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A042 - Titanium Spearfishing Spear Gun Lantan Underwater Dive Speargun

popgun pete

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Jul 30, 2008
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You can see the plug and rear bushing here where they are screwed together for storage, they both having the same screw threads. The plug male, the rear bushing female.
GIRS-TITAN PARTS.jpg
 

popgun pete

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Just assembled the gun in its medium length to take these photos. I left the speartip off as charged weapons on land are not a good look, although with no water inside hydropneumatic spearguns don't shoot. However if air escapes the air reservoir in a rare occurrence then the spear would certainly be blown out.

Alongside the gun is the smallest receiver which when used in combination with the medium gun creates the longest version. Spears are supplied for all three gun lengths while a second medium length shaft can be used as the pump rod to pre-pressurize the gun.

Ports in the muzzle nose cone are to allow the “O” ring sealed spear tail to be pushed into the muzzle and the plastic line slide fits in the muzzle bore to help centralise the shaft. The stainless steel inner barrel commences just rearwards of these ports.
GIRSTITAN GUN MEDIUM 1R.jpg

GIRSTITAN GUN MEDIUM 2R.jpg

GIRSTITAN GUN MEDIUM 3R.jpg
 
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popgun pete

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Just found this reference which commenced a week earlier than this thread.
 

popgun pete

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With the two receivers stacked together to form the longer gun and using the longest spear you can feel the shaft tail "O" ring catch slightly as it passes through the join at the junction of the two inner barrels as you push the spear with no water inside the gun. Now it occurs to me that the long "combi" version of the gun shoots from the rear "medium" receiver only as if you muzzle load the gun underwater then the loading effort will initially drive the annular pistons forward in both receivers until the spear tail passes that join. Then the forward "short" receiver will allow the water volume under pressure inside it to escape around the spear through that butt join at the junction of the inner barrels while the water being injected in the longer rear "medium" receiver will be trapped by the releasing valve action, which in this gun is also the trigger valve. This is most likely the reason for the operating manual stating that the pressure in the forward "short" receiver should be higher than that in the rear "medium" receiver. That way when you muzzle load the long "combi" gun the rear annular piston will be the one to move without budging the front annular piston and ideally before the hydrostatic pressure in the gun's inner barrel is sufficient to move it the spear tail will have already passed the join in the inner barrels. Note hydrostatic pressure in the gun while driving the spear is blocked by the spear tail seal from escaping until the spear tail exits the mouth of the inner barrel.

Just like the spears on the Aquatech hydropneumatic gun the spear tail seals work as one-way valves as the tail "O" ring can slide fore and aft to cover or expose a radial drilling that connects to a small central bore hole in the tail of the spear. Pull the spear forwards at any time during loading and water will be sucked past the tail seal to add more water into the gun which you then inject by further pushing on the shaft with your hand loader. Pressing on the shaft closes the one-way valve in the spear tail.
Combi gun charging.jpg
 
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popgun pete

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In order to clarify the last image I have added water and the spear being pressed into the gun. The rear handle is not shown, but screws onto the threaded boss on the right which is the rear pressure bulkhead for the “medium” length receiver. The axial “reels” which sit in front of the respective forward air pressure bulkheads also flood.
Combi gun charging wet.jpg
 
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Zahar

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How is the issue of pumping water remaining in the barrel in the transverse pockets resolved?
 

Zahar

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The discrepancy between the pressure equality in the two pneumatic accumulators can lead to an increased internal resistance to the movement of water in the well and a loss of efficiency!
 

popgun pete

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How is the issue of pumping water remaining in the barrel in the transverse pockets resolved?
After the shot all annular pistons are leaning on their respective rear pressure bulkheads, so the water will be eliminated from the receivers. The axial reels have revolving covers, so after a dive any water inside them will drain out though the various gaps. The plastic front line wrap hooks just slide into the slots in the covers when you are fitting the reel covers. These revolving titanium covers can be removed by unscrewing the plastic nose cone as the titanium reel body is part of the front pressure bulkhead and the nose cone is what retains the cover in place. The covers can be rotated to wind line on the “spools” as the line passes up through a vertical (effectively radial) hole in the plastic hooks. Personally I find the line wraps OK on the front and rear hooks, so don’t plan on using the reel functions. It really depends on the depth of the water you are hunting in and if your prey holes up on the bottom and you need to retreat to the surface before descending again to finish your victim off, then you need more line on the gun to reach to the bottom.
Combi gun discharged.jpg

