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Bluewater Pneumatics - Pros and Limitations

Gazz

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Jun 22, 2005
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Hi Guys,

As some of you know i have owned many pneumos over the years. Right now in Sydney my weapon of choice is a "predathor vuoto 100", I can take out good fish from a distance and with the power reducer i can shoot stuff in caves. It is also easy to load and has been very reliable (except for the odd vacuum cuff).

In summer for the big kinges and pelagics, the Predathor Vuoto 130 (no power reducer, + 8mm spear, 1000pumps) Is king, I have shot 3 kingfish in one shot not long ago. The spear goes through everything and it can hang with 4 rubber koah guns, in terms of range and power. I intended to use it in the coral sea... but unfortunately that didn't eventuate.

Now a young dive buddy and Pneumatic enthusiast has been doing some crazy and impressive things.

I witnessed him use a predathor vuoto 115 (no power reducer) with 45BAR shoot a 8mm spear with 3 wraps... The spear shot like lightning then and bounced back about 2mtrs from the end of the shooting line. He had technical issues after that (some water got in the main barrel).

He is working on things and i know he wanted to push these guns to find out their max potential, but i wanted to know at what pressure will a gun like this rupture! What elements should he be considering with such forces, do you guys know of any other "Conventional" vacuum pneumatic guns (I am not thinking of hydropneumatics) modified for blue water?

Diving Gecko I know of your amazing 130 Mares Mirage, have you had issues with your piston letting water in at high pressures? Did you upgrade the parts for higher pressures?

Has anyone found the max limits on these weapons?

Anyone used a 9mm spear?

Thanks
 

Diving Gecko

shooter & shooter
Jun 24, 2008
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Great thread!

What I wanna know is how does he load that monster? A pulley loader like I made or an EazyLoader (Tomi design) or?

I have not had huge issues with my Mirage but it has not been over 33 bar I think. Also, at some point and def when I will start making my own reservoirs, I will do a burst test on one. I think perhaps your friend should consider sacrificing and blowing up some parts for peace of mind. Remember to fill them with water for such a test so the burst wont blow stuff around.

I think Salvi will say the parts are good for 30bar, but whether they operate with 2-3 times safety margin, I don't know. Imagine a gun like your friend's left out to bake on the boat and then someone drops something on it... I would think the reservoir is safer but I'd test the plastic parts.

Does he still use the stock shock absorber and piston? Cuz I know of at least one that died at just 25 bar.

Years ago some guy in the Med wrapped kevlar around the plastic parts and I think he might have run the guns at up to 60 bar after that. I may have a pic somewhere, I'll look later.
 
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Gazz

Gazz

Well-Known Member
Jun 22, 2005
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Yes he is still using the standard shock absorber and piston. Apparently they are now turned Delrin.

His loading method is clever, but he needs to get on here and share that with you. I remember seeing some carbon wrapped guns on medfish shooting 9mm spears at 65bar, they had winch loaders like tomics one.

The Kevlar wrapped speargun is on the russian hypropneutaic wesite, he used inox shock absorber.
 
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Diving Gecko

shooter & shooter
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Yes, it would indeed be nice if he got on here to share or allowed you to share. The exchange of experience, ideas and knowledge works best when it flows both ways...;-)

As for the stock parts, I’m away from my own parts now but I think the shock absorber was always turned Delrin but perhaps the piston was injected earlier. But what I think happens is that you start busting the o-rings of the shock absorber and they jam the whole absorber stuck - So on subsequent impacts, the absorber can’t move and the piston starts taking a beating and eventually either the absorber or the piston breaks. That’s what I saw when I serviced another spearo’s gun and as mentioned I think he ran it at 25bar. I also speculated that Salvi got the clearance wrong at the front so that the gap is too big which allows this to happen. Cuz it doesn’t happen on the original which is Dima’s muzzles and he also uses o-rings for the shock absorber. Now, I’m not entirely sure if this diagnosis as I haven’t measured the gap in the two muzzles and compared them. One day, I probably will.
But maybe Salvi has changed something so this doesn’t happen any longer... again, we would need to measure some older parts and compare them to newer ones.


