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Tomba - All in One barrel sealing

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.
This was a problem that I tried to solve with Tomba65S (Tomba7S) in case of possible improper loading:


If during loading the gun, one bend the shaft as on a picture, some rubbing and higher friction might occur between the stainless steel ring and the shaft. Omer solved the same problem on his Airbalete using microspeed slider. That is why the loading is easier than on other guns. But microspeed slider has another problem - it is too heavy!
 
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This is a modification to Tomba11 (6,5 mm shaft), Tomba11S. Unlike Tomba65S that has cone shape line slider, this is similar to previous Tomba11 but the slider also serves to support the shaft during loading and to reduce friction to the stainless steel cone ring. Another modification is that now I will tie a constrictor knot with 1.5 mm spectra on the line slider, instead of to tie nail knot with 1 mm mono. This will be much safer and stronger. The slider can tilt in adapter for about 1.2 deg. There is also an another benefit of this design. The O-ring, sandwiched between cone ring and the slider takes the main impact while in adapter. This makes less chance to O-ring to jump over the cone ring or the slider back end. This jump might occurred
if the O-ring was fat and very slippery.
 
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For Tomba, only with guns Sten, Cyrano, Spark, Stealth holes in head could be easily closed with tape or rubber tubing. For all other brands, the better (cheaper) solution is a head without a holes.

I think Tomba is the most reliable and durable kit (except Tovarich). There is no possibility of entering the water if the O-ring is fine. Gap of the shaft is about 0.1 mm. Only if after longer use the parts wear out so that the gap is larger than 0.3 mm can result in water entering the gun.
 
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You have been very busy with forward development and hard parts. Bravo to you and your son for pushing the curve in complete transparency. My custom Airbalete will look forward to your products setting the standard.
My gun is still leak free and dependable at 25 bar for the last year.
I'm just now going to the second cone after the use this season.

Cheers, Don
 
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Thanks, Don! I prefer transparency. I had always rather bought some thing when I knew how it worked. Than I had more confidence in it and it helped me to use it better. When I was a child, the first I did when I got a toy, was to see what is inside.
 
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This problem of damaging the O-ring might be, maybe, solved using two O-rings. Two O-rings arranged this way help each other to stretch more easily and to jump over the shaft tail stop diameter step.





I am not planning to try this, just was thinking about this possibility. I am sure this would work better than the previous design which was working too, but with possible damage of the O-ring after some (shorter?) time of usage. Anyway, easier and more simple solution would be using different sealing element instead of O-ring, similar to what STC is using for x-power. I am happy with the performance of the latest Tombas so I do not need to change anything or to make different design which would be more demanding to make and to use. This design requires screwing and unscrewing of the screw on the front end of the muzzle, similar to Evo-Air design.

Another possibility instead of using additional O-ring would be to have longer free space for water, where this water might help in sweeping/jumping the O-ring over the tail end stop diameter before reaching the delrin part.
 
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This might be an improvement to Tomba7:



There is additional steel cone ring for centring the shaft during loading and shooting. The main problem is that the ring has very thin wall, 0.5 - 0.6 mm.

In the upper part of adapter might be a spring to replace screwing and unscrewing action. :friday
 
tromic said:
Tomba - new names:


Click to expand...

Marko finished the first Tomba650 for 6.5 mm shaft yesterday. I haven't a picture but I measured the weight of cone ring and the slider. They were both only 3 g. The slider is only about 20 mm long. This is the lightest configuration for now. For Tomba650S the same parts were 4 g because the slider was longer. As I wrote before having the shaft parts as light and as short as possible was my main goal. In same time the slider will be tied more securely than before, with a piece of 1.5 mm Dyna Spear. Having lighter parts means higher possible operating pressure in the gun without damaging the steel cone ring.

 
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Peter, I think this would be better. Maybe no screwing-unscrewing is necessary. O-ring might be pushed in a sealing place by the line slider.
After shooting (as on picture) O-ring might be pushed in a front position, by friction to the shaft, before being hit by the shaft stop diameter step.
In that position there is no friction to the O-ring and ID of the O-ring is same as the OD of the shaft butt (8 mm).

 

Making the stop ring too thin in cross-section will work against its durability when fighting a fish even though it will be less likely to be deformed when struck by the spear tail stop diameter travelling at maximum velocity (i.e. muzzle exit velocity). It is the rapid acceleration that destroys them. I think that a compromise has to be found where you expect to replace the stop ring after a certain amount of work, especially if the gun is very powerful. Spears and tips are consumables, so adding the stop ring to the spares inventory is not a big concern if they can be readily sourced. I would rather have a reasonable size stop ring and a light line slide. I have seen how my "Black Sea" gun can make short work of line slides no matter how light they are. Most annoying aspect is freeing the stop ring from the shaft jam, I think I should build a tube or short well into my diving knife butt to knock it free.

The jumping "O" ring would be a good system to perfect as it leaves the seal inside the muzzle and one can shoot a bare shaft. If the seal lasts a dive session that would be OK, maybe twenty shots, then you replace it for the next outing. "O" rings are inexpensive if bought in multiple quantities. Changing specially manufactured seals is a less attractive proposition.
 
Stop ring on the picture is not very thin. It is 11 mm OD and 4 mm long.
 
popgun pete said:
My comment was directed to the previous image "Tomba7", not the one that was actually included in my reply.
Click to expand...

Yes, you were right about that previous. It was too thin. There were also other problems with that design, for example how to load the shaft and push that thin cone ring to its place behind the O-ring. But I suppose this last might work, with zero friction soon after shooting. The only question is if would it be possible to push the O-ring in sealing position with the line slide or screwing/unsrewing would be neccesary.
 
Thanks Don! I suppose the kit will be sent to you today.

A knot like this might be an alternative to constrictor knot for new shape plastic slider. I believe it could be used with the previous shape of plastic slider that was for mono 1 mm, too.
It would not over tighten the neck of plastic slider and will be very reliable and more hydrodynamic than constrictor. I had not finished tying it strong so one can see how to tie it.



I have similar to this but thinner, 1.5 mm, 220 kg.

 
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