Dynamic Prop Balancing O340

[Dan L]

So it looks like the FX3 doesn't use a plenum. I'm wondering why when it seemed to work so well on the O-340's?

[N867SP]

I finally got around to wrapping up my dynamic balance a few months back. Ended up facing up a bracket that connected to the forward engine case split bolt, allowing the accelerometer to be vertical, centered over the crank and as close to the prop/flywheel as possible. As for the optical sensor I just taped it to the top of the oil cooler, gave it a clear shot to the reflective tape on the back of the master blade. First averaged reading was 0.26ips @ 096 degrees, multiple attempts I was able to get it down to 0.01ips @24 degrees. By temporarily adding washers to the spinner screws to find where the weight was needed. Ended up adding a single AN4-4 bolt, AN960-4L washer and a AN365-428 nut to one of the existing holes in the flywheel that was the closest to the degree needed. Typically anything less that 0.07ips is “acceptable” anything below 0.04ips is “good”. Noticed slight reduction in vibration in the aircraft in our 16hr roundtrip to OSH18.

Forward accelerometer mount




Aft optical mount


First averaged reading


Final averaged reading with permanent hardware installed



Pete Meyer
Severna Park, MD
CCK-1865-0078
✈️N9PW

[Dbro172]

Shouldnt the accelerometer be straight up and down, vertically?


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[N867SP]

Shouldnt the accelerometer be straight up and down, vertically?


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Perpendicular to crankshaft, so with tailwheel Aircraft it’s not vertical to ground.


Pete Meyer
Severna Park, MD
CCK-1865-0078
✈️N9PW