X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 25 Apr 2010 03:21:48 -0400 Message-ID: X-Original-Return-Path: Received: from raven.ravenwebhosting.com ([72.9.254.67] verified) by logan.com (CommuniGate Pro SMTP 5.3.5) with ESMTPS id 4233214 for lml@lancaironline.net; Sat, 24 Apr 2010 21:48:41 -0400 Received-SPF: none receiver=logan.com; client-ip=72.9.254.67; envelope-from=paul@tbm700.com Received: from 6.21.204.68.cfl.res.rr.com ([68.204.21.6]:58242 helo=[192.168.1.101]) by raven.ravenwebhosting.com with esmtpsa (TLSv1:AES128-SHA:128) (Exim 4.69) (envelope-from ) id 1O5qx3-0001nw-OY for lml@lancaironline.net; Sat, 24 Apr 2010 21:48:05 -0400 From: paul miller Mime-Version: 1.0 (Apple Message framework v1078) Content-Type: multipart/alternative; boundary=Apple-Mail-21--352377953 Subject: Re: [LML] Vibration - Composite Firewalls X-Original-Date: Sat, 24 Apr 2010 21:48:01 -0400 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: <3BA549A9-4EBB-4A20-A775-EA062E36A63C@tbm700.com> X-Mailer: Apple Mail (2.1078) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - raven.ravenwebhosting.com X-AntiAbuse: Original Domain - lancaironline.net X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - tbm700.com X-Source: X-Source-Args: X-Source-Dir: --Apple-Mail-21--352377953 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii Thanks Grayhawk. I had the cowls off and after $30 on extensions for the = torque wrench I found all 4 AN7 bolts on the mount to firewall turned = one or more faces. On a quick flight tonight it does feel different. = One more thing to look at when chasing the vibrations. Paul L2K =20 On 2010-04-12, at 7:47 AM, Sky2high@aol.com wrote: > I thought I had chased down everything that could be coming in contact = with the cowling, but I still had a low frequency vibration that was in = the airframe and not in the stick. > =20 > In a discussion with Tom Giddings, he asked, "When did you last check = the engine mount to firewall bolt torques?" "Ah, probably two years = ago," I answered. Then I used some lazy man's excuse like "Well, I = probably would have checked them next month during the annual condition = inspection." I added, "The lower cowl is such a nuisance to remove." > =20 > Well, I did pull the lower cowl and used 5 drive extensions to get a = torque wrench socket thru the foot well to the aft-side firewall nuts = only to find that 5 of the 6 required 2-4 faces turned before the proper = torque was restored (all three on the left side, the middle and bottom = on the right).=20 > =20 > After re-assembly, I went for a test flight. I could tell that things = had improved just while taxiing out. One trip around the pattern = demonstrated that the low frequency frame vibration was gone (almost = reduced to nothing). > =20 > Remember that epoxy/glass/carbon can creep a bit under pressure and = heat, and it is wise to check the torque of these bolts periodically. = Uh, especially if vibration is beginning to felt where operations were = once smooth. This is relevant with any Lancair that has a composite = firewall (wood/glass, all glass, all carbon). > =20 > My 320 mount uses AN bolts that are 7/16" x 24 with a torque range of = 450 to 500 inch pounds (37.5 to 42 foot pounds). I used 40 foot pounds. > =20 > Thanks again Tom, > =20 > Scott Krueger AKA Grayhawk > =20 --Apple-Mail-21--352377953 Content-Transfer-Encoding: 7bit Content-Type: text/html; charset=us-ascii Thanks Grayhawk. I had the cowls off and after $30 on extensions for the torque wrench I found all 4 AN7 bolts on the mount to firewall turned one or more faces. On a quick flight tonight it does feel different. One more thing to look at when chasing the vibrations.

Paul

L2K

On 2010-04-12, at 7:47 AM, Sky2high@aol.com wrote:

I thought I had chased down everything that could be coming in contact with the cowling, but I still had a low frequency vibration that was in the airframe and not in the stick.

In a discussion with Tom Giddings, he asked, "When did you last check the engine mount to firewall bolt torques?" "Ah, probably two years ago," I answered. Then I used some lazy man's excuse like "Well, I probably would have checked them next month during the annual condition inspection." I added, "The lower cowl is such a nuisance to remove."

Well, I did pull the lower cowl and used 5 drive extensions to get a torque wrench socket thru the foot well to the aft-side firewall nuts only to find that 5 of the 6 required 2-4 faces turned before the proper torque was restored (all three on the left side, the middle and bottom on the right).

After re-assembly, I went for a test flight. I could tell that things had improved just while taxiing out. One trip around the pattern demonstrated that the low frequency frame vibration was gone (almost reduced to nothing).

Remember that epoxy/glass/carbon can creep a bit under pressure and heat, and it is wise to check the torque of these bolts periodically. Uh, especially if vibration is beginning to felt where operations were once smooth. This is relevant with any Lancair that has a composite firewall (wood/glass, all glass, all carbon).

My 320 mount uses AN bolts that are 7/16" x 24 with a torque range of 450 to 500 inch pounds (37.5 to 42 foot pounds). I used 40 foot pounds.

Thanks again Tom,

Scott Krueger AKA Grayhawk

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