From: Dale Rogers <rogersda@cox.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Ingnition coils
Date: Tue, 15 Jun 2004 10:06:30 -0400
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Hi All,

   Giff Marr wrote:

> If my memory serves me, I believe that the Northstar engine has coils that
> serve two cylinders. Would this be a better weight solution then installing
> 4 [13B] or 6 [20B] coils.

   This could be a genuinely bad idea.  All such coils that 
I'm familiar with operate on a "waste spark" principle - 
i.e. the "ground" for both ends of the high voltage path 
is at the plug in each of the served cylinders.  The 
pairing is such that one cylinder is at the top of the 
compression stroke and the other is at the top of the 
exhaust stroke.  The only comparable condition in a rotary 
engine is with simultaneous firing of both plugs on the 
same rotor. 

   Such an arrangement would considerably diminish the 
safety redundacy of the ignition system - in that if a 
coil fails, one completely loses the power on that rotor.
Moreover, if one plug goes bad, it can diminish the quality 
of the spark in of the other plug on that coil - which 
also could have the effect result of no power from that 
rotor.

my $.02

Dale R.
COZY MkIV-R #1254