A combination of a radial compressor and an air raid siren.
Produces a loud noise when spun at high speeds.
These settings produced the best parts for me.
After printing sand all parts to ensure a smooth surface and lower friction between parts.
Several pieces will need to be glued together. The 4 scroll parts will need to be glued together as well as the 2 shroud parts.
The design is base off of the combination of a radial compressor and an air raid siren. The theory behind a air raid siren is it uses slats to interrupt airflow out of a rotating fan. This interruption produces sound. The sound is due to the fast changing pressure and the amplitude to the sound is dependent on the magnitude of the pressure difference.
The radial compressor was designed to compress air in a smaller space than a typical axial compressor. The compressor takes air into the blades and accelerates it into the scroll. The scroll gradually expands towards the exit. This expansion converts the velocity energy of the air into pressure energy.
By combining these two theories we get a uniquely designed noise maker. The air accelerates in the blades, to a velocity of approximately 5 m/s, and then is interrupted creating large pressure variations and loud noise. The scroll then directs these pressure waves into a singular direction, while also increasing the pressure and amplifying the sound.
The parts were designed in solidworks and tested to ensure the theory was sound. (that pun was bad)
Test proving the velocity at the exit of the blades was high.
Animation of a velocity pulse exiting the shroud. This is in slow motion.
After completing the post print processes follow these steps to assemble.
- Push parts 1 & 3 together. Glue them if it is not a tight fit. They must rotate together.
- Slide part 5 through the hole in part 4 and press it into part 1. Ensure everything is in the correct orientation.
- Slide part 2 over pat 3 and glue it to part 4 in the ridge (may need fiddling to make it it properly)
- Slide part 6 over part 2 and glue to part 4. You may also glue the upper edge of part 6 to part 2
- slide part 8 through the hole in part 7
- Press part 7 onto part5