Mordem Saturno

[Jegwan]

I have got my hands on a handsome Mordem Saturno. I have taken it apart. The piston seal is leaking and the trigger tooth doesn't catch.
I thought from looking at the spear, that this was the one that should catch - but it's not.

It's in principle a traditional oleo with 40mm outer barrel air tank and inner barrel with piston. The inner barrel is close to 14mm. The spear "tail" is 10mm and the spear 9mm.

I can't really figure the gun out. It's like something is missing between the hollow spear tail and the piston. The face of the piston is aluminium and it stops against the aluminium muzzle - looks wrong.
The front cone and muzzle are one and made in aluminium.

The piston system includes three parts and seals. A front part made of a combination of aluminium and SS. It has a small rear SS catch mechanism, a SS spring and a Aluminium back part that I believe is the one that shall catch the trigger tooth.

The aluminium parts are corroded in some areas. Not a drop of oil left in the old gun :-(

Any chance that some of you have any knowledge about this gun or have a parts diagram? Any help is appreciated.

Jégwan

 

[popgun pete]

This "Saturno" looks different inside to my recollection of the innards of the gun as it first appeared with the wand-like passive line release projecting forwards from the grip handle. The brass sear lever has an elongated slot for its pivot pin, so it pushes back for the relatch while it moves off the piece that the trigger moves when you shoot the gun. I cannot see that part, but if you take the trigger out then it may be possible to see it. So how it works is the sear tooth is first "up", held up by the blocking piece operated by the trigger, then the piston tail pushes on the tooth and drives it rearwards until it moves off whatever is underneath the front section of the sear at which moment the sear lever tips downwards and the mushroom tail catches on the tooth as the sear lever comes back up under the influence of its biasing spring. That biasing spring is a rubber ring! The piston under cocked gun pressure then drags the sear lever forwards until the mechanism is latched.

The sear lever mechanism is similar to the one in the much later Nemrod "Mariner", it too has an elongated slot in the sear lever. Only there a pull rod holds the front end of the sear lever up, the "Mariner" being a mid-handle pneumatic speargun. Other guns have used this design, the clue is the elongated slot in the sear lever that allows it to both pivot and move fore and aft to operate. Attached is a photo of the earlier gun in its pistol form.

 

[Jegwan]

Makes completely sense Peter. My later model also has a pull rod below the front of the sear lever. Pulling the trigger makes the rod move forward - releasing the sear lever.

The piston was reversed in the gun - like shown on the picture - that's why I got confused.

The small SS hook is the one holding the spear and the anvil it goes through the shock absorber. Why didn't I think of that!

Many thanks,
Jégwan

 

[popgun pete]

View attachment 37858

Makes completely sense Peter. My later model also has a pull rod below the front of the sear lever. Pulling the trigger makes the rod move forward - releasing the sear lever.

The piston was reversed in the gun - like shown on the picture - that's why I got confused.

The small SS hook is the one holding the spear and the anvil it goes through the shock absorber. Why didn't I think of that!

Many thanks,
Jégwan

I thought that it was shown the wrong way around, so I rejigged your photo while trying to work it out. I wondered about the split tip at the now front end inserting into and holding the hollow(?) spear tail from the inside. If so a collet is missing to stop the piston blowing apart, something has to hold it together and also stop air leaking along the rod that forms the piston's spine.

 

[Jegwan]

It shall be assembled in the same order as shown on my picture and then reversed. The spring goes on the slim and spilt SS rod and so does the anvil with the O-ring.

This tiny hook mechanism holds the spear in place when the gun is loaded and release it when fired (the anvil stops at the muzzle and the piston with the slim and split SS rod moves forward against the spring, releasing the tiny hook from the hollow spear tail).

I think I misleaded you with my description of the piston. The part with the grooved seal and the mushroom in one end and the tiny SS hook in the other end is one unit. The part with the grooved seal is fixed and cant move. Sorry about that.

I was so exited when I realised this while reading your first post, so I reassembled the gun, though I was on my way to bed

The gun now catches both the piston and the spear as it should. The grooved piston seal still leaks, so I have to find a solution to that. Any ideas are welcome.

Many thanks for your help and pictures Peter,

Jégwan

 

[popgun pete]

Here is the parts diagram for the earlier version, same type of sear lever, so the gun operates in the same way. Mordem spearguns used to have rubber front sights and line wrap hooks that disintegrated over time leaving the muzzles bare. Note the holes in the rubber shock absorber sleeve! There is a bit more info here on the piston, now you can see all its parts. Note the spear tail termination that fits into the front face of the piston. The "Saturno" was up against the first version of the "Sten", a much simpler and more rugged gun which became the industry standard and probably still is, albeit with changes in style along the way. The "Saturno" has a ray-gun appearance which appears to be the intention when considering its name!

 

[Jegwan]

Yes - it sure looks like a ray-gun.

Thank you very much for posting the diagram.
The spear tail, front sight, piston system and valve cap are different on this early version. The rest looks the same as mine.

Is it id 12 that interacts with the sear lever?
I believe I can machine a new piston system for mine with O-ring seals like this one has.

I got to get it up and running and "ray" a fish or two with it..

Jégwan

 

[popgun pete]

Yes, part 12 is the top of the mushroom head, part 11 is the mushroom stem. The piston is typical of the late sixties period where they were assemblies of a number of smaller sub-component parts. The coil spring allows the collar (part 7) to slide forwards and force the jaws closed on part 6 that are formed by the split in the front end of the rod so that they grip the spear tail extension which is usually a small metal ball on a tiny integral stem. When the gun shoots the piston slams into the anvil (part 16) which causes the collar (part 7) to slide back, the jaws to open and the spear tail to escape the grip of the piston. The collar and spring are trapped in place when those parts are screwed into the piston's centre section, part 9. The problem with these pistons is the jaws don't always work and the ball on the rear end of the shaft can be bent on its stalk, or worse still, break off when the owner keeps slamming the spear into the gun and it fails to be retained in the gun. Last guns that I know of using the ball-ended spears were the GSD pneumatic guns.

The Mordem "Strale" hydropneumatic was released in 1966, so the "Saturno" pneumatic will be some time after that. The low grip handle and the trigger operated slide running between side plates that moves the short pull rod are not the best design choices for a rear handle speargun, as we now know it can be done much easier and with fewer fiddly small parts that detract from reliability and take longer to assemble on the production line.

 

[Jegwan]

Thanks Peter.

I went to a near by harbour yesterday to test the guns bouncy - The sea is still to cold for a dive in my opinion. The water there is not very salt - almost fresh.

The gun is close to neutral - but it does not float. I will probably need to put a floater (cork from a nice bottle of wine) in the circular hole in the handle - and maybe I also have to make some new lighter versions of the heavy steel plates holding the handle to the barrel or the sliding one between the trigger and the trigger rod (id34).

I managed to get the piston seal to seal by putting 3 small and thin O-rings underneath it - not a very optimal or elegant solution - but it seals for now...

When the gun got further pressurized the seal at the trigger rod started to leek (only when the gun is loaded) - so I have to have a look at that.

This is the first time that my wife thinks a speargun looks good
She said that if she's ever going to try spearfishing while diving - this is the gun that she would prefer. She don't see it as a raygun - no; she calls it the GucciGun!

Jégwan

 

[popgun pete]

Looks like style has triumphed over substance if the gun is a sinker, which we now know that it is thanks to you. The "Saturno" would have found it difficult to compete with the "superlight" floating rear handle pneumatic guns arriving on the market just as it too appeared.