Re: [PSUBS-MAILIST] Ambient pressure sub hardware

[SFreihof@aol.com]

Pierre (Freezing in Canada?  Come visit me in Ft. Lauderdale... e-mail me offline if interested);

What you are describing is a demand regulator, originally designed in 1942 by Emile Gagnan and Jacques Cousteau.  That is what a scuba regulator is, and that is what it does.  The air chamber is separated from the water chamber by a rubber diaphragm.  When water pressure exceeds air pressure,  the water pressure deflects the diaphragm, which opens an air valve and allows air to flow until equilibrium is established and the air valve closes.

When air pressure exceeds water pressure, a simple flapper valve opens and exhausts the air into the water.

This system is reliable, simple, well tested, inexpensive, and readily available.  Why re-invent the wheel?  The only concern I can see is flow rate, which can limit descent rate.  This can be alleviated by using multiple (e.g. redundant) systems, which is almost mandatory for safety anyway.

Plug the regulator(s) into the keel of the sub where the water pressure is greatest.  If the keel is pressurized to ambient, the upper portions will be progressively above ambient by about 1/2 psi per foot above the keel, so there is positive pressure on the hatch seal, if you have one (the Sport Sub doesn't).

I'm no engineer, but I think I've got it figured correctly.  Will somebody please tell me if I'm missing something???  Does anyone have anything to add???

Stan
2 man Ambient Dry
Ft. Lauderdale

In a message dated 12/5/02 6:05:41 PM Eastern Standard Time, pipo305@hotmail.com writes:

> For my part, I'm looking for something cheaper. I have the idea of using a 
> double rods pneumatic cylinder. (One rod at each end = same force on each 
> side of the piston). One side of the cylinder will be outside water, the 
> other side will be ambient pressure. The difference between those two force 
> will move the piston one way or the other. I will install a mechanicaly 
> controled valve on one end. When the pressure inside the sub is 
> outside+Xpsi, the piston will go back toward middle an close the valve. 
> Sound simple and cheap. At the other end of the piston, the samething with a 
> valve that will exaust pressure with a one way valve of course.