The advent of carbon fibre offers a solution to the problem in engineering a floating hydropneumatic, high pressure shooting speargun which until now has always seemed to be an impossible task. The firing valve operated guns all need an open rear end to the inner barrel tube which means that the outer tank is always the structural element holding the gun together rather than the inner barrel.
The clue as to how it can be done is in the last version of the Alcedo “Hydra”, namely the “Hydra Sprint 62”. If we look at its internal construction, which is of a modular form, we can see that like the later Aquatech most of the “extra” weight in the gun is in the thick bulkheads. Now in all the guns to date these parts are cast or machined from aluminium alloy, but they could be replaced with carbon fibre elements with the gun re-engineered to suit this new material. The question with carbon fibre is can a screw thread cut into it take high axial loads? If it cannot then the screw threads need to be engineered out of it and the construction modified accordingly as that is why the forward section is not also marked as a carbon fibre replacement on the Alcedo Superlight diagram. The problem screw thread is indicated, otherwise all the carbon fibre elements are trapped between the two outer body circlip locations. We know that this circlip holding system is adequate as this mid-handle gun operated at 100 Bar and could shoot for prodigious distances underwater.
A better candidate for Superlight conversion is the Aquatech and if founder Sergiy Kravchenko was still contactable then I would be discussing this with him instead, however the concept is getting its first airing here as he seems to have vanished from the Internet as an active presence. The problem with the Aquatech is that it may not lend itself to a circlip end bulkhead holding system, in which case the large diameter screw threads will need to be retained. This can be done by using threaded metal bushes which are annular rings that trap the carbon fibre bulkheads in their centres. A example is shown on the Aquatech Superlight diagram. Another aspect that will need engineering revision is the elbow connection from the auxiliary hydropump to the gun’s locking chamber, if the locking chamber body is itself a carbon fibre element then a strong connection to it must be retained as during gun charging this component is exposed to maximum gun pressure, that pressure being 1,500 psi (approx. 100 Bar) or even more. With extra strokes of the hydropump lever the gun could be charged well above 100 Bar which would mean that the spear would be driven to “cavitation sheath” generating velocities, decoupling it for some flight distance from the hydrodynamic drag effects of water. The problem with doing this is the gun then operates in the region of rapidly diminishing returns as more and more gun power buys little further advances in performance and the gun structure may fail alarmingly if over-zealously pushed beyond its tested limits. As always follow the manufacturer’s operating instructions and, importantly, read them in the first place!
Due to the high pressure operation the cylindrical outer tank needs to be retained as a metal component, ideally titanium which has been used in the 35 mm tank diameter Aquatech guns. This metal tubing is the main structural element in the gun and must not fail or the gun will eliminate any bystanders as it comes apart in a very big way.
With these changes the releasing valve, servo operation (due to the trigger “pilot” valve) hydropneumatic guns would be floaters and probably the most powerful underwater weapons in the submarine arsenal, yet easily and safely loaded by anybody regardless of physical stature or strength, with the all important charging to shoot operation conducted from the rear end of the gun.
The clue as to how it can be done is in the last version of the Alcedo “Hydra”, namely the “Hydra Sprint 62”. If we look at its internal construction, which is of a modular form, we can see that like the later Aquatech most of the “extra” weight in the gun is in the thick bulkheads. Now in all the guns to date these parts are cast or machined from aluminium alloy, but they could be replaced with carbon fibre elements with the gun re-engineered to suit this new material. The question with carbon fibre is can a screw thread cut into it take high axial loads? If it cannot then the screw threads need to be engineered out of it and the construction modified accordingly as that is why the forward section is not also marked as a carbon fibre replacement on the Alcedo Superlight diagram. The problem screw thread is indicated, otherwise all the carbon fibre elements are trapped between the two outer body circlip locations. We know that this circlip holding system is adequate as this mid-handle gun operated at 100 Bar and could shoot for prodigious distances underwater.
A better candidate for Superlight conversion is the Aquatech and if founder Sergiy Kravchenko was still contactable then I would be discussing this with him instead, however the concept is getting its first airing here as he seems to have vanished from the Internet as an active presence. The problem with the Aquatech is that it may not lend itself to a circlip end bulkhead holding system, in which case the large diameter screw threads will need to be retained. This can be done by using threaded metal bushes which are annular rings that trap the carbon fibre bulkheads in their centres. A example is shown on the Aquatech Superlight diagram. Another aspect that will need engineering revision is the elbow connection from the auxiliary hydropump to the gun’s locking chamber, if the locking chamber body is itself a carbon fibre element then a strong connection to it must be retained as during gun charging this component is exposed to maximum gun pressure, that pressure being 1,500 psi (approx. 100 Bar) or even more. With extra strokes of the hydropump lever the gun could be charged well above 100 Bar which would mean that the spear would be driven to “cavitation sheath” generating velocities, decoupling it for some flight distance from the hydrodynamic drag effects of water. The problem with doing this is the gun then operates in the region of rapidly diminishing returns as more and more gun power buys little further advances in performance and the gun structure may fail alarmingly if over-zealously pushed beyond its tested limits. As always follow the manufacturer’s operating instructions and, importantly, read them in the first place!
Due to the high pressure operation the cylindrical outer tank needs to be retained as a metal component, ideally titanium which has been used in the 35 mm tank diameter Aquatech guns. This metal tubing is the main structural element in the gun and must not fail or the gun will eliminate any bystanders as it comes apart in a very big way.
With these changes the releasing valve, servo operation (due to the trigger “pilot” valve) hydropneumatic guns would be floaters and probably the most powerful underwater weapons in the submarine arsenal, yet easily and safely loaded by anybody regardless of physical stature or strength, with the all important charging to shoot operation conducted from the rear end of the gun.
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