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While trying to keep with the; "use what I have" mindset. I made these first igniters using these parts:
The cat. 5 cable was cut to 10" or so, then one end was cut 1/2" shorter than the other. The wire was stripped about 1/4" from each of these ends. A small loop was made in each stripped wire and a 1" length of steel wool was threaded through the top loop and soldered in place. Then the steel wool was wrapped around the long wire (the one you just soldered) about three turns and then run through the bottom loop in the cat. 5 wire and soldered in place. Loose ends were then trimmed. The opposite ends are now stripped back 1/2" and twisted together.
Now for the pyrogen. I made my nitrocellulose lacquer by dissolving 3 ping pong balls in about a cup of acetone. I needed some black powder, so I cut open an unused commercial D motor. Then proceeded to crush it into a fine powder. Not as easy as it sounds, and I have yet to find an easy way to do it. I filled a small test tube about 1/2 full of black powder, then added the nitrocellulose until it was a thin paste.
A note here on the black powder for the pyrogen. I tried using off the shelf muzzle loader 4f black powder, but I was not pleased with the results. It seems to be too coarse, not remaining suspended in the lacquer. In the future I plan on making my own black powder, we'll see how that goes.
To finish the igniters, just dip in the pyrogen. Let dry for 30 minutes, dip again, let dry and they are ready to go.
I used these for both motor ignition and for deployment initiation. They work fine for motor ignition, but they were not consistent for low amp deployment purposes. Note: For deployment, the igniter was used to ignite a black powder charge.
Changes to the igniter:
After testing other types of resistance wire for the igniter, I happened upon some picture hanging wire. It is basically a small steel stranded cable. I cut the wire to 1" and pulled a strand out of the cable. It heated up instantly red hot using a high amp 9 volt battery. Using a standard 9 volt transistor radio battery, the wire was slow to heat up. I now use this wire for my motor ignition igniters, it is easier to use than the steel wool, and I think stronger. The other aspects of making the igniter are the same as I used before.
This is the wire I now use on my igniters. It's 18 gauge solid copper. It came as three strand loosely twisted. Once cut to the desired length I pull out one strand.
The ends of each wire are bared about 1/4", and the ends offset about 1/3".
The silver wire to the right is picture hanging cable. I cut off about 1 1/2" and separate the cable into individual strands. Each strand is then used as the resistance wire on an igniter. Next to the green arrow is an individual strand. It's hard to see but it's there.
This is hard to see too. But the strand of cable is wrapped around the bared ends of the wires. Starting at the inside, I use at least three wraps around the first bare wire end, then three wraps around the whole thing where there is still insulation (red wire), then use the rest of the strand on the exposed copper end of the outside wire (red).
The cable strand is then soldered to each of the bare ends.
The soldered the end is dipped in the pyrogen. The pyrogen is acetone with ping pong balls dissolved in it as before, with powdered black powder and magnesium mixed in. The mixture needs to be reasonably thin, a thinner mixture actually builds up faster on the wire than a thick mixture. I use about 5 parts black powder to one part magnesium. The magnesium powder is home made from sanding a block of pure Mg with a small drum sander. It's a little finer than sugar, but not as fine as flour. I'm sure you could use commercial Mg here, but the larger Mg particles help throw hot sparks.
Here is the finished igniter after its second dip in the pyrogen. The leads are stripped, and the igniter checked for continuity, the igniters average about 1.5 ohms. The leads are then twisted together for safety and the igniters stored in a PVC pipe with one end cap not glued on.
Here is a capture of the igniter firing.
Click here for a video of the igniter firing.
The igniters really throw out a nice, reasonably long duration ball of fire. They start my my sugar motors and bring them up to pressure very quickly.