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Chris
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DSV oring problem

Sun Apr 19, 2020 10:43 pm

Need to pick some brains here. Last three dives have been a little wet. Last one wet enough to make exhale harder. It appears the oring around the mouth opening is stretching and popping up, pinching on the barrel and keeping it from rotating full open or closed (whichever it feels like). I switched out the .075? Orings Bryan sent me with the original sized to see if rotating easier would help. I notice I have a lot of scuffing in the barrel, so im thinking the scratches are dragging on the oring and stretching it? Should I try a generous helping of grease? Like Bryan says, that may compount the scuffing by colecting gunk. Havent figured out the amount of scuffing for 50 dives. Might have to start cleaning and lubing more often. The water I dive in is silty, but not like I'm rubbing my face in the dirt.
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Nemrod
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Re: DSV oring problem

Mon May 04, 2020 10:43 pm

You might polish that with some 600 wet-dry paper (wet). It does not need to be completely smooth.

James

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Chris
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Re: DSV oring problem

Tue May 05, 2020 2:38 pm

Might try that. Still fighting a bit of water on my last dive. Might also try swapping my hose loop with the one off my Phoenix just to pinpoint the area of leakage.

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Fibonacci
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Re: DSV oring problem

Thu May 07, 2020 12:52 am

I had a couple of related issues with my DSV, sometimes leaking other times after sitting in my dive bag, over time the o-rings would lock it up almost solid.

Even in the water operation would be very stiff and tend to rotate the entire assembly in the hose a bit meaning the DSV mouthpiece was not oriented in the most comfortable position. Tried multiple different types of o-ring lube, no difference.
Located in Australia, service kits are a long way off and shipping is expensive.

So... I decided to experiment with different Duro o-rings after a chance comment by Peter Katz (of Sea Hornet regulator fame) who said they had a lot of trouble with the rotating Turbo Boost collar o-ring tension causing it to become unusably stiff in storage/transit to the customer. They changed o-ring spec from 70 Shore A to 50 Shore A and had no further problems.

I ordered in some 50-70-90 Shore A o-rings to test:
ASA568-028 for the inner barrel and mouthpiece port, -027 for the wagon wheels.

90 SA worked for a time then locked up solid, worse than OEM condition.
70 SA seemed to perform same as OEM
50 SA worked very well, deformed easily so no more lockups or leakage!​

Only issue being so soft they were sensitive to being cut a little by the mouthpiece aperture if you are not careful to rotate the barrel during installation.
BUT it has reliably fixed the issue...

Regarding the annular scratches in the bore , my DSV was like that from new... appears to be post-moulding CNC machining marks to remove draft and introduce the undercut around the inside of the mouthpiece aperture.
Smoothing with some 600-800-1200 grit wet and dry paper might help but all my issues were resolved with just changing to 50 Duro o-rings.
'A man can never have too much red wine, too many books or too much ammunition' Rudyard Kipling

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luis
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Re: DSV oring problem

Thu May 07, 2020 8:29 am

I designed the O-ring groove clearance in the DSV for size -028 O-rings, but I have also used some metric: 2mm x 35mm. It is a bit thicker (2 mm = 0.078 inches, versus 0.070 inches for standard O-ring).

Even with the thicker O-ring I have not had any issues, but molded parts do have some variations due to tolerance.

The thicker metric O-ring (2mm x 35mm) will create a tighter seal if the tolerance on the parts runs on the looser condition. The trade-off is that it can be tighter and harder to rotate if the two cylinders are already running tight to each other.

Good silicone grease lubrication is always critical. There is always the concern of too much grease collecting debris, but I have not had that issue.

I do not see any issues using the softer 50 durometer O-rings, but so far I have had good luck with the 70 durometer.

It would be interesting to try the thicker metric O-ring (2mm x 35mm) in 50 durometer, but I am not sure where I could find that. I buy most of my O-rings from Mc Master- Carr.


Note: this is the same reply as in the other thread. Same subject.
Luis

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Chris
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Re: DSV oring problem

Thu May 07, 2020 9:37 am

Thanks Luis. I settled on the thicker Oring for the end and the thinner one for around the mouth piece. That stiffens the turning effort but not too tight. Happy medium. Also greased it good. I still have a leak somewhere I havent found, so on my next dive Ill swap my hose loop to see if its in the can or hoses.

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luis
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Re: DSV oring problem

Thu May 07, 2020 11:01 am

I have only used the thicker metric O-ring around the mouthpiece opening in order to make a tighter seal to avoid leaks on a couple of the prototype DSV. That is the only O-ring that seals out the water and seals in the air.

The two radial O-ring are not for sealing purpose. They are exposed to the water on both sides. They are only there to provide a bearing surface with enough friction so that the valve doesn’t move accidentally. Those two O-ring are there to keep the two cylinders concentric with a little gap between the cylinders so that they don’t bind with each other.

My general recommendation is to use -028 (70 durometer) for the two ring barrel bearing O-ring. And then try the thicker metric (2mm x 35mm) in either 70 durometer or 50 durometer for the sealing O-ring around the mouthpiece opening.

You may also have to do a little polishing of the surface and make sure there no burrs or sharp edge on the inside corner of the mouthpiece opening.
Luis

Buceador con escafandra autónoma clásica.

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Chris
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Re: DSV oring problem

Thu May 07, 2020 11:09 am

I'll try that Luis. Thank you.

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Chris
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Re: DSV oring problem

Thu May 07, 2020 11:16 am

That was probably my error the second try was the thinner O ring around the mouth piece. All my valves look to be in perfect condition.

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