Re: [PSUBS-MAILIST] Drive shaft alignment & sopport.

["Gary R. Boucher" <engineer@sport.rr.com>]

Walter,

     What you think of my judgement is your business and not a major 
concern to me.  This open discussion, I hope, has been informative for 
those choosing to read it.  Anyone reading these threads has an opportunity 
to make judgements as to what they find useful or useless.  I have a 
feeling that the thru-hull issue is probably not the only practice of yours 
that I would take issue with.  But, at this point what the PSUBer decides 
to do is up to their own judgement.  All the points and counter points that 
I know of on these issues have been made.
     Unless my BS warning light once again illuminates brightly, I will 
attempt to avoid "Beating these Dead Horses."

Gary Boucher


At 10:19 PM 11/22/2002, you wrote:
>Gary,
>
>On hydraulic propulsion I do think it falls in the category of
>unnecessary complexity and expense with a performance penalty as well..
>As for your engineering judgement outside this I know nothing and have
>no opinion. My comments on over engineering were generic to a commonly
>encountered circumstance not a judgement directed at any individual.
>
>On the matter of the thru hull cable fitting your concerns seem to be
>based on a rubber insulated cable.  This is the type I specifically
>advised against.  The type I did recommend has a solid PVC outer
>insulation.  PVC is not only much stronger it slowly cold flows where
>compressed by the O-rings.  This locks it into place very securely.  The
>50 lbs. extrusion force mentioned in the example is far below  what it
>will withstand.  Nothing you have offered in the way of theoretical
>dissent contradicts this and it is easily tested.  This is beginning to
>look like an example of the NIH factor.
>
>NIH is often the impetus to coming up with complicated solutions and
>ignoring simple proven ones that are already available.  NIH is short
>for Not Invented Here.
>
>Walter Starck
>Golden Dolphin Video CD Magazine
>The premiere publication of diving and the ocean world.
>www.goldendolphin.com
>
>
>
>
>----- Original Message -----
>From: "Gary R. Boucher" <engineer@sport.rr.com>
>To: <personal_submersibles@psubs.org>
>Sent: Saturday, November 23, 2002 10:35 AM
>Subject: Re: [PSUBS-MAILIST] Drive shaft alignment & sopport.
>
>
> >
> > >Gary,
> >
> > Starck wrote:
> >
> > >I do confess the comment you so object to was a bit tongue in cheek
>to
> > >see if you would bite.  If you wish to take it seriously however it
>is
> > >not entirely BS.  Certainly engineers do make possible much truly
>superb
> > >technology but this does not obviate abundant examples of  poor
> > >engineering involving needlessly complicated ways of doing things and
> > >failing to take advantage of  readily available well proven
>solutions.
> >
> > You're actual tongue and cheek, yet not entirely BS comment, is held
>by a
> > number of people I have met.  One close friend feels that I am the
>only
> > engineer he has any respect for.  He can't stand all the others.  The
> > fellow does superb work and is the best craftsman I have even known as
>he
> > builds aircraft from the ground up.  These are not kit planes, he does
> > extensive modifications of existing high-performance planes and
>constructs
> > some of his own designs.  I have a great deal of respect for his
>mechanical
> > judgement, yet there is an element missing.  He never calculates
> > anything.  He shoots from the hip and it may someday get him in
>trouble.
> >
> > You apparently, because of my use of hydraulics, feel that I am a
>person
> > that applies needlessly complicated approaches to simple problems.  I
>will
> > let my work stand for itself.
> >
> > >As for reliability of the thru hull cable fitting I described your
> > >concerns are justified on the basis of not trusting your life to info
> > >posted on the internet by parties unknown.
> >
> > Your posting on the Internet has nothing at all to do with my
>unwillingness
> > to adopt your method for deep water thru-hull penetration.  Your
> > credentials have nothing to do with it either.  If you had a doctorate
>in
> > mechanical engineering with extensive work in the field, that would
>not
> > mater to me either in this case.  I will let your note continue.
> >
> > >You seem to be saying though, that you only trust theory not the
>results
> > >of empirical experience.
> >
> > If you knew me better you would not even suggest such.  I am a strong
> > believer in empirical experience and judgement.  Much of my work is
>based
> > on intuition.  I know when to go with intuition and I know when to
>shift to
> > hard numbers.  No one I know and no body that works with me thinks of
>me as
> > a theoretical engineer.
> >
> > >For the most part we really
> > >don't truly know why things work but just that they do.  If on the
>other
> > >hand, what you are referring to as theory is just the principles and
> > >formulas which  quantify  our empirical knowledge please do apply
>them
> > >to the problem at hand.
> >
> > You seem to be trying to parse my reasoning into two categories.  One
> > practical and the other theoretical.
> >
> > >   The parameters are simple, force, coefficient of friction, and
>modulus
> > > of elasticity.
> > >    I have stated what I have
> > >found from experience.  You imply theory does not support this.  I
>would
> > >be genuinely interested in learning what theory, how it differs, and
> > >what safe limits it predicts.
> >
> >      Part of my profession is teaching physics at the university
> > level.  Almost every day I deal with factors such as force,
>coefficients of
> > friction, and Young's Modulus.  All the problems work out so nicely on
