Testing the Salvimar Pneumatics

[tromic]

Pete, I think that the slider have the main centering role in Taimen spear gun. O-ring that holds the slider in place all the time until the shaft tail leave the muzzle helps that function of the slider. Without that O-ring slider might left the gun too early and there would be no centering in the most critical time.

In Tomba vacuum kit the only one O-ring on the shaft serves for maintaining vacuum and for holding in place the cone ring for centering the shaft. The shaft is in center with tolerances +-0.05 mm, all the time during shooting. I suppose similar tolerances are in case of Taimen too. With salvimar kit that tolerances might be +- 1 mm (or maybe +- 0.5 mm in best case)?

 

[popgun pete]

Well the "Tomba" never passes the shaft's stop diameter through its vacuum seal, but the vacuum muzzle guns that use the "hat" type seals do and it is not for nothing that the pioneering "Taimen" design focussed on this co-axial alignment aspect for the muzzle's vacuum cuff (or seal) and the inner bore of the gun barrel and the control of the shaft as it passed through them during the shot. If anything defines the "Taimen" gun it is the attention to precision in the manufacture of its metal parts that enables the control of these factors. The subject is also discussed here http://forums.deeperblue.com/threads/taimen-russian-pneumovacuum-speargun.82933/page-11.

 

[istriker22]

Unfortunately, I don't have good news on this gun either. Gun is shooting poorly, 3 out of 5 shots are in slow motion, shaft barely leaves the gun, and that's on high power.
When it does shoot normal, it's very powerful. So it's not lack of air. I don't know what's going on.


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[popgun pete]

I would say water is entering the inner barrel on those poor performance shots. If the shaft is slightly inclined then it may cause a leak during muzzle loading, but the seal in the muzzle should be more tolerant of that happening, within limits of course.

 

[istriker22]

I would say water is entering the inner barrel on those poor performance shots. If the shaft is slightly inclined then it may cause a leak during muzzle loading, but the seal in the muzzle should be more tolerant of that happening, within limits of course.

I thought about that, however the shaft has been pretty much straight when loading, this gun is fairly easy to load, it's not the case that too much force is needed to load it. Even if water were getting into the barrel, shouldn't the shaft be propelled at higher speed than what it is now? I have literally "pushed" fish within 10 feet of the tip of the shaft. That's how slow the shaft is being propelled.

 

[popgun pete]

The power regulator in those guns uses an upstream valve, so with the regulator knob pushed forwards it moves a plate off and away from the air transfer port in the partitioning bulkhead. The plate should not move back on the rod that is supporting it, something may have broken and it is closing and cutting the air flow, but I think that is very unlikely to have happened. To break the regulator plate the regulator knob would have to be forced against a large pressure differential inside the gun, i.e. the outer tank pressurized and the inner barrel not.

Here is a diagram of how the power regulator works. The rubber pad is glued to the plastic plate or segment, it may have separated from that segment, although this is also unlikely.

 

[Gazz]

Hi istriker,

The Slow spear is a classic example of a dry-barrel gun with a flooded barrel.
You need to check your gasket for tears, its clearly damaged.

I ordered 10 new gaskets on vidrex the other night, i think my vuoto will be out of action for some time.
I am using my flawless tomba and tovarich guns again. Not Happy Salvimar!!

 

[istriker22]

I emailed Salvimar about this issue...shouldn't be happening after only a couple of months. They want pictures of the gasket.


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[popgun pete]

I emailed Salvimar about this issue...shouldn't be happening after only a couple of months. They want pictures of the gasket.


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Hopefully we can look at any photo as well, we have already seen one that split earlier.

 

[popgun pete]

Here is a low pressure "water sucking" test that you can do with reversed action power regulator pneumatic guns like the Salvimar. You need a bucket that will be deep enough to swallow both the spear and the muzzle end of the gun when cocked. The spear needs to have the detachable spear tip removed and a blind drilled block of wood pushed onto the shaft's screw thread to stop the spear pushing through the bottom of the bucket. Now with the power regulator set to "low" (the rearmost gate position) bleed nearly all the air from the gun, but leave some in there by listening to the noise of the pressurized air as it escapes from the inlet valve. This action will only depressurize the inner barrel and the pre-chamber behind the gun's partitioning bulkhead, the rest of the gun will still be at full pressure. Then put the block of wood and the embedded and vertically held spear into the bucket, which is full of water, and push the gun down on the spear until it latches. Leave the gun like that for a minute or so, but retain your grip on the gun and never let go of it for an instant. If the muzzle seal leaks then it will soon suck water up into the inner barrel. Next lift the gun up out of the bucket and place the wooden block on the ground, keeping the gun's muzzle pointed downwards all the time. Then lean on the gun and pull the trigger, the gun will come up, but without much force as you only compressed the residual air remaining in the inner barrel when you cocked the gun. Look to see if any water comes out, if it does then you know the muzzle seal leaks. Repeat a couple of times to see if it leaks consistently or intermittently.

With the gun in the discharged state pull the spear out of the barrel by jerking it free from the piston. Attach the hand pump to the gun and pump it up until you can move the power regulator forwards easily, it will not budge until the air pressure in the inner barrel gets close to the air pressure in the outer reservoir. Because the volume of the inner barrel and pre-chamber is relatively small compared to the volume of the outer tank the lost pressure will be replaced reasonably quickly.

