REFLECTOR:Nose Gear Shimmy

[Chuck Jensen]

Well, in answer to John's query about the pressure I carry in the nose tire,
and contrary to Steve's experience, I found the softer-the-better, at least
to the point that the tire is "squishy" when pilot/copilot is loaded.  On my
first post, I was going to put in the pressures, then I thought that I might
just be showing/confirming my ignorance.

At that risk, the initial pressure was 16.5#, which was a shock when I took
the reading because usually a smaller tire will have a higher pressure and I
run my mains at 40#.  So, I pressured the nose to 35#, which resulted in the
shimmy.  When I reduced it back to 15.0#, the shimmy was gone.  I then
tightened the washers 1/3 turn to cinch them up a bit.  I haven't tried
increasing the air pressure since tightening the washers.  I'm going to
locate a good grass strip by my home base before I do that!

Previously, I had the washers really tightened down and got tired of having
to "punch" the brakes to get the nose to break loose for steering.  I
disassembled the nose gear (it was pretty dry and grabby), cleaned, buffed
and regreased everything.  When I put it back together, I tightened it to be
somewhat less (though not measured) than the 15-20# recommended break-away
force.  This worked great, easy to steer, until I increased the tire
pressure and made the tire hard.  My theory is the slightly softer tire may
incur greater friction and less bounce which reduces shimmy tendency, though
Scott's experience is directly contrary.  

A possible side benefit of the soft tire is less stress on the nose gear
during landing, particularly a hard one.  (I've never done one, you
understand, but I hear stories about others with lesser piloting skills.)
The slight compression of the front tire would seem likely to reduce the
impact-shock if your nose drops on the runway instead of greasing it on like
I always do.

Chuck
With ocean property in Arizona.



-----Original Message-----
From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On
Behalf Of Scott Derrick
Sent: Wednesday, August 06, 2003 12:54 PM
To: reflector@tvbf.org
Subject: Re: REFLECTOR:Nose Gear Shimmy


Chuck,

That's very interesting!! I worry about the pressure in the nose gear, 
one because its so lightly loaded before I get in there is no visual 
indication of low pressure, two its a bear to check or fill, thus 
inducing the "I'll get that later" thought as I eye it during pre-flight.

I do keep my castoring pressure washers pretty tight, which makes 
turning a chore at times but I hate a shimmy.

Scott

aminetech@dixie-net.com wrote:

> Chuck,
> That's a good tip.  How much air pressure do you use?
> 
> John
> 
> 
>>Moral of the story?  It may be that too much air pressure in the front
>>tire makes it "hard" and contributes to nose wheel shimmy.  This is
>>probably not news to 98% of you, but for the rest of us 2%, it's worth
>>keeping in mind.
>>
>>Chuck
> 
> 
> 
> 
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