Message-ID: <3779901B.110555B3@mc.net>
Date: Tue, 29 Jun 1999 22:33:48 -0500
From: jerry@mc.net
Reply-To: jerry@mc.net
To: Lancair Mail List <lancair.list@olsusa.com>
Subject: Nose Wheel Shimmy
Mime-Version: 1.0

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I agree with Chris Zavatson when he says, " It must
be a specific combination of all the factors mentioned that initiates
a shimmy."

Here is my 2 cents worth on the subject:

The bearing blocks holding the upper strut pivot points are "tied
together" across the lower front of the mounting plates with one long
bolt and steel sleeve.  The upper back side cannot accept a bolt like
this because the strut would conflict, of course.

In my view the trailing edges of the bearing mounts are moving a few
thousandths of an inch in the process of a shimmy getting up to
speed.  This few thousandths of an inch is leading to the fracture of
the engine mount in the worst case shimmy scenario.  The steel
mounting plates for the bearing blocks are free to move independently
of each other during the violent twisting action of the upper strut.
If only it were possible to bolt across the upper trailing edges of
the bearing mounts this may check their movement and stiffen the
bearings in their mounts.

If the bearing blocks had extended corners on the top rear they could
be bolted together and sleeved like the lower front corner.  Better
yet throw out the steel sleeve and use two rods with rolled threads
and check nuts each side of the bearing block/mount.

Jerry Grimmonpre'           L320


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