I did not try the procedure described by Finn where a weight was attached at the four cardinal locations.

I used a Freescale MMA7260Q eval board as the 3 axis accelerometer, a USB 6009 as an A to D unit and Signalexpress software both from National Instruments, and a laptop computer to collect and process the data.

The photo shows the setup for balancing the prop.  The position reference Hall effect sensor was installed on the red mount and clamped to redrive.  The sensor and mount were covered in modeling clay to dampen resonance vibrations possible in this mount.  The Hall effect trigger was attached to the prop flange with double sided tape along with an equal weight attached in the same way 180 degrees from the trigger.  The accelerometer is seen behind the red clamp and was installed in a 1/4” aluminum plate.  This was screwed to a second 1/4” aluminum plate which was bonded to the redrive with epoxy putty.  Before the engine was started, a  “thump test” was performed by striking the accelerometer lightly with a rubber hammer and recording the results in order to verify the stiffness of the accelerometer mount.  The balance was adjusted by adding washers under the screws which attach the spinner to the aft bulkhead and at the angular location indicated by the processed data.  The final balancing weight was in the form of washers, nut, and bolt installed in the aft spinner bulkhead.  This weight took into account the difference in the radius from the center of the prop shaft to the test washers under the spinner screws compared to the radius to the location of the balancing bolt, nut, and washers.

The engine was balanced by locating the Hall effect position sensor where it would see a trigger attached to one of the damper plate to flex plate bolts with an equal weight attached to the opposite bolt.  Washers of various weights were installed under two of the bolts until the unbalance phase angle was aligned with one of the four bolts.  Then the weight under that bolt was adjusted until the balance was acceptable.

Steve Boese