Air raid siren

Impeller V5 suitable for 2.2+- mm motor shaft. This might need proprietary treatment. Use 3mm screw if needed to widen hole. This provides a snug fit and reliable connection between the rotor and motor shaft.
If friction occurs between the top of the rotor and the top half casing, use sand paper to remove any imperfections.
Motor secured with small 2mm machine screws.
Casing secured with 3mm machine screws.

Thanks.