Speargun Understanding

[Thorp]

Hey Folks,

My father got me a speargun for christmas - great gift. I'm real excited to go spear fishing. His gun is a russian gas gun and mine is a band gun. I tore it apart the first night. Very simple, elegant design. It's got me thinking about all these spear designs. I've done a bit of research but still haven't cracked the surface.

My understanding of spearguns thus far is that there are band guns and gas guns - both operate essentially using the same principle. The band or gas acts as a spring and stores energy when it is cocked. In both cases, the diver manually loads the gun, transferring energy to the system.

That leads me to wonder if their are guns that use the divers air supply or an auxiliary tank to operate the spear gun? Surely that has been thought of but if they exist, they don't seem to be popular. Is it a cost thing? Safety? Some other aspect of this sport that I don't understand?

I've also seen mention of pneumatic guns and hydropneumatic guns. I presume the difference being the fluid acting on the piston or spear?

I'm looking for a good source of understanding all the working principles of spearguns. Animations and cutaway fews would be terrific

Thanks,
Adam

 

[tromic]

Look at this site:
Fishgun - Ãëàâíàÿ

 

[foxfish]

Hi Adam, welcome to db.
You can find huge amounts of info here on db but basically there are are only two types of popular speargun used by free diving spear fishermen.
Band guns are the most universally accepted as the weapon of choice!
Air guns (pneumatic) come second & as as you point out they both rely on manual effort to load.
There are other forms of guns available that do not require the same sort human force to load but generally these guns are not excepted as the normal!
Co2, Gunpowder cartridge,Compressed air cylinder have all been built but many would consider these types of gun totally unsporting as most of us are free diving spearfishermen!
There is some video somewhere on the site of a Russian fully automatic underwater firearm being used!!
However there is still plenty of room for speargun development especially in the air gun department.

 

[Thorp]

I see. I work in the paintball industry and see the same sort of antics - the majority of the gear is made with the "pros" in mind and recreational players follow suit. Reasonings might be different but the outcome remains.

Okay. So guns that use a supply reservoir are looked down upon because of the sporting aspect. Are there performance gains shooting a gun running off a reservoir besides the obvious ease of load? More directly, if a reservoir gun could be made to use a theoretical bike bump instead of a reservoir, could that be a significant advantage?

The hydropnuematic guns are really cool - my understanding is that they use water as they would oil in hydraulics, to increase the force on the spear. Do they make hydropnumetic guns that use a fixed volume of air or a supply reservoir or both?

And If I could get some numbers to start thinking about that'd be great. What's the average mass of a spear and exit velocity at the muzzle?

Thanks Again

 

[foxfish]

You can have a look though these pages Pneumatic Spearguns

 

[Old Man Dave]

You are talking about what many call a lost air system. Such devises for propelling a spear are banned in spearo competitions, banned for their use if claiming a record and in many countries classed as a firearm. Not so bad in your country but in most of the rest of the world that would be a major problem. Lost air (gas) systems like paintball and soft air weapons are exempt due to their low power.

You could produce a high power speargun using the lost air system but too much power can be a disadvantage. long range is not useful unless you have good vis. In the UK many spearo's are forced to use short low power guns just so they can see the end of the spear and so they don't shoot another spearo as the spear disappears off into the gloom.

Despite what I've said you could design a short, high powered, lost air gun with variable power and it might make an excellent gun even if potentially lethal in the wrong hands. In countries where scuba spearing is not banned the use of the scuba tank would make this even easier. One of the problems with lost air systems is once you've fired "X" shots until it's empty and you can no longer use it until it's recharged, although with scuba tanks this would be a lot of shots.

A self contained gun could use a small buddy bottle of the type used in some stabs and ABLJ's which works on the same pressure as the mian tank and can be refilled from it. I doubt CO2 would be much use as although it has been used in spearguns as a lost gas propellant it generally doesn't have enough grunt. Fine for paintballs but not a big stainless spear.

The main problem is as has been said a lack of acceptance bu most spearo's. For the tiny number of commercial spearo's, especially the deep scuba boys, a lost air "cannon" would probably be a great tool.

With regard spear weights, speeds and other impirical data there is some but to be honest spearguns work on the borderline of function and very small changes create large effect. Therefore most speargun design, alteration and tuning is very hands on. It's extremely difficult to theorise a good speargun design. R&D is al about testing prototypes and refining them.

Interesting thread this so give it a go and if you survive tell us about it.

Dave.

 

[popgun pete]

Explosive firearm cartridge spearguns culminated in the SMG from Tapmatic Corporation, but you are limited by the number of cartridges that you can carry (without dropping them as you fumble to chamber another reload). Ditto for the carbon dioxide cartridge spearguns, they use all the carbon dioxide gas from the small bulb cartridge for each shot, however some managed to squeeze three shots per charge out of a relatively small cartridge (e.g. the Crosman "Rocket Spear Sea Gun").

Carbon dioxide gives about 900 psi shooting pressure as the liquid carbon dioxide transforms into a gas. The guns are very powerful and are dangerous in the wrong hands. They were eventually banned as commercial spearfishermen shot up large numbers of Groupers and Cods with them, e.g. the giant fish lumber up to investigate the glassy eyed intruders in their territory and then they get skewered. A shot of gas from the gun into their guts and up they go like a balloon to the surface, although the battle was usually more protracted than this simplistic description. Over zealous use of the guns got them banned nearly everywhere but the USA. A more or less revamped "Pelletier" (a past big name in carbon dioxide spearguns) is being sold today as the "Maco" speargun, they were exhibited at DEMA in the USA.

