Small mechanical siren for nano drone motor

thingiverse

This is a small siren for a toy drone motor (like Cheerson CX-10, 6x12mm round motor with 0.8mm shaft. It could be used for example in some toy police car or fire engine or a small alarm clock. It makes a high-pitched shrill rather than usual siren sound at full loudness, but it can sound more siren-like when rotating slower, only it's not that loud due to lower amount of air being moved. At 3.6V it goes to 92- 94dB measured with my phone in direct proximity to the siren. The siren rotor should be printed flat side down without a raft as it is hard to determine where raft ends and rotor starts otherwise, leading to unbalanced rotor and a lot of sanding for such small part. The stator and the top cap should be printed wide side down for better accuracy. The pipe that holds the stator around the motor is a bit loose so covering the motor shell in a few turns of tape may be needed, and the hole in the rotor sometimes won't print and has to be drilled instead and rotor affixed with epoxy to the shaft. It is easiest ro put the motor in the housing first, then put rotor on it , glue it if necessary and then attach the top with ABS dissolved in acetone, applying it to the top part rather than stator edge. My printer doesn't seem to meet closer tolerances, but if the rotor was ending nearer the stator, the seal would be better so it might be louder. I carefully applied a little ABS juice to the rotor while spinning through the stator hole with a paintbrush to achieve that instead, and kept it spinning for a few minutes afterwards. Then I removed ABS hairs and candy floss-like froth that are a byproduct of doing that and it did get a bit louder and uglier. I may redo it some other day, like improve tolerances or rotor aerodynamic properties so it's louder.