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1lb Fluidbed Roaster Build
I've started over on my fluidbed build to try succeed this time ThumbsUp

In the pictures I've got a vac blower in the boot flowing through a salvaged heat gun element up to the roast chamber. The blower blows and the heater heats. 1st test with beans in the RC showed absolutely no movement in the bean mass.

Am I not getting enough power to the blower? Is my rc to wide? too wide at the exit? are the holes in the silicon too close together to achieve circulation?

Any and all help would be great. Cheer!



Any and all help would be great. Cheer!


I looked at your set up and with no previous experience in a build such as you are attempting, I have a few questions.

You say "with beans in the RC showed no movement" but you do not say how high the bean mass was. I think there will be a relationship between pressure at the inlet and the mass of beans directly above it. If the bean mass column directly above the air inlet weighs more than the area of the inlet times the pressure, then there won't be enough force to lift it.

If you were to plug up the inlet and turn on the motor, the motor would run but the no air would be flowing through the inlet since it is plugged off -- the back pressure would force the air out of other openings. Similarly, if you put a 1/2" thick layer of beans in the RC, they might be blown up readily whereas a 1 foot layer would, in effect, plug off the inlet (or at best allow air to flow in the interstitial voids between the beans.)

So you might evaluate the effectiveness of your blower by starting out with a very light bean charge and then gradually increase it until you see where movement ceases altogether.

Another thing I noticed, unrelated to this, is that even if you were to get good movement up the center of the RC, I think you'll have a relative dead space, movement wise, at the outer edges along the base. I would suggest that you determine the angle of repose for green beans and then make sure the angle of the base from the air inlet upwards to the outer wall of the RC exceeds that angle. That way you would get the beans shooting up the center, moving to the outside circumference, and then sliding back down to eventually move into the central updraft again -- sort of in a toroidal, donut shape. This would not be a fully fluidized bed, but it would be an air-stirred arrangement that could be expected to produce a uniform roast, and by placing the thermocouple nearer the outer edge of the RC, you would get a better indication of bean mass temperature than you might if the thermocouple placement included the hotter column of rising air.

You might also consider picking up an inexpensive anemometer such as the one shown below. By measuring cold air velocity, and converting from your inlet area to the anemometer measurement area, you could determine the extent to which you may be choking off air flow due to back pressure of the bean mass.

So many beans; so little time....
If that small red opening is the bottom I what I assume is the heat gun element, then I see all kinds of problems with your design.

Maybe some of the guys that use heat gun elements will chime in but I don't see how what you are doing there could possibly work. The opening is way too small and restrictive for the size roast chamber you have. Possibly doing something to make it a spouting bed in the center, not sure, but you are definitely in left field from anything I would be doing.
However, I have more of a mindset like Tim Allen in Tool Man, I want power and plenty of it, then I can control it exactly how I want to.

I would suggest forget the heat for now. Work on your design to getting on pound of green beans moving in the roast chamber the way you want. Once you get that, you can figure out a heat source, but for a pound, I don't think it's going to be a heat gun element.
Your roast chamber is too wide! Try a bake-A-Round (3.5" wide)..
What is the blower output? Buy one pound of rice or dried beans and test, test, and test flow before heating..
Provde a bit more detail of the perf chamber. I used a smaller size, three inch, cocktail shaker top..
Edited by oldgearhead on 10/31/2016 7:59 AM
No oil on my beans...
The vac motor blows through the salvaged heat gun element housing. I disconnected the fan and kept the switch to turn the heating element on. The little red thing at the bottom is a silicon strainer/funnel combo I bought off of amazon (https://www.amazo...&psc=1).

It appeared to serve two purposes (1) the funnel would serve as the bottom half of the RC and (2) the silicon would be heat resistant enough and already perforated.

BenKeith are you worried about scorching? I have limited resources and technical skill. Enough to attempt a cobbled together fluidbed roaster with found/cheap parts. I can't weld, wire up complicated designs like many here with engineering knowledge - I'm a theologian after all - trying to learn when it comes to all the scientific attributes of building a roaster cross fingers
...and a two-staged. flow through, blower delivering 90 CFM and 90 inches of H2O (not at the same time)..
Using a rubber perf plate is scary. Use stainless steel..
No oil on my beans...
OGH - what's the issue with the width? I posed this as a potential issue in my original post because I remember reading about it somewhere a while back but can't recall why the wider RC is problematic? The blower I actually bought from you a couple years ago lol (sundance in a boot)
Concern over scorching had nothing to do with my not using the heating element for now. I just said that because you are centering you whole build plan around using it, and it's not right for what you are doing.
I was just suggesting doing what I learned a long time ago, chase one rabbit at the time. Start of by getting your roast chamber so I will move one pound of beans properly.
If you want to use the Coleman globes, get a bottom shaped and a blower sized to what it takes. I don't know anything about the specs of your vacuum motor and it may be fine if you fix the bottom funnel section to let enough air through, and it may be too small for that size chamber.
You may find out the Coleman globe is just too wide and need to get you a Bake-A-Round as suggested to reduce the diameter. I have two Coleman globes a little over 5" in diameter stacked together, a long Pyrex cylinder about 4.25" and a Bake-A-Round to experiment with so I can get the size roast chamber best suited for the one I'm building. However I'm also using my Flow bench for an air source until I get that worked out and that's up to 12 vacuum motors with over 1,200cfm of air. I make my own heating elements and once I get my roast chamber to suit me, I will build me a heating element. I'm hoping to keep it electric but I can build some pretty wicked propane burners also. My game plan it to do one pound and up to two pounds if desired, if it works out.
My problem is I just don't have enough Round-2-it's to get it done. Other things keep getting in the way and since I have a roaster that works fine, it or the drum roaster I'm building are not high priority. My wife thinks getting a 2004 VW Beetle Convertible I bought for he a few weeks ago going is more important right now, and then something else I'm sure will come along.
Your RC needs to be about 2-3x the diameter of the perf plate..
The bower should be fine for up-to 500 grams..
No oil on my beans...


