Sergiy Kravchenko (december 2005)
This article has been published in magazine "International Freediving and Spearfishing News" (№ 44, Jan/Mar 2006). www.diving-action.com
Increase of a pneumatic speargun power at the expense of reduce of internal losses.
In this article I want to tell about internal losses of a pneumatic speargun and as with these internal losses it is possible to struggle. The pneumatic speargun power directly depends on size of internal losses. Reducing internal losses of a speargun we achieve reduced of loading effort (at preservation of necessary speargun power) or we raise speargun power (at impossibility to increase loading effort).
Let's look at a principle of pneumatic speargun work. The pneumatic speargun consists of a barrel 2, tube 3 filled by compressed air, sliding piston 4 with rubber seal 5 and trigger mechanism 7.
At loading a speargun ( I ), we overcome force of compressed air action on the sliding piston 4 and force of rubber seal 5 friction on a speargun barrel 2. After the sliding piston 4 will be hooked with the trigger mechanism 7, the speargun will completely loading and be ready for a shot ( II ).
To a speargun fired ( III ), it is necessary to press the trigger mechanism 7 and by that to release the sliding piston 4. On a spear the force of compressed air transmitted through the sliding piston 4 will work but this force of pushing out of a spear will be counteracted by force of rubber seal 5 friction on a barrel 2; water mass between a barrel 2 and spear; water resistance, at an exit 1 from a barrel 2; compressed air resistance, at transition 6 from tube 3 in a barrel 2, and spear resistance. The speargun is in the unloaded condition ( IV ).
Now we see of main our "enemies":
· Friction of rubber seal 5 on a speargun barrel 2;
· Mass of water between a spear and a speargun barrel 2;
· Resistance of water, at an exit 1 from a speargun barrel 2;
· Resistance of the compressed air, at transition 6 from tube 3 in a speargun barrel 2.
Resistance of a spear we shall not mention, as the choice of a spear and the choice a spear tip depends from conditions of a underwater hunt.
The pneumatic speargun.
Let's begin in detail to form the requirements to the pneumatic speargun with lowest in the world by internal losses.
For reduction of rubber seal friction on a barrel, it is necessary to choose a speargun with the well polished and equal surface of a barrel, with minimal factor of barrel friction (for example stainless steel) and minimal barrel calibre (for example is better to use 11 mm calibre, than 13 mm). It is very important still to replace rubber "conic" seal of the piston with "0" ring rubber seal. On the piston there should be only one "0" ring rubber seal!
For reduction of water mass between a spear and a speargun barrel, it is necessary to choose a speargun with minimal calibre of a barrel (for example better than 11 mm calibre, than 13 mm), but one must also consider the spear shaft diameter.
For reduction of water resistance, at an exit from a speargun barrel, it is necessary to choose a speargun with the maximal diameter of the channel (i.e. muzzle bore's clearance on shaft and presence of any relief ports), at an exit from a barrel, or use a sealed muzzle outlet as in a pneumovacuum speargun.
In a pneumovacuum speargun there are no channels or relief ports at the exit from a barrel , but there is a special rubber seal 8, which interferes with receipt of water between a spear and a speargun barrel . The pneumovacuum design of a speargun eliminates at once two "enemies" - reduces almost up to zero any water mass between a spear and a speargun barrel, and accordingly water resistance disappears, at an exit from a speargun barrel (but adds some friction from the extra seal rubbing on the spear).
The pneumovacuum Mamba 90 speargun.
For reduction the internal compressed air flow resistance, at transition from tube in a speargun barrel, is necessary to choose a speargun without a power regulating. The power regulating has of necessity the channel with a small diameter. This channel strongly interferes with transition of compressed air from tube in a speargun barrel because it throttles the air flow.
The pneumatic speargun with a power regulating.
It is necessary to note, that the underwater hunters in an attempt to improve their pneumatic guns independently expand channels for an exit of water and for transition of compressed air from tube in a speargun barrel. In these cases it is necessary to be very cautious, as the unauthorised modifications "weaken" construction details and can result in explosion of a speargun and possible injury of the surrounding people! Unless one has a complete understanding of all the factors involved such changes are very dangerous.
For an estimation of size of internal losses of a pneumatic speargun such parameter as EFFICIENCY we will examine in the following testing program of various speargun models. The EFFICIENCY of a speargun is a relative measure of the kinetic energy of a flying spear, to the work expended during speargun loading. If we shall lower all internal losses of a speargun, we shall then raise resultant energy of a spear. The work spent by the underwater hunter at speargun loading, remain unchanged.
It is necessary to clear basic for the underwater hunter a question - on how many it is possible to increase of speargun power?
