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From: "DON & PAT RYAN" <djpryan@ruralnet.net>
To: "Lynda Franz" <LNN@Lancair.net>, "Marv Kaye" <lancair.list@olsusa.com>
Subject: SDR NG Cyl. Attch Failure
Date: Tue, 1 Jun 1999 09:03:27 -0600
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Lancair 360, N15EG

The phenolic block at the top of the nose gear tunnel has delaminated the
fiber glass and raised up ca 3/32".  This is the nose gear hydraulic
cylinder attach point and the must be similar to those reported by George
Shattuck, SDR 4/97 and the SDR on 5/98.

I would like to hear how the failure fixes have worked.  Geo reported that
he repaired his with a steel strap in LNN issue #27.  With no further info,
I plan to round up the top of the tunnel with flox and use a 10 bid
fiberglass overlay extending down the sides of the tunnel in a forward
direction. Rounding the top should reduce the stresses at the edges of the
phenolic and transfer the loads to the tunnel side walls? IMHO?.

It would appear to me that this failure is from overextending the cylinder
and NOT from landing stress?? Any comments from the engineeringly inclined??

Don Ryan


[This problem has been discussed here and in the LNN as well several times
and the typical cause of the failure has been that the nose gear actuating
cylinder was not adjusted properly.  The ends of the piston's travel must
match the ends of the strut's travel.  If the strut stops moving while 
there is still motion available to the piston, the piston will move to 
its stop and damage the mounting point.  It does require the builder to
fiddle with the cylinder and rod end a bit, but it's important that the 
travel is cylinder-limited and not strut-limited.  If the strut stops
moving while there's still travel avilable to the actuator piston,
the only object remaining to absorb the load is the mounting point... not
a good situation at all.

If your installation will not allow you to adjust the rod end to effect
this particular result, it is possible to contact the cylinder manufacturer
and request a spacer that you'll have to install into the inside of the
cylinder, which will limit its travel internally.  This would add far
less weight than would beefing up the attach point to take loads for which
it wasn't designed, and would allow the system to operate as intended.

Just my $0.02...  alternating viewpoints are welcomed.

    <Marv>      ]

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