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Taimen - Russian pneumovacuum speargun

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.
Well as luck would have it I just found the "Cyrano" page, it is for the "Cyrano 110" model. "Volume initial of tank" is 986.96 cc and "volume final of tank" is 896.68 cc. The swept barrel volume is 90.28 cc and the variation of volume is 9%, so the longest "Cyrano" has a CR of 1.09 (big tank, small bore). I can guarantee that CR number gets larger as the gun gets progressively shorter as losing 17 cm to the plastic non-pressurized snout on a 110 cm gun is relatively little, but on a gun half that length (55 cm) it is a lot! Incidentally 17 cm is the spacing between the inner barrel groove "O" rings with the plastic circlips sitting directly behind them, on a "Cyrano" the pressure bulkhead seals on the second "O" ring, on the "Spark/Stealth/Sten 11" it seals on the front "O" ring, in fact those latter guns often have the groove in the inner barrel for the second "O" ring and circlip, but of course it is left empty.
 
Initially I greased the connecting screw thread between the two sections of the front hub to keep any saltwater out of that screw thread, but grease traces in the muzzle cutouts or large transverse slot (made for the special tool to engage when assembling the hub on the gun) were a magnet for any fine particles entering the muzzle. So I removed all the grease completely and decided that the best way to get saltwater that had penetrated during the dive out of this screw thread was to disassemble the front hub section during cleaning. That means I can also easily inspect the vacuum cuff, in fact I do not replace it in the gun until I next intend to go diving. This job only takes a few minutes to perform, you can unscrew the front section of the hub by hand, so no tools are required.

How saltwater gets into the connecting screw thread is via those cutouts or slots. They create a gap on each side behind the vacuum cuff which sits in front of them on a thin plastic washer to stop the cuff collapsing backwards where it sits over the slots. The schematic of the hub does not show these slots, but you can see them in the hub photo where I have indicated the pathway for water entering the screw threaded section by blue lines and some arrows.
 
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A modification has been announced for the 2-part front hub which will now contain a polyurethane washer in the formerly unused space in the rear section of the hub which was discussed here earlier as being underutilized.
 
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This diagram illustrates how water can be trapped, unlike pistons that have a venting hole in the side of the piston's forward section which allows an escape path. The old Mares metal body piston had a small hole which prevented hydraulic lock on the insertion of the tapered spear tail, however it also let water out as the gun dried out after use and after being washed in freshwater.
 
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Revised cleaning diagram with new polyurethane bush incorporated in 2-part muzzle's rear section. The cleaning method remains exactly the same as before.
 
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Design work benefits from cross-pollination of ideas, that is how this modification evolved. A simplification of the designs shown earlier, but enabling use of existing stock of gun components.
 
Magnetic control throttle for proposed "PVRM-RX". Only an idea at the moment, but more design work required on power operating switch which varies magnetic poles to spin the ported throttle cylinder.
 
Updated parts diagram now shows the moulded hard polyurethane float insert that fits very snugly into the lower grip section of the rear handle. This buoyancy element and the size of the handle itself (determined by its long raked length) is instrumental in floating the gun after spear discharge, especially with the shorter barrel length models.
 
The new 2-part front hub or muzzle is now on sale, so I have amended the parts diagram accordingly.
 
As the new 2-part hub is longer than the single-piece hub the fitting of it makes the gun a tight fit in its carry case as the line slide holder on the muzzle nose was already close to the case zipper with the original muzzle set-up. I have suggested a removable plastic cap that can replace the front section of the hub with the latter stored separately in the zipper-closed storage pocket in the carry case. A composite image demonstrates the concept (borrowed from similar caps on DIN fitting scuba regulator first stages).
 
