"last" DA Navy approved.

[Ron]

So I picked up that DA Navy approved that was in the store, and turned it into the regulator that I would have cobbled up in the Navy. It has the last style of DA body, where it has the unmachined hookah port of a DA aquamaster, but the venturi-less second stage of the standard DA Navy. The body is also oriented like a DA aquamaster, down the intake horn, instead of 180 degrees out like a DA Navy or broxton. I put a band clamp and nylon clamps on it, because I have seen pictures of several like this and because no squid in his right mind would have used c clips and tinnermans if he had any say in the matter (or at least this one wouldn't have). Lastly, I just finished installing the lower spring rate springs for the second stage lever that contributes to easier breathing. So now by the end of a tank this reg breathes right around .8" on the old magnahelic.

Here you go boys:

[usddude]

You did better than well my friend. I never would have thought a horse shoe reg could breath that well. I wish I would have kept the one I had now....but it had the 2nd stage flipped on the other side. Bryan certainly put you into a nice setup..along with some of your own skills.....congrats...

Steve

[Ron]

I'm telling you man, it's those second stage springs. I had the OEM springs in earlier today, and the freaking thing would breathe at 1.5" with a 500 PSI supply pressure and if I would jack IP any higher it would freeflow. I'm not a mechanical engineer, but I think they put springs in the second stage that were a bit too heavy on the spring rate. I can't remember where I stashed it, but I bugged Douchebag a while ago and he helped me figure out how much force the springs were actually exerting to keep the second stage seat mated against the orifice and it was too much. He actually made me an excel spreadsheet to explain it with formulas and everything. That guy is a freaking genius. He helped me pick them out and now all my early regs breathe wonderful. They still don't have a venturi assist, but you barely miss it with good cracking pressure. I'm not sure why, but the line between an unstable second stage and crappy cracking pressure are like touching each other with the factory setup on the early regs. We put silicone hoses on everything, why not better springs? I almost stenciled my intials on the top can, but Bryan did such a nice job on this one that I didn't have the heart to deface it with my own name.

Also, I cannot tell any difference between my broxton, which has a one piece hose and the body turned 180 degrees, and this one. They both breathe the same on the magnahelic. So I'm not sure that the body location makes any difference with no venturi assist. Also, the one piece hoses do not seem to make the regulator breath any differently from my experience. They do require fighter pilot like maneuvers to clear though, which makes people look at you like you are a nut.

[antique diver]

That reg looks great and sounds like it will be a good performer. Have you had it in the water with the new springs?

Now the important question is: how do I obtain some of these magic springs? I have several nice regs that could benefit from this advancement.

[JES]

Ron, Thanks for the report. Nice work!

[Bryan]

Ron if you would like to do a writeup with more pictures and details I will post it in the technical section for easy access for everyone. Also if you want to send me the part number I will put the springs in the store inventory with a link to your writeup if other divers want to experiment over the long winter months that some of you have to endure..

[Ron]

Bryan,

I will work on one today and tomorrow, and then post it here in this thread. I will also email you the part #'s.

Bill,

I dove my broxton several times with this setup. It works great, and I had it as deep as Portage Quarry gets (what is that maybe 60 feet-ish?) and it worked fine.

[Ron]

This procedure assumes that you know how to rebuild a 2 stage Aqualung, and that you possess the minimum amount of tools to do so. I make no claims, warranties, or promises that you will not damage your equipment or kill yourself, so following these procedures implies that you do so at your own risk.

Required materials:

-Original DA "Aqualung" parts breakdown (available in download section).
-Custom springs, second stage, quantity of 2.
-Micrometer.
-Magnahelic or manometer.
-Compressed air tank, containing about 500 PSI of air.
-A first stage nozzle with NO creep.

Procedure:

Once your regulator is as disassembled as you prefer, remove the hinge pin securing the two second stage screws (index #23). Remove both hinge screws (index# 22) and inspect for wear in hinge pin holes. Replace if at all worn. Remove horseshoe (index# 21) and both springs (index #20). Set aside springs in a bag, and label them to prevent mixing them in with your new springs.

Install new custom springs. You will notice that they have a lower spring rate then the stock ones. This is a good thing. Install both springs (#20), position horseshoe lever in place over springs (#21), and screw both screws in all the way (#22). If the screws are bottomed out and they are not aligned, then use your screwdriver to align them. Now, turn each screw out 1.5 turns.

