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
Pneubmatic 8,999 (now with Science!)
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Fnord
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- 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 3080 times
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- Test bed. I added a plywood shield later to help stop the muzzle blast.
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- 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.
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Last edited by Fnord on Sat Mar 24, 2012 9:25 pm, edited 2 times in total.
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warhead052
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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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jackssmirkingrevenge
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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.
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.
hectmarr wrote:You have to make many weapons, because this field is long and short life
nice video. The death metal was rather... metal-ly.
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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jackssmirkingrevenge
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After having skimmed through this, now I had a good look:
a) lolol @ the trollfoot
b) shooting liquid targets indoors. Wonderful
a) lolol @ the trollfoot
b) shooting liquid targets indoors. Wonderful
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Fnord
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Probably just some small penetrator rounds for now. It would be interesting to see how much steel you could punch through with only 200JAnything in particular you will be testing with it? Oh and the bacon was a nice touch...
Nice touch? It's the bloody scale! Derp!
Some day I'd like to do a HGDT version, though burst disks would probably be the limiting factor.Very good test! I love to see a good GGDTvsReality test.
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.b) shooting liquid targets indoors. Wonderful
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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Fnord
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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.
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