Hello
Rick
I'm
struggling with your ambient regulator design slightly as to where the regs will
be mounted with regard to external water pressure and equalised internal
pressure. Do you know what pressure difference you require to allow the
demand valve to open. I know what you mean about the 2nd stage adjustment,
my Apeks regs have the same, but if the reg mouthpieces are open in the
same compartment as the diaphragm on the front then there is no pressure
difference acting on the lever within the reg and i can't see how it will open.
Also if the diapragms are located in a compartment at external pressure while
the mouthpieces are within the cabin, can the structure of the sub hull cope
with the increased pressure on the hull until the internal pressure has
increased to equalise or will the pressure equalise by compressing the cabin
hull.
Sorry,
I'm sure I'm missing something with your design but I'm beginning to think about
an ambient myself and could use the help as my breathing system will
probably be based on normal scuba gear. If you have time I'd appreciate the
help.
Regards Simon
-----Original Message-----
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org]On Behalf Of Rick and Marcia
Sent: 20 January 2006 08:24
To: personal_submersibles@psubs.org
Subject: *** SPAM *** Re: [PSUBS-MAILIST] Ambient / 1ATM Q?Hi, Patrick, Bill, et al . . .
I did not realize Rick and Joe were using constant air flow in their ambient designs. Now I see why their hull interiors are almost devoid of water vapour.Regarding constant flow: I'm not sure if Joe is intent on using constant flow in his sub or if he was using the term by way of explanation.My ambient will use a bank or manifold, if you will, of regulators. There will be no constant flow. The regs I'm talking about are standard scuba and are sometimes referred to as DEMAND regs (as opposed to CONSTANT FLOW). By only demanding air when you need it you save your supply.As Rick pointed out earlier this can be handled by dessicant absorbant which is a powder which absorbs water.and basically wicks water out of the air. The air in their tanks is much dryer than normal air also so this helps too.I've used the term "bone-dry" in previous posts and, as Bill has pointed out, there really is little likelihood of anything being bone-dry in a sub cabin. I spoke in relative terms. Desert air is considered "bone-dry" yet actually contains a significant amount of water vapour. Just ask anyone who's had to do a miliary survival course.Magiacl Child's system will be similar to using Barolyme to absorb CO2. Initially I had intended on venting our (breath) exhalations directly from our oral/nasal masks to the surrounding water. I've since experienced an epiphany and am now thinking of simply exhaling straight into the cabin. In this scenario, the dessicant would simply absorb the water vapour from the cabin air (but wouldn't purify it). The cabin's overpressure valve would occasionally burp the excess pressure to the surrounding water.The down side, of course, is that the cabin air would be perennially stale and would support us for less time should we need to stop using our masks. Exhaled CO2 still contains a lot of O2 since the body doesn't metabolise all the oxygen. So, there is still some breathing room so to speak. Mind you, that's what pony bottles are for.What all ambients have in common whether they have an opening to the water (like in an upside down glass) and use the rising water level to trip a float, valve or sensor which then activates their air tanks to vent, or whether they are closed to the water and use a valve or sensor, is that they use internal air pressure to push back against the external water pressureA sealed cockpit obviates the need for a sensor of any kind since the regulators themselves do the job for you (hence, the term "regulator"). The demand regulator is a valve in itself. The rubber diaphram in front of the mouth piece physically pushes a lever that opens the valve.I'd like to add to this by saying that a semi-dry ambient can also use this system. How? Once the required amount of ballast water is admitted, you seal off the cockpit so that the regs take over. Open the valve, the cabin is exposed to surrounding water and the regs are disabled by default. Close the valve, and the cabin pressure is now isolated and available to the regs.Confused yet?Rick L.----- Original Message -----From: Joseph PerkelSent: Thursday, January 19, 2006 11:40 AMSubject: RE: [PSUBS-MAILIST] Ambient / 1ATM Q?************************************************************************ ************************************************************************ ************************************************************************ The personal submersibles mailing list complies with the US Federal CAN-SPAM Act of 2003. Your email address appears in our database because either you, or someone you know, requested you receive messages from our organization. If you want to be removed from this mailing list simply click on the link below or send a blank email message to: removeme-personal_submersibles@psubs.org Removal of your email address from this mailing list occurs by an automated process and should be complete within five minutes of our server receiving your request. PSUBS.ORG PO Box 311 Weare, NH 03281 603-529-1100 ************************************************************************ ************************************************************************ ************************************************************************
Patrick,
As the question is specific to an ambient dry sub which is my design profile, I will answer you in that regard. Whereas a semi-dry or open ambient has a direct connection to the outside ambient pressure, to remain a truly dry ambient requires the use of check valves.
The pressure is equalized by a constant flow of air introduced into the cabin which opens the check valves and dumps the overpressure outboard. The outside ambient pressure does not directly impact the cabin as you noted. There is a delay in compensation, which limits descent rate to design structural capability.
To oversimplify the 1 atm vessel keeps the pressure out by the brute force of it's designed structural integrity.
Joe
From: "Patrick" <pat_man_ta@hotmail.com>
Reply-To: personal_submersibles@psubs.org
To: <personal_submersibles@psubs.org>
Subject: [PSUBS-MAILIST] Ambient / 1ATM Q?
Date: Thu, 19 Jan 2006 11:21:48 -0500
I am having some trouble wrapping my head around HOW the outside pressure influences the inside pressure in an ambient dry sub and how a 1ATM sub keeps the pressure out. Could someone explain this to me?-patrick
