Homeroasters - Home Roasting Coffee Community » BUILDING A ROASTER » Fluidbed Roaster
Who is here? 1 guest(s)
 Print Thread
2 lb Fluidbed Build
allenb
Top  #1 Print Post
Posted on 04/08/2023 10:07 AM
Until I possibly stumble on a successful bubblebed design, I'm going to build a 2 lb standard fluidbed using an asymmetrical bottomed 4" diameter aluminum tube. I've got the vacuum blower and 3kw heating element ready to go.

I've never built one this large before so if anyone has any wisdom to share for the build, please jump in and fire away. Is 4" diameter large enough for 2 lbs (.9 kg)? Roasterob seemed to favor this size chamber for this batch size to allow least kw per lb of beans.
I tried to reach him for comment but his email address is no longer valid. On that note, if anyone has contact info for him, let me know.
Edited by allenb on 04/08/2023 11:19 AM
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
greencardigan
Top  #2 Print Post
Posted on 04/10/2023 7:50 PM
Is that a 2 lb green mass?

I've only experimented briefly with an asymmetrical air roasters in the early stages of my building journey. So not sure how much assistance I can be. Although I've built 2 largish symmetrical spouting air roasters, 3.6kW and 5.4kW. I also had some input into my brother's 7.2kW roaster. All had > 4" diameter roast chambers. But I understand that a asymmetrical design is more efficient at circulating beans.
 
allenb
Top  #3 Print Post
Posted on 04/10/2023 8:57 PM
Yes, 2 lb green. I've been given a tip from another member that 4" is going to be too small and that the green height of 2 lbs in a 4" tube is very tall. With your own experience, what would you shoot for if you were to build one for 2lbs?
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
btreichel
Top  #4 Print Post
Posted on 04/10/2023 11:07 PM
I had one with a 6"diameter that worked well.
 
allenb
Top  #5 Print Post
Posted on 04/11/2023 10:08 AM
Let me know what size batch the 6" worked best with and also, how many kw it took.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
CK
Top  #6 Print Post
Posted on 04/11/2023 1:55 PM
You may have seen this builder's roaster designs already, but here's a link to a video and his channel.
 
greencardigan
Top  #7 Print Post
Posted on 04/11/2023 9:06 PM

Quote

allenb wrote:

Yes, 2 lb green. I've been given a tip from another member that 4" is going to be too small and that the green height of 2 lbs in a 4" tube is very tall. With your own experience, what would you shoot for if you were to build one for 2lbs?


If choosing between 4" and 5" for a symmetrical chamber, I would probably go with 5". However, for an asymmetrical chamber, I'm not so sure.

My 3.6kW symmetrical had a 5" chamber. And if I recall correctly, I typically used around 800g green. My 5.4kW has a 6" chamber and I load 1200g green and usually only need 80% power. Both with no recirculation. And I just checked my 300g 1.8kW symetrical chamber and it's about 3.3" diameter.
Edited by greencardigan on 04/11/2023 9:16 PM
 
allenb
Top  #8 Print Post
Posted on 04/12/2023 10:38 AM
In looking at beanbed height versus diameter cross section, to be somewhat equal which is what all of my previous builds have aimed for , excluding the 1 lbr using the bakearound which I had no choice, the 5" looks to be best of all. From looking at examples of other roasters that had much taller bed depth versus diameter, I don't like the collapsing bed chuffing action that occurs when the beans brown and expand.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
ETomczak
Top  #9 Print Post
Posted on 04/12/2023 11:00 AM
I'm in the process of building a 2lb fluidbed right now, and I ended up going with a 4.7" tube, with an ID of 4.5". I haven't run beans through it yet, but just looking at it makes me think 5" would have been better.

I agree with you in this comment:
"In looking at beanbed height versus diameter cross section, to be somewhat equal which is what all of my previous builds have aimed for..."

I went with a narrower tube just because of availability of materials, but now I'm sort of wishing I tried harder and just found some 5". I'm quite confident that 2lbs of green will circulate very nicely, but I don't know how they will do near the end when they've expanded and lost weight. I'm hoping to have the roaster ready for it's first batch in another 2 or 3 weeks maybe? I can report back when I've done that if you'd like.

