Sort of like an aquarium powerhead? I think it's the same idea. Many
types of powerheads have a removeable shaft. The impeller is coupled to the
permanent magnet, and the whole thing spins about the shaft (but the shaft
itself does not rotate; it only serves to give the moving parts something to
rotate about). Powerheads are designed to be run submersed anyway. Maybe you
could adapt a propeller to it? The whole motor could then be mounted
externally to your robot. Plus, if it ever went bad, it would be easy to
swap out. Too bad they require AC. But that is easy enough to do by building
a simple 50% oscillator and powering a transformer in reverse.

Maybe this is one of those hair-brained ideas that's better shelved as an
intellectual exercise only :)


> -----Original Message-----
> From: Roman Black [mailto:fastvid@EZY.NET.AU]
> Sent: Tuesday, July 31, 2001 6:05 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [OT]: Underwater robots
>
>
> > >         I have some ideas for underwater robots that I would
> > > like to try.
> > > So now that I know that there is someone on the list that has
> > > experience
> > > with Underwater Robots, I have some questions.  What type of
> > > motors do you
> > > use for propulsion?  How do you seal motors or points where
> > > wires protrude
> > > from an enclosure from leakage or high water pressure or .
>
>
> Hi Scott, if you can do some fabrication you
> can get a pancake motor from any modern VCR
> (capstan motor), these have a flat magnet
> assembly and and a flat coil assembly.
> Sometimes the bearing assembly is removable.
> If you could rig the bearings up the electric
> part could watertight with only the perm magnet
> rotor and shaft in the water. :o)
> -Roman
>
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