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Gun Plans

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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Unread postAuthor: SpudChucker24 » Wed Feb 13, 2008 1:56 am

Ok so i was just brain storming something for my next cannon and this is what i have. My goal here is to get pass 1000 feet (Hopefully is do-able with combustion). It might be too small for it but tell me how far you think i could get. I havent done the C:B ratio because im lazy and still need to figure out how to do it.

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Unread postAuthor: Carlman » Wed Feb 13, 2008 4:11 am

what is with the mesh?

i very much doubt you will 1000ft with that design.
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Unread postAuthor: TurboSuper » Wed Feb 13, 2008 7:54 am

The mesh probably prevents the ammo from being pushed in too far.

Design looks nice, although 1000 feet is a bit too optimistic for a simple combustion,imo.
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 13, 2008 8:49 am

A mixing fan and longer barrel would certainly help achieve your range target.

Also, if you're willing to put in the effort, making a streamlined saboted projectile like the one below (though you might want to use some say 1/2 inch tubing instead of a nail for a large calibre) instead of a spud would greatly increase your range.

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The overall weight will be low, so the projectile will accelerate to a high velocity, and on leaving the barrel the foam will fall away, leaving the dart to travel to a much longer distance than a section of potato would.
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Unread postAuthor: Carlman » Wed Feb 13, 2008 9:06 am

jackssmirkingrevenge wrote:A mixing fan and longer barrel would certainly help achieve your range target.

Also, if you're willing to put in the effort, making a streamlined saboted projectile like the one below (though you might want to use some say 1/2 inch tubing instead of a nail for a large calibre) instead of a spud would greatly increase your range.

Image

The overall weight will be low, so the projectile will accelerate to a high velocity, and on leaving the barrel the foam will fall away, leaving the dart to travel to a much longer distance than a section of potato would.


wasnt that posted some where else on here recently JSR?
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 13, 2008 9:07 am

Carlman wrote:wasnt that posted some where else on here recently JSR?


Yep, what's wrong with spreading the word :p :D
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Unread postAuthor: SpudChucker24 » Wed Feb 13, 2008 9:21 am

Ya that was the point of the mesh. I didnt think i could get 1000. If i did all the simple upgrades (ex. sabot, fan, use propane) i might be able too. I might be making the barrel longer but how much longer should it be to get max power JSR?
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 13, 2008 9:28 am

SpudChucker24 wrote:how much longer should it be to get max power JSR?


There's no limit really, longer barrel = more power (as long as you maintain the c:b ratio, ie compensate for the length with greater chamber volume in the correct proportion) - so make it as long as you can afford ;)
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Unread postAuthor: jimmy101 » Wed Feb 13, 2008 11:43 am

Given your chamber dimensions (4x24) a 2"ID barrel should probably be around ten feet, that'll give a CB near 0.8.

Don't use mesh between the barrel and chamber, as the hot gases flow through the mesh you'll loose too much energy as heat transfer to the mesh. If you want an ammo stop just use a screw or piece of wire. Or, omit the stop and use a calibrated ramrod.

I would WAG the range at 600~800ft for a half spud launched at the optimal launch angle.

YMMV
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Unread postAuthor: potatoflinger » Wed Feb 13, 2008 12:20 pm

1000 feet is definitely possible, but you're going to need to make the barrel longer, and the chamber longer (like JSR said). I have a gun that GGDT says can hit over 1000 feet, but the gun has a 10 foot long barrel.
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Unread postAuthor: Jared Haehnel » Mon Feb 25, 2008 9:24 am

Alot of it would depend on what you trying to launch to hit 350yds (1000ft). I think you might be hard pressed with a spud. At least with a combustion. Use a screws instead of a mesh as a stop You can also precut your ram rod so it only goes so far.

Design you have now won't work.
Heres why...

Your barrel is too short. Longer barrel increased muzzle velocity. As long as its not to long.

Your barrel is probably too large in diameter. Meaning the objects you will launch probably will be to heavy or have a high drag coefficient. It will also take a longer barrel to reach the maximum muzzle velocity.

You don't have a chamber fan. A chamber fan will increase the efficiency of combustion. (read: higher chamber psi, less unburned fuel)

Also take into consideration the type of fuel to use. Regular hairspray makes a mess and may not do it for you


350 yards is easier to reach with a pneumatic cannon but its worth a shot.
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Unread postAuthor: jackssmirkingrevenge » Mon Feb 25, 2008 9:47 am

Your barrel is probably too large in diameter. Meaning the objects you will launch probably will be to heavy or have a high drag coefficient. It will also take a longer barrel to reach the maximum muzzle velocity.


This is the beauty of saboted rounds, with a large barrel you get a massive base area for the gasses to push on while the projectile is in the barrel, without the weight of a full bore projectile, which allows for greater acceleration. The instant it leaves the barrel, the sabot strips away and you're left with a streamlined projectile with low weight but a high sectional density.
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Unread postAuthor: Jared Haehnel » Mon Feb 25, 2008 10:47 am

I agree. I guess the next question is what is he planning on launching 350 yards?
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Unread postAuthor: Carlman » Mon Feb 25, 2008 8:35 pm

jackssmirkingrevenge wrote:Image
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Unread postAuthor: chartreusesnot » Mon Feb 25, 2008 8:45 pm

The problem with a dart like that is it would be nigh impossible to find. Especially if its a thousand feet out. Could you get it to trail dust of something? just a thought. It would probably all strip off in te launch...
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