"MAVKA" pistonless speargun prototypes

  • On the “Vlanik” pistonless gun thread there was an image of two guns that looked very attractive and a search has discovered them on the www.akvalang.com website. The top gun is a 70 cm model and the lower gun is a 55 cm model. The 70 cm gun has a side-mounted line release while the 50 cm gun has a passive magnetic clip similar to the Pelengas release lever.

    VLANIK PISTONLESS PNEUMATIC SPEARGUN


    https://www.akvalang.com/forum/topic...shnevoe-ruzhe/


    Roman (Adept6), who lives in Belarus, has described the guns there, but unless you are a member you cannot see the photos and so I am reposting some of them here. The guns were created by Roman who also did the “Arma” speargun, hence the similarity in the style of the grip handle.

    VLANIK PISTONLESS PNEUMATIC SPEARGUN

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    Here are photos of the muzzle and spears used with the guns.

    mavka-pistonless-speargun-prototypes.114082

    The grip handle and barrel which has an integral shroud incorporated for buoyancy on a 22 mm diameter tank tube. Note that the trigger pivot pin is in the lower trigger finger guard frame.

    #lg=attachment53026

    The plastic trigger operates the sear lever arm in the muzzle, which is basically a single piece trigger, via a slim pull rod that runs under the tank tube to the muzzle. Note the step in the front of the spears for the sear tooth (which is of a cam type) to engage rather than an annular notch.


    The longer 70 cm gun floats after the shot, the shorter 50 cm gun is a slight sinker. A side-mounted line release is incorporated in the former gun, the latter uses a passive magnet line clip located just behind the grip handle.

    Attached Thumbnails

    The post was edited 4 times, last by popgun pete ().

  • Pistonless pneumatic spearguns are very efficient as the guns only have one seal in the muzzle which the spear shaft slides through. The spear in a sense is also the inner barrel and piston in one item. Hence this gun has the equivalent of an 8 mm diameter inner barrel and as the spear cannot have any notches in it that penetrate into the gun the retention notch is at the front of the spear.

    Usually forward latching speargun have an annular notch that weakens the spear, but here the shaft has a step with a slightly larger diameter "collar". In order to prevent air escaping from the gun with each shot a detachable spear tail cap or plug acts as a stopper in the muzzle. The sear lever is essentially a single piece trigger installed in the muzzle and operated via a thin pull rod running from grip handle to the muzzle under the tank tube, this being the most common arrangement on forward latching pneumatic spearguns which are very common in Russia and the Ukraine.

    One of most widely known pistonless spearguns is the "Vlanik" speargun which has undergone many revisions over the years and here are two of them. Not everyone likes the handles, so there are many derivatives and clones. A decade and more separates the models shown, the later gun being a floater after the shot whereas early guns are sinkers. The gun with the shoulder stock is a target shooting model, it was also available without the stock and the sights, but was still a sinker.



  • In order to prevent air escaping from the gun with each shot a detachable spear tail cap or plug acts as a stopper in the muzzle.

    I don't claim to understand this gun, but doesn't this cap essentially becomes the piston? Also what do you mean the spear is the inner barrel?


    Do you think that little step at the front of the spear makes for a reliable secure trigger?

  • I don't claim to understand this gun, but doesn't this cap essentially becomes the piston? Also what do you mean the spear is the inner barrel?


    Do you think that little step at the front of the spear makes for a reliable secure trigger?

    The tail cap and spear are the same diameter, so they represent the cross-sectional area that the internal compressed air pressure acts against. It is the pressure differential between the interior of the gun and the external environment that pushes the spear out of the gun. The flange on the spear tail cap does nothing for propulsion as gun internal pressure operates on both sides of the flange and the effects cancel out, so you can ignore that flange’s annular cross-sectional area having any effect. A conventional pneumatic speargun piston is pushed along the barrel by the compressed air working against the piston cross-sectional area of (13/2)^2 x pi = 132.7 square mm.


