GSD pneumatic spearguns

[popgun pete]

GSD produced some stylish and innovative pneumatic spearguns in the seventies and eighties, but what happened to the company? Their last effort was the green bodied "Punto" that had a detachable air reservoir so that you could swap the rear handle around on 3 separate gun bodies of different lengths while each unit was still pressurized. The guns were sold with a very large carry case moulded in black plastic that held the grip handle, the three barrels, their respective spears and the various accessories. Just imagine taking that lot through airport security on an overseas dive vacation these days, assuming that you ever got out of the place!

The "Punto", which I have previously mentioned on another thread, is also unusual as the sear uses metal balls to lock the piston when the gun is cocked, I think that there are 3 of them, although I have never actually checked. Ball type sear systems are not common, one problem is that the balls can escape and roll around inside the gun if something does not function in exactly the correct sequence, necessitating a dismantling job. At least with the "Punto" you had two other barrels to keep you going if one was out of action. That said, I have never heard of anyone having this problem with a "Punto" mainly because few divers seemed to own them. Earlier GSD models used a trigger valve system, pulling the trigger opened a plug type valve that blocked the inner barrel at the rear end. This plug functioned as a non-return valve during muzzle loading of the spear, but when cranked open it allowed the pent up air to drive the piston and spear along the inner barrel. All GSD models had a collet type set of jaws on the front of the nylon piston which held a small ball mounted on the spear tail, the rubber shock absorber being mounted on the piston body rather than in the muzzle itself. It was said that the GSD spearguns could be fired in the air due to the braking action of the pistons as the jaws expanded at the end of the inner barrel travel, but as speargun accidents are usually big ones it is not something to be recommended!

 

[popgun pete]

I was just checking out some past posts when I found this one on the GSD “Punto”. To complete the story I am now adding the patent diagrams for the ball sear system and the variable power muzzle that increases hydrobraking for a “low power” shot. Not a system I would think as handy as flipping a lever as you have to reach forwards to the muzzle to twist it and close off the muzzle relief ports.

 

[popgun pete]

Photos of the GSD "Punto" muzzle power reducer are attached, one muzzle has the ports open while the other is closed. Hydro-braking is used to absorb power from the shot, but is an "energy waster" and your loading effort is fully used up unlike the situation with a partitioned air reservoir system where you save some of the loading effort for the next reload having not fully depleted it all if you only take a low power shot.

The muzzle contains no shock absorber as that function is performed by a rubber bush on the piston nose which was standard practice in GSD spearguns, as were the moving plastic jaws used in the piston nose for grasping onto the ball tail ended spear.

 

[Zahar]

Need help describing the operation of this gun with signs of a valve gun! Very interesting model of 1972! Perhaps some priorities for Inventions will be changed or become clearer!

 

[popgun pete]

The “Katiuscia” is the variable power version of the single power “Dynamic” and has a rotating power dial built into the rear end of the gun. When you pull the trigger a system of levers mechanically withdraws a plug from the rear of the inner barrel which acts as a releasing valve. In the “Dynamic” the plug valve being opened allows compressed air to flow into the inner barrel and drive the tailless piston down the barrel. The “Katiuscia” uses these exact same parts, but with one important difference, the releasing rear valve plug is not acting as the airflow valve, but as a pneumatic control element in a servo type arrangement. As the stroke of this rear plug which is operated by the trigger via pivoting levers was not able to be limited by a control system the Italians ingeniously built a second valve and throttle system just in front of it at the rear end of the inner barrel. This throttle works by controlling access to an aperture created by a rectangular side window formed in the plastic rear inner housing that serves as the rear termination of the inner barrel in the gun by using another valve body that is cylindrical and about 2 centimetres in length sitting directly in front of the reciprocating plug valve. Changing the stroke of this second valve body controls air flowing from the tank via the housing side window into the inner barrel during the shot, the stroke length being controlled from the power dial by a sliding rod pushed by a curved ramp feature on the power dial. The sliding rod accesses the second valve body by a claw reaching through that side window. Although the power dial bears numbers the stroke opening is continuously variable rather than in steps. This system is very clever and compact, but obstructs airflow even when fully open as the second valve body is a cage type construction with a valve built into it that blocks air by its very presence, plus it adds a dogleg to the air flow path. It also shortens the inner barrel working course of the piston, but at a few centimetres this is trivial. Being a throttle system the gun expends all its loading effort energy with every shot, hence its additional complexity and tiny precision made additional throttle valve parts were not really worth the big engineering effort as the more indirect air path reduces the gun's efficiency even at full power.

 

[Zahar]

Thanks Pete! The gun is coming towards me! I will study !

 

[popgun pete]

Thanks Pete! The gun is coming towards me! I will study !

