Tomba - All in One barrel sealing

[tromic]

This might be another design, maybe more simple:

 

[tromic]

I would also like to try this version of Tomba700X!

 

[tromic]

With shaft and slider, small modification:

 

[tromic]

This might be TombaF700X:

 

[zmajmr]

 

[tromic]

New Tomba700X
Loading, if flexing the shaft, should be easier than with previous TombaF700.

 

[zmajmr]

 

[tromic]

Maybe this would be a solution to reduce friction during loading, if shaft is bending.
Making this modification might allow 4 x more bending of shaft than now. Might help!

Uploaded with ImageShack.us

 

[tromic]

I have done some clean up...

New Tomba models and names:



Tomba700S:
The most Simple. Could be used only with Tomba slider. Might lose vacuum if during loading move the shaft backward.
Tomba700E: Could be used with any plastic slider.
Tomba700X: Only for shafts 6,5 to 7 mm, using only Tomba slider.

 

[zmajmr]

 

[zmajmr]

 

[popgun pete]

As various "Tomba" units have been is service for some years now are you receiving any user feedback on how long the "O" rings last and whether they are just routinely replaced after a certain number of shots or when the performance suddenly deteriorates indicating time for an "O" ring change.

 

[tromic]

As various "Tomba" units have been is service for some years now are you receiving any user feedback on how long the "O" rings last and whether they are just routinely replaced after a certain number of shots or when the performance suddenly deteriorates indicating time for an "O" ring change.

There are no any feedbacks regarding O-rings. I suppose they might last long time.... weeks, months? I never changed O-ring on my gun during summer holiday at see.

The only issue reported was difficulty while loading the shaft, last 20 cm, if bending. That is why I made new Tomba700X. Regarding performance I believe Tomba is maybe the best kit for shaft with the slider. I recently received a feedback regarding new salvimar kit used with devoto slider. The user (an Italian) noticed significantly lower performance comparing to "free shaft". I remember from my previous mesurement of speed that Tomba slider (the previous one using nylon tied to its neck) had 53 % better performance (energy) to devoto slider. That is about 24 % higher speed, same as "free shaft" against shaft with devoto slider.

 

[tromic]

I actually reduced the swinging angle to 2 º. That is enough. Also the edge where the bigger (inner) O-ring must pass by is made to be 45 º, not to be damaged the O-ring during insertion. After spear is loaded and vacuum is obtained, spear is in center of muzzle boring. Inner, plastic part, is held in its center position because of vacuum.

 

[popgun pete]

Now I understand, rather than on initial insertion the shaft is instead being pulled slightly to the side as users try to force the last part of shaft travel into the gun and that is displacing the "O" ring enough that the vacuum seal momentarily fails and sucks water into the inner barrel. That can happen on a certain length of gun when your loading hand moves from a pulling back to more of a pressing action to achieve the last few centimetres of spear insertion into the gun. For me that is what happens on a 70 cm speargun, too long to load off my thigh and slightly too short to load off my foot. Shorter guns are easy to load as you don't change your direction of force application much and longer guns your hand is still pulling backwards as the mechanism clicks into place, provided your arms are long enough.

So in a sense you are having the muzzle bore track the spear alignment by allowing it to rock slightly while maintaining the slider and "O" ring central to and perpendicular to the "O" ring seat in the muzzle. That is certainly better than rocking the smaller OD slider and wearing out its tail end where it engages the muzzle bore opening. In the "Taimen" the slider temporarily locks into the muzzle nose piece and being a few centimetres forwards of the muzzle seal keeps the spear shaft properly aligned as it passes through the seal. That spacing makes the muzzle slightly longer in terms of the set back of the vacuum seal from the entrance to the muzzle. You could have done that with a longer slider penetrating deeper into the muzzle, but your tracking muzzle bore keeps the slider short which is what you want in order to reduce its mass, so it is a good idea.

 

[tromic]

I actually reduced the swinging angle to 2 º. That is enough. Also the edge where the bigger (inner) O-ring must pass by is made to be 45 º, not to be damaged the O-ring during insertion. After spear is loaded and vacuum is obtained, spear is in center of muzzle boring. Inner, plastic part, is held in its center position because of vacuum.

 

[zmajmr]

Now I understand, rather than on initial insertion the shaft is instead being pulled slightly to the side as users try to force the last part of shaft travel into the gun and that is displacing the "O" ring enough that the vacuum seal momentarily fails and sucks water into the inner barrel. That can happen on a certain length of gun when your loading hand moves from a pulling back to more of a pressing action to achieve the last few centimetres of spear insertion into the gun. For me that is what happens on a 70 cm speargun, too long to load off my thigh and slightly too short to load off my foot. Shorter guns are easy to load as you don't change your direction of force application much and longer guns your hand is still pulling backwards as the mechanism clicks into place, provided your arms are long enough.

