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Fans - Fluid bed Roasters
If you do go the heater element pre fab route as mentioned above, make sure you pay attention to the voltage so you don't end up with a 220 Volt element being fed from 115. The watts just don't quite add up that way Grin

Bean there Done that, donated the T-shirt to the Church of the Second crack.... St Beanyface

good find:

>In particular, check out the heat blower elements that are 14 Amp (1A505) and 18 Amp (1A506).<

I think I'll order a 1A506.

I'm cogitating about how to configure and machine a volute for the fan (someday I'll have a small CNC mill). When I solve this it should allow 'folding' the fan assembly 180? and place it alongside the heater / roast chamber housing. I wish I could find some good information on how to size the volute correctly vs flow rate etc.

In the mean time I'm going to work on cobbling together the larger removable roast chamber and configuring the larger heater. I still think that if configured correctly the heater could present much less flow restriction and allow the fan to run slower (and quieter). buying a pre-sized heater will help - I may find that I'll remove the coil from its fixture and come up with a new geometry for it.

Down the road after everything is functional I will address some heat recovery and hopefully that will get things back below 1500 watt power drain. I was surprised how little heat I had to add with the heat gun to finish the roast - made me feel positive about heat recovery / recirc.

BTW, I've driven the fan 'direct drive' with a brushless DC motor with success. Used a variac and bridge rectifier / capacitor for power supply with variable speed. It cut out a fair amount of noise associated with the step pulley arrangement and, of course, good speed control. It is a shame that these things are so expensive if purchased new. The stuff I'm using is fairly reasonable from surplus or Ebay sellers - unfortunately this is not conducive to replicating the machine if it is successful.

All in all - I'm pretty happy with the progress. And I get an occasional, really good belly laugh when I look at the assembly and then look at the 'Ubber Popper'. If I keep going this way I'll need a two wheel trailer to move the thing - - it keeps getting bigger. ;)

Yes - just a lighter shade of blond - I like that - we ought to write a song.

Edited by Mike on 05/14/2006 12:57 PM
Look great Mike.

Thinking about your prototype roast chamber, do you think you'll have to change placement of TC or adjust your profiles when you get it in place?


I'm planning on the TC probe going up through the bottom of the removable roast chamber so the probe will stay with the assembly and allow the chamber to be lifted up and out of the fan/heater/control/housing assembly.......most of this is in my dreams, so far.

I'm sure I'll have do to some program manipulation if I drive this thing with a PID. The Fuji does a good learning trick on its own. My actual roasting profile is pretty much of a fluid thing - different beans, different blends etc. I learn a few new tricks periodically (I always listen to Les ;) ). I would expect the new machine to give me the same roast as I get from my 'Ubber Popper'.

If everything works out (and I live long enough ) , the advantages should be:
Quieter - easier to hear 2nd, two to three times the roast quantity, Removable roast chamber assembly - instead of having to man-handle the whole machine when 'dumping' the roast,
In-machine cooling - as quick as collandar/fan (target 2.5 minutes to ambient),
Single housing in a kitchen friendly configuration,
Possible heat recovery/recirc,
got an idea for chaff collection
etc. etc. etc.

I'm trying to modularize the effort. This fan module has taught me a lot so far, and I'm going to have to revisit it. I've got a little bit done, or at least some fairly detailed plans for each of the other modules. And I'm sure that everything will have to go through some changes when I try to do a final blend of bringing everything together.

I know I'm getting awful anal about this effort, but what the hell.. Shock ..I'm enjoying it, and learning a lot.

Edited by Mike on 05/15/2006 10:55 PM


Mike wrote:

I know I'm getting awful anal about this effort, but what the hell.. Shock ..I'm enjoying it, and learning a lot.

Nothing wrong with that. You mentioned CNC, and that plus this comment reminded me of this:

Look at the post from Planeman on 10/15 at 1:20pm. I saw a little of myself in that. ;-)
I'm afraid I'd get so far into the CNC project itself, that I'd never get anything else done. Buying a machine rather than building one is well outside of my budget.


No joke, from what I've seen building a CNC mill can become a hobby in itself. And I think probably most of us have too many of those already. I've thought to build one to automate some of my woodworking, but am reluctant to start for just that reason. But to play the devil on your shoulder, with your skills and a few hundred bucks I'm sure you could build a killer mill. I have some plans...


I've got my shop sort of organized around these little plastic containers with clip on lids that are about twice the size of a shoe box. I've got four of those boxes full of various stepper motors, stepper controllers, ball screws and nuts and other bits and pieces oriented toward that project. Just like everything else - - few hundred bucks is just enough to get you going.

If I could just finish up a few of the other projects first. I've got a couple of roaster projects that I really want to finish - - and Peter just came up with another killer idea that has me intriqued. After that I've got an espresso machine idea that keeps percolating somewhere behind my frontal lobes.

