JonR10 wrote:No.

I've never heard of that.

I've seen reports of it a couple of times on the forum. It's the reason for making sure the grinder is running when adjusting to a finer grind from what I've always understood.

brad

TimEggers wrote:What's "wrong" with stock OEM Mazzer burrs? What does the Duranium propose to improve on (and if it isn't flavor I'm not interested and if its just burr life is this really and issue for home use)?

One thing that Dan said about them but that I don't believe he would like entered for the record as any kind of hard comparison is:

It may be my imagination, but in addition to being really really fast, the taste profile seems different. A lot more chocolates, almost to the point of tasting like a tight ristretto despite my usual brew ratio.

he went on to say:

My preliminary thoughts on the early extractions with the Duraniums: If you're a latte lover who craves bass notes and chocolates, it may be worth checking into these space age burrs next time you change them. That said, it wasn't a blind taste test and thus my comments should be given appropriate weight (read: near zero )

He also noted the stalls in that same thread.

brad

RapidCoffee wrote:Jason, I've got no idea what this will tell you, but anything for the good of the cause.
<image>

Sorry about the quality, it's the closest I can get with the zoom lens that came with my Canon dSLR. If you'd care to donate a nice macro lens and lighting system, I promise to do better.

Thanks a lot, Jon.

It doesn't do good on its own, but report of "fluffier grounds" got me curious.

Titanium, molybdenum and stainless steel alloy?

http://coffeegeek.com/forums/espr...ders/353175#353175

3 week update on the new Mazzer Super Jolly Duranium burrs

I observed three incidents of grinder stalling in the first week after installing the new Duranium burrs. Each stall was associated with grinding a relatively light home roast (a la Paradise Espresso Classico). Turning on the grinder produced a hum, but the burrs did not start spinning. Immediately switching the grinder off and turning it back on allowed the grinder to function normally.

I'm happy to report no further incidents of grinder stalling since the first week. The stalling may have been caused by the brand new burr cutting edges, now dulled enough to reduce the required startup torque sufficiently to eliminate the problem. One hopes.

Aside from the initial stalling issue, I really like these new Duranium burrs. They grind 50-100% faster than the standard Mazzer burr set, should have significantly greater longevity, and produce a grind that seems very similar to the standard burr set. If another couple of weeks go by without problems, I'll give the Duranium burr set a cautious thumbs up. With one major caveat: grinder stalling is a real issue, especially with lighter roasts, until the burrs get broken in.

Thanks for the follow up John I look forward to further reports.

7 week update on the new Mazzer Super Jolly Duranium burrs

During the four weeks since my last post, I observed one more case of grinder stalling with the Duranium burrs. In this latest incident, I was grinding some smallish Yemen beans, and the cause of stalling was obvious. A peaberry bean was wedged between the burrs, preventing them from rotating on startup. Dislodging the bean allowed the grinder to function normally again. (Shoulda taken a pic... )

Anyway, that tears it. I can no longer recommend these burrs, due to ongoing stalling issues. It's a shame, really: the very people who would benefit most from the increased speed and longevity of this new burr set are also the ones most likely to suffer ill consequences from grinder stalling. I'm referring to busy coffee shops, where a barista won't always notice a stalled grinder immediately. That's asking for trouble.

BTW, I plan to keep the Duranium burrs installed on my Super Jolly. For a home barista, the infrequent stalls are easy to catch if you grind per shot. Aside from stalling, I really do like the new burr set.

RapidCoffee wrote:Anyway, that tears it. I can no longer recommend these burrs, due to ongoing stalling issues.

So, would you guess that if they were installed in a Major with an 83mm diameter, the stalling would still be an issue, or would the Major's horsepower make it moot? I'm still willing to test a set or two, if someone's interested in making Major burrs...HINT, friggin' HINT! ; >

We have had little feedback so far on the Duramills stalling save a couple of reports in the forums online. We haven't heard of any issues on the European side, so I think I have a handle on what might be happening. Especially when you consider that it is not a consistent problem.

Motors that operate on 60 hertz have slightly less torque than those at 50 hertz. We had this problem on the gear drive mechanisms of first generation super automatics. The same machine the operated at 12 RPM in the European Union had to be geared down to 10 RPM for the US at the same voltage rating. It did not have the torque to prevent the occasional jam.

Additionally, all of the torque to start the motor comes from the capacitor, which discharges almost immediately after the start cycle. If it isn't able to discharge enough to start the motor, the run windings of the motor will not be able to do it. Three phase motors are able to provide continuous torque and would eventually power through the bean.

The aggressive cut of these mills is rather like starting your car in second gear; it sounds like some motors may be at the cusp of the torque needed to perform effectively. It can be especially interesting if the line voltage gets closer to 110 than 119 volts. Some coffee bars and home users will never encounter a problem.

We may be able to manipulate the microfarad ratings of the cap to increase starting torque. Doing so can drop the run voltage very slightly, but shouldn't pose any long term problem. Those that grind to order can also use the Heather System: use the closing gate of the hopper to feed the beans. The extremely high end commercial grinders use lasers to measure the distance between the mills and start and stop with zero coffee load.

It appears that these mills push the design limits of some grinders. Ironically, we have a set installed in the Chinese Mazzer knockoff over at Supreme Bean and they have reported smooth sailing. I would hate to think they are using a tougher motor assembly than Mazzer. There might be a run on these things, even if they are a little goofy looking.

We have not brought in the Duramill for the Major yet. Large diameter mills use much larger motors but also run at lower RPM and require more starting torque. The speed at the outer edge of the mill (mm per second) is critical to grind quality. Smaller mills can spin faster than larger ones and not burn the coffee. The elongated cut pattern of conical mills allows for further reducing the speed, but requires gear reduction to overcome the torque issues.

We are following the progress to see how things pan out.

Michael Teahan
Espresso Resource / Espresso Part Source

mteahan wrote:The aggressive cut of these mills is rather like starting your car in second gear; it sounds like some motors may be at the cusp of the torque needed to perform effectively.

Excellent analogy. There are no stalling issues once the burrs start spinning.

mteahan wrote:We may be able to manipulate the microfarad ratings of the cap to increase starting torque.

If you're referring to the startup capacitor, I had the same thought. Knowledgeable sources suggested this was unlikely, but perhaps it was a reasonable idea after all...

Thanks for chiming in on this thread. I hope to hear more as these burrs see wider distribution. Other than Dan's initial tests, I seem to be the only home barista posting reports on this site.