Taimen - Russian pneumovacuum speargun

[popgun pete]

After looking at the relative proportions of the spear tails I think that this is a better representation. The increase in tail length is about the length of the muzzle entrance where the muzzle bore diameter forms a guide without the slider being locked into the holder first.

 

[popgun pete]

Here is an update of the “Taimen” parts diagram with the now standard two-part hub or muzzle. I don’t have the size for the new “O” ring that sits on the base of the threaded boss of the rear section of the muzzle (hence the ?) and the part numbers shown in bold are no longer current as the components are no longer listed by number on the “Taimen” Company’s spare parts pages. Also shown are the thin plastic washer that sits behind the muzzle vacuum seal or cuff (which covers the transverse slot made for a dismantling or tightening tool) and the polyurethane shock absorber bush (shown in orange here) which also serves as a seal to hopefully keep water out of the threads of the annular nut (part 10). At one time a “Zedex” plastic annular nut was evaluated, but was on the verge of not being strong enough if the gun was pumped up to the maximum, so the annular nut is back to being made from alloy again. The redundant plastic nut I now use to keep the vacuum cuff and thin plastic washer in the front section of the hub when the front is unscrewed from the gun, especially as with the front muzzle section fitted the gun is now too long for its carry bag. The front section now lives in the pocket of the carry bag, or I store it separately for security purposes so that the gun is useless to potential thieves.

 

[tromic]

Pete is it easy or requires some force to disengage the slider from the PU shaft tail end after shoot?
What is the weight of aluminum slider?

 

[popgun pete]

Pete is it easy or requires some force to disengage the slider from the PU shaft tail end after shoot?
What is the weight of aluminum slider?

The slider weighs about 2.5 grams as my electronic kitchen scale shows either 2 or 3 grams on repeat measurements, the majority of readings being a 2 rather than a 3.

The slider has to be jerked free by using the shooting line in a straight pull along the shaft towards the tip. To immobilize the shaft you wrap your fingers around the floppers to provide a hold as otherwise you cannot grip the slippery shaft with your dive gloves when underwater. The slider pulls free relatively easily when doing this provided you give a strong pull with the shooting line gathered up in a couple of turns around your free hand. Sand needs to be kept out of the rear hollow in the slider, so I run the slider up and down on the shaft to eliminate any particles after it has hit the bottom and then wipe the shaft tail with my hand by twisting it between my gloved fingers. Fish slime on my gloves tends to take any sand away rather than deposit it on the polyurethane bush, but I swish the shaft around in the water like a wand in order to dislodge anything before I insert the shaft tail in the muzzle prior to the next reloading effort.

 

[tromic]

Thanks! I had similar experience while I was testing one of my stainless steel sliders having 30 deg cone entrance for PU shaft tail end.
Is there one or two pieces of PU on the shaft tail end? On image it seems to be two?
I suppose the OD of the slider body is 9 mm for 7 mm shaft?

 

[popgun pete]

The polyurethane bush is in one-piece and appears to be moulded directly onto the shaft and we know it sits in two annular grooves on the shaft from the company's schematic drawings. However I cannot see a parting line on the bush where a split die would have opened up to release it once the polyurethane had set.

The 7 mm shaft slider body is 9.5 mm OD at the rear end and about 9.6 mm OD where the side lug for the shooting line eye is located, the slider being either turned/milled down from a larger piece of metal to form the lug as it all appears to be in one-piece. I have not really studied the machining marks on it closely to check out how the slider was made, but it may have been formed up in some other way as the mid-section does not look to have obvious machining marks before it was bored out and turned on a lathe at the front and rear ends.

P.S. I have looked at it with a magnifying lens and now think that the slider is made using a keyhole shaped alloy extrusion, much like a cylinder with a bar on one side that is a long rectangular cross-section rib. The rib is machined away leaving the lug remaining only in the central section, the ends being turned down as a cylinder at the rear and the front as a hollow nose cone for a streamlined shape once the slider is drilled out longitudinally. There are file marks on the lug to clean off any burrs on the straight edges of its angular side profile.

 

[popgun pete]

A long term personal project has been to look at ways of eliminating annular nut (part 10) which was essential to a fully sealed muzzle/hub with no exposed outer joints in the original gun. It was a very compact solution and a masterpiece of design integration with as few parts as possible combining in a very small space. Now with the latest removable front section it is possible to look at installing all components from the front and not the rear of the muzzle as before as the shock absorption anvil and vacuum cuff are now completely separated.

