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Mares medisten muzle

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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Voja

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Aug 29, 2023
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Dobro vece imam problem koji ne mogu da resim, ne mogu da odvrnem originalnu njusku sa starog mares medistena, hocu da ugradim salvimar vacuum kit. Imate li kakvu preporuku kako da odvrnete staru njušku...hvala.
 

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A couple of views of the muzzle spanner machined up on my lathe. The handles are large bolts turned down on the ends to engage the relief ports in the muzzle with short pins that fit into the port holes.
PNEUMATIC GUN MUZZLE SPANNER R.jpg
 
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The slot in one face is a later addition for muzzles where the relief ports are very close to the nose cone entrance. In those situations an alloy pin is pushed through the ports and the spanner engages this piece of rod on its exposed ends, the rod being just long enough to poke out both sides of the muzzle. For this to work you have to depressurize the gun and push the piston back just enough to get the pin through. A gun that required this approach was the Mares Mirage which has a stubby nose cone, it having two barrels, a shooting barrel and a pumping barrel.
Mirage BRX.jpg
 
Note that the gun must be fully depressurized to remove the muzzle in any case. Otherwise the piston leaning on the shock absorber anvil will load up the muzzle screw threads making it very hard to undo and it will be very dangerous as once the muzzle threads are fully undone the muzzle and piston will fly from the gun with potentially lethal consequences.
 
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The muzzle is one half of a clamp that holds the pneumatic gun together by resisting the action of high pressure air trying to blow it apart. The other end of this strong clamp is the inlet valve body. The muzzle screws onto an external thread, the inlet valve body screws into an internal thread in the inner barrel tube. Some guns use a different arrangement at the rear end, holding the inlet valve body onto the inner barrel tube using a transverse pin or pins. An example is the Technisub Grinta and Jeans rear handle guns. Another is the Soviet Prizm or RPB-1.
Mares Sten Inner Barrel Layout.jpg

PRIZM Diagram revised ANNOTATED.jpg

Prizm depressurised.jpg

RPB-1M all views.jpg
 
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Popgun pete, thank you for your help, I was able to unscrew the muzzle. Can you please help me where to put this little spring valve back, it fell out of the plastic ring when I dismantled the gun?
IMG-9bb78c457137694cf35c7391b5090013-V.jpg
 
That is the older type one-way valve in the power regulator bulkhead and goes in from its rear face. The valve and the rubber seat are combined in that little solid rubber cylinder. When pressure is greater in the gun’s pre-chamber, i.e. the upper handle volume, it is blown forwards against its spring and opening up to let air flow forward into the tank, but when pressure is greater in the tank than the rear prechamber it shuts off air attempting to flow rearwards from the tank.
1983 STEN DETAIL.jpg

mares_1979 schematic (800x562).jpg
 
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That is the older type one-way valve in the power regulator bulkhead and goes in from its rear face. The valve and the rubber seat are combined in that little solid rubber cylinder. When pressure is greater in the gun’s pre-chamber, i.e. the upper handle volume, it is blown forwards against its spring and opening up to let air flow forward into the tank, but when pressure is greater in the tank than the rear prechamber it shuts off air attempting to flow rearwards from the tank.
View attachment 58980
View attachment 58978
Popgun pete, thank you for the explanation and the great diagram, you helped me a lot :)
That is the older type one-way valve in the power regulator bulkhead and goes in from its rear face. The valve and the rubber seat are combined in that little solid rubber cylinder. When pressure is greater in the gun’s pre-chamber, i.e. the upper handle volume, it is blown forwards against its spring and opening up to let air flow forward into the tank, but when pressure is greater in the tank than the rear prechamber it shuts off air attempting to flow rearwards from the tank.
View attachment 58980
View attachment 58978
Popgun pete, thank you for the explanation and the great diagram, you helped me a lot :)
 
That is the older type one-way valve in the power regulator bulkhead and goes in from its rear face. The valve and the rubber seat are combined in that little solid rubber cylinder. When pressure is greater in the gun’s pre-chamber, i.e. the upper handle volume, it is blown forwards against its spring and opening up to let air flow forward into the tank, but when pressure is greater in the tank than the rear prechamber it shuts off air attempting to flow rearwards from the tank.
View attachment 58980
View attachment 58978

Hi Pete! I'm seeking assistance in determining the correct o-ring for the one-way valve on my Mares Sten (Californian) speargun. It appears that the current Sten o-ring kit does not include additional o-rings for this specific part.

Based on my research, the o-ring dimensions should be 3.68x1.78. Could someone please provide the code or part number for the correct o-ring in the current o-ring kits?

I appreciate any guidance or information you can provide on this matter.
 

