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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!

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

· 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

· 03/25/2020 11:49 AM
New Rochelle in the news. I think of you every time I hear it. ... Please stay safe.

· 03/21/2020 7:36 AM
Good morning homeroasters morning Everyone is hopefully staying healthy through this. Hang in there and stay safe!

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Small Batch (100-250g) fluid bed roaster fan question

Sorry this is a crosspost from coffeesnobs. I wanted to post here, but the account I made a few month back never got activated and I had all but given up. But not it works :-)

I've been already reading a lot here but I'm still a bit hazy about the details of the fan, especially concerning my small batch sizes.

So here it goes:

I'm planning on building a fluid bed roaster for small batches of 100- 250g.

To keep it simple my roasting chamber will be the top from a cocktail shaker with a pyrex glas tube attached with oven-silicone. The Tube will have an outer diameter of 80mm and a length of 200mm (since this is the largest I can get).

As a heating element I plan to use the heating element from a hot air gun at around 1600W. This will be encased in a glass or steel tube as well. And since the spout of the cocktail shaker is small enough I plan to stick the roast chamber just into it.
Temperature control will be done by arduino and PID.

Now the Fan-question: I see lots of people using vacuum motor fans or leaf blower fans, but they are a bit overpowered for my 100-250g of coffee. I read somewhere that a minimum static pressure of 2"H2O is necessary to get small batches of beans moving, so I took a look at digikey for 2 Fans:

They are both quite similiar apart from the size. They both provide a static pressure of ~ 5"H2O at a flow-rate of 56 or 130 CFM. However I have no idea on how to calculate which flow-rate is suitable or if 5" H20 is enough.
If it helps, I calculated that the intake for my roastchamber will be 238mm² --> 19 holes 4mm dia. each.

Thanks for the help :-) Currently I'm using an IRoast2 and I thought that motor doesn't seem so powerful and still gets the job done. That's why I'm looking into smaller fan blowers in the first place.
Edited by JackH on 06/08/2017 4:53 PM
Look for an air pump for inflating air beds and such, should work perfectly. That's what I am using for my build.
Welcome to Homeroasters Rudgas! Glad you made it on board.

Some things to be aware of on blowers for fluidbed roasters. Different designs require higher or lower static pressures. The designs where the bottom perforated plate are the same diameter as the roast chamber (Sonofresco, Freshroast) are able to move beans using a relatively low static pressure (usually lower than 10").
This style of roast chamber produces a random bean movement resembling a boiling motion rather than a spouting stream of beans.
The Iroast is also able to spout beans using lower static pressure due to a design where the column height is fairly low and uses a deflector to distribute the beans towards the perimeter.

The classic spouted bed fluidbed requires much more static pressure than the fans you've linked to due to the much taller column of beans its required to lift. The safe bet for this style of roast chamber is the good ole vacuum blower.

Keep us posted on your progress!

Oh, the second item you linked to should not be considered for any type of fluidbed.

1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
Thanks for the replys!

Could you elaborate as to why the second fan wouldn't work? Seems to me all the variables are there.

Great idea with the airbed pump! I ordered one for 12V so I can easily control it via arduino.
This video shows one of my experiments based on using a popcorn heater with a much powerful blower.

The RC diameter is 7 cm, the bean mass is half pound, and the blower use the same chamber as the popcorn, but replaced the motor and the fan from a 75W inflatable air bed pump.
No heat applied, the RC is plastic from a PET bottle.
DIY: TO based IR to bean 750g
Moded commercial: Dieckmann RoestMeister, Nesco, popcorn.
TC4ESP, PID controllers, MS6514 USB/Artisan/Apps
Grinder: MBK Feldgrind, mod'ed Porlex to 47 conical burrs, vintage PeDe Dienes


Could you elaborate as to why the second fan wouldn't work? Seems to me all the variables are there.

Well, I assumed this was just another typical muffin fan that couldn't possibly produce more than a half an inch static at rated flow but I was wrong.
After looking at this fans datasheet, it is able to produce close to 5" static pressure at sufficient cfm by running at up to 12,000 rpm. One datasheet showed that it has two fan blades running counter to each other.

Not sure if 5" static would be enough even for a Sonofresco style roast chamber but could possibly work

I would evaluate the datasheet on this one. I couldn't tell if it requires a PWM input to run or if it is optional.

1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
Thanks again for the replies. Since an airbed pump is cheaper in any case there is no point for me trying the high speed fan at the moment.

I also jumped the gun on a LaPavoni pro so my coffeemoney is a bit exhausted at the moment. Will get back here with news in a couple of month!
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