BP electronic ignition problems

I ain't even got a garage, you can ask my wife.

Because I do know a bit I DO NOT engage in the sort of behavior likely to result in one having an interesting garage.

All my blowing up was on Uncle Sam's dime and when I quit working for Uncle Sugar I made certain to never be tempted and continue to avoid temptation of he whose name shall not be mentioned.

-kBob

The coated wires work fine and even non-coated nichrome ignitor wire will work to set off model rocket engines with enough juice, a 12 v car battery for instance. I'd bet the coating unnecessary for black powder with enough amps, too.

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If I was planning to use this for a cannon, I'd probably poke the nichrome wire segment into the top of the cannon's vent hole and pour some BP in on top of it.

Yeah, the greater the current, the faster that wire will heat up.

[EDIT - Interesting article on batteries - http://www.learningaboutelectronics.com/Articles/Battery-internal-resistance - because of their low internal resistance, NiMH and NiCad's are really capable of pumping out the amps]

As far as a pyro coating goes, I've read that BP has an auto-ignition temperature up around 700F. Modern smokeless powder has an auto-ignition temperature around 350-400F. If you could make a paste with smokeless powder (dissolve with acetone?), the coating might ignite a little sooner....?

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ofitg said:

If I was planning to use this for a cannon, I'd probably poke the nichrome wire segment into the top of the cannon's vent hole and pour some BP in on top of it.

Yeah, the greater the current, the faster that wire will heat up.

[EDIT - Interesting article on batteries - http://www.learningaboutelectronics.com/Articles/Battery-internal-resistance - because of their low internal resistance, NiMH and NiCad's are really capable of pumping out the amps]

As far as a pyro coating goes, I've read that BP has an auto-ignition temperature up around 700F. Modern smokeless powder has an auto-ignition temperature around 350-400F. If you could make a paste with smokeless powder (dissolve with acetone?), the coating might ignite a little sooner....?

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I would strongly advise not dissolving smokeless in acetone or any other non-polar solvent. Keep in mind that most powders are a mix of nitrocellulose and nitroglycerin. The differences in solubility of the two compounds may make for a more sensitive result than you planned on.

I think what she is saying is that you probably dissolve the nitroglycerine from the mix and not equally dissolve both reagents. Now you have a beaker full of free nitroglycerine to deal with . Acetone is not non polar . It is a a polar a-protic solvent and what you could end up with for your efforts is a compound called blasting gelatin. Not something you want to put in your chamber.

CANNONMAN said:

OW, I don't get it. Would not the original polarity return after the solvent has dissipated? Are you thinking a potential for spontaneous combustion? and where's your .02?

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Yugo pretty much beat me to it. Let's say for sake of argument you have a binary powder that is 20% NG and 80% NC. Your solvent is going to dissolve more of one than the other and you have idea none what you are leaving behind or taking with you.

I'd use an estes rocket igniter. Why reinvent the wheel?

Cannonman, I tried a new experiment today - as they say, idle hands are the devil's workshop.....

I used the same "igniter" illustrated in my last experiment: eight-foot length of 24 AWG speaker wire with a one-inch segment of 32 AWG nichrome wire at the end. This time I enclosed the nichrome wire segment in a quarter-inch-diameter paper tube, filled with fine blackpowder (approx. 4Fg).



I also used the big 13.8V/20A power supply from my first experiment - you could duplicate this with a 12V NiMH battery pack.

I wired a 0.2-ohm resistor in series with the speaker wire "igniter", and I connected a data-logger across the 0.2-ohm resistor to measure the duration of the current flow (ie, from the moment the power supply is switched on, to the moment that the BP ignites, breaking the nichrome wire).

Here's the data-logger record -



The horizontal scaling is 0.167 seconds per division, so you can see that the ignition delay was roughly one-sixth of a second. Judging from the amplitude of the pulse (1.2 volts), there must have been around 6 amps of current flow.

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CANNONMAN said:

Dear OW & yugorpk, would you folks kindly help a dear demented cannonman out with this project? I'd like a 30' wire that is powered by a handheld battery device. The wires attach to home made igniters. The igniters should be no more than 1/4" in diameter. What should the ignition wire be and what would make a good coating? I would also like the process to appear near instantaneous from flipping the switch to cannon going bang. Last the ingredients should be simple to make and less expensive then buying them. Thank you for your big brains.

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This is really outside of my field. I suppose if I were to do such a thing I would wrap the wire around the head of a kitchen match then tape the match to a piece of powder "cake" or possible a side ignition fuse.

I'm gonna make a really big batch of wonderful BBQ and have ofitg over.

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Cannonman, the BBQ sounds Great - let's grill up some pyrite, and you can show me how to extract the sulfur!