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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.

foxfish, I guess that (2) would have lower drag. Actually I already did similar measurement and got the same result with 7 mm shaft and the slider, as with 6.5 mm shaft and the thin fishing line tied to the head of the spear, as at the last picture. The slider that I used wasn't as good as could be. With my new slider the result could be even better. I don't like very much the action of the spear when the line is attached to the head.
 
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A suitable muzzle to convert to a Tomba type arrangement is the extended muzzle that Mares supply on their "Miniministen" models to bring them up to a legal length in some countries. This muzzle is machined from hexagonal aluminium bar to provide a short hex section so that the muzzle can be removed or tightened up with a spanner, the rest of the barrel is turned down to 24 mm diameter both in front of and behind the hex section. Coincidentally the recess in the nose is 24 mm deep where the stop ring sits, so there is plenty of room to mount the sealing elements that will sit on the shaft. The muzzle contains a dead space which will always hold water, but that should pose no problems. With this longer muzzle fitted spears of the same length were used, it was just that the slider and line slide assembly sat further forwards on the shaft than usual.

I plugged the small relief port holes in one of these muzzles with nylon plugs turned up on my lathe and also made a sealed slider out of delrin, but I had problems with leaking on the shaft seal and discontinued work with the system. This was back in early 2004 after I had first heard about the Mamba in 2003 from my overseas associates. As I was involved with hydropneumatic developments I forgot about doing any more work with the vacuum barrel, but possibly this muzzle may be still available.

The extended muzzle is 14 cm long, but otherwise it is the same muzzle as fitted to the Mares "Reef" series which was a continuation of the first "Sten" series shape. It was also fitted to the Competition Line version of the "Miniministen", that is how I obtained my example. I changed it over to a normal muzzle rather than machine the original down to the standard length. The longer muzzle was a useless extension in my opinion and added unnecessary weight to the gun, although that model was a sinker even without it fitted, but its advantage for vacuum barrel work is that there are no threads to seal. Just checking on the current supply of "Miniministen" with the "Cyrano" style handle (Sten 2001) it is still being offered with this long muzzle here in Australia. I imagine that the muzzle can be purchased from Mares as they will have been made in Italy, not here.
 
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Thanks, Peter. This was an useful information. This would help the owners of Mares Sten and similar 13 mm barrel guns to easy convert to vacuum barrel. The boring in the muzzle is, I suppose, 14 mm. Cyrano has 11.4 mm. I am thinking about to buy a lathe but I have no place for it. It is difficult to make thinks only with hand drill and the grinder. From the latest Tomba I already have a new idea but I need a lathe.:friday
Regards, Tomislav
 
You can buy some quite good lathe kits that fit to a electric drill?
You can buy some very compact lathes too I think you really need one & Christmas is coming?
 
foxfish said:
You can buy some quite good lathe kits that fit to a electric drill?
You can buy some very compact lathes too I think you really need one & Christmas is coming?
Click to expand...

The good think is that there would not be a tomba as simple as now if I had a lathe. But I would like to have one. Now I have some other ideas how to increase the speed and the range of the spear. That is something about the line release. It would be a secrete for now. I suppose that it would be possible to increase the range for about 50 % or more. Instead of 3 m, 4.5 m, same gun, same bars in it, same spear and line.
 
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This was an idea:


This is the latest tomba (in the middle): MicroTomba

OD of the O-ring on the shaft is 10.5 mm, same as Microspeed slider. Plastic and stainless steel parts OD is 10 mm.

I use it with the Omer Airbalete spear with some modifications:

The plastic spacer ring between the O-ring and the slider could be omitted.
 
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Reactions: Don Paul and devondave
foxfish said:
You can buy some quite good lathe kits that fit to a electric drill?
You can buy some very compact lathes too I think you really need one & Christmas is coming?
Click to expand...


This sell's used/ like new condition at our local swap meets around $500.00. Ok for spearguns but not gunsmithing.Ok for low duty cycle.
Cheers, Don
 

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Hi Tromic, I see you reversed the flopper retainer ring on the Airbalete shaft.
Are you not concerned that the ring will not disengage on flesh contact on shaft entry? I found the mircro slide had very sharp hole edges on the two slide rings in my kit. I deburred them and polished smooth. Maybe I had a bad batch.
Cheers, Don Paul
 

Hi, Don Paul
I didn't reverse the flopper retainer ring. I made a new one. I suppose the original ring has more drag because it has the front side like a parachute. This new ring, when disengages becomes the front part of the slider.
I bought a lathe. This MicroTomba is the result of my first use of the lathe.

Cheers, tromic
 
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The new version looks like the best yet - Don, that might be a future improvment for your new gun?
 

Thanks tromic, After work yesterday I looked at your images again and saw
that, yours has a different profile. I like your work with MicroTomba what lathe did you procure?
All the best Don.
 
foxfish said:
The new version looks like the best yet - Don, that might be a future improvment for your new gun?
Click to expand...

I'm going to use it with stock internals and 30 bar at first, and only make changes to terminal components to match the power of the big fish I will stalk.

I really enjoy lurking on tromic and Peter's discussions, I just wish I could type with at a faster rate, I'm a newbie.

Nice work tromic.:friday

Cheers, Don
 
I not sure if you would have to adapt anything inside the gun but by using tromics dry barrel effect you might have a much smother firing cycle & of course more power.
But like you say best to use the gun in standard trim first
 
foxfish said:
I not sure if you would have to adapt anything inside the gun but by using tromics dry barrel effect you might have a much smother firing cycle & of course more power.
But like you say best to use the gun in standard trim first
Click to expand...

I believe I have no warranty on my second hand Airbalete to worry about,
but I want to respect the engineering and work with it before seeking performance mods. I'm going to be going all Omer this year(blue h2o gun exception)...Viva Italia.....
and any unknown jobbers.
Sorry for the dis-rail tromic.

Cheers, Don
 
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That looks like a nice piece of kit Tromic, you should be able to really perfect your designs now
 
I am curious about which vacuum kit is better regarding the performance of the spear at say 4 m, MicroTomba or Tovarich. I believe the winer could be MicroTomba. Tovarich is more simple but I do not like to tie the line to the front of the spear.
 
MicroTomba (left) and regular Tomba (right). Both for 7 mm shaft. Regular Tomba is OD 11.3 mm (for Cyrano with adapter to the muzzle which make the boring 18 mm deep).

 
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Cross section of the adapter and the ring:



Inner part of the boring in the adapter is a taper so is the sliding ring.
I am preparing to make this for my new tomba. The taper have to insure center positioning of the slider ring and better sealing after shooting.
 
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Reactions: Don Paul
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