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  #1  
Old 12-23-2013, 02:14 PM
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777Dave 777Dave is offline
 
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Default Engine start...

I have an airplane equiped with 2 bendix mags and "shower of sparks" system. I also have no key switch but instead have a 4 position switch allowing me to select off, left, right and both (mags). To engage the starter I have a simple toggle switch.
Just confirming that I should be using "left" selector for start to avoid kickback.
Cheers and thanks
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  #2  
Old 12-23-2013, 02:32 PM
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Do you have an impulse coupling on the left mag??
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  #3  
Old 12-23-2013, 03:01 PM
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Shower of Sparks mags don't have impulse couplings.

Both should be on when starting if both have the system installed. Otherwise you only want to be starting on the mag with the shower of sparks.
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  #4  
Old 12-23-2013, 03:39 PM
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N941WR N941WR is offline
 
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I question the toggle switch for the starter. Shouldn't you use a push button?
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  #5  
Old 12-23-2013, 05:10 PM
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Default clarify

Correct, no impulse coupling.
Its a spring loaded toggle so same as push button. Interesting because its well hidden and almost impossible to see.(thief) I have read a couple of older threads that talk about this setup so I think the builder (not me) decided to do it this way.
As I mentioned, I'm just confirming that left mag start is preferable.
Bob, SoS is only on the left...
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Last edited by 777Dave : 12-23-2013 at 05:12 PM. Reason: additional info
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  #6  
Old 12-23-2013, 05:16 PM
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As I understand things, left mag only for starting is to let the impulse coupling do its job and only have a retarded spark.

Usually an impulse coupling is on one mag, and the other mag will fire at static timing----------so it is bypassed for start.

While Rocket Bob is correct that a shower of sparks setup is not intended for use with an impulse mag----------you never know if someone has batched up a bunch of mismatched parts, and thus my original question.

I see no reason to start on left only in your case---------as at cranking speeds the right mag is not doing much of anything in the spark department, unless it also has a SOS or impulse coupling-----just not enough electrical energy developed in the mag at cranking speed. It will not hurt to start left only if it is the only mag with the shower of sparks setup.

http://www.aeroelectric.com/articles...erOfSparks.pdf
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Last edited by Mike S : 12-23-2013 at 06:33 PM.
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  #7  
Old 12-23-2013, 05:47 PM
BobTurner BobTurner is offline
 
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Mike,
You may be confusing an impulse coupling - which is a spring loaded affair that both increases the magnet speed and hence the voltage, and retards the timing to near TDC - with a retard breaker, which retards the timing. You want a retard breaker mag (at least with Slicks, I'm not familiar with Bendix) to trigger the shower of sparks (called Slick start with Slicks).
I would turn any non retarded mag off during start. While true, usually they won't fire at cranking speed, it might (say, a plug gap was extra small) and this could result in a kick back and damage.
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  #8  
Old 12-23-2013, 06:34 PM
Kyle Boatright Kyle Boatright is offline
 
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Quote:
Originally Posted by N941WR View Post
I question the toggle switch for the starter. Shouldn't you use a push button?
Perhaps he has a momentary (spring loaded) toggle. That's what I have.
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  #9  
Old 12-23-2013, 06:39 PM
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Quote:
Originally Posted by BobTurner View Post
Mike,
You may be confusing an impulse coupling - which is a spring loaded affair that both increases the magnet speed and hence the voltage, and retards the timing to near TDC - with a retard breaker, which retards the timing.
Nope, no confusion there.

The OP was not the builder of this plane, and did not initially state if the SOS was only on the left mag--------thus I was asking questions to determine what his setup was, if in fact he even knew for sure how it was setup.

When someone is asking about a plane they did not build, it is good to get all the details straight..............what actually is, may not be how we would have done it, and best to not fall into that thinking process.
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VAF 909

Rv-10, N210LM.

Flying as of 12/4/2010

Phase 1 done, 2/4/2011

Sold after 240+ wonderful hours of flight.

"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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  #10  
Old 12-23-2013, 06:39 PM
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N941WR N941WR is offline
 
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Quote:
Originally Posted by Kyle Boatright View Post
Perhaps he has a momentary (spring loaded) toggle. That's what I have.
Yep, see his reply above.

Quote:
Originally Posted by 777Dave View Post
...
Its a spring loaded toggle so same as push button...
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