[PSUBS-MAILIST] Dive report: Snoopy at Seneca
Alec Smyth via Personal_Submersibles
personal_submersibles at psubs.org
Tue Jun 9 22:38:09 EDT 2015
All right, lets see what results that produces - I look forward to hearing.
For my part, I'm going to concentrate on eliminating the leftover air
because I agree, if we have 100% oil and no trapped air at all it should be
the end of the story. I'm going to put NPT set screws in the nose cones as
I think that will be the easiest way to fill without voids. I'm also trying
to get new armatures, as the commutators have wear and I want to bring back
their youth a bit.
Best,
Alec
On Tue, Jun 9, 2015 at 9:59 PM, hank pronk via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:
>
> Alec,
> There really is no other explanation than air in the motor. I can't see
> motor temperature causing it because the motor is in the most ideal
> environment (cold water) and full of oil. The air is compressing and water
> is entering past the seal due to shaft rotation and depth. It wouldn't
> matter if the hose did not collapse, because the motor is plumb full of oil
> in theory. My vertical thruster has no hose or bladder, it is just full of
> oil and it seems just fine, It only has one seal, so no little air space.
> It really does not take much air volume to create the problem, the inside
> seal will hold whatever small over pressure we create, until it fails of
> coarse and that is the visible oil we see causing dock side shame. :-(
> One thing you could do if you want to keep the inner seal is to pack the
> void with grease.
> I am changing Gamma's system this weekend to the open tube idea and am
> confident it will solve my leak.
> Hank--------------------------------------------
> On Tue, 6/9/15, Alan James 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: Tuesday, June 9, 2015, 9:37 PM
>
> Alec,once you
> get past an inch or so in length at the diameter we are
> usingthe
> external pressure rating doesn't
> change.I think
> the same would apply to the internal rating; so they would
> be basing the 40 psi
> maximum pressure on an unlimited length of
> tube.Another
> factor may be the cold operating temperatures making it
> lessflexible.Alan
>
> From: Private via
> Personal_Submersibles
> <personal_submersibles at psubs.org>
>
> To: Personal
> Submersibles General Discussion
> <personal_submersibles at psubs.org>
>
> Sent:
> Wednesday, June 10, 2015 12:45 PM
> Subject: Re:
> [PSUBS-MAILIST] Dive report: Snoopy at Seneca
>
> The hose is wound around the motor, so there
> are quasi-flattened parts I'm sure. But even if it were
> laid out straight, you would find the high length to
> diameter ratio would make it extremely susceptible to
> collapse via the general instability failure mode.
>
> There are several types of
> PVC, and I wonder if the material properties you've got
> might be for the rigid type used in plumbing. This stuff is
> really soft and pliable.
>
> Problem is, I still have no satisfactory
> explanation for why my motors or Hank's seal come up
> pressurized. I'm not convinced that these floppy hoses
> can withstand significant pressure, but I don't have a
> good alternative theory.
>
>
>
> > On Jun
> 9, 2015, at 8:13 PM, hank pronk via Personal_Submersibles
> <personal_submersibles at psubs.org>
> wrote:
> >
> > Alan,
> > My gut feeling is the hose will flatten
> quite easily as is because it has no support to keep it
> round. Just a feeling, can't argue with specs though.
> > Hank
> >
> --------------------------------------------
> > On Tue, 6/9/15, Alan James 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: Tuesday, June 9, 2015, 7:54
> PM
> >
> > Do
> > you mean if it is crimped Hank?Or
> > are you saying that just as is it will
> flatten
> > easily?Alan
> >
> > From: hank pronk
> via
> > Personal_Submersibles
> > <personal_submersibles at psubs.org>
> >
> > To: Personal
> > Submersibles General Discussion
> > <personal_submersibles at psubs.org>
>
> >
> > Sent:
> > Wednesday, June 10, 2015 11:27 AM
> > Subject: Re:
> >
> [PSUBS-MAILIST] Dive report: Snoopy at Seneca
> >
> >
> > Alan,
> > I think
> > it will flatten under water right away
> because it is not
> > round and has little
> strength to keep it round.
> >
> Hank--------------------------------------------
> > On Tue, 6/9/15, Alan James 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: Tuesday, June 9, 2015, 7:15
> PM
> >
> > Hi
> >
> > Alec,that one
> > is also showing 40psi.This is
> > a
> > Sean type
> problem.I guess
> > it's a bit like
> snapping a match stick.
