Prop Balance and Murphy

WIth 4 hours on the fresh top overhaul I decided it was time to
balance the prop as we removed the weights when sending the props out
for new studs...

I was delayed a bit at my monthly meeting down in Grand Blanc and got
back to the airport at a quarter to one... The Kid was chomping at the
bit... He immediately dove into pulling the top cowel and the top
plate of the air pressure box around the engine... He bolted the
accelerometer to the engine, taped the strobe to the side of the lower
cowl, and cleaned the back of the prop with butyrate thinner and put
reflective tape on it...
(I love the smell of bannana oil - it always makes me remember my dad
as one of my earliest memories is following him around a yellow J3 Cub
as he was patching the fabric)
We pushed back out onto the ramp and did the engine run... It was 24
IPS at 2400 RPM - not good... The engine definitely was putting
vibration into the airframe... Even more noticeable with the cowel off
when you can see the cylinders vibrating...
He then pulled a spinner screw and hung an external weight on the
spinner in the amount that the balancer machine calculated and we re-
ran the engine... Oops, we were 180 degrees off on placement (Murphy
hanging around)... Quickly reversed that and ran it again... Balance
was about 0.9 IPS - mucho better...

OK, now we are in the ball park... The Kid changed over to internal
weights.. He had to calculate the new weight based on the fact that
they were closer to the crank centerline than when external, and plus
the additional weight that the computer called for the 0.9IPS of
unbalance... After mounting the internal weight we put the spinner
back on, and did all the safety wire and screws, etc... Took it out
and ran it... About 0.7 IPS, acceptable but nothing to write home
about...

We pulled back in and discussed it... Decided to go to split
weights... Took the spinner off again, which is not a trivial job
recalculated the weights for the split condition, rehung them, put it
all back together (it is 33 degrees and blowing and even with the
plane part way in the shop, I am by now shivering)... Pushed back,
engine run. 0.6 IPS @ 2400, but we both can tell it is smoother with
the split weights at idle than it was with a single weight... Asked
the computer for the new (and hopefully final) weight...

Once more into the breach we, the light Brigade, go...Take it apart,
add one thin little weight, put it together, push it back, run it...
Holy shakes, Batman - 0.2 IPS!
HIgh fives all around... Two hours of freezing our butts off and
wearing the tips off our fingers with lebenty seben screws...

ME: Uhh, why is there a film of oil on the back side of the accessory
case?"
The Kid: "Well, I was hoping you wouldn't notice that."
ME: "In your dreams, Tonto."
We are both peering at the offending specks of oil (just a dusting
really)
Looks like the gasket for the oil filter adapter...
The Kid sighs, "Well, lets push it in the shop and I'll change the
gasket tomorrow. I've got another job I promised to do today."
Ah jeez, I wanted to go flying... Does that Murphy guy ever take a day
off?

denny