Re: [PSUBS-MAILIST] Pressure compensation

["D. Blake" <dblake@bright.net>]

What about using the motor from a submersible pump?  Granted it will no
doubt be AC, but you could use a relativaly cheap inverter as long as the
amperage was not too high.
Big Dave

-----Original Message-----
From: Gary R. Boucher <protek@shreve.net>
To: personal_submersibles@psubs.org <personal_submersibles@psubs.org>
Date: Friday, August 11, 2000 11:31 PM
Subject: Re: [PSUBS-MAILIST] Pressure compensation


>Jon,
>     You're right in that the mentioned method is a much better way of
>compensating.  I wonder if anyone has ever been successful at using a low
>viscosity oil in a trolling motor.  It would be an interesting experiment
>in the direction of a low cost compensated thruster.  It almost makes me
>want to go get a trolling motor and experiment.  I wonder if the armature
>would have too much drag against the oil and how much power you would loose
>in the process.  I would think that cooling would not be a big problem.  I
>would suspect that real thrusters for submersibles that are compensated in
>this way have special armatures.  Probably the same oil used in submersible
>pump applications would work.
>
>GB
>
>At 08:16 PM 8/11/00 , you wrote:
>>On Fri, 11 Aug 2000 22:00:37 -0700, "Gary R. Boucher" <protek@shreve.net>
>>wrote:
>>
>> >      The trick is having the pressure inside the motor the same as the
>> > outside pressure, or at least close.  If you set the pressure inside
the
>> > motor at a certain value and ascended the pressure inside is greater
than
>> > outside.  If you dove beyond the set pressure you have more pressure
>> > outside.  One method of pressure compensating a motor is to place a
rubber
>> > bladder with air in the water close to the motor and run a tube from
the
>> > bladder to the motor housing.  As the sub dives the pressure on the
>> bladder
>> > increases and so does the inside motor pressure.
>>
>>Just as a point of interest...
>>
>>In deep professional-quality thrusters, they typically fill the thruster
>>housing (and thus the motor) with oil, which makes the whole deal
basically
>>non-compressable. Instead of using a seal, they use a magnetic coupling to
>>turn the propeller. This gives a thruster that can be used to full ocean
>>depths.
>>
>>Later,
>>Jon
>>
>>--------------------------------------------------------------
>>    Jon Hylands      Jon@huv.com      http://www.huv.com/jon
>>
>>   Project: Micro Seeker (Micro Autonomous Underwater Vehicle)
>>            http://www.huv.com
>