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I think this talk of certain substances should stop here. It will do no good for the forum, and although you may not realize it, you put yourselves in danger by even mentioning your knowledge of it over such easily intercepted channels. I know someone who suffered a very unpleasant fate because he said something he shouldn't have, and I'd hate to see that happen to anyone here. Whoever posted about themselves having experience with flash powder, I strongly advise you edit out that little remark.
Now, onto the actual topic, which, the careful observer will notice, never implied anything at all about illegal matters (regardless of the rather poorly chosen username):
The usefulness of any particular ignition system depends on the rest of the apparatus - if it takes an hour to reload and you stand 50m away to fire it, a system that takes up a lot of space (such as a capacitor discharging through an ignition coil), or even one that requires a manual reset of the spark gap (burning / exploding wire setup with high current, low voltage), is a fine choice. If your cannon is handheld and designed for easy use, something more compact is in order. The difficulty in doing so depends on your skill level and confidence with electrical builds.
-A flint-based lantern sparker is the easiest possible option, but often difficult to obtain. You could likely rig one up yourself with the right tooling and mechanical skills.
-If you live in the States, "stunguns" (which are insufficient for stunning and have no relationship to guns) make a great ignition system until they burn out (this occurs after anything from 5 seconds to several years of intermittent use, depending on the quality).
-If you're not in the States, a simple stungun design can be replicated with capacitors, a step up circuit, low voltage power supply (battery), and a miniature pulse transformer (go to 4hv, but read before you post)
-Size constraints permitting, a camera flash capacitor discharging through a car ignition coil is simple, effective, and made with readily available parts (see SpudWiki).
-A flyback-based Mazilli driver circuit (again, see 4hv) is a good choice if you're feeling ambitious, as it can be built compact and runs on a DC source)
Although it is tempting to think otherwise, a bigger spark really doesn't mean a more reliable ignition. One of my acquaintances did a test to that effect, using a propane/air mix that was just barely beyond the ability of an ignition coil based circuit to ignite it. He tried camera capacitors and steel wool, then moved on to high current arcs, and eventually up to a 500J pulse capacitor discharging through aluminum foil, which ablated rapidly and produced a plasma cloud that filled the entire chamber. This spark was comparable to a small blasting cap in total energy released, and powerful enough to momentarily raise the chamber pressure by a few psi, but still insufficient to ignite the just-barely-overfueled mix.
This should serve as more concrete evidence of the conventional wisdom here saying that "a spark is a spark is a spark" - if a 0.1J spark cannot ignite the mix, it is unlikely that any other spark / arc / 10000 degree plasma cloud filling the entire chamber will ignite the mix. The plasma cloud will improve the burn if the mix is ignitable, but it will likely not aid in actually igniting the mix unless you have so much pulsed power as to make the combustion itself superficial.
If your combustion launcher is unreliable, improve the fuel metering, increase the number of ignition points, and use a fan to mix the fuel more thoroughly.
I suppose, but it is near the same as an ignition coil setup or a marx generator, both of which use the same concept
Standard ignition with a coil uses a low voltage current interuption to create a high voltage spike. It does not creat a spark when power is applied. It sparks when the power is interupted.
Capacitive discharge uses a high voltage (over 12 volt) as a pulse into the primary of the ignition coil. It creats a spark on application of power to the coil.
Marx is simply a voltage doubler or tripler to the n-th degree. Marx is a name for a voltage multiplyer I have never heard before for a voltage multiplier in all my years in electronics.
I looked it up. It uses spark gaps instead of diodes.
Not used in sensitive electronics such as TV, Medical X Ray, Microwave, etc. This won't work off a 120 volt outlet without a transformer being used to boost the voltage high enough to operate the spark gaps.
Not really.. It's a fairly universal composition used so often.
But I agree, no more of that talk is required.
Marx generators are not actually very complicated.
Quick and easy marx generator
Needless to say, it wouldn't misfire often.
Though honestly speaking, it would not be hard to conceal a single pole marx generator along the length of the chamber, the real drawback being that they're difficult to use without an AC socket..
You'd think so, but if someone from law enforcement read that and figured out where the writer was, he may as well have been producing 5 tonne batches of RDX and shipping them to Somalia. Remember, everyone wants to make a name for themselves, and the opportunity to catch a "terrorist" is not going to be passed over.
Marx generators fall into the category of "effective but overkill" ignition systems, unless you're trying to use a traditional sparkplug for a 100x mix. The most compact way to power one in the field would likely be a flyback circuit, which would be more than adequate in itself for lower mixes.
Flash powder is actually used fairly frequently. However it is not to be used as propellant in this forum. I have legally used it on stage as part of a magic show. It with flash paper are the main components for a quick flash of flame on stage, either from the floor or from fingertips. Flash paper provides a bright yellow flame with little smoke. The flash powder in flash paper provides the instant smoke cloud used in magic shows. Proper training is required to use in public performances and many places do not permit it due to fire regulations. Check the local codes before use.
I agree, it is dangerous. I posted this as a warning. Proper training is required. It is not a plaything.
It is dangerous in larger quantities and if contained. Ejected by flash paper and ignited it burns rapidly and relatively quietly. Ignition of a 1 oz jar in the jar is most likely to cause serious injury. It is not a toy.
Do not PM me asking how to use it. I will only refer you to contact a professional for proper training.
Law enforcement is aware of the legal uses of flash powder. Be sure you have a legal reason to have it, as law enforcement does know it is often used to make illegal fireworks and making explosive devices is illegal in most places. My current line of work does not include any legal use for the stuff, so I have none.
I have never had more than one oz jar at any one time. Excessive amounts or manufacture will raise suspicions of intent.
It is like my large launcher. If spud guns are not legal here, it is a T shirt launcher built for an engineering challenge. I store it next to the contest rules, the mentored school photos, the big game photos, etc. Getting caught shooting spuds at passing cars would most likely land me in legal hot water. Use of flash powder is the same.
It's like Chinese New Year in the USA. Most places firecrackers are very illegal. A traditional lion dance is always done with firecrackers. I've never seen an arrest at a lion dance in a parade with firecrackers.
The police know the traditions and how they are used and by whom.
Sorry for the off topic post.. I won't discuss this for spudding. It's not legal. It is dangerous, and against forum rules.
Mods, It's OK to delete this post if my warnings are against forum rules.
I have PM'ed PCGUY to have him review this post.
Another cheap possibility is to use a 10 Ohm or so 1/4 watt resistor with a small 12V automotive jumper battery. 12V over 10 Ohms is 14.4 watts, the 1/4 watt resistor will burst into flames. This is basically a ghetto squib that avoids the need for any kind of powder. Big drawback is that the resistor has to be relplaced each shot. Occasionally, this setup is used to ignite dust explosions and other pyrotechnics that require much higher energy densities than what most spark generators can provide.
BTW: the camera flash and other types of ignition coils circuits are in the wiki:
http://www.spudfiles.com/spud_wiki/inde ... on_sources
http://www.spudfiles.com/spud_wiki/inde ... ition_coil
http://www.spudfiles.com/spud_wiki/inde ... mera_flash
When you take everything into consideration a standard BBQ piezo is really the best ignition source. For hybrids, and setups with lots of spark gaps, then upgrade to a stungun. All of other methods are either (1) more expensive, (2) finicky or (3) a lot more work than these two.
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