29 replies to this topic

[Whisper101]

Hey all,

I was browsing youtube when I found this vid of a homemade nerf gun:

http://www.youtube.c...feature=related

I was sort of skeptical at this gun's durability: I'm not sure if the soda bottle ait tank will hold. I'm very interested in trying this mod out though because of it's apparent good ranges and low cost.

Any thoughts? The main thing that is troubling me here is that I just do not see how a soda bottle can be durable enough to function consistenly as an air tank in a powerful nerf gun.

Suggestions, advice, and comments are welcome.

Whisper...

[cheesypiza001]

It says, "We're sorry, the page you requested cannot be found."

[Hipponater]

It won't hold, and it is a terrible idea. The bottle just isn't meant to deal with that amount of pressure, and when it breaks, it's damn close to your body. A PVC tank would be a much better idea.

It says, "We're sorry, the page you requested cannot be found."

There's a couple extras http:// in front of the link

[ggk]

Here is that link
I dont see the point in making one because it would be banned. Mind as well just buy a cobra or something.

[Whisper101]

@ cheesy: I have the same probelm. Don't know why.

@Hipponater: yeah, that's what I was thinking. It's probably yhr kind of thig that work for about 10 shots and then blows up. Is a PVC tank just a length of PVC with 2 endcaps? I'll do some hunting...

[OnyxZenith]

The only reason I could see you making this, is that it would be 1) the first time that your making a homemade nerf gun or 2) you have PVC scraps and you are bored. But then again its a good concept to beginner homemade nerfers and then again homemades are meant for flaunt-ification purposes.

[Whisper101]

@ onyx: yeah, it would be my firts homemade.

[skatah]

Tried this once. I have a scar from a bottle explosion now.

[pjotrkuh]

Please keep in mind that when pvc fails, it produces much more sharp shards flying violently everywhere, carbonated soda bottles are designed to take some pressure, pvc is not!

[wingd man]

I can't say this is from personal experience, but you are probably not going to pump the gun before the PVC explodes, assuming you are not using large pieces of class 200.

[pinhead52]

Let's not forget that the same two liter bottles have been used in middle schools to make sweet pressurized rockets. Since PVC pipe is used for water, and even then rarely pressurized (actually if you do a quick search you will find that the US government has recently issued a warning that other types of piping should always be used in the case of pressurized gases), whereas the soda bottle is designed for just that, I would feel safe building one. I still would put some kind of housing around the tank, though. I don't like putting anything pressurized next to my body. It's one of my four disqualifying adjectives; Hot, sharp, fast moving, highly pressurized.

[Carbon]

PVC pipe almost always has a pressure rating printed on it, but even that assumes that you solvent-weld all your fittings perfectly.

Important footnote: that pressure rating is for fluid, not gas. PVC is not rated for air pressure (because of aforementioned ninja effects).

[Langley]

[Draconis]

Regardless of the dangers of PVC... Pop bottles? Seriously? Does anyone know how to say "ghetto" in noob-speak? I mean come ON.

[pjotrkuh]

Regardless of the dangers of PVC... Pop bottles? Seriously? Does anyone know how to say "ghetto" in noob-speak? I mean come ON.

I used small and even large soda bottles for replacement lego's pressure tanks.......although I used an OPRV to prevent popping hoses

Edited by pjotrkuh, 19 December 2009 - 05:23 AM.

[TantumBull]

While we're on the topic of the safety of pop bottles, I have a question.

Does anyone know if using something like fiberglass+epoxy to reinforce a 2 liter one will make it significantly safer to operate at higher pressures (ie will hold its own at higher pressures)? Would it be impractical to assume that covering all surface area on the bottle with fiberglass is possible?

And for making a safer explosion, what about using denim and duck tape? I know that doesn't work for PVC shrapnel, but this plastic is significantly lighter and thinner.

[OnyxZenith]

While we're on the topic of the safety of pop bottles, I have a question.

Does anyone know if using something like fiberglass+epoxy to reinforce a 2 liter one will make it significantly safer to operate at higher pressures (ie will hold its own at higher pressures)? Would it be impractical to assume that covering all surface area on the bottle with fiberglass is possible?

And for making a safer explosion, what about using denim and duck tape? I know that doesn't work for PVC shrapnel, but this plastic is significantly lighter and thinner.

Yeah Duct tape will work, IN THICK AMOUNTS (tightly) if your super cautious. OR maybe use an old pantleg and use that hahaha! then again like most plastic bottles if you popped one like those OZARKA water bottles, the'll just pop. and you can see where the air escaped through a slit like opening on the sides, and since they are SO thin, You can see if they're ready to pop or not after a few pumps

[pjotrkuh]

While we're on the topic of the safety of pop bottles, I have a question.

Does anyone know if using something like fiberglass+epoxy to reinforce a 2 liter one will make it significantly safer to operate at higher pressures (ie will hold its own at higher pressures)? Would it be impractical to assume that covering all surface area on the bottle with fiberglass is possible?

