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10/17/2021 12:40 PM
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10/14/2021 10:06 AM
Thanks for the addition to the group. Seriously considering building a drum roaster along the lines of oldgrumpus's. Love the design and craftsmanship.

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Increasing Batch Capacity
As I've been re-evaluating/building out a larger capacity FB Roaster (current maxed out at 500g) I've tackled heat, bean cooling, etc. but the one challenge still remaining is how to increase RC size.

Is it more efficient to scale up by widening the RC or simply making the RC taller?

With widening I could foresee issues of reducing from a 6"+ RC diameter back down to a couple/few inches of steel pipe used for airflow and heat???

With increasing the height of an RC I suppose you could end up with a 6ft tall RC to handle increased load capacity???

Who's got some thoughts, ideas, or insight?welcome2
I would try to keep a balance between pile height and diameter.
And relate it to your blower lifting capabilities.
For a given blower, is not the same thing to lift same mass as 1:1 or 2:1 or 1:2, I guess...

Or look for other design, there are ways to roast without floating beans, still using hot air, but moving them using other methods.
Like an auger (c.f. Zach and Dani) or something to that effect? Or TTKO?
Or Saturn centrifugal... or perforated/mesh drum with hot air, or an upsized Gene, or other TO based setup... or a Stronghold S7 clone...

btw, is KKTO Grin
All of which would require a basic rebuild of all the pieces I have available to me... unfortunately. I do have some perforated steel that I could slip into a housing to blow the hot air in but then wouldn't I be better off just building a drum roaster?!?
Not for me, I stay away from this concept too hard to manage for my understanding... and patience Grin
Drum yes, but only as an agitation method, I am sold to roasting done by true 100% convection (hot air), with optional recirculation.
Far IR could also be an option, even if not so well understood.

Actually, I find your idea of an upsized Nesco very interesting, I mean the Archimede screw based auger.
It could be actuated by a windshield wiper motor placed on the hot air exit cover of the RC.
Same cover could have a lateral pipe exit, routing the hot air to a small cyclone like the aluminium dust commander some of us already using, so chaff capture solved as well.
The requirements for hot air blower and heater power will decrease a lot, maybe even halve... noise also as well, making possible hearing FC, what are drawbacks ?
Fabrication??? Roflmao finding an auger that size??? Roflmao
So after looking a bit closer at the Nesco auger and searching around online it's pretty easy to find a garden auger that would fit inside a bakearound and emulate the design. But.... it begs a few questions...

(1) The Nesco auger looks to take up about 50% of the RC and since it works I would imagine following suit but would there be any danger of a wider auger while obviously avoiding too wide for potential wedging of bean against RC walls.

(2) The auger spirals are pretty tight and the options available online are spread out more. I would imagine this would make proper agitation of the bean mass more challenging (increase speed of auger to compensate???)

(3) With a traditional FB build there needs to be enough head room for spouting bed to not exit the RC. Could the batch size be increased in a similar/same size RC since airflow is going to be reduced because it won't be the main agitation of the bean mass?

You've got me interested Renatoa in heading this direction!ThumbsUp
The Nesco auger is a massive piece of metal, and indeed it takes too much space...
I was thinking to a tin made auger, the type used to mix concrete for small house works, check attached picture.
I would design such auger size to fit tight in the RC, but not scratching the glass.
So lift the outer layers of beans, near the glass, not the inner beans, as does Nesco. The central part of the RC being the beans return down path.

I can't argue for this design, is just a personal preference. Probably is a flashback of the moment when I seen first time such mixer, and I wondered if any usefulness for such purpose.
Not sure if the beans will obey with enough discipline to my wishes Grin
renatoa attached the following image:
I would be interested to see if an auger like that would provide sufficient agitation and recirculation
The auger is a really cool idea. If bean agitation is sufficient, renatoa is definitely right in that the benefits are a lot less BTU's required due to less airflow, smaller blower could be used or at lower speeds which means less noise too. While i can hear FC on my FB roasters, its not always easy and could definitely be improved on. If you try this route, please document and report!

If you don't go with an auger I think your question of how to increase batch size is it depends. The general rule of thumb which I'm sure you are aware of is don't go much higher then 1:1 on bed depth to width/diameter. I've found this can be bent to a relatively significant degree, and depending on how your perf plate is built, and the blower you have, you can go upwards of 2:1 here. So if your setup lends itself to that capability, then going higher obviously affords easy extra capacity.

I think the better answer is usually that adding cross-sectional area is the way to go to increase capacity. Especially since going from a 3" bake-a-round to a 4" tube or even better a 4" rectangular RC is quite a big capacity increase (could be as much as a little over 2 lbs for 4" square tube). Key consideration here is that your blower has enough CFM to accommodate the extra area for flow at required pressure.
Found a flaw of my auger design, it is not capable or would be very difficult to lift the first layer of beans, above the perforated mask.
Without a minimal airflow able to make them levitate, those beans will stay on the mask forever, and char, or maybe even burn.
To fix this, the auger must be precise done, ending at the level of mask with a paddle /blade, acting as a spade that shave the beans on the mask.


renatoa wrote:

Found a flaw of my auger design, it is not capable or would be very difficult to lift the first layer of beans, above the perforated mask.
Without a minimal airflow able to make them levitate, those beans will stay on the mask forever, and char, or maybe even burn.
To fix this, the auger must be precise done, ending at the level of mask with a paddle /blade, acting as a spade that shave the beans on the mask.

I wouldn't necessarily call that a "flaw". It definitely adds to the complexity of the build. However, I think you can still get away with significantly less airflow even if you don't have an augur that is able to scrape and lift the beans away from the perforated bottom. In my current RC, I can get the lower beans to start lifting and rotating on their own at lower flow then it takes for whole pile to circulate. So if you have something in there helping the pile move (auger), it should still require a lot less airflow then a traditional fluidbed, only enough to lift the bottom beans. Of course you would probably have to have a kind of mash-up design between the auger and conical or asymmetrical RC design.

There may also be other ways of designing the bottom to avoid that issue.

I think its definitely still an interesting and very viable design concept.
why not... simpler turn it into a Gene style machine, by rotating RC 90 degrees... all problems solved :)
I bet others will arise Grin

While we are joking here, I want to show you a machine very inspiring for me, due to the way how the Archimedes screw was been used to recirculate beans in an oblique oven having some ... xx degrees slope.

I love the way how the beans are continuously exposed to ambient, as you are permanently push and pull a tray Grin

One day maybe I will reproduce this concept in a glass chamber, with hot air.
Challenge ? Grin
So I've been looking around at augers to see if/how they could be implemented into a new design and a question arose in my mind...

What would be a minimum diameter width for an auger to be effective? Obviously, it is dependent upon the diameter of the RC but for example in a bake-a-around (4") diameter would a 2.5" auger agitate enough to justify working it into a design???
Nesco auger is less than half of RC diameter, me thinks... so 2.5 of 4... should be
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