|
Vance,
Your message contained all the specific
information to consider all the problems......I'll try to fish them
out......and add my views:
"Correctly designed, the pressure can material
withstands the compression without distortion."
This view takes into the consideration thickness, shape, and
material. I'm sure most people who design them(pressure vessels) are
not looking to magnetically couple a motor through their hull. So their design
will not necessarily work so well, for our idea. With a thin material (needed
for magnetic coupling)......the design will not be optimum. Also......steel is
the predominate material used....which we all know can't be used for the
coupling. So...for all practical purposes....the coupling area will be to
"required design"...not optimum strength.
Designing an oil filled thruster is a balance
of compromises. The thickness, material, shape, and filler are all
considerations to get it working. The vessel is only as strong as the weakest
spot. So.....I figured using oil would be a great way to keep structural
integrity.
I may have to add a pressure compensation system to
prevent structural failure, but I already have an idea for that as well.
Please remember....I'm trying to build a "cheap"
thruster to be a substitute for trolling motors. I would have used the words
"cost effective" but what does that really mean?
James Long
Owner/Designer
Lil Brother LLC (Instrument Division)
----- Original Message -----
Sent: Sunday, July 29, 2007 11:47
AM
Subject: Re: [PSUBS-MAILIST] Diver
Lockout.... serious question here!!
Understood, density is the factor. However, compression of bearings and
the like isn't the problem. Correctly designed, the pressure can material
withstands the compression without distortion. Ultimately, the problem with
air filled 1 atmosphere cans is more one of the rotating seal, and entrained
sea water which, inevitably, corrodes the polished surfaces. This isn't a
guess, rather it is a report on real circumstances. VERY DEEP, however, makes
the entire discussion moot, and if you've got a working mag coupling that I
can afford, then I want one (or several, come to that). My friend Ian
Blaimire, who founded the Seaeye Corporation, made his living with replacement
ROV thrusters which had mag couplings (which he cooked up while working with
us at Intersub) and provided an amazing improvement in service life. Oh,
boy!!! Just think, no shaft seals. Whooee! Sign me up!!!
Vance
-----Original Message-----
From: Lil Brother LLC
<lil_brother_llc@bellsouth.net>
To:
personal_submersibles@psubs.org
Sent: Sun, 29 Jul 2007 12:08 pm
Subject:
Re: [PSUBS-MAILIST] Diver Lockout.... serious question here!!
Vance,
Air is the least effective means to cool
something that is enclosed. The problem with air, if it is exchanged in a fast
enough rate, it works great. On the other hand....if you can't exchange the
air, you end up with an oven. Oil on the other hand can carry
more heat away faster. The density is the factor here. Air is
not very dense, so it will only absorb so much thermal energy per unit.Oil
will absorb many more btu per unit than air. Also because oil will
thermocycle.....the oil will transfer the heat to the container that contains
it faster.
I think an air filled thruster would work good
too, but there are problems with compression. If there are any bearings housed
within the casing......they will bind under extreme pressure if filled with
air. An oil filled enclosure will not compress as far. There will still
be compression problems, but not to the extent of an air filled
unit.
There was a project a few years ago....a guy made
a gaming computer that used oil to keep all the expensive parts cool. You
should look it up. It worked really well. (Oil cooled computer)
I do not plan at this point to run a reduction
gear. BLDC motors are real good at direct drive.
I would like to build smaller thrusters that can
go very deep.
James Long
Owner/Designer
Lil Brother LLC (Instrument
Division)
----- Original Message -----
Sent: Sunday, July 29, 2007 8:55
AM
Subject: Re: [PSUBS-MAILIST] Diver
Lockout.... serious question here!!
James,
Serious DLOs have dive chambers separate from the crew compartment. And
as for your thrusters, in my experience AIR transmits heat faster than oil.
How deep are you building these things for? HBOI, for instance, runs
aluminum cans and PM motors in air to 3000 feet, with no real problems. The
commercial units that Nuytco uses ARE oil filled, I believe, but have a
higher pressure rating, and no reduction gear.
I've got into some pretty serious questions lately......and I've done a
little reading about diver lockout (archives), but the archives raised a
question.
If you have a 1 atm sub, with a diver lockout........how do you lock a diver
back in?
Are there any 1 atm subs with a lockout?
If there are......if the lockout has been pressurized to the outside
pressure........what method is used to depressurize it back to 1 atm?
(these questions are redundant I know)
And the last....the important one.....is this on the dangerous side? If you
depressurize to fast......the bends.
I was reading about the nice sub.....(the Krata I think.....please don't
quote me ....I've had a very long two days)......but I didn't notice if it
was 1 atm or not.
Some one learn me on this. :-)
(Hey....at least I know what a VBT is for now.)
James Long
Owner/Designer
Lil Brother LLC (Instrument Division)
************************************************************************
************************************************************************
************************************************************************
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 53
Weare, NH 03281
603-529-1100
************************************************************************
************************************************************************
************************************************************************
|