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Date: Thu, 24 Feb 2005 12:11:01 -0500
From: Ernest Christley <echristl@cisco.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: E-shaft permanent magnet alternator
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Jim Sower wrote:

> I don't see the point of two primaries (unless you're using 1920s era 
> technology like mags).  My notion is to have a good, solid ND primary 
> and either a [small] backup battery or [small] backup Alt.  If I have 
> redundant primaries, I'm probably too heavy, and (just me) more 
> tempted to drive around with one failed while I wait on parts or 
> something.

Jim, my goal is to eliminate the belt driven alternator entirely.  No 
belt.  No pulley.  No heavy alternator hanging off the side of the 
engine on a heavy cantilevered bracket.  No need for a cowl bump to give 
it clearance.

I'm looking for at least a 35A primary and 20A secondary.  I'm actually 
quite comfortable with the idea of flying with only a primary, but if 
you look at these things they are like an alternator with all of the 
heavy parts thrown out.  The backup is cheap, weight wise.  My guess is 
that the difference between the 20A and 35A unit is the wire guage used 
in the coils, and you'd need an ounce scale to tell the difference.