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her63
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· 06/02/2020 9:10 AM
keep healthy bro, love roaster form home

pisanoal
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· 05/27/2020 10:14 AM
Anyone else have issues seeing the whole window of a thread when accessing from a mobile phone? Any fixes?

allenb
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· 04/02/2020 4:50 AM
Morning Ed, I haven't done any green coffee hoarding yet but am hoping the supplies don't end up like the toilet paper isles!

snwcmpr
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· 03/31/2020 2:53 PM
Hey Ed. Thanks. roar

homeroaster
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· 03/31/2020 11:21 AM
Hey quarantined home roasters! I hope you have great coffee! If they have a run on coffee, I hope you're set with your great home roast! Find me on Facebook! Ed Needham

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Physics, Pressure, and RC Designs
CharcoalRoaster
Did I trick you with that scientificy sounding subject?! Roflmao

Sorry, I used two big words to catch the attention of people who understand that to help me out with what I hope to be a very simple design question before I weld something I regret/don't need.

On my current 500g capacity build I have a bake-a-round glass RC with funnel/cone shapes on top and bottom and it works out great with 1000+ roasts on that machine. I have two options for this upsized RC build both of which will connect to a cyclonic chaff collector.

#1 Funnel both ends of the RC
#2 Funnel bottom to help with recirculation and flat top

Do both function the same in terms of the physics/pressure associated with a FB roaster? If fabrication were easier on the flat top for me would it be detrimental to me at all?

Thanks!
CharcoalRoaster attached the following image:
rc_1.png
 
btreichel
#1 is better. While you want static pressure to lift the bean mass, you don't want back pressure like #2 would cause.
 
renatoa
What if the cyclone is complemented with a small fan on exit, that helps eliminate the back pressure at all, or maybe, if the fan speed is variable, even allow experiment with various degrees of pressure levels, negative or positive ?
 
CharcoalRoaster

Quote

btreichel wrote:

#1 is better. While you want static pressure to lift the bean mass, you don't want back pressure like #2 would cause.


Thanks for that helpful little tidbit. How much of a convex exit is too much? How little is too little? Do I need another full blown funnel/cone or is a slight convex exit point enough to mitigate back pressure caused by a completely flat top?
 
CharcoalRoaster

Quote

renatoa wrote:

What if the cyclone is complemented with a small fan on exit, that helps eliminate the back pressure at all, or maybe, if the fan speed is variable, even allow experiment with various degrees of pressure levels, negative or positive ?


Small fan on exit of RC or exit of cyclone? I don't plan on recirculating heat for this build so I could include a small fan on the exit of the cyclone. Wouldn't that fan just suck in all the chaff though and eliminate the cyclonic effect altogether?
 
renatoa
Nope, a cyclone can be used in two ways, either pushing pressurised air on input, or pull/sucking from the exit. In both cases the dust/chaff separation is well done.
I guess you mean the chinese aluminium small unit, taht was pictured in some setups here.
Proposed the fan on exit because is how I am using mine on a TO setup, where pressure from the oven is very small, almost nothing. So a pull fan on cyclone exit is required.
Also, this is how almost all production roaster cyclones works, with the suction blower on top of cyclone unit, check this typical model:
https://www.giesencoffeeroasters.eu/r...nalcyclone
 
CharcoalRoaster
Not the small chinese cyclone. I fabricated a larger one to be able to use with this increased capacity RC. I'll have to include a picture but it's at least 20x the cyclone you're referring to if not 30x the size.
 
renatoa
Probably the size of Giesen cyclone from the page linked above Grin
The point remain valid: most production cyclones have motors on top, pulling the air from cyclone, they are not relying on pressure from the oven to push the air into cyclone.

Why do you need the cyclone be so big ? The chinese unit is good for at least 500 grams roasters.
 
CharcoalRoaster
Hoping to get at least 1-2kg for this next RC so I figured I would need a larger cyclone cross fingers

The only problem I can foresee with my cyclone is that it has similar inlet/outlet locations as the smaller one which was the reason for my initial fan location reply question. Would I just mount the fan onto the top of the outlet??? Wouldn't that just suck the chaff into it instead of it swirling to the bottom.

Here's a sketch of what mine looks like. My plan was to just connect something to the outlet on top to carry the exhaust out of the garage while I'm roasting then just place a small catch underneath the chaff exit on the bottom.
CharcoalRoaster attached the following image:
cyclone.png
 
CharcoalRoaster
Nevermind. I went ahead and welded on the other funnel I had. Backpressure shouldn't be a problem cross fingers
 
renatoa
Nope, will not suck the chaff, but... you need the upper central pipe to have a certain length inside the body, at least under input pipe level, as you can see in these various cyclone designs:
https://www.researchgate.net/figure/R..._259101451
 
CharcoalRoaster
Good to know and also interesting Renatoa! One follow up question I have I guess...

On my current roaster my (extreme diy and siliconed together) cyclone works wonderfully but shouldn't, at least according to each of those designs. I guess it looks similar to the very first one that includes the note about it being low-efficiency Roflmao
CharcoalRoaster attached the following image:
cyclone_1.png
 
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