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Second Cannon

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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Second Cannon

Unread postAuthor: CYANIDEGENOCIDE » Mon Nov 03, 2008 10:45 am

My first was a pneumatic running a 3/4" rain bird valve with a 3"x 3' chamber feeding a 1.5" barrel. A little tailoring of the ammo got it to punch through cinder blocks (not assembled as a wall). That was at about 110 psi from 75 feet.

This second cannon is a 4 chamber pneumatic 4 1" rainbird valves (still running electric solenoids) testing has been at 90-100 psi. The chambers are 5' x 4" schedule 40. The barrel is 10' x 2" Its heavy and a pain to move. I have used for ammo, cast concrete slugs, rebar, copper pipe filled with polymer modified cement, an electric motor, and military flechettes.

The only things to penetrate a block wall was the electric motor, but only the front of the wall; and the flechettes which stuck in the wall and in an aluminum ladder. The testing was from 100'
here are some pics.

the cannon
Image
the motor after firing
Image
the hole from the motor
Image
the flechettes in a foam sabot
Image
the flechettes about 1/4" deep in the wall
Image
the flechette fin deep in the ladder
Image
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Last edited by CYANIDEGENOCIDE on Mon Nov 03, 2008 11:16 am, edited 1 time in total.

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Unread postAuthor: RabidDuck » Mon Nov 03, 2008 11:07 am

Wow! Looks awesome. Also is very powerful. Cool cannon.
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 03, 2008 11:20 am

Fork in hell, this is the first time I've seen actual surplus flechettes used in a spudgun, good stuff!

I'm sure many would agree though that you should at least pneumatically mod the sprinkler valves. In general, one would advise against multiple valves, due to variations in opening time and associated turbulence.

Consider making a single chambered piston valved launcher, it would be a lot more compact and likely more powerful. You can also get 3" sprinkler valves if you want to avoid the complication of making your own piston, and they work ;)
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Unread postAuthor: CYANIDEGENOCIDE » Mon Nov 03, 2008 4:49 pm

Thanks for the positive reviews so far. I intend to pneumatically mod the valves but I was just dying to try this out! This is actually a runner up design, I had a 2" QEV from some industrial application lined up but it never materialized from the source. I went with 4 1 inch valves because I didn't want to pay for bronze 2 inch valves and I honestly didn't know about 3" valves until JSR pointed them out. I don't feel comfortable making a piston gun (yet). There are a few items left that could increase the performance:
1 Run the pressure up to 150 psi
2 fin stabilized discarding sabot projectiles (Im thinking 12" nail with a hardened point and some sheet metal fins)
3 mod up the valves
4 get a scale and figure out where the optimum weight/velocity combo is
5 calculate up the sectional densities of my projectiles

Ideally I want to punch completely through the wall with 1 shot. Otherwise I am going to look bad compared to my brothers in law (they are working on a bowling ball throwing trebuchet)
any other ideas to increase penetration or power would be appreciated
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Unread postAuthor: VH_man » Mon Nov 03, 2008 5:50 pm

Whered you get those Fletchettes?!?!

I need some. Now.

And for Answers:

1. Yes, that will definetly Help
2. That will, with no doubt, penetrate VERY far.
3. You might be suprised at how much more power you get from modding your valves..... It suprised me the first time i did it.
4. Use GGDT to find your optimum Weight Figures, However I would always go for Muzzle Enegry Over velocity for penetration, AKA heavier is better, to a point.
5. I dont know..... What is that? Sounds kinda cool......
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Unread postAuthor: psycix » Mon Nov 03, 2008 6:05 pm

I like your choice of ammo. Those flechettes are great and heck, a whole electric motor?, why not?

Modding the valves will most likely give alot of performance increase, especially if you increase the pressure.
Any idea how you were going to pilot 4 valves? (the drawback of multiple valves!) Beware of excessive pilot volume!


Too bad the gun cant be handheld though.
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Unread postAuthor: FishBoy » Mon Nov 03, 2008 6:28 pm

very nice gun you have there. I agree with the others that if you modified the sprinkler valves they would open faster, and whatever else was said but aside from that, what are those fletchettes for and where did you get them????
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Unread postAuthor: CYANIDEGENOCIDE » Mon Nov 03, 2008 9:37 pm

The flechettes seem to be on everyone's mind so here's the dope. The US military originally designed them for use in 155mm artillery "beehive" rounds (called beehive because thats what 1,000 of these raining down on you would sound like). The military decided these would be great as a shotgun load, they weren't. They open to a very wide pattern and while they will defeat body armor and drill into bone they just don't cause a big enough wound channel to readily kill. You can pick them up from www.gunbroker.com (you have to be 18 and register, its like Ebay for guns and gun stuff) buying them loose they go $15 for a pound which is like 300-400. There are lots of places that will ship them to you, you just have to know what to look for; flechettes or satan's toothpicks
from wiki:
Sectional density is the ratio of an object's weight to its cross-sectional area. It conveys the ability for an object to overcome resistance. When a projectile is in flight or impacting an object, it is the sectional density of that projectile which will determine how efficiently it can overcome the resistance to air or object. The greater the sectional density is for a projectile the greater its efficiency is and therefore ability to overcome the resistance of air and object.

