underwater motors
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Posts: 46,084
There are some technologies used for sealing underwater motors;
Presssure sealed:
a) O 'ring shaft seals: low, cost, may be difficult to project and prone
to fail. Works well only in small angular speeds (small diameters shafts
or slow RPM) Low MTBF.
b) Mechanical seals: Commercially available, Medium cost.Medium Life.
Low pressures.
c) High end mechanical seals (Mag-Seal etc..) Two precision lapped
surfaces. High cost. Very reliable. Hard to find small diameters.
d) Two isolated shafts, magnetic coupling. High cost. Fail safe.
Pressure balanced:
a) Use oil ( low viscosity oil ) immersed motors. Use O'rings are used
only to avoid large oil escape or large water entrance. O'rings will
work at same pressure at both sides. Low cost.High MTBF. Oil helps to
heat exchange. This method is used in commercial deep sea thrusters.
Large RC Servo motors already are O'ring sealed. Enclosure oil filling
is best done with a vaccum pump.
Are you looking for these motors for a pan & tilt camera system or they
will be used for propulsion ?
ACJacques
Raphael Abrams wrote:
>
> anybody know of a source for inexpensive submarine motors? i'm making an
> underwater servo controlled camera for depths of 150 feet. if the motor
> can come in a sort of sealed off ducted fan arrangement, that would be
> ideal.
>
> thanks!
> raphael abrams
Presssure sealed:
a) O 'ring shaft seals: low, cost, may be difficult to project and prone
to fail. Works well only in small angular speeds (small diameters shafts
or slow RPM) Low MTBF.
b) Mechanical seals: Commercially available, Medium cost.Medium Life.
Low pressures.
c) High end mechanical seals (Mag-Seal etc..) Two precision lapped
surfaces. High cost. Very reliable. Hard to find small diameters.
d) Two isolated shafts, magnetic coupling. High cost. Fail safe.
Pressure balanced:
a) Use oil ( low viscosity oil ) immersed motors. Use O'rings are used
only to avoid large oil escape or large water entrance. O'rings will
work at same pressure at both sides. Low cost.High MTBF. Oil helps to
heat exchange. This method is used in commercial deep sea thrusters.
Large RC Servo motors already are O'ring sealed. Enclosure oil filling
is best done with a vaccum pump.
Are you looking for these motors for a pan & tilt camera system or they
will be used for propulsion ?
ACJacques
Raphael Abrams wrote:
>
> anybody know of a source for inexpensive submarine motors? i'm making an
> underwater servo controlled camera for depths of 150 feet. if the motor
> can come in a sort of sealed off ducted fan arrangement, that would be
> ideal.
>
> thanks!
> raphael abrams
Comments
underwater servo controlled camera for depths of 150 feet. if the motor
can come in a sort of sealed off ducted fan arrangement, that would be
ideal.
thanks!
raphael abrams
>
>anybody know of a source for inexpensive submarine motors? i'm making an
>underwater servo controlled camera for depths of 150 feet. if the motor
>can come in a sort of sealed off ducted fan arrangement, that would be
>ideal.
I don't know if this will be much help, but years ago I built a two-person
wetsub for scuba use with motor heads from those electric outboard trolling
motors. I seem to recall that we purchased a few of the motor head
assemblies only, right from the manufacturer. These were powerful, cheap
and ran forever from a deep cycle 12 volt battery. Our sub had four, and at
high speed it would pull our masks off! We had to add a small 'windscreen'
(hydroscreen?) to deflect some of the water pressure. A piece of thin
aluminum tubing made a great duct, or I guess you could even use large
diameter PVC. I don't know if the pressure seals would hold up at that
depth. You could try contacting some of the companies that actually
manufacture those trolling motors...
Cheers, Duncan
Norm & Monda
Cozy MK IV #202
Ford V-6 Powered
Original Message
From: "Raphael Abrams" <raphael@w...>
To: <basicstamps@egroups.com>
Sent: Monday, July 24, 2000 2:34 PM
Subject: [noparse][[/noparse]basicstamps] underwater motors
>
> anybody know of a source for inexpensive submarine motors? i'm making an
> underwater servo controlled camera for depths of 150 feet. if the motor
> can come in a sort of sealed off ducted fan arrangement, that would be
> ideal.
>
> thanks!
> raphael abrams
>
>
>
>
>
>
trust them unless I had a
fail safe way to retrive my camera. I am thinking of building a
tethered camera using these motors to study Dragonfly larva
in my pond. How did you seal the camera, Is it autonomous or tethered ?
Raphael Abrams wrote:
> anybody know of a source for inexpensive submarine motors? i'
>anybody know of a source for inexpensive submarine motors? I'm making an
>underwater servo controlled camera for depths of 150 feet. if the motor
>can come in a sort of sealed off ducted fan arrangement, that would be
>ideal.
