Brian Whatcott wrote:

Place three in series in the housing, and fix the housing on the motor
in some waterproof way. This will put you in with a chance.

That is not a very promising approach.

If keeping the motor dry is important, filling the housing with a light
oil under slight positive pressure via a compensating bellows is the way
to go. A standard lip seal will keep junk out and the oil in. The
compensating bellows will allow operation to any depth with no fear of
flooding the housing.

Rick

Hmmm....a trolling motor uses a single seal and no depth compensating
bellows.

Still, for decent depths, rather than the shallow depths the
questioner mentioned, this would be a sensible suggestion.
Either way, lip seals
have lips facing the higher pressure side, to prevent lift off, or
they face both ways in some applications....

Brian Whatcott Altus OK

On Sun, 23 Nov 2003 19:56:48 GMT, Rick
wrote:

Brian Whatcott wrote:

Place three in series in the housing, and fix the housing on the motor
in some waterproof way. This will put you in with a chance.

That is not a very promising approach.

If keeping the motor dry is important, filling the housing with a light
oil under slight positive pressure via a compensating bellows is the way
to go. A standard lip seal will keep junk out and the oil in. The
compensating bellows will allow operation to any depth with no fear of
flooding the housing.

Rick

This is a completely theoretical, uninformed suggestion, so take it for what
it's (not) worth...

Put the motor in a totally sealed chamber. The motor turns a large disk,
which is positioned adjacent to the rear wall of the chamber. Strong magnets
are placed around the edge of the disk. On the other side of the (thin as
possible) rear wall is a matching disk, with magnets around its rim. This
second disk is hooked to the prop shaft. If the magnets are strong enough,
wouldn't this setup transmit enough torque to spin the prop, while keeping
the motor in a totally sealed chamber?

Remember: theoretical, uninformed! (g)

Alex

Brian Whatcott wrote:

Either way, lip seals have lips facing the higher pressure
side, to prevent lift off, or they face both ways in some
applications....

The technique I mentioned is what we used on the thrusters of manned
submersibles working down to 2000 meters. We used two lip seals, back to
back, on the shaft to keep the oil in and water out.

Rick