Take your hinge pin (#23) and compare it to a known straight edge. Both ends of the pin must be straight where they penetrate the screws of the second stage. If this is not the case, then make it so using needle nose pliers.

Install your hinge pin (#23) through the second stage screws (#22), but do NOT bend the pin yet. Using the micrometer, take a measurement of the distance between the horseshoe lever (at the screw) on both sides. The distance between the horseshoe lever and the body should be about .080 inches ON BOTH SIDES. If this is not the case, then adjust each screw alternately a half turn at a time until this is so. Once the screws are set correctly, then you can bend the hinge pin (#23) to secure it to the screws. Ensure that once the hinge pin is bent that both sides of the lever are still at .080 inches. If you bent the hinge pin (#23) too far, then bend it back a little bit to ensure that the distance between the horseshoe lever and body are as close to .080 inches as possible.

Assemble the rest of the regulator if you have not already done so. The regulator should be fully assembled, with the top can and diaphragm removed.

Place the regulator on the tank as specified in the required materials. Charge the regulator. Adjust the first stage until the second stages begins to barely hiss air, then back it off 1/8-1/4 of a turn. Turn the air off, and purge the regulator. Charge the regulator again and operate it several times. It should not leak from the second stage. Wiggle the horseshoe lever from side to side (without actuating it), it should hiss when you do this, but just barely.

Finish assembling your regulator to a ready to dive state. Ensure that your diaphragm ears are bent at such an angle to most efficiently contact the horseshoe lever. This is more important on these regulators than it is on the aquamaster as the lever sits much lower in the can.

Place your fully assembled regulator on the tank as specified in the required materials. Charge the regulator. Place the mouthpiece in your mouth, and snake the inlet tube of your magnahelic in your mouth without the magnahelic mouthpiece installed. Using your lips as a seal, draw a breathe on your DA series regulator with the supply pressure at about 500 PSI and the magnehelic tube in your mouth. The regulator should begin to crack at .8" of water as indicated on the magnahelic. If this is not the case, then increase or decrease intermediate pressure as required to achieve this state.

Enjoy your regulator, because now it does not breath like an iron lung. You will hear a clicking sound on inhalation. That is the sound of the diaphragm traveling downward and contacting the horseshoe lever, as it sits lower in the can than an aquamaster. This is normal.

[eskimo3883]

Hi,

Reading about Ron's spring replacement in his DA NAVY design got me thinking if USD missed this or was another explanation possible. In my younger days I was always told my ski bindings needed rebuilding because of spring fatigue. Later I was taught this was not so because steel was elastic almost forever as long as it is not overly stressed. I recently wrote to the head of the “Spring Manufacturers Institute, Inc” about 50 year old springs under mild compression and he suggests the springs “might be out of calibration from taking a set.”


Dear Sir,
I am a member of a group that collects and refurbishes very old SCUBA regulators (~1942 – 1962). The goal is to preserve the original design as a functioning device in “as new” condition. These models were all designed using spring pressure to balance air tank pressure. The correct spring balance makes a design breath with little effort. Most want to rebuild with all original parts. Is this wise? Should we expect properties of springs to remain as they were or should we expect a spring under mild compression for 50 years to age and hence change its original properties?

His reply:

I’d be a little more with concerned with corrosion of the older springs and eventual failure. For a buck or two it would be wise to replace the spring – and yes they might be out of calibration from taking a set.

Luke
Technical Director
Spring Manufacturers Institute, Inc.
2001 Midwest Road, Suite 106
Oak Brook , IL 60523
Phone 630.495.8588
Fax 630.495.8595
http://www.smihq.org

[captain]

I am sceptical that a lower spring rate contributes anything to performance and may in fact degrade it.
A lower spring rate has to be compensated for by a lower IP to prevent a free flow condition. Pressure is directly related to flow through a fixed orfice so a lower IP could lower flow capacity.

What is the IP.

I experimented with lower spring rates on a DAAM and came to the conclusion it provided no improvement in performance.

In a regulator like the DA Navy without a venturi effect it could lower flow even with a low cracking pressure which basicly means nothing because without a venturi assist, your lungs have to do all the work to keep the flow going.


To quote Bryan. I'm just saying.

