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-   -   My shamelessly cheap $12 DIY stir plate (http://www.homebrewtalk.com/f51/my-shamelessly-cheap-12-diy-stir-plate-338695/)

CS223 06-30-2012 03:22 AM

My shamelessly cheap $12 DIY stir plate
Thanks to Flomaster and his thread

I picked up a Thermatake USB desk fan from Amazon

It's a 3" fan with a retracting USB power cord and a speed control.


The first thing I did was take it apart. Removed the 4 screws and the little stand. I moved the screws around to serve as legs & swapped sides with the fan guards.


I took the guard with the Thermatake logo and cut the center out by clipping the 4 wires. In retrospect, I wish I had used the other guard instead as it would have allowed the magnet to be a little closer to the flask as it is offset less, not that it mattered. Just a minor detail.

Next I scrounged a fender washer from the junk box, I peeled the label off the fan hub, cleaned the hub & washer with solvent and set the washer in place. I gently spun the fan with my finger and eyeballed the washer to center it. It didn't take long nudging and spinning to get it where it was centered with no visible runout. At that point I dropped some super glue into the center of the washer and let it set.

The washer is important to shield the motor from the effects of the strong magnet. If you don't use a washer, then you need to space the magnet(s) some distance away to prevent them from interacting with the magnetic field of the motor.

While the glue was setting, I tore apart a 3-1/2" HDD to rob the magnet from it. I could have used some spiffy disk magnets but I didn't have any and I'm cheap and wasn't about to spend $10 on magnets. I liberated the magnet from the HDD & cleaned the old adhesive from it.

I placed the magnet on the washer and used a 6" machinist scale to get it centered on one axis, I put the stir bar on the magnet and found it's neutral happy spot. I then nudged the magnet in the other axis until the stir bar was centered on the fan axis. All this was done by eye and by gently spinning the fan by hand.

Once I was satisfied with the magnet position, I put a bead of superglue around the magnet and let it set.


I scrounged a few 6-32 screws and attached the cut out fan guard to the top and that was it.

I used my iPhone wall charger, set the flask directly on the guard and away it went. I need to find some rubber feet/caps to go on the end of the screws to keep from scratching the counter, maybe some caps used for spare ports on aquarium air lines should work. It's a nice compact, easy to stow stir plate, my storage space is very limited. The 1L flask was from Stirstarters.com $12 delivered.


Here's it's chugging away with some washed US-05 in 800ml of DME


Thanks Flomaster and thanks Homebrewtalk!


Indianhead_Brewer 06-30-2012 02:25 PM

Very nice! That is the cheapest stir plate I have seen.....just my style. At $11.73 plus free shipping if you order $25 or more from Amazon how can you go wrong? For another $14.28 I can order a 2000mL borosilicate Erlenmeyer flask from Amazon and get my order over that $25 threshold to get free shipping. With all the old usb cell phone chargers we have lying around the house I am set for my power supply, but if I didn't there are tons USB wall chargers for cheap on Amazon too. Yeast starters here I come!

ghoti 06-30-2012 03:41 PM

What size stir bar are you using ?

CS223 06-30-2012 07:04 PM


Originally Posted by ghoti (Post 4215223)
What size stir bar are you using ?

1" Stir bar that my LHBS carries. Works great for my 1L flask. It should handle a 1.5" as well.

ARKAY 06-30-2012 07:48 PM

Nice! What's nice about this is that you don't have much work to do other than mount the magnet AND you have speed control :) For my fist stir plate I just harvested a pc fan and slapped it on a variable transformer, both of which were dumpster parts. This is much cleaner!

0202 06-30-2012 07:51 PM

I'm wondering how long the fan will tolerate this, but that is awesome.

redcoloredrum 07-01-2012 11:05 PM

Slowly building my DIY homebrew arsenal. This is my next project :)

conpewter 07-01-2012 11:45 PM

I like it! Pretty easy build, already has speed control. Price is great. Would read again A++

rmaloney86 07-02-2012 01:25 AM

I have to do this one, very simple

WuAnquo77 07-02-2012 02:00 AM

Simplicity is a thing of beauty!

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