First Double Hose Dive In THIRTY YEARS!!!

[Gilldiver]

I have a few of the old DACOR mouth pieces that have the snap tabs attached at each side. The original neck lace mouth pieces (in fact one is on my deep set of regs right now).

A short line attached to the mouth piece with a strong/large aligator clip should do it.

Pete

 

[Luis H]

I will let Luis describre the PMDSV.
N

Nemrod is referring to a mouthpiece plug. I asked Dave (aka dbg40) if he could make a plug to fit the USD curved mouthpiece and he did a great job.

It does a good job of stopping any free flows when the mouthpiece is out of your mouth. I tied to my shoulder strap, therefore when I plug the mouthpiece it also hold it in place.

I have been thinking of having more made. It is just a simple idea. The only trick is on the fit with a slight tapered wedge and on using a semi-soft material.

 

[Nemrod]

The PMDSV works pretty good in my tests. I am pleased with it as a simple concept. Of course, a DSV would be better but given that no such suitable animal exists the PMDSV is better than nothing. It works especially well when swimming on the surface in my preferred method --on my back--no stupid snorkel to flail about--eliminating freeflow due to the diaphram being underwater. Otherwise I have to shut the tank valve off. I am currently clipping the PMDSV on a short lanyard/boltsnap to my right shoulder D ring on my Hog harness, here it also serves to help stow the mouthpiece when using your octapus or buddy bottle regulator or stage etc. N

 

[duckbill]

Has anyone tried one of those EKWTLMV? If you haven't, then your IYDYOOLV will suffice.

Just ask yourself......WWMD (What Would Mike Do)?

 

[Nemrod]

PMDSV

Poor Man's Diver Selectable Valve--is that right Luis or am I have another brain cloud? Regardless of the acronym the purpose is to close off the mouthpiece thus "forcing" the regualtor to see equal pressure fromdiaprham to duckbill--the mouthpiece being closed it does not want to freeflow. N

 

[Luis H]

PMDSV

Poor Man's Diver Selectable Valve--is that right Luis or am I have another brain cloud? Regardless of the acronym the purpose is to close off the mouthpiece thus "forcing" the regualtor to see equal pressure fromdiaprham to duckbill--the mouthpiece being closed it does not want to freeflow. N

Well the PM is definitely "Poor Man", since I kiddingly label it that.
I am not sure about the DSV. That is a re-breather acronym which I thought that it stood for "Dive Surface Valve", but again, I am not sure.

 

[Nemrod]

Yeah, I think your right--I don't much about rebreathers, just the mouthpiece looks like it may have another application if not so expensive as we have discussed before. Ha-ha. N

 

[John C. Ratliff]

I may be wrong, but I think that the DW Air Stream did not have the same venturi nozzle as the Mistral. My understanding is that the Mistral was the first regulator to include a well design venturi nozzle.

Many (if not most) Stream airs were retrofitted with the Mistral venturi nozzle. Most were upgraded by the owners, but there has been some speculation that US Divers might have retrofitted the last of the Air Streams (in their inventory) with the newer nozzle before selling them.


If you are going to leave a double hose unattended you do need to close the tank valve. I would think that closing a stage bottle valve is a good way of reducing any risk of a free flow or any air loss wile not in use (no mater what regulator you are using).

The DW Stream Air did have a different nozzle, but it was too good as a venturi. Therefore, the DW Stream Air had to be pointed slightly off-center of the intake tube, or it would free flow (continue to flow even after the inhalation had stopped). With it off to one side, there was enough turbulence to disrupt the flow a bit, and allow the Stream Air to function as a normal regulator.

When the Mistral orifice became available, it was an "improvement" in that it could be pointed directly down the intake tube, and not cause such a drastic flow. This is because of the two holes in the side of the nozzle, which diverted some of the air into the case, preventing the vacuum that forcefully brought the diaphragm down on the Stream Air (and Jet Air, by the way). As Fred Roberts stated,

The orifice of the Mistral has been redesigned to overcome the difficulty of the DW and approach the performance of the DX, without the gush of air. This has been achieved by placing primary and secondary holes in the orifice...

The orifice of the Mistral aimed down the inlet hose. Primary air rushes downthe intake hose drawing second chamber air with it. In the DX and DW this action had caused a rapid depression of the low pressure diaphragm (28) and thus the gush. Note that in the Mistral the air also escapes through secondary holes at the side of the orifice. THis secondary air flows along the inner walls of the box and fills in the void left by the air sucked down the intake. In doing this it acts as a damper on the movement of the diaphragm (28) and keeps it from a violent response.(Roberts, Fred, in Basic Scuba, Second Edition, page 181.

I have both the Mistral and the DX, and used to have a DW Jet Air. All of these are great regulators, but I like the DX best because of the smoothness of the breathing cycle, the ease of breathing, and the quietness of the intake (with a hose within a hose dampening the noise of inhalation, which is quite noisy in the Mistral).

By the way, there are two regulators with a better-designed (in my openion) orifice than the Mistral. These are the Healthways Scuba Deluxe (Gold Label), and the Royal Mistral by USD. The Healthways regulator negated the great flow potentials with a poorly-designed hose/mouthpiece system. But stick a USD hose/mouthpiece on the Gold Label Scuba Deluxe, and it's quite a breathing machine. The Royal Mistral has simply a big hole in the case, pointed down the intake (no orifice, as confirmed by photos that Bryan posted for a time on the Vintage Scuba Supply website before he had his own up and running). It then had a metal baffle plate partially blocking the intake, to disrupt the flow just enough not to have it free-flow in inhalation. USD boasted that this regulator (the Royal Mistral) had the highest flow rate that they had by then recorded (but the number right now escapes me).

John

 

[duckbill]

I'm sure this has been addressed before, but I guess I never paid attention to it.
With the Stream Air and the Mistral both sharing all the parts except the orifices and band clamp, how was the orifice of the Stream Air aimed off center? In other words, the dowel pin locates the positions of the body washer, top box and body relative to one another the same way in both models. If the threaded opening for the orifice in the body of a Mistral is pointed down the horn on a Mistral, wouldn't it have also pointed down the horn on a Stream Air? How was rotating the body in the Stream Air effected? Was a new hole drilled in the top box? Was this done at the factory? I would assume not, since the Stream Air preceded the Mistral and the parts (other than the orifice) weren't changed, including the positions of the dowel holes. Am I right to conclude that turning the orifice to the side of the horn on a Stream Air was a consumer alteration which necessitated machining?
Curious.

 

[John C. Ratliff]

Duckbill,

Your analysis is correct, except that because the Stream Air came first, its top box would have to be drilled to accept the dowel in a different position when it was converted to a Mistral orifice. Or, the dowel would need to be left off, and the regulator's retainer nut would have to be screwed down tight. I did that with my VRC-2 50 Fathom regulator by AMF Voit. Its body was oriented incorrectly for maximum effect (with the venturi holes oriented toward the box, and not down the intake hole). I think I have seen somewhere in the past the Stream Air-to-Mistral conversion discussed, and it did need to have another hole drilled in the top box. It would be easy to confirm by having someone with a Stream Air, which has the Mistral orifice in it, see whether there are two holes in the top box.

The Jet Air is different, in that the fiberglass housing was molded around the regulator's body, so that it fit into grooves and really could not be moved. So it really cannot be fully converted to the Mistral orifice.

John