Omer Skorpion spares

[olliric]

A friend of mine asked me to overhaul a 20+ yo Omer Skorpion he hardly ever used. The gun was dismantled, cleaned and inspected in all its components. Despite the large amount of oily sludge the overall conditions are still remarkably good and could be returned in as new conditions or even improved while rebuilding it. Here are the areas that need attention.


Piston:
The 13 mm piston is in good conditions but it has a large cup seal I have seen on other older guns and never liked. The soft seal skirt contact area is large and while it is pressurized it creates considerable friction which is evident when loading the gun. In the picture the one on the right is the Skorpion 13mm piston and the left is the 11mm Cyrano piston. I would like to change the whole piston and ideally get one with the seal like the Cyrano. That seal is thicker and stiffer and has a very thin edge that produces minimal friction and maintains better lubrication. It is a common seal I have seen used in high pressure hydraulic system in various dynamic sealing applications in components from proportional valves to hydraulic cylinders. Apart from the Cressi Saetta it seems that most other 13 mm pistons have the big soft seal and the 11mm ones have the smaller one. I have still have not figured out why. The Cyrano even on higher pressure offers smoother loading of the 13mm guns I have used and it not just because of the smaller piston area.

Charging valve:
The oil degradation has caused some corrosion of the valve 6mm ball. I could buy a new ball or change the whole valve. Is there one from other brands that fits?

Shock absorber:
The bushing is partially broken at the step where the piston lands. What brand absorber can fit?

Trigger release pin:
It has a 3mm pin. Is there any 1.5mm upgrade kit? The original trigger contact area with the pin is only plastic so the 1.5mmpin may work only if the trigger is changed to one like the Mares with a stainless adjusting screw. They look identical minus the adjusting screw.

http://www.articolipescasportiva.it...p?pageelenco=2&macro=141&categoria=92&id=1290

Seals:

Does anyone has the dimensions of the O-rings. One post mentions that the Tempest handle is the same and so are the O-rings. The tank is 40mm dia. Does it have the common issue with the “special” O-ring (CS2.25x31.2 ID) like Mares and others?

 

[olliric]

I have drawn the Omer Skorpion piston model and shock absorber. Hopefully someone has some 13 mm guns with suitable used parts to compare. I have got the feeling that the Cressi Saetta piston looks very promising as an upgraded replacement. For the shock absorber the older Cressis SL or other 13 mm barrels gun should work.
Tomorrow I will work on the O rings as it seems that I may be the first one to attempt to figure out the original dimensions.

 

[popgun pete]

Various pistons from a few years back.

 

[popgun pete]

Omer Tempest airgun Oring Set

O-ring set for Omer Tempest pneumatic speargun.

merehunt.ee

 

[popgun pete]

This is an Omer Tempest which provided the basis for the later Skorpion. The Tempest rear handle was also used for the later production Mamba spearguns, including the Magnum version.

 

[olliric]

Hi Pete, thanks for the information. You have the most comprehensive collection of piston on the planet
In the end I figured out all the O-rings and made the enclosed spreadsheet with the dimensions. I have used Cyrano's O-rings from my stash for all except the 2 in the barrel grooves and the muzzle to tank one which I bought in Viton from China. I have ordered from Edosub the Seac shock absorbers, Cressi Saetta piston with PU seal, cressi spear end and Edo's synthetic oil SAE10. The Seac Asso shock absorber is almost identical in dimensions to the Skorpion and most probably also the Seac Caccia which is the one Edo is sending me.
Omer power regulator piston is undersized for the O-ring and bulkhead which is the same bore as Mares. The old O-ring was in fact extruded.
Have you ever used the Edo's synthetic oil? I got that because the Cressi oil he also has uses a terrible bottle that always leak in the luggage.

 

[popgun pete]

The assorted piston photo was not taken by me, it appeared in another thread. I only use motorcycle fork oil made by Castrol as that happened to be what was in stock and was the specified grade of SAE 10 recommended by Mares.

 

[olliric]

I see, I did not know. Mares using fork oil? That is where the fork oil thing came from then. I just hope there is enough emulsifying additive in fork oil to keep water contamination in suspension like in lubricants used in ships thrusters, oil lubricated stern tubes, stabilizers and variable pitch propellers. That is the reason why I never wanted to try silicon oil despite the apparent performance improvement. In Italy there lots of guys that love the stuff. In my guns I check the oil for water and do regular oil flushes to keep the internal parts in good conditions. I opened my Cyrano for the first time after 30 years and it was in great conditions. Synthetic oil is a lot more stable and much less prone to sludging so I am curious to try it, I just hope is not the biodegradable type which is becoming very common for below the waterline applications and in my experience seem to get water contaminated a lot faster than conventional oils.
After 15 years the Omer Skorpion oil was a total mess and broke down in lots of sludge e organic acid that corroded the inner parts of the charge valve, ball included. The spring is still ok but looks on the thin side compared to the Mares one. I have ordered a ceramic ball in China. The oil I bought is SAE 10 but I would be curious to try a lower viscosity which would be fine given that there is no thermal implications, low loading and no metal to metal contact in spear guns and where we do not want the dampening effect of thicker oil like in fork application. SAE 10 is probably an old days legacy where SAE 10/ISO32 was the lowest viscosity available. My next bottle will be SAE 5

 

[popgun pete]

Mares don't mention fork oil as such, just the grade as can be seen in the original instructions for the Sten. Other viscosities were available, but this is what Mares used in all their guns.

The oil in the Skorpion could have been contaminated or someone put the wrong oil in it, with used guns you don't know anything about how it was used or abused. Never had sludge in any of my guns and some of them were produced long before that Skorpion.

 

[olliric]

The oil in the Skorpion was the original put in from Omer. I recall when my friend bought the gun and he never did any maintenance afterwards. Who knows what they put in originally. Some of the sludge may have been the result of excess grease put in. The very dark color of the oil and smell resembled old EP grease. Speargun oil main features should be corrosion protection and emulsifying properties. Viscosity SAE 10 /ISO 32 and possibly lower. As I mentioned before the best match would be oil used in underwater equipment applications. All manufacturers of such equipment use hydraulic oils such as Castrol Hyspin or Shell Tellus but in recent years environmentally friendly biodegradable oils have become more common. On one ship we made the switch from conventional to biodegradable for the thrusters and fin stabilizer one piece of gear at the time and noticed that the biodegradable oil would cause much faster seawater contamination. A major headache for myself caught between the cruise line industry corporate political agenda and the well being of the equipment.

 

[popgun pete]

More oil could have been added in the past by using the hand pump, you don't have to open the gun up. Motorcycle telescopic fork shock absorber oil is ideal for pneumatic speargun operation, the gun operates at low temperature and relatively few cycles. The fork oil contains anti-corrosive properties given that motorcycles operate under a wide range of weather conditions.