Having mentioned the all-reservoir-tank-and-no-inner-barrel "Vlanik" speargun in the recent speargun compression ratio thread, I thought that I would complete the list of pneumatic speargun types by describing another speargun which also has no inner barrel and in a sense no air pressure tank either. This is the vacuum speargun which is powered by a relative vacuum formed inside the gun body when the gun is muzzle loaded. The gun has a large diameter body tube (internal diameter is 40 mm) to provide the cross-sectional area necessary to obtain some useful propulsive force from the pressure differential acting on the sliding piston that will propel the spear from the gun.
The spear (8 mm diameter) inserts through a muzzle seal and drives a large diameter piston back (same size as the inner diameter of the body tube and carrying a single large diameter rubber cone type seal), pushing it away from the muzzle and moves it towards the rear end of the gun which is open to the surrounding water. Water sitting behind the piston is pushed out of the rear end of the gun while a relative vacuum forms in the space opening up between the piston's front face and the rear face of the muzzle bulkhead. That means the spear is sitting in a vacuum inside the gun body when the gun is cocked and ready to shoot, the gun body being in a sense one big barrel. You can think of it as a scaled-up "Mamba" system, but without the rest of the gun.
The problem with this intriguing design is the large contact area of the piston seal and the need to have a very smooth finish on the interior of the gun body/big diameter barrel, otherwise sliding friction will absorb too much of the gun's power. Especially as abrasive particles like sand and grit can easily enter the gun and damage the finish on the internal bore of the big diameter barrel. Any loss of vacuum inside the gun and the gun will lack any shooting power, plus water will fill the gun body if it has a bad leak when the gun is cocked. After shooting the gun has no buoyancy, being full of water. It needs to have some mass or it will float when cocked, which is not such a good idea! The spear has no stop diameter on its tail and is attached to the gun with an auto-coil type shooting line affixed behind the spear tip.
Basically a quirky gun that explores yet another variation on the differential pressure theme which is used to power all pneumatic spearguns, regardless of the type.
You can read about this very interesting gun on Apoxy.ru, a thread is posted there based on an article by L. Volkov from "Sportsmen - Submarine", issue number 69.
The spearfishermen of the former Soviet Union explored nearly every speargun design imaginable, no doubt something to keep them busy in the months while they waited for the ice on the local river or lake to melt!
The spear (8 mm diameter) inserts through a muzzle seal and drives a large diameter piston back (same size as the inner diameter of the body tube and carrying a single large diameter rubber cone type seal), pushing it away from the muzzle and moves it towards the rear end of the gun which is open to the surrounding water. Water sitting behind the piston is pushed out of the rear end of the gun while a relative vacuum forms in the space opening up between the piston's front face and the rear face of the muzzle bulkhead. That means the spear is sitting in a vacuum inside the gun body when the gun is cocked and ready to shoot, the gun body being in a sense one big barrel. You can think of it as a scaled-up "Mamba" system, but without the rest of the gun.
The problem with this intriguing design is the large contact area of the piston seal and the need to have a very smooth finish on the interior of the gun body/big diameter barrel, otherwise sliding friction will absorb too much of the gun's power. Especially as abrasive particles like sand and grit can easily enter the gun and damage the finish on the internal bore of the big diameter barrel. Any loss of vacuum inside the gun and the gun will lack any shooting power, plus water will fill the gun body if it has a bad leak when the gun is cocked. After shooting the gun has no buoyancy, being full of water. It needs to have some mass or it will float when cocked, which is not such a good idea! The spear has no stop diameter on its tail and is attached to the gun with an auto-coil type shooting line affixed behind the spear tip.
Basically a quirky gun that explores yet another variation on the differential pressure theme which is used to power all pneumatic spearguns, regardless of the type.
You can read about this very interesting gun on Apoxy.ru, a thread is posted there based on an article by L. Volkov from "Sportsmen - Submarine", issue number 69.
The spearfishermen of the former Soviet Union explored nearly every speargun design imaginable, no doubt something to keep them busy in the months while they waited for the ice on the local river or lake to melt!