Modifications to reduce coffee retention in grind chamber

Grinders are one of the keys to exceptional espresso. Discuss them here.
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trzynkaa

#1: Post by trzynkaa »

I've been modifying my old Rossi RR45 again: This time to reduce the quantity of ground coffee that accumulates in the burr chamber. I've previously measured an accumulation of 5 grams of ground coffee in the burr chamber. This seems like whole lot of old stale coffee, and this would be acceptable if I was sure it would not contaminate the fresh coffee. Unfortunately I'm not convinced the accumulated stale coffee is not contaminating the fresh coffee. It seems like the freshly ground coffee smells better after I clean the burr chamber...

So I designed a washer to fit in the chamfer between the upper burr carrier and the upper burr to prevent the grounds from accumulating there. After fitting the washer, I measured the grounds accumulation at 2 grams. This is much better that the 5 grams before the washer.

This washer fits in the chamfer between the upper burr and the upper burr mounting surface and it is important that the washer does not affect how the upper burr mounts against the carrier. The outside diameter of the washer just fits in the burr chamber. Also, I fitted a rubber washer in the gap between the washer and upper burr carrier.
Pictures follow...

Grounds accumulation before washer...
Grounds accumulation before washer...
The washer...
Fitting the washer...

Grounds accumulation after washer...
Grounds accumulation after washer...

Any ideas on how to reduce the grounds accumulation further?
Is there information available on which grinders currently on the market have low grounds accumulation in the burr chamber?

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AlexH

#2: Post by AlexH »

How about a brush or tape mod to help the sweepers move the grounds out of the chamber? Either that or a machined burr chamber base that fitted below the bottom burr and extended out so the sweeper arms were much closer to it. It could have angled edges to encourage grounds to fall and be swept out.

On my RR45, the exit hole for the grounds does not line up with the matching port on the doser, there is a lip at the bottom, which means grounds get stuck there and build up. If this were modified either so there was no lip, or further so it sloped down from the burr chamber I would imagine they would flow out better.

zaphodbb

#3: Post by zaphodbb »

I've been thinking over this after reading trzynkaa's excellent article: Could a vortex be created using angled fins on the lower burr carrier in the space between the sweeper arms?
I've had a look at my RR45 (was an Auto, but I've 'fixed' it :) ) and there is a small gap - maybe an eighth of an inch between the carrier and the body, so maybe not enough...
On a side note - does anyone have a tip on how-to remove the lower carrier, more specifically, how to stop the carrier turning while undoing the nut without risking breaking the sweeper arms (can't believe that there's no locking hole on the main body). I want to make sure it's all clean before I start using it....

RandyR
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#4: Post by RandyR »

On a side note - does anyone have a tip on how-to remove the lower carrier, more specifically, how to stop the carrier turning while undoing the nut without risking breaking the sweeper arms (can't believe that there's no locking hole on the main body). I want to make sure it's all clean before I start using it....
There is a nice thread: "Removing Super Jolly Lower Burr Carrier"
Paul Pratt writes:
Jamming things in may cause damage to the shaft. An easier way is to use long bolts and tighten them in sequence. The bolts push against the main body and force the carrier off. The risk of damage is low because the amount of force required is very small.
There are some nice pics of the technique.

I just removed the lower carrier on my RR45, but I did not have long bolts of the proper thread/diameter to use this technique. So, I whittled a plastic toothbrush handle into a chisel/wedge shape, and tapped it gentlely under the carrier, through the exit chute. I pulled it out, spun the carrier a bit, and tapped from another angle and it popped off just fine. (It was quite gross underneath, so I'm glad I did it.)

zaphodbb

#5: Post by zaphodbb »

Thanks RandyR - I'll look for that thread.

OK, I understand what you say re carrier loosening and final removal (mine looks bad as well from what I can see eugh!), but my first hurdle is to get the nut undone - did you use the wedge to stop the carrier turning or am I missing something.
I've tried using a piece of wooden dowel through the exit chute held against one of the sweeper arms but the nut wouldn't budge and I really didn't want to break the sweeper arm by applying more pressure.
Are these nuts threadlocked?

Mind you, I'm still waiting for the new burrs to arrive so no rush, hey-ho...

zaphodbb

#6: Post by zaphodbb »

OK - finally removed the nut by making a 'jamming' tool out of eighth inch aluminium plate with a 'foot' projecting out of it that fitted into the exit chute. I used one of the old burrs to draw round on a piece of card and fiddled around to find the right angles for the 'foot' before transferring the shape to the ali plate.
The plate is secured to the carrier useing the exsisting burr screws, and I had to resort to a breaker-bar to get the leverage to undo the nut with the body of the motor held in a vice! (BTW, the nut is 17mm).
Once the nut was off, I used the long (set) screw technique to apply gentle upward pressure to release the lower carrier from the tapered shaft.

Thanks again to RandyR for pointing me to the article by Paul Pratt.

Now it's off, I've noticed the lower carrier has a casting ridge around the outside edge which encourages the retention of grinds, I intend to dremmel this off + smooth off the other casting ridges and bumps in the hope this will also reduce the amount of grind retention in the chamber.

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trzynkaa (original poster)

#7: Post by trzynkaa (original poster) »

Zaphodbb wrote:
OK - finally removed the nut by making a 'jamming' tool out of eighth inch aluminum plate with...
Make a special tool when you need to. Excellent!

When I installed new burrs on my RR45, I noted the lower burr was not self centering. To center the lower burr as best I can, I use a dial indicator to read the radial run out of the lower burr on the lower burr holder. I did this measurement by removing the doser and positioning the dial indicator to 'reach though' the grind exit chute.