Classifying is a great technique, and it can be used both pre- and post-winnowing. Getting all of the pieces into more or less the same size/mass for a pass makes the overall yields much higher (and, interestingly, the overall process faster).
I use a large mesh (1/4") to sieve the output of the cracker.
I then use a smaller mesh (1/10") to sieve out most of the fines.
Whole beans that don't go through the 1/4" mesh can be run though the cracker again. Pieces (usually long and skinny with shell attached) can be pushed through the mesh by hand.
The fraction that falls through the 1/10" mesh can be further separated to eliminate the small dust which is basically not usable. I collect the larger-sized fraction from several winnowing batches and winnow it all at once when I get a decent amount.
The medium-sized fraction (that passes through the 1/4" mesh but not through the 1/10" mesh) winnows very cleanly once the airflow is tuned properly.
I had forgotten all about that video.Thanks for posting it!
So it looks like the DD can be made to winnow by allowing airflow up through the bottom of the cyclone and adjusting the vacuum pressure. In the video, he had to run the cracked beans through the winnower three times, but hopefully it could be tuned to work in one pass.
I've been using the DD (it's my set-up in the video that Kane posted the link to) for the last year or so and am very happy with the results. I found it works best if you extend the cone by about 6" (I just taped a cardboard funnel I made to the bottom of the DD lid), you need to either cut a hole in the lid or, as I did, just put a spacer between the lid and the nib bucket, to allow for sufficient airflow up the DD, and you need to add a bucket between the DD and the vacuum to receive the husks and keep them from going into the vacuum. I get almost zero husks falling into the nibs, but I do suck some of the nibs up with the husks -- I run three passes with the husks and capture somewhere between 85 and 90% of the theoretical total (assuming about 88% nibs by weight in a typical bean). The whole set-up cost me about $100.
My next steps with it are to add a valve to adjust the inlet airflow, and to add an automatic feeder -- I found an attachment for my KitchenAid mixer that I think will do the job with a couple of minor adjustments -- I'm going to give that its first go this coming week.
...I do think that by adding two valves (one to control the total flow rate and one to control the air flow through the bottom of the DD) and controlling the material feed rate you could get good separation in a single pass. Once I hard-plumb the system I'll add those controls -- right now it is a 'portable' system that gets assembled and disassembled every time I make a batch of chocolate...
Hi David. Thanks for your video and input on this thread.
I was thinking of adding some pvc below the DD to extend the funnel a bit. The BC winnower has long tubes under each funnel, and you can see husk being sucked up through the left one.
I'd use an unmodified DD as the second stage to capture everything that was removed from the first one.
Have you tried adjusting the strength of the vacuum? I was thinking of adding a valve between the first and second DDs that would allow the airflow to be reduced. Is this what the valve to control the total flow that you mention would do? Or would that be on the inlet side (where the cracked beans enter)?
If I build one, I plan to use the champion to crack and feed the beans as I do with my current winnower.
One issue I see is that you can't see the winnowed nibs without lifting the lid.
Lastly, what about adding a third DD? The first would be tuned to do the first winnowing pass, the second would be tuned to capture the nibs that the first DD sucked up, and the third would be the unmodified DD to capture the husks before they enter the vacuum. This may be more effort than it's worth, but I really need something that will work in one pass.
Hi Ben -- I do think that adjusting the vacuum and the flow rates will result in better first-pass removal (even for a single stage system). I see challenges using a two stage DD system in that you need to ensure a certain upward airflow rate in both DDs in order to prevent the husks from falling to the bottom, so balancing the flows would be more of a challenge. I'd expect even more challenges using a three stage system. Once we get set up in our new leased space I should be able to start experimenting with improvements. Like I mentioned earlier, my first small victory will be in automating the feed so that I can go do something else while my system cracks and winnows -- very manual at the moment.
I'll definitely share anything I learn -- it's a fun problem to try to solve.
I am really curious to know what Kitchen Aid mixer attachment you think would work. I've been looking at the idea of custom-crafting attachments for a variety of purposes, using the motor in the Kitchen Aid the way people use the motor in the Champion.
It occurs to me that something you might be able to do is incorporate a classifier into the second bucket. This would let the fines drop through while keeping the larger pieces - might help reduce the number of passes required. Of course, pre-classifying before you drop the nib into the winnower is another way to do that.
I wonder if there is also a way to "fluidize" the bed of nib that is waiting to drop into the first bucket using air being drawn through the system. This would mean you would not need a separate machine with a motor (the Kitchen Aid) (or a small vibratory motor) and the supply of nib would not "clog" the hopper. Sounds like a relatively straightforward thing to make.
OR - take a look at the BC machine, they use the vacuum to suck up the nib rather than pouring it A lot to be said for that approach.
Lol -- necessity really is the mother of invention! I'm happy to report that the proof-of-concept winnower feeder works! Here's a (very) short video: http://www.youtube.com/watch?v=RlfdF_gA2MU&feature=youtu.be
The feeder is a KitchenAid food grinder attachment sans the cutting blades and end cap. My "hopper" is a blender pitcher. I'll get cute later with the refinements, but it does look like a very inexpensive screw feeder (which is all this in without the blades) works really well. An added bonus is that the feed rate can be adjusted over a wide range using the KitchenAid speed settings.
Fun hack, David. This is turning out to be a real fun discussion.
First 'production' run indicates that valves are going to be a 'must-have'. I had my flow rates tuned for manual feeding, which turns out to be slower than what the KitchenAid set up delivers, so now I'm having to adjust in order to get a clean separation again. The fun part, though, is just seeing that it's possible. I don't think I'd dedicate a KitchenAid to this task once we get up and going -- a small variable speed motor should do the trick for a lot less money.
do you know the percentage of dust you get?...