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

It's really only a guess.  But if you think about it the only thing changing=
 with a throttle change is pitch. =20

Blue Skies,
Craig

On Jul 26, 2013, at 10:45 AM, "Danny" <danny@n107sd.com> wrote:

> On what data do you make this assessment?
>=20
> Danny
> LNC2-360 Mk-II
> Nothing is foolproof to the sufficiently talented fool.
>=20
> -----Original Message-----
> From: Craig Schulze [mailto:craig@skybolt.net]=20
> Sent: Friday, July 26, 2013 12:48 PM
> To: lml@lancaironline.net
> Subject: [LML] Re: Potential Problem-Engine Vibration
>=20
> It sounds to me that you may have an issue with your prop hub not changing=

> the 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 everythi=
ng
> to wobble.  It settles in sometimes but when you change the power setting
> the pitch on the prop is adjusted by the hub unevenly. =20
>=20
> Blue Skies,
> Craig Schulze
> Lancair N73S
>=20
>=20
> On Jul 25, 2013, at 1:22 PM, "Steve Colwell" <mcmess1919@yahoo.com> wrote:=

>=20
> In the first 40 hours I had vibration so severe it caused stick shake.  Th=
is
> has continued intermittently more or less for almost 400 hours.
>=20
> First I found and fixed several Cowl Interference locations, then adjusted=

> and notched the hat section of the nose gear door.
>=20
> 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.
>=20
> 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 fil=
e
> is in Texas.=20
>=20
> I rounded the leading edges of the elevator counter weights when building s=
o
> I temporarily squared them off to go back to the stock shape for testing.
>=20
> All gear doors were checked in flight with video camera.=20
>=20
> The pitch trim hinge pin had play, I replaced it per Chris Zavatson's web
> page.
>=20
> Along the way the prop was balanced twice.
>=20
> I could not get more that the usual vibration (which always seemed to be t=
oo
> 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.
>=20
> Steve Colwell  Legacy RG IO550-N with Hartzell 3 Blade
>=20
>=20
>=20
> -----Original Message-----
> From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Pau=
l
> Miller
> Sent: Thursday, July 25, 2013 7:22 AM
> To: lml@lancaironline.net
> Subject: [LML] Re: Potential Problem-Engine Vibration
>=20
> 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.
>=20
> The problems I had originally were in that freq range and visible at the
> wingtip also.
>=20
> Paul
>=20
>=20
>=20
> --
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l
>=20