8 replies to this topic

[InkJet]

So, recently i've made an air powered nerf gun out of pvc. I've made some pneumatic guns in the past, so this wasn't very hard. I made a 1.5" pressure tank, a sprinkler valve, and then a female threaded part for attaching multiple barrels. So far, i've made 3 barrels, one with 9/16" brass in 1/2" pvc, the next 1/2" cpvc in 1/2" pvc, then the last 1/2" pvc. The first is for micro stefans, the next for noodle missiles, and the last for shooting stock micros. I got the idea from someone else on this forum, but basically i put some electrical tape on the cpvc so it fit in the noodles hole (hehe).

Now, when i fire stefans or stock micros out, this thing goes farther than any other thing i've seen, but when i shoot a noodle, no matter how many pumps, it goes about 7-10 feet with a *pthooom*. I'm not sure what to try next, i tried putting duct tape around the noodle so the air couldn't rush out of the foam as easy, but that didn't seem to help. I tried releasing the air slower from the valve, didn't work. All i can think of is to make a bigger air tank. Any suggestions? Oh yeah, pics, i almost forgot pics.

Edited by InkJet, 30 August 2006 - 09:41 PM.

[WratH]

By the looks of it your foam isn't weighted, so it just spins out. For it to go in a straight line(and thus, far) there has to be stabilization. There are a few ways you can do this. The first way, the most common around here too, is to make your projectile front-weighted. You can make it like a stefan, with something like a marble(but make sure it is stuck in the noodle like a muthafucka) covered with hot glue or whatever you can think of. Another way is to have fletching. If you look at nerf arrows, they have fins that make them fly in a straight line. The fins also act to induce my third example, which is this; Making your projectile spin. If you look at modern rifle ammunition, it is not front weighted nor does it have fletching, it spins at such a high speed that it goes in a straight line(someone who has some expierience with this may tell you, but I don't exactly know why). So it is your choice, but your projectile must be stabilized somehow. Good luck.

[Flaming Hilt]

First thing I'd do is get a barrel material that better fits the noodles. Because honestly, having a 1-cm segment of e-tape is like having a 1-cm barrel, but since your projectile slides over it, it creates drag as the back is pushed over. I'd either e-tape the whole thing, find a different barrel material, or use no e-tape at all.

As for spin...

(someone who has some expierience with this may tell you, but I don't exactly know why)

First off -- I'm sure he knew this but just forgot to mention it -- the reason the bullet spins is because there are grooves on the inside of the barrel that spin the bullet before it exits.

As to the reason this makes the bullet fly straight, it's because anything spinning creates an inbalanced air flow. This means that there will be low pressure on one side, and high pressure on the other. High pressure moves towards low pressure; so anytime the bullet deviates, pressure movement will put it back on course.

[InkJet]

Well, it is weighted. I followed someone elses instructions, and basically wrapped some foam sheet around my FBR and pushed it down the hole so i had about a 1" deep hole. i filled this with steel bbs (.117), then put hot glue, then some FBR, then i just put craft foam on top to make it pretty. I'll try to tape the whole thing though, that makes sense to me.

I tried also forcing it on the 1/2" pvc barrel, which it fit tightly, and it seemed to go a tiny bit farther, but it sprayed me with little pieces of foam, so it tore up the inside, which i'm assuming is bad.

The fin idea seemed interesting, but my first requirement is that it gets some distance. How far does a stock titan shoot it's missile? I haven't forked out the 40$ for it yet. I'm just wondering what kind of performance i should be expecting.

Another idea i had was to try pipe insulation, because that would be made to fit around the 1/2" pvc, and i'm also assuming it's made from a different type of foam than the noodles. Another odd thing is that before i tried this, i used another pneumatic cannon with a big airtank and a 2.5" barrel, and jammed the noodle in. I pumped it 40 times with the bike pump (pant, pant) because i didn't feel like hooking up the air compressor, and it shot about 50-70 feet. My dad said that maybe the air has to be released slower, for some reasoning i can't remember. I'll try some of those ideas though.

[WratH]

If that is the case, you might just not have enough power. That is some pretty heavy ammo, and you need a lot of air to chuck it a decent distance. Your sprinkler valve might be opening too slow, in which case you'll have to mod it. The website eludes me right now but davidbowie might be able to help you.

[InkJet]

Ok, Thanks. I found the site, it's on spudfiles.com. I'll mess with that in a bit. I'm gonna try to make a semi auto valve with the tutorial on the homemades section of the site also, so i have some work ahead of me.

[davidbowie]

You'll probably want to put a bigger tank on, although you could do fine with what's on there already. What would probably help the most for noodles would be to put the e-tape ring right at the muzzle. Insulation would probably be better, though. The yellow jacket shot missiles about 50 feet with a much smaller tank and a 3/8" port ball valve, so I can't see why this shouldn't outperform a Titan.

[InkJet]

Ok, well, i was at the hardware store today, so i picked up some foam pipe insulation (along with some dremel cutting wheels and a butane torch). I got home, rolled some craft foam around a little FBR and then glued it in. Dropped 5 slingshot BBs in, then glue then rolled up craft sheet. Then, I tried adding 4 wings from foam sheet on it. Pumped it up 3 times, shot about 50 feet. Thought i could try more pressure, so i added 4 pumps, but when I fired that, it blew the seam on the foam. The pipe insulation seems thinner, that could maybe be part of it. I made another and hot glued the seam, then wrapped it in duct tape, weighted it, added 3 fins.
Any other ideas to seal the seam?

Now my only problem is that the pressure valve in the gun leaks around it, and my dad keeps telling me plumber's goop or silicone won't seal it, so i'm gonna try those, if those don't work, i'll have to scrap the whole pressure chamber and start over with automotive pressure valves.

Pics

Yes, that's hot glue to seal, worked at first, but stopped working.


Took off some tape to make the insulation fit, but it fits great now.


Missile loaded on

Edit: Messed with a pic, also, went to the hardware store, bought pipe fittings & some valves, popped one into the endcap, now the glue's all drying, let you all now how it works when it's dry.

Edited by InkJet, 02 September 2006 - 07:12 PM.

[davidbowie]

Nice!

You're going to have to pump that seam full of hot glue if you want the missiles to hold together, but it shouldn't give you any problems afterwards.

Your missiles look WAY better than mine ever have.