Speed Posted September 9, 2008 Posted September 9, 2008 Hey guys, I picked up some potassium benzoate and I've been working on making some whistle mix with it. I ground both the k perchlorate and the k benzoate separately in a coffee grinder to a fine powder. I mixed 7 grams of k perc with 3 grams k benz by screening them together and shaking them a bit in a paper cup. In this finally powdered green mix form, it burns vigerously with lots of gas but nearly as fast as my willow meal powder. Perhaps it's just a matter of setting expectations but I expected it to be more reminicient of 7/3 flash rather than commercial airfloat meal powder. The confusing part is many of the videos I've seen seem to show similar speeds that I'm experiencing but many others show a whistle of much higher speeds. Ultimately, I am interested using this as a booster for my small shells in lue of 7/3 flash but it seems way to slow for that. How fast should a green mix like this be and is it usable as a break booster?
FrankRizzo Posted September 9, 2008 Posted September 9, 2008 (edited) A coffee grinder will not bring the benzoate to the fineness that you need for a good whistle mix. Dry the benzoate in an oven @250F for 3 hrs, then ball mill. If you have cab-o-sil, add 0.5% before milling. Separately from the benzoate, ball mill the potassium perchlorate and iron oxide together. As with most pyro compositions, the particle size of the fuel makes a considerable difference in the burn rate. The oxidizer particle size is of secondary importance, and doesn't have as much of an impact. Edit: Oops..thanks Richtee. I mistyped. Edited September 9, 2008 by FrankRizzo
Richtee Posted September 9, 2008 Posted September 9, 2008 As with most pyro compositions, the particle size of the oxidizer makes a considerable difference in the burn rate. The oxidizer particle size is of secondary importance, and doesn't have as much of an impact.Hmmm... fuel particle size matters less?
tentacles Posted September 10, 2008 Posted September 10, 2008 (edited) Speed: You might try ricing the mix, that will make a huge difference in the speed. Look it up to find instructions, as I'd rather not give you the wrong ones. Frank made some whistle with 2% (or was it 5%?) red gum dissolved in alcohol, make the usual ball of comp and then rice through a screen. It worked very very well and made super fast whistle. This might be just the ticket for breaking shells, and the particles will be much more durable than the typical wax or mineral oil riced stuff. Keep in mind the harder particles may/will be more sensistive to friction. I've heard of ricing with NC/acetone as well. But definitely follow Frank's advice and ball mill that fuel at least. If it's in the same particle size as what we have (cottage cheese) then it will need a couple hours in the mill. Edited September 10, 2008 by tentacles
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