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Pneubmatic 8,999 (now with Science!)

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Pneubmatic 8,999 (now with Science!)

Unread postAuthor: Fnord » Tue Mar 20, 2012 10:36 pm

Uh, yeah. I finally posted it.

I wanted a general use and test platform pneumatic so I made this. I have some experimental data at the end which I compared to GGDT predictions as best I could. The results lined up quite well and I believe most of inaccuracies were the result of my human-error in pressurizing the gun accurately and consistently.

Video link (with obligatory death metal, of course)


Note for D_hall:
I tried using your valve flow coefficient calculator, but it got through the first couple data sets then got stuck in an infinite loop for some reason.
Also kudos for making this thing so damn accurate. Tweaking the numbers sightly can get near perfect data alignment, but I believe the ones I used are the most representative of my gun.

Specs on the gun:
Chamber: 30 cubic inch
Barrel: 1.05" x 23.75"
Valve: 1.05" porting piston valve
Piston travel: about 1"
Piston mass: 98 grams
Pilot: 1/4" ballvalve

Maximum muzzle energy: ~160 Ft-lbs (217 J) with a 31 gram projectile, 160 psi
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Attachments
1floor.JPG
2floorJPG.jpg
4piston.JPG
Stainless and aluminum, floating oring. This was made with a hand drill before I got my drill press. And it was very intimidating sanding it down by hand while it was whirling away at 2000rpm.
3testsetup.JPG
Test bed. I added a plywood shield later to help stop the muzzle blast.
graph1.gif
Projectile weight was 31 grams.

*=Accidental overpressure; was not included in average
**= Erroneous chronograph reading; also was not included

Note the extreme consistency in the 100psi Column. I think this is because the '100psi' mark on my pump was bolded and very easy to see. I believe with a more accurate gauge I could get this gun to vary as little as 1 FPS between shots, no joke.
graph1.gif (36.54 KiB) Viewed 1497 times
34plywood.JPG
Last edited by Fnord on Sat Mar 24, 2012 9:25 pm, edited 2 times in total.
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Unread postAuthor: warhead052 » Tue Mar 20, 2012 10:40 pm

Very nice! Looks like a nice chunk of fun! Anything in particular you will be testing with it? Oh and the bacon was a nice touch, but you should have gone with tactical bacon
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Unread postAuthor: jackssmirkingrevenge » Wed Mar 21, 2012 12:51 am

Bacon!

I like the piston support.

Also, quite impressive energy levels for a pneumatic. With a 30 gram projectile in a 2 foot long 0.75" barrel with 12x in a 30mL chamber I got around 310 fps.
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Unread postAuthor: jhalek90 » Wed Mar 21, 2012 6:50 am

nice video. The death metal was rather... metal-ly.
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jackssmirkingrevenge wrote:I wonder... if you put flammable vapours inside a lady... could you get her to diesel?

POLAND_SPUD wrote:Anything is possible with the proper 3-way valve.
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Unread postAuthor: SpudFarm » Wed Mar 21, 2012 10:25 am

Very good test! I love to see a good GGDTvsReality test.

I also like your piston design, very neat and looks efficient.


(U mad?)
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"Made in France"
- A spud gun insurance.
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Unread postAuthor: jackssmirkingrevenge » Wed Mar 21, 2012 11:54 am

After having skimmed through this, now I had a good look:

a) lolol @ the trollfoot

b) shooting liquid targets indoors. Wonderful :D
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Unread postAuthor: Fnord » Wed Mar 21, 2012 5:57 pm

Anything in particular you will be testing with it? Oh and the bacon was a nice touch...


Probably just some small penetrator rounds for now. It would be interesting to see how much steel you could punch through with only 200J
Nice touch? It's the bloody scale! Derp!

:D

Very good test! I love to see a good GGDTvsReality test.


Some day I'd like to do a HGDT version, though burst disks would probably be the limiting factor.

b) shooting liquid targets indoors. Wonderful


There was a live 240volt plug right behind every one of those shots, and it got pretty well saturated... with me still walking around in the water. Microwave oven transformers, however, still scare the crap out of me.



Edit, oh and fun fact from the video:
In the first shot you can see the projectile bouncing back, and that particular trajectory gave it a hilariously perfect flight path toward my head, at maybe 20-30 fps. but luckily I managed to dodge it.. all those years of unreal tournament are finally paying off :)
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Unread postAuthor: Fnord » Fri Mar 23, 2012 11:27 am

Little penetration test for sh*ts n' giggles.

15 gram chunk of round file vs. 0.130" (3.3mm) mild steel. Technically made it through, but the 'exit' hole is only about 1/16" wide

The ducttape sabot weighed an additional 15 grams and separated on impact, so this was only the equivalent of 75 ft-lbs (~100) joules of kinetic energy against the target.
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entry holes are 0.2" wide
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