So in a sense you are having the muzzle bore track the spear alignment by allowing it to rock slightly while maintaining the slider and "O" ring central to and perpendicular to the "O" ring seat in the muzzle. That is certainly better than rocking the smaller OD slider and wearing out its tail end where it engages the muzzle bore opening. In the "Taimen" the slider temporarily locks into the muzzle nose piece and being a few centimetres forwards of the muzzle seal keeps the spear shaft properly aligned as it passes through the seal. That spacing makes the muzzle slightly longer in terms of the set back of the vacuum seal from the entrance to the muzzle. You could have done that with a longer slider penetrating deeper into the muzzle, but your tracking muzzle bore keeps the slider short which is what you want in order to reduce its mass, so it is a good idea.

Hi Pete, you did not understood my father good as I understand, there is no problem with losing vacuum, you can bend spear as much as you want during loading of spear , you will not lose vacuum at any stage of inserting spear deeper and deeper in to the barrel.
Thing that happens with old design of Tomba kit (Tomba700, 650, 800,...) is if you bend spear you are making your life harder , why , because at certain angle of bending spear, stainless steel cone ring can block further movement of spear in to the barrel and usually you can feel that the most, last 20 cm that you have to insert the spear in barrel (because then spear can bend the most if you start to bending it from the start). Some people understand that they need to load spear parallel to barrel as much is possible and other one think they are not doing that but actually they bend spear. I personaly had same problems with locking during loading and this is only reason why I prefer free shaft kit, and as you can see I have free shaft kit on my Mares Sten 11 (100 cm length) and on Asso 135 (which was fail with 6.5 mm shaft). Free shaft kit with 100 cm long gun and 6.5 mm spear is good combination and Asso 135 and 6.5 mm shaft with free shaft kit is total fail, you can not hit on what you aiming for.

So , as in free shaft kit you have plastic parts which are in contact with spear, you have less friction if you bend spear, you can gradually feel how friction increases if you bend spear, if you bend spear while you have combination of kit where parts that are in contact are two stainless steels and plus cone ring have edges then at certain angle spear will block / stuck unless you correct spear from bent to straight shape.

My father put some pictures of that but as it seams he did not explained what is the problem.

Problem is, if you bend spear to much with regular Tomba kit at certain angle spear will be blocked because of stainless steel cone ring inside of Tomba adaper.

At Tomba700X kit you have movable tip in which is cone ring so there is no locking of spear because cone ring follows bending of spear, so there is no contact : edge of cone ring - spear.

I hope people understand now.

 

[popgun pete]

Well I was not sure what the "difficulty" actually was as up until now I had thought that it must have had something to do with breaking the vacuum seal as I never picked up from your previous comments that it was the increase in muzzle loading effort at a certain spear insertion distance that you were talking about. Thanks for clearing that point up, plus I was starting to be confused by all the many "Tomba" versions on these pages, but the reason for the latest self-aligning muzzle is now clear and as I said previously it is a good idea. It would also be good to have user feedback on these issues and be able to read about it here, then people can make informed choices about which type of system they purchase.

 

[tromic]

Well I was not sure what the "difficulty" actually was as up until now I had thought that it must have had something to do with breaking the vacuum seal as I never picked up from your previous comments that it was the increase in muzzle loading effort at a certain spear insertion distance that you were talking about. Thanks for clearing that point up, plus I was starting to be confused by all the many "Tomba" versions on these pages, but the reason for the latest self-aligning muzzle is now clear and as I said previously it is a good idea. It would also be good to have user feedback on these issues and be able to read about it here, then people can make informed choices about which type of system they purchase.

I have been starting to think about finding a solution in this post:
Tomba - All in One barrel sealing
However, here I had not accurately identified the real cause of difficulty of loading when bending the shaft.
Presented image would also be a solution, but in case of even more bending. But higher friction during loading occured at lower bending when the bending shaft started touching the lower edge of stainless steel cone ring and the upper edge of plastic slider. After making contact in these two point some kind of lever with shaft was established.
The latest Tomba700X has an additional bonus - easy checking if ther is a vacuum inside barrel behind the O-ring. If there is a vacuum the inner plastic part, holding the shaft, will come back to its center position if moved a side. That is because vacuum creates a force of about 2.7 kgf pulling the plastic part back.
Additionally, stainless steel is not in contact with aluminum, so there is no, or much less, electro corrosion.

 

[popgun pete]

What you are really talking about is the shaft bowing and thus slightly changing approach angles as it passes through the muzzle restriction imposed by the stop ring and slider. Now everything is much clearer as muzzle loading the shaft when not parallel to the muzzle is a completely different problem and can result in bending the spears and maybe damaging the gun, something that beginners are capable of doing when their attention is not focused properly on the task.

On a standard wet barrel gun the stop ring and slider are not pulled tightly back into the muzzle, they can rock and move forwards if the shaft bows and changes its angle while entering the muzzle, plus there is a small amount of lateral play in the seating recess, whereas in the Tomba system they are held back in their seating recess, so they cannot tilt or move to accommodate the change. I had not thought of that being a problem, but now you have a clever solution to it and a vacuum indicator as well which is very good, in fact with a discernable travel distance it would be a very good indicator if you could detect the change in position by just looking at the muzzle.