Have you checked for main gear wheel balance?  This may be an imbalance of the 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 main gear legs have a longitudinal response near the tire rotation frequency at 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 you get the shimmy, but it would be interesting to correlate vibration frequency with groundspeed.  This may be another use for that iPhone app (Vibration) I described recently.  Just set it to its maximum sample rate for the longest duration and have someone not flying start to record right before touchdown. I think you can sample at 100 Hz for 40 seconds, which should be plenty to capture it. Then note the GPS groundspeed where the maximum vibration occurred.  Since the vibration grows so significantly during the shimmy the frequency 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 airplane.

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,
>
> I'm looking for some thoughts on a persistent nose wheel shimmy that refuses to go away. I have serviced the strut as outlined by the Lancair service procedure 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 thoughts?
>
> Shane Daly
> L-ES  C-GICX
>
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