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RE: [PSUBS-MAILIST] Pressure compensation
Gary,
I just read the Unconventional UW thread backwards. Although it was
extremely entertaining, I suddenly understand your concern about making fun
of my fish oil. However, I am the first to admit that I have many many very
stupid ideas and only the occasional good one. But as long as I keep having
the occasional good one I will continue to blurt out the dumb ones. Which
then means I need a clever fellow like your self to tell me that it is a
dumb idea so I don't have to suffer through finding that out myself. So I
beg of you, next time just come right out and say it, it will save me time
and effort in the long run (even if I don't find it very funny at first).
Where I live, we now have three brand new and thoroughly useless, but very
expensive ferries. They were built because nobody really bothered to stand
up and say exactly what they thought of the whole idea. And by the way, you
can never squash creative thinking, no matter how bad the joke.
Actually, the whole reason I'm writing this is that now I'm imagining that
you could have come up with a really good joke and I'm missing it.
Cheers,
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