spin balancing a tail rotor

Don W wrote:
Seems like you are describing a method for balancing a 3-blade system
since it requires placing weights at 120, 240, and 360 degrees
successively but at the same radius.

There should be a similar method for a two-blade system which involves
placing the weights at different radii and plotting the vibration using
the dial indicator.

Or am I missing something??

You can probably add the weights at whatever angle is most convenient
(if the rotor hub has a balance wheel with three holes evenly spaced at
120 degrees, or four at 90 degrees...) and then plot the circles
accordingly. My understanding is the solution will give you how much
weight to add and where (in degrees from your reference) to add it, and
that you add the solution weight at the same radius you added the test
weight (probably a washer or washers).

I gather the number of blades is irrelevant to this method. Besides,
adding and subtracting weights to two opposing blades only affects
spanwise balance (not chordwise, which is usually much smaller anyway).