If you ever abandon the idea altogether let me know, I may be interested in buying your steppers, screws, nuts and controllers. Just trying to be helpful of course... ;-)
Mike, I worked on centrifugal pump project for Goulds way back when. The formulas for them are not for the faint of heart. The rule of thumb, the engineers said, was that vane height determines flow and wheel diameter controls pressure, all else being equal.

Here is a motor thought. Direct drive using a 3-phase motor controlled by a VFD. If the VFD is set to, say 300 Hz, then the motor rpm is 5 times 1725. :)

Besides quiet, you get variable speed, too. VFD output can be tied to an input, too. For instance, a PID could control the motor speed. Or, two inductive or photoelectric sensors -- set to peer into the chimney at two different heights -- could keep the beans spount 'this high' but not 'that high'.

>vane height determines flow and wheel diameter controls pressure, all else being equal<

I, also, got involved in a pump project with the Navy during a previous life. These 'rules of thumb' meet my recollections, and what experience I've gleaned from this current project.

The piece of this pie that is alluding me is the Volute. I wasn't the one doing the design during the pump project but if I remember correctly the volute was pretty straight forward. Uncompressable liquid meant to design the size of the Volute discharge to handle the flow rate at whatever the impeller math (based on impeller size and speed) gave you, coupled with the speed of flow you wanted to see in the discharge plumbing. The product of all this gave a pump discharge cross section, so the volute was just a product of collapsing that cross section to 0 through the 360 degree pump rotation. My part of the project started at the pump discharge flange. I'm sure the pump part wasn't as simple as I just described, but it seemed like the guys doing the pump stuff had some 'canned' math that they could throw at the variables.

I'm pretty confident that I could put together some kind of a test rig to do some Bernoulli stuff and come up with flow rate perameters within which my roast chamber will do what I want. This effort would be time consuming but if it would get me to where I want to be I would do it. The trouble is I don't have a hint of how I would use this info to help me design the Volute. I find it hard to believe that folks doing this kind of thing professionally are just saying 'why don't we have a 2" Volute discharge" and engineering from there. All of that not withstanding, it is what I am prepared to do next with the fan, lacking a better focus on the Volute thing. If I am going to 'fold' this thing into a configuration with a reasonable size and footprint, the volute thing is necessary.

I like the VFD idea, it would certainly simplify the mechanical side of this thing. A little bit (underlined little) of reading is making me think that a guy could drive a single phase sychronous motor with a VFD. Am I incorrect here? It seems as though small fractional HP 3 phase motors in the 1/5th HP and smaller range are pretty dear ($). My seat of the pants figuring keeps telling me that 1/5 HP is the range of power I'll need for the fan if I'm not dealing with the losses associated with countershafts, pulleys and belts.

Edited by Mike on 05/18/2006 1:26 PM
I'm working on the heater cartridge. This thread is about the fan, so what is the heater doing here. In the P1 the air is forced through a thin (less than 1/4" wide) slot around the periphery of the ceramic heater, the nichrome heater element is coiled around a ceramic piece and wedged in between it and the roast chamber casting with a piece of mica sheet in place to keep it from shorting to the metal casting. This arrangement works well but it presents the air flow with a lot of resistance. This resistance requires the fan to turn quite fast to provide the necessary pressure to overcome it, as well as the other flow restrictions in the air path. I am trying to design this roaster to present as little air flow restriction as possible. This should allow the fan to provide the necessary flow at a lower speed. A lower speed fan will require a less powerful motor and may allow turning the fan directly from the motor shaft without using sheaves and belts to increase the fan speed above that of the motor. If I can accomplish this it should also drastically reduce the noise of the roaster - which is a primary focus of this project.

To reduce resistance to air flow a less restrictive flow path past the heater is necessary. The flow cross section past the heater in a P1 is approximately 3 in^2, the cross section past the new heater will be approximately 7.8 in^2. In a P1 the air is forced through a complete 180 degree change in direction after passing through the heater and before taking another 90 degree change in direction as it is forced through the slots in the side of the roast chamber. I hope to affect the air flow in a fashion to reduce these resistance producing changes in direction also.

A challenge to this heater is transferring the heat to the rapidly moving air. In the P1 heater the air is forced directly through the heating coil ensuring good heat transfer. The new heater will have three heating coils placed in close proximity to each other and the inner and outer structural pieces. The coils have to be far enough from each other to keep from the shorting that would result from touching each other. The previous step of this project presented the need for more heat than the P1s 1400 Watts (the other 100 Watts is the fan) to complete the roast. Better control of the air flow may affect this. The initial testing of this heater will be accomplished with approximately the same air flow as the last test. Decreased air resistance may allow for a slower fan but the air flow should be pretty much the same (what is necessary to loft the beans). The new heater will provide 1800 Watts.