Sent from my iPhone using Tapatalk
 
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popgun pete

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Jul 30, 2008
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The Mares "Sten" can be taken up to 40 bar as I have done it on an early model with metal piston and shock absorber, but was almost impossible to load unless you could stand on something. The gun could shoot three wraps of cord and gave a mighty jerk when you pulled the trigger, so two handed shooting was essential. A Greek guy, Panagis Aravantinos, heavily modified a "Competition Line Sten" which is the one referred to above. http://aquatech1.narod.ru/index1.html. However to load it the gun used a winch mounted on his boat. The modified gun could be used at very high pressure, but I doubt the burst pressure was ever calculated and he hoped for the best. Wrapping the tank emulated wire wrapped cylinders used in aircraft gas bottles in earlier days.

 
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popgun pete

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Jul 30, 2008
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A long time ago someone suggested pushing the inner barrel piston back in a pneumatic speargun using a water pump temporarily attached to the muzzle. The gun was built using all metal parts to take the pressure to be used which was a lot more than standard. The hydropump was attached to the muzzle and you pumped water into the inner barrel with a lever (for mechanical advantage) pushing the piston back until it latched on the mechanism hook, then you unhitched the pump and removed it from the muzzle. The risky part was inserting the spear into an already cocked gun! A good push would seat the spear tail in the piston nose, but if the sear lever got jerked the gun might shoot. This was a very dangerous idea and I don’t know if the project was pursued beyond the initial concept.

This concept is similar to the ultra high start pressure hydropneumatic guns, the difference is the latter push an annular piston in the tank forwards rather than an inner barrel piston backwards. The advantage of the hydropneumatic gun is the pump is built into the gun's trigger mechanism, which is based on a hydraulic locking chamber, and is permanently attached. Other types of hydropneumatic guns are not ultra high start pressure guns and are basically analogues of pneumatic guns with a release hook controlling a releasing valve rather than a piston, or they directly control the spear tail.

Another loading permutation is the idea patented by James Horlock whereby a hydropump built into the gun pushes an annular piston in the tank rearwards after the gun has already been muzzle loaded. The start pressure is the usual pneumatic gun pressure, but after pumping water into the tank the air in the gun is further compressed as the tank volume has been decreased. The drawback of this system is the gun's nose becomes heavy as the front end of the gun is full of water. After the shot you have to release the water via a valve so that the gun returns to normal start pressure.
Horlock.jpg
 
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popgun pete

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Jul 30, 2008
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Things can be simplified if you return to the classic pneumatic speargun layout with a mid-handle, long narrow front barrel and rear air tank. Mares made such a gun which is in a sense loaded from both ends, the spear goes down the muzzle as usual and water is pumped from the rear into the back of the tank. This arrangement is known as a surcompressor and was also used in some spring guns.
Mares-Superjet-A.1.jpg

Mares-Superjet-A.2.jpg

The above image shows the water pump handle pulled back, the holes in the tube stop the outer tube cover from being hydraulically locked.
The problem with guns that inject seawater is you needed to flush them out after the dive as water droplets left in the gun can cause corrosion if they are saltwater.
 
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popgun pete

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Jul 30, 2008
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One thing to remember is that plastic pistons and shock absorber anvils are a cost reduction measure. They replaced steel items which had been used from the beginning and had been introduced when there was a need to contain costs and make guns more user friendly as they largely eliminated inner barrel corrosion. However the corrosion problem was easily avoided if you rinsed your gun out in freshwater and put some oil drops into the muzzle.
 

Diving Gecko

shooter & shooter
Jun 24, 2008
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Welcome Chris.
Cool to have you here and great first post.
I totally agree on the untapped potential in reg to making airguns proper bluewater cannons.
So, far I’ve wanted to keep the “assisted loading” mechanism part of the gun but I’ve been away from my own machines for over a year so development has halted on that front. But will get back to it all at some point.
I did have a go at a pulley system and it works alright for me. Don’t know if I could get to 40bar and still keep the shaft from bananaing on me. I will probably tinker with it some more later on.

As for your pump, you are now using the normal pump as your hydro pump? Where do you store the pump on dives? Just in your belt?

