Naming Your Mags

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Tiger Tim

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Here’s a dumb question for y’all: if you were taking an in-line engine and flipping it over how would you identify which mag is which when wiring the P-leads? Would you go with the left one being physically on the left side of the plane or would you reference them the same as they would have originally been before overturning the whole assembly?

I guess the same question would apply to turning an engine from a tractor to a pusher, like if you took a C85 off a Super Cub and put it on a Breezy.
 

pwood66889

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Supprised "Fran and George" has not been taken... :)
Realistically, when reinstalling, one should just pick something mnemonic from the pilot's seat. And document the socks out of it!! So the next proud caretaker does not muff it.
 

TFF

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One is Awww. The other is Sxxx.

I work on Lycoming powered helicopters that have the engine drive facing rearward. Left engine mag is on the right side of the airframe.
 

TiPi

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This is a problem in a number of industries. Engines are generally numbered by the manufacturer of the engine and referenced by the flywheel end. The installation can be in a number of ways (flywheel forward, sideways, facing back, up/down). In most cases, the cylinder numbering and mag/injection pump label are kept as per engine manufacturer so that they align with repair and parts manuals.
 

Chilton

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Disclaimer:- this only applies to DH Gipsy engines mounted in a tractor configuration!

De Havilland used the terms Port and Starboard, thus being aircraft side referenced. I have no idea what was done for the few pusher installations as I dont have manuals for any of those!
 

wsimpso1

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The convention in cars and trucks is to just call it like you do when conventionally applied. Even if it was facing backwards or sideways in the vehicle. The end with the bellhousing has Rear Face of Block, the other end has Front End Accessory Drive, etc.
 

Bill-Higdon

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The convention in cars and trucks is to just call it like you do when conventionally applied. Even if it was facing backwards or sideways in the vehicle. The end with the bellhousing has Rear Face of Block, the other end has Front End Accessory Drive, etc.
Really applying logic to this discussion, that spoils the fun
 

Hephaestus

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Put a coat of paint on them, Make one pink and one blue. Then just ignore physical location :)
 

Tiger Tim

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Thanks for the answers so far, both the serious kind and the ones good for a laugh.

The more I think about it the more it’s baking my noodle. In short the situation is that the controls are two toggle switches side by side (so clearly a left and a right) and labelled as such. After a day of thought instead of finding some clarity I actually conjured up a third option. Here’s what I’ve got:

1. Go with Left and Right as they would be identified on the engine as originally intended. This would keep part numbers straight since IIRC the mags rotate in opposite directions and there’s a single impulse coupling. This would keep procedures (both operational and future parts replacement) simple but at the cost of potentially replacing parts on the wrong side if I forget that they’re backwards.

2. Go with Left and Right with reference to the airframe. If there was fouling found on a run up it would be easy to ID which set of plugs to pull for cleaning/replacement as well as generally being easier to physically point to a problem. If I ever need parts for the mag on the left side, I’ll have to remember that it’s actually a right mag.

3. Go with Left and Right as originally ID’ed on the engine but make up a set of extra long ignition harnesses that cross over behind the engine. This way the switches still directly describe which set of plugs are firing. I don’t know if losses through essentially double length leads would be an issue. Also, it would convince the next guy to wrench on it that I was nuts. Still, I kind of like this option even though it means I’m re-re-wiring the plug leads to do it.

What do you all think? Are there any obvious pros and cons to the above? Potential deal breakers for anything?
 

Deuelly

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Change the switch nomenclature to Ignition 1 and Ignition 2. Paint 1 and 2 on the corresponding mag or ignition source. Fast, accurate, effective, eliminates all confusion now and in the future.
Until a maintenance manual says "Connect right magneto to lower plugs".
;)

Brandon
 

Tiger Tim

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Which engine and airframe combination is this for? I thought you were working on a Gipsy Moth so that is an upright engine anyway??
It’s for the Gipsy Moth but the engine used is a converted Gipsy Major standing in as a sort of hot rod Gipsy III. I came late to the party and the two men who really planned out this whole project have both passed away. In any case it’s a neat rig with a custom cast oil pan, pressure lube to the rockers, and a bunch of other clever little mods beyond just turning the engine over.
 

Chilton

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The only one of those I know of the builder treated it as a Gipsy III, if I remember right the impulse magneto is on the left side on the upright engine and becomes the right on the inverted, but the switches on the deck are wired to have the impulse mag on the front toggle which ever way up the engine is!

I assume you have the manuals for both upright and inverted Gipsy?
 

hangarrat101

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I know the Tiger Moth is set up with the front switch controlling the impulse mag. That's the starboard mag on a Gipsy Major. As for which is left and which is right, I'd go with whatever the engine manual says should be left or right.
 
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