If you reassemble a "Taimen" yourself then you need to pay attention to aligning the metal cover plate that goes over the sliding column type sear as the "D" shaped opening in the cover plate that the small pin on the bottom pokes through has to be such that the flat is aligned fore and aft on the gun, as well as being on the correct side or you will have the sear installed in the gun the wrong way around! It is very easy to do correctly as you first push the piston right back in the rear housing (which is "bare", as in not being fitted with anything else at this stage and that includes the inner barrel) to properly align the already installed sear column and then attach the flat cover plate and add the two small fixing screws, just nipping them up as they don't need to be very tight. These screw threads are very small and you don't want to strip them by being ham-fisted. The attached diagram explains what I am talking about.

The gun disassembly video actually demonstrates this cover plate assembly method, but I bet some people may fail to absorb just what they are seeing, especially non-Russian speakers.
 
For the spearfisherman who can afford two "Taimen" guns there is now a nice carry case to transport them both in with their respective spears clustered together in a bundle held in place at the top when carrying the case. A 40 cm gun for the reed thicket (or silt-laden, underwater soup) and a 70 cm gun for conditions where you have a lot more viz. Detachable speartips and other small items are carried in the zipper-closed storage pocket on the upper right hand side as seen here so that they don't rattle around and trash the surface finish on your guns. I jam metal chair leg rubber feet or end caps onto my spear tips to stop them damaging other items and each other, but years ago you could use wine bottle corks for this job. Plastic "corks" have taken over in many places from the genuine article, or composite corks that crumble and are of limited use. Small rectangular, clear plastic, press seal kitchen containers are handy for confining detachable speartips, just don't use the ones from your kitchen or you will be in trouble!
http://apox.ru/forum/topic/12575-novinka-chehol-dlja-ruzhei-taimen/
 
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As many of the "O" rings for the "Taimen" are of a similar size, I have suggested that a template be supplied with the kits of replacement seals or incorporated into the user handbook, such as on the rear cover page which is largely underutilized. A purely illustrative representation is shown here (LHS) which has been achieved by manipulating the small images in the "Taimen" handbook (RHS) and using some thumbnails from an earlier parts list, but a 1:1 sized image of each "O" ring and seal/washer in silhouette is all that is required. Mares supply such a chart/seal template with their own pneumatic speargun seal replacement kits.
 
As I have posted this info on the self-aligning seat for the vacuum cuff in the "Taimen" muzzle elsewhere I decided to add it here as well for any future reference.
 
Pete, I think that the slider have the main centering role in Taimen spear gun. O-ring that holds the slider in place all the time until the shaft tail leave the muzzle helps that function of the slider. Without that O-ring slider might left the gun too early and there would be no centering in the most critical time.

In Tomba vacuum kit the only one O-ring on the shaft serves for maintaining vacuum and for holding in place the cone ring for centering the shaft. The shaft is in center with tolerances +-0.05 mm, all the time during shooting. I suppose similar tolerances are in case of Taimen too.
 
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Actually this seal alignment on the shaft was part of Mikhail Kuznetsov's design aim for his "Taimen" pneumo-vacuum speargun, he only eliminated the need for it by providing the self-centering seat for the vacuum cuff in the later models. I am just reporting on his work, I would have mentioned it earlier, but had no reason to do so until the seal damage was reported on the similar, but not identical, system used in the "Vuoto-Air" speargun. (Refer thread http://forums.deeperblue.com/threads/testing-the-salvimar-pneumatics.100351/).
 
Here is how the vacuum cuff was centralized to the muzzle (front hub) and thus the barrel's inner bore by building the forward assembly up on the spear shaft. The photos are from the disassembly-assembly video of the gun in one of its earlier forms. The upper left photo is using the special tool for the gun, the vacuum cuff now sits on a rod projection that stands in for the shaft, but by this time the gun has self-aligning seats in the front hub. The tightening of the annular nut locks the vacuum cuff into position in the front hub. In the 2-part hub the annular nut no longer performs this function as the vacuum cuff is moved into the detachable front section of the hub.
 