>the
> > board.  All the numbers agree to three decimal places with the answers
>in
> > the back of the book.  It would give the student the impression that
> > everything in physics is just so precise.  But, the truth is far from
> > this.  Translating pure theory to practice in the real world is not so
> > one-to-one as a person might think.  These factors are good for
>predicting
> > estimates and ranges of expected performance, but often fall way short
> > because the simple parameters do not exactly match or there is or can
>be
> > many factors too complex to accurately estimate.
> >      In the case of the wire mentioned in an earlier post (0.40 inches
>in
> > diameter) the load calculated was 55 pounds.  That means that the
>wire's
> > insulation, not the wire itself must be able to take a compressive
>load of
> > this value.  Should there be any exceptions in any of the parameters
>or
> > just a flaw in the wire's insulation itself, failure could easily push
> > uninsulated wire through a hole intended for the  insulated wire's
>diameter.
> >      I can run numbers on the O-ring penetration using estimates for
> > coefficient of friction and the like.  But my person intuition, my
> > engineering intuition, my knowledge of how such parameters vary in
>real
> > live tells me to not get in that sub at that depth.  You are simply
>making
> > a jacket of rubber into a pressure bearing structural component.
> >
> >      If you want a good example of rubber failure consider how many
> > unwanted births are caused by some component made of similar material
> > failing when it is supposed to hold up under the rated load!
> >
> > Gary Boucher
> >
> >
> >
> >
> >
> >
> >
> > Let me state just a few, but I am sure, not all of the not so simple
>factors.
> >
> > Coefficient of friction varies greatly with age of a material,
>lubrication,
> > moisture content etc.  Wire insulation properties also vary with age
>and
> > conditions.  Given the example of a 0.4 diameter wire I used in a
>previous
> > post, the loading on the insulation is about 44 pounds per lineal
> > inch.  Assuming a "Wet" coefficient of friction for rubber against
>O-Ring
> > of 0.6 the loading will be around 73 pounds per lineal inch.
> >      O-Rings are not intended for
> >
> >
> >
> >
> > >Walter Starck
> > >Golden Dolphin Video CD Magazine
> > >The premiere publication of diving and the ocean world.
> > >www.goldendolphin.com
> > >
> > >
> > >
> > >
> > >
> > >
> > >----- Original Message -----
> > >From: "Gary R. Boucher" <engineer@sport.rr.com>
> > >To: <personal_submersibles@psubs.org>
> > >Sent: Saturday, November 23, 2002 12:01 AM
> > >Subject: Re: [PSUBS-MAILIST] Drive shaft alignment & sopport.
> > >
> > >
> > > >
> > > > Starck Wrote:
> > > >
> > > > >If you enjoy problems and complicated expensive solutions
>complete
> > >with
> > > > >all sorts of reasons why what works in practice is no good in
>theory
> > >and
> > > > >should be ignored consult an engineer..  They can  solve problems
> > >that
> > > > >don't even exist and create new ones no one else has encountered
> > >before.
> > > >
> > > > That is absolute B.S.  No matter what your profession is, you find
> > >those
> > > > who are incompetent, unknowing, and irrelevant.  The engineering
> > >profession
> > > > is no exception.  However, what I have found through the years
>over
> > >and
> > > > over is people who have limited knowledge of technical issues who
>make
> > > > broad-ranging and very verbal assumptions.  These people, because
>they
> > >do
> > > > not completely understand the underlying theory, believe that
>those
> > >who do
> > > > understand and can employ that theory are somehow living in their
>own
> > >world
> > > > using tools that are irrelevant to good design practice.
> > > >
> > > > I will give a case in point.  I know someone that pressure chamber
> > >tested a
> > > > submersible window design using Lexan.  The window was one-time
>tested
> > >to
> > > > beyond the rated operating depth of the sub.  The Lexan actually
>had a
> > > > noticable bow inward under pressure creating a convex/concave
>window.
> > >The
> > > > logic here was simple and of course not needing any real theory,
> > >certainly
> > > > not any engineering expertise.  The logic simply put was that, if
>the
> > > > window did not fail under one cycle of pressure, somewhat over the
> > >rated
> > > > operating depth of the sub, coupled with the fact that Lexan
>seemed a
> > > > wonder material and would never actually break, everything was
>fine.
> > >This
> > > > is a typical assumption made by someone that does not understand
>the
> > > > properties of the material.  "No engineering theory needed here.
>We
> > >just
> > > > proved that it will work.  We built 100 of them and never had a
> > >problem."
> > > >
> > > > There is NO way I want to go down below very shallow depths in a
>sub
> > >with
> > > > thin Lexan windows.  Likewise, there is NO way I want to go down
>to
> > >1000
> > > > feet in a sub that uses wire penetraters made from flair fittings
>and
> > > > O-Rings relying on nothing but the wire's insulation to keep the
>water
> > >out.
> > > >
> > > > You do not have to be an "engineer" to construct a safe
>submersible,
> > >if you
> > > > find outside help from qualified individuals, but the PSUBer has
>the
> > > > responsibility to determine who to get advice from.  After many
>years
> > >of
> > > > this type of work, I feel that I have just about reached the level
> > >where I
> > > > know what I don't understand and where to get good help.
>Basically, I
> > >am
> > > > NOT an expert.  But, I know where to find good advice.
> > > >
> > > > Gary Boucher
> >
> >