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New Nail Dart Design & Testing

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Unread postAuthor: spudtyrrant » Sat Nov 21, 2009 1:03 pm

well i can shoot nail darts out of a blowgun farther than i can see them, so i doubt that you will be able to find any you shoot
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Unread postAuthor: iknowmy3tables » Tue Nov 24, 2009 4:20 pm

tee hee dats my gun, so yeah the great thing about cartridges is that with they have freedom to load anything, and like in the deus ex machina the bolt stroke length does not necessarily have to be as long as the cartridge,

however don't think that gun with a long bolt stroke for none cartridge ammo has to have lots of dead space, you can reduce dead space by using a barrel sliding bolt in which the barrel slides forward to open and back to close, you can also use a system where the input enters from the side right behind the projectile when the bolt is closed, like in ben trettel's FANG

cartridge systems have their difficulties, for you idea you could try a special semi rigid sabot, you could try a set of inverted fins out into a mag friendly ammo, you could also have a detachable mag firearm style lay out in which ammo is pushed forward and up into the breech which could compensate for the narrower tips
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Unread postAuthor: inonickname » Wed Nov 25, 2009 4:20 am

Create a clip from something like a strip of clear tape to hold the darts together which is removed by the action of the bolt/firing perhaps?

Cartridges seem the other good way to go.
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New Nail Dart Design & Testing

Unread postAuthor: boyntonstu » Tue Dec 29, 2009 9:59 am

Image

Adding more cones pushes the cg forward and they stabilize the dart.

Hint: I use a short piece of "barrel" and a bench grinder to quickly fit the dart to the barrel.

Each cone acts like a piston ring and seals the dart to the barrel.

I shot one of these 3" 10d darts at 300 psi and it went through 4" of telephone books and 5/8" of plywood.

The 0.020" thick paper tail cones penetrated about 1-1/2" into the telephone book!

Next: 400 psi.

Edited by jrrdw.
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Unread postAuthor: Hubb » Tue Dec 29, 2009 10:18 am

These are cool. I notice in the picture that the first cone has a sort of flap. I'm not sure if this is intentional or not, but that little flap should add spin to the dart, right?
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Unread postAuthor: ramses » Tue Dec 29, 2009 10:25 am

Most likely, it gets pinned down from the air resistance, but it might add spin. It could also destabilize the projectile some by creating uneven drag.
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Unread postAuthor: boyntonstu » Tue Dec 29, 2009 10:47 am

Hubb wrote:These are cool. I notice in the picture that the first cone has a sort of flap. I'm not sure if this is intentional or not, but that little flap should add spin to the dart, right?


Exactly what I am attempting to do, spin it like a top.
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Unread postAuthor: Hubb » Tue Dec 29, 2009 11:19 am

I don't think this one little piece will make for an incredible amount of uneven drag. If Stu is penetrating this much, the tip is definitely going forward.

However, recently, I was reading up on how archers test arrows for just this. One of the things they do is to use a paper tear test. They will set up the target, then place a piece of paper in front of the target, then shoot the paper at a certain distance. If the hole is a clean one without any side tears, it indicates that the drag and stability of the shot is correct.

As far as the paper fin being pinned down, I can see this. If this is the case, it could be stiffened up a bit, say, by rubbing it with super glue or something? The archery studies have also indicated that stiffer stabilizers also lead to better stability during the flight of the arrow.
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Unread postAuthor: Marffy » Sat Jan 02, 2010 8:49 pm

cool, cool... so those darts can go through some telephone books and plywood at the same time?
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Unread postAuthor: boyntonstu » Sat Jan 02, 2010 11:55 pm

Marffy wrote:cool, cool... so those darts can go through some telephone books and plywood at the same time?


Yes. They penetrate 4" of telephone books and through 5/8" plywood in a single shot.

I would not like to be on the receiving end.
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Dart Stability Test

Unread postAuthor: boyntonstu » Sun Jan 03, 2010 8:27 pm

"There is a relatively simple test that you can use on a model rocket to determine the stability. Tie a string around the body tube at the location of the center of gravity. Be sure to have the parachute and the engine installed. Then swing the rocket in a circle around you while holding the other end of the string. After a few revolutions, if the nose points in the direction of the rotation, the rocket is stable and the center of pressure is below the center of gravity. If the rocket wobbles, or the tail points in the direction of rotation, the rocket is unstable. You can increase the stability by lowering the center of pressure, increasing the fin area, for example, or by raising the center of gravity, adding weight to the nose."

http://exploration.grc.nasa.gov/educati ... tstab.html
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Unread postAuthor: psycix » Mon Jan 04, 2010 6:52 am

Nice find!

Very simple test, yet very useful.
I'm going to use this one someday.
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Unread postAuthor: jackssmirkingrevenge » Mon Jan 04, 2010 7:16 am

Useful for large projectiles but not for the smaller darts we tend to shoot. You can do this more scientifically by comparing centre of drag to centre of pressure.
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I can use some ideas?//

Unread postAuthor: boyntonstu » Mon Jan 04, 2010 1:10 pm

I can shoot a 3" 10d nail dart at 100 psi with 100% reliability.

The dart flies straight and it easily penetrates 5/8" plywood.

Above 150 psi they do not go straight.

No cone blowout, just instability.

I have gone from 5" overall length to 8", no improvement.

I installed a muzzle brake, no improvement.

Theairgunman has demonstrated success using plastic 12 Gauge wads.

http://www.airgununiverse.net/community ... 180.0.html

"I made 5 paper cone darts and 5 shotgun wad darts. 4 out of the 5 shotgun wad darts shot nice and straight at 20 yards and buried the head into the 3/4" oak plywood at that range. One wasn't quite centered when I made it, I could notice it being off center when I loaded it. It still penetrated, but bent in half. It is in the top part of the picture I attached to this post. The paper cone darts I made were for the same barrel and they did not perform as well as the ones I made for the 3/4" copper barrel. So to be fair, I'm going to make 5 of them for the copper barrel and retest hopefully on Tuesday. Out of the ones I made for the 3/4" pvc barrel, only one hit and barely penetrated. That is the cone you see in the bottom of the picture. One of them blew apart and the others were not balanced and missed the target. So far, I'm liking the shotgun wad darts better, they are constructed in less than half the time of the paper darts and if you center them, they fly true. It is easy to check for centering by loading the dart in the barrel. If the nail is in the center of the barrel, it will fly true. I marked the 5 shots in the picture with red dots to make them easy to find. Note the mark that the wad leaves on the board. All shots were at 250 psi and 20 yards away."



It seems counter intuitive that a cylindrical wad would outperform a cone tail.

I would appreciate some of your ideas.

BTW Should the total area of outlet holes in a muzzle brake be proportional to the barrel area?
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Unread postAuthor: qwerty » Mon Jan 04, 2010 1:34 pm

How straight are you cutting the back of the dart? if it is not perfectly straight it wil not fly properly also, make the cone as neat as you can and the nail should be pointing exactly straight up as this will affect flight too.
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