Yeah, I sort of left that detail out in earlier
postings.
Rick L
----- Original Message -----
Sent: Saturday, January 21, 2006 4:45
AM
Subject: Re: [PSUBS-MAILIST] Ambient /
1ATM Q?
Ah ha...now I understand! One little detail, (thru-bulkhead mounting) makes
all the difference.
Yes, that will work nicely!
Joe
From: "Rick and Marcia" <empiricus@telus.net> Reply-To:
personal_submersibles@psubs.org To:
<personal_submersibles@psubs.org> Subject:
Re: [PSUBS-MAILIST] Ambient / 1ATM Q? Date: Fri, 20 Jan 2006
23:59:29 -0800
Hi, Joseph . . .
Short answer: the cabin is at less pressure
(partial vacuum) than the surrounding water. Greater pressure outside
pushes in on the reg's diaphram since the lesser pressure is on the
mouthpiece side. Essentially the cabin is like your lungs: drawing in
air.
The regs will be mounted on the bulkhead with
the diaphram on the water side and the mouthpieces on the cabin
side.
I had a long answer but the short one
works!
Rick L
----- Original Message -----
Sent: Friday, January 20, 2006 7:17
AM
Subject: Re: [PSUBS-MAILIST] Ambient
/ 1ATM Q?
Rick wrote:
"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."
I'm sorry Rick, "explain it to me like I'm a two year old" Where the
cabin environment is concerned, where is the negative
pressure required to trigger the regulators on descent?
I can see Chips membrane trigger working but, this I don't get yet.
Joe
From: "Rick and Marcia" <empiricus@telus.net> Reply-To:
personal_submersibles@psubs.org To:
<personal_submersibles@psubs.org> Subject: Re:
[PSUBS-MAILIST] Ambient / 1ATM Q? Date: Fri, 20 Jan 2006
00:23:40 -0800
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
pressure
A
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 -----
Sent: Thursday, January 19,
2006 11:40 AM
Subject: RE: [PSUBS-MAILIST]
Ambient / 1ATM Q?
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
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