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The one way valve changed in the Sten and other Mares guns to a two piece element which I have never had to change, It has been used at least since the plastic piston guns appeared. You can see it marked on this Sten diagram, but all the guns use it. That is why nothing appears in the "O" ring kits.
Sten Competition Line parts diagram non return valve.jpg
 
I am just looking at your gun to see which model it is.
sten model question detail.jpg

Your gun is just before the version shown at post #10, so should use the same parts, the numbers are shown in that red box. How we can tell is Mares initially had a butt plate with a metal post on the handle, then they kept the butt plate but moulded an eyelet to tie a cord to the grip. The next thing was to eliminate the butt plate and mould a short tab to provide the eyelet. That means the grip handle floods on all guns since then. The "O" ring is part number 5537.
1983 STEN DETAIL Handle.jpg
 
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Thank you for your reply! Yes, i already checked all the threads and the version appears to be the same as in post #10 and also looks the same as Seac Hunter. My issue is that I can't find a match for the O-ring 5537 within the current Sten codes. It seems that the O-ring 46110102 might be a suitable replacement (Also named as AS568-007 or NBR sh70 - 007)
 
I am just looking at your gun to see which model it is.
View attachment 59282
Your gun is just before the version shown at post #10, so should use the same parts, the numbers are shown in that red box. How we can tell is Mares initially had a butt plate with a metal post on the handle, then they kept the butt plate but moulded an eyelet to tie a cord to the grip. The next thing was to eliminate the butt plate and mould a short tab to provide the eyelet. That means the grip handle floods on all guns since then. The "O" ring is part number 5537.
View attachment 59283

Attached, you'll find a better photo. The butt plate is removable with one screw, and inside, there are small styrofoam balls. I assume they are there for buoyancy reasons. Also the plate handle is plastic
 

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Yes, that is what I thought it was, The butt plates are usually sealed with a gasket using some goo that sets once the screw is done up, if you remove the plate the gasket will usually not seal again. In that case stuff like silastic will work, but to stop the butt plate being glued on you need to have some release agent like oil to make the surface slippery, just a touch, don't overdo it. The styrofoam balls may be a later addition. If the butt plates still keep water out I don't undo them. That model is eighties vintage and Mares probably don't bother with spare parts for it. As that "O" ring serves as a stationary gasket close enough will do, just size from the old one. In the earliest Sten guns the one way valve is a rubber block with a small coil spring and the brass seat is screwed in to capture it in the bulkhead. To prevent leaks around the screw thread it is held in with loctite, which means the bulkhead must be as clean as a whistle with zero oil. That was done because the bulkhead has stand-off legs, later on it is a cylinder and can lean against the handle boss which holds the brass plug in place, hence no need for a screw thread and the seal can be an "O" ring.
mares-sten-original-model-jpg.58928

original-mares-sten-without-tank-jpg.58934


 
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More info on rings here.
I worked my way through the Scubagaskets list and found which rings are which, as claimed by them.

OR R/1 46110201 trigger seal on Sten (31), Reef (46), Mirage (28); inlet ball valve seal on Sten 87 (46), Sten 2001 (46), Reef (46) https://scubagaskets.com/product/nbr-70-o-rings-soft-006/

OR 106 46110106 safety lever friction element Cyrano (60), Sten 2001 (60), pumping barrel rings Mirage (46) https://scubagaskets.com/product/nbr-70-o-rings-soft-610-ap7502/ or https://scubagaskets.com/product/scuba-o-rings-green-viton-sh75-610-ap7502/

OR 2031 46110107 piston ring 11 mm barrel Cyrano, Spark, Stealth https://scubagaskets.com/product/epdm-70-sh-011/
or https://scubagaskets.com/product/nbr-70-o-rings-soft-011/

OR 2062 46110220 barrel to pre-chamber bulkhead for 13 mm barrel Reef (71), Sten 87 (71), Sten 2001 (71) https://scubagaskets.com/product/nbr-70-o-rings-soft-016/

OR 122 BIS 46110206 barrel to nose cone seal 13 mm barrel Sten (9), Reef (22), Sten 87 (22), Sten 2001 (22) https://scubagaskets.com/product/green-fkm-115-viton-o-rings-oxygen/

OR 2037 (was OR 110) 46110110 piston ring 13 mm barrel Reef (18), Mirage (9), Sten 87 (18), Sten 2001 (18) https://scubagaskets.com/product/scuba-o-rings-epdm-70sh-012/ or https://scubagaskets.com/product/nbr-70-o-rings-soft-012/

OR 3062 46110228 barrel to nose cone and inner nose cone support Cyrano (22) https://scubagaskets.com/product/green-14-viton-o-rings-scuba-dive-pure-oxygen/ or https://scubagaskets.com/product/green-14-viton-o-rings-scuba-dive-pure-oxygen/

OR 2106 46110245 nose cone inner support to nose cone Cyrano (29) https://scubagaskets.com/product/nbr-70-o-rings-soft-023/

OR Special 46110208 main body or tank ring all guns Reef (20), Mirage (36), Sten 87 (20), Sten 2001 (20) https://scubagaskets.com/product/o-rings-mares-46110208-speargun/

Where there are two choices the rubber type changes, however pneumatic guns do not need oxygen class "O" rings which are usually green.

Note that the numbers in brackets are the part numbers on the exploded parts diagrams for each gun.
"Sten" is the first version of the gun until the rear grip shape and muzzle changed. "Sten 87" is the "Competition Line" model, "Sten 2001" is the current model with the "Cyrano" style rear handle. "Reef" is a continuation of the original "Sten" shape, but with modifications to reduce its production cost (some parts used less plastic, some parts were either simplified or omitted).

They also list these as Mares speargun rings, but the code numbers are not cited.

https://scubagaskets.com/product/nbr-70-o-rings-soft-119/ ID X CS : 23,47 X 2,62 mm

https://scubagaskets.com/product/nbr-70-o-rings-soft-123/ ID X CS : 29,76 X 2,62 mm

The Shore Hardness or durometer of the "O" rings is 70.
 
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