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Z-13/8 RE: P/E-Mags Bus Feed

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rv7a(at)cox.net
Guest

Posted: Sun Feb 03, 2008 2:05 pm Post subject: Z-13/8 RE: P/E-Mags Bus Feed

Looking carefully at the drawing the inset in the lower   right side shows the P-Mag fed from the "Main Bus" and the E-Mag fed through the  S700-2-10 switch from the "Battery Bus".  Then if you look at the upper  left hand part of the drawing at the "Main Battery Bus" you see both the right  and left ignitions coming off this bus.  I think my question is this...Is  the "Battery Bus" and the "Main Bus" nomenclature in the lower right inset  really the "Main Battery Bus" and not the Battery Bus and the Main Power  Distribution Bus?  Probably a dumb question for anyone than has done more  electrical work than changing a light bulb.  Do not archive.

  

 Jim Thorne

 RV7A CHD

   [quote][b]

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n8zg(at)bellsouth.net
Guest

Posted: Sun Feb 03, 2008 3:15 pm Post subject: Z-13/8 RE: P/E-Mags Bus Feed

Jim - 

  

 The Battery Bus and the Main Bus are indeed two separate  circuits.  The EMag is an electrically dependent ignition - lose or remove  electrical power and it quits sparking.  Conversely, PMag is NOT  electrically dependent - once above about 900 RPM, it makes it's own  power via a small internal alternator.  

  

 Bob's philosophy has been to connect electrically dependent  ignitions directly to the Battery Bus, so that in the event of smoke or other  electrical misbehavior, one can throw the Master OFF and not lose the  engine.  Hanging the EMag off the Battery Bus ensures that it will continue  to make sparks with the Master OFF.  

  

 Neal  George

 RV-7  N8ZG

 Canopy  & Cowling



   From:  owner-aeroelectric-list-server(at)matronics.com  [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Jim  Thorne

Sent: Sunday, February 03, 2008 3:59 PM

To:  aeroelectric-list(at)matronics.com

Subject: Z-13/8 RE:  P/E-Mags Bus Feed

 

 Looking carefully at the drawing the inset in the lower   right side shows the P-Mag fed from the "Main Bus" and the E-Mag fed through the  S700-2-10 switch from the "Battery Bus".  Then if you look at the upper  left hand part of the drawing at the "Main Battery Bus" you see both the right  and left ignitions coming off this bus.  I think my question is this...Is  the "Battery Bus" and the "Main Bus" nomenclature in the lower right inset  really the "Main Battery Bus" and not the Battery Bus and the Main Power  Distribution Bus?  Probably a dumb question for anyone than has done more  electrical work than changing a light bulb.  Do not archive.

  

 Jim Thorne

 RV7A CHD

[quote] [b]

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nuckolls.bob(at)cox.net
Guest

Posted: Mon Feb 04, 2008 6:10 am Post subject: Z-13/8 RE: P/E-Mags Bus Feed

At 02:59 PM 2/3/2008 -0700, you wrote:



 	  Quote: 	
		  Looking carefully at the drawing the inset in the lower  right side shows 

the P-Mag fed from the "Main Bus" and the E-Mag fed through the S700-2-10 

switch from the "Battery Bus".  Then if you look at the upper left hand 

part of the drawing at the "Main Battery Bus" you see both the right and 

left ignitions coming off this bus.  I think my question is this...Is the 

"Battery Bus" and the "Main Bus" nomenclature in the lower right inset 

really the "Main Battery Bus" and not the Battery Bus and the Main Power 

Distribution Bus?


	




   The distribution suggestions you've cited are

   artifacts left over from the Pre-Emag era where

   individuals with electrically dependant engines

   are encourage to run all engine feeds from the

   battery buss. This would include up to 2 two

   electronic ignitions including E-mags.



   In the new era of best-we-know-to-do for

   aircraft ignitions, the earlier architecture

   still holds for two E-mags. However, the

   special nature of the P-mag's internal power

   supply combined with the owner/operator's

   desire to occasionally test a P-mag for

   full functionality, running the P-mags

   (whether one or two devices) from the main

   bus keeps the switching simple while allowing

   for the occasional testing of the P-Mag's

   alternator.



   So the short answer to your question is, it

   depends. If you have any combination of ignition

   system products that depend on the ship's

   electrical system, run them from the battery

   bus. If you have one or two P-mags, run them

   from the main bus.



   Bob . . .

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hotwheels

Joined: 01 Jun 2007
Posts: 240

Posted: Mon Feb 04, 2008 7:28 am Post subject: Re: Z-13/8 RE: P/E-Mags Bus Feed

Devices hanging off the battery bus (like EMags or electronic ignition) don't have any way to be shut down when the master is switched off. Each of the above must therefore have it's own switch to de-energize that circuit, right?



Jay

do not archive

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nuckolls.bob(at)cox.net
Guest

Posted: Mon Feb 04, 2008 8:55 am Post subject: Z-13/8 RE: P/E-Mags Bus Feed

At 07:28 AM 2/4/2008 -0800, you wrote:



 	  Quote: 	
		  



Devices hanging off the battery bus (like EMags or electronic ignition) 

don't have any way to be shut down when the master is switched off. Each 

of the above must therefore have it's own switch to de-energize that 

circuit, right?


	


   Seems like the way to go. If you were flying a J-3

   with NO electrical system, you'd still have a couple

   of switches that control the magnetos. Further,

   operation of those switches would be addressed in

   your pre-fight/post-flight protocols.



   The supporting simple-idea is that one selects

   the accessories that are needed to meet

   design/mission goals for the aircraft. Then

   figure out ways to minimize weight, parts

   count, pilot workload, costs of ownership,

   and still have an acceptable failure mode

   effects analysis (favorable = failure tolerant).



   The collection of switches, the things they

   control, the manner in which they are operated

   and the sources for power are all ingredients

   that go into the recipe for success. Further,

   there are MANY recipes for success that select

   from a HUGE array of ingredients.



   Bob . . .

        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

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