Re: [PSUBS-MAILIST] motor seals

["Paul Suds" <paul_suds@hotmail.com>]

I just thought of some other things that may want to be considered in the 
magnetic coupled thruster design: typically, you want the inner driver to be 
90 degrees out of phase when running. This will provide the greatest torque 
transfer. At 90 degrees, the lines of force of a magnet on the drive 
transfer surface will be between two of the magnets on the follower transfer 
surface. This is the optimal location during operation. The drive magnet 
(one of many), will be attracting the opposite pole magnet (#1) on the 
follower and at the same time, repelling the opposite pole magnet (#2) on 
the follower. One advantage and disadvantage of the magnetic coupling: The 
advantage is that you can't overload your motor. If the design torque on the 
prop is matched to the design force of the coupling (another calc), and the 
prop load increases as a result of the prop getting caught up, slip will 
occur on the coupling. The downside of this is that if the torque force 
exceeds the magnetic coupling force (bad design), the coupling will slip at 
high torque. The prop will not align with the drive tranfer surface until 
the drive surface is reduced to the same speed as the transfer surface. The 
bottom line is that you will have to stop your motor, or at least slow it 
down significantly.
The coupling design force must equal the maximum design torque force.
Comments?
Suds
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