ARGONAUT DSV mouthpiece design information.

[Luis H]

Using 50 durometer O-rings sounds like a possible alternative, but I have never had issues with the basic 70 durometer O-rings.

I always use good traditional silicone grease. I would never use Christo-lube (or any of the other O2 compatible grease) for this application. The traditional silicone grease is a much better lubricant and it doesn’t break down and separate with time.

You do not need O2 compatible lubricant with ambient pressure gear. You only need O2 compatible lubricant in the first stage if you are using high O2 mixtures (> 40%).

I have about 8 different DSV on different regulator hoses and regulators. Many tend to sit for many weeks or months without using them. The silicone lubricant doesn’t separate or break down on them. I just rotate them before a dive and they work well.

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.

 

[Fibonacci]

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

Thanks for the info Luis, I did try all sorts of different o-ring lubricants (generic silcone grease, Dow Corning 111, Tribolube 71, Super-Lube) to no avail...
It may indeed be a tolerance issue... but from my POV the 50 Duro o-rings fixed the problem reliably.
Seems like the outer housing bore has been CNC machined after moulding to eliminate draft taper and create the undercut o-ring relief, may have drifted from specifications?

 

[Luis H]

Thanks for the info Luis, I did try all sorts of different o-ring lubricants (generic silcone grease, Dow Corning 111, Tribolube 71, Super-Lube) to no avail...
It may indeed be a tolerance issue... but from my POV the 50 Duro o-rings fixed the problem reliably.
Seems like the outer housing bore has been CNC machined after moulding to eliminate draft taper and create the undercut o-ring relief, may have drifted from specifications?

I would never argue with success.


AFAIK, the only thing that is machined after molding is the area around the mouthpiece opening to provide gradual leading edge to the O-ring as it slides sideways onto the sealing surface.

The only issues that I have personally seen is the edge being a bit sharp, where the O-ring catches as it slides sideways into it. I always inspect that edge and make sure it is well de-burred.

 

[txgoose]

Thank you @Fibonacci and @Luis H, I am going to try both. I was in the process of ordering some yoke and din o-rings for the season so I added some 50 durometer 028's because it was an easy add-on. And both solutions give me a opportunity to disassemble that thing, which most vintage folks enjoy anyway.

 

[scrane]

The DSV is a great invention. The dilemma is you want it loose enough to activate easily, but not so loose that it can be toggled inadvertently. I think Luis made the right decision in leaving it a little bit tight.

 

[Luis H]

I am repeating some of these from other posts in VDH and maybe here. I hope it is not too repetitive.



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.



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 either the -028 or the thicker metric (2mm x 35mm) in either 70 durometer or 50 durometer for the sealing O-ring around the mouthpiece opening.

The user may also have to do a little polishing of the inside surface if it has gotten scratched with debris and make sure there no burrs or sharp edge on the inside corner of the mouthpiece opening.

 

[txgoose]

I am five dives into the 50 Duro 028s and I am very pleased. I love the design of the DSV. Makes entry, exit, and the occasional floating SI so much easier. Thank you both again for the input. Happy camper, here.

 

[Luis H]

Here is a diagram showing the components of the DSV, including the three O-rings.

You will notice that I am showing the preferred O-ring and at least one option to account for possible tolerances on the clearance and fit.

Let start with the wagon wheel valve O-ring (Item # 6 in the diagram):

The design nominal O-ring is an SAE -027 (in either 70 or 50 durometer).
If there is a loose fit then the metric 2mm x 33mm will provide a tighter fit. In this case I recommend using the softer 50 durometer O-ring.

The mouthpiece opening O-ring (Item # 9A in the diagram):

The design nominal O-ring is a SAE -028 (in 70 durometer).

If it feels loose or there are any signs of a leak then the metric O-ring will provide a tighter fit.
The recommended metric O-ring is either a 2mm x 35mm (or a 2mm x 34 mm works and it can be easier to install).

This O-ring slides past the mouthpiece opening in the outer tube (Item # 3). So make sure that the inside edge od the opening has a smooth chamfered edge, not a sharp edge. After assembly, operate the DSV and check that the O-rind stays in place, in the groove, while fully opening and closing the DSV.

The two circumferential inner tube O-rings (Item # 9B in the diagram).

These O-ring can be either a -030 or a -029.

Either one works fine since this is not a sealing O-ring. These O-ring are not intended to create a seal, they are intended to create a constant gap between the two cylinders and create a bearing surface for sliding, with just enough friction so that the DSV has to be intentionally rotated. The gap is designed so that the two cylinders are do not slide and scrape on each other.

This O-ring are intended to keep sand or dirt from getting in between the tubes, but it is not intended as a water tight seal. The space between the tubes is a wet space and it has to be a flooded space.

There is a vent hole below the mouthpiece opening in the outer tube (Item # 3). Any attempt to seal the space between the tubes to keep it dry, by plugging this vent hole is a very bad idea. That could create a sealed void that will not equalize with the ambient pressure as you dive. Please, never consider closing the vent hole with a plug. It is not a good idea to create a sealed void.

The vent will also allow you blow the little amount of water in the mouthpiece tube before opening the DSV. By blowing the water from the mouthpiece tube, you can keep the hose-loop dry.


To disassemble the DSV:

Remove the retainer screw (Item #11) and rotate the inner in the closing direction and little past it so that the opining in the inner tube is far from the opening in the outer tube. Then slide the inner tube sideways. Only slide the inner tube sideways when the opening in the inner tube is far from the Opening in the outer tube, to avoid pinching or cutting the O-ring.

To assemble the two tubes just revers the process. Make sure the opening in the inner tube is not lining up with the opening in the outer tube. The inner tube opening should be facing up, near the label.


Lubricate all O-ring with good quality silicone grease. I do not recommend using any of the oxygen compatible grease. They do not work as well for this application and they are not needed.

 

[rhwestfall]

@Luis H

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[Luis H]

316 Stainless Steel Slotted Screws, High-Profile, Narrow Fillister Head, 6-32 Thread, 1/2" Long

Lg.

Threading

Head Dia.

Head Ht.

Tensile Strength, psi

Specifications Met

1/2"

Fully Threaded

0.226"

0.132"

100,000

ASME B18.6.3

BTW:

“Cheese head” screws are defined by their head type. The cheese head has cylindrical sides with a flat disc top and a flat bearing surface. The head height is approximately half of its diameter and typically features a slot drive.

The name cheese head derives from the similarity in shape and proportion to that of a wheel of cheese.

Cheese head screws feature a deep head, which permits a deep recess, making them well-suited to a slot drive. Cheese head screws are most commonly available as cap screws and are frequently used in appliance manufacture, fixing electrical components, and within the automotive industry.

Fillister head screws, or raised cheese head screws, are similar to cheese head screws because both have cylindrical sides and a flat mating surface. However while the cheese head has a flat top, the fillister screw head has a domed top resulting in an overall deeper head.

Pan head screws have largely replaced cheese heads in many applications. However, the deeper slot capability of cheese heads makes them the preferred choice for applications requiring extra head strength and those where a deeper drive socket is desirable. For example, when frequent disassembly is required and damage to the drive socket is likely.

Source:

What are cheese head screws?

Written by Jody Muelaner "Cheese head" screws are defined by their head type. The cheese head has cylindrical sides with a flat disc top and a flat

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