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Centrifugal TO Roaster build
allenb
In the middle of building a TO roaster using a centrifugal type agitation instead of paddle. Still needs to have the TO top modified to fit the smaller diameter of the pot I used. The drive base is from a standard bread maker. Had to replace the drive shaft with a longer one. RPM is unchanged.



1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
allenb
Forgot to mention, load in video is 1 lb but should be able to handle much more as far as sufficient bean agitation. Not sure how much coffee the 1500 watt TO top will handle.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Koffee Kosmo
I like the idea and would like to see roasting results when they are available

When I did my initial research on coffee roasting principles
The common theme was that the bean mass should remain intact during the agitation process, so the heat transfer should be from both the TO heat source, and stored heat transfer from the beans themselves

Then I chose the appropriate speed and best agitation method that gently pushed, tumbled and worked the beans from the center to the outside continuously while still having occasional pause sections

So I will be watching to see the upcoming roasting test results

KK
I home roast and I like it. Designer of the KKTO
Roaster Build information
https://forum.hom...ad_id=1142

https://docs.goog...lide=id.i0
Blog - http://koffeekosm...gspot.com/

Bezzera Strega, Mazzer Robur Grinder, Pullman Tamper Convex,
(KKTO) Turbo Oven Home Roaster.
 
renatoa

Quote

allenb wrote:

Forgot to mention, load in video is 1 lb but should be able to handle much more as far as sufficient bean agitation. Not sure how much coffee the 1500 watt TO top will handle.


Wow, wow...

One pound surely does. I did 640 grams with 1300 W. But shorter distance from beans to TO, about 8 cm.

Great agitation there, with the cost of increased noise though... eagerly waiting the first roast to hear how FC can be distinguished from that high pitched background ambient.

Also, where goes the chaff ?

Not the last... do you plan to add a dump door in the bottom?
The machine seems big enough to dump beans by tilting.
Edited by renatoa on 11/20/2021 4:30 AM
 
allenb

Quote

Koffee Kosmo wrote:

I like the idea and would like to see roasting results when they are available

When I did my initial research on coffee roasting principles
The common theme was that the bean mass should remain intact during the agitation process, so the heat transfer should be from both the TO heat source, and stored heat transfer from the beans themselves

Then I chose the appropriate speed and best agitation method that gently pushed, tumbled and worked the beans from the center to the outside continuously while still having occasional pause sections

So I will be watching to see the upcoming roasting test results

KK


Hi KK and great observations. Yes, I've read the same regarding heat transfer being optimized by keeping bean to bean contact happening as much as possible while allowing adequate heat access at the same time. With that said, the roaster can be slowed down by going with a variable speed motor drive instead of using the bread maker motor allowing roasting different load sizes. The current setup would probably do better at 2 lbs.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
allenb

Quote

renatoa wrote:

Wow, wow...

One pound surely does. I did 640 grams with 1300 W. But shorter distance from beans to TO, about 8 cm.

Great agitation there, with the cost of increased noise though... eagerly waiting the first roast to hear how FC can be distinguished from that high pitched background ambient.

Also, where goes the chaff ?

Not the last... do you plan to add a dump door in the bottom?
The machine seems big enough to dump beans by tilting.


Good questions Renatoa! Here goes:

Noise: Bigger bean mass is quieter but will need the exterior of the pot insulated with some sound absorbing material to hear 1C.

Chaff exit: Will be incorporating a slit in the pot shell near the bean travel with catch cup hanging on the exterior as Farmroast used with his Dreamroaster.

Dump door will be a hinged flap in the side with angled chute attached to the outside as with a drum roaster. Will just tilt the works upside down for now until concept proves to give acceptable roast results.

I will not be measuring bean temp on this one but only ET.

Pot height will be shortened eventually to only as tall as necessary maximize heat transfer and lessen heat loss through metal skin.
Edited by allenb on 11/20/2021 8:43 AM
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
renatoa
You can use for insulating such tapes, used in motor tuning jobs:
https://www.heats...haust-wrap
or, for fireplaces:
https://www.amazo...01DDKEC02/
 
allenb
Those are some possibilities for noise reduction. Another option would be to use a ceramic pot instead of metal which would not ring/resonate like metal but drilling holes would require carbide tools.

Some history behind this design

Years ago I built a smaller version of the centrifugal bowl roaster. The bowl was basically a small dog food bowl made from carbon steel and had several 1/8" tall vanes placed around the sloped wall to give the beans traction to be slung up and into the stationary turning vanes. I had assumed the sloped walls were necessary in order to effectively move the beans up and into the turning vanes but the current design proved we don't need a bowl and a flat disc is sufficient as the beans will walk up the sides of the pot and easily hit the return vanes. I had used 3 vanes instead of 2 which created less intense velocity and kept beans in closer contact with each other.

A few notes on the current design:

Pot diameter = 10"
Disc is 3/32" thick. (thinner may deflect downward at edges due to bean force near vanes)
Disc vanes (4) are 1/8" tall x 2" long. If using slower rpm, you might need to increase vane height by a small margin.
Some chaff will travel down below disc via gap between disc and pot so leave a cleanout door to vacuum chaff.;

Link to farmroast's dreamroaster with chaff removal slot and cup:
https://homeroast...#post_4485

See posts #7 and 13 for chaff exit slot and cup
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
renatoa
One more design detail that I think deserves a bit of reflection is how the airflow path could interfere with those deflectors.
The airflow coming from the lid is not vertical, but spiraling along the walls, counter clockwise for my lid, as looking from above, no idea if this is an universal standard.
The chaff flying in the oven shows very clear evidence of this descending path, a complete circle spiral is about one inch tall.
Now the question is how this airflow will interfere with the deflectors, and which of two turbulence patterns that will be created in the bottom of the pot would be best for the roasting.

For my roaster I have two different pots, for small and large roasts.
The smaller, for under 250 grams roasts, can be seen in the video below, is partially centrifugal for the push outside action, combined with gravitational return path to center, due to the curved bottom of the pot.



9" outer pan diameter, 60 rpm and half pound greens there.
Need a faster turning motor to experiment some true centrifugal setup.
 
tem3000
Any progress on your TO? It looks really promising! I'm interested in seeing its progress...
 
allenb
Actual physical changes no but have been finalizing dump door design and control strategies along with probe placement so hopefully will be cutting and bolting in the next two weeks and will post video of it in action if all goes well. Like many others, lots of other stuff getting in the way! Shock
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
tem3000
Thanks, that's great! Looking forward to pics as you life's busyness allows. :-)
 
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