Whats wrong w/ my stir plate?

So i just finished up a DIY stirplate project and i am having trouble getting the bar to spin right. Instead of spinning about the center like a propeller, the best i can get with the flask as close to the fan as possible is the stir bar spinning with the fan. Kind of looping around the center of the fan like the moon would rotate around the earth(if you get what i mean) If i run it faster it will just fly off because of the centrifugal force. I tried spacing the flask farther away from the magnet by stacking some thin CD cases underneath with no success.

I have two rare earth magnets mounted on a 120mm fan. One side is N up, other S up. They are spaced roughly 1-1.5" apart from the center of the fan. I am trying to spin a 1" magnet

Any suggestions on how to trouble shoot this? I am guessing it may be something with the magnet placement.

Thanks for the help all

What voltage are you running?

I have an adjustable power supply. I tried running at 6 and 12, but i can go down to 3. I am also using a voltage regulator circuit with pot to adjust fan speed.

Stack the magnets on top of each other.

Bingo, the "single" magnet (stacking the two instead of having two on the fan hub) did the trick.

Thanks!

I could not get a single straight bar magnet to stir. I had to buy a magnet that is made like an X. It worked perfect. Good Luck.