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Sneak peak of my new build. Pic of 4'' piston and 2.5"

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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Unread postAuthor: JDP12 » Sat Jan 02, 2010 11:05 pm

IIRC, ggdt predicts the muzzle energy of a round, like a gun
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 03, 2010 1:06 am

jhalek90 wrote:Yes, GGDT predicts around 300 ft/lbs of force at the muzzle.

Seems to me that that is a very high energy for such a low pressure.


That's what your typical handgun round generates (some comparisons here), but still for such a big launcher seems a bit low, what pressure is it at and what projectile weight?

Now here is a question that i have about gddt... is that ft/lbs propelling the projectile forewords? If so, does that mean the cannon will kick back at the same force per Newtonian physics?


Ft/lbs is the energy, recoil is concerned with momentum. In theory:

weight of projectile x velocity = weight of launcher x velocity

(for the sake of simplicity, I'm ignoring the mass of the air in the launcher that is also being fired out)

This means that if you fire a 0.5lb projectile at 500 feet per second, a 15lb launcher will try to recoil backwards at 17 feet per second. Not inconsiderable, so some sort of muzzle brake is advisable ;)
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Unread postAuthor: jhalek90 » Sun Jan 03, 2010 10:42 am

JSR, that 300 ft/lbs was at low velocity and low pressure

at a 120psi GGDT predicts somewhere around 545fps and 1200 ft/lbs
(Might be off a little, as i dont have the GGDT file open and am using my memory.) :shock:

1200 ft/lbs i think was if i used a lighter projectile as well.

I will have to re-model it in GGDT and toss the file up here.
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 03, 2010 11:14 am

jhalek90 wrote:1200 ft/lbs I think was ifI used a lighter projectile as well.


Usually with pneumatics the heavier the projectile the more the ft/lbs, even though velocity goes down.
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Unread postAuthor: jhalek90 » Sun Jan 03, 2010 9:15 pm

mkay.

Like i said.... im remodeling it soon.

Ill update with real numbers soon.
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Unread postAuthor: Brian the brain » Mon Jan 04, 2010 5:26 pm

Don't forget that area increases exponentially with area

:roll:

so does adding increases to your lightness... :D



Any idea on when we can expect the cannon to be done?
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: jhalek90 » Mon Jan 04, 2010 6:26 pm

that's exponential too? :o

(im bbq-ing STEAK!!!! woooo) :shock:

EDIT: on a real note...

No progress will be made until Thursday on the cannon itself :-(
i ran out of cannon funds.... dam u spudbucks.... why are you not worth anything??
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 05, 2010 1:08 am

Brian the brain wrote:so does adding increases to your lightness... :D


*blink*

I really should sleep more :? :roll:
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Unread postAuthor: MrCrowley » Tue Jan 05, 2010 1:53 am

jhalek90 wrote:dam u spudbucks.... why are you not worth anything??

Well they were, but then we started loaning them to banks and then the banks couldn't pay us back when we called in all our loans when JSR got drunk and started trying to double his contribution to Spudfiles overnight... :roll:
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 05, 2010 2:01 am

MrCrowley wrote:Well they were, but then we started loaning them to banks and then the banks couldn't pay us back when we called in all our loans when JSR got drunk and started trying to double his contribution to Spudfiles overnight... :roll:


hehe reminded me ofthis topic:D
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