Mechanical BC's - is it possible?

[Couv]

Anybody remember the Turtle backpack? You put air into the hard shell backpack and it served as your bc. There was no bag so when one did a head first dive all the air and positive buoyancy was lost. This was a "feature"....automatically dumped air when the diver wanted to decend.

 

[spankey]

it seems like a good idea, but need to ask. If it was simple and/or possiable why dont submarines use a system like this? By your theory this would stop the bubble noise subs make venting their balast.

 

[FoSheZZie23]

Im not an expert but i dont think that increasing or decreasing pressure in a cylinder would do anything at all to bouyancy

 

[fisherdvm]

Im not an expert but i dont think that increasing or decreasing pressure in a cylinder would do anything at all to bouyancy

Only if volume of air is changed - then the bouancy would change. It is very hard to get air to be more dense than water. Once you compress it enough, it would be the equivalent of liquid nitrogen (about minus 200 degree Kelvin).

I think we are talking here about using pressure to change the volume - whether it is using pneumatic or hydraulic pressure - vs. mechanical means - ie screws, and gears.

 

[bperrybap]

So lets just say it could be done and was dirt cheap to make
and was a very low cost option for your BC.
(And to keep it simple, ignore any failure issues)

Would you use it?
Would it even make diving easier or more pleasurable?

When I'm diving, especially when I'm taking photos, I'll
use breath control to get into position and then
also use it to "float" up out of the way once I'm done.
This allows me to get in and out of position without touching
things or stirring things up.
Doesn't matter if I'm horizontal or even head down vertical
peering up under something very close to the bottom.


I would find it extremely frustrating to have a BC compensating
for my breaths all the time.

The "magic" would be how to integrate the automatic buoyancy
system and the divers desire to ascend/descend.

Now perhaps if it had a few different modes.
Auto vs manual.
Or perhaps a mode that should get your buoyancy compensated
to where breath control should be able to be used. i.e. keep
you from being too negative or too positive.

I tend to think of something like this like ABS brakes.
Yes it could be done, Yes it will cost extra money.
It can correct poor or incorrect human behavior.
A highly trained human can usually outperform the automated
system. Failures can be deadly. And those that get used to and
depend on the system are much more dangerous and more
likely to be involved in an accident when not using the system
than those that have never used it.

I would think a simpler device might be to have something
that would stop runaway ascents or to prevent you from
descending below a certain depth rather than trying
to maintain your ideal buoyancy.

Just some quick thoughts.

--- bill

 

[Don Burke]

it seems like a good idea, but need to ask. If it was simple and/or possiable why dont submarines use a system like this? By your theory this would stop the bubble noise subs make venting their balast.

Submarines only vent air from ballast tanks on the initial dive from the surface, so bubble noise is not an issue.

 

[Stoo]

I think USD or DACOR toyed with this concept about 25 years ago, with mixed results. As I recall, it worked OK, but there really wasn't any advantage to it, and it was a pain to pack and haul around. I don't really remember the details other than it was black, about the size of a small dive-pack and had a couple of valves sticking out of it.

Personally, I don't find it especially "challenging" to use a BC. Isn't this an overly complicated solution to a non-problem?

 

[Thalassamania]

Here's some information on neutrally buoyant systems.

 

[String]

Probably a one way bleed valve that maintain constant pressure greater than water pressure will be needed.

You mean exactly like a drysuit shoulder auto dump valve.

 

[Drewski]

Here's a picture of a Dacor Nautilus CVS:

We tried to sell these in the dive shop I used to work in "back in the day." They were a limited production run and if memory serves they were a spinoff of technology developed for the USN. The actual units looked MUCH better than the one pictured, they were all black and shiny and actually looked pretty COOL. They were, however, EXPENSIVE. I want to say $700+ in 1982 dollars.

The stuff you see in this photo is typical of the set-up. First, NO doubles, singles only. You're looking at the tank side. The diver side had straps. The inflator system is on the left (big hose). The dumps are on the top and bottom right. The "strap" and handle looking thing you see on the right is an emergency weight release system. The unit had "on board" lead, if memory serves it was lead shot.

The "concept" of what Dacor created was more a "constant buoyancy system" instead of a constant "volume" system. The unit was designed to keep you neutral after you "set" it at depth, kind of like a drysuit vent valve.

The reason why it failed as a product was because is was RIGID. Packing and flying with this thing just didn't work. Also, with all the moving parts, maintenance, especially for use in salt water, was expensive.

We only had and sold ONE.