lml@lancaironline.net Mailing List Archive

The other related variable on prop blades is "runout" or "blade tracking." Although it's as severe as with different pitch angles, ;but significant variation between blade tracking can also be a cause of vibration. Always worth checking as part of these checks. Bob -----Original Message----- From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Craig 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 feeling 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. 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. 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. 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 -- For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html