Originally the vacuum cuff was also a shock absorption bush on its outer periphery, but now this duty is undertaken by a polyurethane bush in addition to the similar material bush on the nose of the piston in the latest version of the gun. This latest exercise looks at a possible further development within the dimensions of the current hub and maintaining the low weight required for floating after spear discharge of the gun.

 

[popgun pete]

Strength and length of muzzle screw threads needs to be considered, as shown on this schematic diagram, when muzzle components face either unloaded or cocked to shoot pressures inside the gun.

 

[popgun pete]

Cleaning method diagram updated to include what was written in text, but not actually shown. Avoid a future appointment with pliers and a gas torch and assorted heavy duty gripping devices if you dive in saltwater and then leave your gun unattended to look after itself!

Note that the gun is never cocked or latched in these cleaning operations, all the operator is doing is working the piston up and down in the inner barrel like pushing on a spring. The piston is pushed in only far enough for the water sitting in the muzzle to run down into the barrel, probably about a third of the travel and possibly less than that. Step 4 is where the gun is inverted and pushed down onto the spear which is stuck into a drilled hole in a wooden block thus allowing the piston to be backed off the shock absorber anvil far enough that the water surrounding the piston nose can escape as otherwise it will be trapped there. Pistons in modern times don't have a breather hole in the side of the nose section which allows any trapped water to gradually dry out.

 

[popgun pete]

The solution to controlling muzzle corrosion suddenly occurred to me while reflecting on my last post when I awoke this morning. You can prevent the galvanic action which creates corrosion by either totally excluding water completely or allowing the area to be flushed out, or at least a slow transfer process where osmotic action dilutes saltwater in contact with freshwater. Now Mikhail Kuznetsov tried to exclude water by using the “O” ring on the damper or shock absorber body which does prevent water coming in via the front end, that is what that “O” ring is there for, but it does not stop water coming in from the rear end which is provided by the residual water sitting in the muzzle “accommodation space”.

I had suggested a thin rubber washer on the rear side of the shock absorber anvil’s flange to block water accessing the muzzle thread, but it now occurs to me that a far easier solution is to allow water to more readily access the area. To do that one needs to drill a ring of tiny holes in the shock absorber body which will allow freshwater to interact and dilute any saltwater when the gun is soaked in a tub, in fact the gun will need soaking after saltwater use anyway. Normally water cannot get in this area during gun soaking because the piston nose clamps the shock absorber anvil and seals the area off. A diagram showing this modification is attached.

This ring of additional holes is the counterpart to the breather hole in the piston nose mentioned above, but the shock absorber anvil being reversed in a "Taimen" makes it easier to do because it has no rubber sleeve covering it as is the case in a standard pneumatic gun of the Italian type such as the Mares "Sten".

 

[popgun pete]

Screw thread strength diagram as above, but now for the original muzzle design.

 

[popgun pete]

After looking at the relative proportions of the spear tails I think that this is a better representation. The increase in tail length is about the length of the muzzle entrance where the muzzle bore diameter forms a guide without the slider being locked into the holder first.
View attachment 42180

Another possibility is the aim of the polyurethane bush being moved closer to the vacuum cuff (and thus a longer tail) is to break the suction which may develop behind the departing spear tail. This idea was canvassed when looking at a two hardness bush, the softer inner providing shock absorption and the harder outer more effectively sealing the front rim of the annular nut. This was rejected as the bush would be "gold plated" in terms of the expense involved and gains may not be worth all the effort required to do it rather than a simple bush of one type of polyurethane material.

 

[popgun pete]

Method for transporting “Taimen” gun when stripped of its front muzzle/hub section and rear plastic handle so that the assembly is protected from contaminating materials. As this is “PVR” model the power regulator control lever has been unscrewed in order to remove the clamshell rear handle. Extra materials required are an old 35 mm film canister drilled with two small holes just below the rim of the canister for passing a cord, in this case the “Taimen” shooting line, across a diameter. Presence of the “half circle” of cord inside the canister holds the canister on the front of barrel with a slight interference fit. Rear cap is an unmodified WD40 spray can cap that already has notches on top (for a small diameter spray pipe) which are suitable for cord wrapping. Method of line wrapping shown parallels that used for protective end cap transport of the “Taimen” spears and line slides.

