Hi,
I have been thinking a lot of what is the relation between grinding speed and coffee quality. I have an 220V single-phase Mazzer Major. Its grinding speed is 1400 rpm (50 Hz) . But at this speed everything is suppressed by the citrus flavor at the fruity taste light roasted coffe.
Let's look at the pros grinding mills speeds:
-Nuova Simonelli Mythos One: 900 Rpm
-Nuova Simonelli Barista Low RPM Espresso Grinder: 350-400 Rpm
-Mazzer ZM Filter: 900 Rpm
-Mazzer Robur: 420 Rpm
-Mazzer Kold: 420 Rpm
-Caedo E92: 240 Rpm
-Compak K10 (E10): 325/340 Rpm
-Hg One: variable

There is an option to reduce this speed: a single-phase inverter. (single-phase input - single-phase output) I connected one of this to the motor. It can be changed by one tenth between 0-120 Hertz. The aim is to lower the speed, thus, the part above 50 Hertz (US. 60Hz) does not matter. The frequency may be reduced to 22 Hz, the engine will not start,
but this is due to the magnetic switch inside, which is included in the normal operation because of the powder container level switch, metering switch and motor overload protection. However, if the
engine starts can be reduced further while driving, and even at 10 Hz (250 RPM) can also be grind, but the torque will be reduced very much.
The results:
- It's significantly changed the quality (form) of the grist, It has become much more even, while I reduced the frequency of 50 Hz (1400 RPM) to 22 Hertz (636 RPM), and I had to refine the grist of the same quantity.
-The lowest speed which can be grinding is 11 Hz (285 Rpm), in this case only 4-6 coffee beans can be ground at a time.
-We tested many kinds of coffee, and compared with a Hg One grinder. In one case, the Major was better than Hg one.
Fruity coffee
- Fast speed (1400 RPM) grinding: cloudy, very citrusy, nothing highlight, flat and dull taste
- 600 rpm grinding: missing the tartness of lemon, the coffee tastes cleared, much more noticeable fruits, more significantly distinctive flavour quality
-285 rpm grinding: pure taste, but lost some flavour ingredients
The best results were achieved at about 600 rpm, but some coffee varieties are best at 400 rpm.
Chocolate flavour coffee
-At lower speed the tastes are more recognizable too, such as the fruity coffee, but it declined the corpulence.
My experience is that the speed control is also very important than the grinders. It can be used within wide limits in, or a fine-tuning tool. According to my experiments due to the speed of the grinder the coffee has a quality of a combination of a full-body and oily flavour that could be changed by altering the speed.

https://www.youtube.com/watch?v=Zc6ljtSm09A

Have anybody some experience of this modification?

I saw your video the other day and thought it was very interesting. I haven't tried changing the grind speed of my Major. I do note that on your list of grinders and their speeds, several have conical burrs and not flat burrs. It seems that most conical burr grinders spin the burrs slower than the flat burr grinders.

It seems the general consensus of conical burr grinders is that it highlights the individual flavors better and it seemed to be attributed to the burrs being conical vs flat, but with your tests and tasting notes, perhaps its attributable to the rotational speed of the burrs and not that they are conical vs flat?

Very interesting. Thanks!

I always liked our desire to explain why things are in a certain way, unfortunately we also like very simple and easy understandable explanations.

Unfortunately I do not belive that it is the effect of just one aspect, it is most likely the combination of several effects that influence on each other, this means Alignment, burr shape and size, grinding speed/RPM, vertical/horizontal or angeled mounting of the burrs, temperature and temprature development.

In top there are other things like retention, amble temperature, humidity, how we decide to use our grinders (single dosinger vs. hopper fed) that ultimately will impact on the results as well.

That said variable RPM is one of the recent developments, whether or not it dos truely impact on performence needs more testing, but several manufactures such as Titus, Mahlkonig and Lyn Weber had added this option on their high end products so you're defiantly hitting the right moment with your testing.

You might want to read this thread: Burr RPM affects grind particle size distribution significantly

I would like to play with it, but having trouble finding affordable option for 110v.

Interesting....just to find a cheap single phase regulator....they are more expensive that I would have thought even on ali...

Perhaps this might work? http://www.auberins.com/index.php?main_ ... cts_id=332

A bit DIY... you'd have to mount it in a case w/ a heatsink... but relatively inexpensive.

Hmm thanks, but I don't think a voltage regulator using a triac is the same as a frequency convertor...

This would probably be the better option http://www.auberins.com/index.php?main_ ... cts_id=452 ...if it is an option. We have talked about this unit before in other threads and I don't think a conclusion was reached, i.e. some say yes and some say no, but I don't know anyone who has actually tried it. I'm not trying it on my grinder, I can tell you that.

I had the opportunity to compare my grinder with a Hungarian DIY grinder, which name is Combat, and its equipped with a 83 mm Mazzer Robur burr sets. This is a prototype. This grinder speed can be adjusted between 112 rpm and 346 rpm. The best results were archived at about 260 rpm. I was wondering how I could align the two grinders by changing only the gear. I only set the speed Major between 500 rpm and 700 rpm.

Consequently, I could align the two machines very well. Concerning their basic characteristics it can be said that Major makes full-bodied drink, while Combat prepares slightly thinner but that remains in the mouth longer. And from this point a matter of taste, who does what like it better. In my opinion that every factory grinder has the ideal speed with which the burr set can best produce its own level. But even if we do not talk optimum speed, but individual tastes, it also gives enormous freedom in this option.

I think that has space both grinder in the kitchen.