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O-rings (especially trigger pin)

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.
Slightly updated O-ring schematic for the Seac Hunter. Info is still the same as before, but I am listing the possible alternatives for the main barrel seals.
(From earlier in this thread, I can see Pete says that for older Mares' guns he did try the exact metric alternative I am listing and it did not work, so no guarantees here. But I have a feeling it could work given the diameter of the o-ring groove and the diameter of the alternative o-ring. Together, they should end up very close to the OD of the original ring when mounted)

 
Reactions: Jegwan and grantl
This is useful and very valuable information!
Thanks Diving Gecko!
 
As we now know, the main bulkhead o-ring the Seac Hunter (and perhaps the Asso too) uses a non-standard 32x2.15mm (ID x W) ring.

I would however really like to find an off-the-shelf ring that could do the job and though I know others have not had much luck, I have not killed off the idea entirely. Yet;-)

I ordered a bunch of o-rings off the web here in China in my efforts to make my own complete replacement sets and of all the o-rings in the Seac Hunter, only the main bulkhead ones seem to not be standard.

I just tried with some different o-rings from the 2mm series and I now have a bit of hope that a 34x2mm (ID x W) o-ring might actually work.

The original, custom ring is thicker at 2.15mm but with an ID of 32mm it is stretched in the groove - which on my handle is app. 34.4-34.55mm (a tiny bit oval). The mass produced 34x2mm ring, while being thinner, is not stretched and thus, the best candidate for an off-the-shelve alternative. Actually, it seems to be possible to buy 34.5x2mm, so that could be worth a try too, but I couldn't find them in China.

I tried with a 32x2mm (ID x W) too, but the stretching of that made it too thin. So, no less than 34mm ID, I would say.

During my first rough tests (just inserting handle in outer tube) the 34x2mm ring feels like it does indeed compact quite a bit against the outer tube and could hopefully obtain a seal. I only have a handle and the 38mm ID outer tube so it is all by feel.
Around New Years, I'll get to test it properly pressurized when reunited with my guns.

So, even though I am a bit of a tease now, I wanted to chronicle my hopes that some handles might actually work standard 2mm series rings.

But there are a number of factors which decide if this will work with your handle and you have to get a little lucky too:
- One of the main things is the diameter of the o-ring grove in the handle. If it is too deep (too small diameter) the o-ring wont be compressed enough against the outer tube. It seems just about doable if it is around 34.6-34.5mm (higher is better). Here, I am assuming an outer barrel with a spot on 38.0 ID

- The gap between the handle and the inside of the outer tube. If this gap is too big, the slightly thinner o-ring might be pushed into the gap and break. For the same reason, don't use the soft silicone rings. Try to get the hardest rings you can and if the gap is slight it is definitely an advantage. The OD of my handle is 37.5-37.65 (it varies as does the groove diameter)

Stay tuned, I'll take the Seac Hunter apart at the end of the month and try with these o-rings. And I might try them in a Mirage as well, if I have the time
 
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Here's a screen shot of the o-ring calculations with my measurements typed in.
The compression is what mostly decides if we have a seal or not and it granted, it is on the low side. Static o-rings are often compressed to 25-30%, sometimes even 40%, if I recall correctly.


 
Here's the data for the original, proprietary o-ring from Seac with the measurements from my handle added. Actually, the compression (at nominal variation) is not that much higher than the off the shelf 34x2mm ring (12.3% vs. 9.4%).

With the Seac o-ring one it does feels harder to slip the tube over the handle but maybe that ring is made of a harder rubber.
But judging by the data, this could almost work - if the ring stays in place, that is;-)

If these slight variations of especially the handle o-ring groove depth is on your side, the 34x2mm (ID x W) is your best bet at an alternative.

 
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34 x 2 mm might work well if the compression would not be 1.45%. But the Shore hardness is also important.
 
tromic said:
34 x 2 mm might work well if the compression would not be 1.45%. But the Shore hardness is also important.
Click to expand...
You are right. If I understand the o+ring calculator correctly, the three compressions values are for the different tolerances of the o-ring dimensions. So, one ring could be at 1.45% whereas another ring of, supposedly, the same dimensions could be at 15.1%. It's cutting it close no matter what.

Yes, to the hardness as well. The harder the better. Especially since with a thinner ring it will also be more at risk of getting squeezed into the gap (which, I personally think is too big...).
It could very well be that the Seac bulkhead rings are of a harder rubber than the regular Shore 70 o-rings.

Hopefully I will have time to test this. Though I don't think I will make a longevity test as I don't feel like going on a spearing holiday yet with these rings. We'll see
 
I thought that readers may be interested in these worksheets I created for a Mares “Mini-Titan” when I received the gun for repair. I knew it was a “Titan”, but I did not knows the model until some time later. It was the first time that I had dismantled one and I knew nothing about it at all, or even the “O” ring sizes it used. To work out the “O” ring sizes I drew up a schematic (refer sheet A) in order to assign location numbers and then proceeded to measure up the seat diameters, the groove widths and the bore sizes of the tubing/component that slid over each location (refer sheet B). So this is what you can do when you encounter a gun that you have zero information on. In fact when I did this work there was no Internet as we have today and Imperial sizes applied for many items including “O” ring charts when technically the country had gone metric. However ask for metric “O” rings and all that you got was a blank look from the guy at the service counter, so all the sizes needed were measured up in inches rather than millimetres and then matched to the specifications in the published size charts in order to find the best fit available from the range of stock sizes.

