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EFII and propeller balancing

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jask

Well Known Member
Just discovered the other day that EFII uses the top dead center hole on a lycoming flywheel to mount the magnet for the hall sensor. Those holes every 30 degrees are the extremely easy place to add weight for prop balancing on a lycoming which forces anyone balancing their prop to then drill holes in the spinner backplate. Propeller balancing is probably one of the cheapest and most valuable things you can do for an aircraft to prevent fatigue damage. IMO, anyone adding the EFII should remove the flywheel and drill a 3/16 partial depth hole to mount the magnet on a different radius so that the pre-drilled flywheel holes can continue to be used for balancing. EFII just uses a dab of epoxy to glue their small magnet in the 1/4 inch hole.
 
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If the balance required a weight to be put at TDC, two smaller equal weights can be placed on either side of TDC to achieve the same results.
 
balance weigts

It is not a matter of splitting the weights. The bolts used for balancing would hit the hall sensor as the flywheel spins. The magnet and hall sensor must be placed at a shorter radius to clear the bolts.
 
Prop balancing

I recently discovered the problem with the EFII hall sensor when I began balancing a lycoming with a Cato fixed pitch prop. At this point, the only choice was to drill holes in the spinner for the weights. Balance weights were actually required almost opposite of TDC. The weight of the small magnet actually added to the unbalance problem. Luckily, with a fixed pitch prop, the system was not very much out of balance with a reading of .11 IPS so we elected to let it be as is. If that had been a CS prop, the reading would have been at least a .3 or above. BTW, less than 1 oz at 5 inches will balance a prop with a .35 IPS. That would be equal to .5 oz at 10 inches from center so it does not take much weight to cause a significant out of balance.
 
EFII magnets

Not sure whose magnets you are looking at, but they are not ours.
Our magnets get buried in the ID of the alternator belt feature of the flywheel. And there is no magnet at TDC. They are epoxied in and oven cured.
There is no effect on prop balance.

Robert Paisley
 
Prop balancng

I called EFII and that was their magnet that was installed for testing but never removed.
 
Prop balance on flywheel

EFII is Robert and I called him. He said the installed magnet was indeed his so his post was in error. It was installed for testing and not removed. He does not normally use the balance holes for his system.
 
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