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Pressure From Chemestry?


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#1 Ronnies07

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Posted 15 February 2007 - 10:12 PM

After reading Idea for powerful nerf gun, I can understand how this would NOT work, But what about other gas-releasing compounds? If you were able to exploit some of these chemical reactions this could mean REALLY high pressures.

Now after watching MythBusters I have learnt two things:
A 2 liter soda bottle ruptures at about 150 P.S.I., And that a small amount of Dry Ice and water can cause enough pressure to rupture one of these bottles. This means that pressures of 150+ P.S.I. can be achieved with minimal weight.

Now I understand that this is REALLY unsafe and shouldn't be tried, But it is an interesting concept.

And if that isn't extreme enough for you, you can make a potato cannon with a dart sized barrel. But I don't condone firing flaming bits of high velocity melted foam at your friends. :P
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#2 Uncle Hammer

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Posted 15 February 2007 - 11:30 PM

I love people like you. First off, you can't even spell chemistry right. Second off, combustion and nerf guns is stupid. Especially some sort of gas. That is too ineffecient and very dangerous.
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#3 Prometheus

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Posted 16 February 2007 - 09:01 AM

Ok, first, using gas releasing compounds would be very inefficient, as you need to carry around a large amount of them, and they need to be kept seperate from one another. Juts like baking soda and vinegar, you get a good amount of CO2 released, but you would need a more concentrated acid to react faster, and reduce the amount you are carrying around. Also, you would have to figure out the stoichiometric ratios and corresponding masses/volumes for this to be as efficient as possible (which is still fairly inefficient).

Second, Uncle Hammer, by calling nerf combustion guns stupid, you are therfore calling boltsniper stupid, since boltsniper built a combustion cannon. MANY, MANY people would love the opportunity to make you regret indirectly calling Bolty stupid. Me included. Show some respect for someone who is trying to be involved and explore different possibilities.
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#4 Ronnies07

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Posted 16 February 2007 - 09:03 AM

Well all I can say about the title is "Oops" But anyhow, Would it be practical to use a dry-ice + water combination to create high amounts of Co2 pressure?

And I do understand combustion is quite stupid. Not only will it deform the foam, but possibly ignite it and propel the ignited darts at high velocity. Really the only way I can see this working is if one uses a sabot.

Edited by Ronnies07, 16 February 2007 - 09:06 AM.

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#5 Prometheus

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Posted 16 February 2007 - 09:18 AM

dry ice and water wouldn't be too efficient either, because you need to have a ready supply of dry ice, which will need to be kept in a thermos or some form of insulating container, and you need to have a water supply also. for all the weight you will be carrying, you would be better off building General Primevil's SOBR-P or some other pump gun, which would be way lighter and alot faster to reload.
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#6 SHADOW HUNTER ALPHA

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Posted 16 February 2007 - 05:42 PM

Second, Uncle Hammer, by calling nerf combustion guns stupid, you are therfore calling boltsniper stupid, since boltsniper built a combustion cannon.


He didn't in any way call boltsniper stupid. He (and I agree) called the idea stupid. Dangerous pressure, plus the fact that some reactions leave behind residue (baking soda and vinegar leave a sloppy white paste that is annoying to dispose of, let alone remove from a tank).

Also, dry ice and water create pressures that could cause a FATAL or at least DEAFENING blast inside a tank. Plus, dry ice causes severe frostbite and is usually difficult or illegal for anyone under 18 to obtain.

Edited by SHADOW HUNTER ALPHA, 16 February 2007 - 05:42 PM.

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#7 Sanityjr

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Posted 16 February 2007 - 06:06 PM

When I read boltsniper's article on his website he noted that the pressure of the gas released would push the dart out long before it caught on fire or melt. Tons of info can be learned from him in the following passage.

Note: This is from his website

"PROPULSION

A variety of propellants were tried. Some of the more exotic ones were black powder, Bacardi 151, and a few other random combustibles. In reality the fuels used were aquanet hairspray and WD40. Through trial and error we found that a 50/50 mixture of WD40 and hairspray performed the best. I have no proof of this, but it is just the way it seemed.

Ignition was sometimes sketchy. Getting the right fuel air mixture depended on the pressurization initially and it was never exact or the same each time. through more trial and error a good protocol of time to fuel and pumps was come up with that gave quasi-reliable ignition.

Firing produced a healthy *whooomp* noise and about a 2 foot blue muzzle flash. Contrary to popular belief the dart receives no mal effects from the launch. It does not come out on fire. It does not get melted or burnt. In fact the dart doesn`t even get warm. It is not in contact with the flame long enough. "

Edited by Sanityjr, 16 February 2007 - 06:07 PM.

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#8 SHADOW HUNTER ALPHA

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Posted 16 February 2007 - 06:24 PM

Ignition was sometimes sketchy. Getting the right fuel air mixture depended on the pressurization initially and it was never exact or the same each time.


This is only adding to the reasons not to use a combustion gun. However, I will say that a properly working gun would be a nice trophy, such as sponge's cannons. However, such a gun would not be practical in the least.

Edited by SHADOW HUNTER ALPHA, 30 September 2007 - 01:38 PM.

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#9 six-five-two

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Posted 16 February 2007 - 08:34 PM

Just make a plunger or pump up homemade. Combustable stuff, like Uncle Hammer is very dangerous... And didn't some guy a little while ago made a combustable nerf gun and it took like 30 minutes between shots?
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#10 z80

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Posted 17 February 2007 - 09:52 AM

The only thing I could see chemical energy being useful is in an indirect firing weapon (IE bombs, grenades, mines) Due to reloding not really being a factor and time from ignition or reaction to firing wouldn't really matter. One thing I've been thinking about is a grenade with a burst disk on the top, that would have some gas releasing reaction inside.
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#11 Fireshot

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Posted 17 February 2007 - 03:39 PM

I know that I'm probably adding fuel to the fire with this idea, but when I read the potato gun post, and idea came into my head. What if one put a plunger tube with a plunger made of mostlikely a pvc endcap between the combustion chamber and the barrel, so the pressure and firey stuff would push the plunger, which would push air and shoot the projectile out. It would be a safer way to make a launcher that shot something like z80 suggested.

Edited by ‡Fireshot‡, 17 February 2007 - 03:40 PM.

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#12 Carbon

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Posted 17 February 2007 - 04:22 PM

I know that I'm probably adding fuel to the fire with this idea

So to speak.

What if one put a plunger tube with a plunger made of mostlikely a pvc endcap between the combustion chamber and the barrel, so the pressure and firey stuff would push the plunger, which would push air and shoot the projectile out.

You couldn't use just a single endcap, as you'd need to have some system to vent the excess pressure created from the explosion. However, a vent would put the pressure closer to you than the end of the gun. Bolt's gun shot flames two feet...I really wouldn't want that any closer to me.

There would be ways to create a vent system (an I-shaped plunger which would have the air side ahead of the vent hole is one), but such a design starts to get dangerous. The system might not vent all the extra pressure fast enough, which might cause the gun stress to the point where it would fail quickly...or explode outright.
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#13 Fireshot

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Posted 18 February 2007 - 07:18 PM

Just put some pvc for a vent at the top of the plunger stroke, then pipe it away from the shooter. Also, this hypothetical gun would be smaller than Bolt's, and use less petrol to power it, no reason to tear apart my hypothetical darts.

Edited by ‡Fireshot‡, 18 February 2007 - 07:19 PM.

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