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New and the last gun design.

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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New and the last gun design.

Unread postAuthor: Mitchza89 » Sun Jan 20, 2008 1:59 am

Well this is my latest design for this will be one of my last guns. It's based off the S400 and the SSS that Chaos previously built. I hate copying designs at all but his design is the most practical and clean for me. I take my hat off to Choas for first making what he did.

This is the idea I had planned:
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Unread postAuthor: Zen/// » Sun Jan 20, 2008 2:10 am

Dident you call your last gun "the last gun"?

Just check GGDT to optimize it before you start building.
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Unread postAuthor: Mitchza89 » Sun Jan 20, 2008 2:13 am

Yeah "the last gun" was my last small bore, this will be my last larger bore gun ;)
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Unread postAuthor: Novacastrian » Sun Jan 20, 2008 2:46 am

Looks good, Chaos will be proud!
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Unread postAuthor: Mitchza89 » Sun Jan 20, 2008 3:02 am

Cheers mate, thanks alot. Can anyone see anything that I could do to improve the design? I'm thinking of getting some 1/4'' copper tube and running that along the gun from the blowgun to the piston valve. it should give it a really nice look and feel. :D

Edit: Velocity told by GGDT:

100psi: 560fps
200psi: 747fps
300psi: 866fps

Not too great :(....
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Unread postAuthor: ALIHISGREAT » Sun Jan 20, 2008 5:16 am

to imporve the design... hmmm well a QEV pilot would be a start if you are running at suitable pressures and the barrel obviously could be longer... and if you ditch the stock you could make the barrel longer, but the one thing i would reccomend to up the power is to up the pressure.

p.s. whats the ammo you will be using?
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Unread postAuthor: Mitchza89 » Sun Jan 20, 2008 5:18 am

Well 300psi is about as high as I would go, maybe 350 if the pump I'm gonna make can take it. Qev's are very expensive to get in Aus :( I'm gonna make the barrel 120cm instead of 100cm and take the chamber from 50cm to 75cm.

Primarily, marbles will be what's used.
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Unread postAuthor: ALIHISGREAT » Sun Jan 20, 2008 5:28 am

Mitchza89 wrote:Well 300psi is about as high as I would go, maybe 350 if the pump I'm gonna make can take it. Qev's are very expensive to get in Aus :( I'm gonna make the barrel 120cm instead of 100cm and take the chamber from 50cm to 75cm.

Primarily, marbles will be what's used.


hmm marbles so they are about 7g.... well i have been planning something similar for a while and i'm using a 20mm copper barrel but 150cm long and i'm using a 28mm x 22mm x 28mm reducing tee (barrel side will be 22mm) with a 25mm piston and a 50cm x 28mm copper chamber at 400psi piloted by a 1/2" qev which won't be that much more powerful than your design because i think pneumatics reach a point where it is very hard to go over because normal air is reluctant to go over the spped of sound :roll:
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Unread postAuthor: Mitchza89 » Sun Jan 20, 2008 5:32 am

:? 7grams?! I was told a standard glass marble was only 4... Hmm... Your gun at 400psi will be absolutely insane. When is the release date for this beast?
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Unread postAuthor: ALIHISGREAT » Sun Jan 20, 2008 5:57 am

Mitchza89 wrote::? 7grams?! I was told a standard glass marble was only 4... Hmm... Your gun at 400psi will be absolutely insane. When is the release date for this beast?


hmm i though it was paintballs that were in the 3-4g region :? maybe i'm wrong.... and i'm still thinking about whether the cannon will be worh the cost (which is alot :cry:) but i will hopefully order the parts soon... and yes it will be insane... more power than a .22 rifle :twisted:
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Unread postAuthor: Mitchza89 » Sun Jan 20, 2008 6:01 am

Hmm with the gun I'm gonna build, what do you think the penetration will be like with a marble at 300psi?
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Unread postAuthor: ALIHISGREAT » Sun Jan 20, 2008 6:10 am

Mitchza89 wrote:Hmm with the gun I'm gonna build, what do you think the penetration will be like with a marble at 300psi?


well a marble at 300psi will be going at 866fps according yo your calculations but i really don't have a clue about penatration but i can work out muzzle energy and momentum?

muzzle energy= just over 100ft/lbs

momentum= 0.004kg*264m/s= 1.056kgm/s
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Unread postAuthor: Mitchza89 » Sun Jan 20, 2008 6:11 am

Haha well is 1.056kgm/s good? :P
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Unread postAuthor: ALIHISGREAT » Sun Jan 20, 2008 6:15 am

well i will get 2.something kgm/s with a 7g projectile fired from my 400psi beast (hopefully) so no :P thats because you will be firing a lighter projectile slower (a 4g projectile at 264m/s) wheras i will be firing a heavier projectlie faster (7g at 304m/s)

i might go work out how much momentum DYI's sbtakkankvnfk has...

edit: although the marbles fired from your gun will have more momentum (just) than .22 rifle bullets

40grain= 0.858kgm/s
38grain high velocity= 0.95kgm/s
31grain high velocity= 0.88kgm/s
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Unread postAuthor: SpudBlaster15 » Sun Jan 20, 2008 2:50 pm

ALIHISGREAT, do you even have a clue how momentum correlates to penetration? Or are you just spouting off numbers in an attempt to appear intelligent? Because I am quite sure you have no idea what your numbers mean.

Penetration is directly related to energy density, not momentum. The difference? Well, take a look at the equations;
E<sub>k</sub> = 1/2m*v<sup>2</sup>
p = m*v

With this info, we can write;

Momentum is directly proportional to mass, and directly proportional to velocity.

Kinetic energy is directly proportional to mass, and directly proportional to the square of velocity.

See the difference? Using velocity as a 1st degree term in any equation that attempts to calculate penetration will give you some pretty whacked out results.

So, back to energy density. Well, energy density is kinetic energy divided by the cross sectional area of the projectile, which will yield a result in Joules per square centimeter. This means that we can write;

E<sub>D</sub> = 1/2m*v<sup>2</sup>/(pi*r<sup>2</sup>)

Solving for your launcher and ammo, we get;

E<sub>D</sub> = 1/2(0.004kg)*(264m/s)<sup>2</sup>/(pi*(0.8cm)<sup>2</sup>)
E<sub>D</sub> = 69J/cm<sup>2</sup>

Comparatively, a .22LR rifle yields;

E<sub>D</sub> = 1/2(0.0026kg)*(330m/s)<sup>2</sup>/(pi*(0.28cm)<sup>2</sup>)
E<sub>D</sub> = 575J/cm<sup>2</sup>

A .22LR will out penetrate your launcher by a factor of ~8, but the overall energy transfer to the target (assuming no overpenetration) will be very similar.
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