Big News - The SUD Arrives

Fellow Coffeesnobs ‘Christretto’, ‘TerryM’, ‘Alchemist’ and myself often sit and plan mad designs for roasters and other gear.

With our individual levels of production approaching 2 kilos of roasted coffee a week, we’d all found the chore of searching for stones particularly tedious, especially when roasting Yemen Ismali.

Much of the world’s coffee is dried after being spread across the ground on hard clay of concrete. Small stones are swept up into bags with the coffee and these stones can destroy a grinder if not removed.

We’d examined the practicability of buying coffee de-stoners to remove the small stones that are found in bags of green coffee beans but cost factors forced us to innovate.

And a good thing too!

I am proud to present the “SUD” or Sam’s Ultimate De-stoner, a custom designed de-stoning device for the discerning CoffeeSnob. While the initial work was a collaborative effort of Perth CoffeeSnobs, the real accolades for the final execution and innovation must go to Sam the ‘Alchemist’, who 24 hours after the final ‘Specific Gravity vs Air Pressure’ epiphany actually had built a fully working successful de-stoner.

The underlying principle is straightforward. After you roast the coffee, the specific gravity of the coffee beans has been reduced so that the application of a certain level of vacuum applied will lift anything that shares that specific gravity and transfer it to the recovery chamber.

In simple terms – it picks up the coffee and leaves the stones behind.

It doesn’t matter what mass the stones are – even a stone with less mass than a coffee bean will be left behind because its specific gravity is higher and the air pressure not sufficient to loft it into the chamber.

The epiphany came when looking at the early patent for the Jabez Burns’ design for a de-stoner and I could finally see that what was really important was to ensure that the aperture to ‘suck’ the beans would have a high relative air pressure and needed to be emptied into a larger container with a low relative air pressure. This means the beans just fall to the bottom without the problem of their being sucked into the vacuum device itself.

Here’s the 1929 Patent image of the Jabez Burns and Co. “Coffee cleaning apparatus” from which we took our inspiration:

APPARATUS FOR CLEANING COFFEE QEQRGE C. HERZ

And now, with ‘Alchemists’ permission I have posted below the photographs and his instructions for creating your own de-stoner and I think it highly creditable of him to commit this design to the public domain so that CoffeeSnobs can build their own!

Take it away Sam. . .

“There are essentially two really important parts to this home made Coffee De-Stoner - (a) The Collection Chamber (ie: Bucket!), and (b) The Vacuum Cleaner.

I'll first describe how I put together the collection chamber (from bits that I bought from Bunnings).

Choosing the right vacuum cleaner involved a bit of trial and error, so I'll describe this in detail further below.


Thing's you'll need to buy for the Collection Chamber:

Materials
1 x Plastic Food-grade bucket with air tight lid
1 x Plastic sink drain
1 x Double ended tank-bung (32 mm diameter)
1 x length of clear PVC hose (32 mm diameter)
1 x length of clear PVC hose (40 mm diameter)
1 x length of clear PVC hose (50 mm diameter)
2 x Cable ties
1 x Rubber sink plug
1 x Roll of gaffer tape
1 x Sheet of foam


TOOLS:
32 mm hole saw
Drill
Hot glue gun
Scissors
Sharp knife/Hacksaw

Step 1
Cut a hole out the bucket lid the size of the plastic sink drain (this is where the sharp scissors came in). The plastic sink drain screws into it, with the flat part of the drain sitting flush with the underside of the bucket's lid.

Depending on which sink drain you bought, you may need to remove/cut out the plastic 'grate' (the bit that stops wedding rings and other items from going down the sink!)

Photo 1 - Underside of Plastic Bucket's lid:



Photo 2 - The top side of the plastic bucket's lid

Step 2
Using the hole saw, cut a 32 mm hole on the wall of the bucket around three quarters up the side (this will be where the beans enter). Screw in the tank bung and lock in place (use the locking washer / threaded half of the bung on the inside of the bucket's wall).

Photo 3 - Tank bung goes in here (it's official, this bucket now has "102 Uses") :-)




Photo 4 - Tank Bung screwed into side-wall of plastic bucket:

Step 3
Cut an 8 inch length off the 32 mm PCV pipe - ensuring one end is cut at an angle (somewhere around 45 degrees)

Photo 5 - An 8 inch length of 32 mm PVC pipe

Step 4
Press the angled end of the PVC pipe over the end of the tank bung (making sure the other end of the PVC piper is facing towards the bottom of the bucket. Use two cable ties to tightly secure the PVC pipe around the tank bung (cable ties not shown).

Photo 6 - PVC pipe on end of the tank bung (cable ties not shown)

Step 5
Cut two pieces of foam (one square and the other round, of equal size to the diameter of the bucket's base). Hot glue these into place - the foam softens the landing and eliminates breakage of brittle, fresh roasted beans!

Photo 7 - Pieces of foam hot-glued into place

Step 6
Place 32 mm PVC pipe over the outer part of the tank bung, then slice off 2-3 inches from the bung (in preparation of making a "Goose-neck" - see step 7 below)

Photo 8 - 32 mm PVC pipe pushed over the end of the tank-bung

Step 7
Making the "Goose neck" - insert a 32 mm diameter length of PVC (2-3 inches long) into a 40 mm diameter length of PVC (also 2-3 inches long), into the full length of the 50 mm diameter PVC pipe (the full length of the 50 mm diameter PVC at Bunnings is 900 mm)

Photo 9 - One segment of PVC... in another... then in another.

Step 8
Seal the goose-neck up with the gaffer tape - ensuring no air-leakage!


Step 9
Cut a hole in the rubber sink plug equal to the diameter of the vacuum cleaner's nozzle, then insert the rubber sink plug into the inverted sink drain.

Photo 10 - The finished 'Collection Chamber':- Vacuum cleaner nozzle goes in at the top...- Beans get sucked up the 50 mm PVC pipe through the side of the bucket wall and then drop into the bucket (without getting sucked into the vacuum cleaner!)





And the result of a de-stoning operation on Yemen Ismali?

So, which Vacuum Cleaner to buy?
Ideally, you will need a barrel vacuum cleaner that has:
- A low relatively level of suction; and
- Variable speed control.


After a lot of trial and error (and patience from the guys at Godfreys at Canning Vale), I chose the Hoover "Zoom" as the most effective unit - this has a variable speed, 1300 watt motor.


The de-stoning process?
(1) Insert the vacuum nozzle into the rubber sink plug at the top.

(2) Set the motor speed on the Vacuum to lowest setting.

(3) Switch on Vacuum cleaner.

(4) Place the end of the 50mm PVC intake nozzle into your coffee (I have found that placing the end of the intake nozzle into an empty bowl, then pouring the coffee in, one scoop at a time works best).

(5) At its lowest setting, the vacuum cleaner should not suck any beans up the PVC pipe - wind the vacuum motor's speed up slowly until it is 'dialled in' to the specific gravity of the roasted beans - the beans will slowly roll "up" the PVC pipe into the bucket.

(6) Remain attentive! While larger stones (>2mm) tend not to travel up the intake nozzle (they'll just hang around the base), smaller ones (<2mm) may trickle up the nozzle (but at a much slower pace than the coffee so these will be very easy to spot – when you see them, decrease the air flow and they’ll fall back down).

Warning – the de-stoner only removes hard lithic objects from your coffee beans, NOT pot-smoking relatives from your house.