Simple stir plate

thingiverse

This is an extremely simple, incredibly affordable stir plate featuring a 120mm case fan hardwired directly into a 12v power supply. I tore apart some refrigerator magnets and they adhere perfectly without the need for glue. I've been using it with a large stir bar in a 5L Erlenmeyer flask, and I'm confident that this design will work just as well with smaller flasks - you might just need to resize it based on your fan's dimensions so the lip sits just above the magnets.