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What vacuum muzzle guns are available off the shelf?

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.

X-Ring should be 14.8 mm x 2.62 mm (ID x CS). I suppose this modification would work but I must test it to be sure.
I had some other ideas too but this might be the best and the easiest to make.
I will update the Tomba thead if there would be some news regarding submerged loading..
 
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tromic said:
X-Ring should be 14.8 mm x 2.62 mm (ID x CS).
I will update the Tomba thead if there would be some news regarding submerged loading..
Click to expand...
I think if you can adjust your design a bit, you will have a much easier time finding x-rings. 14.8mm ID seems to be smack in the middle of two standard sizes:
13.95 x 2.62mm (ID x CS) and
15.54 x 2.62mm (ID x CS)
 
Diving Gecko said:
I think if you can adjust your design a bit, you will have a much easier time finding x-rings. 14.8mm ID seems to be smack in the middle of two standard sizes:
13.95 x 2.62mm (ID x CS) and
15.54 x 2.62mm (ID x CS)
Click to expand...

I might try with 15.54 x 2.62mm (ID x CS)...
 
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You could always use a blow-off ring on the Tomba, in fact this was discussed way back in the very beginning. A groove around the muzzle body with small holes radially running to the muzzle bore and when water is being pushed it blows out through the ring valve covering those small holes. Then as a vacuum develops the ring valve closes. Basically that is the design used by LG-Sub in the “Black Head”.
 
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Pete I think you are wrong about this statement: "Basically that is the design used by LG-Sub in the “Black Head”.
Black Head muzzle use X-Ring, instead of O-Ring as in former models. I do not know the details of design so I tried to find my solution using X-Ring too. It might be more simple that with O-Ring because does not require additional groove and small holes.

"Il sistema inoltre permette il caricamento
del fucile pneumatico direttamente in immersione
e consente la sostituzione in maniera rapida e
semplificata delle guarnizioni x-ring,
grazie al terminale ispezionabile!"

In English (Google translate):

"The system also allows uploading
of the pneumatic rifle directly under water
and allows replacement quickly and
simplified x-ring seals,
thanks to the inspectable terminal!"
 
You guys are both engineers and I am not so I am still confused as to how the x-rings makes a difference. I say that without knowing how the Black Head looks inside, but for many purposes, you can swap o-rings for x-rings and vice versa. So, I can't yet see how you can design this function to only work with an x-ring.
@tromic If you have an idea as to how it may work, could you sketch it out for us?
 
Well I described the “Black Head” system on this forum before LG-Sub had seemingly thought of it, just read the New LG thread. I bought the “Revolution” from the Pelengas Store guy who had only got it to examine it, and basically I did the same. As soon as I got my hands on it I figured that you had to tip the water out of it because it was in a way a refined Mamba. As the rear inlet valve cap was missing I wrote to LG and struck up a dialogue with them. I reflected on tipping the water out and simultaneously expressed the forward draining channel idea on the New LG gun thread. It is all there date stamped for those who care to read it. I then tried my best to find LG a better distributor here in Oz and continued my conversations with them. Plus like anyone else they could read my forum notes here. Then after a month or so the “Black Head” was announced.
 
Actually I can save you the trouble.
25 Jan 2019
If you watch the gun loading video carefully then you will see that the diver tips any water out of the muzzle before pushing the slider home in the muzzle, this being a “Mamba” type pneumovacuum system based on a sealed slider. Now personally I would rather not have to do that as for example I can muzzle load both my "Taimen" and "Pelengas Magnum" guns completely under the water, there is no need to tip anything out of the muzzle. What the LG-Sub gun needs is a muzzle relief valve like we discussed some years back to eliminate hydraulic lock, the valve consisting of a rubber annular band around the muzzle covering tiny ports with channels running back to openings behind the muzzle seal position. Hydraulic lock blows off the annular ring temporally before sealing again as a vacuum develops in the inner barrel during gun cocking.

The key words are channels running back as the LG "Revolution" muzzle and piston/shock absorber system cannot use radial ports as everything is much shorter in length. Unlike a Mares there is no relief port bridging section in the muzzle because the gun was never designed as a wet barrel gun.
 
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"X" rings are like two "O" rings side by side, so you have two inner and two outer sealing surfaces with no mold joins on the periphery as you have with an "O" ring. Instead the mold join is on the web connection of the two rings in a sort of Siamese arrangement. The big advantage is they don't twist in the seating grooves when you put them in, but the grooves need to be wide enough to take them if they were previously sized for "O" rings. If they were around when the "Mirage" was built then "X" rings would have been handy on the pumping barrel mounting endpoints in the gun.
 
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This is my schematic based on video presented by Claudio Basili, how it might look like inside muzzle.


The missing detail is what enable submerged loading using X-Ring. I think one X-Ring performs two tasks: maintain vacuum and enable water escape (in combination with water escape ports). It is easy to inspect and change even in water.
 

