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Pneumatic speargun without piston

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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tromic

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Aug 13, 2007
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This is an idea of a Vlanikgun like speargun design. His design was the first I've seen. Maybe there are other similar designs too. Here is a slightly different solutions to Vladimirs design. Just to put something new on a forum. :) I suppose it might work, at least theoretically on a paper! The shaft is 9 mm with thinner front segment of 8 mm. I do not like this 8 mm part but I had not better solution. The most critical part of the design is reliable permanent sealing on the rear part of the shaft.



 

popgun pete

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Jul 30, 2008
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Unless the red seal (if that is what it is) in the spear tail can bow inwards then hydraulic lock will stop the spear tail cap fully engaging when inserting the shaft into the gun while submerged. If you remember I suggested some easily compressed foam rubber like material that may allow the trapped water to be accomodated somewhere. Hydraulic lock will stop the front lip of the tail cap fully cupping the "O" ring in the groove in the shaft tail. The water inside the tail cap flows out until the "O" ring makes contact, then it stops and that remaining water prevents the tail cap moving completely forwards on the shaft (refer attached diagram).
 

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tromic

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Aug 13, 2007
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Unless the red seal (if that is what it is) in the spear tail can bow inwards then hydraulic lock will stop the spear tail cap fully engaging when inserting the shaft into the gun while submerged. If you remember I suggested some easily compressed foam rubber like material that may allow the trapped water to be accomodated somewhere. Hydraulic lock will stop the front lip of the tail cap fully cupping the "O" ring in the groove in the shaft tail. The water inside the tail cap flows out until the "O" ring makes contact, then it stops and that remaining water prevents the tail cap moving completely forwards on the shaft (refer attached diagram).

Vertical "red strip" (right from the O-ring) is supposed not to block the water flaw. It is just additional element to ensure some friction. The proposed design should work without that "red strip". Only an air bubble is required inside shaft tail boring. Before loading the gun the shaft must be held out of water vertically and than pushed into the gun muzzle retaining air bubble in shaft tail.
 

popgun pete

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Jul 30, 2008
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Vertical "red strip" (right from the O-ring) is supposed not to block the water flaw. It is just additional element to ensure some friction. The proposed design should work without that "red strip". Only an air bubble is required inside shaft tail boring. Before loading the gun the shaft must be held out of water vertically and than pushed into the gun muzzle retaining air bubble in shaft tail.

Yes, it will work with the gun loaded while out of the water, but that is usually inconvenient unless the conditions are right and you can lift the gun clear.
 

tromic

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Aug 13, 2007
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Yes, it will work with the gun loaded while out of the water, but that is usually inconvenient unless the conditions are right and you can lift the gun clear.

Actually the gun could be loaded in water. Just the shaft should be taken out of water to catch some air in a shaft tail boring. After catching some air and attaching the shaft to the gun, loading could be as usual, in any position. But with some modifications to the design, the loading could be done entirely in water. That would require the design to be a more complex. I do not like complex designs!
 

popgun pete

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Jul 30, 2008
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Here is an idea to provide somewhere for the water in the tail cap to go and prevent hydraulic lock. If the spear shaft is a hollow tube it can then have a valve built into the rear end of it, like a pneumatic gun's inlet valve, but with a stronger biasing spring. The front of the hollow spear is sealed off with a female thread accepting the male thread of the spear tip, such as the type of tip used in the old spring gun spears which were also tubular. A rubber gasket is used here at the front end to seal the spear interior once the spear tip is screwed in. The concept is that when loading the gun the excess water trapped in the tail cap is pushed through the valve into the interior of the spear each time. Each successive shot will add more water to the spear, but the quantity transferred will be small. At the end of the hunting session (or each day) the spear tip is removed by unscrewing it and the water emptied out of the spear ready for next time. To prevent corrosion the spear is washed and stored with everything opened up so that it can fully dry out internally between dive trips. The spring in the spear tail valve, a ball type valve, must be strong enough to resist ambient pressure at depth flooding the bare ended spear after the shot, but weak enough so that the force of loading the gun causes it to open before the tail cap moves into the gun from its place in the muzzle where it acts as a plug. Then the air pressure in the gun should hold the tail cap firmly on the spear as for it to fall off it will need to create a slight vacuum, the tail cap also preventing air from the compressed air reservoir getting into the hollow interior of the spear. Thus the hollow spear gradually accumulates water, but not enough to change its mass if the usual number of shots per dive are say around twenty shots. The longer the hollow spear is then the more capacity it has to contain water, hence it would take a greater number of shots to fill it up, but the idea is to empty it out well before that happens. If the hollow shaft half filled with water coming through the rear valve then the pressure inside the spear would double to 1 atm. (gauge pressure) having been at ambient pressure initially (i.e. gauge pressure = zero).
 

tromic

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Aug 13, 2007
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Yes, Peter that might be a solution. An another simple solution might be to put a neoprene "stick" into the boring. That might work for some time. After some usage the used "soaked stick" could be changed to a new neoprene "stick".
 

popgun pete

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Jul 30, 2008
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The reason I suggested the ball valve is that one could be used which is taken from a trashed pneumatic speargun, particularly the Mares inlet valve which now uses a simple cylindrical spring instead of the original conical shaped coil spring. Tensioning up the spring will vary the pressure that the valve opens at.
 

tromic

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Aug 13, 2007
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The reason I suggested the ball valve is that one could be used which is taken from a trashed pneumatic speargun, particularly the Mares inlet valve which now uses a simple cylindrical spring instead of the original conical shaped coil spring. Tensioning up the spring will vary the pressure that the valve opens at.

