"Dave Hyde" wrote in message
...
I've had a kind of unnerving vibration in my RV-4 since first
flight. I looked into harmonic dampers, but they're pretty
expensive, so I decided to give dynamic balancing a shot first.
$200 and 1 hour later, my engine runs *much* smoother. It
measured 0.3+ ips on the first run, so the guy weighed and
added an AN-4 bolt, nut, and a few washers to the flywheel.
Next run it was down to 0.05 ips and felt markedly different,
much smoother and quieter. I ran out of time and weather at
the same time, so I haven't flown it yet, but I don't see how
it can't help but be smoother. It remains to be seen whether
or not I'll have the pronounced shake at some power settings
and speeds, but I've also cut back the baffles where metal
rubbed on fiberglass and tightened things under the cowl a bit.
We'll see.

I've had dynamic propeller balancing done on every airplane I've owned.
It's absolutely the best dollars I've ever spent on maintenance. It can
make 4-cylinder engines feel like 6-cylinder.

I feel strongly the money spent is quickly recovered on the things that
don't break because of vibration. Just do it, you'll never regret it.

Bill Daniels