Make sure that you have a big box to put the multitude of parts in. The tank is held by four metal dogs that expand out into slots cut in the tank wall as in these valve operated guns the inner barrel does not hold the gun together, the tank does that job. To keep the tank wall thin and not using screw threads to attach end bulkheads the Italians used this unique dog system plus they rolled over the other end of the tank to form a flange that catches onto the front plastic bulkhead that is moulded onto the inner barrel tube. All very expensive to make and nothing like the Sten type construction which can be churned out relatively cheaply. This plus the lack of spares and a high retail price sunk these guns, however the "Katiuscia" is a floater thanks to that unique construction, but not by much! The most beautiful of guns in the pneumatic speargun world and powerful with their 14 mm inner barrels, but once the releasing valve “O” ring fails the guns are unrepairable unless the critical white inner moulding can be replaced with a new fabrication. This white plastic nylon moulding was GSD’s solution to making the inner parts pressure isolated as there are no joins to seal off, except where the moulding slides onto the rear of the inner barrel tube, that being accomplished by twin “O” rings.

 

[popgun pete]

Here are some photos of a “Katiuscia” in pieces. Note there are many pins and securing rings not shown here and the plug valve is also not shown, but the white plastic rear inner housing is. This housing is critical as it holds the releasing valve "O" ring which is trapped between two brass pieces co-moulded into the housing with the plastic flowing around it. I dug the rubber ring out on one gun and it had an integral flange jammed tightly between the brass pieces, it is never intended to be removed and the design is to stop it falling out of position when the gun is fired. Getting the ring out I had to fragment it and I think the flange was created when the component was squeezed up before placing it in the moulding die. In order to replace the rubber seal you purchased this whole white plastic section as an assembly. I cleaned the cupped brass ring seat and tried an "O" ring close to the size, but it never stayed in place when I operated the gun. Somewhere there may be a bin of these spare GSD parts laying forgotten, but it is unlikely.

The “Dynamic” uses a similar moulding, but lacks the rectangular window that is used in conjunction with the power regulator throttle valve. These parts are shown in the last two photos here.

You can see one of the four metal tabs or locking dogs through the window in the top of the rear handle housing. Just below the "c" in Katiuscia.

The power regulator throttle valve with an inner pin that is sprung loaded.

The critical releasing valve seat seen through the elongated airflow windows in the plastic housing.

 

[popgun pete]

Note that dismantling these guns is all done from the rear end as the front plastic bulkhead is moulded onto the inner barrel tube. The muzzle screws off to pull the piston out while the black plastic nose cone is actually just a cover held on by the muzzle, so nothing can be done from the front end except to change the oil in the gun.

Attached is the only image that I have seen of the "Katiuscia" parts, you can see the gun is positively swarming with tiny components.

 

[popgun pete]

Note to remove the green plastic disc-headed screw that covers the inlet valve GSD supplied a red plastic tool with short prongs that match the small ring of holes surrounding the silver and black GSD logo plate on the back of the gun. On "Dynamic" guns this is a one piece cap that simply screws off, but because the outer black part is the power dial the centre which is green plastic has to be unscrewed on the "Katiuscia". Doing so means the black power dial comes off, but watch out for the tiny short plastic rod with two short arms which is white or clear plastic that is biased by a rubber plug spring in the hole in the top of the rear of the red plastic rear housing. This tiny element adds friction to the power dial and prevents it turning too freely, but is easily lost as it will just fall out with the power dial removed. The two small arms locate in a vertical groove that straddles the mounting hole that this element sits in. Finding a replacement is impossible, but something could be fabricated once you know what it looks like.

 

[Zahar]

Russia is bombing Kiev and other cities of Ukraine with cruise missiles! Mail is not working! Katyusha stuck at the Post Office!

 

[popgun pete]

Russia is bombing Kiev and other cities of Ukraine with cruise missiles! Mail is not working! Katyusha stuck at the Post Office!

This seems to be a disaster for which ordinary people will pay the price, it is a very bad situation.

 

[popgun pete]

Just made this diagram for someone else. It is a rejig of the Dynamic diagram showing how the Katiuscia sends air through a new side window that has been added to the white moulding that houses the gun's releasing valve seat. When you pull the trigger everything is exactly the same, but gun pressure moves the new throttle body forward on a short stroke selected by a rod operated finger from the rear power dial. That throttle body movement in turn opens a second valve inside the throttle body which air flows through for the shot, via the new side window. A smart conversion, but the second throttle body chokes the gun. One benefit of the Katiuscia is that it floats after the shot. I have drawn it up on the Dynamic diagram , but the body construction details are different even if the internal guts are the same for the actual trigger valve system. Those details such as the rear tank locking dogs and folded over nose on the tank's front end removed a lot of weight from the gun turning it into a floater, and even more expensive to make!