I report results of the measurements of speargun EFFICIENCY:
The speargun |
Mares Cyrano 700 |
Mares Cyrano 700 |
Sargan 600 |
Sargan 600 |
Zelinka 650 |
The speargun design |
The pneumatic |
The modified for pneumovacuum performance |
The pneumatic |
The modified for pneumovacuum performance |
The pneumatic |
The power regulating |
With a power regulating |
With a power regulating |
Without a power regulating |
Without a power regulating |
With a power regulating |
The barrel calibre, mm |
11 |
11 |
10 |
10 |
10 |
The barrel material |
The marine grade aluminium |
The marine grade aluminium |
The stainless steel |
The stainless steel |
The stainless steel |
The piston |
The piston with rubber "conic" seal |
The piston with rubber "conic" seal |
The piston with "0" ring rubber seal |
The piston with "0" ring rubber seal |
The piston with "0" ring rubber seal |
The spear diameter, mm |
7 |
7 |
8 |
8 |
8 |
The loading effort, kgf |
32-40 |
32-40 |
21,6-23,6 |
21,6-23,6 |
19,6-21,2 |
The spear speed, m/s |
27,8 |
30,3 |
23,5 |
24,5 |
22,6 |
The spear energy, Joules |
77 |
92 |
88 |
97 |
72 |
The speargun efficiency, % |
43 |
51 |
77 |
84 |
63 |
The pneumatic Sargan 600 speargun.
The pneumatic Zelinka 650 speargun.
For a hydropneumatic speargun does not exist restrictions of a spear speed, but this theme is worthy of separate article. In this article I shall bring the characteristics of the hydropneumatic speargun for comparison with the characteristics of a pneumatic speargun only.
The hydropneumatic Aquatech 500x9-B speargun.
The hydropneumatic Black Sea 500x9-B speargun.
The hydropneumatic Black Sea 500x9-A speargun with a butt.
The speargun |
Aquatech 500x9-B |
Aquatech 500x9-B |
Aquatech 500x9-B |
Black Sea 500x9-B |
The speargun design |
The hydropneumatic |
The hydropneumatic |
The hydropneumatic |
The hydropneumatic (This model of a speargun is loaded through the hydropump) |
The power regulating |
The power regulating |
The power regulating |
The power regulating |
The power regulating |
The barrel calibre, mm |
9 |
9 |
9 |
9 |
The barrel material |
The stainless steel |
The stainless steel |
The stainless steel |
The stainless steel |
The piston |
The piston with "0" ring rubber seal |
The piston with "0" ring rubber seal |
The piston with "0" ring rubber seal |
The piston with "0" ring rubber seal |
The spear diameter, mm |
8 |
8 |
8 |
8 |
The loading effort, kgf |
22,8-24,8 |
24,8-28,8 |
28,8-32,0 |
64-67 |
The spear speed, m/s |
22,9 |
24,9 |
27,0 |
45,8 |
The spear energy, Joules |
61 |
73 |
86 |
247 |
The speargun efficiency, % |
54 |
58 |
61 |
67 |
In the conclusion of article, I think, that for the readers it will be interesting to learn about EFFICIENCY of an "ancient" pneumatic speargun.
The РПО-2 speargun (a copy of the Nemrod Torpedero) is made in 1983 in Ukraine.
The РПБ-1 speargun is made in 1975 in Russia. I hunted with РПБ-1 speargun before creation of my hydropneumatic speargun.
The speargun |
РПО-2 |
РПО-2 |
РПО-2 |
РПБ-1 |
РПБ-1 |
The speargun design |
The pneumatic without the channel, at an exit of water from a barrel |
The pneumatic with the channel (i.e. additional relief ports) |
The modified for pneumovacuum performance |
The pneumatic |
The modified for pneumovacuum performance |
The power regulating |
Without a power regulating |
Without a power regulating |
Without a power regulating |
Without a power regulating |
Without a power regulating |
The barrel calibre, mm |
12 |
12 |
12 |
14 |
14 |
The barrel material |
The aluminium |
The aluminium |
The aluminium |
The aluminium |
The aluminium |
The piston |
The piston with "0" ring rubber seal |
The piston with "0" ring rubber seal |
The piston with "0" ring rubber seal |
The piston with "0" ring rubber seal |
The piston with "0" ring rubber seal |
The spear diameter, mm |
8 |
8 |
8 |
8 |
8 |
The loading effort, kgf |
12,8-24,8 |
16,4-29,6 |
12,8-24,8 |
19,2-26,4 |
19,2-26,4 |
The spear speed, m/s |
13,8 |
19,6 |
18,4 |
20,4 |
21,4 |
The spear energy, Joules |
23 |
47 |
42 |
51 |
57 |
The speargun efficiency, % |
30 |
49 |
53 |
52 |
58 |
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