Upgrading AL DA Aqua Master

[herman]

I not only don't bend them, I polish off any old burs caused by bending them in the past.

 

[halocline]

A quick question about the spring tension adjustment via the height of the 2nd stage body, I think it's called the seat holder in the schematic. If I screw this part "finger tight" as it say, the poppet is essentially trapped with a fully compressed spring. Adjusting this part seems to be kind of like adjusting a movable orifice in a modern downstream 2nd stage, only you're moving the "other side" of the mechanism. Is that a good way to look at it? You get it right, then adjust the lever height.

Thanks for all the tips so far, and please keep them coming!

 

[Luis H]

A quick question about the spring tension adjustment via the height of the 2nd stage body, I think it's called the seat holder in the schematic. If I screw this part "finger tight" as it say, the poppet is essentially trapped with a fully compressed spring. Adjusting this part seems to be kind of like adjusting a movable orifice in a modern downstream 2nd stage, only you're moving the "other side" of the mechanism. Is that a good way to look at it? You get it right, then adjust the lever height.

Thanks for all the tips so far, and please keep them coming!

Yes, you got it.

There are few disadvantages:

• This adjustment can only be done on increments of 120 degrees since you have to have an orifice pointing down the hose horn.
• You can only back up the Seat Holder a limited amount. For this reason, I prefer to use the old original springs. Some of the new reproduction springs are a bit strong.
• You can only do this adjustment with the horseshoe supports (and horseshoe) removed. This is not a big deal since I do this adjustment early and then the final adjustment is the IP.

These disadvantages are mostly just a minor inconvenience. The Aqua Lung Mentor solved these issues, but we will probably never see that regulator sold to the public (there is only one on private hands).
Note: I am working on some work around to some of this second stage adjusting issues; it may include hardware modifications and perhaps some procedures.


To install the Seat Holder, I first install the spring and seat carrier and temporarily screw the nut all the way in. This pulls the seat carrier back which prevents the seat from being overly scared by the volcano orifice. Then I release the nut to adjust the Seat Holder against an IP of about 150 psi.

Then I proceed to add and adjust the horseshoe lever. The final step may be to fine tune the IP.

 

[Nemrod]

You can only turn that nozzle out but a limited amount or it will sit to high to lock in the V notches. Really, most of the time I run it down much as Luis does and then turn it out to align the nozzle to the first hole that comes up, occasionally it goes to the second if it does not breath to suit me, I try the third. I cannot recall more than going to the thrid hole, in fact, I am pretty sure some of mine are on the first hole. Some of us who have done this a while have a collection of springs and stuff, I never throw that stuff away. Sometimes I try different springs until I get what I want. It does not have as much adjustability as one might like. Dont set the lever to high, I am thinking around level to the can. If it is to high the angle to the tabs on the diaphram are acute and it increases the cracking force. There is a sweet spot for it to sit. Mentioned before but make sure when it goes togehter that the diaphram tabs are centered on the horseshoe. I used to put a tiny drop of Aqua Seal on the edge of the can and set the dipahram down dead center. Now, with the silicone diaphrams I have forgone that step. I also "glue" the duckbill to the top can with a single, small dab of silicone or with the non silicone ducknbills, a touch of Aqua Seal. You want it position such that a line through the slits is center of the can.

The diaphram tabs do not slide on the horsehoe, they roll. I have polished the top of the horseshoe contact points and made sure there is no roughness on the tabs so they can roll smoothly. I bet your horsehoe standoffs were bent, take some smooth face pliers and flatten them out and leave them unbent, they need not be bent, skip that step in the manual, it is not needed.

JFYI, the DA had two different nozzles. The early nozzle had a smaller orifice. Later the orifice size was increased. I can tell the difference between the nozzles in use, it does make a difference. You can only see this when comparing them visually or of course measuring them.

