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Nichrome Wire Igniters
Nichrome (pronounced Nye-Chrome) wire
is a blend is 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 of 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
few:
The Nichrome/Fuse Igniter
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. 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 ends of each wire.
Using a sewing needle and a 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.
Another Method of Making Igniters
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. 1.5"
piece of soda straw
2. 6"
piece of bi-pole insulated copper wire (22-24 awg)
3. 1.5"
piece of 30 awg Ni-chrome wire
4. Wire
cutter/strippers
5. Soldering
iron
6. Solder
7. Soldering
flux
8. 6 g KNO3
(Potassium Nitrate or Saltpeter)
9. Epoxy
10. Magnesium
powder (preferably > 300 mesh)
11. Mixing
cup
Procedure
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[Fig.1.
Detail of method for wrapping Nichrome wire]
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1. Strip both leads of one end of the bipole-insulated
wire making sure that one lead approximately .7"
shorter than the other (see Fig. 1)
2. Take the nichrome wire, wrap it first around
the stripped copper of the longer lead, then wrap
about 5-6 turns around the INSULATED part of the
longer lead and then wrapping around the un-insulated
part of the shorter lead (look at Fig.1).
3. Take some soldering flux and put it on the
un-insulated part of the wire where you wrapped
the nichrome. Solder the nichrome wire wrappings
to the un-insulated wire.
4. Mix together a pyrogen consisting of 6g KNO3,
2.5g Epoxy resin and hardener, and 1.5g Mg powder.
Make sure to mix the Magnesium powder into the
wet epoxy fully before adding the KNO3 as this
will greatly reduce the risk of flash explosion
with this mixture. Push this mixture into
the 1.5” soda straw.
5. Push the nichrome wired end of the bi-pole
wire into the pyrogen in the soda straw. Allow
to cure.
6. Cut a slit down the soda straw and peel it
off of the hardened pyrogen.
7. You're igniter is finished.
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