Newsgroups: comp.robotics
Path: brunix!cat.cis.Brown.EDU!agate!howland.reston.ans.net!pipex!uknet!liv!swain
From: swain@liverpool.ac.uk (Mr J.R. Swainston)
Subject: Re: Underwater motors
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References: <1994Jul12.173350.29777@lds.loral.com> <307704$o5l$1@heifetz.msen.com>
Date: Thu, 28 Jul 1994 14:17:54 GMT
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Allen Majorovic (amajorov@garnet.msen.com) wrote:
: Brian Dombrowski, 5424 (dombrows@lds.loral.com) wrote:

: : Hi:

: : I'm brainstorming on how to use DC motors for underwater propulsion
: : of an ROV.  The big problem is to keep water from getting inside
: : of the ROV or motor.  For this reason I'd like to avoid a direct shaft

We have looked into the same problem here for our ROV.  The solution we use is 
a prop shaft with two o-ring seals which goes into an 8:1 reduction gearbox.  
The intermediary gearbox is filled with grease, sealing the system further.  
The DC motor then drives this gearbox.  This motor has been pressure tested to 
500m and works fine.

For a cheaper solution fill the casing with either non-electrolytic oil (causes
a bit of damping) or parrafin (check if your windings will take it).  Then a 
simple O-ring seal with suffice, with direct drive.  However, this system may
cause a large amount of stiction in the thruster system.


--
*	Mr.J.R.Swainston (swain@unix.liv.ac.uk), 051-794-4539, ex 4610  *
*	Dept of Electrical/Electronic Engineering,			*
*	The University of Liverpool, PO Box 147, Liverpool L69 3BX, UK	*
