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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