But sealing it with O-Rings would not limit cooling any more than impacted grinds of coffee would.

-C

A cursory cleaning of the Robur produces about 2 grams of grinds, enough to affect the taste of subsequent shots, if left in the grinder too long.

The pathway between the burrs and the doser retains more coffee in my Robur than my Super Jolly and is a PITA to clear. For me, this is too much work for the occasional shot.

CRCasey wrote:They left that space behind the burrs on purpose. Call it a air insulation gap so that motor heat would not be directly conducted to the burr grinding surface?

Psyd wrote:Hmmm.... sounds, well, exactly like mine! Having this theory, I came here wondering if there was anyone that knew more about it than I. So far, no one has come up with anything more than mine and your theory.

If it is actually heat related, I'm loathe to screw with it regardless of how little work it actually does in my home environs.

I just wish that there was someone out there that could give us more than a guess.

I'm speculating and have no experience in the manufacture of burr sets :

• The ridge is there to machine flat. It's easier, faster, cheaper to machine a narrow ridge than the whole back of the burr. On a 58m burr, ~266mm² vs ~1734mm².
• The burrs are initially heated by grinding friction. The burr will be 'hotter' than the motor, but after a short while, the motor heat probably reverses the direction and motor heat is conducted into the burrs by mount contact and screws. Probably not much of an issue in home use.
• Heat is carried away from the burrs by coffee and air flow.
• Next to Zero heat transfer in either direction can occur when the gap is filled as there is no air flow and coffee is fairly decent insulator. Think expanded cell foam.

If worried about the gap, cut a donut of a thin closed cell foam and place between the carrier and the burr.

Fullsack wrote:The pathway between the burrs and the doser retains more coffee in my Robur than my Super Jolly and is a PITA to clear. For me, this is too much work for the occasional shot.

I got a set of 3/8" and 1/2" paintbrushes at Wallyworld for $1.68. The skinny brush is just the right size to quickly and easily sweep the chute between the burrs and doser.

And since the burr rotation stops quickly I can sweep, bump the motor, and sweep again enough times in 5-10 seconds to clear the grind path completely (meaning that my measured dose going in produces a similar measured dose coming out within a couple tenths of a gram every time).

cafeIKE wrote:I'm speculating and have no experience in the manufacture of burr sets :

All this sound perfectly sound, and, with the exception of the (now obvious) machining consideration, is my present stance. I dunno about foam, closed cell or no, as that sounds like a trap for oils and dust. I may just get me some gasket material and fill that up.
I'm loath to change the engineering, on something that I can't afford to replace, without a fair understanding of the engineering that went into the design.
I'm pretty sure that the machining consideration, as the motivation for that gap, is the lynch pin to my decision... ; >

Doesn't sound that different from my SJ, John - though if I understand correctly from Nicholas's pictures in the grind retention thread, the chute is at an angle to the side on the Robur whereas it's central and perpendicular on the SJ. I don't know whether that makes it any more fiddly.

I've been experimenting with single-dosing the Nino today. There's certainly more popcorning there than on the SJ and the beginning and end of the grind is quite coarse. I've had to tighten the grind up massively as a result. The results are varying in shot quality and taste in particular. It worked rather well on my Ethiopian Bale Wild Beans, with some wonderful flavour separation. Whereas on the Guatemalan Finca La Perla I still haven't dialed it in quite yet.

The Nino does turn somewhat faster than the Robur at 500 RPM vs. 420 RPM, so the Robur could be less affected by popcorning and therefore grind variation in this way - or it could just be a conical thing. And after all both were designed to have a weight of beans in their hoppers.

The trick of opening the flap, dosing and closing the flap on the hopper works just fine on the Nino, too - thanks!

Cheers

Mike

Psyd wrote:I dunno about foam, closed cell or no, as that sounds like a trap for oils and dust.

Closed cell foam will only collect on the edge and only as much as anything else. I suppose you could get some oil wicking between the burr and the gasket. The only way to stop that is seal with glue.

The idea is to fill the void with something slightly compressible to form a seal that fills the gap.
Something like McMaster-Carr should work.

That being said, the gap between the burr and the carrier collects only a very small fraction of the crud that comes out on a teardown.

michaelbenis wrote:The Nino does turn somewhat faster than the Robur at 500 RPM vs. 420 RPM, so the Robur could be less affected by popcorning and therefore grind variation in this way - or it could just be a conical thing.

I suspect at 60Hz our N.A. friends will be running at 500RPM as well.

cafeIKE wrote:That being said, the gap between the burr and the carrier collects only a very small fraction of the crud that comes out on a teardown.

I think that we've covered that in another thread. If you're attentive and conscientious, the stuff that accumulates under the burrs constitutes the majority, by a long road, what comes out of a Major on a teardown. At least what comes out between the hopper and the doser. The rest is immaterial.
Yeah, McMaster-Carr also has a number of pre-fabbed gaskets that would fit that gap like a glove. ID, OD, thickness, material, quantity and credit card number, and they'll ship 'em to your door.
Not that they're the cheapest solution all the time.
Grainger will do the same thing, but you'll have some old guy that knows things search them out for ya.

JonR10 wrote:I got a set of 3/8" and 1/2" paintbrushes at Wallyworld for $1.68. The skinny brush is just the right size to quickly and easily sweep the chute between the burrs and doser.

And since the burr rotation stops quickly I can sweep, bump the motor, and sweep again enough times in 5-10 seconds to clear the grind path completely (meaning that my measured dose going in produces a similar measured dose coming out within a couple tenths of a gram every time).

The thing that makes it awkward, is trying to get the brush into the chute with that black plastic gizmo in the way.