Jasonian wrote:I'm in the market, but I'm not convinced by initial hype.

And you shouldn't be. Skepticism is a Good Thing. My comparisons are flawed because it's unfair to compare the new Duranium burrs to my used Mazzer burrs. Furthermore, with only one SJ grinder on my counter, it should be obvious that I cannot perform any scientifically valid taste comparisons. I've only had these burrs for a couple of days, and I'm going out on a limb by recommending them.

But I'm reasonably comfortable posting my positive first impressions of this new burr set for several reasons. Michael Teahan (a true espresso luminary) gave the Duranium burr set his blessing when I contacted him offline. My observations thus far reinforce his comments about the faster grinding speed. The taste profile is similar to the standard Mazzer burr set, but I'd rate the Duranium pours slightly better. This could be due to burr sharpness. In his new book, Scott Rao states emphatically (p.7) that

The single most important feature of a grinder is sharp burrs.

According to Michael Teahan, the Duranium burrs are significantly sharper and harder than the standard Mazzer burrs, so they should stay sharper over time, as well as lasting longer.

Finally, the small cost differential between the Mazzer burrs and the Duranium burrs (under $30) makes this a relatively low risk purchase. I'd be much more cautious about recommending a $1K+ grinder after just a few pours!

I'm also eager to see more reports on this new burr set. But I'm predicting we've got a winner.
EDIT: Due to grinder stalling issues, I must retract this statement. See my followup posts on this thread for details.

I wasn't trying to be critical of your review, John, so I hope you didn't take it as such.

I'd just hope to see conclusive evidence from the seller of said burrs.

I realize it's only a little more money, but I haven't been sold yet.

On that note, I haven't been sold on the stock burrs either.

What exactly is the structure of this "duranium" substance that makes it hold a sharper edge?

Someone SELL these things, darn it!

Well folks, I may have to temper my early enthusiasm for this burr set. I observed my first incident of grinder stalling this morning. After turning the grinder off and back on, the SJ ground flawlessly again. That's one incident in 3 days and at least two dozen shots, but cause for some concern, since I never observed this behavior in 3 years with the standard Mazzer burr set. I'll keep you posted...

I would be very interested to know what metal these burrs are made from ("duranium" is a word that does not satisfy me in this regard). The "duranium" looks to me like it may be a high-end stainless alloy....not your normal 300-series

Do the new burrs seem to be about the same density?
(For the same geometry do they seem heavy or lighter than the originals?)

Also, I am very interested in hearing any theories as to why a sharper and tougher (harder?) burr would cause a very powerful grinder to stall. Anyone have any SWAG's?

Different angles on the more-aggressive burr edges?

brad

RapidCoffee wrote: I observed my first incident of grinder stalling this morning. After turning the grinder off and back on, the SJ ground flawlessly again. That's one incident in 3 days and at least two dozen shots, but cause for some concern, since I never observed this behavior in 3 years with the standard Mazzer burr set.

JonR10 wrote:Also, I am very interested in hearing any theories as to why a sharper and tougher (harder?) burr would cause a very powerful grinder to stall. Anyone have any SWAG's?

RapidCoffee, is it possible you hit a pebble?

JonR10, as DigMe said, the faster grinding speed is due to a more aggressive burr design. More aggressive requires more power, so maybe the grinder motor is close to its torque limit with some roasts.

JonR10 wrote:I would be very interested to know what metal these burrs are made from...

I'd suggest contacting Michael Teahan <michael@espressopartsource.com> for particulars.

JonR10 wrote:Also, I am very interested in hearing any theories as to why a sharper and tougher (harder?) burr would cause a very powerful grinder to stall.

Yah, me too. Aside from initial tests, there were supposedly no other reports of stalling.

AndyS wrote:RapidCoffee, is it possible you hit a pebble?

Not a chance. When the SJ stalled on takeoff, I immediately turned the grinder off and then back on. On the second startup, it ground the beans just fine. No evidence of anything unusual in there.

AndyS wrote:JonR10, as DigMe said, the faster grinding speed is due to a more aggressive burr design. More aggressive requires more power, so maybe the grinder motor is close to its torque limit with some roasts.

I concur on both counts. Perhaps the cutting edges on the burrs are at a steeper pitch. This was a fairly light home roast, and a fairly fine grind (I'm currently testing a couple of lever machines), so I'm sure it did stress the motor.

My first WAG: start capacitor, since the SJ stalled on takeoff, not in mid-grind. (Edit: I'm told this is unlikely.)

AndyS wrote:JonR10, as DigMe said, the faster grinding speed is due to a more aggressive burr design. More aggressive requires more power, so maybe the grinder motor is close to its torque limit with some roasts.

Hmmm...I wouldn't have thought that the Super-Jolly was anywhere near any operational limits judging by the overbuilt nature of Mazzer designs, but if a slight change in cutting angle causes stalls then perhaps it's true. I guess it seems odd to me that such a heavy-duty design would operate so close to its torque limit.

John - do you keep beans loaded in the hopper or do you load per shot?

I have recently purchased another used Super-Jolly on eBay (found a mis-named one with poor pics that I won for under $200). It looks like it's probably in rough shape and needs extensive cleaning so maybe I'll try a set of these burrs out against the "stock" set I have on my modified doserless SJ

Maybe I'll write to Michael and see if he knows more about the alloy being used. I prefer to buy from him when I can (all of my grinder mills, group screens, and gaskets as well as a couple of bottomless portafilters I got from them to use with the COOL artisan-crafted wooden handles I found)

JonR10 wrote:I wouldn't have thought that the Super-Jolly was anywhere near any operational limits judging by the overbuilt nature of Mazzer designs, but if a slight change in cutting angle causes stalls then perhaps it's true. I guess it seems odd to me that such a heavy-duty design would operate so close to its torque limit.

Seems odd to me, too.

John says they grind about 50% faster than the old burrs. I guess that puts an upper limit on how much more power they require compared to the old ones: 50%. In practice, since they're new and sharper, they probably take less than 50% more power. But still, even 30% would be a big jump.

JonR10 wrote:Hmmm...I wouldn't have thought that the Super-Jolly was anywhere near any operational limits judging by the overbuilt nature of Mazzer designs, but if a slight change in cutting angle causes stalls then perhaps it's true. I guess it seems odd to me that such a heavy-duty design would operate so close to its torque limit.

And yet surely you heard of people around the forums who have had the burrs stall due to a single bean being caught somewhere in there, no?

brad