BenKeith wrote:

My wife thinks getting a 2004 VW Beetle Convertible I bought for he a few weeks ago going is more important right now, and then something else I'm sure will come along.

All the best on your build. If you have any questions on the bug, let me know. Just sold my wifes '04 convertible last month. I'm way more familiar than I ever wanted to be. Cheers, Scott
The funnel in the base of the may also be a bit flat. A steeper base will help the beans push back into the central spout.

Although I just remembered that one of my roasters has essentially the same setup with a 5" diameter Coleman tube and jam funnel with a stainless sink strainer in the base. This setup was able to roast about 1kg (2.2 pounds) using 2 x 1800W heat gun elements. The blower was a 900W vacuum cleaner.

Videos of my setup on YouTube here


Edited by greencardigan on 10/31/2016 6:24 PM


CharcoalRoaster wrote:

The vac motor blows through the salvaged heat gun element housing. I disconnected the fan and kept the switch to turn the heating element on. The little red thing at the bottom is a silicon strainer/funnel combo I bought off of amazon (https://www.amazo...&psc=1).

I also would highly recommend using a stainless steel perf plate. I regularly see air temps directly below my perforated plate ranging from 600-1000F.

When the silicone starts melting you will have many other problems on your hands.
So I've made some adjustments to the RC and redesigned the layout of everything to make it more compact and less that 6ft tall ;-)

I bit the bullet and went with a Bakearound which has proved effective as I can easily agitate/loft 1lb of greens. I think I may be able to do 1.5 lbs but haven't tried yet. Furthermore, I've got two heat guns elements that will serve as my heat source so I should have enough heat to roast that capacity.

Unfortunately, I haven't been able to do a full test roast bc between the vac motor, and both heat guns elements I tripped the 15a breaker after 10 seconds of having everything running at once. I plan on installing a larger breaker in my garage to accomodate but am unsure what size to go with. Will 20amp suffice or should I go 30amp just to be safe?
I did I quick calculation: with one 1800watt element at 120 volts, the current draw is 15 amps. So two of this rating will draw30 amps. I have fashioned a connection to the 30 amp dryer outlet in my garage. One hot wire is 120 volts with respect to common. The other is also 120 volts also, so they are 240 volts with respect to each other. So this can be used. Either (both) sides are rated at 30 amps. Still, if you put both heating elements on one side, you will have maxed out the capacity. But if you put one on each side, you will have enough reserve to also run the blower on either of the two circuits.
Bad coffee prevails when good coffee roasters stand by and do nothing.
I used a dryer cord and ran it into a dual circuit 30 amp fuse box.
You could run into overloading problems with the house wiring itself by just increasing the value of the circuit breaker, if your trying to get more out of a 15amp circuit.
Bad coffee prevails when good coffee roasters stand by and do nothing.
It looks like this:
Lawnmowerman attached the following image:

Bad coffee prevails when good coffee roasters stand by and do nothing.
Tried a test batch of 250g a few minutes ago hoping I'd at least be able roast that much before I can install large enough breaker in my garage to handle full capacity of the blower and both heat gun elements. You can see I've got a pretty solid sprouting bed of greens at about 60% power of my variac controlled vac motor.

I had both heat guns blasting for about 7 min before I cut off the roast and called it quits to post a couple of questions. I could feel a 20 min stalled roast coming.

Even at 250g it still seems that I can't draw enough power to get enough heat to achieve a reasonably timed roast?

I stuck a thermocouple down into the bean mass about 5 min in and it was reading around 158* - - so clearly there was some heat transfer occurring and some of the beans were warming up.

For fluidbed builders/users out there do you have a warm up period for your roaster? w/ beans or before beans? Anything else I should/could consider to get things roasting? (pun intended)

JSA Coffee
Without having built a fluid bed roaster myself (yet) I can only answer a question about the power. You need to check the size of the wire that the breaker is feeding before changing out a breaker for a larger size.

A 15 amp circuit typically has 14 gauge wire.
A 20 amp circuit typically has 12 gauge wire.
A dedicated 220v 30 amp circuit can have 10 gauge for intermittent duty.

A limiting factor to your electric elements is the size of the wire feeding it. A smaller wire will heat up, causing resistance if your lucky, or melt the insulation if you are unlucky. Also, make sure you are using the correct outlet for the circuit. A 20 amp outlet has a sideways slot. Drawing too much power from a underrated outlet will eventually make the plastic brittle, causing it to short and trip the breaker if you are lucky, or a fire if you aren't lucky.

If you cannot upgrade the power, due to renting, you might consider searching for a small generator to feed your roaster. You can frequently find generators on Craigslist for a few hundred.
Good action for the drying phase (first 3 minutes). But in the rest of the roast less spout and more bean contact, with each other, would be better. Remember with electric heat the less air flow, equals hotter temperatures. However, if the beans stop moving they will burn.
No oil on my beans...
JSA Coffee has called attention to the problems with electric heat. If you want to run two 120 volt 1800 watt heaters you must go with a 220 volt service. Because at 120 volts your load is 38 amps and on 220 volt service your load is 19 amps (IF you connect the two 120 volt heaters in series)..That is why I choose to re-claim hot air from the RC and run one 1550 watt, 120 volt heater...
No oil on my beans...
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