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From: Robert R Pastusek <rpastusek@htii.com>
To: Lancair Mailing List <lml@lancaironline.net>
Subject: RE: [LML] Re: Potential Problem-Engine Vibration
Thread-Topic: [LML] Re: Potential Problem-Engine Vibration
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Date: Fri, 26 Jul 2013 19:12:35 +0000
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My writing got "edited" somehow; it should have read:

The other related variable on prop blades is "runout" or "blade tracking." =
Although it's NOT as severe as that caused by different blade pitch angles,=
 significant variation between blade tracking can also be a cause of vibrat=
ion. Always worth checking as part of these checks.

This is relatively easy to do by removing the plugs so you can rotate the e=
ngine easily without moving the airplane around in the process. Place a fix=
ed work stand/stool in front of the prop and clamp a ruler or straightedge =
to it so it extends back toward the prop to just touch the leading edge, ab=
out 4" or so from the tip. Adjust the position of the straightedge as you r=
otate the prop blades past it until it just touches the closest one, then m=
easure the "gap" between each other blade and the straightedge. Ideally the=
re is no gap, but it's almost impossible to produce/maintain this standard.=
 Different prop manufacturers specify the allowable gap; anything less than=
 0.20" will likely produce little/no vibration; the amount increases with t=
he increase of tracking run-out. To make it more complex, it's almost impos=
sible to measure this at anything but fine pitch--or the pitch stop setting=
 for our variable-pitch props--in the field. Truly accurate runout measurem=
ents require the tools of a proper overhaul shop.

Bob
-----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Robe=
rt R Pastusek
Sent: Friday, July 26, 2013 1:23 PM
To: Lancair Mailing List
Subject: [LML] Re: Potential Problem-Engine Vibration

The other related variable on prop blades is "runout" or "blade tracking." =
Although it's as severe as with different pitch angles, ;but significant va=
riation between blade tracking can also be a cause of vibration. Always wor=
th checking as part of these checks.

Bob

-----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Crai=
g Schulze
Sent: Friday, July 26, 2013 12:48 PM
To: lml@lancaironline.net
Subject: [LML] Re: Potential Problem-Engine Vibration

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 feeli=
ng is one blade taking a larger bite of air and then causing everything 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

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.  Thi=
s 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 Per=
formance 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 B=
ill 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 s=
o 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 p=
age.

Along the way the prop was balanced twice.

I could not get more that the usual vibration (which always seemed to be to=
o
much) on test flights.  Then, unpredictably, vibration magnitude would incr=
ease with power reduction on some later flight.  I say unpredictably becaus=
e I could not get increased vibration by attempting to duplicate previous c=
onditions.  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 interfere=
nce fixes and plug change.  Many pilots forget the alternator can be a wick=
ed 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 wi=
ngtip also.

Paul


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