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A042 - Titanium Spearfishing Spear Gun Lantan Underwater Dive Speargun
- Thread starterpopgun pete
- Start date
The above hydropneumatic gun is by Valentin. Below is a pneumatic version using the same stylistic principles. Not a mass production gun, unlike the Girstitan being discussed here. The pull rod running under the tank indicates a forward latching weapon. The garpun website had some info about him, but the site seems to have disappeared!
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The use of plastic to mount the trigger mechanism has reduced the potential for galvanic corrosion as the stainless steel releasing valve body does not actually touch the titanium of the receiver and its tail end only contacts the electrically isolated parts suspended in the rear grip.
Perhaps you could give these guns their own thread as not much point in showing them here.
An inner barrel diameter of 11 mm is relatively large for a hydropneumatic speargun, although in the early days of hydropneumatic guns such as the Alcedo "Hydra" inner barrel sizes were the then "standard" 13 mm diameter. They were also the days of 9 mm diameter spears and even larger for shooting enormous fish cowering in caves! Once shooting bans came into effect to save the dwindling stocks of these big fish in the more accessible locations that was the end for many of those big guns and spearfishermen also regained their senses. Eating a fish the size of a small car was not very appetizing!
Hydropneumatic guns have been described as temperamental and capricious when they can quit working for no apparent reason, but this is usually a result of poor maintenance. That includes after post-dive cleaning and rinsing if they are to be stored for a lengthy period then you dry them right out which usually means some disassembly. With this Girstitan gun being made of titanium it should be relatively impervious to marine use, but my advice is to always take such guns apart by at least pulling the releasing valve out. If nothing else it renders your gun useless if anyone decides to steal it as then they will not easily be able to replace that part which you keep separate from the rest of the gun.
With Aquatech guns no longer being made I think that this would be the only off-the-shelf hydropneumatic speargun available today if you exclude the forward latching guns such as the “Kobra”.
Hydropneumatic guns have been described as temperamental and capricious when they can quit working for no apparent reason, but this is usually a result of poor maintenance. That includes after post-dive cleaning and rinsing if they are to be stored for a lengthy period then you dry them right out which usually means some disassembly. With this Girstitan gun being made of titanium it should be relatively impervious to marine use, but my advice is to always take such guns apart by at least pulling the releasing valve out. If nothing else it renders your gun useless if anyone decides to steal it as then they will not easily be able to replace that part which you keep separate from the rest of the gun.
With Aquatech guns no longer being made I think that this would be the only off-the-shelf hydropneumatic speargun available today if you exclude the forward latching guns such as the “Kobra”.
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Pete, how is the sliding rubber cuff sealed to the releasing valve body? Has the biasing spring some role in that?
The hydrostatic pressure when the gun is charged forces the rubber cuff against the metal disc and its connecting cylindrical shank that forms the front of the releasing valve body. You could compare the rubber cuff to the sealing flange of a plug in a sink outlet, but here it seals a thin ring around the metal head of the plug and the rear face of the inner barrel. Because the annular gap created is small the hydrostatic pressure cannot force the rim of the rubber cuff through the gap. That gap has ambient pressure in the inner barrel on one side and charged to shoot pressure on the other side created by the annular piston transferring air pressure from the tank to the water trapped in the rear of the gun. The biasing spring helps to return the rubber cuff, but the hydrostatic pressure is what really seals it as any water flow is cut off before it can escape through that small gap.
Note for these releasing valves to work the diameter of the rear bore that the releasing valve's body "O" ring is located in is always larger than the bore of the inner barrel.
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Yes, I thought it was like what you explained.
It is similar in working principle to one of my early ideas presented on this forum some years ago, but this is for hydro pneumatic supergun and has more simpler design and is actually proved in exploitation. My remained just as an idea..
As someone recently asked me this is how the spear tail valve works. When you push the spear into the gun you want it to push water into the inner barrel, so the "O" ring on the spear tail slides forwards to create a tight seal. To push more water into the gun you then pull the spear forwards in the barrel and as it does so the spear tail valve opens with the "O" ring sliding rearwards. This opens the valve port cross drilling which the "O" ring was blocking and water around the front of the spear now sucks back through the open tail port to collect behind the spear tail. Thus with the spear nearly out of the gun another loading push rams even more water into the gun body. This raises the gun's shooting pressure, but also means it will shoot a column of water out behind the departing spear. This cumulative addition of water by barrel pumping is a feature of most valve operated hydropneumatic guns and allows another variation of shooting power in addition to any throttles.
The brass spear tail is most likely used to reduce any chance of scratching the inner barrel bore, but it is a good reason not to leave the spear inside the gun when not in use due to the possibility of corrosion with different metals in contact. My first Aquatech hydropneumatic gun had stainless steel valve tails, but after that they went to brass, probably due to cost.
The brass spear tail is most likely used to reduce any chance of scratching the inner barrel bore, but it is a good reason not to leave the spear inside the gun when not in use due to the possibility of corrosion with different metals in contact. My first Aquatech hydropneumatic gun had stainless steel valve tails, but after that they went to brass, probably due to cost.
The tapered shank design was used on the later Aquatech guns which had brass tails on their spears. The drilled port earlier tails are less likely for the "O" ring to be peeled off with the shaft skidding along the bottom, in fact they are difficult to slide by hand to open or shut.
One thing I noticed when cocking this gun is as soon as you stop pushing on the shaft it just stops, there is no slight rebound which you get with the Aquatech as its hydraulic locking valve slides back to plug the rear of the inner barrel. So the sprung loaded returning rubber cup on the GIRS-TITAN does not push much water when it does the same thing, which is not surprising as it is a thin rubber annulus. However a few times when I stopped pushing on the shaft it came straight out again and I noticed the line release lever was pointing straight up rather than lying back in the reset position. It looks like you need to be sure it is right back as otherwise the top of the trigger is not locking in behind the line release lever, so any developing pressure in the inner barrel is pushing the releasing valve body rearwards and there is no locking action and the spear comes out again. Possibly applying the safety may ensure the trigger is in the right position, but I haven't tried it. Rather than risk bending anything I would rather apply the safety after the gun is charged to shoot, then you know the trigger is in the correct position. I wouldn't trust the safety for anything other than line wrapping, the same as with any other speargun.
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