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Two Combustion Chambers?

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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Two Combustion Chambers?

Unread postAuthor: itwentboom » Mon Feb 26, 2007 10:08 pm

I've been building a duel chamber cannon and I'm not sure if I'M wasting my time? I started with two 36" 4" chambers and elbow up to a tee. I am going to use two propane meter pipes connected to one bottle. The chambers are SCH 40 reduced to 2" SCH 80 elbows and Tee. My ignition will be two 100,000 volts stunguns wired to one control box. My concern is that they wouldn't fire exactly the same time. Is there anything else wrong that you can tell that would make this project Trashed? I just wanted to try something different and i'm sure its been tried before.
Thanks
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Unread postAuthor: trae08 » Mon Feb 26, 2007 10:10 pm

well if i was doing this i think using 2 check valves on the chambers so the pressure can go out of both but not out of one an into the other... if one fire before the other... but overall i think it sounds sweet
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Unread postAuthor: noname » Mon Feb 26, 2007 10:12 pm

One stungun should be fine, unless you have something like triple sparks for each chamber. Just use the other one on another gun, it'll be fine.
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Unread postAuthor: itwentboom » Mon Feb 26, 2007 10:36 pm

I see alot of different check valves, SCH 40 ball check valves, or union check valves? Thanks
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Unread postAuthor: frankrede » Mon Feb 26, 2007 11:19 pm

if you have both firing at the same time you don't need any check valves. Those will only cause trouble.
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Unread postAuthor: itwentboom » Mon Feb 26, 2007 11:29 pm

Thats my worry that they won't and if they don't could this whole cannon blow up? I might just scrap it the more i look at it the more i think it won't work. If both chambers go to the tee and to the barrel what prevents it to flow right through the tee? Sorry for all the question do u think it can work i really wanted to keep building this one?
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Unread postAuthor: FiveseveN » Tue Feb 27, 2007 8:35 am

1. Forget the check valves
2. There isn't a greater chance of it blowing up than with a single-chamber gun. In fact, if one chamber misfires and for some strange reason the flame front from the other chamber doesn't ignite it, you'd simply get roughly half the power, thus half the hazard (excluding the fire hazard of an unfired chamber). Just ignite it again after the 1st shot and it'll fire a blank.
3. Like noname said, a single stun gun should suffice. That would also simplify synchronization.
4. There is no way in hell the chambers will ignite at the EXACT same moment and provide the EXACT same energy upon combustion. For this purpose, the delay can be ignored altogether, but you could use a slightly longer barrel to take advantage of the longer burn time (but remember to compensate for the different geometry, as described below). A fan for each chamber is also a good addition.

The twin-chambered combustion design hasn't been studied thoroughly, but it shouldn't behave much differently from a "normal" combustion. The main advantage is that for a given volume, your chamber system will have half the length. The shape of the chambers is thus closer to the ideal sphere, which means faster and more efficient combustion.
The only disadvantage is the dead volume, possible stress point and flow constriction of the tee.
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Unread postAuthor: Hotwired » Tue Feb 27, 2007 10:33 am

I can't see a huge benefit in dividing the chamber, you just get a bulkier layout. Particularly since combustion chambers tend to be fairly short anyway.

I'd list that in the same category as multi-shot large bore pneumatics: not really worth it.

However if you do go for it then a single stungun and a spark gap for each chamber would be fine.

A misfire in one chamber would be interesting though particularly since the hot (and possibly still combusting) gases from the other one would be flying around.

Check valves would be a massive damper on the force of the combustion and I'd not bother with them.

Still, its something to think about.
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Unread postAuthor: spudthug » Tue Feb 27, 2007 2:17 pm

i agree with no name just hook one stungun to all the wires
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Unread postAuthor: itwentboom » Tue Feb 27, 2007 4:10 pm

Thanks for the INFO. I will let you guys know what happens when i hit the button that is if i live through it LOL. Again you guys Rock and to give that much info to a Noob is awesome.
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Unread postAuthor: itwentboom » Wed Feb 28, 2007 4:35 pm

I was thinking would it be better to use a Y instead of a tee to connect the chambers to the barrel?
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Unread postAuthor: LGM » Wed Feb 28, 2007 5:20 pm

There is a double chambered golfball cannon on here that I saw, but it is a very old thread and I am having some trouble finding it. He had one ignition in each chamber and didn't report any misfires in one of the chambers, at least not that I saw.
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