This week, we tested out our magnetic stirring mechanism for the first time. Initially, we were worried that the magnet may interfere with the movement of the cooling fan.

Cooling fans typically use brushless DC motors, which rely on electromagnetic fields to function. Adding a magnet close to or on the fan could interfere with these fields, disrupting the motor’s operation. Thus, the fan might struggle to rotate or could stop entirely. Additionally, placing a magnet on the fan can add uneven weight or increase friction on the fan’s axis, which can slow down or stop the rotation, depending on the magnet’s size and positioning.

For this, we had thought of a potential solution: Gasket tape. With some research, we found that gasket tape could potentially reduce electromagnetic interference with the motor’s core, and even reduce the effect of the magnet’s weight on the fan blades by absorbing some of the added load, allowing the fan to rotate more smoothly.
However, our fans surprisingly still worked! We chalked it up to the motor’s design and power being resilient enough to overcome the added weight and any potential electromagnetic interference from the magnet.
Then, we found that our stirring mechanism only worked, i.e. our stir bar only spun, when our round neodymium magnet was placed vertically. Some research taught us that this was to do with rotational symmetry of magnetic field alignment and rotational symmetry.
When our magnet is placed vertically, the north and south poles were made to be aligned with the axis of rotation. This alignment helped create a stable magnetic field that effectively coupled with the magnetic stir bar. However, when the magnet was placed horizontally, the field alignment was inconsistent with the rotational direction, causing weaker or no coupling with the stir bar.

To support the magnet in this rather unsteady orientation, we turned to superglue. We thus piped out a bed of glue onto the center of each fan, before firmly securing our magnets to the fans. This managed to hold our magnets firmly in the proper orientation.