Small mechanical siren for nano drone motor

thingiverse

This is a compact siren designed for toy drone motors, similar to the Cheerson CX-10, which uses a 6x12mm round motor with an 0.8mm shaft. It can be used in various applications such as toy police cars or fire engines and even small alarm clocks. The siren produces a high-pitched shrill sound when operating at full loudness but can sound more like a traditional siren when rotating slower, albeit not extremely loud due to reduced airflow. At 3.6V, the siren reaches a measured volume of 92-94dB when placed directly next to my phone. To achieve accurate results, print the siren rotor flat side down without a raft as it can be challenging to determine where the raft ends and the rotor begins, resulting in an unbalanced rotor that requires extensive sanding. The stator and top cap should also be printed with the wide side facing downwards for optimal accuracy. A loose pipe that holds the stator around the motor may require wrapping the motor shell with a few turns of tape to secure it properly. Additionally, the hole in the rotor might not print correctly and needs to be drilled instead; the rotor can then be attached using epoxy to the shaft. For easier assembly, place the motor inside the housing first, followed by attaching the rotor, gluing if necessary, and finally securing the top with a mixture of ABS dissolved in acetone applied to the top part rather than the stator edge. My printer struggles to meet tighter tolerances, but modifying the rotor so that it ends closer to the stator could improve the seal and increase loudness. To achieve this, I applied a small amount of ABS juice to the rotor while spinning through the stator hole using a paintbrush and kept it spinning for several minutes afterwards. This process resulted in a louder siren but also created unsightly ABS hairs and froth-like residue that needed to be removed. In the future, I plan to revisit this project and explore ways to improve tolerances or rotor aerodynamics to increase its loudness even further.