Homemade Bladders, For a homemade auto Options

[nerfboi]

I remember seeing a homade that was pump action and I saw a mountain dew 2 liter bottle on it.
So im guessing you could use a soda bottle as a blader

[King Of Butt Land]

Your retarded. Not to flame but I wouldn't give people advise that is not legit.

-Butt

[Dart Attack]

A bottle would just Break

This post has been edited by Dart Attack: Feb 18 2007, 01:01 PM

[nerfboi]

Ok I was just throwing ideas out sorry.

[sam]

Actually pop bottles can hold around 120psi. I wouldn't put that much in them but they are usable as airtanks. Carrtoon modded his AT3K so that it was semi-auto using pop bottles. The bottles had schrader valves on the caps so that he could switch bottles really easy. He got about 4 shots from a 20 oz. bottle and about 8 from a 2 liter.

[nerfboi]

Actually pop bottles can hold around 120psi. I wouldn't put that much in them but they are usable as airtanks. Carrtoon modded his AT3K so that it was semi-auto using pop bottles. The bottles had schrader valves on the caps so that he could switch bottles really easy. He got about 4 shots from a 20 oz. bottle and about 8 from a 2 liter.

AHA!!! I told you!!!

[Retiate]

Actually pop bottles can hold around 120psi. I wouldn't put that much in them but they are usable as airtanks. Carrtoon modded his AT3K so that it was semi-auto using pop bottles. The bottles had schrader valves on the caps so that he could switch bottles really easy. He got about 4 shots from a 20 oz. bottle and about 8 from a 2 liter.

AHA!!! I told you!!!

But he was looking for a bladder, not an air tank. But I like that bottle idea...

[Prometheus]

Ok, just to clarify what stuff really is. Bladder - think of where your piss is, and how it feels good when it all comes gushing out. Ok? it's expandable. I've never seen an expandable pop bottle. That would be called an air tank. And whoever said that the bottle would break - just go hide in a corner. Wikipedia has detailed info on pop-bottle rockets, and various pressures used. 60 psi will not break a bottle, unless it has been previously damaged.

[Flaming Hilt]

I recently talked to my dad about this; he's an engineer. He suggested building an accumulator.

What an accumulator is is a tank that is always pressurized via air or a spring. Inside of this tank is your bladder.

How it works: the accumulator is always putting pressure (say 30 psi) on your bladder. Your bladder will not expand ridiculously until it can overcome the pressure in the accumulator. It's hard to explain how, but because of this, the pressure in the bladder will jump to 30 very fast and stay there for a long time.
IE:
1 pump -- 15 psi
2 pumps -- 28 psi
3 pumps -- 29 psi
4 pumps -- 30 psi
5 pumps -- 30.5 psi
etc. etc.

This helps because with a regular bladder, the pressure would advance at regular intervals:
1 pump -- 5 psi
2 pumps -- 10 psi
3 pumps -- 15 psi
4 pumps -- 20 psi
5 pumps -- 25 psi

until it burst.

This HELPS because then all your shots go equal distances. The last shot will have less air, but because it's in an accumulator, have just as much pressure as the first.

And that's how it works. So basically, make a PVC tube for the accumulator, run some latex tubing through it as the bladder, and then seal and pressurize the accumulator.

Otherwise, just latex tubing is what I suggest... but without an accumulator, the distances of the shots will vary greatly (as seen in a MS or PC).

[elf_avec_gun]

FH THAT'S BRILLIANT!!!

Does anyone else feel stupid for not having thought of that?

I know that you and your dad aren't on the best of terms, but I would still like to meet the guy sometime.

[Doom]

That's a neat idea, but the bladder's have fairly constant pressure to begin with. That's why they used the bladder in the CPS (which stands for constant pressure system) Super Soakers and the Nerf Wildfire/Powerclip to begin with. Pressure drops in rigid air tanks, not bladders. I could explain how, but I don't have enough time right now. The pressure stays relatively constant except for when the air is very low or the bladder is near bursting. The distances of your Powerclip should not vary greatly. If they do, I think there has to be some other problem.

Regardless, putting a latex tube inside of a rigid air tank is a bad idea. First off, the pressurized air on the other side of the tube is not good for the tubing. That will reduce the life of the bladder further. The bladders simply require replacement after a certain number of expansions due to thinning and tearing of the rubber from the expansions. This pressurized container will have to allow for replacement of the bladder, which can be done with a threaded fitting. That however makes installation of the bladder difficult due to twisting. It's not a good idea obviously.

I see that idea often when someone is looking for more power in a water gun, but it's a bad idea to begin with as I already explained. There's another reason however. The pressure on the outside drops, which would turn a CPS water gun into one that performs like an air pressure one. That makes a big difference in water guns and for multiple shots in Nerf guns. So, the idea wouldn't even make the pressure more constant. In fact, it would make it less constant. You could simply layer more tubes over the inside tube if you wanted more power.

Generally, people don't seem to understand how bladders work. I should set up a webpage explaining everything about latex tubes and their use as pressure bladders in water guns and Nerf guns. I seem to be one of the few who actually has any experience with latex tubing.

This post has been edited by Doom: Jan 18 2007, 05:06 PM

[Flaming Hilt]

That doesn't... make sense. Especially considering my dad is a bachelor's and his job was to test things like this and make them better.

Background aside... the distances of everybody's PC/MS varies greatly by shot. RF20's, too. I have never seen a range post on a full auto that says something like: 50, 50, 48, 49, 51, 47, 53, 51, 50...
It's always more like: 50, 48, 45, 43, 38, 35...
In which case, maybe Nerf doesn't use this "CPS" you speak of.