And when wet.
Combi gun discharged wet.jpg
 
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Zahar

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The translator does not translate correctly! I didn’t mean pumping out water, but getting air out of the barrel and pockets before loading! Hydraulic systems need bleeding to remove air before operation!
 

popgun pete

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The discrepancy between the pressure equality in the two pneumatic accumulators can lead to an increased internal resistance to the movement of water in the well and a loss of efficiency!
Because any water injected into the front "Small" receiver in the “Combi” gun configuration is lost once the spear tail "O" ring passes the unsealed join in the two inner barrels this would mean that some of your loading effort is wasted, but this only applies to the initial spear insertion. Once the spear tail moves into the rear inner barrel you can push and pull the spear and inject more water into the gun. For example you could just use the last third of the inner barrel and three strokes would be equivalent to one full length inner barrel stroke because the spear tail valve allows more water in but does not let it out. When the “Combi” gun shoots the injected water can only go out the inner barrel mouth as bar the inner barrel the connection between the two receivers is sealed.
 
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popgun pete

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The translator does not translate correctly! I didn’t mean pumping out water, but getting air out of the barrel and pockets before loading! Hydraulic systems need bleeding to remove air before operation!
If you hold the gun vertical with the muzzle pointing upwards while underwater then the inner barrel of the gun will fill with water before you insert the spear. A low power shot with only a partial spear insertion should get any remaining air bubbles out, or even a "dummy" shot with the spear pulled out. On the “Aquatech” guns you can open the rear hydraulic locking chamber and by pressing the shaft into the gun this will send water straight out the other end of the gun, thus getting rid of any air bubbles, however on these mechanical release valve operated guns there is no rear water exit. The rear handle is easy to screw off, so you could assemble the rear of the gun underwater as the releasing valve tail is first trapped in the handle and then you screw it onto the gun which pushes the releasing valve into the back of the inner barrel. Even a partial undoing of the rear handle may do the trick, but I have not tried it.
 
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popgun pete

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The releasing valve consists of a stainless steel body with a rubber cuff that slides and is biased by a coil spring to be clamped over the rear end of the inner barrel. When you inject water into the gun via muzzle loading with the "O" ring on the spear tail driving water rearwards the pressure created pushes the rubber cuff back on its stainless steel body allowing water to enter the annular volume of the receiver. This water in turn drives the annular piston forwards in the gun against the compressed air pressure inside the outer tank tube trying to push it back. As soon as you stop pushing on the spear the rubber cuff moves back to plug off the inner barrel trapping the water already injected in the receiver.
Releasing valve action.jpg
 
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popgun pete

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This is the "Small" version of the gun using the shorter of the two titanium receivers. The safety lever’s pivot pin can be seen poking out on the right hand side of the grip which means that any shots taken will be at full power, but if you want to convert to a low power shot pressing this pivot pin inwards shifts to another cam on the pivot pin that limits the rearward travel of the releasing valve. Thus by restricting the unplugging of the inner barrel at the rear end to a smaller opening gap this then throttles the shot. The safety control lever on the left hand side of the grip points rearwards for "shoot" and flips upwards to put the safety on and block the trigger. After the shot the trigger mechanism is reset by pulling the line release finger on the top of the gun backwards from its forward position when it lets the shooting line wraps escape. Synchronisation of the gun shooting and the line release lever activating is ensured by the trigger's upper section simultaneously blocking both the tail of the releasing valve and the innermost end of the line release lever which can be seen on the earlier layout diagrams.
GIRSTITAN GUN SMALL R.jpg

Another photo shows the axial reel section on the gun’s nose with its revolving outer cover removed. Revolving the cover winds line on the spindle section with the line being anchored in the annular recess directly in front of the spindle and passing out through the hole drilled in the plastic combined front line wrap hook and aiming sight. The line running through this hole is to prevent the line cutting on metal edges in the reel cover slot where the line wrap hook is mounted.
GIRSTITAN GUN LHS GRIP DETAIL R.jpg