But my gut tells me that an ID of around 4.9-5" is the happy spot for 2lb. My original goal was 1kg, but I don't know how that will do with 4.4kw of heat, so this is my first run at it. I can make a second roast chamber quite easily, so if it turns out I have enough heat, and 4.5" ID is feeling too small, I may do that.
 
allenb
Top  #10 Print Post
Posted on 04/12/2023 12:24 PM

Quote

I went with a narrower tube just because of availability of materials, but now I'm sort of wishing I tried harder and just found some 5". I'm quite confident that 2lbs of green will circulate very nicely, but I don't know how they will do near the end when they've expanded and lost weight. I'm hoping to have the roaster ready for it's first batch in another 2 or 3 weeks maybe? I can report back when I've done that if you'd like.


Yes, please report back when you've been able to test it. I am in no big hurry at this point.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
ETomczak
Top  #11 Print Post
Posted on 04/20/2023 9:48 AM
Allen,
Ok, first off I realized you were asking about an asymmetrical chamber. Mine is symmetrical. So maybe this isn't applicable.

However, I did do my first roast, and the chamber unfortunately did pretty poorly :( The beans circulated perfectly as green, but as soon as the drying phase the bean spout wandered to the side (actually acting more like an asymmectrical roaster). By the time it was done roasting, the beans were chuffing pretty badly.

Again, this is a symmetrical chamber, so probably not applicable to your design. Sorry about that. I am going to build a second chamber now, probably 5.5" or so, since that is what the material I have available works for.
 
allenb
Top  #12 Print Post
Posted on 04/20/2023 5:58 PM
Sorry to hear the RC didn't work out. But, as I'm sure you're aware, the hot air entry point opening diameter and perf hole size and spacing can totally change how a given chamber performs and can cause what you're experiencing. Too small of an opening can cause chuffing even with a properly sized RC diameter.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
ETomczak
Top  #13 Print Post
Posted on 04/25/2023 10:18 AM
Allen, yes, I might experiment with some entry point diameter changes and maybe play around with different perforated plate, but the reality is this chamber is just too small for 2lbs. That amount of roasted coffee takes up way too much space in there. The chamber is already 19 inches high, and when 2 lbs is fully roasted, it's taking up almost half the space with no air flowing. Just a little air flow, and it's already reaching for the top.

I think it could work ok with 1.5lbs, or maybe a little less. So I will roast 1.5lbs and then use that roasted batch to play around with some specs. I think a narrower hot air entry hole could help a lot, that's my gut feeling. I'm not honestly convinced that changing the perf holes would do much, but I designed it so that part of the chamber is easily interchangeable, so I may try some pieces of the other perf plate I have here.

I don't want to hijack your thread though, you were asking about asymmectical chambers, and mine is a regular center bean spout style. I was planning on starting a thread for my new roaster anyway, I'll do that.
 
HarryDog
Top  #14 Print Post
Posted on 09/08/2023 2:02 PM
The rock sorting machine has nice bean movement, might make a good plate for a bubble bed design? Thought of this thread when I saw it in action. Was wondering if this is done with air or bouncing the table or both?

https://www.youtu...sljTqQVung
Edited by HarryDog on 09/08/2023 2:10 PM
 
allenb
Top  #15 Print Post
Posted on 09/08/2023 7:38 PM
Looks like the same vibratory bed action seen on portioning machines that are used for portioning/filling coffee bags. They utilize a solenoid type vibrator that vibrates the platform allowing product to flow along from the hopper, across the vibrating bed and into the next stage. My guess is that they use this technology for separating rocks from roasted beans prior to packaging. The rocks don't move forward like the lighter beans and can be removed from the screen once the coffee has passed through.

As for using this for bean agitation for roasting, back in the 1990's there was a small, 100 gram vibratory bed infrared roaster built and sold by a guy in Schmittweiler Germany by the name of Hans J Damm and called his invention the Damm Kaffeerostsysteme. I saw him demonstrate it at a coffee trade show in Denver Colorado and seemed to work nice although it was loud due to the solenoid actuated vibrating bed at 60hz USA alternating current frequency.

I don't think you would achieve nearly enough agitation for anything deeper than 1/2" or so.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
HarryDog
Top  #16 Print Post
Posted on 09/09/2023 3:04 AM
I have not seen a de-stoner in real life so was not sure of the tech used, I did like how the beans were moving.
 
renatoa
Top  #17 Print Post
Posted on 09/09/2023 3:53 AM
One of the lightest stone, a variation of limestone, has 4 times bigger density than the medium roasted coffee, so a properly tuned airflow would carry the beans away while leaving the stones in the sieve.
This is a typical destoner principle.
You can build yourself one, using a vac cleaner, as described in this thread: https://homeroast...post_75082
 
Jump to Forum: