Tomba - All in One barrel sealing

[popgun pete]

As tromic says simply changing the tip of a muzzle such as the STC device will not convert the gun to "normal" wet barrel operation as the muzzle lacks relief ports. The resultant flooded barrel would suffer from hydrobraking due to the water trapped around the body of the shaft having to pass through the small annular gap at the muzzle. On a Mares gun that shoots 8 mm diameter shafts this gap is usually 1 mm around the shaft body, that is because the muzzle bore reduction is 10 mm in diameter. It is that size in order to allow the 9 mm diameter shaft tail butt to pass through it. On a "Cyrano" or "Spark/Stealth" the shaft tail butt is 8 mm in diameter, while the muzzle bore reduction is 9 mm in diameter, so the annular gap for water to pass through is again 1 mm with a 7 mm diameter shaft. That is why a "Sten" shaft tail will not pass through a "Cyrano" muzzle, the 9 mm diameter tail butt will not go through the 9 mm diameter muzzle bore reduction as there is zero clearance. So without any muzzle relief ports the annular gap to be sealed for a dry or vacuum barrel system is only 1 mm wide at the muzzle entrance, so any "O" ring to plug the gap has to be thicker than 1 mm and has to resist being sucked by the pressure differential through the gap, especially if the shaft is not sitting dead centre in the bore. The plugging "O" ring has to be accurately controlled in terms of how it sits in the muzzle in order to achieve a dynamic seal as the shaft passes through it. That is what tromic has achieved with his design and now you can appreciate why it can be done with only one "O" ring, it just needs to be adequately controlled and protected from being wiped off the shaft tail.

Anything in the way of a demountable muzzle tip that unscrews has to have a seal or gasket somewhere or water will suck in along the attachment threads that connect it to the main muzzle body. Hence such changes need to be made under conditions where you can ensure that there is a seal.

 

[popgun pete]

STC muzzle drawing "sliced and diced" with parts nudged sideways to show how it assembles, based on the web-site's original. Note the gaps where an "O" ring seal sits in the nose section to seal off the screw thread. There is probably another "O" ring or gasket in the join to the rear body section to seal off those screw threads. Horizontal black bars are the connecting screw threads. Conical seal with inner lip sits in nose section, but is not shown. Note that the shock absorber has an energy absorbing sleeve (in red) and some other material (in yellow) which the nose of the piston crashes into. Now you can contrast how the two systems work, STC's and tromic's version. If the STC muzzle uses a shaft with a tail butt then I cannot see how it gets through the muzzle seal without causing it to dilate and contract after the shaft butt passes through it. One gun that attempted this feat was the hydropneumatic RPS-3, the step at the butt end of the shaft was 9.5 mm diameter compared to the shaft body of 9.0 mm diameter and was even profiled as part of a spherical section to ease the passage of the 0.25 mm "bump" through the seal, however the seal was soon damaged as pieces progressively busted out of it. The seal rubber was made of terrible stuff which did not help matters. It was held in the muzzle, in a similar fashion to the STC muzzle, by the removable nose cone.

 

[peacenluv]

Hi there popgun Pete. The STC shaft tail is made from extremely thin material and has a very low profile, protruding less than the Devoto or Mares shaft tails, but just enough to hold the slider. Because it was so thin, the first versions ripped apart when shooting if you loaded the gun to over 23 or 24 bar which really sucked. I don't know what kind of metal it was, but it was weak. It actually even broke open if you screwed it too tight. Now they changed the material to titanium which holds up much better. I'll try to take a picture of it next time I get out to the beach house.

 

[tromic]

This is idea for my new Tomba - MiniTomba:



Uploaded with ImageShack.us

This will work without the plastic ring on the shaft. The o-ring in contact with the taper metal ring lies on the taper part of the adapter.

I expect lower friction during loading - easier, smooth loading, better sealing, still more hydrodynamic ...

This MiniTomba adapter could be easily converted to tovarich like system (shaft without the line slider):



I actually did it temporarily few times when I compared Tomba to Tovarich system.

This is similar to new Seatec Evo-Air but I think more convenient for use. Before loading one have to push on the front of the adapter to move the O-ring deeper on the cone part of the adapter. That is all! Other important think to mention, behind the adapter there is the original muzzle with holes for water which are covered with a rubber tubing that acts like a valve. So in case same water leak into the muzzle (damaged O-ring) there is a way out thought that valve. Also, removing the tubing we have water barrel gun instantly.

 

[tromic]

This was one of the first versions with the cone steel ring:



Later came this type:



And this is the latest adapter and the cone steel ring shapes:



This is a combination of the two previous versions. O-ring comes on the beginning of the cone part of the adapter just after the cone steel ring. Cone steel ring is more slim than the first, longer and with more hydro-braking. The face of the ring adjacent to the O-ring is conical.

 

[tromic]

I also decided to change the naming of my Tombas:
There will be three basic types of my Tombas:
Tomba10 - For 6,5 and 7 mm shaft. OD of the Shaft with the O-ring is 10 mm.
Tomba11 - For 7 mm shaft only, OD 11 mm.
Tomba12 - For 7 and 8 mm shafts, OD 12 mm.

 

[Don Paul]

Received the Tomba kit for my Airbalete speargun today. The machine work is precise and burr free, the anodize finish flawless. Bravo tromic you and your son are true machinists and perfectionists.:friday Thank you very much for allowing me to be a part of your development work and testing.

I am planing on installing the kit this week end and weather permitting heading on a shore dive on Sun for a hunt. As soon as the season ends (30 days) I plan on starting my performance tests and comparisons to stock gun specs along with images. Will shoot some pictures of the install this week end. I will start the gun off at 20 Bar for hunting.

Cheers, Don

 

[tromic]

Received the Tomba kit for my Airbalete speargun today. The machine work is precise and burr free, the anodize finish flawless. Bravo tromic you and your son are true machinists and perfectionists.:friday Thank you very much for allowing me to me a part of your development work and testing.

I am planing on installing the kit this week end and weather permitting heading on a shore dive on Sun for a hunt. As soon as the season ends (30 days) I plan on starting my performance tests and comparisons to stock gun specs along with images. Will shoot some pictures of the install this week end. I will start the gun off at 20 Bar for hunting.

Cheers, Don

Thank you too, Don. Waiting for your testing.
Cheers, Tomislav

 

[foxfish]

Fantastic news - we will all await the testing :friday

 

[Mark Lamont]

Okay, so you got my interest up and I read and then went to check on my Scubapro Pneumatic. It was designed by the same engineer as the Mares guns. I read the word "hydro braking" and take exception in the case of the Mares second generation "Scubapro Pneumatic". There are four cross drilled 3/16 in diameter holes in the muzzle that act to allow the water in the barrel to escape the compression of the fired shaft or more accurately the end fitting in addition to the space between the inner barrel and shaft end. If one looks at a pure cross section it seems like there is water restricted in the inner barrel.
So, if the fluid is restricted between the inner barrel and the muzzle whether it be air or water the result is the same.
I may be missing something but I don't think so. I have made multiple 26 foot shots and landed fish with my guns.
Mark

 

[Don Paul]

Mark, I have the sister gun I traded for from Rene years ago. I would never covert it...too much history. I you ever want to sell yours let me know.
Yes your gun was a 26 ' killer. There is a great discussion here:
http://forums.deeperblue.com/pneumatic-spearguns/81902-vacuum-barrels-aka-dry-barrels.html

Cheers, Don

 

[Don Paul]

Some images of the Tomba parts for Airbalete and the stock piston assembly
as removed from my Airbalete.

My first step was to wash the gun in fresh water to remove any trace of sand or salt deposits. The handle was then removed to take a pressure reading and depressurize the barrel assembly by releasing the fill valve pin. I am happy to report the Nitrogen I filled the gun with many months ago still held at 30 Bar at the same temp.

After using a short rod to press the piston 6'' back into the inner barrel I
carefully unscrewed the end fitting with a thin rod. The piston was removed
and the inner barrel was inspected with a borescope I have had kicking around many years.The inner barrel was found to be un-scored and water free.
After several sandy beach surf entry's.

The next image shows the piston assemble with very small droplets of water from the wash down process on the scraper ring.

I washed the affected parts in rubbing alcohol and followed with a canned air blow down. After a application of Omer Airgun grease to the piston assembly and the O-rings the Tomba parts were installed.
I plan on pressurizing the gun tonight followed by a tub submersion to check for any leaks.

Cheers, Don Paul

 

[Don Paul]

The Tomba parts assembled very nicely with no binding on hand assembly.
Only requiring me to me to metal finish the height of the two dimples on the
sleeve under the unused power reducer plastic port sleeve as seen n image 4 of my previous post. More later....

Cheer Don Paul

 

[foxfish]

Wow, getting excited now!
Cant wait for the real life test...Tromic makes Don a custom part - don fits part - Don kills fish - don tells us how it works = Great stuff.

 

[Mark Lamont]

