RE: [PSUBS-MAILIST] Seals again

[Duncan Milne <milned@teckcorp.ca>]

Pat,
	Steve is just pointing out that it is important to realize
that SOME redundancies can actually INCREASE the overall risk of failure.
The reason why a lot of dive shop owners in your 36 years of diving, (33
years for me),
have given up on DPV's is that until recently most of them were developed
and
manufactured without an understanding of the mechanical and environmental
conditions
that they would be subjected to - flimsy switches, thin plastic housings
that collapsed
at less than 200 FSW, lack of battery offgas isolation leading to explosion,
etc.
In cave diving even Gavin scooters are towed as spares during major
penetrations,
see http://www.wkpp.org/  in recognition of the possibility of failure even
with a well designed unit.
Along with the use of double tanks with isolation manifold,  two first and
two second stage regulators,
three lights, etc., they illustrate the need for redundancies that are
functional under multi-task
situations by both the diver and his buddy in an overhead environment.
	I submit that it doesn't get more mission critical than naked 3
miles back in a cave at 300 feet.
I know that I certainly don't plan on  taking my 2 man 150 meter dry sub,
(which has now passed the half way mark
for completion), into an overhead environment.  But for the cost, however, I
would have been happy to have
strapped on a couple of Gavin DPV's in place of the 48 VDC 3 Hp PM motors
that I am using.
	Duncan Milne
	Vancouver, B.C., Canada
	IANTD EANx Cave #5407
	NACD #2479
	Honorary Newtsuit Pilot #008   

> -----Original Message-----
> From:	Captain Nemo [SMTP:vulcania@interpac.net]
> Sent:	Wednesday, October 04, 2000 4:59 AM
> To:	personal_submersibles@psubs.org
> Subject:	Re: [PSUBS-MAILIST] Seals again
> 
> 
> ----- Original Message -----
> From: "Steve Lindblom" <s_lindblom@conknet.com>
> To: <personal_submersibles@psubs.org>
> Sent: Wednesday, October 04, 2000 5:33 PM
> Subject: Re: [PSUBS-MAILIST] Seals again
> 
> 
> "Why is the KISS principle so suspect on this list?"
> 
> Steve,
> Unless you're talking about some esoteric principle devised by Gene
> Simmons,
> I take that term to mean "Keep It Simple, Stupid!"
> 
> Sounds like you're saying system redundancy in submarines is not only
> unnecessary, but also more dangerous than beneficial; and everyone who's
> been using it should now do without it because people are too stupid to
> design, build, or operate anything more complex than the most rudimentary
> machines.  That is contrary to everything I've ever read about submarine
> design.
> 
> Of course, you're entitled to your opinion; but I doubt you'll convince
> automobile manufacturers to do away with emergency brakes simply because
> multi-chamber master cylinders reduce the possibility of failure; or
> convince us that pressure compensation does not safely improve
> functionality
> and reliably in the submersible motors we propel our submarines with, when
> for years it's been proven that it does.
> 
> In your message to Ken Martindale three weeks ago, you didn't even know
> that
> applying direct power to the motor could zap the magnets; now, all of a
> sudden, you're an authority.  Amazing!
> 
> And regarding the reliability of DPV's: in my 36 years of diving I've
> known
> a lot of dive shop owners who stopped messing with them because of all the
> problems they had; and a lot of seasoned divers who say they are "junk".
> To
> tell people that such motors are reliable enough to make proven support
> systems undesirable and unnecessary in submarine applications is
> irresponsible, at best.
> 
>  I wonder if you practice what you preach.  Do you have a submarine of
> your
> own which employs your revolutionary double-seal system, and which you've
> done much actual operational testing with?  I'm not talking about a model,
> a
> CAD program, something you read about, or your buddies' DPV: I'm talking
> about an actual boat you spent years, bucks, blood-sweat-and-tears to
> build.
> I don't think you do, because if you did, you wouldn't be talking about
> getting by with "good enough"; you'd want to protect that baby with all
> the
> best backups you could get.
> 
> Pat
> 
> 
> 
>