This is the job that I was referring to in my post #28 on page 2.
 
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Reactions: Diving Gecko
tromic said:
Nice work Pete!
Click to expand...
Thanks, I thought I had thrown those diagrams out years ago, but just found them again during a clean out of old papers. I still had some of the written notes on the "O" rings, however it was a surprise to see the drawings after so many years and that although the paper had discoloured (which you don't see on the scans) they had not fallen apart despite being on old blue lined notepad paper where you tear each sheet off the pad.
 
Just so that this "O" ring info can be found again I will add it here for the Mares pneumatic guns. The "Cyrano Evo" will have to wait until we see all the "O" ring codes for it and its successor, but body rings and inner barrel rings will likely be the same.

The individual "exploded diagram" part numbers for each ring are shown in brackets. "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 first "Cyrano" styled 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).

The part reference numbers now all start with a "46110", those that do not are from earlier versions and have no counterpart today, although that does not necessarily mean that they are no longer available. Last three number actually identify the component and in some cases the numbers have carried over from the earlier code used for the item.

OR 2003 46110242 trigger seal on "Apnea" system Cyrano (49) Sten 2001 (49)
https://scubagaskets.com/product/50-oring-pack-soft-003/

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 2007 46110213 trigger seal Sten 87 (77), seal sat in a removable plastic stirrup with two prongs holding it in the handle

OR 2015 (was OR 102) 46110102 power regulator shaft seal and power regulator piston seal
https://scubagaskets.com/product/nbr-70-o-rings-soft-007/

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/
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 3056 46110227 barrel to pre-chamber bulkhead Cyrano (71)
https://scubagaskets.com/product/nbr-70-o-rings-soft-113/

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/

The "O" rings can be available in different compounds, but as pneumatic guns use air they do not have to be the oxygen service type rings which are green. The latter rings are used to prevent fires occuring in pure oxygen gas equipment such as is found in medical air supplies.
 
I have received the O-rings for overhauling Mares Cyrano, Sten 2001 and probably few more models. I bought them on Aliexpress and choose the green Shore 75A Viton instead of the OEM shore 70A NBR. Except for the price Viton is superior on all fronts. The minimum order quantity for NBR is quite high so for almost the same amount of money you can get 10 pieces for each size in Viton. For about 20 USD you can make 10 O-ring kits. Special O-ring 46110208 (3 each gun) is a custom size Mares uses of the pneumatic guns as well as scuba regulators. I bought the closest sizes and tried the OEM one as wells the 2 Viton on the gun and the best match is CS2.4x35 OD which equates to CS 2.4x30.2 ID instead of Mares 2.25x31.2 Shore 70A.
In the enclosed spreadsheet the two items that are not highlighted were not purchased. One is the the safety lever friction ring that lasts for many years without the need for replacement. The other is the piston cup seal which I have not got down to identify it yet. It would be nice to have it in Viton too.
 

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Any seal that functions as a gasket in a static situation can be made from any elastomeric material, but where sliding takes place you need abrasion resistance even though the surfaces are seemingly smooth that they move or slide on. For that you need carbon black which strengthens rubber, a fact I learned from working in the tyre industry on the manufacturing side for many years.
 
Reactions: Zahar
Absolutely true! Experiments with non-carbon rubber have shown that it rotates when moving and twists, ceasing to work as a movable seal!
 
Viton can be bought in various colors. Regardless of the elastomer in the old days all O-rings were mostly black due to carbon black addition that indeed can improve some of the properties but now color coding is widely used as mixing elastomers can cost dearly in term of down time as I have witnessed in my line of work. I could have bought the same O-rings from the same vendor in green, brown or black but I chose the green as it is the color code of FKM in Europe and more important can be identified when mixed with all the other NBR O-rings I have. The O-rings I bought are all static applications where green FKM in practice outperform NBR especially in dimensional stability. In the specific case I like to be able to dismantled the gun and thus break a seal without the need to change the O-ring. I have done that many times even in applications with 120 C temperatures in heavy fuel centrifuges. If you do that with NBR you may get away with it within the first year but after the rubber looses tension and displays permanent set leading to leaks.
For the gun piston seals I would use black Viton O-ring and possibly polyurethane cup seal.
 
Reactions: tromic
The advantage of the kits from Mares is you get all the rings and a chart displaying which ring is which. Since this thread was started we now have the Cyrano Evo kit and here I have added the locations to the Mares supplied chart. Being low temperature operation the standard "O" rings can be reused unless damaged by long term pressure against a raised mould parting line on a plastic component. I have done it many times. Because the piston is so easy to take out of a gun it can be replaced at any time. One seal that does get hot is the pump piston seal as if you pump your gun to 40 bar you can feel the heat build up in the pump barrel due to adiabatic heating.
 
