[PSUBS-MAILIST] Dive report: Snoopy at Seneca

hank pronk via Personal_Submersibles personal_submersibles at psubs.org
Mon Jun 8 18:53:38 EDT 2015


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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