Davide, here it is how I think it might work with X-Ring:
 
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tromic said:
Davide, here it is how I think it might work with X-Ring:
View attachment 54657
Click to expand...

Thanks Tomi. I think I got it now. The x-ring would not move but the bore it sits in changes size in between the two lips of the x-ring?
I guess that's why - if you are making a version like this - you'd like to use a bigger cross section like 2.62mm to make it easier to get the positioning right?
 

Davide, thats are the missing details... I don't know how it is made behind the visible X-Ring front end.
My solution with Tomba would be quite different because I do not want to make big change to the existing design which is proven to be good.
My idea with 14.8 x 2.62 mm (ID x CS) X-Ring, with which I could just replace the existing 15 x 2.5 mm O-ring, was just to "shawe" one outer lip of the X-ring so it won't prevent water escaping from the gun. The other lip would maintain the vacuum.
 
You can see the "Black Head" muzzle in pieces here, this is shown on the New LG Gun thread, I have just snipped off the top image of the muzzle fully assembled.
 
If my calculation based on pixel numbers from images about LG speargun, the length of new slider is about 40 mm and its thinner back part is about
11 - 11.5 mm OD? The front end is thicker, maybe more than 12 mm OD.. I think this gun (the user of the gun) also might have loading problem if the shaft is bowed during loading..? That was also my major problem with first types of Tomba muzzle. Now with Tomba700X the loading is fluent and bowing forgivable but could not be loaded submerged, for now...

This is a image of X_Ring in LG muzzle:

 
My "Revolution" gun has two "X" rings in the muzzle which are spaced apart by about a centimeter, so the seal on the Delrin line slide/slider is at two locations. The use of two “X” rings is probably to stop any rocking of the line slide as it goes into the gun. Now you only need one vacuum seal, yet in a sense there are four as "X" rings are effectively double “O” ring seals. Conceptually the water is trapped in the muzzle as the leading seal edge takes up and the easiest solution is a short radial muzzle port or shallow internal annular groove between the "X" seals that leads to a ring of longitudinal outlet channels that send the water out the front end of the muzzle. As the line slide or slider moves past the first "X" seal it creates a pumping action that forces water out the ring of channels and then when it meets the second "X" seal it effectively closes those channels off and then as the gun is cocked a vacuum will form in the inner barrel.

The sketch is not a plan of the muzzle, it just shows the functional aspects and the detail will be slightly different. Once the spear tail can push on the piston the internal space opens up and you do not get a hydraulic lock.
 
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For this to work, I reckon the most rearward of the seals has to be very close to the piston. It must be as far back as physically possible otherwise, we are back where we started. And I guess there’ll still be a moment where there’s a bit of a hydraulic lock, just much smaller.
And if that’s how they made it, the front seal doesn’t even have to be there. The rocking of the slider could be stopped by having a small tolerance in the bore - so possibly they want the friction to stop the slider from falling out?


Sent from my iPhone using Tapatalk
 
I didn't know there were more variants of the LG vacuum muzzle...
Some rocking of the slider might prevent blocking of the shaft during loading..
What is the OD of the slider (back part) and the ID of the boring in muzzle?
 
Yes, the spear tail has to be touching the piston as the final seal closes onto the rear section of the line slide body. At that time there will not be a lot of water in front of the piston, unlike the situation if the seal was further forwards in the muzzle body. A similar situation to pushing the spear tail with a tail "O" ring into the muzzle of a hydropneumatic gun. No matter how hard you push the spear will not line up properly to push it into the gun, but if you pull the water valve trigger and let the spear tail enter a centimeter or so by releasing that water volume through the gun then the spear pushes in very easily until the opposing pressure builds up. In some ways the front "X" ring does nothing but act as a guide. The bore clearances are tighter than shown on my sketch which was just to show the juxtaposition of parts.

The vacuum in the inner barrel should suck the slider in when the gun is cocked. The original sliders seem to be made of metal, the later ones are of Delrin, although metal ones appear to be an option.
 
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tromic said:
I didn't know there were more variants of the LG vacuum muzzle...
Some rocking of the slider might prevent blocking of the shaft during loading..
What is the OD of the slider (back part) and the ID of the boring in muzzle?
Click to expand...
The rear slider body is 10.97 mm, very close to 11 mm in diameter. The muzzle bore is about the same size as inside it are the two "X" rings that seal on the slider body. The inner barrel ID is said to be 12 mm, therefore not a lot stops the piston. I have yet to remove the muzzle from my gun, the previous owner chewed the anodizing up trying to do just that, but I think the gun opens from the rear as they may have locked the muzzles on the barrel nose, it has been done before elsewhere. When the warm weather departed I gave up on dismantling it until the return of warmer conditions. Guns are easier to pull apart in hot weather as alloy parts expand.

The proportions are more like this sketch.
 
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