After pumping the piston into the sear do you turn the gun upside down out of the water to get the water out?
But yeah, that would be the cheapest as you’d only need an adapter with a check valve and a modified, threaded front for the muzzle.

Good to hear the new Salvi pistons are better.

If you have easy access to pools and gear - which I don’t these days then there’s one test I’d love to see get done. It’s on my own list but might take a year before I get the chance to do it.
I’d love to see how much of an impact the power regulator has on performance even when it’s open vs. not being there at all. I’d prolly go one step further and 3D print dummy power regulator bulkheads with differently sized transfer ports to simulate the older standards of ø6 and ø7mm and then gradually increase up to 13-15mm. But it’s a lot of work for just one test... One thing the Predathor has going for it is even when keeping the bulkhead I think the transfer bore is bigger than on most other guns.

That’s all for now and welcome again!:)



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popgun pete

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Jul 30, 2008
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Good to see your set up using a hand pump on the muzzle. As I mentioned the idea has been around before, I encountered it on Spearboard when Iyadiver posted on it, a search may find it there as Spearboard records go back a long way. At the time the “Black Sea” auxiliary hydropump, hydropneumatic gun was already being tested and was designed to take on big Tuna. That concept had been used before for small guns which could only be loaded using the hydropump and had never been much more than a curiosity with the hydropump barrel built into the grip handle (in Ukraine and Russia).

The danger of muzzle loading a spear into an already charged to shoot pneumatic gun could be minimized if it did not use a rocker sear lever as most pneumatic spearguns do. That would require a cam lock trigger mechanism which is very common in band spearguns and can be locked out by a safety. Current pneumatic guns have a safety that only blocks the trigger which does not mean the sear lever is locked and under some circumstances the gun can still shoot. However there is still the possibility that the piston’ s mushroom tail might break off, in which case the gun can shoot without warning. When I was looking at high power pneumatic guns the emphasis was on safety and the advantage of the “Black Sea” type gun was you operated it from the rear end, the spear inserting and not charging the gun when the hydraulic locking system was left open. Dangers were the gun might shoot during hydropumping, although the shot would be throttled, and the gun exploding with 100 bar in it, or maybe even more.
 
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popgun pete

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Jul 30, 2008
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I searched Iyadiver's posts on Spearboard, but could not find it, so most likely it was here on Deeper Blue in the early 2000's. I found some posts where he refers to a "crazy pneumatic" and an inventor friend whom he refers to as "Mr. Pneumatic", so I think this is the person who proposed the pump on the muzzle of a pneumatic gun.

The above thread is where Iyadiver talks about the supergun, but I have yet to find the post where he actually said how the loading device worked, but it is on here somewhere.
 
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quakeos

Member
May 24, 2017
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Gazz and I have both noticed an increase in power removing our power regs - it makes sense to me that if there is a transfer point anywhere in the internals where the surface area is smaller than the surface area of the inner tube then it can cause choking. I definitely agree pool testing is invaluable and I have access to one through a friend but it's about 30ft which I think is way too small for testing large oleos... thanks for the warm welcome and the kind words for you all
 

popgun pete

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Jul 30, 2008
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Mares used to sell versions of their guns without the power regulator, from memory the “Medisten”, “Ministen” and the “Miniministen” could be had with the regulator block omitted and the selector gate blanked off in a separate handle molding. Other companies did the same for their models. Usually the smallest models never have a regulator option because their tanks are too short in the first place for the regulator to be useful, one exception being the Hang Fung “Aqua Gear” smallest gun because they never had a blanked off handle.

All the “Supersten” guns had regulator handles mainly to make use of “easy loading” as it was not always possible to load a very long gun in one movement, the biggest versions were 150 cm!
 

popgun pete

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Jul 30, 2008
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One way to compare band guns to pneumatic spearguns is that band guns are parallel loaded in that you can add band draws of the same force increment to achieve a larger cumulative force to drive the spear and pneumatic guns are series loaded where each increment is greater than the last and in a sense they are stacked on each other in an ascending order. The exception to this is the air transfer “Mirage” pumping barrel system where the force is descending as loading strokes gradually depressurize the barrel that the spear will be later inserted into by moving air molecules from it into the main tank, this being aided by the smaller diameter pumping barrel having a very high compression ratio (i.e. a very small dead space).
 

