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Overkill?

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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Overkill?

Unread postAuthor: magnum9987 » Sun Jun 22, 2008 3:33 pm

I am thinking to build my first cannon after months of watching this site. I am planning on building a marbel muzzle loader, as they are cheaper than taters. I plan on using an 8 foot barrel (Of what diameter i am unsure). As i whant high penetration and power, I am thinking of a huge chamber, maybe 6in by 36in. My question is, is the chamber ridiculously large and inneficient at the gun I am making? As well, what diameter pipe would be best for a tight fit for the marble?
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Unread postAuthor: potatoflinger » Sun Jun 22, 2008 5:35 pm

Well, I think that it would be best to use a smaller chamber diameter, since you are primarily shooting marbles out of this gun.

A good barrel for marbles is .5" PVC, but you may have to go to a craft store to find marbles that fit. Most of the marbles that you can get from dollar stores are just a little bit too big to fit in .5" pipe.
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Unread postAuthor: MaxuS the 2nd » Sun Jun 22, 2008 5:41 pm

If you're going with a 6" x 36" chamber, it would be a vast waste of energy to 'bottleneck' that down to .5".
My advice, don't fire marbles, give it a 3" barrel instead and send those spuds soaring.
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Unread postAuthor: Ragnarok » Sun Jun 22, 2008 6:13 pm

MaxuS the 2nd wrote:My advice, don't fire marbles, give it a 3" barrel instead and send those spuds soaring.

You'd need seriously hefty spuds for a 3" barrel.
Really, 2" bore is the limit for spuds, and 1.5" is often a wiser choice.
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Unread postAuthor: SpudFarm » Sun Jun 22, 2008 7:00 pm

the golf ball sized barrel i have is also pretty anojing (spelled wrong) to find spuds for since they all get a gap someplace.

(but if it fits golf balls, why bother to find a spud?)
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Unread postAuthor: Lentamentalisk » Sun Jun 22, 2008 7:02 pm

for an 8' barrel with a 1/2" diameter, you would only need your 3' chamber to be 1" in diameter. You should aim for a chamber to barrel ratio of around 1:1, though that varies greatly with the individual projectile, pressure, and all.
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Unread postAuthor: daberno123 » Sun Jun 22, 2008 7:05 pm

I'd say play around in HGDT for a while to get the gun fully optimized. You can probably use smaller diameter chamber and not lose much performance.

But if you have access to 6" pipe and fittings than why not? A marble barrel will be a waste though, put a 4" barrel on it and shoot 3" caps out of it! :D
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Re: Overkill?

Unread postAuthor: jimmy101 » Sun Jun 22, 2008 7:13 pm

magnum9987 wrote: As i whant high penetration and power, I am thinking of a huge chamber, maybe 6in by 36in. My question is, is the chamber ridiculously large and inneficient at the gun I am making? As well, what diameter pipe would be best for a tight fit for the marble?

Yes the chamber is ridiculously large (who cares about efficency?). Get HGDT and fiddle around with it. It'll give you a very good idea of what chamber size is reasonable for your particular barrel. I suspect you could cut the volume of your chamber by a factor of 4 and only loose a few percent in muzzle velocity. Besides, the cost of a 6" cleanout and the reducers to drop 6" to 0.5" is going to be significant ($50-$100?). For a small diameter (<1") barrel there really isn't much need for a chamber any bigger than 2" diameter.

As to barrel choice, get a couple different diameter marbles and visit your local PVC supplier.

Someone once posted that they carried a key chain with short segments of various PVC pipe and fitting diameters. Never know when you might stumble on the perfect ammo. This situation is the opposite, carry several different rounds with you, never know when you'll stumble on the perfect barrel.

EDIT: Engrish
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Unread postAuthor: magnum9987 » Sun Jun 22, 2008 8:56 pm

Maybe not so much overkill as "Home Made Sniper Rifle?"
Anywho, Maybe rather than use marbels, go to an army surplus and buy some 12.7mms and get bush (kidding, i sure as hell aint a commy). MAybe a horribly expensive barrel made out of pvc pipe fittings to actually get .5in (or .50cal if you will).

Fantasies of sniper rifles aside (And .50 cals), so the chamber can be 1in diameter, as long as the barrel is 3 feet long. I might as well half the length and double the diameter.
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Unread postAuthor: Lentamentalisk » Mon Jun 23, 2008 12:18 am

no, the barrel can be 8 feet long by .5" diameter, if your chamber is 1 foot of 1" pipe.
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Unread postAuthor: Carlman » Mon Jun 23, 2008 2:42 am

for marbles and small bore barrels i would suggest a pneumatic, more power in smaller bores and easy to pump because of *small* chamber that is needed.

but if your set on combustion then listen to everyone else :D
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Unread postAuthor: MaxuS the 2nd » Mon Jun 23, 2008 7:06 am

Ragnarok wrote:
MaxuS the 2nd wrote:My advice, don't fire marbles, give it a 3" barrel instead and send those spuds soaring.

You'd need seriously hefty spuds for a 3" barrel.
Really, 2" bore is the limit for spuds, and 1.5" is often a wiser choice.

Larger goods then, Pumpkins, Oranges, Apples, Pint Glasses, Kitchen Sinks..
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Unread postAuthor: magnum9987 » Mon Jun 23, 2008 4:13 pm

MaxuS the 2nd wrote:
Ragnarok wrote:
MaxuS the 2nd wrote:My advice, don't fire marbles, give it a 3" barrel instead and send those spuds soaring.

You'd need seriously hefty spuds for a 3" barrel.
Really, 2" bore is the limit for spuds, and 1.5" is often a wiser choice.

Larger goods then, Pumpkins, Oranges, Apples, Pint Glasses, Kitchen Sinks..


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Last edited by magnum9987 on Tue Jun 24, 2008 10:42 am, edited 1 time in total.
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Unread postAuthor: psycix » Tue Jun 24, 2008 10:33 am

MaxuS the 2nd wrote:Larger goods then, Pumpkins, Oranges, Apples, Pint Glasses, Kitchen Sinks..


:lol:
Quite costly ammo if you ask me, but fun if you happen to have a gun capable of firing that.
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Unread postAuthor: MaxuS the 2nd » Tue Jun 24, 2008 11:56 am

D_Hall's Pipe Dream. ;)
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