Yes. On a three
square-inch surface area of the sub, that would be perfectly true. But the
pressure around the sub would not be changed: It would still be
267psi.
The recent delay in the
posting of emails (that, long with a few cups of coffee) has me rethinking
this whole thing. And Frank, if I've come across in my emails as sounding
condescending, I sincerely apologize. My intent is not
to challenge, merely understand.
Let me see if I can ask
this a different way, and see what kind of answers I get (and yes, I am
looking for answers)
If I had a square tube
welded to the side of my hull, and the opening was exactly one inch wide by
one inch high, and I had a square rod that fit perfectly inside this tube,
then when the sub is 600 feet down, them amount of pressure I would have to
exert on the rod (to keep it in place) would be 267 pounds because the end of
the rod that is facing the ocean has one square inch of surface
area.
Now, instead of a 1
square-inch example, I perform the same experiment with a ¼? tube & rod
combination. The total amount of
surface area facing the ocean is a quarter of the surface area on the one-inch
rod, so the pressure I would need to keep this rod in place would be about 67
pounds.
Now, let?s set up a third
experiment: Let?s use that same 1? square tube, but this time we?ll weld a
plate over the end (facing the ocean) that has a ¼? square hole in it. Now?
how much force is it going to take to keep that 1? rod in the tube? My money
would be on 267 pounds.
Here?s my idea of
thinking: If you?re using a piston-type pump to force water out of the sub
into the surrounding sea, the amount of force required is equal to the
external pressure times the surface area of the top of the
piston. I don?t believe it has anything to do with the diameter of
the pipe between the pump and the hull of the sub.
Could someone tell me if
I?m right or wrong on this one?
--
NP
From: bobtravis@comcast.net
Reply-To:
personal_submersibles@psubs.org
To:
personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] RE:
payload
Date: Fri, 08 Dec 2006 19:12:06 +0000
Wouldn't that be 267 pounds per squair inch? Which would mean that if
you had a surface area of three inches, then the force against it would be
801 pounds?
--------------
Original message --------------
From: "Nomdae Plume"
<nomdae@hotmail.com>
Frank:
I read this post first thing this morning, and my brain still isn't in
gear, so let me see if I understand this correctly:
I'm in my sub, 600 feet down, and the outside pressure on the hull is
18atm.
(600 / 33) = 18.18atm or 267psi
Now let's say I have three pipes entering the hull, and all
three have pressure gauges on them. The first pipe is 3" in
diameter, the second is 1", and the third is 1/4" in diameter. Won't all
three gages read the same pressure? Will a pump have to generate
267.0001psi in order to pump anything out of the hull?
I think I can understand what you're saying about smaller
pumps. A small pump can be geared down so that the volume of
water it's moving is decreased while the pressure it creates is
increased. It would just take more time to pump out all the water you were
trying to move. However, hooking a pump up to a 1/4" hose is not
going to give you any more of a mechanical advantage than hooking it up to
a 3" pipe... or directly to the hull of the sub.
Am I right? Or should I get a few more cups of coffee in me
before I start posting? ;-)
-- NP
From: ShellyDalg@aol.com
Reply-To:
personal_submersibles@psubs.org
To:
personal_submersibles@psubs.org
Subject: Re:
[PSUBS-MAILIST] RE: payload
Date: Wed, 6 Dec 2006 21:30:09
EST
Just a quick note on this pressure thing. If you are pushing
against the pressure in a 1/4 inch high pressure hose/line, a small pump
would work. Frank D.
Talk now to your
Hotmail contacts with Windows Live Messenger.
************************************************************************
************************************************************************
************************************************************************
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
******************************************! *******
***********************
************************************************************************
************************************************************************