Diving Gecko

shooter & shooter
Jun 24, 2008
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@Gazz and @quakeos One thing that I really learned on my latest Indo trip in reg. to BW guns is that we have to almost turn our thinking of what size gun is required upside down. I mean, we have to start from the shaft and its mass. Now, let's for a minute forget that you are running monster pressures, as that might skew the requirements a whole lot.
But since @quakeos mentioned that he likes Salvi's mono, then lets start there. Once you start hunting doggies of a proper size, you want to get rid of mono fast. That means dyneema or cable. Some really, really good info on that type of rigging over on spearboard but I feel like there's a growing consensus on using the stiff Aussie dyneema often in 1.7mm or 1.9mm or the Catchall cable with the very thin PVC coating in about the same size. That rigging is more draggy than a thinner Euro style mono so will slow a shaft down fast. So, the shaft needs to have a certain mass to carry the heavier tackle and still be able to punch through a doggie. Shaft-wise the roller gun guys are really beefing it up these days and it's not uncommon to shoot 150-160cm x 9mm shafts.
Personally, since I am not yet running pressures in the 40s (bar) my thinking is that a 140-150cm shaft at 8.5-9mm ought to do well. With your super charged guns, you may be able to get by with a shorter shaft and still have plenty of energy in it.
I ran my gun at 33bar most of the time on the latest trip and shot a 145cm x 8mm shaft rigged with 1.7mm dyneema and I fel that was about the minimum pressure I would need to make that shaft and line come to life. One day, I had a tech issue and had to drop the pressure to perhaps 22bar and it was far from enough for that shaft.
I think once you start testing a lot more (and hopefully, me too) we will start reaching some firmer ideas on what pressures are needed for each thickness of shaft - much like Majd has these days in terms of how much you can power up each thickness of bandgun shaft before returns diminish.
I wouldn't be surprised if with +40 bar pressures we actually no longer need the longest guns. Imagine how nice it would be for traveling and deep diving to just have a 115-125ish oleo weighing not much more than 1.5kg when the rubber dudes are lugging around guns at 4-6kg with shafts 30-40cm longer...

I guess this was a whole lot of words to say "don't get in the pool with a BW gun shooting 1.4mm (?) mono". Take into account the much heavier tackle you need to land these fish and include it early on in your optimization and testing.

A few more thoughts off of the top of my head:
The Salvi handle is beefy, probably the best candidate for what you are trying to do. But it could still be modified with a dremel and some putty to get a much higher grip on it and get it more aligned with recoil forces. I would even consider cutting the trigger guard and bending it upwards to be able to grip much high on the handle. This was a mod I've wanted to do on my Predathor handle for a long time but other projects got in the way.

If you start taking pool tests seriously, I'd love to see some slow mo side footage of shaft flight. My thinking is that the only potential down side our oleos have is that the shaft has no "track". It's only supported at the extremes so on long guns, the shaft must be sagging in the middle. During the shot, does the shaft get straightened out by the muzzle or does it compress and bend more and keep oscillating in flight? Add if so, when does that start hurting precision, shaft speed and penetration?
 
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Gazz

Gazz

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Jun 22, 2005
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Interesting.. Has anyone tried using a Stainless steel piston? could these deform at high pressures?

I have some old nemrod oleos that have steel pistons ans shock absorbers.

I have 1000 pumps in the 130, i think this is 20BAR? This is fine to load, i am wondering what pressures i could handle loading (ie 25 BAR-30BAR) and how much more performance would be gained and the chances of gear failure. I remember reading on the old Asso 115 modded with tomba style kids and 7mm spear performance was topping out at 24BAR.

It would be good to figure out a universal performance test ie penetration of a standard object at certain distances allowing for difference thicknesses, in order to understand and measure these performance gains.

I am wondering what max pressures Tromic has used with his winch style loader?

