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Date: Wed, 31 Jul 2013 07:29:35 -0400
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Subject: Re: [LML] ES Nose gear shimmy
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From: Kyrilian Dyer <kyrilian_av@yahoo.com>
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Have you checked for main gear wheel balance?  This may be an imbalance of t=
he main tires resulting in yaw, of the fuselage and this lateral response at=
 the nose gear.

Based on your symptoms and other discussions in the past, I wonder if the ma=
in gear legs have a longitudinal response near the tire rotation frequency a=
t some intermediate speed.  On a 6.00x6 main tire at 50 kts groundspeed, for=
 instance, this would equate to around 19 Hz.  I'm not sure at which speed y=
ou get the shimmy, but it would be interesting to correlate vibration freque=
ncy with groundspeed.  This may be another use for that iPhone app (Vibratio=
n) I described recently.  Just set it to its maximum sample rate for the lon=
gest duration and have someone not flying start to record right before touch=
down. I think you can sample at 100 Hz for 40 seconds, which should be plent=
y to capture it. Then note the GPS groundspeed where the maximum vibration o=
ccurred.  Since the vibration grows so significantly during the shimmy the f=
requency plot should show the frequency of the shimmy.

If it's bad and you're uncomfortable repeating this, then by all means, don'=
t do this. Perhaps you can find someplace to balance your tires off the airp=
lane.

Just my $0.02.  ES owners may have other, perhaps more useful advice.

- Kyrilian


Sent from my iPhone

On Jul 30, 2013, at 2:43 PM, "Shane" <f4u5n@shaw.ca> wrote:

> Hello All,
>=20
> I'm looking for some thoughts on a persistent nose wheel shimmy that refus=
es to go away. I have serviced the strut as outlined by the Lancair service p=
rocedure twice now with no change. The shimmy does not happen on touch down,=
 but shortly after on the roll out and is brief, but very noticeable. Any th=
oughts?
>=20
> Shane Daly
> L-ES  C-GICX=20
>=20
> --
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