Boll Weevil Brewery

For parts, you'll need at least the following:

• Magnet, the stronger the better
• Flask or other flat bottomed container (clear)
• Stir bar (google "purchase stir plate bar")
• Glue
• Frame materials (wood, plastic, whatever you have that's non-ferrous will be best)

You can also get as fancy as you want with this, adding LEDs to show when it's on, on/off switches, variable speed knobs, maybe even a timer and buzzer or something, but all you really need to make it spin electrically is the powersupply and fan. You could also use an AC fan and powersupply, but make sure you match up your powersupply to your fan.

I did add an on/off switch to mine, as well as a red LED. The switch comes in handy, and I like red lights, heh heh.

I've seen some very nice ones on the web that were housed in plexiglass or other clear acrylic panels, but I didn't have any laying around and didn't want to purchase any for this project, so I just made mine out of some scrap wood that I had laying around.  Again, you can use your imagination and get as ghetto or fancy as you want. I went with some neo-ghetto-chic.  :-) 

 As I said earier, I don't think it matters whether your fans and power supplies are AC or DC, but make sure they both match. Computer fans are DC and are usually 12 volts, so if you are planning on salvaging some fans from a local computer shop or repair person, they will most likely be DC so bear that in mind when looking for a power supply. With DC fans, they will usually work with a power supply putting out less than 12 volts. I actually made mine using a 7.5 Volt DC powersupply and it works just fine. The motor will spin slower with a smaller power supply however, so bear this in mind as you are building it. 

When hooking up the fan to the power supply, note that there is usually a red and black wire coming from the fan (see fan picture below). The RED wire is the POSITIVE (+) side and the BLACK is the NEGATIVE (-) side. On the power supply the two wires are usually also easily distinguished, with the positive having a white stripe, white words, or some kind of texture on it. The negative wire is almost always plain and slick, with no texture or writing on it. What I usually do is just hook them up and try them if in doubt. There are only two wires so only two possible combinations. Why spend minutes wondering when you can spend seconds and have the answer!  Your milage may vary though, and if you get killed...don't come crying to me, ok?

Take the magnet and test fit it on the fan, and also test its magnetic orientation to make sure that the stir bar will properly "fit" with it. I originally had this magnet laying flat down on top of the fan rather than standing on edge, but this made the stir bar stand on end in the flask rather than lie down as it should. You can use your hand and hold the magnet under the flask with the stir bar inside and move it around to see when you get it positioned correctly. You want the stir bar to move as your rotate the magnet.

When you know your magnet's orientation, get it as close as possible in the center of the fan whenever you mount it. Just like an automobile tire out of balance, an out of balance fan will vibrate so you want to avoid this as much as possible. With a rectangular magnet like this one and a square computer fan housing, it's a pretty simple thing to measure on all sides and center it. Using a nonmagnetic ruler (wood or plastic) helps keep things to a non-irratiting level, heh heh.

When I mounted it, I used a two part plastic epoxy, but there are numerous glues out there that will do the trick including superglue, contact cements, and general plastic adhesives. I liked the epoxy because it setup quickly so I didn't have to wait several hours or overnight to finish the project, but it also gave me plenty of time to move it around for final adjustments before it completely set up.

Once the glue had cured, I mounted the fan into the housing that I made. I used a very simple design using only 5 boards. I first cut a square for the top (about 5 1/2 inches wide I think) and then cut 4 boards for the sides. I wasn't making a cabinet or anything, so I just did simple butt joints on the ends rather than mitering them. You can again get as fancy or as ghetto as you want here. I cut a hole in the top of the frame a little bigger than the magnet, and was planning on mounting the fan flush against the bottom of the frame so that the magnet was almost flush with the top of the stir plate, but discovered that for some reason if the flask was this close to the magnet the stir bar would not stay centered and would fly all over the place rather then spinning as designed. I first assumed this was a speed issue with the fan and that it was spinning too fast (and it probably was), and made about 3 trips to the local Radio Shack for potentiometers to use to vary the fan speed...but I could never get them to work properly. I did discover though that if I spaced the flask about an inch over the top of the magnet that it would spin perfectly. Go figure.  :-(

In hind sight, there probably doesn't even need to be a hole in the wood now that the magnet is almost at the bottom surface of it, but we live and learn. Here's a shot of the fan mounted on the bottom and also a shot from the top:

Originally I wasn't going to have the "feet" on the frame, but moving the fan away from the bottom of the flask (using some spacers and rubber washers that I had laying around) made the bottom of the fan stick out lower then the bottom of the frame. I had these little wooden plugs left over from another project and took 4 of them and glued them to the bottom. They work pretty good as little bun feet.

I didn't know how any vibrations from the rotating fan would effect the flask, and didn't want it to jiggle off of the edge of the stir plate, so I indented the top of the frame about 3/16 below the edges of the sides just to give it a little bit of edge to help hold things. As it turns out, I got the magnet about spot on and it doesn't vibrate at all. I was also surprised at the sound of the thing when running: there isn't any. This thing could run in a sleeping baby's room.  I have a box of used computer fans and I guess I just got lucky and grabbed a quiet one!

 All of this stuff isn't worth squat if the starter doesn't get stirred I guess, but as they say the proof is in the pudding. So with that said, here's the pudding!

I know that I haven't completly given you blueprints and a point and click shopping list for parts, but this thing is really super easy to build. I figured that anyone needing detailed directions and step by step instructions wasn't really capable of building one in the first place, and anyone that is capable probably will improve upon what I've done anyway, so unfortunately what you see here is what you get!

*burp*