The following composite picture shows the steps I went through to construct the heater. I made a mold from aluminum plate and cast the insulator ceramic pieces. Drilling them to allow threading the nichrome coil through was a PIA, destroyed half of them. A better way would be to cast the holes into the slip as it is cast - live and learn. I then had them fired by a local ceramics shop. Nice guy at the shop, he charged a whole dollar to fire them (put them in with some other pieces he was cooking), and I picked his brain pretty well so my next pieces will be a lot better quality. I machined the central piece out of aluminum, machined in slots to hold the ceramic pieces and put just a dab of red high temp RTV in the slots to hold everything together while I thread the nichrome. The holes in the ceramic shrunk during drying and firing a bit more than I planned for so threading the heating element was another Royal PIA. I had to heat and cool it several times to anneal (soften) it and twist it a little tighter to reduce the diameter of the coil......then it doesn't end up being very pretty. Oh Well - it is only a prototype.....I'll know better next time. pics/Heater%20002.jpg

This picture is putting it together and the first heater test - worked OK......a lot of heat. Current draw indicates between 1700 and 1800 Watts. I will machine a separator for the top and bottom and can the heater between them with thin sheet metal around the outside between the separators. This 'cartridge' will leave 1/2" clearance around the outside for some insulation between it and the aluminum tube between the fan exhaust and the roast chamber. pics/Heater%20003.jpg
Edited by Mike on 08/21/2007 10:41 AM
That's a beaut! I like your billet approach. I never would have thought to slip-cast and fire my own ceramic parts. I'll keep that in mind. I have an electric heat treat furnace that I could use, too. Don't forget to get some high-temp wire. I get mine from

Have you run into a supplier for the high temperature insulation 'tubing'? The woven stuff that you can slide over a piece of hard single conductor wire.

I found it at the link you provided above. http://www.infrar...eeving.htm

I used to have a little kiln that I used for burning out investments when doing lost wax casting. It would have been perfect for the ceramic parts. Unfortunately it has disappeared.


Edited by Mike on 05/25/2006 12:18 PM
If you are in need of a good yet affordable kiln. Try this place.


This is just one model they have and you can call them on the phone and discuss exactly what you may need.

I needed a kiln for my precious metals recycling I do to pour ingots, and this one did just perfect for me.

Im sure you could make it work for your purpose too.
Edited by Mike on 05/25/2006 5:53 PM
Bean there Done that, donated the T-shirt to the Church of the Second crack.... St Beanyface

Thanks, Good link (BTW I edited your post and made the link active). They make a smaller unit that will fit my needs perfectly:


If I get to the point of needing to do any quantity at all this smaller kiln has a 6"x6"x6" inside and would be just right.

Edited by Mike on 05/25/2006 5:54 PM

I spaced your previous comments (upthread allmost a page) about 'Y' connection heat recovery and 'can the fan take the heat?'. Sorry.

The fan in its current configuration is all metal except for the return (static impeller) between the first and second stages, so inlet temperature will be limited by what would melt this plastic piece. I'm confident it will stand up under temps up to 212? F. I boiled everything in a solution of TSP when cleaning it up prior to assembly.

The 'Y' in the exhaust would probably work. But--I would be introducing a certain amount of vaporized oils, chaff etc. that would foul the fan sooner or later. Dan and I were discussing a similar heat recovery idea earlier. Our ideas ended up with an easily dis-assembled (for cleaning) double sided heat sink (copper plate with fins on both sides), exhaust flow and inlet flow seperated to one on each side of the heat sink. When I get considerably further down the road with this project, I am going to try it.

Edited by Mike on 05/28/2006 1:29 PM
Mike, I was going to give you a url for ceramic spacers but my roaster pictures thread has been decimated :(
When I bought the furnace insulation I got some insulators for just pennies s:2
Okay a quick search led me here:
What Dan said ;) s:1 s:2
They seem to carry everything!
Type "ceramic insulators" in the box.
It should lead you there.

When I bought mine there was a large selection of different sizes, but I can not find that page quickly.s:8s:8

Hope this helps.

PeterZ c:3
Edited by peterz on 05/28/2006 2:37 PM
This may be it! Grins:2


Thanks, they seem to have a pretty good selection.

Doing the slip-cast and firing the little insulators I used is the first time I've ever dabbled in ceramics (underlined dabble). Pretty neat medium. I keep thinking about the capabilities the addition of ceramics makes to the arsenal of construction techniques. It may be possible for me to make the whole heater section with a couple of ceramic pieces that fit together. I'm going to wait to see how these things I made hold up to repeated heat-up and cool-down cycling. What I have now will facilitate continueing the project without major modification to the heater at this time (I hope).

As is probably obvious, to anyone who has followed this thread, I have to guard against getting lost in the technical minutiae of my projects. This ceramics thing looks tremendously interesting, If I'm not careful I'll be making book ends and planters and will have forgotten the real project.

Edited by Mike on 05/28/2006 4:25 PM
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