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submersable speargun

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: joannaardway » Sun Aug 05, 2007 7:14 am

ProfessorAmadeus, a bigger problem is the mass of water in the barrel that has to be displaced (which takes a considerable amount of energy), rather than the pressure of the water.
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Unread postAuthor: rogntrude » Sun Aug 05, 2007 7:17 am

VERY COOL!@!!
I sey you is bery goood at whut you du. I weely wike it. How many spud points for not using speelcheck do i git?
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Unread postAuthor: iknowmy3tables » Sun Aug 05, 2007 3:03 pm

never mind my question I took a good look at the direction arows and setup, I never knew that guide rod guns are more like chammber sealing diaphrams well I already started my next gun
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Unread postAuthor: ProfessorAmadeus » Sun Aug 05, 2007 6:05 pm

Well if you, as said before put some type of water proof cover over the end (like he does) then you wont have to worry about shooting the spear and the water out.

Another thing that concerns me is the fact that the gun itself wants to float while under water. I know that its not going to be extremely difficult to aim and shoot but it might help to weigh it down. Then the recoil wont be so bad either (if it is).
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Unread postAuthor: homedepotpro » Mon Aug 06, 2007 1:41 pm

ProfessorAmadeus wrote:So say you take this under water to a consiterable depth like 30 feet. The air pressure will lose a fraction of its power and therefore need more air for the same amount of power it has at the surface. Now I am just guessing that this chamber will act the same as scuba equipment but I may be wrong.

Also if you are into scuba they make adapters that you can attach to your first stage regulator that is like a bike pump adapter for a compressor. I think they are only like 50 bucks. Then you can reload under water.

yeah i realized that. i only used it while free diving at depths of 15-20ft. and it function great. high barrel velocity but low range
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Unread postAuthor: Modderxtrordanare » Mon Aug 06, 2007 4:02 pm

ProfessorAmadeus wrote:Well if you, as said before put some type of water proof cover over the end (like he does) then you wont have to worry about shooting the spear and the water out.

Another thing that concerns me is the fact that the gun itself wants to float while under water. I know that its not going to be extremely difficult to aim and shoot but it might help to weigh it down. Then the recoil wont be so bad either (if it is).


Have you witnessed the stopping power of water?

When the spear goes from one medium to another (air to water) it will slow down considerably.

Edit: Grammar.
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Unread postAuthor: Tsukiten » Fri Oct 26, 2007 4:24 am

Just have a sealing in front of the barrel, so no water gets in.
If fired, the sealing breaks shooting all of the air in front of it, making the projectile (which comes out after that happened) not come in touch with water for the first few bits...

Just a theory :roll:
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Unread postAuthor: Novacastrian » Fri Oct 26, 2007 4:30 am

ProfessorAmadeus wrote:Well if you, as said before put some type of water proof cover over the end (like he does) then you wont have to worry about shooting the spear and the water out.

Another thing that concerns me is the fact that the gun itself wants to float while under water. I know that its not going to be extremely difficult to aim and shoot but it might help to weigh it down. Then the recoil wont be so bad either (if it is).


What like a "water proof cover" maybe?
How about reading first, posting later ?

P.S. Don't drag up old topics unless you have something important to add, it pisses me off.
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Unread postAuthor: Necrosis » Sat Oct 27, 2007 3:30 pm

*edit* I misunderstood. It was about getting high muzzle velocity but low range and the thing about putting the condom over the barrel.. well it's just a random pool of info now then eh..


Exactly, the condom over the barrel to keep the water out only helps the projectile accelerate for the time it's spending in the barrel.
once outside of the barrel the projectile will have to face the new viscosity of the material it is moving through.

Wich in turn will slow it down significantly. (It has to "break the water")

Now the best solution for that is to use a projectile that is longer than the barrel.

And the projectile should be a long thin rod that weighs as much as possible Now ideally you would make a barrel length sabot that has a really thin bar in it with a sharpened point. And the thin bar would extend beyond the barrel.

Sorry for the chaotic explenation so: Here's a maybe better version (atleast shorter)

You need a long heavy thn projectile.

Long to make it stable
thin so it cuts though the water easilly.
And heavy because of the it needs to contain.

So a thin steel rod that has been wadded enough to fit in the berrel would be ideal.









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