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From: Craig Schulze <craig@skybolt.net>
Subject: Re: Potential Problem-Engine Vibration

It sounds to me that you may have an issue with your prop hub not changing t=
he pitch exactly the  same on all the blades.  The vibration you are feeling=
 is one blade taking a larger bite of air and then causing everything to wob=
ble.  It settles in sometimes but when you change the power setting the pitc=
h on the prop is adjusted by the hub unevenly. =20

Blue Skies,
Craig Schulze
Lancair N73S


On Jul 25, 2013, at 1:22 PM, "Steve Colwell" <mcmess1919@yahoo.com> wrote:

In the first 40 hours I had vibration so severe it caused stick shake.  This=

has continued intermittently more or less for almost 400 hours.

First I found and fixed several Cowl Interference locations, then adjusted
and notched the hat section of the nose gear door.

At about 50 hours I paid Barrett to tear down the engine to replace the
Performance pistons (prematurely worn top rings) with stock ECI pistons.
Also found a cracked case.

We had the Kelly Alternator balanced and rebuilt at a shop recommended by
Bill Bainbridge of B & C.  Sorry I can't remember the name, the Legacy file
is in Texas.=20

I rounded the leading edges of the elevator counter weights when building so=

I temporarily squared them off to go back to the stock shape for testing.

All gear doors were checked in flight with video camera.=20

The pitch trim hinge pin had play, I replaced it per Chris Zavatson's web
page.

Along the way the prop was balanced twice.

I could not get more that the usual vibration (which always seemed to be too=

much) on test flights.  Then, unpredictably, vibration magnitude would
increase with power reduction on some later flight.  I say unpredictably
because I could not get increased vibration by attempting to duplicate
previous conditions.  Let's hope a solution surfaces at Airventure.

Steve Colwell  Legacy RG IO550-N with Hartzell 3 Blade


-----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Paul
Miller
Sent: Thursday, July 25, 2013 7:22 AM
To: lml@lancaironline.net
Subject: [LML] Re: Potential Problem-Engine Vibration

Ed Martin's legacy is smooth.  Mine has had a lot of annoying vibes as you
describe but virtually all have been removed with lots of cowling
interference fixes and plug change.  Many pilots forget the alternator can
be a wicked source of vibration and it is almost in the same plane as the
prop.

The problems I had originally were in that freq range and visible at the
wingtip also.

Paul