Dear All,
I need some help in understanding the information I have gathered on the
diagnostics
of my propeller.
I used the Smart Avionics PB-3, the configuration for the setup is illustrated
in the diagram. The PB-3 was mounted on the port side of the manifold and the
pick up reflective strip was mounted on blade 3. The red block shows the PB-3
vibration sensor and the blue line highlights the x-axis orientation.
Forgive the handwriting, I did it with a mouse :)
Ignore the axis in grey. I have used an illustration from the Rotax Installation
manual to give context to my diagram, and are not used for my purposes.
Point 1 is my starting reference.
Point 2 had 1 washer (ca. 4g.) removed from blade 3.
Point 3 had the washer returned to blade 3, and 1 washer from blade 2 to blade
1.
Point 4 had a washer from blade 1 moved to blade 3
Point 5 had 2 washers removed and moved 1 to blade 1 and 1 to blade 2.
In total blade 2 ended up 3 washer down on the start, blade 3 ended up 2 washers
up on the start and blade 1 ended up 1 washer up on the start.
As far as I understand the PB-3 0 is the alignment in the X-axis, when is X-axis
mode on the PB-3 app. Plus it registers the out of balance when the force pulls
it in the X-direction. Therefore the propeller has to rotate between the 225
and the 284 for the out of balance to be register (Very simplistically
speaking).
>From my first diagram, and given 120 between blades, then blade 2 sits at 240
or basically where I understand the imbalance to be if I have interpreted my
data
correctly.
With so much weight removed from the blade 2 I would have expected the imbalance
to move inwards, but instead it remains in more or less the same spot. Leading
me to conclude that a bigger effect than a mass imbalance is at play.
Blade 2 is also the one that I previously mentioned, in another post as having
more play than the other blades.
I know the Arplast PV50 has play in the blades when it is at rest. This time I
attempted to measure the at rest play. Blades 1 and 3 are fairly consistent with
each other and approximately 1 of play. Blade 2 has approximately 4.
I think what I am looking for, and the reason for this post, is for someone else
to think about my workings to sanity check if I have missed anything; or also
to check the conclusion is genuine and I am not just looking for evidence of
blade 2 because that is my apparent problem.
Thanks all
Jon
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