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Re: [PSUBS-MAILIST] Pressure compensation
Fish oil is used a lot as a corrosion inhibitor, works very well and can be
obtained in a deodorized version. Seems like the last thing you would want
to use in an electric motor though, much too viscous. Not too expensive and
good for those hard to paint and protect spots on a steel vessel.
Surely, if you are using a magnetic drive, you can make a pressure proof
vessel for the motor that does not need the oil as well. O-rings, fitted
correctly, are good for 1000's of PSI.
Regards, Karl.
----- Original Message -----
From: Wade Carson <wacarson@interchange.ubc.ca>
To: <personal_submersibles@psubs.org>
Sent: Saturday, August 12, 2000 2:42 PM
Subject: RE: [PSUBS-MAILIST] Pressure compensation
> Gary,
>
> That was pretty clever. It seems you still did say that it stunk doesn't
> it. Hehe. Actually, the oil does have a commercial application, it isn't
> just fish oil. It just happens to be made from fish, which was convenient
> for me at the time. Unfortunately, I don't remember what the application
is
> but it's something to do with hydraulics. Can you get large volumes of
> submersible pump oil without breaking the bank? It most certainly does
> smell like fish.
>
> Wade
>
> -----Original Message-----
> From: owner-personal_submersibles@psubs.org
> [mailto:owner-personal_submersibles@psubs.org]On Behalf Of Gary R.
> Boucher
> Sent: Saturday, August 12, 2000 8:44 AM
> To: personal_submersibles@psubs.org
> Subject: RE: [PSUBS-MAILIST] Pressure compensation
>
>
> Wade,
> I was going to joke with you and tell you that I thought your idea to
> use fish oil stunk. But, I would get more negative mail saying that I
> squashed creative thinking. I like your idea, I just don't know if I
could
> go with the fish oil. Does it really smell like fish? I think for those
> not entering contests they might try submersible pump oil. Was this for
> man powered wet subs? I can see where they would not want to recreate the
> Exxon Valdez (Sp?) scenario on a smaller scale.
>
> GB
>
>
> >Gary,
> >I've actually compensated a drive train in this way before. Granted it
> >wasn't a trolling motor but it did work in my application. I used a high
> >viscosity oil made from fish (so it was biodegradable which fit with the
> >rules of the competition I was in). It smelled terrible, but it was
cheap
> >and worked really well. Unfortunately, it was discovered that you still
> >need do put on some sort of compensation device (we used a sturdy
balloon)
> >because it is very difficult to get all of the air out of the system and
> >even the tiny bubbles will contract and suck some water through the seal
if
> >you don't. However, the balloon only needs to be very small. It actually
> >improved the efficiency of our drive train because it lubricated all the
> >parts (there were lots of gears and no long shafts). Anyways, the point
is
> >if the losses aren't too significant it is a very simple and very cheap
way
> >of fixing the problem.
> >
> >Wade
> >
> >-----Original Message-----
> >From: owner-personal_submersibles@psubs.org
> >[mailto:owner-personal_submersibles@psubs.org]On Behalf Of Gary R.
> >Boucher
> >Sent: Friday, August 11, 2000 11:23 PM
> >To: personal_submersibles@psubs.org
> >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
>
>