A photo showing details of the reel spindle and the annular recess that provides the line anchor, it has some notches cut in the flanges to pass the line through.
GIRSTITAN GUN AXIAL REEL.jpg
reel details.jpg
 
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popgun pete

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This is how the gun shoots as compressed air drives the annular piston rearwards as a result of the releasing valve uncorking the rear of the inner barrel thus allowing water under pressure to escape down it. Because water is incompressible the water has to speed up as it moves into the smaller diameter inner barrel which means it travels much faster than the annular piston does and therefore can propel the spear at high velocity.
Releasing valve shot.jpg
 
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tromic

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This is how the gun shoots as compressed air drives the annular piston rearwards as a result of the releasing valve uncorking the rear of the inner barrel thus allowing water under pressure to escape down it. Because water is incompressible the water has to speed up as it moves into the smaller diameter inner barrel which means it travels much faster than the annular piston does and therefore can propel the spear at high velocity.
View attachment 57456

Pete can you explain how the valve is released after pulling the trigger? In the pictures shown earlier, this is not seen well.
 

popgun pete

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Pete can you explain how the valve is released after pulling the trigger? In the pictures shown earlier, this is not seen well.
This is how it works, I have left out the safety cam in order to make the drawing easier as it has been spliced together from a couple of different diagrams. The trigger blocks the line release lever which in turn blocks the rear end of the releasing valve. This feature is what makes this gun different from most other guns of this type and is quite ingenious.
trigger action.jpg
The shooting line then pulls the line release lever forwards from the position shown above so that the line can easily escape from the tip of the lever. When you reset the releasing valve by pulling the line release lever backwards this presses on the releasing valve tail driving the valve body forwards to once more seal off the end of the inner barrel.
 

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tromic

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This is how it works, I have left out the safety cam in order to make the drawing easier as it has been spliced together from a couple of different diagrams. The trigger blocks the line release lever which in turn blocks the rear end of the releasing valve. This feature is what makes this gun different from most other guns of this type and is quite ingenious.
View attachment 57459 The shooting line then pulls the line release lever forwards from the position shown above so that the line can easily escape from the tip of the lever. When you reset the releasing valve by pulling the line release lever backwards this presses on the releasing valve tail driving the valve body forwards to once more seal off the end of the inner barrel.
Thanks Pete! Actually the safety cam makes me the difficulty to understand it clear because it seems to me that it prevents the adequate moving of trigger lever. Now from your drawing I can see that that moving is actually very small, just to slip from the line releasing lever bottom.
 

popgun pete

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In order to take a better look at the safety cam would require the trigger mechanism cassette to be removed. A slotted cheese head screw holds it in place and can be seen by looking inside the hollow grip handle through the open butt end. Exactly what type of threaded hole that screw fits into would determine whether it could be removed and replaced without causing some problems. The safety cam only rotates through 90 degrees between safe and fire; control lever upwards is “safe” and the lever pointing rearwards is “fire”.
GIRSTITAN GRIP LAYOUT.jpg

grip top mechanism cassette.jpg

In the above photo the safety is "on" with the tip of the control lever on the other side of the grip handle just visible in front of the line release lever. Note that pushing on the projecting metal pin on the right hand side of the grip causes the safety cam assembly to slide to the left so that the gun switches to a low power shot, but this can only be done with the safety lever set to off, or fire, and the trigger mechanism is already reset.
 
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popgun pete

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The releasing valve in the discharged position which is indicated by the line release finger being tipped forwards.
releasing valve in discharged position.jpg

When you screw the grip handle onto the gun body this is the position that the releasing valve should be in as it removes any loading from the cuff biasing spring and makes it much easier to screw the body connecting threads together without any tension or risk of cross-threading. Likewise when removing the rear handle a slight hydrostatic pressure through pushing a short column of water with the spear tail in the barrel while pulling the trigger will push the releasing valve right back enabling an absence of tension when unscrewing the big connecting threads. This also prevents rotating the rear inner barrel mouth against the sealing edge of the rubber cuff, it may cause no harm if you do but for an extended life of the cuff it is best to not subject it to unnecessary friction, especially if the gun is no longer wet inside.
 
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