>
two classic inexpensive ROV motor sources are small sealed bilge pumps for
steering and control (Rule® or Johnson are available at places like WEST
MARINE), or for more power, you can use trolling motors. I bought mine pretty
cheap at a goodwill superstore.
===========
Larry Geib
ljgeib@a...
===========
a. c. jacques: initially i will need a propulsion motor, but i will
eventually want a sewt of waterproof servos as well. I like the magnetic
coupling idea, any sources?
duncan, norm: trolling motors sound good, but where can i find a small
one? this device only weighs about 3 or 4 pounds, and is neutral in water.
do you know a couple of brand names i can try?
maybe a motor from a toy
submarine would work?
thanks again to all,
raphael abrams
magnetics with small diameter and the required torque for a thruster may
cost more than a thousand $ ! (Giannini Petro-Marine - California )
There are some pumps brands (??) that uses also magnetic couplings(low
torque) but they are disks that will add axial attraction forces in the
shaft.You may project and make yourself these disks with a number of
small strong magnets.
Bilge pumps and trolling motors are not designed to work in high
differential pressures like underwater. Higher pressures, may stress,
shorten life or completely fail the sealing components.
The technique of pressure balanced( oil immersion ) could be easyly be
implemented in a trolling motor giving you a very reliable thruster.
You just need drill a hole in air compartment of armature rotor,and fill
it with Singer machine oil or other low viscosity inert fluid ( kerosene
? )and fit a small lenght of flexible hose (silicone) that could be
closed at the other end. Water pressure will compress the hose,
equalizing the internal pressure . Eventual trapped air bubbles will be
compressed lowering the total volume. The inside volume of hose must be
higher than these bubbles.
Electric trolling motors are available from fractional HP up to few.
The cost may start from around $250 ea.
Check web for Mini-Kota motors.
There are also Johnson, and Mercury, and other outboard manufacturers
that sell electric trollers.
Good servos and strong RC servos (Tonegawa Seiko -SSPS) are avaiable
from
vantec.com
ACJacques
Raphael Abrams wrote:
>
> thanks all for the responses!
>
> a. c. jacques: initially i will need a propulsion motor, but i will
> eventually want a sewt of waterproof servos as well. I like the magnetic
> coupling idea, any sources?
>
> duncan, norm: trolling motors sound good, but where can i find a small
> one? this device only weighs about 3 or 4 pounds, and is neutral in water.
>
> do you know a couple of brand names i can try?
>
> maybe a motor from a toy
> submarine would work?
>
> thanks again to all,
> raphael abrams
>
>Depending on your power requirements and budget, the market is full of very
>inexpensive epoxy incapsulated submersible pumps. These could be homebrewed
>into a cheap 'jet' engine or reaction thruster. They are available in a
>full
>range of power ratings and potential thrust capacities. Prices range from
>$10-$60.
...and depending on the thrust you need to generate, you might be able to
mount the pumps pointing perpendicular to the desired plane of travel, and
use a duct to redirect the flow by 90 degrees. Rotating the duct gives you
thrust in any direction along the plane the pump's output is perpendicular
to.
I've seen similar setups used for "docking thruster" type purposes, with the
output jets pointing straight down from the hull, and using a rotating duct
to redirect the thrust forwards, backwards, or to the sides -- sort of a
parallel parking method for boats. It just pulled up to a few feet from the
dock, rotated the ducts, and slid sideways up to it. Very clever
arrangement, and worked like a charm.
________________________________________________________________________
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Depending on your power requirements and budget, the market is full of very
inexpensive epoxy incapsulated submersible pumps. These could be homebrewed
into a cheap 'jet' engine or reaction thruster. They are available in a full
range of power ratings and potential thrust capacities. Prices range from
$10-$60.
Regards
________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com
to answer a few last questions: the camera is in a plexiglass box and the
whole thing is tethered with five or six wires- power, ground, camera
output, and serial in and out. there will be a pan tilt servo setup on the
camera, and a bunch of power transistors (or maybe even relays, if I don't
need speed control) and a stamp1 program burnt onto a pic for servo
and motor control.
the tether will go to a control board that houses another stamp and a set
of controls, and a small monitor (radioshack tv or video camera with
inputs for recording)
so thanks again to all, and any more ideas will be much appreciated, f
course!
-raphael abrams
I found this link to Minnkota, one of the major trolling
motor manufacturers:
MINNKOTA TROLLING MOTORS
(800) 227-6433 MN
http://www.jwa.com/motors/minnkota/minnkota.html
Although it sounds like these will be too large/powerful for your app.
I've been thinking about the pressure requirements of whatever seals you
use and it shouldn't be too difficult to get a solid seal. At 150ft the
pressure will be ~67 psi - seems well within the reach of even simple seals.
Best, Duncan
is finished? It sounds very interesting.
Sincerely
Kerry
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