X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from elasmtp-junco.atl.sa.earthlink.net ([209.86.89.63] verified) by logan.com (CommuniGate Pro SMTP 6.0.5) with ESMTP id 6403776 for lml@lancaironline.net; Mon, 05 Aug 2013 08:44:37 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.63; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=nmUuqokItx3U4yvxGd4I6jXonkxvRwDw3jg/CSW2aI9c259vtSIvILBcrw4OzMre; h=Received:From:Mime-Version:Content-Type:Subject:Date:In-Reply-To:To:References:Message-Id:X-Mailer:X-ELNK-Trace:X-Originating-IP; Received: from [72.92.134.55] (helo=[192.168.1.24]) by elasmtp-junco.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1V6K8n-0000nc-LH for lml@lancaironline.net; Mon, 05 Aug 2013 08:44:02 -0400 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1085) Content-Type: multipart/alternative; boundary=Apple-Mail-126-114965047 Subject: Re: [LML] Potential Problem-Engine Vibration Date: Mon, 5 Aug 2013 08:43:59 -0400 In-Reply-To: To: "Lancair Mailing List" References: Message-Id: X-Mailer: Apple Mail (2.1085) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da940c6f371768d8f5285111c46eaf809829d350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 72.92.134.55 --Apple-Mail-126-114965047 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 Steve, thanks for this post. Can you elaborate on the prop alignment relative to #6 TDC? Does that = mean you want one prop blade vertical when #6 is at TDC? ....and why = would that matter? thanks, Colyn On Aug 4, 2013, at 5:38 PM, Steve Colwell wrote: =20 Oshkosh/Vibration, or what I learned on my summer vacation: =20 First, all 550 Continental crankshaft separations and cracks have been = traced to prop strikes or likely prop strikes. We are back on flight = status with 15SC. =20 =20 Les Doud (Applications Engineer) of Hartzell, spoke at Jeff Edwards = Forum and spent 30+ minutes with me later discussing our Vibrations. = The most interesting point was the weight of a metal 3 blade prop causes = it to act as a gyroscope. The engine and all moving parts can create a = harmonic more easily as a result. Lighter weight composite props have = much less gyro effect and therefore are inherently smoother. Our stiff = composite airframes are more susceptible than an aluminum one with = =93every rivet acting as a damper=94. I previously thought the main = reason was composite blades had less resonance than metal. =20 After all the obvious sources have been checked and fixed, the best = diagnosis tool is a in flight Spectrum Analysis and Plot with the top of = the line DynaVibe (tool cost $3000+). At least that is what the = DynaVibe rep. said in a forum and Les agreed. Mount the sensor tightly = on something solid like a spar cap, horizontal and parallel to the spar = (not on anything like the panel dust cover). Determining increased = first, second or third order vibrations narrows down the source. Les = thought in my case of unpredictable vibration, the free iPhone ap = =93Vibration=94 could be accurate enough to find the major shake.=20 =20 Les advised checking prop orientation for parallel alignment of one of = the blades with #6 cylinder at Top Dead Center on compression. This is = best for smoothness. =20 Paul Snyder, an Engineer with Lord Mounts, thinks he may be able to = help. He cited the Mooney Ovation with a vibration problem that was = improved by a single stiffer mount on the left front. Early Cirrus with = 550=92s and 3 blade Hartzell=92s vibrated, later versions have 6 mounts = with 4 near the front to better balance the static weight of the prop = and engine. He may have suggestions when he knows the part number of = the brown (silicone) mounts supplied to me by Lancair. =20 Oshkosh is a excellent resource for all things aviation. You can button = hole the engineer/designer/owner and get a lot closer to answers. I was = impressed with their willingness to help us and the lack of = defensiveness on their part. =20 =20 Oh yeah, the weather, just about perfect, in the 70=92s most of the = time. The LOBO/Lancair Banquet was great with a full house, Alberto=92s = Mars Curiosity talk was amazing and the new location at Best Western = Waterfront Hotel is a big improvement in banquet room and food/service = quality. You shoudda been there! =20 Steve Colwell aka =93Claudette=92s husband=94 =20 --Apple-Mail-126-114965047 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252 Steve,   thanks for this = post.

Can you elaborate on the prop alignment = relative to #6 TDC?  Does that mean you want one prop blade = vertical when #6 is at TDC?    ....and why would that = matter?

thanks,

Colyn

On Aug 4, 2013, at 5:38 PM, Steve Colwell = wrote:

Oshkosh/Vibration, or what I learned on my summer = vacation:
 
First, all 550 Continental = crankshaft separations and cracks have been traced to prop strikes or = likely prop strikes.  We are back on flight status with 15SC. =   
 
Les Doud (Applications Engineer) = of Hartzell, spoke at Jeff Edwards Forum and spent 30+ minutes with me = later discussing our Vibrations.  The most interesting point was = the weight of a metal 3 blade prop causes it to act as a = gyroscope.  The engine and all moving parts can create a harmonic = more easily as a result.  Lighter weight composite props have much = less gyro effect and therefore are inherently smoother.  Our stiff = composite airframes are more susceptible than an aluminum one with = =93every rivet acting as a damper=94.  I previously thought the = main reason was composite blades had less resonance than = metal.
 
After all the obvious sources = have been checked and fixed, the best diagnosis tool is a in flight = Spectrum Analysis and Plot with the top of the line DynaVibe (tool cost = $3000+).  At least that is what the DynaVibe rep. said in a forum = and Les agreed.  Mount the sensor tightly on something solid like a = spar cap, horizontal and parallel to the spar (not on anything like the = panel dust cover).  Determining increased first, second or third = order vibrations narrows down the source.  Les thought in my case = of unpredictable vibration, the free iPhone ap =93Vibration=94 could be = accurate enough to find the major = shake. 
 
Les advised checking prop = orientation for parallel alignment of one of the blades with #6 cylinder = at Top Dead Center on compression.  This is best for = smoothness.
 
Paul Snyder, an Engineer with = Lord Mounts, thinks he may be able to help.  He cited the Mooney = Ovation with a vibration problem that was improved by a single stiffer = mount on the left front.  Early Cirrus with 550=92s and 3 blade = Hartzell=92s vibrated, later versions have 6 mounts with 4 near the = front to better balance the static weight of the prop and engine. =  He may have suggestions when he knows the part number of the brown = (silicone) mounts supplied to me by = Lancair.
 
Oshkosh is a excellent resource = for all things aviation.  You can button hole the = engineer/designer/owner and get a lot closer to answers.  I was = impressed with their willingness to help us and the lack of = defensiveness on their part.  
Oh yeah, the weather, just about perfect, in the = 70=92s most of the time.  The LOBO/Lancair Banquet was great with a = full house, Alberto=92s Mars Curiosity talk was amazing and the new = location at Best Western Waterfront Hotel is a big improvement in = banquet room and food/service quality.  You shoudda been = there!
 
Steve Colwell  aka = =93Claudette=92s husband=94