Pumping up pneumatic spearguns

[popgun pete]

Thanks Pete

I have been researching all previous threads regarding pneumatic spearguns. What a steep learning curve. In fact its almost becoming a technical obsession. I can see why once you start tinkering around with one you cant top. I have learnt so much between your threads and Tromich threads. If I could speak Italian or Spanish I wouldnt get any sleep looking at all those wonderfull web pages.

The truth is we here in Australia are so far behind in the practical uses of pneumatics, especially on the East Coast. Where I spear in the shallows for estuary fish the water is most times cloudy. The benefit of a shorter barrel to swing around is vital, especially if it has the power of a longer band gun. I can only imagine the power in those new Omer and Cressi guns.

After further looking into the problem I found that the hand pump seals are shot. I went to the local dive shop and pumped the gun there. It feels much better. I can really feel the power in it when trying to load. Hopefully I can test it out in the next few days.

Does anyone in Australia distribute/sell dry barrel kits? I have sent emails to various companies in Europe with no replies. In your opinion what is the best dry barrel kit for a Seac Sub Asso 90?

Once again thanks for the info.

As Foxfish says Tromic and his son are probably the best way to go for a vacuum barrel kit. In Australia pneumatic guns are not that popular and people often have adverse views about them based mainly on hearsay and misconceptions. Write to people who know what they are talking about rather than waste time elsewhere. You will need a spring stainless spear for the better shaft surface required for the seal in terms of long term durability, other shafts eventually pit with rust spots.

 

[Alphamic]

Thanks again gentlemen.

Your advice is very helpful. I will contact Tromic and see how I go.

Cheers

 

[popgun pete]

Thought that this may be useful if pushed back onto the front page as I recently received a query on the subject for an unknown model of pneumatic gun. It is an "Atlantis" and is of the classic layout with a long barrel, mid handle and cylindrical rear tank, but with no spear or pump not much can be ascertained from it except that it has imperial sized handle screws..

 

[Jenno1983]

Anyone know the best place to buy an adaptor to fit the rear of my gun so I can attach an electric pump?

 

[popgun pete]

I made the adaptor for using a portable 12 Volt air compressor out of the end of a pneumatic speargun hand pump, the part that fits directly into the rear inlet port of the gun. On the Mares guns this part screws off the end of the hand pump body tube or you can buy the ends separately. My old Mares guns use a "quarter twist and lock" bayonet fitting on the end of the hand pump, later ones simply screw in. The front end of this adaptor is a standard rubber tubeless tyre valve insert with the valve core removed, you need the threaded brass end for the air compressor's inflator attachment to clip over it like when you blow up a passenger vehicle or bicycle tyre. The two end pieces in my adaptor are joined by an old spark plug body using only the metal part, but you can make it out of anything tubular provided you have access to some machining facilities. Basically you need something to screw into the gun, you could cut the end off an old pump or use the whole pump body, but you need to block off the air breather hole in the pump if you do. The assembly has to be air-tight so pumped air transfers into the gun without external losses.

Most pneumatic guns come with a pumping table for the number of pump strokes from empty to reach a certain pressure in the gun expressed in Bar or Atm or kg/cm2. As the volumetric capacity of both the hand pump and the gun's internal air reservoir (including the volume of the inner barrel) dictate the pressure level achieved with a certain number of pump strokes there is no "universal" pumping table. My advice is pressurise the gun to the maximum and see if you can still load it. If not then bleed some air out carefully until you can. A good idea is to have the power regulator set to "low power" when doing this, it limits the air that can escape if you overdo it, only a momentary push on the valve stem lets more air out than you would think. After letting any air out flip the power regulator lever back to "full power" and then try the gun for loading effort again as this action allows air pressure in all parts of the gun to equalise.

As I took these photos for another thread I figured that I should add them here. The rubber valve stem blew out when the rubber perished after some years so I just chucked it in a box and forgot about it. This was made for the bayonet connection Mares spearguns as I have a number of them. Mares quit using this style as the dead space is larger than it needs be in the back of these guns and you require more strokes to compensate for air lost as you pull the pump handle back for the next stroke. Still able to hit 40 bar though, however the pump barrels get quite hot.

 

[popgun pete]

One thing I forget to mention when I wrote this thread is you need to periodically lubricate your hand pump. Without some lubrication the pump piston rubber seal or washer will wear out. Pull the pump handle back and put a few drops of oil down the pump bore. A few drops on the pump sliding rod will also help. The hand pumps are lubricated at the factory, but over time this oil evaporates. Oil used can be the same stuff as you use in the gun, usually SAE 10 grade such as motorcycle fork oil which is used for the front mounted shock absorbers or dampers.