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Auger FB Hybrid
CharcoalRoaster
I believe Renatoa and I (maybe a few others) briefly discussed a FB hybrid roaster that could incorporate an auger in order to reduce the need for high airflow agitation among other things but I can't find the thread any longer.

I've been disappointed with my current setup for a variety of reasons that don't need to be listed here. With that said I was looking at my pile-o-parts and wanted to open up for discussion an exploration of an augered fluidbed roaster with a capacity between 500g-1kg using electricity as the heat source.

Here's a rough sketch of one idea that came to my mind to get the conversation started ThumbsUp
CharcoalRoaster attached the following image:
augerfb.png
renatoa
The other thread is here:
https://homeroast...ad_id=6264
renatoa
If using an auger, i.e. mechanical agitation, then it is no more FB, but a hot air roaster...
The first consequence of the assert above is such machine is no more mandatory to have a vertical layout. Same freedom for the heat source placement, no more need to be axial/in line.
Could be horizontal, as a Loring roaster, or partially inclined, as is RotateFun, my personal favourite design of such kind, i.e. beans agitation done by an auger.
Edited by renatoa on 05/27/2021 2:36 PM
CharcoalRoaster
So I completed the fabrication of my new RC that will utilize an auger for agitation of the greens. One thing I'm stumped about is how to drive the auger? Any ideas?

RPM speed?

Sprocket and chain? Heat resistant but needs more space

Direct drive? motor potentially affected by heat source/flow

RC = 5" diameter x 24" tall
Auger = 18" tall by 3" diameter at it's base (haven't measured the shaft but guessing it's right around 3/8"-1/2")

See pics below of the current RC configuration
https://www.dropb...zWz1a?dl=0
renatoa
Nesco is 20 RPM if I remember well...

For example, in the case of the Nesco, the RC is a glass cylinder/carafe, with a perforated tin base, that is placed on top of the heater coil, very similar with the popcorn roasters heater.
Below the heater assembly there is the auger drive wheel, part of a pulley/belt system.
Fresh air comes from a small pump, cooling the auger wheel and the belt, then enter in the heater assembly, and from there, by natural convection, in the RC base. The air flow is not very big, just enough to raise the chaff at the top of the RC, where is a chaff collector.
The advantage of this approach, for me, is the easy way how you charge and remove the RC with beans from the rest of the machine, because the auger is driven via a fork coupling, not a rigid coupling.
CharcoalRoaster
I'm unfamiliar with fork couplings but have a vague idea of the purpose vs a rigid coupling. Any examples you could send my way?
renatoa
This is the heater plate, with the vertical auger shaft.

cdn.statically.io/img/sieuthicafe.vn/f=auto%2Cq=100/wp-content/uploads/2017/09/Máy-rang-mẫu-Nesco-Coffee-Roaster-Sample-140G_Sieuthicafe_2.jpg

The horizontal rod enters into a corresponding auger shaft slot, driving it and starting beans lift movement.
renatoa
Attached is the roast carafe support, i.e. heater output plate, with the vertical auger shaft.

The horizontal rod enters into a corresponding auger shaft slot, driving it and starting beans lift movement.
...
renatoa attached the following image:
my-rang-mu-nesco-coffee-roaster-sample-140g_sieuthicafe_2.jpg
CharcoalRoaster
Fabrication of roaster is just about complete but before buttoning everything up I wanted to see how successful the auger would be in agitation.

Disappointed to say the least. I think this is about 1lb of beans and it looks like it agitates an "inner ring" of bean mass but leaves the outside largely untouched.

Do I need a bigger auger? I tried blasting some air through the RC and I don't think it provided any "loft" assistance.

https://www.dropb...1.MOV?dl=0

I couldn't get my camera to focus on the bean mass, it kept trying to focus on the auger so sorry for the blurriness of the bean mass
CharcoalRoaster
One thought I had if a larger auger is not going to solve agitation issues would be to install a perforated cone instead of a perforated flat bottom in the RC.

In the same way this assists in bean circulation in a true FB would it assist in moving the bean mass with an auger?
CharcoalRoaster
Bump. Any and all help would be appreciated? I even tried leaning the entire RC on about a 35-45* angle but to no discernible effect. Still ended up with what looked like just jostling beans but no where near the needed level of agitation.

Shock
allenb
My initial hunch is the auger is too small in diameter in proportion to the RC's diameter. Do you know what the ratio is of auger diameter to RC diameter of the zach and dannys? Also, an important design element for any auger is its pitch angle. If it turns out to be too shallow, you would need to increase speed to compensate. Lots going on here that needs to come together for success.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
CharcoalRoaster
Yeah, that's what I figure too Allen. Thanks for the reply. I don't see any other auger options as ebay is not coming up with much in terms of search results.

I do not know the ratio of the Z&D's. I've ordered a motor with almost 2x the RPM to see if that makes a difference. Current RPM =60rpm and new motor will be 110rpm.

cross fingers
CharcoalRoaster
I had an old tri-clamp adapter fitting laying around that matched the ID of the RC perfectly with no gaps. 5"-3" funnel shaped. the auger had about 1/2" of clearance and I thought maybe the funnel shape would help with agitation. However, the auger kept getting jammed and was unable to agitate at all.

Does anyone know a rule of thumb for optimum ratio of auger diameter /cylinder diameter? I tried a google search but must be using the wrong keywords as I couldn't find anything
CharcoalRoaster
So I hooked up the new motor with an increase to 110 RPM it looks like it may be sufficient agitation for at least 2lb, but its gentle slow agitation with just added green beans.

Since I've primarily roasted on FB Roasters I'm familiar with the optimal agitation flow to end with a relatively even roast. I've followed all you drum builders out there and have observed a fairly aggressive agitation with the tumbling of the beans by the veins and drum circulation.

I watched a few videos of the Nesco in motion and that auger is PUMPING gotta be close to like 200RPM! I know that as the roast progresses the beans will lose moisture/density and become lighter resulting in more agitation without an increase in RPM.

My question now, is how slow is too slow re: agitation toward the beginning of the roast? Do I need to find a motor that will spin faster than my current 110RPM or will it be sufficient after the first couple of minutes into the roast?
renatoa
Nesco speed could be so high because the airflow is sluggish, at the limit to lift the chaff.
Agitating speed in various hot air machines could be very different, with the slowest examples being Gene, with 10 RPM of that wobble paddle, and Dieckman Roestmeister, with 20 RPM of a mesh drum/cage. For both the airflow is comparable with a hotgun.
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