 

[popgun pete]

This diagram shows design principles behind original "Taimen" muzzle. Only problem is saltwater use in high salinity seas can create small galvanic cell in region of annular nut screw threads. No problem occurs if gun is methodically cleaned by user who understands the dynamics of the muzzle and takes precautions based on common sense.

 

[popgun pete]

Drag effects of the sealing “O” ring used to plug the gap between the rotating throttle disk and the inner barrel have proven to be a binding problem on the disk rotation in experiments. In this revised embodiment the sealing is changed from blocking off the annular gaps around the inner barrel tube to plugging the actual by-pass holes by using a ball form to block the bore entrance in each of the 8 holes. The magnetic controller is now a sleeve on the outer tank which is rotated after being slid forwards to pull the balls free and then moved back again in a type of step function to place the balls on the divisions between the airflow bore holes rather than in the holes. The former position is low power, latter position is high power with other possibilities being independent ball positioning rather than all 8 balls acting as one. As before detail engineering is left to the experts!

 

[popgun pete]

Source of “Magnetic Power Regulator” idea is this magnetic switch used on “Wet Beacon”/”Wet Finder” pinger system used for underwater relocation of a deep pre-marked object, e.g. a sunken wreck, some months after the sonar beacon was installed by deep anchoring at the dive site. Magnet buried inside encircling plastic sleeve switches on a magnetic reed switch buried deep inside the main component bodies to either switch on the “pinger” or change search mode on the “finder” as the beacon location is closed in on during successive sweeps to narrow down the beam detection. GPS location has made this system completely redundant, but the technology was typical of the “new” electronic dive era emerging in the seventies and eighties. Despite me spending a fortune importing it the device never worked that well and fortunately I recovered the “Wet Beacon” before it was lost to me forever, that is why it still looks in good order today. Single 9 volt batteries were its chief weakness; no electrical power, no signal! I had to rip out the magnet and reinstall it before it even worked at all, so much for QA.

 

[popgun pete]

I have noted some people wanting to know what to use when pressing open the "Taimen" inlet valve stem as it is plastic. Normally one would use something like a wooden toothpick as metal ball inlet valves are common, but the “Taimen” inlet valve stem is a thick cylinder relative to other "sewing pin" diameter sized stems, so one needs something of a similar diameter and flat on the contact end to evenly push the plastic stem inwards. I found the ideal tool was this “charging pin” from an old Cressi-Sub spring gun as each press downwards is easily controlled due to the loop shape on the top of the “charging pin” which allows a pressing action with your thumb on top of the looped end. Easily made up out of a thin diameter aluminium rod as strength is not a requirement here if you don’t want to make one from steel.

 

[popgun pete]

"Taimen" owners when reassembling their guns need to place the sear cover plate the correct way around on their gun or the sear column will be facing in the opposite direction and will not operate! Also the "D" shaped cut-out in the duralium cover plate must not be damaged or corroded, however the titanium pin creates a polarized condition where any galvanic action is precluded. This is the reason for both a titanium sear column and titanium piston, that piston material offering the lightest weight and strength. It would not be practical to insert a titanium pin in a stainless steel sear column as both pin and sear column must be one solid component. A screw connection here is not a proposition as the screw required would be miniscule.

 

[popgun pete]

I put both these diagrams up on the www.apox.ru dedicated "Taimen" section after a try at Russian translation, but even rechecking by converting everything back to English again is no guarantee that it says what you intended. No response or criticisms yet, but perhaps the approaching festive season has everyone concentrating on other important matters such as securing sufficient supplies of food and drinks.

 

[popgun pete]

I am ordering a "universal handle" for my Taimen PVRM 600 as that handle is slightly smaller where your middle and ring fingers wrap around the grip handle. Right now the existing "old shape" handle keeps those finger tips on an outward sloping surface where they cannot create an opposing grip onto the heel of your thumb and lower palm which then allows the gun to twist slightly in your hands when the gun shoots. Those with bigger hands and longer fingers will have no trouble, but my hand is just not big enough, so I shoot two handed with my left hand cupping the butt of the raked angle handgrip. The new right hand grip also has this reduced girth dimension, but the universal handle (as in either left or right hand) has no thumb ridge which means that I can switch to left-handed shooting on occasions when my right hand has a firm grip on something in order for me to hold station in the water.