"I guess old age has finally kicked into the grey matter. I kinda thought it was the magnets that were the primary factors, Not air movement!!!"



you were right the first time. Its all about the magnets and nothing to do with air movement.



For clarity, I'll cover the instructable. It is about re-purposing a throwaway old CPU fan into about the cheapest magnetic stirrer that can be found. There is an elongated piece of plastic covering small magnets inside the glass with the solution to be sired, and is spun by the rotating magnetic field from magnets on top of the fan. In the picture with the glass, it is hard to see as anything more than a white blur at the bottom because it is spinning so fast. But, you can easily see the vortex it generated. The actual fan blades serve no purpose in the stirring process except maybe to keep the rotor from spinning too fast.



Side note: Like an unbalanced tire will cause increasing vibrations when spun faster, slightly unbalanced magnets glued to the rotor can cause excessive vibrations if spun too fast like say after cutting the fan blades off so that it is no longer loaded by air resistance, the magnets on top may cause excessive vibrations if it spins faster and there the magnets are not balanced.