Hey Don,
I don't know if you remember but I have a number of the old Scubapro guns. The shortest shoots a 54 inch 5/16 shaft and with heavy monofilament line I have a 27 foot shot (yes a slight lob) but you may remember a nice WSB and a halibut landed both with those long shots. Thanks again for scaring up the halibut.
The other lengths are for a 60 and 72 inch shafts. In the Scubapro design and maybe the new Mares design there are cross holes drilled in the muzzle much like flash supression in a rifle allowing the escaping fluid in the barrel to ambient and without restriction.
I can see the possible difference in performance but think it may be outweighed by addition of all of the plastic stuff trailing at the back of the shaft. One of the real benefits of a pneumatic gun is it's ablitiy to vary power. The Scubapro gun has a thumb switch for exactly that reason. I changed handles on my guns to elimate that feature.
I think.............there is a lot of misunderstanding about the pneumatics. I have had mine since '82 and you know how much we and I dove in those days. I have only changed the oil once and that was for a check of the system. I never rinsed my gun and a couple of years ago I developed a slow leak in one. This is now 28 years later. The first year after developing the Panther I started using the pneumatics and never quit. I didn't miss one shot in the first three years until a little 10lb bluefin rolled away from my shaft 6 feet off the end of the shaft. The standard muzzle velocity was measured at 50 miles per hour. Quite a little fish I'd say.
Anyway back to reality. If one is diving at about 100 feet and shoots the calculation for the difference in inner barrel versus the ambient water pressure is negligent. Personally I'm not that good. By the way, I will say that the inner barrel colapsing is the weakness in the gun but that too is factored in and not much chance of it happening in reality. I consistantly over power my guns using a special first stage scuba regulator. There are a lot of options for pressurizing the barrels.
This has covered a lot of territory and there is a much more info to consider in learning about a simple, effective quality gun for bluewater hunting.
Mark
Is there a spell check here?????

 

[Don Paul]

Wow, getting excited now!
Cant wait for the real life test...Tromic makes Don a custom part - don fits part - Don kills fish - don tells us how it works = Great stuff.

Please don't hold your breath for any big game fish as it's been raining for 3 days so the Vis is piss and the game fish season over when the Halloween decorations come out. I do dive halibut in the winter and I will harvest some local Calico bass for the table when I find a good one. If I am lucky the big White Sea Bass will stay around till the winter storms rip out the kelp up to the North of me. I quit shooting our local Sheephead years back but I may harvest one for tacos before our Laguna MLPA closure this Jan.

This bonding of Speros on DB is very cool indeed and I really like the warm relations many of us share here. Thanks tromic, and the DB members and staff. You helped me through a tough year.:friday
Cheers, Don

 

[devondave]

Don't want to derail this brilliant thread in any way, but . . .
Don, how do you rate the OMER airgrease?
Does it really replace oil like it claims to?

 

[Don Paul]

Is there a spell check here?????

Mark, if you left click on the suspect word it will offer spelling options in a pop
up box.

Yes I remember all the air guns we had on board for many years, That big Italian team gun inspired me for many years and is what lured me to revisit the Dark Side. Rene recently broke the Stripe Bass record with one, I have the other 130 he had. The Scuba Pro almost swept the Blue Water Meet
with those big airsprings..

The new slide ring Tromic fabricated is very sleek compared to the early bits in his development cycle. I just have fun with using new methods and gear other then the guns I once built.

Cheers, Don

 

[Don Paul]

Don't want to derail this brilliant thread in any way, but . . .
Don, how do you rate the OMER airgrease?
Does it really replace oil like it claims to?

I had a very good look inside the barrel with me borescope sorry I don't have the image download cord at home. I also inspected the sear with a hi power lupe and found no displacement of metal or galling. So I must say in the Airbalete application the Airgrease is doing it's job. Fork oil is what I use in my collection of vintage airguns. I like how it slosh's around inside the barrel
coating the old metal working's. The Italians using the Airbalete for years would be the guys to ask.......Spag where are you?

I will bring the recent mods over to my Nitrobalete post later so as not to derail Tromic's thread.
Cheers, Don

 

[tromic]

Some images of the Tomba parts for Airbalete and the stock piston assembly
as removed from my Airbalete.

My first step was to wash the gun in fresh water to remove any trace of sand or salt deposits. The handle was then removed to take a pressure reading and depressurize the barrel assembly by releasing the fill valve pin. I am happy to report the Nitrogen I filled the gun with many months ago still held at 30 Bar at the same temp.

After using a short rod to press the piston 6'' back into the inner barrel I
carefully unscrewed the end fitting with a thin rod. The piston was removed
and the inner barrel was inspected with a borescope I have had kicking around many years.The inner barrel was found to be un-scored and water free.
After several sandy beach surf entry's.

The next image shows the piston assemble with very small droplets of water from the wash down process on the scraper ring.

I washed the affected parts in rubbing alcohol and followed with a canned air blow down. After a application of Omer Airgun grease to the piston assembly and the O-rings the Tomba parts were installed.
I plan on pressurizing the gun tonight followed by a tub submersion to check for any leaks.

Cheers, Don Paul

Very nice job and nice pictures Don! There is only one think I am little concerned about this Tomba for Airbalete. Because there is no water escaping holes covered with rubber tubing which function like a valve, it would bi maybe good to let the water out from the muzzle after inserting the shaft and before pushing the O-ring in to the muzzle. It is possible that small amount of water after loading the gun get in to the place between the piston and the shock absorber. After shooting some of this water could be injected in the gun passing the piston's sealing. Maybe this would not happen but have on mind as a possibility. Waiting for you real test in the sea.
Regards, Tomislav