X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sat, 29 Sep 2007 00:55:41 -0400 Message-ID: X-Original-Return-Path: Received: from wx-out-0506.google.com ([66.249.82.236] verified) by logan.com (CommuniGate Pro SMTP 5.1.12) with ESMTP id 2358294 for lml@lancaironline.net; Fri, 28 Sep 2007 20:36:16 -0400 Received-SPF: pass receiver=logan.com; client-ip=66.249.82.236; envelope-from=msteitle@gmail.com Received: by wx-out-0506.google.com with SMTP id i27so2253590wxd for ; Fri, 28 Sep 2007 17:35:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=beta; h=domainkey-signature:received:received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:references; bh=tAx/55cG/pslH1w7i9ETD2WMrjBf4RxF7s5UDJT9MKA=; b=Ah2b8mvrTaLjb9JIxKSyNlKs6gUwPzhV3D2ztwCi1N6qMscHZs3LXgzlEALLNF68i2pDPyXg07mZTYYvTxcPEoEJzVpU5mIKUGlIarOG44fEjj73ohWj8yJyMzHXl2ODNgfLNUu6ID2s0A+5ogvCfetnO4WXxZoieBfqvOpnq1k= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:references; b=HazGgr2mBqm610HP/5I0EacQiGh2e8Yhq16Ufs3HsRI3c3ERSH2uwQmbTI1oBzGdXuir02H6EQMXKV5qaJLsaKzFoVMib8fo0cuSpy0hM4AqPVgHVdxLmzGSqMsJCBfnTDr0kC9T8C1gXerPyf9EnIq8q80i8mHqoLNDSnJ3Cp8= Received: by 10.90.106.11 with SMTP id e11mr6910719agc.1191026140059; Fri, 28 Sep 2007 17:35:40 -0700 (PDT) Received: by 10.90.35.16 with HTTP; Fri, 28 Sep 2007 17:35:39 -0700 (PDT) X-Original-Message-ID: <5cf132c0709281735q6bb79ef8rcf0e115fbd778840@mail.gmail.com> X-Original-Date: Fri, 28 Sep 2007 19:35:39 -0500 From: "Mark Steitle" X-Original-To: "Lancair Mailing List" Subject: Fwd: Lancair nose gear. In-Reply-To: <5cf132c0709280333t17fa0a7eqe440c75f7ad9b75@mail.gmail.com> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_3844_3162196.1191026140044" References: <46FC8D80.9090909@earthlink.net> <5cf132c0709280333t17fa0a7eqe440c75f7ad9b75@mail.gmail.com> ------=_Part_3844_3162196.1191026140044 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline I mentioned to an engineer fried the problem some of us are having with cracked motor mounts. His response was interesting to say the least. Mark S. (I wrote) On another subject, some of the Lancair ES's have developed cracks in their motor mounts. I may need to remove my mount and send it back for magna-fluxing and repair. There have been a number of severe shimmy incidents, one resulted in nose gear collapse. They're still trying to figure out why that's happening. I have not experienced any shimmy in six landings, but they usually begin later on, after 100 or so landings. Personally, I believe that the mounts are cracking which weakens the mount and allows the shimmy to occur. The cracks are on the cross-over tube right at the nose strut attachment. I'll be inspecting mine for cracks this weekend. Hopefully, I won't have to ground it for mount/strut repairs. Other than that, it flies great! Mark S. Sorry about messing up the margins. ;-( From just looking at these pictures of the MM it does not look like it has any positive damping in rotation other than the friction in the cylinder seals. Once the seals wear a bit the friction is probably reduced. A scissor link and a circular disk damper could be retrofitted. I'll do a 3D for you. The structural design is not great either. It needs an FEA done as there are tubes in bending and torsion. I take it you are using the stock Continental bed mount. I have never been a fan of that mount. Also some of the bays are not triangulated. CC copied it unfortunately. I take it you steer with the brakes? Has Tom Parke's had any nose gear problems. Tom? Paul Lamar ...No rotor no motor. The Rotary Engine NewsLetter. Powered by Linux. ACRE NL web site. http://www.rotaryeng.net Copyright 1998-2006 All world wide rights reserved. ********************************************************************************************************** Paul, I figured some sort of bending/twisting was happening to cause those cracks. As for the strut, it does have an internal damping mechanism. Some of those have blown the o-ring which resulted in severe shimmy, or maybe it is the other way around (severe shimmy caused it to blow the o-ring). There's a mod to those to add a second o-ring. So far, mine is doing fine. I feel that the shimmy is caused by the weakened motor mount. The strut mounts in the area where the cracks are forming. Would you mind if I forward your analysis of the Lancair motor mount to the Lancair group? They are headed down the path of adding gussets. I don't feel they are addressing the real problem (as you described). Thanks, Mark ------=_Part_3844_3162196.1191026140044 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline
 
I mentioned to an engineer fried the problem some of us are having with cracked motor mounts.  His response was interesting to say the least. 
 
Mark S.
 

(I wrote)
    On another subject, some of the Lancair ES's have developed cracks in
    their motor mounts. I may need to remove my mount and send it back for
    magna-fluxing and repair. There have been a number of severe shimmy
    incidents, one resulted in nose gear collapse. They're still trying to
    figure out why that's happening. I have not experienced any shimmy in
    six landings, but they usually begin later on, after 100 or so
    landings. Personally, I believe that the mounts are cracking which
    weakens the mount and allows the shimmy to occur. The cracks are on the
    cross-over tube right at the nose strut attachment. I'll be
    inspecting mine for cracks this weekend. Hopefully, I won't have to
    ground it for mount/strut repairs.

    Other than that, it flies great!

    Mark S.

    Sorry about messing up the margins. ;-(

     From just looking at these pictures of the MM
    it does not look like it has any positive damping in rotation other
    than the friction in the cylinder seals. Once the seals wear a bit
    the friction is probably reduced. A scissor link and a circular
    disk damper could be retrofitted. I'll do a 3D for you.

    The structural design is not great either. It needs an FEA done
    as there are tubes in bending and torsion. I take it you are using the
    stock Continental bed mount. I have never been a fan of that mount.
    Also some of the bays are not triangulated. CC copied it unfortunately.

    I take it you steer with the brakes?

    Has Tom Parke's had any nose gear problems. Tom?

    Paul Lamar ...No rotor no motor.




The Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site. http://www.rotaryeng.net
Copyright 1998-2006 All world wide rights reserved.

 

**********************************************************************************************************
Paul,
 
I figured some sort of bending/twisting was happening to cause those cracks.  As for the strut, it does have an internal damping mechanism.  Some of those have blown the o-ring which resulted in severe shimmy, or maybe it is the other way around (severe shimmy caused it to blow the o-ring).  There's a mod to those to add a second o-ring.  So far, mine is doing fine.  I feel that the shimmy is caused by the weakened motor mount.  The strut mounts in the area where the cracks are forming. 
 
Would you mind if I forward your analysis of the Lancair motor mount to the Lancair group?  They are headed down the path of adding gussets.  I don't feel they are addressing the real problem (as you described). 
 
Thanks,
Mark
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