You are correct that pressure drops in rigid air tanks. However, it also drops in bladders -- though less. Ever blown up a balloon? It's real easy at first, but as you get to the end, it gets harder and harder until it's impossible. Yes, the impossible part is due to the fact that the balloon just isn't big enough to hold more, but the harder and harder part is because the pressure inside is increasing: it is changing. Again, less than a rigid tank, but more so than in an accumulator all the same.

I think it's debatable that a bladder inside an accumulator would need more replacement. Remember, because of the pressure on the outside, it doesn't have to expand (stretch/tear/etc) as much to achieve the same amount of pressure. True that the constant pressure on the outside would wear it a little, but better on the outside going in than on the inside going out, as anyone who knows basic laws of stress on circles knows. I think that because of the increased stress on the outside but the decreased stress of expansion, it would have just the same wear and tear of a regular bladder.

If it does require more replacement, that's fine with me. I'd rather have a gun that shoots well and needs slightly more maintenance than the vice versa. The twisting wouldn't affect the bladder because it's being twisted through air (the PVC (or whatever one chooses to use) is twisting, not the bladder), and then when it is internally installed you could just add a hose to the barrel/pump.

Don't get too ahead of yourself. I believe that you are smart and probably do have more experience than most of us, but remember that the world of pressure and physics (especially on something like latex) is a complicated one indeed.

[Doom]

Makes no sense? Read what I said and everything below.

If your dad has a bachelor's degree in any engineering field and he suggested anything to make the pressure more constant in rubber tubing, he obviously has no experience with rubber tubing. They don't teach classes about this. In fact, I very highly doubt he ever saw such a material used in such a way before. I went to a forum about latex tubing and asked about the force applied from the tubing to a fluid on the inside (important in water guns), and I didn't get a straight answer from the experts. There is simply no way to learn about how this tubing operates aside from using it.

Sure, I'm just a high school student, but I ain't stupid. I take that "I believe you are smart" crap to doubt my knowledge. I'm just about the only person on the internet with experience in using latex tubing for homemade water guns and Nerf guns. I beat people to use latex tubing in both by years. I think you should take my word for it. I'm not out here just to tell people they're wrong. I'm here to tell people what's right.

You don't know me very well because I don't post here very often. But, I've built things more advanced than you know. Check out this directory and look at the supercannon, supercap, and semiauto/semiauto2 directories. How's that for my credentials? The simple fact is that I know what I'm talking about from experience. I have experience with most everything in Nerf and water guns. And that doesn't even take into account the physics and math classes I've taken.

If you can point out posts or do a study that verifies your claim that the range drops that significantly, that would help your argument. But, the simple fact is that the range does not drop that significantly, and pressurizing the outside will not make the range more constant, rather, it will make it less constant. The ranges you posted are biased.

The range will drop, but not significantly. It will drop significantly for the last few shots. I've only used a Wildfire, so I only can speak about that. I do know that the first few shots were more powerful than the last ones. But, this does not have very many shots because the bladder is very small. You will see a much more constant pressure for longer tubes, such as the Nerf homemade I made. The pressure however is still slowly dropping as verified in a very long shot duration water gun I made back in 2004. It does not drop significantly, so it does not need any sort of "accumulator," not that the system you proposed would make it more constant anyway. Any long tube is very good for constant pressure. The pressure does drop, and it is shown more obviously in shorter tubes.

So do I know about your balloon example? Yes I do. But it's not a significant drop in pressure as I said in my post. Perhaps I should have clarified by saying that pressure drops in bladders, but much much less significantly in bladders in that one sentence.

This is because the tube operates on the expansion of the rubber. Once the tube reaches a critical pressure, the tube expands. At that point, it's the tension between the rubber and the air that is creating the pressure, and the pressure is relatively constant. The air can expand. Attach a pressure gauge to a tube and you will see this verified. The pressure will increase when the tube is getting close to poping because the air has no where else to go - like in a rigid tank. That is why the pressure does not fluctuate and it also is why they used rubber tubes in water guns and Nerf guns with extended shots.

Stretching rubber tubing puts stress on it. It slowly tears the rubber. The rubber thins. Some spots, even with the best precautions taken to keep the stress over the entire bladder even, will be used more often than others simply due to the way the tubing expands (from one end to another). Those spots will be where the tube will pop. I've seen it happen before. Pressurizing the outside will put more stress on the bladder. It might not really make that much of a difference, but it won't work to do what you think it will anyway, so it's not even worth it.

The twisting wouldn't affect the bladder because it's being twisted through air (the PVC (or whatever one chooses to use) is twisting, not the bladder), and then when it is internally installed you could just add a hose to the barrel/pump.

Yes, this is something I should have mentioned. I was thinking of attaching barbs to both sides as to make it use space more efficiently. Don't know why I didn't consider that in my post.

Anyway, I invite you to try what you have described. You'll see that everything I've told you is correct. It simply would be a waste of time not only because it would not perform what it was set out to, but it also would be hard to maintain. It will actually make the pressure less constant. I have no doubts about that. Physics is indeed a complicated world, which is why you should trust someone who knows.

I don't know, but you came across as offended when I read your post. Please realize that I am not trying to offend people. I'm only looking to tell people what will work and what won't. Your idea won't. Take it from someone who knows what they are talking about.

This post has been edited by Doom: Jan 19 2007, 02:22 PM