Measuring cracking pressure

[herman]

With Bryan adding new DH mouthpieces I cured my manometer to DH reg interface problem. I bored a small hole in the back of an older (hard) straight mouth piece and installed a double ended hose barb into the hole. I then install the test mouthpiece in the place of the normal mouthpiece along with the wagonwheels or nothing if I am trying to isolate a problem, works great. I have done the same for single hose regs, I just drilled a hole in the side of an old mouthpiece and inserted a hose barb. For quick checks on both single and double hose regs I use a short piece of pvc tubing with a hose barb installed in it instead of a mouthpiece.

Imastinker, do a search on manometer. I posted photos of one I made and use a while back. I did recently add blue color to the water, makes reading it so much easier.

 

[Bluey]

Yep, that explains your readings.

Are you using a Magnehelic or a? I would guess you are using a Magnehelic.

With a full venturi flow the vacuum should go down once you establish flow.

Several of my regulator will drop very close to zero. A few of my double hose regulators will actually go past zero into positive flow if I suck just right.

I am using a U tube manometer.

The venturi assist only seems to kick in during quite high flow (very rapid inhalation).

In a series of gradually more rapid inhalations, the S600 cracks at about .6" then levels out to about .9 for normal to fairly strong breaths and starts to drop when I inhale extremely quickly.
It obviously will reach zero, or positive pressure eventually, as it free flows if purged.

This agrees with my experience that the venturi assist has no real effect at shallow depths when breathing normally, and suggests that the reg may in fact breath easier at depth than in shallow water.

As a comparison, my Conshelf SE3 cracks at about 1.1" and the effort keeps increasing up to about 1.6 for strong breaths.

Bluey

 

[DA Aquamaster]

Personally the only thing I ever found to be useful with an adjustable flow vane is settign it to the minimum position when using it as your secondary/octo. As it will help prevent a continuous freeflow on entry, etc.

One note on the S600 (and most other flow vane equipped plastic cased Sp regs). The flow vane is reversible and reversing it will increase the venturi effect. Off the top of my head I cannot remember what side is more or less, the flat side or the curved side. It was in any event one of the changes that seemed to creep in with CE norms and a desire to increase free flow resistance.

 

[Nemrod]

The water manometer is very accurate once set up. Using the food coloring in the water to turn it blue or red etc is helpful as as is a second set of eyes sometimes. Unlike a magnehelic, which is awfully coollooking, a water manometer really does not need calibrating other than marking a zero point and then sliding your "ruler" to match zero.

More than likely the only three people on this board who have hooked a magnehelic or manometer up and actually measured any of this rather than taking the word of the scuba rags and urban legend are the three that posted, maybe some of the guys in the DIY forum as well. It is a real eye opener when you hook up the latest super duper plastic fantastic and it don't do any better than a 50 year old double hose antique. We are simply up against physical laws and until we have electronic/chip control FADBC (Full Authority Digital Breathing Control) or electro servo controlled breathing systems we will be stuck with an approximately 0.5 inch cracking force plus or minus a bit.

N