I have done numerous experiments, made larger venturi nozzles, increased the size of the hookah port and radiused the edges, I have drilled the nozzle holes (not the volacano), I have drilled holes in the horsehoe to reduce it's weight, I recently made a venturi shield and I have no conclusions on that yet. Messed around with various IPs and played with the IP diaphram materials. One place a little bit of lubricant seems to help is the button that rides on the IP diaphram.

If you have a Pico DA I bet it has the small orifice nozzle.

Disclaimer: Everything I said and have ever said will cause your death, only crazy people would dive with antique regulators.

Important: Never, ever, breath off the horn, especially on a single stage reg like a Mistral, it just might kill you for sure. You must install a hose and mouthpiece with valves in place. Remember the venturi, espcially on a Mistral, is very powerfull. On a single stage the force behind that nozzle is tank pressure---TANK pressure. When you breath off of a single hose the exhaust valve or port is open and available to relieve pressure and as well, compared to a double hose, all single hose regs have relatively weak venturis. A double hose like a DA/RAM/Mistral etc have powerful venturi action to assist breathing through the long hoses. Putting your mouth directly to the horn points that venturi straight to your lungs with NOTHING to relieve it except a blowout in the wall of your lungs--you have been warned!

N

 

[halocline]

I messed around with the height of the seat holder a little today. As you guys have said, there really are only 2 or three holes (two thirds-one complete revolution) before the seat holder is too high to be held in place by the lever supports. I got mine as high as I could, thinking I'd start with the lightest orifice pressure possible.

This does change the geometry of the reg a little in that the lever will now contact the tabs at a slightly different angle. I have no idea if that's an advantage, disadvantage, or has no appreciable effect.

I think improvements could be made by dealing with friction areas in the whole lever mechansim as Nemrod has been working on. When I get the new diaphragm and put the reg together for keeps I'll spend some time cleaning up the supports and the tiny rectangular holes in the horseshoe. That's a place a drop of Christolube or silicone might come in handy. I like the idea of polishing the edge of the diaphragm tabs.

An interesting experiment would be to fabricate thicker-based horseshoe supports so that there is a wider range of adjustment in the seat holder height. Another place for messing around would be the washer/lever joint. Anything to make the response of the lever more accurately and consistently transferred to the poppet stem would theoretically improve the ability to get the reg tuned.

Now, if you think Nemrod has a disclaimer on his post, check out mine: I have been working on double hose regs for a total of two days. Anyone who pays any attention to my ideas about them is a certifiable lunatic.

 

[Luis H]

Dont set the lever to high, I am thinking around level to the can. If it is to high the angle to the tabs on the diaphram are acute and it increases the cracking force.

N

I agree with everything that Nemrod posted except for this statement. The statement is correct in theory, but at the working angle and angle range it would not make any practical difference. It would make a difference if it started to be too high of an angle, but in this regulators that will not happen.

With the new silicone diaphragm I tend to set the horseshoe lever height somewhat above the edge where the diaphragm sits. I like the lever to be basically touching the diaphragm taps at all time. It seems to work well.


Polishing all the matting and sliding surfaces is not a bad idea, but the most important would be to make sure nothing is binding. In particular I am referring to the horseshoe support hinges with the horseshoe.

The separation and location of the hinges has to be adjusted to make sure the horseshoe moves freely. It is possible to place the hinges too far apart or too close together where they bind with the small rectangular openings in the horseshoe.


I have never needed to unscrew the seat holder more than one full revolution, but if I had to I am not convinced that the locking wedges are really needed. If I was concern I would use a bit of nail polish on the edge.

I am working on some other ides to simplify the adjustment of the second stage, but I need to test a few possibilities. More about it later.


One big advantage of this type of double hose regulator is the huge mechanical advantage supplied by the diaphragm. I think I posted some calculations, but I should probably post the entire calc sheet in the technical section of VDH.