 

[popgun pete]

What sidelined many GSD guns was the loss of the spear with its ball ended tail. While the distributors had guns to sell they did not seem to have any spears. The gun cannot be converted to anything else as the claw system on the piston nose that grabs onto the ball is also the shock absorber, there being no shock absorber in the gun's muzzle. Their 14 mm diameter inner barrels made them more powerful, provided you could load it, but the Mares Stens and Cressi Sub SL's had more spare parts.

 

[popgun pete]

Why GSD had to go this route for a variable power gun with the "Katiuscia" is that they had no way to control the stroke of the releasing valve, when you pull the trigger the piston plug moves back the same amount in all their guns using that trigger valve. So they had to put their variable throttle system downstream of the relessing valve. In another releasing valve gun with a 14 mm inner barrel, the Alpha C1, the stroke of the releasing valve opening can be controlled and that means the power of the shot is controlled by the releasing valve itself, not an add on.

Note releasing valve is shown open here as a shot is fired from the gun.

 

[popgun pete]

GSD also manufactured a mid-handle version of their gun which used the same releasing valve, but had a different method of actuating it in a mid-handle layout. This gun, the Gran Gara, bears the Dynamic name, but this gun is a variable power model. You can see the power adjustment throttle with the side window covered by a housing which is not airtight, it just provides support for the inner workings. Basically functions like the "Katiuscia", but power is controlled by a lever in the front of the trigger finger guard. This model was not imported here to my knowledge and this gun appeared on a sales page long ago, so I saved the images. Great looking gun, but a sinker and not the sort of gun which was popular in Oz at the time, being the early seventies. No one here would use a trident on such a gun.

The "safety slide" is where that part goes in the rear handle guns, but here I think it is just part of the power regulator lever as seen in the handle frame photo. The single power version of this gun is yellow and black, not red.

The all important GSD spear tail.

 

[popgun pete]

Valve trigger guns usually are held together by the outer tank, whereas sear lever operated guns are usually held together by the inner barrel tube. Using the outer tank as the structural element the end bulkheads typically screw into the tank ends requiring the tank wall thickness being such that it can carry screw threads. That is how the earlier GSD Dynamic was constructed and the thick tank wall made the gun a non-floater after the shot. A different approach was taken with the "Katiuscia" by using an expanding system of four dogs that engage slots in the rear of the tank tube beyond the body tube sealing rings. At the nose end the tank was rolled over to form a cup at the front termination. When the four dogs are driven outwards by a rotating ring on a screw tapered base thus tightening the dogs then the inner barrel and plastic nose bulkhead are trapped inside the gun. An ingenious system that sheds weight from the gun, but makes it even more costly to make.

Note the slots for the anchoring dogs and the indexing notch in the rear of the tank tube.

And at the nose of the gun we can see the front plastic bulkhead poking out through the open cupped end created by rolling and forming an inwards lip on the barrel tank tube.

This means each gun length has its own dedicated tank tube, they cannot just lop a length of tubing off which is cut to the required gun length.

 

[popgun pete]

Note that all the rear handle GSD spearguns use a socket style handle frame that sits on the exterior of the tank tube and is not inserted within it, such as with the Mares Sten's and its descendant clones in many different brands. This usually makes for a bulkier gun as the handle frame has to be that much bigger to swallow the tank's outer diameter. This over-handle arrangement is very common on Russian spearguns as it lends itself to handles made by other than injection moulding methods such as resin lay up matrix construction with a gel coat finish. This was also true of Pelengas guns until they made their latest rear handle guns where the handle moulding is also the gun's rear bulkhead, as it is in the Sten's and Cyrano's.

When the gun's tank diameter is small, say 30 mm in diameter, then the over-handle arrangement presents few problems as the gun is already less bulky due to its slim tank affecting all the subsequent proportions of the gun's external parts. One aspect that needs to be carefully managed is shooting the gun does not send the tank body sliding rearwards through the over-handle to hit you in the face!

 

[popgun pete]

This is the "Katiuscia" rear power dial and you can see it contains an inner sloping ramp that occupies half the dial circumference. By turning the dial the throttle can be continuously varied, but for consistency there are three detent positions that stop the dial in the same place for each of three power settings. Small holes in the inner face of the dial are located by a tiny sprung loaded peg made of nylon with a bullet shaped tip to allow it to pop in and out of these indexing holes. The biasing spring for the nylon detent peg is a small rubber cylinder, these two parts being very easy to lose when dismantling the gun. I spent hours finding them in my back lawn after they fell out.

A small metal disk or bush screwed onto the outer end of the power dial control rod skids along this ramp to vary how far the rod is pushed in or allowed to project out of the gun depending on where the disk is sitting on the ramp. The gun relies on water flooding the entire rear end of the gun for lubrication of this power dial ramp, although the contact loading is very small.