim not to read manufacturer's information but as a dealer of these machines I dare to say that you have probably read and re-read such material so much that now it's become much of the basis of your arguments...

 
Jon Rosenthal
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JasonBrandtLewis
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Posted Sun Jul 5, 2009, 1:09pm
Subject: Re: Technically and Mechanically  - Conical vs Flat Burrs
 

The Mahlkönig K30 ES is available from a US-based vendor for $2,150.00, and is available in 110v (North American "home," as opposed to "commercial," electric current).  Please note, I have a Mahlkönig K30 Vario, the stepless version of the above grinder, in 110v.

The Elektra Nino is available from the same American vendor for $2,995, but only in 220v (European) current.

The Mazzer Robur is also available from the same vendor for $2,195 -- in a 110v model.  But the Robur 220v model is $2,321.80.

All three of these Italian grinders are more expensive than the Mahlkönig as I am checking prices on the afternoon of 5 July 2009.

Meanwhile, the Dalla Corte DC Standard Espresso Grinder comes in at $3,690.00, the Dalla Corte DCII Gsc Espresso Grinder is available in the US for $5,590.00, and let's not forget the La Marzocco Swift which seems positively cheap in comparsion at only $4,150.00 . . . .

 
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cappuccinoboy
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Espresso: Milano pod, Milano fully...
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Posted Mon Jul 6, 2009, 12:28pm
Subject: Re: Technically and Mechanically  - Conical vs Flat Burrs
 

JonR10 Said:

While it seems you have learned a bit about burrs (apparently what is generally purported by machine manufacturers), here you are technically incorrect about the physics of rotation. The relationship is determined by a simple law: Two objects with the same outside diameter and rotational velocity will have the same peripheral speed:    

            r x w = v         Where r is radius, w is angular velocity, and v is peripheral speed.  

My fastest-motor grinder is also by far the quietest. It's not the housing per se, but rather seems related to burr geometry and motor mounting.  For example, the less expensive conical grinders are some of the loudest available...sounding like an airplane jet engine but the German flat burr grinder has rubberized motor mounts to isolate the motor assembly and it is amazingly quiet

Posted July 5, 2009 link

Keep my promise. About size oc conical burrs :
38mm, lower burr OD 29mm, thickness 17mm
47mm, lower burr OD 31.5mm, thickness 20mm
68mm, lower burr OD 49mm, thickness 25mm

Sorry for the limited range, but they happen to be the sole sizes I am currently using
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cappuccinoboy
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Location: MILANO
Expertise: Professional

Espresso: Milano pod, Milano fully...
Grinder: grind on demand
Posted Mon Jul 6, 2009, 12:47pm
Subject: Re: Technically and Mechanically  - Conical vs Flat Burrs
 

IMAWriter Said:

Cap boy.....methinks you might want to gracefully withdraw from THIS battle! LOL
Jon is an engineer, but in true R10 fashion is giving you a gentle pat on the posterior, but at the same time questioning your scientific method.
besides, this conical/v flat burr thing is to me, all about taste anyway.
By the way, you list yourself as a professional, yet your gear appears to be pod oriented.
Whoops...don't want to get into THAT discussion.
However, as a manual grinder owner, I do agree with you that for whatever reason, a somewhat miniature in stature conical in my manual does pretty much as superior a job as does a Mazzer mini, close to an SJ.

Posted July 5, 2009 link

I do appreciate your help, but I think I can hold my own with Jon, after all is just theory (his) against daily practice (mine) : but I do accept that there is quite a bit to be learned from these fights....
Since there is no change in taste of brew (with either method), believe me it is just a matter of manufacturing choice of giving an option to the customer, who will be happier knowing that he could have chosen either method since he will always be certain that he did chose the best one.......
About pods if you were a manufacturer you would be aware that the majority of people out there are just normal decent people who love to enjoy a cup of "decent" espresso without having the fuss of going through rituals in the search for the "perfect" one, and if that "decent" cup turns out to be "good" than they are just happier...
Of course out there  are also a lot (vast minority though) of never satisfied people looking for more .... and willing to spend more : so, it is all about marketing .....
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JonR10
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JonR10
Joined: 26 Apr 2004
Posts: 10,376
Location: Houston, Texas
Expertise: I love coffee

Espresso: E61 Legend, Livietta,...
Grinder: Robur, B-Vario-W
Vac Pot: Hario Tabletop, Yama...
Drip: Technivorm
Roaster: 1-lb US Roaster, Behmor 1600
Posted Mon Jul 6, 2009, 1:38pm
Subject: Re: Technically and Mechanically  - Conical vs Flat Burrs
 

You seem to think I am just giving theory but I am referencing actual test data to back up my assertions.  Also, it might surprise you to know that I have been making espresso every day for over 20 years, so I have a bit of experience myself, sir.  In my profession, testing results are much more credible than other unsupported claims.  ;-)

cappuccinoboy Said:

Since there is no change in taste of brew (with either method), believe me it is just a matter of manufacturing choice of giving an option to the customer, who will be happier knowing that he could have chosen either method since he will always be certain that he did chose the best one.......

Posted July 6, 2009 link

This is not correct (another technically incorrect assertion).  Maybe "seasoned" coffee all tastes the same no matter what grinder you use, but this is not true for fresh artisan beans/blends.

Testing has been done that shows a different particle size distribution from conical vs. flat burrs.  This indicates that each burr type has it's own characteristic grind, and some folks can certainly taste the difference.  This is also why the conical burrs seem more forgiving of grind adjustment.  

Here are some links for testing threads that may be enlightening for you (they were for me):

CLICK HERE to see evidence of particle size distribution differences between conical and flat burrs.


CLICK HERE to see evidence that there is no difference in grounds heating between flat and conical burrs (home use)


CLICK HERE to see taste testing performed with various grinders by a professional cupper.


.

 
Jon Rosenthal
Houston, TX
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