What this mechanical advantage does is that any minor friction forces or indentation forces on the seat tend to be insignificant. I am not saying not to bother playing with it, but at the end of the day when you test it with a Magnehelic a lot of it just doesn't seem to make much difference.

Fine tuning the regulator can be actually fairly easy since some of the minor friction forces become very insignificant, but it is never a bad idea to make sure they are in fact insignificant.

 

[captain]

Years ago I played around with the seat holder and could not see any advantage to it. Taking compression off the spring just makes free flow occur at a lower IP. Basically you are balancing spring pressure against IP. Lower spring pressure = lower IP. Higher spring pressure = higher IP in the end it is 6 of one and half a dozen of the other. I prefer the higher IP.
In some single hoses such as the Scubapro R109 there is no adjustment nut so the volcano orifice is adjusted to set the lever height. The Conshelf VI and Voit MR 12 I have both a fixed volcano orifice so a nut is needed on the poppet to adjust lever height just as the DAAM or RAM
Screw the seat holder all the way in while maintaining one hole pointing down the inhalation port. Put it on a tank with 300 psi. Crank the IP up until it barely starts to free flow without the horseshoe installed than back off the IP until it stops. Adjust the horseshoe lever height and if the free flow starts again when the diaphragm is in place lower the horse shoe a flat on the nut at a time until it stops. IP should end up at 130 to 145 at 300 psi tank pressure with no free flow.
As Luis said be sure the horseshoe is free on the supports and the ends of the horseshoe are centered on the diaphragm tabs.

 

[Nemrod]

Years ago I played around with the seat holder and could not see any advantage to it. Taking compression off the spring just makes free flow occur at a lower IP. Basically you are balancing spring pressure against IP. Lower spring pressure = lower IP. Higher spring pressure = higher IP in the end it is 6 of one and half a dozen of the other. I prefer the higher IP.
In some single hoses such as the Scubapro R109 there is no adjustment nut so the volcano orifice is adjusted to set the lever height. The Conshelf VI and Voit MR 12 I have both a fixed volcano orifice so a nut is needed on the poppet to adjust lever height just as the DAAM or RAM

That is kinda where I am with the seat holder in my thinking as well. I am also known to just bend the lever to suit, especially with my MR12IIs. I try not to bend on my double hose parts just because they are hard to come by but, well, just never know what might be under the hood.

I am going to stay with the other part, maybe I don't explain things well. If the horseshoe is kept in the sweet spot the diaphram tabs essentially roll on the horseshoe but if horseshoe is to high the tabs tend to skid and slide on the horseshoe which increases the cracking force and reduces sensitivity. Think of an arc, with the neutral point of the arc having the horseshoe half way depressed by the diaprhram. The top of the arc would be with the LP seat seated and the horseshoe resting at full extension and the other end of the arc being the limit of depression of the horsehoe. I like to set the horseshoe so that the center of the arc where the direction changes, looking down in plan view, is to be centered on the diaphram tabs. This adjustment results in the least amount of relative motion, in plan view, of the diaphram tabs in relation to the tops of the horsehoe fingers. If the horseshoe lever is to high the relative motion increases, it is geometry. The amount of adjustment we are talking about here is not make or break, it is just a goal and it does seem to make a small difference in overall responsiveness. AND, if need be after doing what Captain said, I bend the lever to achieve what I said---lol.

How do I have a feeling Luis is going to beat up on poor Nemrod some more, lol, love ya Luis .

