VAWTBearingDistance:

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   Calculates minimum rotor shaft bearing distance. 
   Assumes axial load capacity of bearings is appropriate for load.
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   Form:
   dist = VAWTBearingDistance( d, yS, F, FoS )
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   Inputs
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   d          (1,1)  Data structure
                     .do         (1,1)  Outer Rotor Shaft Diameter (m)
                     .di         (1,1)  Inner Rotor Shaft Diameter (m)
                     .A          (1,1)  Bearing to Blade Distance (m)
                     .B          (1,1)  Blade mounting distance (m)
   yS         (1,:)  Yield Strength (Pa)
   F          (1,1)  Axial Load (N)
   FoS        (1,1)  Factor of Safety

   -------
   Outputs
   -------
   dist       (1,1)  Distance (m)

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   Reference: 

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   Copyright (c) 2009 Princeton Satellite Systems, Inc.
   All rights reserved.
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