Re: [PSUBS-MAILIST] Sgt. Peppers O2 consumption rate question.

["Captain Nemo" <vulcania@interpac.net>]

----- Original Message -----
From: "Carsten Standfuß" <MerlinSub@t-online.de>
To: <personal_submersibles@psubs.org>
Sent: Wednesday, November 29, 2000 5:47 PM
Subject: Re: [PSUBS-MAILIST] Sgt. Peppers O2 consumption rate question.


> Hi Pat
> Your tank is diamter 0,1325 m length 0,325 m
> so volume (without any correction for the tickness) is :
>
> ((0,1325 x 0,1325) x 3,1415)/4 x 0,325
> = 0,00448 cubic meter or 4,48 Liter, with 122 bar it should be
> 4,48 x 122 = 547 Liter - so figures seems right.

Good.  Thanks!  This is what I wanted to know.


> But is that a new bottle ? we use here normally 225 bars (atm.)

Yep, new bottle.  Might have been sitting around for a while; somebody might
have bled off some O2 before I bought it.  I usually get my O2 at 2200 PSI;
this one was only 1800.  I'll make sure they fill it completely when I
refill it.
> So, figured on an average Oxygen consumption rate of about 0.25 liters of
O2
> > per person / per minute: one liter of O2 would last one person about 4
> > minutes; and 566 liters would last 2264 minutes, or 37.73 hours; right?
> >
> right - but see also message to Stan

Cool!  Man, that's really great.  Back in '91, we did the first tests
without life support.  Then I went to a LSS with a 60 cubic foot bottle of
02 and a scrubber made from the defroster fan from a Chevrolet Van, a
homemade duct, and a gym sock full of SODASORB.  Worked fine; but our dive
time was limited to about 1.25 hours because we had to get on and off the
launching ramp during high tide (depth needed to launch and recover was
about 4 feet on the ramp); so I never got to know how long it would last.
Now I've gone to a smaller bottle to save space inside the sub, and the
exact duration is more important to know.  Heck!  By these numbers, if I buy
a second 20 cubic foot bottle (or go to a 40 cubic footer) I'd have enough
LS to meet that 72 man-hour requirement.  This is good to know.  Thanks!
> But the inside volume is more less - you body, all equipment the bottles
> displace some of this volume.
> So your inside volume must be calculate to 991 minus 75-95 Liters for
> your body minus 4,5 Liter for the o2 bottle, minus ... etc.etc.

You know, I didn't think about that.  Thanks again!

> I am working allways with security factors ..
> so use maybe 0,5 l/min consumption and figure out 37/2 = 18,5 hours..


Yeah, considering possible consumption variables with exertion and such, I
was planning on estimating about 1/2 the time for safety's sake.  With this
sub, we always operate in shallow, protected areas; we have a dive crew in
the water for emergencies; and I doubt I'll ever do more than two hours in
the sub intentionally.  Even at 18.5 hours, that still gives me plenty of
time to get rescued if something goes wrong.


> Today I get the steel anticollision bulkhead (3,2 feet in diameter,
> half inch strong)  and the stiffners for it.
> Its forward on the bow-main ballast tank and will later covered
> by a GRP /GFK nose with the sounder, video, lamps etc.
> Something to weld for the weekend.
>
> Carsten

Cool!  Good luck with your submarine.

VBR,

Pat