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Copper gun to fire 1 1/2" steel flechettes.

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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Copper gun to fire 1 1/2" steel flechettes.

Unread postAuthor: kiwi of nitro » Sat Jan 02, 2010 11:58 pm

Image

I just bought a 3/4" QEV from McMaster,

Should I use the QEV to fire the cannon or pilot a piston?

I want to fire these little flechettes, I just bought 100 of them.

And I bought 1lb of the 1" long kind flechettes.

What diameter and of what metal should my barrel be?

Thanks!
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 03, 2010 1:20 am

Nice!

Should I use the QEV to fire the cannon or pilot a piston?

What diameter and of what metal should my barrel be?


It depends on how you intend to use them. Because of the fins you'll definitely be needing some sort of sabot. Do you plan on firing them individually like an APFSDS round or putting multiple roundsin "beehive" fashion?
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Unread postAuthor: kiwi of nitro » Sun Jan 03, 2010 1:45 am

I want to fire them individually, Is it possible to get a barrel with just enough room for the fins and put wadding (like a cotton ball) behind them?

I don't know exactly how I would make a sabot for these...

Would wadding somehow make the flechette inaccurate after it leaves the barrel?

Could I cut potato cores or wax cores and then slice them in half down their length, using them to encase the flechettes fins?

If the sabot only contacts the flechettes shaft, I think it'll slide off in the barrel.

I don't know exactly how to make sabots that would stay intact while being fired, and not slip off the flechette. PLUS shed away after the flechette is airborne without affecting it's trajectory...
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Unread postAuthor: turner » Sun Jan 03, 2010 1:53 am

mabye that yellow expandable foam poured in the barrel then cut down the center to fly off in the air?\.
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 03, 2010 2:01 am

How about something like this, using say a 1/2" barrel and 1/2" dowel as a sabot. It comes in 2 parts, a simple half inch length goes to the rear of the fins, as a gas seal to push the flechette along. Another half inch length is drilled through the centre the same diameter as the flechette body, then cut in half and put around the flechette to stabilise it in the barrel.

As a lighter alternative to dowel you can use balsa wood, much lighter and easier to work with, and you can cut out appropriately sized sabots from a 1/2" thick sheet using the sharpened tube method (without cutting your fingers :P)
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Unread postAuthor: kiwi of nitro » Sun Jan 03, 2010 3:54 am

Of course! A gas seal AND a sabot! That is an absolutely awesome idea.

Did you make that diagram just now, the flechette looks exactly like the ones I ordered.

Thank you very much!

When this starts going together I'll post it in this thread.


Do you think I need to make a piston or should the QEV alone be enough to fire a single flechette out of a 1/4" barrel at the same velocity as a 3/4" piston? (I think they're small enough to fit in a 1/4" barrel, maybe a slightly larger one) I plan to use the highest pressures I can get, I have a CO2 regulator from Kobalt, it'll only do 120psi now, but I think I can modify it.
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 03, 2010 4:13 am

kiwi of nitro wrote:Did you make that diagram just now, the flechette looks exactly like the ones I ordered.


Yep, one gets handy with paint on this site ;)

Do you think I need to make a piston or should the QEV alone be enough to fire a single flechette out of a 1/4" barrel at the same velocity as a 3/4" piston? (I think they're small enough to fit in a 1/4" barrel, maybe a slightly larger one) I plan to use the highest pressures I can get, I have a CO2 regulator from Kobalt, it'll only do 120psi now, but I think I can modify it.


For a 1/2" or 1/4" barrel I would say use the QEV directly - a QEV after all is a commercially made piston valve. As to the calibre, it depends on the pressures you intend to use. If you're stuck with typical compressor pressures (150 psi or so) I would say go for the 1/2" to maximise your surface area, but if you can go higher (300-400 psi) I would go with the smaller barrel, it will probably be more accurate.
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Unread postAuthor: kiwi of nitro » Sun Jan 03, 2010 4:14 am

I guess I need to port the barrel to release pressure before the flechette exits, otherwise the blast of air will cause the flechette to yaw back and forth as it sails through the air...

I don't know exactly how to do this, but I think it might be necessary... Is it?
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 03, 2010 4:22 am

Probably not such a big deal, you could make an air stripper:

Image

but a series of barrel ports should suffice, you could even sheath the barrel et voila, integral suppressor ;)
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Unread postAuthor: kiwi of nitro » Sun Jan 03, 2010 4:37 am

Great, I think I can make an air-stripper out of some fittings using a dremel.
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Unread postAuthor: spudamine » Sun Jan 03, 2010 5:18 am

Isn' t there quite a chance that part of the sabot wil get caught on the edge of the air stripper? a simpler muzzle brake with smallish holes might be a better solution.
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Unread postAuthor: POLAND_SPUD » Sun Jan 03, 2010 11:28 am

And I bought 1lb of the 1" long kind flechettes.
what their mass, length and diameter ? anyone has any idea what their cd value is?

you know, I could compare them with a bb of the same diam in charigun pro to see how much better would they perform
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Unread postAuthor: ramses » Sun Jan 03, 2010 1:59 pm

Their BC should be quite high, maybe above 1. that puts the Cd very low.
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