From: Dale Rogers <rogersda@cox.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Wire (and LS1 Coils and Harness II)
Date: Sat, 26 Jun 2004 14:51:08 -0400
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> From: "Ed Anderson" <eanderson@carolina.rr.com>
> Date: 2004/06/26 Sat PM 12:33:09 EDT
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Subject: [FlyRotary] Re: LS1 Coils and Harness II
> 
> The terminals for the plugs will handle 16-18 AWG wire and are rated for 14
> amps, so even 18 AWG should be more than adequate for a single coil.


Hi All,

   This seems to be an area where I'm going to have to reorient 
my thinking.  For years, I've been wiring trailers and after-
market accessories, and I've often been appalled at the barely- 
adaquate wiring I've found in place.  I've used far more 14g wire 
than 16 or 18, just to be sure it was safe.

   Now I'm facing the wiring of an airplane, and 14g - besides 
being harder to find in Mil-22759 - is _heavier_ than 16 or 18g.

   I'm going to have to pay a lot more attention to what current 
my circuits will be expected to carry and use wire that will 
*just* to the job (with an appropriate safety factor, of course.) 

   And it isn't just the instantaneous load I have to consider.  
In the case of the coil, wasn't the instantaneous draw about 9A? 
But that's pulsed DC.  The RMS flow is probably considerably 
less, but how much less?  Using Bob Nuckols' chart, it appears 
that 18g wire is good for 7A before the temperature increase 
breaks 10*C; if I don't mind wasting some watts, I get push 10A 
through it for a 35 degree increase.  But that's for 100% duty 
cycle; what's the duty cycle of one coil at 6000 rpm?  If it 
was - say - 50%, then 18g would be plenty. 

   Learning all this, to finish this aircraft is definitely going 
to stretch my talents a bit.

Dale R.
COZY MkIV-R13B #1254