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Re: [PSUBS-MAILIST] motor thought

I agree in principal, but spent a few uncomfortable hours in pretty deep water struggling with entanglements. The Cousteau jet pump was primitive, but effective. By accepting the obvious limitations in power, they were able to work three different submersibles through many hundreds of dives without entanglement. There is something to be said about that kind of safety record, and I think it is worthy of consideration as an alternative method of propulsion for psubs. Mind you, I haven't done it, either. My K-350 is going back together this summer pretty much as designed (except for lessons learned by Dan and a few others, which I will incorporate in one way or another). However, I ain't giving up on some kind of pump for future reference.
-----Original Message-----
From: Jay K. Jeffries <bottomgun@mindspring.com>
To: personal_submersibles@psubs.org
Sent: Sat, 8 Apr 2006 18:04:53 -0400
Subject: RE: [PSUBS-MAILIST] motor thought

Jon is correct in that the underwater jet nozzle is inefficient for
propulsion.  Review of the many PSUBS, commercial, and research subs built
over the years will show few applications of jet nozzles.  A propeller is
more effective and simpler to construct from off the shelf items.  This
efficiency can be improved with a Kort duct around the propeller.

Jon's turbine concept is used in high speed military subs and torpedoes.
There is a Kort nozzle around the prop (rotor) and a static series of blades
(stator) is sometimes found after the prop.  Extreme large amounts of energy
are expended in this propulsion scheme.
Jay K. Jeffries
Andros Is., Bahamas


-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Jon Wallace
Sent: Saturday, April 08, 2006 10:43 AM
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] motor thought


I don't know the efficiency of a water jet, but suspect it is somewhat lower
than a prop.  And yes, it would definately depend upon nozzle velocity and
pressure.  There are two ways to look at this.  One is to use the pump
pressure through a simple nozzle jet similar to a twirling lawn sprinkler
(this is what cousteau's sub did).  The other, imagine taking a water
turbine from a hydro-electric plant (down-scaling of course) and replacing
the stator/magnet with a propeller.  You mount this contraption like a
regular minn-kota motor, but use hose or piping to duct the flow from the
pump to the turbine end of the unit.  The high pressure water flow (relative
to ambient pressure) from the pump is directed to the turbine (squirrel cage
perhaps?) which drives the propeller.


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