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Something that I have not previously mentioned is the "Taimen" has a painted outer tank or receiver. You can see in the frame extracted from the disassembly-assembly video that it was once a different colour with a glossy finish, but is now black and has a slightly textured, semi-gloss finish. The front line wrap hook ring or "horn" was previously moulded from polypropylene and to provide a friction element for its controlled rotation to different orientations on the tank (in order to remove slack from the shooting line wraps) a separate stop ring (part no. 66) was mounted directly behind it. Now that the front line wrap hook ring is moulded from a polyamide plastic, which is less susceptible to stretch than polypropylene, it can stick at different orientations on the black painted tanks and hence the stop ring behind it has been omitted. However I found that the front line wrap hook ring was hard to remove on my gun when I replaced the front hub with the new 2-part hub, so I found a way to remove the ring without risking it being damaged by using a drum pouring spout thread size adaptor that was just the right size to slip over the rear end of the tank. The rear handle had already been removed (power regulator guns need that removed as well) and the adaptor then provided a surface to brace against as I delivered a series of light blows to the end of the muzzle with a soft-faced hammer. As can be seen in the photos the only modification is to cut a notch in the adaptor to accommodate the "sighting" peg so that the opposing surfaces fully butt up against each other.
 
Something else to be aware of is the "Taimen" piston can no longer be inserted at the front end of the inner barrel tube, you have to push it in from the rear end of the inner barrel instead. This is not really a problem as when reassembling the gun the rear housing containing the sear mechanism screws on last, so that is when you should fit the piston, pour some oil in and then close the gun with respect to sealing up the outer tank. The reason the piston will not go in from the front end is that a short section of the inner barrel tube is now necked down immediately behind the screw thread on the inner barrel nose creating what looks like a slightly depressed band when looking from the outside of the inner barrel. On the inside of the inner barrel this band represents a bump that constricts the bore slightly at that location which corresponds to where the front end of the piston sits with the gun discharged. The purpose of this constriction is to confine the piston's polyurethane bush from spreading radially under constant internal gun pressure and thus taking a "set" that would produce a flange or belled-out shape on the polyurethane nose of the piston by holding it against a diameter that is slightly less than the inner barrel bore in order to prevent this from happening. Older guns don't have this necked down constriction, but as the "Taimen" muzzle when removed takes the inner barrel with it then it is logical to push the piston (with the spear) out the back end of the inner barrel anyway. The design and construction of the "Taimen" gun is based on this order of assembly, if you think you know better then you will be in for a pile of problems all of your own making.
 
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When using the "Taimen" special tool to snug up the inlet valve body that effectively clamps the gun's cylindrical components into the rear plastic clamshell handgrip assembly I found that the two opposing lugs on the end of the tool fouled the circular rear access opening in the handle. You can push the tool through this opening by the lugs forcing the handle halves apart momentarily as the top rear connecting screw in the handle is removed, it only goes back in after the rear cover or bung has been replaced to close up the inlet valve's threaded well (used for the handpump connection). I decided to carefully slice a tiny amount of plastic from the lug on each side until the tool would pass through the handle rear opening without catching. This worked very well and the modification is seen in the attached photo. The dimensions shown in brackets are the "nominal" sizes, the other dimensions are as measured with vernier calipers. The special tool is moulded from a glass-reinforced polyamide, so a thin box cutter blade or similar will do the job or you could file the material off. Slicing produced a clean cut edge as with the "Taimen" tool resting against a work table the excess material was carefully pared away with a reciprocating motion of the blade which possessed an extremely sharp and thin cutting edge. I removed material until the tool just made it through the opening without any obstruction. The benefit of performing this modification is that once you have the inlet valve body sufficiently tightened you can then remove the tool without it catching again on the handle rear opening and can therefore concentrate more on getting the tension right without over-stressing the plastic handle. The diameter of the special tool where you grip onto it for this task is intended to limit the torque that can be applied, although those with stronger hands than brains should think twice before mindlessly twisting the tool with every fibre of their being as such over-tightening is completely unnecessary.
 
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