Sectional density is stated as: SD=M/A
SD = Sectional Density
M = Mass of the object, kg or lb
A = cross-sectional area, m2 or in2

As far as piloting 4 valves I figured a 1/4 line run to each valve plumbed to a common manifold with a single valve should do it. Just a few minutes with hose barbs and vinyl should straighten it out. I tried to use ggdt, but I was in a hurry to get out of work so I think I screwed up a variable, it told me my gun is FAIL (maybe its suck but not fail)
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Unread postAuthor: POLAND_SPUD » Mon Nov 03, 2008 10:14 pm

yeah those flachettes look really good... AFAIK there are bigger ones as well...:twisted:

I'd love to have them :D unfortunatelly shipping them from the USA would cost a lot


as far as the launcher is concerned I've notice that it has huge chamber volume.. it's a real overkill... I suppose that it would be almost as powerfull if it had only one chamber and a modded spinkler valve (plus it could be portable)
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Unread postAuthor: jackssmirkingrevenge » Tue Nov 04, 2008 12:17 am

CYANIDEGENOCIDE wrote:The US military originally designed them for use in 155mm artillery "beehive" rounds (called beehive because thats what 1,000 of these raining down on you would sound like)


It was actually used mostly in the 105mm gun:

Image

Each flechette only ways around as much as a 0.177 airgun pellet, however there were 9,000 in each shell, of which 6,000 were loaded normally, while 3,000 were loaded back-to-front, in such a way that they would flip end over end scything through the air in a brutal fashion.

I would go with all 4 valves connected to a common line attached to another modded sprinkler valve for piloting, keeping the line as short and low volume as possible.

If you are having problems with GGDT, post a pic of your results ("print screen" then paste in MS paint or similar) and we'll be more than happy to help you out.

As to ideal saboted projectiles, this is a design that has worked well for me:

Image

The oversize fins are enough to steady the projectile in the barrel, meaning your sabot has to be nothing more than a simple disk. You can also use thinner fins then suplement them with a second set of fins in the mid-section.
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Unread postAuthor: CYANIDEGENOCIDE » Tue Nov 04, 2008 4:16 pm

yes, 105 mm sorry for that, my memory was off.
Image
There's my ggdt read out, I have tried to optimize barrel size using the program and it seems the program is set up for guns using short large diameter barrels.
I was hoping to utilize a heavy projectile (something in the 3-5 pound range) with a long barrel so I could maxmize area under the acceleration curve by increasing the X component and a (comparatively) slower climbing Y. The idea being to give the compressed gas more time to expand. I am beginning to think this was a misguided effort. :(
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Unread postAuthor: VH_man » Tue Nov 04, 2008 4:22 pm

Dont mind the Choking Flow thing. It doesnt really matter. Just look at your Muzzle energy and then check a list of modern firearms.....

AKA, thats a HELL of alot of muzzle energy. Stick with it.
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Unread postAuthor: jackssmirkingrevenge » Tue Nov 04, 2008 4:44 pm

Nothing wrong with the equivalent muzzle energy of a 6 round burst from a thompson submachinegun ;)

Change the seat diameter to 1 inch, and the bore diameter to 2 inches.

The "choking flow" reference implies that you have more valve area than barrel area, meaning if you wanted you can afford a larger diameter barrel.
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Unread postAuthor: covey12 » Tue Nov 04, 2008 6:53 pm

that is total pownage, i would really like to know where you get flechettes from besides that website, can you buy them at a hunting store or something, ordering stuff online here cost a pain load, anyone know of any stores, maybe millitary surplus stores have them?
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Unread postAuthor: Ragnarok » Tue Nov 04, 2008 6:58 pm

Unfortunately, the issue is that his valve stats are more likely to be:
25% efficency, 1" seat, 12ms open time.

He hasn't changed the valve stats from the basic GGDT inputs. He's also misunderstood Inner and outer diameter.
I also seriously doubt the projectile weighs a full kilo, I have adjusted it for 100 grams - at the outside, I would say.

So, the numbers are actually significantly off - with those numbers corrected, GGDT predicts 1150 ft-lbs, and 580 ft-sec. That's still about the same as the NATO 5.56mm round, so not bad - better than I've ever done (bearing in mind that my cannons are pretty small)

@VH_Man: Velocity is more important than you think - if you hit fast, the target can't deform with the blow, absorbing the energy.
Velocity has a lot of importance.

That's why I've put paintballs WHOLE through 1mm steel plate with HEAL (running at 400 psi with a modification to my track pump) - within almost a walking pace of the sound barrier, they hit so fast, they simply don't have time to deform and break.
Only a very small percentage (a couple of percent at the outside, I've only ever seen it three times in hundreds of balls) come through in one piece, but I know they're whole by the patterns and dents they left in my backstop, and the complete lack of any paint around the hole they leave.
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