If performed while keeping your wits about you then there will be little drama in conducting this test, but you could also do it with the gun totally depressurized if you want to play completely safe. I would not recommend this test with the usual power regulator layout as pressure differentials there are trying to open the regulator valve in the partitioning bulkhead, not close it.

 

[tromic]

Another method for checking the seal is on this video:


Maybe the easiest would be, similar to what Pete suggested, switch the gun to low power and load the shaft. Leave the gun for few minutes in water. After that take out the gun from water and discharge the shaft in air, slowly using the loader. You'll see easily if there is a water in gun because if it would get out from the gun during taking out the shaft.

 

[grantl]

I took my Vuoto 75 out for the first time yesterday and it really exceeded my expectations in terms of performance. I have it triple wrapped with 1.4 mm mono and set at 25 bar - it is extremely fast and pulls hard on the end of the line.
Unfortunately the only fish I saw and shot at was on my first drop and I actually thought the safety was on the trigger was so heavy. I'm going to adjust it a little but other than that I'm impressed - it's really good value and well made.
One thing I would say is that loading isn't as tricky as it can be with the Tomba on my 115 which I find can somehow jam the spear which requires me to release it a little and continue loading. This isn't fun on a big gun at 27 bar, especially if it happens 2 or 3 times.

No doubt though the Tomba system will always be more durable and simple to replace an O ring if needed and it would be my first choice to convert any pneumatic.

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[tromic]

[QUOyuo"grantl, post: 933862, member: 7398"]I took my Vuoto 75 out for the first time yesterday and it really exceeded my expectations in terms of performance. I have it triple wrapped with 1.4 mm mono and set at 25 bar - it is extremely fast and pulls hard on the end of the line.
Unfortunately the only fish I saw and shot at was on my first drop and I actually thought the safety was on the trigger was so heavy. I'm going to adjust it a little but other than that I'm impressed - it's really good value and well made.
One thing I would say is that loading isn't as tricky as it can be with the Tomba on my 115 which I find can somehow jam the spear which requires me to release it a little and continue loading. This isn't fun on a big gun at 27 bar, especially if it happens 2 or 3 times.

No doubt though the Tomba system will always be more durable and simple to replace an O ring if needed and it would be my first choice to convert any pneumatic.

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Yes, you are right, it is litle tricky to load Tomba700. That is why I made Tomba700X.

 

[istriker22]

Here are the pictures of the gasket. Sorry it took so long.

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[popgun pete]

Thanks for the photos. Well it is pretty obvious that the sealing lip is torn, but what are those marks on the nozzle section of the rubber seal? I have indicated them on an annotated version of your clearest photo. Those marks must have been created by something as they would not have been there originally. Have a look inside from the rear of the front section of the detached alloy muzzle nose to see if anything corresponds to the position of those marks. To me it looks like the seal has been pushed out of shape and crushing has created those marks (circled) during loading of the spear, however the marks seem more like scrapes rather than folds or creases, but only you can tell for sure by looking very closely at them with a magnifier.

I suggest you send the busted seal to Salvimar, as if I was the person producing those guns then I would want to closely examine it for a detailed analysis of the mode of failure.

 

[istriker22]

Thanks for the photos. Well it is pretty obvious that the sealing lip is torn, but what are those marks on the nozzle section of the rubber seal? I have indicated them on an annotated version of your clearest photo. Those marks must have been created by something as they would not have been there originally. Have a look inside from the rear of the front section of the detached alloy muzzle nose to see if anything corresponds to the position of those marks. To me it looks like the seal has been pushed out of shape and crushing has created those marks (circled) during loading of the spear, however the marks seem more like scrapes rather than folds or creases, but only you can tell for sure by looking very closely at them with a magnifier.

I suggest you send the busted seal to Salvimar, as if I was the person producing those guns then I would want to closely examine it for a detailed analysis of the mode of failure.
View attachment 38985

I'll take a look and you know. Sucks now I have to dismantle this gun.


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[popgun pete]

This adjusted diagram shows what I meant when I mentioned that seal misalignment in the muzzle may be responsible for the muzzle seal being pulled unevenly by the shaft tail stop and thus being more easily damaged over time.

The stretched out seal or cuff may be nipped on the edge of the exit hole (marked in yellow) and this may also explain the general scuffing marks (but not the more grooved ones) on the outer conical face of the most recently damaged cuff.

 

[tromic]

Hi Pete,

The spear tang is rounded and perfectly smooth,
I will cut the gasket in half tomorrow and post pics.

Gazz, had you been using something to lubricate the seal, grease, silicone grease.., at least every few days?
That would be maybe helpful.

 

[popgun pete]

Superior design of the vacuum cuff and its auto-axially aligned seating in the muzzle body of the "Taimen" gun can be seen here. Contrast this with the apparently poorly thought out wall thickness of the Salvimar muzzle seal!

 

[tromic]

I think the main cause of damage to the gasket is the force (F) from ambient pressure.
On 20 m depth that force might be more than 8 kgf!
This type of gasket is better for lower deep hunts like rivers, lakes...
The only solution is well greased sealing cuff to minimize the friction cuff to shaft tail end.