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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.
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That was my concern too, but i think it would work without loosing air. First part of lever movement is 4.8 deg (2 mm up) up to horizontal position. Trigger pin would tilt right for 0,1 mm. Next 4.8 deg of lever movement (total 4 mm down-up movement), trigger pin tilt back, in opposite direction for 0,1 mm. This movement by tilting is actually less because pin can slide in respect to lever.
 
The same principle, exploiting the friction forces in order to achieve the balance used Jack Prodanovich, 40 years ago. Here is a comparison of its mechanics and an another triggering mechanism. Although seemingly similar, yet very different in essence. Although the two-part mechanism, have no problem soft trigger even with several strong bands.



In design that I use for pneumatic gun trigger that principle is just a half of story. Another half is using a pressure balance in a same time.
 
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I have a suggestion to remove the risks from the sear tooth angle experiments, safety being something that I am always concerned about. You can make yourself an all-metal piston with a screw thread in the piston nose to accept a long rod in place of the spear shaft. The other end of the long rod has a screw thread to attach a large weight simulating the load of a charged gun or a platform to which you can add weights. A water container that you can fill is another possibility to change the weight on the rod. The gun (with no air pressure inside it and the inlet ball valve removed) is lifting vertically to apply the load and you can see what happens to the sear lever as the load goes on and whether the load on the piston is held or released by the sear lever. Alternatively use a set of large washers, a large coil spring (e.g. engine valve spring) and a nut to compress it to apply a variable load at the muzzle end of the rod, bracing this spring against the front of the gun's muzzle. That way the gun will not have to be vertical for the sear lever tests. Once the sear lever angle changes are evaluated you can advance to the pressure tests with a bit more certainty. It may be possible to carry out these preliminary tests with the air tank removed, speeding up the process to change sear levers in the gun as you evaluate them.
 
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Interesting suggestions, Peter! That is similar to what Jack Prodanovich did testing his trigger mechanism.
In may case, pressure & friction balanced trigger would not work without pressure in a gun, so the method should be changed. Maybe it seems the trigger pin would be under high stress, because it is tiny, but the greatest force on it is just about 2 kgf on 30 bar. I will use the gun on not more than 25 bar (13 mm piston). When calculating the angle "alpha" I used friction coefficient. To be certain about it I measured it. It is surely not less than 0.1. If it would be more than 0.1 "miracle-angle" would be higher than I took in calculation so safety would be also higher, but it would be also necessary to apply higher force on the trigger to shoot the gun. If the friction coefficient would be 0.11 the angle for pressure independence would be 12.1 deg. I will make angle 11.2 do 11.6 deg. Optimal would be 11.53 deg for friction coefficient = 0.1.
Regarding safety, the only way the gun accidentally might shoot would be in case of trigger pin and sear lever joint breakage. Even the breakage of spring above the sear lever would not cause accidental shooting. The trigger would just become softer than normally. Changing the angle is something that could not happen suddenly and it would be noticed because the trigger would become gradually softer than normal. I always load my guns under water, and especially this gun with hydro-damper mast be loaded under water, or the damper would not work. I would surely use my Easy Loader that gives additional safety.
 
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Evaluating the tooth angle is very important as the design depends on that doing what you want it to do for the rest of the concept to work. The external loading up of the sear lever method was suggested to eliminate depressurizing the gun each time you refitted the sear lever and pumping it up again after changing the tooth angle. Small increments of metal need to be removed to find the balanced sear lever configuration as not only is the sear tooth angle important, so too is the exact distance of the sear tooth face from the pivot pin axis at the effective contact point between the sear tooth and the piston tail's mushroom head. The effective contact point is not necessarily at the base of the sear tooth and the outer periphery of the mushroom head. Jack Prodanovich found that he had to experiment to adjust for the contact point being slightly further up on the sear tooth face than a drawing of the interaction would have suggested.
 
