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just a question

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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just a question

Unread postAuthor: bassmaster1228 » Tue Aug 21, 2007 9:03 pm

if i were to take a number of 9v batteries (lets say 5,6,7, batteries)and then conect them in series, then if i were to touch the positive and negative wires together. would it make a nice spark? cause i was thinking i could connect the wires inside the connon and then flip a switch a make a spark? im not sure if it will work or not thats why im asking
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Unread postAuthor: thespeedycicada » Tue Aug 21, 2007 9:07 pm

no it probaly wont you would need many more nine volts then you would want on a cannon but this might work with a capacitor.
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Unread postAuthor: potatoflinger » Tue Aug 21, 2007 9:08 pm

It might actually work, because when I was making a battery pack for an unmodified sprinkler valve with four nine volt batteries, I was measuring the voltage output with a multimeter, and accidently touched one of the test leads to both of the wires coming out of the battery pack and it made a pretty big spark, but I don't know if it's big enough to ignite a combustion cannon or not.
Edit: It might be more reliable for a mini, but with all the nine volts, it wouldn't be a mini anymore.
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Last edited by potatoflinger on Tue Aug 21, 2007 9:19 pm, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Tue Aug 21, 2007 9:10 pm

If your idea were to work, then car batteries would be hooked up directly to the spark plugs, which they're not ;) :wink:
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Unread postAuthor: thespeedycicada » Tue Aug 21, 2007 9:12 pm

to reliably ignite a combustion i would think you would need at least 3/4 of an inch if you must use nine volts and dont want to wire up capacitors use steel wool but im not sure if that would work just use a bbq igniter much cheaper than all them 9 volts :D
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Unread postAuthor: CannonCreator » Tue Aug 21, 2007 9:14 pm

Wouldn't you need some sort of Spark Circut, and a Compacitor?

Im not for sure, but I don't think that would work completely without another compent, like a Spark Circuit, or Compacitor.

Someone please Correct me if im wrong.
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Unread postAuthor: jackssmirkingrevenge » Tue Aug 21, 2007 9:15 pm

It would work if you hooked it up to a piece of nichrome wire wrapped around a match head, or a model rocket ignitor, but that's the realm of solid fuels so I digress - trust me, a BBQ ignitor is more convenient. If you want ignition at the flip of a switch, but a stungun ;)
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Last edited by jackssmirkingrevenge on Tue Aug 21, 2007 9:46 pm, edited 1 time in total.
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Unread postAuthor: singularity » Tue Aug 21, 2007 9:24 pm

steel wool wont work i can tell you that for sure. if you wire a bunch of 9v in series i know there will be a spark, just don't know how well it will work in a cannon (reliably) . and i bet i could get a cylinder to fire with a single car battery (but it would most likely explode in the process)

Wouldn't you need some sort of Spark Circut, and a Compacitor?


its a capacitor man, and yea thats your best bet (just go with camera flash ignition)
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Unread postAuthor: dongfang » Wed Aug 22, 2007 7:47 am

Hi

When getting a nice big spark from disconnecting a solenoid from a battery, it´s the coil in the solenoid generating the high voltage (not the battery). Coils "want" to keep the same current flowing constantly in them; when you disconnect a current source to a coil, it reacts by generating a large voltage.

Somebody actually made nice arcs from 9v batteries and posted it on youtube. But he used like 100s of batteries in series.

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Unread postAuthor: Hailfire753 » Wed Aug 22, 2007 8:53 am

I got a spark from 2 AA batteries. They were both connected to copper wires, which were splayed at the end. Both of the splayed ends were wet. When I rubbed em together, they crakled and made tiny sparks. Although impractical, this could somehow be used in a cannon with a 9v.
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Unread postAuthor: jimmy101 » Wed Aug 22, 2007 10:02 am

You can't ignite propane with the sparks that you'll get from nothing more than a series of 9V batteries, unless you have a several hundred batteries.

What most people are seeing with low voltages are "make/break" sparks. Lots of current through a small contact surface heats the surface up, if the contact is broken (or the contact point melts) you get a brief arc. The arc is generally not hot enough to ignite propane.

Small DC motors throw these kinds of sparks from the commutator. They won't reliably ignite typical spudgun fuels.

Adding a capacitor (in parallel) to a bunch of 9V batteries does nothing except boost the peak current the circuit will produce for a fraction of a second. Since a new 9V battery will produce several amps you would need a cap in the thousands of microfarads range to have any real affect on the peak current. Even then, it is voltage that makes the spark, not current.

To get a spark suitable for ignition of a spudgun you must boost the voltage into the thousands of volts range. An oscillator, coil, and voltage source are required to do that. A capacitor is sometimes added to boost the total power of the spark.
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Unread postAuthor: bassmaster1228 » Wed Aug 22, 2007 3:12 pm

ok thanks guys.

i figured it wouldnt work but it was worth a try.
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