How has the reliability been of the Mares mirage been at 33BAR Gecko?
 

quakeos

Member
May 24, 2017
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I really want these new turned salvimar pistons to work out, but if not I will look at machining some 304 stainless pistons. I think it is a fantastic material for the job Gazz, very corrosion resistant and also very ductile - its yield tensile strength is at 30000 psi whereas its ultimate is at 70000! Basically, I very much doubt you could ever crack one, it will just keep getting misshaped or dinged on a small scale... However, I would still machine the tail end out of concrete hard steel. I am also very much in favor of cresting some universal standards and parameters/tests for speargun performance, something I've discussed with a few brains in the industry and also had a lot of thinking on it of it myself... may have to leave a whole new post to just that.


And yes diving gecko I agree with your shooting line perspective, I've never shot these large fish but I commonly am rigging and sometimes testing my customer's guns to take down these fish so I do get a little foot in the door with what has and hasn't worked. I think a really important aspect of this is the huge deceptions that pneumatic spearguns are the master of. We forget even at 20 bar just how much stored energy these spearguns have and how skyrocket-high efficient they can be! The spearguns have such little recoil that it causes huge perspective issues with the power of the speargun - and only penetration testing can show this. The first time I used an airgun I mistook it for having no power because I was used to intense recoil setups, and this is also an experience customers have had as well, to then only release what it's actually doing. All my salvimar vuotos I use frequently have custom grips and the handle is very high relative to the spear being a centre shot pneumatic. Even though it's not too amazingly high on the handle itself.. the ratio is about as high as the best rubber gun grips. I like your thoughts on moving the trigger guard up, but with this said I'm not sure the hand can really go too much higher due to the rear valve inlet - my custom grips barely finish and just clear the rear valve inlet. At 18 ish bar on my 115 vuoto I've shown a trick to a few dive buddies where I have my hand completely off the handle and pull the trigger with my index finger, the speargun moves back about 100mm... it's extremely impressive. With a custom grip, the recoil is so minimal and so controlled that I wouldn't have any desire to change anything - even when the gun was around 45 bar I felt the very slightest increase in recoil which is very standard behavior of custom grips.

I also do have a theory that pneumatic spearguns are inherently much more accurate devices pushing the spear from its very back and due to the outstanding linearity of the system it greatly reduces non-linear shaft action like shaft oscillations and allows a much greater terminal velocity from a spear.

Here is a quoted section from my article:

A spear can only go so fast. Oh wait, let me rephrase that. A certain speargun can only throw a spear so fast before it pushes the shaft into nonlinear action (shaft whip). We must ask ourselves what causes shaft whips? My answer is it is when the gun acts on the spear in a nonlinear way as such the "moments" as they are called in engineering are deviating. This is why we use thicker shafts with longer spears and/or heavier rubber setups. Eg - 5 rubbers cannot be used successfully on a 7mm spear. This nonlinear action is caused by many things - The rubbers not being able to be perfectly in line with the spear both at the muzzle and bridle end is one cause of this, as well as not being able to push at the spear's true center.


The greatest offender appears to be heavy recoil rubber setups, where the user isn't able to control the gun so there is a significant amount of shift in any random direction when fired which totally ruins stable shaft flight hence inaccuracy and shaft whip. If we are able to push on a spear at truly zero degrees from its horizontal axis no humanly loadable speargun will be able to push the shaft into non-linear action. The problem is that it isn't really possible, The second we go a degree or two off the horizontal axis it goes from needing quite literally tons to deform to exponentially less. enclosed track spearguns are a band-aid fix for this, and we could but not successfully use 5 rubbers on a 7mm spear and theoretically it would not "whip", the issue with this is that it isn't fixing the actual problem at hand and huge amounts of friction will exist in the track when the spear is fired, reducing power as a tradeoff for stable shaft flight. A well-designed rubber speargun will not require an enclosed track.


With a pneumatic speargun, its projectile is pushed from its very back, from a circular geometry 'tang". A parameter I have come up with to describe this phenomena is "achievable shaft velocity". And from my testing, observations and testing/observations of others I can conclude that a much greater shaft velocity is obtainable from vacuum muzzle pneumatic spearguns to the point where a humanly loadable pneumatic speargun cannot push any standard size shaft into nonlinear action, due to the quasi-perfect linear power delivery and ultimate control over the weapon.
 
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