What is the best BMCL orientation?

Scott

I know the answers will be quite subjective, but, I would like to hear the arguments for your preferences =)

So what is the most effective back mount counterlung design?

Low on the back, mid back, near the shoulders, going over the shoulders toward the front of the clavical.... running the full length of the back?

Kept near the spine, kept near the flanks, or spread across?

Inhale and exhale each confined to their own side, overlapping partially.. or each covering the entire width of the back?

paulraymaekers

first rule: CLOSE to your back!!
second rule: close to your lungs, but as you can not put 5/7 liter all at the closest point to your lungs, you have to devide the volume... so now you start to compromise.. :-)

paul

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www.rEvo-rebreathers.com

.... the earth is flat, Elvis is alive, and radial scrubbers give longer dwell time than axials...

Scott

Well.. here is my thinking...

for a swimming position near horizontal:

counterlung(s) sitting in the small of the back would have the least WOB based on hydrostatic pressure influences.... but worst due to the long path of the breathing hoses...

counterlung(s) contained very near the lungs, would need space to expand out away from the body, and as such, with any gas volume in them, would tend to attempt to seperate from the body, pushing toward the are of least pressure... So WOB due to hose length would be lower, but WOB due to hydrostatic pressure would be worse

A potential fix for the later example would be to have one face of the counterlung secured to the divers back, such that the entire counterlung would not 'float' to the far side of the case.

From my understanding from reading this board, if a single counterlung is used, with a BMCL position, percieved WOB is better if it is on the Inhale side. This however makes placement of a water trap difficult.

If a single counterlung is used on the Exhale side, depending on how the O2 Sensors are placed, you run the risk of condensation and flatout flood attacking them.

Overlapping counterlungs could cause a problem with one lung from restricting the other from inflating...

If the exhale is placed closer to the body then the inhale, then in theory, hydrostatic pressure (i think I am using the term correctly here), would tend to assist the flow of gas from the exhale CL, through the scrubber and into the Inhale CL. As the gas is moving from one CL to the other, I don't *think* that one impeding the other would be a problem while in this attitude.. HOWEVER, if the diver were to orient themselves face up for some reason, then the inhale counterlung would be under the exhale counterlung, and my get sucked flat and seal, preventing gas from moving from the Exhale CL to the Inhale CL.?.?


-Rambling done for now..

AD_ward9

The scientific and objective answers to your question is in the O.R. document: http://www.deeplife.co.uk/or_files/O...vC5_070810.pdf

This document explains the theory of CL hydrostatic imbalanaces, the practice, the measurements. If anyone knows a more definitive work on the topic, please post the reference.

One word of caution: ensure the CLs are free to move (do not trap them in a water column, otherwise the resistance will be very much higher).

Alex

Nad

Years ago, when I was playing with my HB I always had BMCL on the side just behind the shoulders, vertical.
The last experiment was to have CL free to move. I did use a Rescue Resuscitation Bag, with a T. This bag has an egg-shape and has a ring on one side and the hole on the other. The ring was fixed at harness and hoses mounted on the T. It had good WOB, I suppose just because of the position that was exactly under the arms, at the same lung level, in every position.
But it was just personal experiments then, like Paul say, you need compromises: I didn't have any safety factor with this kind of design, at least with the material and solutions I did use: CL too exposed, hoses routing a bit funny, etc.

Nad

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The Impossible is often the Untried

lof

Here are couple of pictures of my latest design. The T-pieces are pretty much in the same position as on the OTS CLs. The CLs are in loosely attached perforated cases along my side/back as close to lungs as possible. the wing is behind them. The WOB is very good in all positions (subjective). Photos by Corey Mearns.

Do not pay attention to hoses and cables it is all work in progress and will get streamlined





Look Ma, no bags

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Jakub
Golem Gear ShopKeeper
www.golemgear.com

decoweenie

Jakub,

Could you give some more detail pictures of your:

- MAV with orifice
- Secondary PO2 display

lof

As soon as I take them.
In our design the Orifice is separated from the MAV. That way if it plugs you just unscrew it and put in a new one. Or you just screw in one with the flow appropriate for the planned dive.

__________________
Jakub
Golem Gear ShopKeeper
www.golemgear.com

mountain diver

looking forward to the finished product.








all the best.