"Perry Mick" <pjmick@mail.viclink.com> wrote:

"""
I've tried 4 times now to use a computerized dynamic balance
  system, but it won't converge on a solution. It always worked perfectly
    

with
  

  my direct-drive fan. So it mustn't like geared engines. I'm going to
    

trial-
  

  and-error it by moving a fender washer (weight) from one prop bolt to
    

the
  

  next and see if the vibration level readout increases or decreases, and
    

try
  

  to find a minimum.
"""

I'm curious, Perry, if a fender washer might not be overkill...  last guy
    

I
  

saw had a prop dynamically balanced it took a short #6 screw to get the
    

job
  

done.  Given the size of prop bolts and their associated fender washer
    

size,
  

aren't you concerned that will be _too much_ mass?  I'd think that much
    

weight
  

fladdling around off-center out there at 2000+ rpm would make matters
    

worse,
  

not better.  Like I said, just curious (and concerned).

    

My experience with these electronic balancers is:
a) if you can't get a consistent reading, something is out of spec, a loose
engine mount, worn bearing, off-center mounted/drilled/bored prop
b) balancer out of calibration

c) Generally it takes me about 5 runs to go from an initial run down to
about 0.02 to 0.05 IPS, if it takes more runs and values continue to jump
around "the clock", something is not right, a or b.

My 5cents,

Thomas J.

  

I've used the balancer many times before with no problem on direct-drive. I think it's getting confused by harmonics or beat frequencies between the engine and redrive. For a first step it usually asks for 20-30 grams at a certain radial position, the fender washer is about right. This is on the prop bolt circle (4.75 inches?), not out at spinner diameters. It will just be moved around the six locations temporarily to see if the vibration gets worse or better.

Perry