    In a pistonless speargun shooting an 8 mm diameter spear the compressed air pressure is working against a cross-sectional area of (8/2)^2 x pi = 50.3 square mm, hence the force propelling the spear at a similar gun internal pressure is much less. For that reason pistonless guns need to operate with higher internal pressures to achieve the same level of propulsive force. On the plus side there is only one seal providing any friction on the moving spear, whereas in a conventional pneumatic gun you often have two seals on the piston that provide more frictional losses, plus the piston body can rub on the barrel interior, however the gun can produce reasonable performance at 20 to 25 atm because the piston diameter is so large and thus its cross-sectional area is large. Some guns have 14 mm diameter pistons and their cross-sectional area is (14/2) ^2 x pi = 153.9 square mm, hence they offer even more force on the piston to drive it and the spear from the gun. A quick calculation is to look at the ratio of the diameters squared to determine the advantage with barrel diameter increases as the factor of pi cancels out, as does the factor of 0.5 (radius equals diameter/2 or diameter x 0.5).


    The small steps do the job in retaining the spear, but not being lubricated as the sear tooth to piston mushroom head flange contact faces are inside a conventional pneumatic gun they are more likely to wear out the tooth and the edge of the shaft notch, but it will take some time and a lot of use to do so. The smaller the actual contact area then the more rapid the wear. Single-piece triggers require a 90 degree face interaction to the direction of propulsion, any slope and they may not hold as a force component develops which rolls the tooth down without you pulling the trigger and sometimes only friction hold the spear back which is not very reliable or safe.


    That said with high quality steel in both sear tooth and spears the gun longevity can be extended to the point where it will not be a problem and as spears can be lost it is really only the sear tooth that has to last. Vlanik guns have functioned for decades without problems, so a pistonless gun is not a deal breaker, but like all spearguns you need to carry out inspections and regular maintenance.

    The post was edited 3 times, last by popgun pete ().

  • More information on the "Mavka" pistonless speargun can be found here.

    http://garpun.spb.ru/forum/viewtopic.php?t=1147


    The 70 cm "Mavka" gun with reel fitted (Pelengas)

    Mavka gun with reel.jpg

    "Mavka" trigger pull rod, bifurcated sear lever arm, trigger biasing spring and sear which is the cylindrical element with the cutout that releases the spear when rotated by pulling the trigger.

    Mavka sear and muzzle lever.jpg
    This combined photo shows how the biasing spring is fitted onto the trigger pull rod.

    Mavka pull frod spring.jpg

    The post was edited 1 time, last by popgun pete: Added photos from www.garpun.spb.ru website ().

  • Muzzle details including line wrapping detail of muzzle front line hook. Image below shows inverted muzzle with detail of trigger pull rod connection to swinging sear lever arm which functions as a single piece trigger. Note the biasing spring which pushes the sear lever arm forwards after you have pulled and then released the trigger. From the comments on the Russian and Ukrainian forums it seems that you can insert the spear into the "Makva" gun without having to pull the trigger, something that often needs to be done on forward latching guns to ease the spear tail past the sear tooth.


    Mavka gun pull rod biasing spring.jpg

    Line wraps on front line hook in lateral view of "Mavka" muzzle nose.

    Mavka gun line wraps.jpg

    Line wraps on cocked ready to shoot "Mavka" pistonless gun, note that the gun is shown inverted here.

    Mavka muzzle with spear.jpg

  • Pistonless guns have the potential to swallow water, maybe only a tiny amount, if the water in the front cavity of the spear tail cap after the shot is not completely squeezed out when the tang of the shaft is pushed into it during reloading of the spear shaft. Properly machined the spear tail cap will butt smoothly with the shaft body so that the join in the shaft that passes through the muzzle seal will not break the seal or have any water inside the almost microscopic gap, but there may be some water in the cavity as butting two surfaces with absolutely no gaps is very difficult both internally and externally, it will usually be one or the other. If the water is in the tail cap cavity then it is important that it stays there and that the cap does not fall off inside the gun.


    The post was edited 1 time, last by popgun pete: added a photo ().

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