THE NICHROME/FUSE IGNITER
Nichrome (pronounced nye-chrome) wire is a blend of nickel and chromium metals. This metal has the unique property of increasing its electrical resistance when current flows through it, causing it to glow red hot. In short, a thin piece of nichrome wire will quickly heat up when even a small voltage is applied to it. This makes it perfect for igniting fireworks, miscellaneous pyrotechnic items, and rocket motors from a safe distance at the push of a button. There are several different variations of making electrical igniters, but they are all basically the same. Here are a couple:
The nichrome/fuse igniter is easy to make from available materials, and has the extra safety advantage of a short delay produced by the fuse. This is the best igniter to use for smaller black powder type ( Estes or homemade) rocket motors.
The materials needed for the nichrome wire/fuse igniter are: a short length of Visco Safety Fuse, about 1.5" of nichrome wire, and some insulated wire. You can use just about just about any type of insulated wire (speaker wire, alarm hook-up wire, etc.; all available at Radio Shack or your local hardware store). Stranded wire is generally easier to work with, and much more flexible than solid wire. It's best to use wire no thinner than 20 gauge. If you plan on running the wires a long distance like 20 or 50 feet for launching model rockets, etc., then 16 gauge or 14 gauge wire would be better. The lower the wire gauge number is, the thicker the wire, and the less power it will take to fire the igniter.
Strip about 1" of insulation off the end of each wire.
Using a sewing needle and pliers, push the needle through the end of the fuse to make a small hole.
Twist the nichrome wire tightly around one of the wires and fold over so it is secure.
Insert the other end of the nichrome into the small hole in the fuse and connect to the remaining wire by twisting and bending over as you did before. Make sure the two ends of the wire are not touching each other, or the igniter will not work.
Finally, fold a piece of tape over the connections so it protects them and prevents them from touching each other. When power is applied to the opposite ends of the wire, the small piece of nichrome will heat up, glow red hot, and ignite the fuse. Depending on how long your wires are, and how thick the wire you used is, as little as 3 volts (2 flashlight batteries) will be sufficient to make the igniter work. Long lengths of wire may require as much as 12 volts, and very long runs may require even more.
This information will show you how to make a highly reliable, fast burning, and very high temperature rocket motor igniter. This thing burns hotter than 3500 (F) and will light reliably and quickly on a car or motorcycle battery. These igniters include Magnesium powder and potassium nitrate. These two ingredients should never be mixed dry as they become an explosion hazard.
What You'll Need:
- 1.5" piece of soda straw
- 6" piece of bi-pole insulated copper wire (22-24 awg)
- 1.5" piece of 30 awg Nichrome wire
- Wire cutter/strippers
- Soldering iron
- Soldering flux
- 6 g KNO3 (Potassium Nitrate or Saltpeter)
- Magnesium Powder (preferably > 300 mesh)
- Mixing cup
[Fig.1. Detail of method for wrapping nichrome wire]