Taimen - Russian pneumovacuum speargun

[tromic]

It seems to me that vacuum cuffs annular body through thrust washer works together with shock absorber as an larger (more efficient) shock absorber?

 

[popgun pete]

It seems to me that vacuum cuffs annular body through thrust washer works together with shock absorber as an larger (more efficient) shock absorber?

Yes, this fact was mentioned much earlier in the thread, near the beginning (post #32). Note the small movement compliance step on the thrust washer, you can also see it in the photos.

 

[tromic]

Right, I found it: "Close study of the images reveals how the gun is assembled; shock absorption is undertaken by both a small muzzle damper with rubber ring in conjunction with the rubber vacuum sealing cuff and the polyurethane bush on the front of the sliding piston."

 

[popgun pete]

Replacing the vacuum cuff without depressurizing the gun first required the vacuum cuff to be separated from the shock absorber, so the cuff will not be used for shock absorption in the 2-part hub as it was in the original hub. The 2-part hub has a longer body, so there is some space available to add more damping material in the rear section of the hub if it was required. Field testing of the new hubs is underway, but I don't know when they are scheduled for production as the standard fitment, or if that will ever happen as the 2-part hub may just become an option.

 

[popgun pete]

I have found out why the inner barrel comes out with the muzzle or front hub when the latter is unscrewed from the depressurized gun. When you initially assemble the front hub and tighten the annular nut, which has both inner and outer screw threads, in order to compress the vacuum cuff periphery and fully seal it into its centralizing seat in the hub you also trap the shock absorber body in the short cylindrical recess in the front end of the annular nut that allows the shock absorber body to move back and forth slightly. However when you screw the inner barrel into the annular nut it can screw in somewhat further than the length of the inner screw thread in the annular nut and then press the shock absorber body forwards, thereby partially loading up the shock absorber damper "O" ring and the vacuum cuff's periphery. This compression of the two rubber components increases the friction on the annular nut to inner barrel connecting threads, the same as if a spring washer was being used, so that turning the front hub also turns the inner barrel and that is why they both come out of the gun as a single unit. I realized this when I found that the annular nut on its own screws on and off the inner barrel thread very easily, so something else had to be giving it a tighter grip when everything was assembled.

 

[popgun pete]

Here is a possibility for using now longer front hub section to increase damping on shock absorber body by reversing it and adding two more "O" rings. The stainless steel shock absorber body would need reduction in existing front end OD to fit inside inner barrel bore as right now it is slightly too big to serve as the rear end, despite its appearance as being the same diameter on the diagram. A bonus is that working course of the piston would be slightly increased as can be seen on the modified company drawing.

 

[popgun pete]

I notice that a large number of additional people are now reading this thread, over a thousand more in recent weeks; was 8,300 views, now 9,450, but no one is saying anything! I would have expected a long term "Taimen" user to chime in by now.

 

[foxfish]

We are all waiting with baited breath Pete!

 

[nordseal]

Nice gan for fresh water.

 

[cece]

like it . did you try it?

 

[nordseal]

like it . did you try it?

Yes. So so.

 

[popgun pete]

Here is the "Taimen" now rigged with the new 2-part hub muzzle and with a 2.0 mm shooting line replacing the standard 1.4 mm "Taimen" white line. I ordered this larger diameter line with the gun and received a "Taimen" bungee to go with it (the bungee was their recommendation) just in case the thinner white stuff did not survive long on our rocks. That standard white line is stretchy as it is a tightly woven type and has a springy feel to it, so you don't really need to use a bungee with it, but the black and white cord seems much less yielding, hence the bungee.

When I swapped the muzzles over the black plastic rotating ring, front line wrap hook was pulled off the tank, but it was a very tight fit on there, so it looks like it is no longer intended to swivel around the tank, in fact I had a big job dragging it off the nose end of the tank without breaking it. Once I put the black plastic ring back on it was too hard to push the ring right over the necked down front end of the tank, so now it sits on the rear of the new and longer front hub about which it can just about swivel as the outer knurled grip on that alloy hub section makes the plastic ring a snug fit. The subsequent forward repositioning of the front wrap hook added an extra 2 cm to the line wrap distance per side, hence to achieve the desired maximum shooting range of 3 metres I decided on installing 4 line wraps on the gun, which meant that I needed a longer line than the standard stuff which only seems to come in 3.1 metre lengths (according to the user handbook) to complete the necessary wraps. The black and white 2.0 mm diameter line was 5 metres long, so it must be some other type of cord. I cut it off to the required length which works out at just over 3.4 metres, including the bungee.

