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Vance,
I'm not saying a trolling motor is not designed
correctly.(for it's use). But take a trolling motor and place it in a press
(vertical press...vertical orientation ........bearing on end of the shaft) Turn
it on...and add pressure until it won't move. If you have a pressure gauge and a
fsw chart of pressure versus depth...you can now see where the motor will stop
working.
Remember...the deeper we go....the more pressure
exerted on that shaft trying to push it in the motor (or the seals
leaking....)
Also....most trolling motors (not all) are standard
brushed motors. When you calculate that they are only 55-65% efficient.....that
hurts. A BLDC motor is 80-90% efficient. Battery power goes much further. Put
some pressure on it....and I'm sure a trolling motor is even less
efficient.
I'm not saying to not use trolling motors.......but
for people looking to stay down longer, and have a limited power budget, may
want to have some efficient thrusters.
James Long
Owner/Designer
Lil Brother LLC (Instrument Division)
----- Original Message -----
Sent: Sunday, July 29, 2007 3:28 PM
Subject: Re: [PSUBS-MAILIST] Thruster
ideas
Ten million trolling motors can't all be wrong (although they
have the motor's outer case itself as part of the housing, for more direct
distribution of heat). HBOI improves on that by the simple expediant (simple
to say, not to do) of machining a base plate replacement for the shaft end of
a PM motor. Bearings mount in the divider plate, and the motor casing is
assembled on top of it. The stub shaft is spline cut and sticks into the sun
gear through the plate. A welded can goes over the top (o-ring seals at the
divider plate) and a cast housing mounts to the back, within which is the
large shaft with bearings, coupling and seal. The whole thing is aluminum, of
course, and bleeds heat exceedingly well. That handy old ultimate
heat sink out there in the deep briny never seems to get enough.
And,
before you ask, 1.25 HP reduced to 250 or something lets them turn a square
tipped four-bladed 14X14 prop in a Kort nozzle--with maybe 80
pounds of thrust-in-motion (not bollard pull, that's probably 100 or
a little better). It's old fashioned, I guess, but, as you know, I'm a
bigger-and-slower-is-better kind of guy where props are concerned, and I like
that torque in the water. Man, I'd love to have some of those babies at 48V.
My K-350 would turn every way but inside out. I'd rig it just like the good
Dr. Nuyton did on the DWs, and as we discusssed for NR-2 (I think that was
about 4 tons ago, or so).
Mind you, Phil's 1 hp rare earth units kick
ASS on the Deepworkers, which tells me prop and nozzle design and all the rest
has come a long way through the years. At $10,000 a pop, I don't suppose
either one of us will get any realtime hands-on experience with them, but it
sure do sound good, do it not?
Vance
-----Original
Message-----
From: Joseph Perkel <joeperkel@hotmail.com>
To:
personal_submersibles@psubs.org
Sent: Sun, 29 Jul 2007 12:59 pm
Subject:
Re: [PSUBS-MAILIST] Thruster ideas
James,
I am wondering (and perhaps Vance can speak to this), if "conduction"
through the mountings to the external case, is sufficient for a directly
immersed air-filled thruster.
Joe
From: "Lil Brother LLC" <lil_brother_llc@bellsouth.net>
Reply-To:
personal_submersibles@psubs.org
To:
<personal_submersibles@psubs.org>
Subject:
Re: [PSUBS-MAILIST] Diver Lockout.... serious question
here!!
Date: Sun, 29 Jul 2007 11:08:27 -0500
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)
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