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Using a key Ignition switch with a Rotax 912

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Feb 24, 2009 12:01 pm Post subject: Using a key Ignition switch with a Rotax 912

At 01:08 PM 2/24/2009, you wrote:

 	  Quote: 	
		  



I have decided to use a keyed switch for the starter contactor only, 

as a safety measure, not a security measure.



MacMaster-Carr has small and inexpensive keyed security switches 

available in a two position SPST momentary contact version that 

would seem to do the job.



http://www.mcmaster.com/#key-switches/=qsw33

Has anyone had any good or bad experiences with these?


	


   What are your concerns? As a safety switch, it never

   has to SWITCH a load, only guarantee an open or close

   circuit exists before the starter button is pushed.

   This is about the most relaxed duty you can require

   of any switch.

        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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rckol

Joined: 14 Nov 2008
Posts: 36

Posted: Tue Feb 24, 2009 6:29 pm Post subject: Re: Using a key Ignition switch with a Rotax 912

I had it in mind to use the momentary contact version of the key switch to replace the push button starter switch, so it would actually be switching the current to the starter contactor.



My concerns are whether these are quality items that would be expected to perform well in the extremes of temperatures that it will see (Wisconsin winters to desert heat).

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_________________
rck

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Feb 25, 2009 8:46 pm Post subject: Using a key Ignition switch with a Rotax 912

At 08:29 PM 2/24/2009, you wrote:

 	  Quote: 	
		  



I had it in mind to use the momentary contact version of the key 

switch to replace the push button starter switch, so it would 

actually be switching the current to the starter contactor.



My concerns are whether these are quality items that would be 

expected to perform well in the extremes of temperatures that it 

will see (Wisconsin winters to desert heat).


	


   Starter contactors are generally intermittent duty

   devices that are pretty hard on switches compared

   to other forms of heavy duty relay. But the answer

   to your question cannot be quantified. Suppose I told

   you that the momentary, non-snap action switch is has

   perhaps 1/10th the service life of a snap-action push-

   button with heavy contacts.



   Without know exactly how long EITHER switch lasts

   in that application, you can't deduce the service

   life of the other switch either. "Quality items"

   is also non-quantified. I have no way to offer you

   an opinion based on any understanding of simple-

   ideas.



   We should be striving to build failure-tolerant

   airplanes. What are the consequences of failure

   for this switch? Could you not jury-rig some temporary

   means by which you energize the contactor to get the

   engine started so you can go home?



   This is an OBAM aircraft . . . you're allowed to

   think in such terms. Our spam-can flying brethern

   risk sanction for taking off with the wrong screw

   holding the ash tray in place. Try anything you

   think will meet your design goals . . . and put

   something else in later if your first choice

   proves to be a disappointment. NO switch will

   last forever.

        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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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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