Re: [PSUBS-MAILIST] motor seals

["Gary R. Boucher" <protek@shreve.net>]

Dave,
     Look at their Item #46.  I think the #37 is overkill.  The #46 is 1.25 
by 0.5 inches, which is a more manageable size.  They are $12.00 
each.  They also have curved magnets which can be operated near the walls 
of a tube where the opposite coupling would be around the outside of the 
tube.  I could see some possibilities here.

GB

At 11:18 PM 8/15/00 , you wrote:
>Hey Gary:
>WOW! you were not exaggerating about the strength of these magnets.  I found
>a surplus supplier on the net:
>http://www.wondermagnet.com/dev/magnet37.html
>Here's what they had to say about one of their larger magnets:
>
>ITEM #37
>Price: $35.00 ea.
>dimensions: 1.5" diameter, 1" thick
>We have a fair number of these large magnets in stock. These are Nickel
>plated.
>These magnets are not available through our online form, and are not for the
>general public; we will sell these only for use by legitimate commercial or
>industrial/research applications. To order these, please send us an email or
>call (877) 944-6247. These magnets are not available for purchase through
>our web site.
>We take these precautions because, due to their size, these magnets require
>extremely special handling. Gloves and eye protection must be worn at all
>times. Folks who are unfamiliar with magnets of this strength are likely to
>wind up hurt. We generally prefer to sell smaller items, so we would like to
>sell these quickly and we would be glad to offer substantial quantity
>discounts on large orders.
>
>© 2000 ForceField
>toll free (877)944-6247
>
>A better item for our purposes would probably be
>http://www.wondermagnet.com/dev/magnet45.html
>
>TTYL,
>Big Dave
>
>
>-----Original Message-----
>From: Gary R. Boucher <protek@shreve.net>
>To: personal_submersibles@psubs.org <personal_submersibles@psubs.org>
>Date: Tuesday, August 15, 2000 9:24 AM
>Subject: [PSUBS-MAILIST] motor seals
>
>
> >     I have an idea, not an original one I will admit, but I have some
> >thoughts on magnetic coupling.  I played around with the idea of using
> >magnetic coupling to make my scanning sonar have no seals, leakage, etc.  I
> >purchased several rare-earth magnets from a surplus vendor.  Some of the
> >new permanent magnet motors use these and most people can not imagine how
> >powerful they can be.  I literally hurt my hand a couple of times when I
> >got two of them in close proximity and they came together with my fingers
> >in the middle.
> >     I believe there may be a way to engineer a coupling with these
> >high-strength magnets.  A couple of thoughts on that; these magnets are so
> >powerful that when I took a piece of aluminum plate 3/16 inch thick, tilted
> >it on a 45 degree incline, and released one of the flat magnets it creeped
> >slowly down the aluminum.  This was due to the fact that the very strong
> >mag flux moving through the aluminum (conductor) created currents in the
> >metal opposing the flux created by the magnet.  This effect will drain
> >energy out of any coupling system where metal is used between the
> >magnets.  The faster the rotation, the more energy lost.  If the magnets
> >are placed on either side of a flat plate for the coupling you have the
> >additional problem of using a flat, non-metallic plate to withstand the
> >water pressure.  I believe that a tube of non-metallic material perhaps PVC
> >or fiberglass (not composite - carbon fibers conduct!) could be used.  This
> >could withstand the pressures because of its geometry.  Also, I believe
> >that the rotating components could be "potted" in an epoxy or even
> >fiberglass or composite.  With the rotating components, you would not have
> >to worry about small currents as you would with the housing, since both
> >systems are turning at exactly the same RPM.  Metal could also be used for
> >these components.  What ever was used for the rotating magnet holding
> >system, you would have to balance it to minimize vibration.
> >     If both motor and propeller magnets are rotating at the same speed
> >there will be very little loss of power except for the drag of the water
> >around the prop side magnet.
> >
> >Gary Boucher
> >