And for making a safer explosion, what about using denim and duck tape? I know that doesn't work for PVC shrapnel, but this plastic is significantly lighter and thinner.

Something hard like epoxy will actually make it more dangerous.

Duck/t tape wrapped tightly will actually make it more dangerous.

What you want to be looking for is to contain the explosion, not to stop it. I have done exactly that with denim and duct tape but NOT TIGHT. Layers, with some room to expand. Then zip it all into a backpack for more convenience and an additional layer.

Indeed, a backpack will be sufficient enough to contain an explosive decompression I think.......

An advantage of using soda bottles is that you can use another (smaller) bottle when you blew up your old one!!

[OnyxZenith]

While we're on the topic of the safety of pop bottles, I have a question.

Does anyone know if using something like fiberglass+epoxy to reinforce a 2 liter one will make it significantly safer to operate at higher pressures (ie will hold its own at higher pressures)? Would it be impractical to assume that covering all surface area on the bottle with fiberglass is possible?

And for making a safer explosion, what about using denim and duck tape? I know that doesn't work for PVC shrapnel, but this plastic is significantly lighter and thinner.

Something hard like epoxy will actually make it more dangerous.

Duck/t tape wrapped tightly will actually make it more dangerous.

What you want to be looking for is to contain the explosion, not to stop it. I have done exactly that with denim and duct tape but NOT TIGHT. Layers, with some room to expand. Then zip it all into a backpack for more convenience and an additional layer.

Indeed, a backpack will be sufficient enough to contain an explosive decompression I think.......

An advantage of using soda bottles is that you can use another (smaller) bottle when you blew up your old one!!

What about shelling the bottle with a PVC pipe that fits around it loosely? But I'm almost positive if the bottle bursts, the PVC will act as another tank because the air in the bottle escape and is now inside the PVC

and how come Tight Duct tape doesn't work? I've always imagined that the duct tape will keep the bottle together after it bursts?

[OnyxZenith]

Oh hey! I recently made a GUNBLADE with all 1/2 sch 80 (thickwalled) PVC and I've pumped it to about 40psi (thpump has a built in gauge) ... is that near exploding? Or can It take more? I'm not taking risks here. I'll upload a pic as soon as I'm done Christmas shopping

[Doom]

This discussion seems familiar... that's because I covered this in detail before: http://nerfhaven.com...ndpost&p=219400

Soda bottles are in general bad ideas. They're designed for temporary storage of low pressure with most of the bottle full of liquid. Liquids don't compress much and consequently they don't store much energy. In contrast, people here want to store relatively high gas pressures for an extended period of time. I call this a recipe for disaster.

Admittedly, soda bottle failures are fairly benign. I've seen the shrapnel and the explosions, and while it wouldn't be as bad as a PVC chamber failing, it's much more likely, and it still can cause very serious harm. A backpack probably would contain the shrapnel, but I'd do a number of tests to verify that rather than assume it does.

Bob's correct---wrapping something tightly around it will just make it fail more dangerously because it would fail at a higher pressure. Yes, it is likely to increase the failure pressure, but at the expense of a more dangerous burst.

If someone wants to shell a soda bottle in PVC, that's their decision. I think it's a thoroughly silly one. One reason people use soda bottles is because they are light. Adding PVC to the mix makes them heavier. And if there's PVC pipe involved, why not keep it simple with just a PVC tank?

Does anyone consider aluminum LPA tanks for gas storage? The one I have was dirt cheap, is extremely light, and has an operating pressure of 240 psi (the burst pressure is 600 psi). Ask a company that manufactures them for a quote price. I asked Catalina Cylinders as they aren't too far from the DC metro area.

@OnyxZenith: Do a Google search for something like pvc pipe sch 80 pressure rating. Harvel 1/2" sch. 80 PVC pipe has a water pressure rating of 850 psi (most manufacturers are the same). You have a safety factor of more than 10 over the pressure rating---this sounds plenty safe. You can use higher pressures.

Edited by Doom, 22 December 2009 - 12:27 PM.

[Draconis]

I have recently figured out that all three of the aluminum water bottles that I have use a thread pattern compatible with 3/4" NPT for the mouth. I have yet to test one under pressure, however. Might be worth a try. Also, I have two different fire extinguisher tanks that i am using, as outline in my homemade ballgun thread. They work well, and I've been able to get both for free. The threads in the neck are funny, though, and required use of a CGA580 coupling from the welding shop, for $6.

[CA13]

Soda bottles are meant for pressures up to about 15 psi or so. If you want a reservoir, find it in a segment of 2.5 in diameter PVC. With two endcaps.

[Whisper101]

And that'll consistently hold? We've had some differences of opinion on this matter...

[pinz321]

Seriously, I just don't know why nobody has thought of this: Just put the damned soda bottle inside, the PVC. No pressure in the PVC, so the PVC is your "guard" so when the tank does explode, you are unharmed. Seriously. And as I think someone said previously, why do you want to make one if they're pretty much banned everywhere?