> > Anyone can
> do
> > it, but try breaking it
> > bycrushing
> > it from
> end to end. In this case
> > you can
> squeeze the tube
> > & bend it but
> > try crushing
> > it
> cross sectionally with
> > even pressure
> all
> > around.A
> >
> > solution may be to just squeeze up a
> section of the hose
> > with a hose
> crimpso that a
> >
> >
> point of weakness is created for the water pressure to
> > continue crushing thetube from
> > there along it's length.Alan
> >
> > From:
> Alec Smyth
> > via
> >
> Personal_Submersibles
> >
> > <personal_submersibles at psubs.org>
> >
> > To: Personal
> > Submersibles General Discussion
> > <personal_submersibles at psubs.org>
> >
> >
> > Sent:
> >
> > Wednesday, June 10, 2015 10:55 AM
> >
> > Subject: Re:
> > [PSUBS-MAILIST] Dive report:
> > Snoopy at Seneca
> >
>
> >
> > Wow. If
> > there is no mistake that is really
> > counter intuitive,
> >
> because the hose feels
> > super pliable in
> your fingers -
> > almost like
> > those yellowish rubber lab hoses if you
> know
> > what I mean. The size I'm
> using is half
> > the wall
> > thickness of what you calculated
> > with, if that makes a
> > difference. It's
> > 1/4" ID X 3/8" OD X
> > 1/16"
> >
> thickness.
> > Alec
> > On Tue,
> > Jun 9,
> 2015 at 6:46 PM, Alan James via
> >
> Personal_Submersibles
> > <personal_submersibles at psubs.org>
> > wrote:
> >
> >
> > Alec,I had a
> > look at the
> > specs
> on that link. Thanks.The
> > 3/8"
> ID
> > x 5/8" OD X 1/8" tube is
> rated for
> > 40psi internal pressure.As
> this
> > is for fuel there could be a
> safety margin of
> > 4x, so 160 psi
> > burst pressure.I ran a
> > couple of plastics I have in my
> pressure
> > program through
> > internal and
> >
> thenexternal
> > pressure, & the
> maximum
> > external pressure was 2/3rds
> the
> > internal
> > in
> both cases.This
> > could mean that it
> would
> > take 106 psi before the hose
> would
> > equalize
> >
> significantly.The
> > diameter would
> maybe
> > shrink a bit before
> > collapsing.Cheers
> >
> Alan
> >
> >
> >
> > From: Alec
> Smyth via
> > Personal_Submersibles
> <personal_submersibles at psubs.org>
> > To: Personal
> >
> Submersibles
> > General Discussion <personal_submersibles at psubs.org>
> >
> > Sent: Wednesday,
> June
> > 10, 2015 10:11 AM
> > Subject:
> > Re:
> > [PSUBS-MAILIST] Dive report: Snoopy
> at
> > Seneca
> >
>
> > The stuff
> >
> I'm using is really flexible, and has a
> > wall thickness
> > of
> only 1/16". I'm
> > having trouble
> imagining that
> > the seal
> > could offer less resistance than this,
> it's
> > very soft. See McMaster item
> #5552K25.
> > Best,
> > Alec
> >
> > On Tue, Jun 9, 2015 at 5:29 PM, Alan
> James
> >
> > via
> Personal_Submersibles <personal_submersibles at psubs.org>
> > wrote:
> >
> >
> > Does anyone
> (Sean)
> > have the
> >
> material specifications in theirpressure programs for the
> > soft pvc that we
> >
> would be using inour
> > flexible
> compensation hoses?The nearest I had
> >
> was nylon, & that had
> > a crush
> depth of
> > 8,000ftfor a 1 meter long
> tube, 10mm diameter &
> > 2mm wall
> thickness.I was
> >
> >
> thinking of using oil filled light housings with the
> > wiringrunning through
> >
> > flexible hose as
> compensation, but are having second
> >
> thoughts.Alan
> >
> > From: Sean T.
> >
> Stevenson via
> > Personal_Submersibles
> <personal_submersibles at psubs.org>
> > To: Personal
> >
> Submersibles
> > General Discussion <personal_submersibles at psubs.org>
> >
> > Sent: Wednesday,
> June
> > 10, 2015 6:11 AM
> > Subject:
> > Re:
> > [PSUBS-MAILIST] Dive report: Snoopy
> at
> > Seneca
> >
>
> > I have
> >
> always
> > been a fan of oil compensation
> at
> > higher than ambient
> > pressure, for a variety
> > of reasons. The only real downside
> > is the
> >
> environmental impact of potentially losing oil to the
> > surrounding water in the event of a
> leak, but
> > that impact
> > can be mitigated with oil
> > selection. Positive pressure
> > allows you to
> >
> compensate for volumetric changes in your
> >
> > compensated volumes
> due to the exterior pressure, as well
> >
> as
> > for thermal expansion of the oil,
> and if
> > you have any
> > leakage at all, you leak oil
> > out, rather than water in,
> > which can be an
> >
> expensive lesson. Additionally, if you
> >
>
> > provide the bias with something like a
> spring loaded
> > cylinder or elastomeric
> bladder, you can
> > instrument its
> > displacement for accurate
> > monitoring of demanded
> > compensation volume,
> > and potentially detect leaks well in
> >
> > advance of when they
> actually become a problem.
> >
> Ambient-only compensation has the disadvantage
> > of not
> > compensating
> for boundary-layer
> > viscosity effects
> on
> > rotating shafts,!
> > density
> >
> differences
> > (gravity induced exchange
> and/or centripetally
> > accelerated
> fluid) and other small but
> > cumulative
> effects
> > that can contribute to
> > water ingress.
> >
> >
> >
> >
> >
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