• Welcome to the DeeperBlue.com Forums, the largest online community dedicated to Freediving, Scuba Diving and Spearfishing. To gain full access to the DeeperBlue.com Forums you must register for a free account. As a registered member you will be able to:

    • Join over 44,280+ fellow diving enthusiasts from around the world on this forum
    • Participate in and browse from over 516,210+ posts.
    • Communicate privately with other divers from around the world.
    • Post your own photos or view from 7,441+ user submitted images.
    • All this and much more...

    You can gain access to all this absolutely free when you register for an account, so sign up today!

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)

SEAC HUNTER DIAGRAM O-RINGS_UPDATED.jpg
 
  • Like
Reactions: Jegwan and grantl
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:)
 
Last edited:
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.


34x2mm o-ring.jpg
 
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.

ORIGINAL SEAC O-RING 32x2.15MM.jpg
 
Last edited:
34 x 2 mm might work well if the compression would not be 1.45%. But the Shore hardness is also important.
 
34 x 2 mm might work well if the compression would not be 1.45%. But the Shore hardness is also important.
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.
Mini Titan Sheet AR.jpg
Mini Titan Sheet BR.jpg

This is the job that I was referring to in my post #28 on page 2.
 
Last edited:
  • Like
Reactions: Diving Gecko
Nice work Pete!
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.
 
DeeperBlue.com - The Worlds Largest Community Dedicated To Freediving, Scuba Diving and Spearfishing

ABOUT US

ISSN 1469-865X | Copyright © 1996 - 2024 deeperblue.net limited.

DeeperBlue.com is the World's Largest Community dedicated to Freediving, Scuba Diving, Ocean Advocacy and Diving Travel.

We've been dedicated to bringing you the freshest news, features and discussions from around the underwater world since 1996.

ADVERT