SharkWhisperer
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Alrighty, so we dip our igniters, sometimes using a BP slurry in NC. Some folks cover their starters in an NC-only coating to afford additional protection and possibly enhancing flame/heat production. NC burns so fast as guncotton, and is used to propel bullets at a several thousand miles per hour, so this makes intuitive sense. But does it make practical sense? Or could an NC coating actually inhibit the burning of an underlaid pyrogen? So I did a quck evaluation of how BP burns with an NC coating.
Blackmatch (BM) is a common fuse used by fireworkers to guarantee igntion of the timing element (another fuse or BP packed into a tube known as a spolette, with known burn rates) of aerial shells. It is simply cotton string that has been embedded throughout with a wet BP slurry in water, with a little dextrin (oven-baked cornstarch) as a binder. This is a 2.5" piece of three x 6-strand cotton BM (thick by any standards) that was braided together before rubbing in the BP slurry. One end was double-dipped in double-base NC (and NG) lacquer (beige color), with 10 min drying between layers. Formed a pretty thick shell, probably brittle but didn't evaluate that. The NC shell probably waterproofed the BM (yet to be checked for sure) but, though NC (and NG) are very flammable, in this hard shell format it acted as an insulator that slowed the BM burn rate. You can see the BM blasts sparks in all directions but when it hits the NC, the sparks are primarily ejected towards the NC shell's opening (and propelled the burning remnant when it's mass was reduced below the generated thrust at the end...). The slow-mo file is at 1/4 actual speed, and gives a pretty good visual of the huge 2500F+ BP flamefront.
Thus, an NC shell doesn't burn very quickly, and actually muted the super hot burn & wide flamefront of the BP-only underlying pyrogen. It also tempers the pyrogen burn when NC lacquer is used as the carrier for dipping a slurry, which is why my dips are pyrogen heavy/NC low (can dilute with acetone to allow more pyrogen in the mix). This effect would be even greater with lesser flammable binders like many of the plastics and polymers in some dip kits and in paint. Still, with an appropriate ratio of flammable carrier to pyrogen, heated up with metal addition, you can generate a lot of energy to fire up any motor.
Maybe I'll repeat this dipping in BP or several other pyrogens, some containing various metals, on starter wire (I use 34 and 40g nichrome), and without an NC-overcoat so you can compare how different pyrogen combos work.
Blackmatch (BM) is a common fuse used by fireworkers to guarantee igntion of the timing element (another fuse or BP packed into a tube known as a spolette, with known burn rates) of aerial shells. It is simply cotton string that has been embedded throughout with a wet BP slurry in water, with a little dextrin (oven-baked cornstarch) as a binder. This is a 2.5" piece of three x 6-strand cotton BM (thick by any standards) that was braided together before rubbing in the BP slurry. One end was double-dipped in double-base NC (and NG) lacquer (beige color), with 10 min drying between layers. Formed a pretty thick shell, probably brittle but didn't evaluate that. The NC shell probably waterproofed the BM (yet to be checked for sure) but, though NC (and NG) are very flammable, in this hard shell format it acted as an insulator that slowed the BM burn rate. You can see the BM blasts sparks in all directions but when it hits the NC, the sparks are primarily ejected towards the NC shell's opening (and propelled the burning remnant when it's mass was reduced below the generated thrust at the end...). The slow-mo file is at 1/4 actual speed, and gives a pretty good visual of the huge 2500F+ BP flamefront.
Thus, an NC shell doesn't burn very quickly, and actually muted the super hot burn & wide flamefront of the BP-only underlying pyrogen. It also tempers the pyrogen burn when NC lacquer is used as the carrier for dipping a slurry, which is why my dips are pyrogen heavy/NC low (can dilute with acetone to allow more pyrogen in the mix). This effect would be even greater with lesser flammable binders like many of the plastics and polymers in some dip kits and in paint. Still, with an appropriate ratio of flammable carrier to pyrogen, heated up with metal addition, you can generate a lot of energy to fire up any motor.
Maybe I'll repeat this dipping in BP or several other pyrogens, some containing various metals, on starter wire (I use 34 and 40g nichrome), and without an NC-overcoat so you can compare how different pyrogen combos work.
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