N

 

[Luis H]

Years ago I played around with the seat holder and could not see any advantage to it. Taking compression off the spring just makes free flow occur at a lower IP. Basically you are balancing spring pressure against IP. Lower spring pressure = lower IP. Higher spring pressure = higher IP in the end it is 6 of one and half a dozen of the other. I prefer the higher IP.
In some single hoses such as the Scubapro R109 there is no adjustment nut so the volcano orifice is adjusted to set the lever height. The Conshelf VI and Voit MR 12 I have both a fixed volcano orifice so a nut is needed on the poppet to adjust lever height just as the DAAM or RAM
Screw the seat holder all the way in while maintaining one hole pointing down the inhalation port. Put it on a tank with 300 psi. Crank the IP up until it barely starts to free flow without the horseshoe installed than back off the IP until it stops. Adjust the horseshoe lever height and if the free flow starts again when the diaphragm is in place lower the horse shoe a flat on the nut at a time until it stops. IP should end up at 130 to 145 at 300 psi tank pressure with no free flow.
As Luis said be sure the horseshoe is free on the supports and the ends of the horseshoe are centered on the diaphragm tabs.

I have been adjusting the seat holder to take compression out of the spring mostly because I have encounter what seems to be some very stiff springs. I would also not bother making this adjustment if the IP required for a free flow was in a reasonable range.

I like to set the second stage so will start free flowing around 160 psi (or maybe even a bit less). That way I can adjust the IP to 140 to 145 psi (or even lower at times) and the regulator will breath well.

If the second stage doesn't start to free flow until the IP is 170 psi or even higher, it will be a hard breather unless I run a very high IP. That is OK unless you ever want to add other LP attachments, which I often do.

I had a RAM that needed an IP of around 165 psi to breath well. It worked, but I prefer to adjust them at a more conventional IP.

That is kinda where I am with the seat holder in my thinking as well. I am also known to just bend the lever to suit, especially with my MR12IIs. I try not to bend on my double hose parts just because they are hard to come by but, well, just never know what might be under the hood.

I am going to stay with the other part, maybe I don't explain things well. If the horseshoe is kept in the sweet spot the diaphram tabs essentially roll on the horseshoe but if horseshoe is to high the tabs tend to skid and slide on the horseshoe which increases the cracking force and reduces sensitivity. Think of an arc, with the neutral point of the arc having the horseshoe half way depressed by the diaprhram. The top of the arc would be with the LP seat seated and the horseshoe resting at full extension and the other end of the arc being the limit of depression of the horsehoe. I like to set the horseshoe so that the center of the arc where the direction changes, looking down in plan view, is to be centered on the diaphram tabs. This adjustment results in the least amount of relative motion, in plan view, of the diaphram tabs in relation to the tops of the horsehoe fingers. If the horseshoe lever is to high the relative motion increases, it is geometry. The amount of adjustment we are talking about here is not make or break, it is just a goal and it does seem to make a small difference in overall responsiveness. AND, if need be after doing what Captain said, I bend the lever to achieve what I said---lol.

How do I have a feeling Luis is going to beat up on poor Nemrod some more, lol, love ya Luis .

N

Gee... are we a bit sensitive. I never intentionally "beat up on poor Nemrod".

I can see that adjusting the horseshoe can affect the point of contact on the diaphragm tabs. That is an interesting point. Although related to the angle adjustment, the effect you are referring to is not just from the angle change. I have never notice it being supper critical, but I am not saying there isn't an effect, just that I haven't notice it.

In that same subject, the amount of play in the location of the horseshoe supports can change the end location of the horseshoe. I am always careful to adjust the distance between the horseshoe supports so the horseshoe doesn't bind, but have never bother to check their precise final location towards the center of the main body.

 

[jbrians]

I do remember Sea Hunt (in fact, I just bought the entire 128 episode DVD set) and Mike Nelson wore a wetsuit and a massive weight belt (by appearance). No BC, no octo, nothing else except a harness and tank/regulator. I'm assuming that SOME of the photography wasn't faked so it must have worked.

Richard

What you see on sea hunt isn't totally transferrable. Most of the underwater scenes were shot in maybe 20-30 feet of water with a full thickness wetsuit. 20 more feet of depth and half of the weight would be coming off. They also probably wanted him negative to make it easier to shot scenes without him popping to the surface if he stopped moving. There is a lot of standing around between takes, as it were.