Sciencemadness Discussion Board


schatz - 24-4-2011 at 07:14

I will be doing a bit of research into using smd resistors as bridge wire initiators and am looking at various ignitor compositions.
I understand that some electric munitions use kclo3+ Lead thiocyanate; And possibly Kclo3 + Potassium Ferricyanide.
I will be mixing only sub gram quantities at a time but was wondering about sensitivity issues since I have no experience with either compositions.
I was planning on using NC as binder dissolved in acetone.

Bert - 24-4-2011 at 07:44

They are both quite sensitive to shock and friction. All the commercial igniters I have recently used avoid chlorates now. 20 years ago, I could strike a commercial igniter on a safety match striker pad and it would fire. Or a tap with a hammer on a steel surface would cause one to explode- Accidents with that class of mixtures were common.

I don't know what your intend use is, however those using resistors for model rocket igniters oftn use Copper oxide/Aluminum thermite. Plain old black powder with a bit of Silicon or pyro Aluminum if you need more performance would work too.

pjig - 24-4-2011 at 07:58

What do you think they use then for commercial shells and class 1.3 items ??
I know most if not all commercial ematchs are covered with sleeve to protect the head(comp) from being touched.


schatz - 24-4-2011 at 08:15

Some commercial electric match heads I have seen and handled used the mentioned plastic sleeve and probably use Kclo3+Sb2s3. I could get them to go off by direct friction or hammer blow ( with plastic cover off).
(My intended use is both as heat ignition and bullet hit effects.
In the past I have assisted historical re-enactment groups and amateur film makers, who even when they have expert technical help, cannot afford some propriety devices. Some squibs, because of transport liabilities are frankly unaffordable.)


Oh !
Some eastern (chinese ?) e matches that went open circuit through storage, I witness being delicately dissected had what looked like a pale ( white ) composition inside. Could not have contained As, metal or carbon.

-={Please do not double post. Thanx: Moderator}=-

[Edited on 25-4-2011 by quicksilver]

Bert - 24-4-2011 at 20:46

Schatz, for bullet hits used on an actor's body you need to restrict the amount of solid material that might be ejected from the explosion possibly striking actors, crew, expensive camera gear- A resistor with heavy wire leads may become shrapnel. Professional body hits have very fine lead wires with a small bridge wire and paper bodies.

For just setting something afire, plenty of others have used resistors. If you're going that route, safest to use the least sensitive first fire you can and a hefty battery. The extremely sensitive and fast bridge wire/pyrogens designs are needed for scenarios involving limited output firing systems and/or multiple matches in series that all need to ignite really fast before any element melts to break the circuit.

All the commercial igniters I use do have metal fuels. They are so fine that they're not easily visible in the composition of the match head.

I personaly installed about 8,000 igniters last year. I like them to be as insensitive as possible and still be reliable.