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

[JDP12]

IIRC, ggdt predicts the muzzle energy of a round, like a gun

[jackssmirkingrevenge]

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

[jhalek90]

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.)

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.

[jackssmirkingrevenge]

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.

[jhalek90]

mkay.

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

Ill update with real numbers soon.

[Brian the brain]

Don't forget that area increases exponentially with area

so does adding increases to your lightness...



Any idea on when we can expect the cannon to be done?

[jhalek90]

that's exponential too?

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

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??

[jackssmirkingrevenge]

so does adding increases to your lightness...

*blink*

I really should sleep more

[MrCrowley]

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...

[jackssmirkingrevenge]

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...

hehe reminded me ofthis topic