[PSUBS-MAILIST] Dive report: Snoopy at Seneca
Alan James via Personal_Submersibles
personal_submersibles at psubs.org
Mon Jun 8 19:54:42 EDT 2015
Hank,below is Herve Jauberts "Intruder" wet sub.It has a can around the outboard motor shaft that is open at the bottom.So similar principle of air compensation.Alan
From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Sent: Tuesday, June 9, 2015 10:53 AM
Subject: Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca
I am expanding on Brian's idea to have the motor open to the water. A simple hose routed to create traps like your kitchen sink has. The oil can't escape because the hose goes vertical from the motor then loops back down trapping air at the top of the loop. Water can't get in because there is air in the line at the top of the loop. As long as you start with a large enough loop trapping air, the oil will never escape and the water won't get in the motor. Oh ya the hose is open at the end. The pressure is exactly the same on both sides of the seal all the time., An air bubble won't bother anything as long as the air in the hose loop exceeds the volume of an air bubble in the motor.
Hank-------------------------------------------
On Mon, 6/8/15, Private via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
Subject: Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca
To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
Received: Monday, June 8, 2015, 6:28 PM
Hang on, I'm not
understanding Brian's suggestion. What exactly are the
"oil traps"?
> On Jun 8, 2015, at 5:26
PM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
wrote:
>
>
> Actually Brian's idea is picking up
steam in my mind! The power loss your experiencing would
not happen if the motor is open to the water because the
motor is truly equal on both sides.
>
>
Hank--------------------------------------------
> On Mon, 6/8/15, hank pronk via
Personal_Submersibles <personal_submersibles at psubs.org>
wrote:
>
> Subject:
Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca
> To: "Personal Submersibles General
Discussion" <personal_submersibles at psubs.org>
> Received: Monday, June 8, 2015, 5:16 PM
>
>
> Alec,
> I have the same
problem with my drive on Gamma,
> when
returning to the surface the shaft tube is under
> pressure. I have a ball valve mounted to
the tube and even
> a month later there
is pressure until I open the ball
>
valve. I have tried a softer compensation bladder with
no
> luck. There has to be an air
pocket that we are not
> getting rid
of. Brian's suggestion is not bad at all,
> forget the bladder and rig an open hose
with traps so the
> oil can not escape.
There would be an air space trapped
>
between the oil and water in the length of tube. That
air
> bubble would simply move in two
directions depending on
> depth. A very
simple solution, more tricky for you because
> your motors rotate. I think I will test
this idea since I
> have my tail assembly
off for repairs anyways.
>
Hank--------------------------------------------
> On Mon, 6/8/15, Alec Smyth via
> Personal_Submersibles <personal_submersibles at psubs.org>
> wrote:
>
> Subject: Re:
>
[PSUBS-MAILIST] Dive report: Snoopy at Seneca
> To: "Personal Submersibles
General
> Discussion" <personal_submersibles at psubs.org>
> Received: Monday, June 8, 2015, 4:48
PM
>
> OK, let
me
>
> try to reason
this through again. Lets say the standard
> trolling motor shaft seal is watertight
to 50
> feet, and that
> initially I had 1 cubic inch
> of bubble in the system. Dive
> to 250 feet
> and
what I would have thought would happen is
> that the 1 cubic inch of air would be
reduced
> to 1/8th in3
> due to 8 atmospheres of
> pressure increase. I would have
> expected
> that the
compensation bladder would have just been
> squeezed by that volume, and that
upon
> surfacing the bubble
> would go back to 1 in3
> and the pressure in the motor to 1
> atm.
> However, what
we found was that the motor upon
>
surfacing was significantly pressurized. The
> compensation
>
bladder (i.e. hose) was
> visibly
distended by internal
> pressure
upon
> surfacing. There was no leak at
the hose
>
> clamps,
but oil was leaking from the shaft seal.
> Since there was over-pressure
>
> surfaced, clearly
water had to have entered the system
>
during the dive, and as the hose clamps were
> leak free and
> the
seal was not, I suspect
> the seal. Now
the question is
> why water
> would get in. Bubble greater than the
compression
> range of the hose? Seal
offering less
> resistance than the
> hose to compression?
> Shaft pumping water under the seal
> during
> operation
due to abrasions? Thermal contraction?
> I'm actually not sure - any theories
are
> welcome. One
>
interesting detail - the stern
>
thruster, which was not
> working due
to the
> issue with the speed controller,
did not
>
> have any
oil leaks. Both side thrusters, operating,
> did.
> The side
> thrusters being feeble can be explained
by
> pressure on their
> seals, or just by their
> age and related wear on the
> commutators. I
> will
be changing them, or at least their
>
> internals.
>
> Best,
> Alec
> On Mon, Jun 8, 2015 at
> 2:54
> PM, Jon
Wallace via
> Personal_Submersibles
<personal_submersibles at psubs.org>
> wrote:
>
>
>
>
>
>
>
>
>
>
> It sounds
like at some point water pressure at
>
the
> seal was able
>
> to
compress the bubble of air in the tube,
>
the
> opposite of what
>
> was
expected.
>
>
>
>
I'm kind of stumped by
> the
description of the
> motors
> performance
>
being
> "feeble" however.
This couldn't
> have been primarily
due to
>
>
pressure I don't think. Also,
>
isn't an easy
> fix just to
> "clamp"
>
the
> tube any place where
liquid appears assuming the
> tube is
held
>
> in
a vertical position and the bubble is at
> the top
> (ie vise
grip
>
>
the tube).
>
>
>
>
Jon
>
>
>
>
>
> On
6/8/2015 12:01 PM, Brian
> Cox via
> Personal_Submersibles wrote:
>
>
>
>
>
>
Hmm,
> guess I'm not getting what
is
>
> happening
>
> Brian
>
>
>
>
>
>
>
>
>
>
>
>
>
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