[Ron]

I suggest if you are skeptical that you buy some of the springs that Bryan has and try it. You will not be disappointed, or at least you will have feedback on why you are. Math dictates that the reason that the cracking pressure is what it is on the standard DA Navy is because of a combination of the mechanical advantage of the lever, the surface area of the diaphragm, and the force the springs/seating surface exert against the orifice to keep the second stage from opening (amongst other things, I'm not a PE give me a little leeway). If you change one of the variables, then you change the equation. Placing in a slightly (marginally, in fact) lighter spring only serves to lessen the cracking pressure by changing one of the variables. In any event, it certainly breathes better than they do stock. My broxton and DA Navy both have this configuration. You can ask Roger or Jim, they have seen me dive both of these regs to 100 feet at Blue Grotto...they work. I do not have a way of testing IP on either of these regs but judging by the amount of spring tension on the first stage I would guesstimate about 130-135. Still, to each his own. If you don't like it, then don't do it

I agree that the venturi effect lessens inhalation effort over a period of seconds (which is visible on a magnahelic), but lowering initial cracking effort still reduces the amount of effort your diaphragm must exert to generate enough negative pressure to cause the second stage to open. I also agree that I do not have a flow bench, which would be helpful. This is kind of like tuning a car by the "butt dyno". At 100 feet my lungs tell me I have plenty of air if I gasp really hard, and I cannot overbreathe either one of my DA series like I can virtually any early single hose (aquamatics, for example). So I guess I feel pretty good with it, though I do not expect everyone to do so. It is definitely better to me than the 1.5" of cracking pressure it had when I got it, which made me never use it. So I guess if it becomes more useful to me then that counts for something.

Sorry I took so long to reply, I don't really follow things on here as close as I used to.

[antique diver]

Captain and Slonda:
You both make interesting and logical points about the spring subject! I would have thought that simply increasing the pressure would be the equivalent of using a weaker spring. But now I see it is definitely more complicated than just any one component or force out of the several in play here.

I discovered something interesting yesterday on a Voit single hose that led me to believe this may be more complicated than just raising the pressure. I was trying to get a nice Titan II to breathe a little easier by raising the IP. I was thinking I would use the technique of just raising the pressure until it leaked some air, then slightly back off. I also had a gauge on the low pressure side to track my changes.

At about 135 psi IP the cracking effort was about 1.6". I raised the IP all the way up to 170 before it leaked, backed off to 165... and the cracking effort had only dropped to 1.4". I was surprised that IP would go so high without a leak, and even more surprised at the low degree of improvement in cracking effort.
Those two observations led me to believe that it might benefit from a weaker spring. I'll be trying that when I can come up with a few different springs that will fit.

I am also looking forward to testing some of my double hose regs with the slightly weaker springs. The results of some of my testing isn't always what I expect to find, but this is fun stuff!

[captain]

OK, I throw some wood on the fire. I have the exact same DA, stub hookah port, 2nd stage located on the same side as the inhalation horn. I put it together about 4 years ago with all original parts except for new HP diaphragm, new LP seat and silicone LP diaphragm.
I set the IP at my usual 135 on a 300 psi supply and did my usual final tuning. I don't have a Magnehelic but I do have a 0 to 3" H2O U tube manometer. I can't recall if I checked the cracking pressure at the time but it has been a fine breather. I just hooked it up to my manometer and on a 300 psi supply it cracks at between .7 and .8 inches H2O.
Another thing I have found is that DA and Broxton type horseshoes seem to be more sensitive to diaphragm to horseshoe alignment than DAAM's and RAM's that have the long rounded horseshoe contact surface compared to the narrow sharp edged contact point on the DA. If the diaphragm tabs are not centered and perpendicular to the horseshoe then tend to honk and be somewhat erratic on inhalation.

I'm just saying.

[antique diver]

There must be a lot of variation from reg to reg on spring rates, other tolerances, etc to explain why one stock reg works so much different than another. Of course the technician's skills are another important variable too!

[antique diver]

Well, I have been waiting to see if someone was going to jump in and mention all the successful modern regulators with the adjustment knobs... they just vary the spring tension you know! Isn't that what we are wondering about here? (granted there are some adjustments that just vary the venturi, and some regs have both)

The ones that I am familiar with work quite well at varying the breathing effort at a fixed intermediate pressure. I have worked on many (and own a few) by Scubapro, Apex and some others that I thought worked darned well through a range of breathing efforts that could be adjusted from easier than I liked to more effort than I liked.

It's hard to argue with the performance of some of these regs. Maybe that proves something about spring tension at a given IP? I look forward to some polite but informative comments.