Mailing List flyrotary@lancaironline.net Message #54783
From: Ernest Christley <echristley@att.net>
Subject: Re: [FlyRotary] Re: Timing Question for Tracy
Date: Sat, 30 Apr 2011 10:58:22 -0400
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Lehanover@aol.com wrote:
On the other hand, the actual clock position of the pickup is not important, so long as the timing wheel relationship with the pickup is maintained. So you can mount the pickup in any location that is handy, and remount the trigger wheel to agree with the pickup location.  You do this without moving the crank, and everything remains same/same.
 

I had to do something in order to add a second VR and second ignition controller. You're telling the computer where the crank is and it decides when to send a spark.  It doesn't know where that spark is going, it just sends it when it thinks it is time.

So my goal was to have backup ignition.  The problem is that you can't have two VR sensors in the same place, and going to one and some sort of splitter circuitry introduces a single point of failure.

My solution was to place the backup VR sensor 185* on the other side of the trigger wheel.  Since the 2nd rotor fires 180 degrees off from the first, all I have to do is switch the plug wires between the rotors, and I have ignition events from independent sources that are placed 5 degrees apart.  The first is controlled by the ECU to modify the advance. The second runs off a separate power source.

It is all a game of knowing where the crank is and sending the spark at the right time.
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