You may notice that the name stickers no longer sit on the side of the gun, that is because the replacement muzzle's thread started at a different position, so the grip handle ends up at a different orientation with everything tighten up. To twist the tank while in place on the gun you would need to be King Kong, so I will mark the hub positions and correct it next time I pull the gun apart. Once you push the muzzle into the tank that fixes the tank orientation, but you don't know how many turns it takes to screw the rear housing right up. I had two attempts and this was about as close as I could get to lining the stickers up without pushing the muzzle out again (I needed a soft-faced hammer to drive it back into the tank, it is a tight fit).

In the photos the line slide is locked in the muzzle as I did not fancy taking any photos with the gun cocked with the spear and you have to lean surprisingly hard on the hand pump to pump the gun up, by the time I got to 115 strokes I was looking for a thick glove, while 150 strokes is the allowable maximum for this model length and barrel diameter. Having already let all the air out twice I was not going to do it again just to line up the stickers! Of course the muzzle itself has no actual "top", but that position is determined with the gun tightened up to squeeze the front and rear ends of the gun tightly against each end of the air tank. The plastic cereal box shown here makes a convenient post-dive gun soak tub, when full of water the guns stay put unless they are too long and overbalance the tub, then you need a convenient wall to prop one end of the gun against. Swap ends to do the whole gun, you can just tip water over the mid-section when you empty the tub.

A shooting and handling report will come later when conditions better suit the "Taimen" (i.e. poor viz, lots of drifting bubble weed and piles of busted off kelp), otherwise I will still keep using my longer pneumatic guns.

 

[Jegwan]

Thanks for the update. The gun looks really sweet and "hightec" with the new to part muzzle.

Have the manufacture or you changed the screws in the handle to SS?

Jégwan

 

[popgun pete]

Thanks for the update. The gun looks really sweet and "hightec" with the new to part muzzle.

Have the manufacture or you changed the screws in the handle to SS?

Jégwan

The screws and nuts are stainless steel as supplied, it appears that they have been made from that material for some time now. A number of updates on the "Taimen" have been in place for some time now which are not reflected by that parts diagram I created (their parts list photos had not been changed and that is what I had used to do my diagram). For example there is a rubber ring between the plastic handle and the rear metal housing to prevent too much stress being placed on the handle when tightening up the inlet valve housing that clamps the gun body to the handle. That rubber ring gives you a bit of feedback as you tighten the inlet valve housing, being a progressive tensioning rather than all or nothing.

 

[popgun pete]

An updated parts diagram, but not showing the new grip handle shape or the "universal" version without the thumb support projection for left or right handed users. Note the extra "O" rings on the front hub and rear housing components and the new and slightly longer piston.

 

[popgun pete]

Now with the new handle, smaller image next to it shows the "universal" version.

 

[popgun pete]

What I think happens as the piston slams into the shock absorber and the spear departs. Slight vacuum occurs behind the spear tail as space opens up in the muzzle interior (little white dots depict the vacuum if you look close enough at the space behind the spear tail). Water can push outwards from behind the vacuum seal, it was in there when the spear was introduced into the muzzle and before pushing on the shaft commenced.

 

[tromic]

What you are talking about is similar to what I described here:
http://forums.deeperblue.com/threads/tomba-all-in-one-barrel-sealing.81791/page-36#post-903872

 

[popgun pete]

The partial vacuum only lasts until the spear tail clears the lip of the vacuum seal, then the small side ports relieve the vacuum for the remainder of the spear's travel out of the muzzle. They let water out and in as the spear tail enters and leaves the muzzle, in fact that is what they are there for.

 

[popgun pete]

The "Taimen" has no metal springs, it uses rubber elements for any biasing function of its moving parts. Note that the sliding column type sear is biased by the air pressure differential existing between the interior and exterior of the gun, one of the most intriguing aspects of this innovative design.

I have been thinking about the rubber column biasing spring located in the trigger finger guard frame, it gets pinched as the line release lever turns to let the shooting line escape at its maximum allowable rotation. For the line release lever to rotate much further it almost needs to shear the rubber column in two (a piece of rubber "O" ring), but I have been thinking that if the rubber column was used instead as a compression spring then it may allow more rotation of the line release lever and decrease the stress on the line release system arising from pinching the rubber column which now functions like a leaf spring. A diagram is attached, the new handle may have more space available in the trigger finger guard upper frame, so I have simulated it here as I do not have a photo of the interior of the new handle. The new "cam follower" style parts may be slightly curved, not straight as shown here, so that they follow the curve of the tunnel in the finger guard frame.