spin balancing a tail rotor

Don: It turns out that the Russians were doing this, or something like it,
for some time
The method is basically make a run and record the peak dial indicator
reading. Add a weight to an arbitrary designated zero position. Make
another run and record that dial indicator reading. Now move that weight to
a position 120 degrees around from the zero position and make sure the
weight is installed at exactly the same distance from center that it was at
the zero position. Record the dial indicator reading and move the weight to
the 240 position, again at the same radial distance from the center and
record. Assign a graphical scale to the dial indicator readings and plot
first a circle representing the reading without a weight. Next plot a
second circle centered on the first circle at the zero degree position. Now
plot the next circle similarly at the 120 position on the first circle and
again the last circle centered on the 240 position. You should have an
intersection of all of the circles at one point. The distance from the
center of the first circle to this point represents that amount of weight
needed to correct the imbalance. The angle to this intersection represents
the angle measured from where you added the first weight to this
intersection point and designates the location to add the weight. In actual
practice you don't always get a point at the intersection but an small area.
The center of this area is used as the intersection point. I have used this
on the tail rotor of my helicopter successfully but used and accelerometer
instead of the dial indicator. The guys article in the magazine had color
plots of his graphical calculations.
--
Stuart Fields
Experimental Helo magazine
P. O. Box 1585
Inyokern, CA 93527
(760) 377-4478 ph
(760) 408-9747 publication cell
"Don W" wrote in message
om...
Sounds neat. I'd like to hear how he did it. It seems that the dial
indicator would tell you how good the balance was, but would not be very
good at telling you which side was heavier.

Don W.

Stuart & Kathryn Fields wrote:

We recently received an article for our magazine where the author
performed a balance of his tail rotor on a bench using an electric motor
and a dial indicator instead of an electronic balancer. I was impressed
with his thinking outside the box. If there is any interest in this out
there, I will see if the author would be willing to discuss his technique
here.