The hydropneumatic speargun is a pneumatic with water acting as a transmission element between the moving bulkhead or piston fronting the high pressure air reservoir and the tail end of the spear. The Ukrainian "Aquatech" is the most developed of the modern hydropneumatic spearguns, in fact it is one of the few available to spearfishermen in the West. The hydraulic trigger mechanism in this gun works like a one-way valve during cocking so that the gun can be loaded in stages. This stage loading has been used to cock guns with very high internal air pressure using an auxiliary hydropump. That is where the power comes from, the super strong "air spring", not the use of water in the guns.

Rather than everything being rewritten out again about various speargun types check the threads here as foxfish suggests. Use the "Search" function. Nearly every type of pneumatic speargun has been covered, most types were fully developed by the end of the sixties, after that it became incremental refinements and improved materials for underwater use which lowered the overall weight of the guns.

A US company made a speargun powered using a scuba tank LP hose, it was not a long-term success.

 

[popgun pete]

That scuba tank powered speargun was the Ferro "Scubagun". The gun was available from Ferro Firearms at 38 Ridgeway Drive, Warren, Rhode Island. That was also the address of the inventor, Daniel Ferro. A US patent was filed on 17 June 1986 and published on 28 April 1987; the gun was advertised for sale with the patent still pending.
It is an expellable gas speargun using the scuba diver's air supply by taking a tap off the low pressure side of the regulator's first stage. The gun was supplied with a 50 inch L.P. hose with a quick release air coupling on the gun. I can only remember seeing one in a US Skin Diver magazine advert and then heard nothing more about them. Spearfishing was in the bad books at about that time with many manufacturers deserting the sport and concentrating instead on their scuba customers.

The "Scubagun" was about 30 inches in length and had a claimed range of 15 feet. Probably a collector's item today, if unused and still in its packing box!

 

[Old Man Dave]

In the original film "Thunderball" the underwater fight scene had divers armed with spearguns. They used Technisub Jaguars. These were pneumatics featuring a disctinctive mid handle with a large resevoir behind and a thin barrel ahead of the trigger. James Bond however had twin scuba tanks with an electric scooter on top of them (back mounted) and he had gun barrels alongside the tanks that appeared to fire spears powered by the air in his tanks. All make believe I'm sure but fun to watch.

I've used a technisub Jaguar but never actually fired a CO2 gun. I believed they were somewhat underpowered, well the ones I knew of anyway. They used the soda syphon (sparklet) refil cartridges. However, I am more than prepared to bow to Petes superior knowledge in this area and accept that there were high powered versions. I wonder how they got on with the temperature problems with CO2. As CO2 is stored as a liquid and evapourates to create a gas it is seriously effected by its ambient temperature. This can lead to variations in the pressure created and certainly in CO2 air rifles leads to inaccurate or inconsistant performance.

Dave.

 

[popgun pete]

Ben Cropp, veteran Australian diver, reported a friend took some fingers off when he carelessly held the shooting line of a carbon dioxide speargun! It is cited in his "Handbook for Skin Divers"; from memory I think the diver concerned was Ron Cox.

 

[popgun pete]

I thought I better add something about why the large carbon dioxide spearguns are such powerful weapons. These guns usually have a big cylindrical pressure tank down the back end and a skinny forward barrel with a mid-handle grip layout for balance. The rear tank is filled with liquid carbon dioxide and you get a constant pressure in the gun as the liquid progressively transforms into carbon dioxide gas. The liquid-to-gas process is affected by temperature, but the big alloy tank has large thermal mass and is warmed by the surrounding seawater. The pressure available for shooting only falls once all the liquid carbon dioxide is turned into gas (a liquid to gas phase transition). Long barrels allow the gas to reach maximum pressure before the spear is blown clear of the muzzle, it has about 890 psi behind it, well above anything a pneumatic will put out as spear loading of the latter would need a winch (which also has been tried, but reloading is slow!) at that pressure level.

On land, where they should never be fired, carbon dioxide guns have put shafts through tree trunks and car doors, even buildings and flown for several blocks of land in built-up areas! The police soon arrive after such exploits. The biggest models are very dangerous weapons and require disciplined handling. That is why they have been banned nearly everywhere. Reloading effort is zero and the guns use a metering system to minimise the wastage of gas. Early carbon dioxide spearguns were simple blow and go, as long as you squeezed the trigger the gas poured out, hence they were wasteful of gas.

High pressure expellable air guns lose shooting pressure with successive shots, unless they have some sort of pressure regulation like a scuba system does to maintain a steady discharge pressure into the firing chamber and barrel. This means extra weight, complexity and constructional expense, so carbon dioxide was the gas of choice, plus better than having a gun with maybe up to 3,000 psi stored in it on your boat!

 

[foxfish]

Where can I get one :t

 

[popgun pete]

You can buy a brand new "Maco", but will have only limited time to enjoy it as the authorities will soon be carting you off to prison once the trial is over and the gun has been seized if they are banned in your country. You can thank the irresponsible actions of some past users for this situation. Remember there are people out there who want to eliminate armed men tramping about their beaches, we are lucky to have the guns we use now. This is only because the sport is often thought of as a folly and its adherents will soon be eaten once their luck runs out. This is said with tongue in cheek, but there is a real need to act responsibly or spearfishing will be eliminated by political crusaders looking for dragons to slay. Need I say more?