Yes, for people that is on the first attempt at a gun overhaul and are working with O-rings for the first time your guide charts are very useful. But only if the are overhauling guns with commercially available kits recently produced. That has not been the case for my two Cyrano 850 first series and now Omer Skorpion I have been ask to bring back to life after 15 years of dust and zero maintenance. Both manufacturers have stopped selling the kits and knowing the actual cord, internal diameter and Shore hardness of each O-ring is what is needed to actually bring the gun back to life for a long service life using long lasting seals. Online, there are some 43164290 kits for the old Cyrano but are old manufacture left over past shelf life and you just don't know what your are buying. I would only buy them if I see where they were kept which is not possible with online retailers. Mares only recently have address the UV degradation issue of their kits and the regulators kits are now sold in carboard boxes with no windows. Yet, the brand new complete handle I got 3 weeks ago from Mares factory in Rapallo (the identical white trim for Sten 2001 as the Cyrano was not available) came with the power regulator O-ring broken from just sitting on their shelf with no protection.
I had to overhaul 2 Cyrano first series and even here in Mares country the overhaul kits for the Cyrano first series was not available in probably the best stocked gun shop in the country. I could only get 43164208 kit which is for the EVO and works only in part. 3 O-rings are missing and there are O-rings of no use for the first series. You need two 46110228 and the kits has only one, same for 46110102 you need two of them for the power regulator. More importantly you need the ultra thin 1.78x26.7 ID (46110245) which is missing and seems the Achille's heel of the Cyrano first series. In my old gun it was completely extruded (blown out). Luckily the very first production of the first series had a closed nose so it got pressurized without bursting. The other Cyrano 850 (the latest series of the old ones) I just bought almost brand new has an open nose cone and if the above O-ring blows out you end up with a 25 CC oil spill blown into a cloud or in a large oil sleek. I bet Mares introduced the slot after some moron blew the nose up by going to 30 bar. My old gun original nose cone never leaked or blew up despite keeping it at 22/24 bar during any period of fishing activity for the last 30 years. I changed it because of poor external cosmetic conditions and a slight deformation in way of the thin O-ring that got extruded. As you once suggested the internal nose cone reinforcement considerably reduces the pressure chamber volume and to some extent the performance. I am considering reusing the old nose cone without the reinforcement and if the performance improvement is noticeable against the twin gun run a spectra whipping on the outside of the nose cone to reinforce it.
Going back to the O-rings, the almost brand new 850 I just did had the nose cone reinforcement O-ring deformed but not leaking yet. I am pretty sure it would not be reusable once opened. Other seals could possibly be reusable despite slight but uniform deformations. Due to the poor seal design, that one in particular would greatly benefit being Viton and an higher Shore A. In Solidworks I have a O-ring seal and grove design feature based On DIN 3371 and I check some of Mares seals and grove design. Some are not very Kosher. In the end thanks to some friend I have that works at Mares I got a bunch of all the missing O-rings before I got the batch from China.
 

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There are sets around if you search for them, I just found some right now.


Pneumatic Speargun O-Ring Kit - Spearfishing World

This kit includes all the orings inside the Speargun. All kits are different, choose from the list, the brand and model of your speargun.
www.spearfishingworld.com

The Spark and the Stealth are just Cyrano's with the usual front nose cone bulkhead that you see on the Sten 2001, but sized internally for the 11 mm inner barrel. Their tank tubes are accordingly longer for the same overall gun length as the Cyrano due to the absence of the long muzzle snout. The Cyrano has a double front bulkhead with a pressure bearing inner white bulkhead and a black outer one. If the O ring sealing those two bulkheads fails then pressurized air enters the space between them and that can crack the outer section as it is designed to contain air at atmospheric pressure, not gun pressure.



inner nose cone in white nylon.
https://forums.deeperblue.com/threads/pneumatic-dismantling-how-to-get-inside.90024/ post #7
 
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Nice Cyrano drawing, Thanks Pete. I will add it to the technical literature collection. Apart from the user manual, do you have any documentation on the Omer Skorpion? I started a thread on it but nobody pitched in. In one Italian forum I read that Omer does not disclose any information and requires owners to send in the guns for service. How convenient !!
The unpressurized volume is similar in size to the handle volume behind the bulkhead which is sufficient to propel the spear on low power.
I wonder if that volume addition to the working spaces will improve the ballistic performance. My gun 30 yo nose cone have proven that if you keep pressure below 24 bar the nose cone holds it without bursting and without external reinforcement. I found that the tell-tale pressure relief slot that Mares introduced in the later nose cones is way bigger than needed and causes a pretty severe extrusion on the outermost barrel O-ring where the ring is unsupported by the slot opening. It could have been 1/10 in size and do the intended purpose just fine without weakening the seal. I have now put Viton there.
 
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