Mounting tanks upside down

[devjr]

Yes, they did a pretty good job of responding to that bizarre post..... bygones. However, I saw no direct explanation offered to Larry as to the variations of breathing effort experienced by the diver. As we know from basic SCUBA the sensory node for water pressure is the regulator 2nd stage, the diaphragm to be specific. The demand side of the breathing cycle is the center of the diver's lungs. Thus, the breathing or "cracking" effort is the sum of the mechanical resistance of the second stage valve and the water pressure measured by the distance between the 2nd stage and the diver's lungs. Water pressure is additive (hard breathing) when the diver is vertical, or in the horizontal position with face up. It is subtractive when the diver is in the inverted position. It is neutral when the diver is horizontal and face down.

In a nutshell, anytime the lungs are below the 2nd stage they are working against greater water pressure than what the 2nd stage regulator diaphragm is seeing. The converse is also true.

 

[Uncle Pug]

Originally posted by devjr
Yes, they did a pretty good job of responding to that bizarre post..... bygones. However, I saw no direct explanation offered to Larry as to the variations of breathing effort experienced by the diver.

Actually I had that in my post dev but I edited it out because I thought that I had already whacked enough and needed to tag out and give someone else a turn....

But now that you have tagged out I will add back in my coup de grace... for our own NetDoc in a thread long long ago and far far away....

This is why horizontal is better for decoing... less breathing resistance ... Peter.... (I know you are watching silently in the audience ut: )

 

[Laurence Stein DDS]

Whew! You beat the c--p out of me. I will admit to being bad at math at 6 in the morning if you can admit you can't read. I am NOT an instructor. Put downs kinda p--s everyone off don't they!

devjr was alot more kind. Remember this isn't a pi--ing contest. At least a reasonable explanation was given to the difficulty of breathing inverted...as opposed to the put downs you sent.

I contacted a really great scuba shop locally. First, the position of the first and second stages DOES affect breathing. Both the repair staff and an instructor said the same thing. Maybe you want to chew them out too. Next, inches of water used to measure cracking pressure and calculate the work of breathing is still a measurement of pressure...as in pounds per square inch. It can be converted to pounds per square inch This is NOT apples and oranges. It is simply a convention used for this type of measurement. Keep your "noise" for your electrical, radio and stereo measurements.

I know you will argue with that statement so before you do, go to your scuba tech and ask like I did. They indeed know more than me and possibly you too.

Now devjr's answer made the most sense. No put downs, no noise. Just a very logical answer that even I could understand. As a matter of fact, I believe devjr's answer is the correct one and I stand corrected with appreciation.

Finally, back to the original question about inverted mounting. I can just see any one of us trying to suit up in heavy seas with the valve bouncing on the seat or deck. Maybe THAT is why someone had the good sense to put the regulator on top! The fire department's units are somewhat lighter (I was surprised to find out that many are made of spun fiberglass and resin!) than ours and they are put on differently--commonly from overhead and nearly always on solid ground. These units have straps only, and no BC attached--they can be swung around the back kind of like putting on a jacket. The inverted position certainly is less likely to catch on obstructions. Their units are not used for respiration under water so no need to worry about pressure differences.

I have no doubt that the inverted set up is used. I've seen it. I know Couseau used them at least for a while and as was pointed out the Royal Navy does so ( I have no reason to doubt that statement). I suspect that they have made certain changes and adapations to allow the units to be used easily and successfully like this. However, there must be a logical reason why the majority of dive set ups are valve up.

I didn't see you, roakey, coming up with any logical reasons.

Thank you very much, devjr. It was a pleasure to read your answer.

Larry Stein

 

[roakey]

Originally posted by Divesherpa
Roak and Uncle Pug are right on as usual(excluding DIR discussions)

Whattya mean "excluding!" I'm ALWAYS write!

Roak

 

[Uncle Pug]

Originally posted by Laurence Stein DDS
As a matter of fact, I believe devjr's answer is the correct one and I stand corrected with appreciation.

Larry... congratulations to you for being a good sport...

 

[devjr]

I never fail to be in awe at the ability of this simple device, the Cousteau Gagnan regulator, to not only supply air on demand, but also to provide the air at pressures which are exactly compensated for water depth. Think about it, if the demand valve's compensation were off by more than a tiny fraction it would not work well, or even be potentially dangerous. If this confluence of engineering and physics did not exist we would have had to wait for the invention of electronic sensors, the computer, and complex servo controls to imitate it's ability.

 

[Laurence Stein DDS]

Just want to thank Uncle Pug and devjr for their courtesy. You are gentlemen.

Thank you.

Larry Stein

 

[pipedope]

As someone who has used tanks valve up and valve down, I can tell you that *I* can't tell any difference in breathing effort. If you can tell the difference then you have a more sensitive sucker than I do.

In commercial diving we generally rig our bailout bottle valve down to keep the first stage from hitting the back of our diving helmets. There is no difference in effort breathing from the surface supplied umbilical or from the bailout bottle.

I also frequently use a scuba bottle with first stage on the surface and a *long* hose (about 75') to the second stage. No problems breathing this rig either. This rig is very handy when I need to get into a pipe that is too small to allow me to wear *any* tank in any position.

While there is a theoretical difference, it is too small in practice to matter to any human diver.

 

[Uncle Pug]

Originally posted by pipedope
This rig is very handy when I need to get into a pipe that is too small to allow me to wear *any* tank in any position.

Hey Michael... I was wondering...
Do they flush the sewage out with fresh water before sending you in?

 

[pipedope]

UP, that would take all the fun out of it.

Actually I rarely dive in sewage pipes or systems as most of those jobs are too short and too anoying to be worth rigging up all the decontamination equipment needed.

I dive in LOTS of storm water drain pipes. Here in Florida the water table is so high that most storm water pipes are full of water all the time. If a contractor needs to work on the pipe or pump out the retention pond they call us to put a plug in the pipe. Sometimes the pipes are as small as 18", lots of them are 24". After a while at this stuff a 60" pipe (5 feet in diameter) seems like an OW dive.