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  #161  
Old 02-02-2017, 05:03 AM
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Toobuilder Toobuilder is offline
 
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Quote:
Originally Posted by rwtalbot View Post
Dan,

I don't disagree there are some considerations with the rear pickup and its engineering. However, I think you have somewhat understated the risk associated with two pickups on the crankshaft as anything that gets loose in there may well destroy both systems.

I am not overly concerned if the rear mounted system fails (and doesn't compromise the engine itself). Simultaneous failure of both pickups could result in a fatal accident.

The group may find the following accident report useful.

http://www.atsb.gov.au/media/5341498...21%20Final.pdf

It seems that we are going down the familiar rabbit hole of trying to guard against the mere possibility of failure, rather than evaluate the probability, as Dan is wisely suggesting. After all, the entire accessory gear train in a Lycoming depends on a single 5/16 bolt securing the crank gear- yet we don't give that much thought. So back to Dan's point, aside from a belt coming loose (which is easily guarded against), or bad design/maintenance (as the Glassair accident suggests), what is the probability that something can "get loose in there" (behind the ring gear) that wouldn't cause engine stoppage anyway?

I'm not saying it can't happen, and I'm not saying that I'm not blind to my own logic/justification, but I'm not seeing a higher risk with a properly designed and maintained front pickup system.
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

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  #162  
Old 02-05-2017, 03:42 PM
rwtalbot rwtalbot is offline
 
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Quote:
Originally Posted by Toobuilder View Post
After all, the entire accessory gear train in a Lycoming depends on a single 5/16 bolt securing the crank gear- yet we don't give that much thought.
To compare the reliability of a home brewed, one of a kind crankshaft position sensor installation with a component that is the subject of numerous SBs and has 60+ years and millions of hours in service doesn't really work for me.

This whole thread started with Dan building a rear mounted pickup. Presumably he had his reasons despite both of us acknowledging the additional complexity.

We all have different views on this stuff and that's fine. My personal design goal is zero probability of a single failure taking out both ignitions.
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  #163  
Old 02-05-2017, 05:25 PM
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Quote:
Originally Posted by rwtalbot View Post
My personal design goal is zero probability of a single failure taking out both ignitions.
Go for it. I can see a little higher risk per trigger, but an argument for low risk of double failure makes sense.
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  #164  
Old 02-08-2017, 07:30 AM
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Default Maybe I missed it..

Maybe I missed it in an earlier post...

Dan.. I see pics in post #4..
What High voltage power pack are you using? ie. What year/model car/truck did it come from?
Did you make your spark plug wires or did you buy some off the shelf?
What spark plugs are you using? Gap?

I know you use a IO390. Do you feel that these parts would work well for an O360 lycoming? I saw that Kirk has a 360. Are you guys running the same power pack, wires and spark plugs?

Thanks.
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  #165  
Old 02-08-2017, 08:21 AM
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Quote:
Originally Posted by N363RV View Post
Dan.. I see pics in post #4..
What High voltage power pack are you using? ie. What year/model car/truck did it come from?
Follow the link in post#4 and read the Megajolt manuals. The popular EDIS-4 module seems to be a new or used Motorcraft DY-630, Module F1CZ-12K072-A, taken from a 91 to 96 1.9L Escort or Tracer. Also Standard Motor Products LX239.

I assume "power pack" means coils? There are two Ford choices, early and late, plus dozens of others that are compatible. Zillions of sources.

Quote:
Did you make your spark plug wires or did you buy some off the shelf? What spark plugs are you using? Gap? I know you use a IO390Do you feel that these parts would work well for an O360 lycoming?
Made up plug wires. Components here: http://www.kingsborne.com/

I use long reach plugs, so they will be different. Everything else is the same.
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Last edited by DanH : 02-08-2017 at 08:29 AM.
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  #166  
Old 03-20-2017, 07:03 AM
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Update for those following along.

The wiring shown a few posts previously has one sneaky failure mode. If the path between the main contactor and the second battery should become open for some reason (broken wire, failed terminal, fusible link or diode burns open), the ignition would continue to operate normally...until the battery ran dead. It's not a critical failure; the other ignition would be unaffected. However, the "mag drop" is so small that a pilot might not notice. The only other clues might be a change in EGT and perhaps some slight roughness if LOP at the time.

It needs an voltage monitor, something to draw attention to a loss of alternator voltage on the second ignition. The EFIS already monitors the main bus, so that's covered. My GRT Sport doesn't have an available input for the monitor task, so I went looking for a suitable stand-alone device. This one fit the bill, and it was a whopping $4.59, delivered:

http://www.tomtop.com/modules-219/p-e1021.html



The digital display is for setting the upper and lower voltage limits, using the three buttons. It's a "set and forget"; the board is mounted in a sealed box under the panel. If line voltage goes over or under the limits, it closes the relay and sets off a buzzer. I installed a flashing LED under the #2 ign switch, and set the lower limit at 12.8V:



Function is dirt simple. The LED flashes when the ignition switch is moved to ON, prior to engine start, as battery voltage alone is below 12.8. That's the self test. It stops flashing when the alternator comes on line after start. If it flashes in flight, there is something wrong. The buzzer can't be heard in flight, but it's a perfect volume to warn that I've left the ignition on after shutdown, a nice bonus.
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  #167  
Old 03-20-2017, 10:30 AM
mtnclimber mtnclimber is offline
 
Join Date: Apr 2010
Location: Nathrop Colorado
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Default Thank's for that link to voltage warning board.

I've order one for the 8 and one for the 9A.

Seems like a great safety feature if using a non standard battery.

Easy to implement as adjustable over-voltage 'Crowbar' with SCR.

Roger Bloomfield
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