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

http://www.pyiinc.com/?section=pss_shaft_seal&sn=4


"MBS" wrote in message
m...
I am trying to waterproof a small electric motor (submerged) so that
shaft will be sticking out of waterproof enclosure. Can anyone point
me to a source of water sealed bushings or bearings for this sort of
application? I have been looking all over the net and can't seem to
come up with ideas or supplies to do this. The shaft size will be =
1/4"

Thanks!
Bailey--

"Paul" wrote in message
news:PxVwb.309584$Fm2.326329@attbi_s04...
http://www.pyiinc.com/?section=pss_shaft_seal&sn=4


"MBS" wrote in message
m...
I am trying to waterproof a small electric motor (submerged) so that
shaft will be sticking out of waterproof enclosure. Can anyone point
me to a source of water sealed bushings or bearings for this sort of
application? I have been looking all over the net and can't seem to
come up with ideas or supplies to do this. The shaft size will be =
1/4"

Thanks!
Bailey--


Just an idea...

Would it not be possible to submerge the whole electric motor unit in a kind
of container completely filled with a nonconductive (non toxic) oil. If e.g.
the container is kept upright with the shaft protruding downwards and the
oil being lighter than water, it seems to me that the motor could be safely
operated without expensive water sealed bearings and/or bushings. As the
container would remain opened to the surrounding water, the hydrostatic
pressure inside and outside would be equal. Fluids can not easily be
compressed so this unit could be used in any depth of water with only a
lightweight protective container and a closely fitting shaft-tube leaving a
small enough opening for pressure compensation but too small to allow the
spilling of the oil when tilted. The only setback would be that the motor
could only be tilted a little less than 90° from the upright position and
that the internal turbulence caused by the rotor (at higher rpm) would
certainly slow down the motor (depending on the construction of the motor).
With this system one could easily insulate the motor completely from the
container/vessel. (No maintenance, no galvanic effects)

JP

Condom?

runs away

;-)

OK now i know this post is quite old & you've long since solved your problem but ive taken it upon myself to do the exact same thing without buying expensive purpose-made stuff, just to use the stuff i already have lying around or cheaply bought!

Stumbled across the link below that ive tried out and it works very well, i can settle for a 95% waterproofed shaft seal as my little project is making a liquid pump, but its a very good way of keeping water/liquid out the motor!

I also will be making a submarine next year some-point so i'll try to reverse-engineer an expensive-type shaft-seal (on the cheap of course!) as long as i can find and understand the basic principal of one online, i mean, the schematics gotta be on the web somewhere !

Hope this helps you & everyone else!

http://members.tripod.com/robomaniac_2001/id197.htm

Merry Xmas & a Happy New Year to All !!!

;-)