Any idea is welcome! Although this drawing of the gun would remain just an idea too.
I will not make it, I suppose. But who knows... :friday
 

popgun pete

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Jul 30, 2008
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Any idea is welcome! Although this drawing of the gun would remain just an idea too.
I will not make it, I suppose. But who knows... :friday

Maybe Vlanik might try it, I think that he will probably read this thread. The differential pressure held tail cap idea has always been frustrated by hydraulic lock problems which will stop the tail cap getting to that pressure condition. Then it falls off inside the gun and adds that small amount of water as well to the air reservoir, but which will blow out with all the air when the gun shoots! A mechanical friction detent has been the only solution, up until now, for retaining the tail cap on the spear when the gun is cocked and ready to shoot.
 

tromic

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Aug 13, 2007
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Maybe Vlanik might try it, I think that he will probably read this thread. The differential pressure held tail cap idea has always been frustrated by hydraulic lock problems which will stop the tail cap getting to that pressure condition. Then it falls off inside the gun and adds that small amount of water as well to the air reservoir, but which will blow out with all the air when the gun shoots! A mechanical friction detent has been the only solution, up until now, for retaining the tail cap on the spear when the gun is cocked and ready to shoot.


Peter, there is actually something similar to my idea. Look at this link:
Garpun.spb.ru :: -
I understand almost nothing, using google translate. You will understand much better.
I suppose that was working but there were still some problems?
 

popgun pete

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Jul 30, 2008
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Peter, there is actually something similar to my idea. Look at this link:
Garpun.spb.ru :: -
I understand almost nothing, using google translate. You will understand much better.
I suppose that was working but there were still some problems?

I gather that this thread is a continuation of the one where someone proposed a piston-less and inner barrel-less gun, but never actually made it (128 pages to date). The idea shown here (by you, 14th post from top of the page) dumps the problematic trapped water outside the spear using an annular ring valve. I wonder how that ring valve will fare going through the muzzle seal a few times. Maybe you could put the hollow spear solution there for the Russian guys to read, I don't belong to that forum, but I see Hanter is there. http://garpun.spb.ru/forum/

The hollow or tubular spear (such spears were common in the fifties) requires only one valve and has plenty of internal accommodation for water, but the dive would be over before you filled the spear up to any extent. The spear diameter is the "inner barrel diameter" effectively, like the RPS-3 the volume displacement of the spear is used to push against highly compressed air inside the gun, so you need a fat spear, or very high pressure air in the gun if the spear diameter is small, say 7 mm OD or less. That is why the RPS-3 used a 9 mm OD spear, even then the air pressure in the gun was high (from 40 to 65 kg/cm2!).
 

tromic

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Aug 13, 2007
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Ok, Peter. Thanks! I thought you were the member of that forum. Ive already posted my idea there. Maybe somebody make use of it. As I told, there were similar ideas but the details might make a difference, to work or not.
Cheers, Tomislav
 

popgun pete

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Jul 30, 2008
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The pistonless speargun design has the highest efficiency, this has been discussed when Vlanik made his posts here some time ago, but of necessity it must use a forward latching spear which is a weaker design with the spear grooved for the muzzle mounted sear tooth to engage just behind the speartip. It is OK for smaller guns, but not so good for more powerful weapons where the spear may be accidently bent at that annular notch which weakens the shaft. The design can be improved by only having the notch at the bottom of the shaft, but then the spear must be inserted the right way up and not rotated as the spear is forced into the gun. That is not so easy to do as the tendency is to rotate the shaft on pneumatic spearguns during muzzle loading of the gun.
 
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popgun pete

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Here is another "pistonless" pneumatic speargun from Russia, the "AMATIKA", which has a trigger mechanism that utilizes a sear lever that does not have a pivot pin, instead the sear lever is a metal block that tilts inside a matching slot cut into the muzzle body to catch or release the spear shaft. A schematic is attached with a translation of the part names. An interesting feature is that you do not have to pull the trigger to load the gun, something which you usually have to do with forward latching spearguns like this one. Instead the sear tooth is held depressed by the detachable plug (12) on the tail end of the spear that stops the compressed air escaping from the muzzle after the shot. In the "AMATIKA" speargun this plug or stopper extends far enough forwards to trap the sear tooth and when you insert the spear to muzzle load the gun you push this plug off the sear tooth which can then reset while you push the spear fully back to cock the gun. More information can be obtained from the company web-site http://www.amatika.com/ which includes the relevant patents for the gun and an interesting downloadable calculator of speargun shooting performance.
Amatika schematic.jpg
 
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popgun pete

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Jul 30, 2008
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Here is the patent diagram showing the sear tooth operation. The plug or spear tail cap looks longer here than in the above schematic for the gun.
Amatika mech.jpg
 

Vlanik

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Jan 19, 2009
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The pistonless speargun design has the highest efficiency, this has been discussed when Vlanik made his posts here some time ago, but of necessity it must use a forward latching spear which is a weaker design with the spear grooved for the muzzle mounted sear tooth to engage just behind the speartip. It is OK for smaller guns, but not so good for more powerful weapons where the spear may be accidently bent at that annular notch which weakens the shaft. The design can be improved by only having the notch at the bottom of the shaft, but then the spear must be inserted the right way up and not rotated as the spear is forced into the gun. That is not so easy to do as the tendency is to rotate the shaft on pneumatic spearguns during muzzle loading of the gun.
Ешё ни один гарпун не сломался на моих ружьях...

Eshyo not a single harpoon conked on my handgun...
 
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