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I will not change the sear tooth angle for the test. That will remain as it was, about 90 deg. It should work having the right angle on piston side only. Latter, if it would work well, I might match both the angles. I just rounded the sharp edge and polished the tooth so made it smooth, not to scratch the opposite side of pistons contact surface. If it would not work as I expect I have just to revert the piston side to the original angle of 90 deg, and the gun will work as before. I even do not need to change the trigger pin. I see some advantages, regarding safety, with respect to original trigger pin. I can have clear indication if the trigger tooth were in its right position. If not, the trigger would be more back, because the pin and the lever are connected. Disadvantage would be more power to cock the gun. But I have may Easy Loader, so there is no problem.
 
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You need to put a lot more shots through it as the unmatched contact of sear tooth on mushroom tail will lead to increased wear with just the tip of the tooth now engaging. Basically you have reduced the sear lever closing torque by minimizing the pull offset to the pivot pin axis from the base of the sear tooth to the top of the sear tooth. The reliability has to be evaluated. Band gun owners improved trigger pull by the angular filing of sear teeth, but unreliability was a possible consequence down the track with higher wear, unless the angles were matched on both components. While it is nice to have a positive result, speargun trigger mechanisms must be reliable, especially on muzzle loaders. Although you have not changed the tooth angle, the mushroom tail on the piston is now only being held close to its shank, not over the full contact face with the tooth. While you don't want a heavy trigger pull, you do not want a "hair trigger" either where the slightest finger pressure fires the gun. Anyone else reading these posts needs to be reminded that trigger changes are not without consequences if things go wrong, so extreme caution is advised.
 
Trigger force of about 1 kg seems quite good for me, not too soft and not too hard. If it would be same on normal working pressure of 25 bar it would be very good. After that I will inspect the pistons mushroom for wear and maybe match contact surfaces.
 
Mirage with HydroDamperTomba and Pressure&Friction balanced trigger is ready for testing in sea. Silicone tubing that cowers muzzle ports is not on a picture.

 
I did a test with hydro damper in sea with my Mirage 70. It was working excellent, both water barrel and vacuum barrel with Tomba800. I recorded the sound of impact with my sound recorder under water to compare intensity of sounds: hydro damper/classic damper using water barrel/vacuum barrel. I did a recording on distance about 30 cm side/back from the muzzle.

[ame="http://youtu.be/_Vn3Rhl9hZ0"]Damper - YouTube[/ame]

 
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Tomba700 with constrictor slider for lightest weight - highest pressure - highest speed.
I tied climax 0.92 mm to mono 1.7 mm. Instead of climax, spectra 1.5 mm might be used.

 

Although I was trying to make hydro damper using muzzle without water exit holes, I think this is still better solution for free shaft. Shaft could be loader under water in any position and water would not get behind the piston. Upper picture (very similar to it) is what I already made and tested in sea. I can reuse the same muzzle for free shaft too, just changing Tomba800 adapter to TombaF800 or TombaF700.

 
Idea for a new Tomba700X. X should mean extra easy loading, extra slim, for extra pressure and speed. I used idea that I believe is similar to Airbalete microspeed slider that is also flexible in a muzzle what makes loading more smooth and easier. But contra to microspeed slider that is too heavy this Tomba slider would be very light, I believe about 2 g. I would use slider made from spectra/climax constrictor knot.

 
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Few corrections. Mass of taper ring, O-ring, ... about 2 gr

 
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Would be not the best but maybe optimal solution. Shaft should not to be modified. Loading in any position.

 
Now, you got me interested in the hydro damper as well. Remember, I still haven't shot my gun with a dry barrel kit yet, so bear with me. But I guess the need for better dampening is to be able to have less recoil and perhaps even loading gun at higher pressures while still keeping the piston safe - would that be correct?
I have been wondering a lot what happens with the tiny amount of water that I guess will be "stuck" between the o-ring and the piston? Is it an issue at all? Some of your hydro damper designs lets the water out, but as far as I can see not your latest design, right?
I noticed that in some videos, Marko lifts the gun out out of the water to empty the muzzle before loading. Do other people do that as well?
 
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