REFLECTOR: wheel shimmy

aminetech at bluefrog.com aminetech at bluefrog.com
Mon Feb 16 16:28:41 CST 2009


I don't know why, but my nose wheel tension is low at about 3-4 lbs and I don't get shimmy with a normal landing.  If the nose hits hard I get a "buzz" type of shimmy which isn't that bad and it goes away in a few seconds.  Several years ago I experienced that bad, bone-rattling shimmy when my tension was low, so I know what that feels like.  The only difference I'm aware of is that I replaced my wide slick type tire with a narrower, tread tire and I replaced the phenolic washer with one I made from a plastic drum.

John

--- bill.stockman at daytonaero.com wrote:

From: "Stockman, Bill" <bill.stockman at daytonaero.com>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Subject: Re: REFLECTOR: wheel shimmy
Date: Mon, 16 Feb 2009 16:53:55 -0500

I wouldn't quite say 100%.   I had his system and it failed on my
173FGE.    The problem with Kens system is what happens when you fail to
pull the pin and turn your airplane--such as leaving the runway quickly
when someone is landing behind you.    Normally the tire just scoots and
everything is fine.   But if the tire actually grabs the runway, then
something has to give--either the pin or the rest of the mechanism.   In
my case it pulled the mechanism up and stripped out the mounting
hardware.   After pulling the pin while taxing, the mechanism set back
down into place and looked totally normal--no evidence of failure (no, I
didn't attempt to tighten the screws which might have indicated a
problem).  Guess what happens next time you "lock" the wheel, fly around
and try to land?   Now the mechanism is not screwed down and if there is
any perturbation at all, it kicks the wheel sideways (shimmy) and now
the mechanism lifts up and moves, screws and all and will actually lock
the wheel sideways or at an angle and you get a real Disneyland ride.   

My wife was not impressed with the ride, but my friends on the side who
witnessed it thought it was rather impressive.

I think Ken has a good idea, but it biggest fault is that the pin is
stronger than the rest of the mechanism and will not shear off before
damaging the rest of the wheel and holding mechanism.   I realize others
have used this system successfully with no apparent problems.  However,
if you ever forget to pull the pin and turn the plane--especially at
speed--you need to fully inspect the system--which is really tough to do
after you cover it with your wheel pant--which was the whole purpose of
installing the system.   MTCW.   

Bill Stockman, Senior Associate
Dayton Aerospace
 
(937) 369-4799 cell
(937) 426-4300 work
bill.stockman at daytonaero.com



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