Whistle rocket mix
From PyroGuide
Whistle rocket mix is a general term to refer to any pyrotechnic composition that emits a whistling sound when pressed into a tube and ignited. Whistle mix tends to be very fast burning in a loose state; therefore it is also used as burst charge in small shells. It is friction/impact sensitive and should never be rammed/compacted with a rammer and hammer, only pressed. To work correctly, it needs to be very fine, mixed thoroughly and solidly compressed into a thick walled tube and filled about half full. The remaining half of the tube acts as a resonating cavity, essentially amplifying the whistle sound. There are two compositions that can be used to make whistle rockets, the more powerful of the two being the salicylate mix.
Tutorial
Compositions
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Method
Grind the potassium perchlorate by itself in a mortar and pestle or coffee grinder until it is a very fine powder. The same needs to be done to the sodium benzoate or sodium salicylate (depending on the mix you are making) and red iron oxide. Remember both chemicals need to be very fine, like talcum powder and never grind them together. It is a very high-energy mix and burns extremely fast. Screen the chemicals together by passing the mixture several times through a mesh screen. Once you have done this put the mix into a clip seal bag and close it. Gently shake the mix together until the formula is mixed very well. Be sure to touch an electrical ground before starting to mix to avoid the possible production of static electricity from friction with the bag. Alternatively, you can mix this composition via screen method if you wish.
Gently melt the petroleum jelly in a beaker on low heat. Make sure no sources of heat or sparks are present before proceeding with the next steps. Remove it from the heat and add about 5 portions of toluene or lacquer thinner--ie. for a 500g batch, melt 20g of petroleum jelly, mix with 80 milliliters of toluene. Make sure the petroleum jelly is still warm, or it won't dissolve very well. Continue stirring until the petroleum jelly has completely dissolved in the solvent used.
Add the clip seal bag of composition to the petroleum jelly and thinner mix. Using a wooden paddle, mix the composition enough to turn it into a thin paste. Stir the mixture until it becomes homogeneous. Spread the composition out in a layer about 1/2" thick on kraft paper over newspapers to dry overnight. It is important that the mixture has thoroughly dried before pressing motors. A slightly damp mix can cause some shrinkage of the propellant grain over a period of days or weeks, causing the rocket to explode when ignited. When the composition has dried overnight, carefully run the mixture through a 20-mesh sieve twice and store in a paper container so that trace amounts of solvent can evaporate. After several days, the mix is ready to press.
Video
Whistle tube - 700k - Example of whistle mix in a small tube.
Whistle rocket - 536k - An example of a small whistle rocket.