Received-SPF: none
 receiver=logan.com; client-ip=68.230.241.28; envelope-from=dale.r@cox.net
From: Dale Rogers <dale.r@cox.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: Timing
Date: Thu, 7 Apr 2005 17:08:20 -0400
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Message-Id: <20050407210821.MAMJ22013.fed1rmmtao11.cox.net@smtp.west.cox.net>

Umm, folks? 

   A little deeper explanation is called for.  A reluctance 
circuit triggers on a *change* in the reluctance of the 
circuit.  It doesn't require the presence of magnetized 
material, only that the reluctor material be magnetically 
sensitive (ferrous).  In fact, such circuits usually operate 
at such low values, that the most important property of the 
sensor wheel is that it be homogenous, so that there is a 
clear difference between states.  

   There are two different ways of triggering via reluctance:
detection of the presence of a "finger", and detection of 
a gap in an otherwise continuous presence of the reluctor.
The circuits are different, so the reluctor has to be made 
to match the type of circuit (or vice-versa.)

   From Tracy's pic, and description, I'd say that the RX8 
circuit is of the second type.

   Because the field of the pickup is so small, the likelihood 
of interferance by another field from an alternator - 
unless it was placed within a few millimeters of the 
pickup - is really, really small.

   Look up "Hall effect".

Dale R.
COZY MkIV-R13B #1254
       (__
|----==(__)==----|
      o/  \o

 
> From: Dennis Haverlah <clouduster@austin.rr.com>
> 
> Two things to consider:  We have dual CP"U's for the engine fuel and 
> ignition but only one sensor.  Tracy, can we add another sensor at 180 
> degrees to the first sensor and have redundancy?  Also, if a permenant 
> magnet alternator is designed to attach inside the belt drive pulley I 
> suspect it would make the sensor give faulse position indications.
> 
> Dennis H.
> 
> Tracy Crook wrote:
> 
>> Bottom line is that the 4th valley (between two teeth) following the 
>> single 30 degree flat must be centered on the sensor when rotor 1 is 
>> at TDC.
>>  
>> I have attached a drawing of the wheel but note that the wheel is NOT 
>> shown at #1 TDC in it.  The text at 5 deg BTDC on wheel is accurate 
>> relative to where the sensor should be at those times.
>>  
>> Hope the pix is not too large for list mail.
>>  
>> Tracy
>>  
>>
>>     ----- Original Message -----
>>     From: George Lendich <mailto:lendich@optusnet.com.au>
>>
>>     Tracy,
>>     You mentioned the timing mounting protocol, placement etc.
>>     I sure would appreciate that advise.
>>     George ( down under)
>>     lendich@optusnet.com.au <mailto:lendich@optusnet.com.au>
>>
>>         The RX-8 sensor is magnetic reluctance.  Same type, size &
>>         shape as the 3rd gen.  In fact if you have a 3rd gen sensor,
>>         you can use it if you can mount it correctly.  The Subaru
>>         sensors will also work but they are poor quality (many
>>         failures reported) so don't go there.
>>          
>>         Advantages are:
>>         No ignition timing scatter due to gear lash, single sensor
>>         instead of two, and gets the 2nd gen crank sensor out of the
>>         way for other things (like alternators).
>>          
>>         Tracy
>>