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If you want to make a really loud bang. . .

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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If you want to make a really loud bang. . .

Unread postAuthor: explsvcookie257 » Mon Sep 01, 2008 10:20 pm

Well hello everyone i have not been on in a while but I made a combustion on saturday after I had already made a pneumatic weird I know but I have a question and some info I would like to share.

so question 1 my sparker used to jump the spark gap now it doesnt ive cleanied it and i wrapped the bolts in tin foil which helps and i just add new tin foil when they get gunked up. but what can i do to clean them better ive tried brasso paint thinner alcohol and steel wool wich kinda works but i can seem to get them as shiny as they where when i bought them and they are galvanized by the way.

And if you want to make a defaning bang put on your 2" barrel mines 2 feet long and put a caulk tube in there totally empty and the noise it makes when fired is defaning it really hurts my ears and it goes pretty high and at night it echos really far and you can also feel a shock wave when its fired i think its because the caulk tube is hollow its goes up in the air like 15 to 20 seconds ill time it and give you a good estimate.

oh and if your wondering. . .

my chamber is 11" of 4" sch 40 and the sdr21 barrel is 36 inches long whatever it is it gives me a 1.5 to 1 ratio.

and and i use aquanet hairspray is that a good or bad choice as fuel and i spray it for like 3 to 6 seconds.

sorry i wrote a book there i dont like being short and simple i like to explain in depth haha.
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Re: If you want to make a really loud bang. . .

Unread postAuthor: potatoflinger » Tue Sep 02, 2008 5:03 am

explsvcookie257 wrote:and and i use aquanet hairspray is that a good or bad choice as fuel and i spray it for like 3 to 6 seconds.

That would probably explain the trouble with the sparker. I don't know exactly how to clean the bolts, but if steel wool gives good results keep using it.
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Unread postAuthor: explsvcookie257 » Tue Sep 02, 2008 2:45 pm

haha yeah lol combustion are fun to make noise with but there not always reliable like a pneumatic but I liked it so much i didnt even touch my pneumatic all weekend.

I wonder has anyone else noticed that the caulk tubes make a really loud bang.
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Unread postAuthor: Radiation » Tue Sep 02, 2008 4:05 pm

Well the reason is that the hollow back of the caulk canister directs sound back toward you rather than just radiating it everywhere. You can get the same effect from any ammo with a substantial cavity in the back of it. It is fun... until your ears ring.
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Unread postAuthor: explsvcookie257 » Tue Sep 02, 2008 7:29 pm

yeah ide say its louder than my 12 gauge or 30-06 but its alot of fun and my freind across the street could hear it playing rockband in his room and he came over and was like wow lol ohh and it makes my ears ring evereytime and i cant hear well for like 5 minutes so after like 10 shots i started to wear earplugs. also thatnks for the info radiaition
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Unread postAuthor: FLONE » Sat Sep 13, 2008 8:31 am

My 1.75 C:B combustion (over-under) goes bang very nicely without any projectile. Static Guard spray, non-fan, bbq twin spark. Wait until the wife is gone, give a 4-6 second spray, and watch the flames. Even with ear muffs it is loud.
I don't do it in the basement anymore, my brother reminded me that the concussion might rattle the windows a bit more that they could handle.
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Unread postAuthor: firey_ginga » Tue Sep 16, 2008 1:27 am

what it the best ignition system. every one talks about using a barbique lighter, wouldnt a spark plug from a car work better?
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Unread postAuthor: starman » Tue Sep 16, 2008 1:46 am

firey_ginga wrote:what it the best ignition system. every one talks about using a barbique lighter, wouldnt a spark plug from a car work better?


A spark plug by itself doesn't produce a spark...it's just a fancy gap. You need a high voltage source to provide the arc across the gap. BBQ ignitors are self contained HV sources that can drive any reasonable gap of your choice, including a real "spark plug" if you desire.
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Unread postAuthor: firey_ginga » Wed Sep 17, 2008 2:28 am

i know a spark plug doesnt produce its own voltage but if a spark plug were conected into a circuit with an ignition coil it would produce the same high voltage spark used in a car engine which would ignite the fuel better that a bbq lighter
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Unread postAuthor: Hotwired » Wed Sep 17, 2008 5:03 am

Theres nothing special about the sparks created in a car system. Still a few tens of kilovolts as in a BBQ lighter and having the sparks go through a sparkplug does nothing to help ignition.
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Unread postAuthor: rp181 » Wed Sep 17, 2008 7:08 am

a spark is a spark untill you get into high power ignition (current, not voltage)
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Unread postAuthor: firey_ginga » Thu Sep 18, 2008 3:04 am

not necessarily a more powerfull spark will ignite the fuel better than a weak spark
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Unread postAuthor: Demon » Thu Sep 18, 2008 6:24 am

Why dont use a mini combustion with a burst disk as ignitor?

I will be the best ignitor you cant have!
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Unread postAuthor: jimmy101 » Thu Sep 18, 2008 11:35 am

firey_ginga wrote:not necessarily a more powerfull spark will ignite the fuel better than a weak spark

Nope.

The power and/or performance of a combustion spudgun is independent of the power of the spark as long as the spark is enough to actually ignite the fuel mixture.

A more powerful spark will not ignite the fuel better than a weak spark as long as both sparks are powerful enough.

To ignite propane in air it takes a fraction of a millijoule in a sufficiently small volume. That is a very small amount of energy.

A spark plug will not work significantly better than any other spark gap. Indeed, the best gap is a pair of very sharp points. A spark plug can certainly be used but the only advantage a spark plug has is that it can be installed in a single hole, whereas a pair of screws takes two holes. The plug though uses a much larger hole and you will probably need the appropriate tap so you can thread the hole properly to keep the plug from being blown out of it's hole.

A gasoline engine needs a much higher spark voltage to fire the plugs because the breakdown voltage of the air-fuel mixture goes up with pressure. It takes a significantly higher voltage to jump a given gap at 10 ATM of pressure than it does at 1 ATM. I believe hybrid builders usually figure that a 10X hybrid (10 ATM before ignition) requires either ~10X higher sparker voltage or a spark gap that is 1/10 as big compared to a 1 ATM gun.
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