Gene,

 

I've been following the ES shimmy issue on the Yahoo ES group.  The ES nose wheel strut is the same as the retractable one on the IV, but it's bolted in place.  The IV hasn't has the same problems.  So the current investigation in on the added mass of the nose wheel pant. 

 

The other issue is the hot engine cooling air gets pushed down inside the strut fairing, causing the oil in the dampener to heat up.  That's something that's been measured by someone with heat probes.  Warmer oil is thinner, less dampening.  But the IV strut is tucked up inside the cowl during flight, and the turbocharged engine makes more heat.  Incidentally, Bryan has a turbocharged engine.

 

Lancair has designed a new strut with much stronger dampening built in.  In the first tests, Tim said it worked really well, almost too well.  He said the worst part was parking the airplane.  The tow bar was barely able to turn the wheel!  He said the extra stiffness didn't affect ground handling.  He's looking into ways to lessen the dampening strength.

 

Some of the existing ES struts have been modified by adding an additional O ring to stiffen them up.  Different viscosity oils are being tested also.  Some oils, I guess, maintain their viscosity better when they get warm.

 

Another solution that's being tested is going to a all carbon lightweight nose wheel pant.  Some guys are blocking the air flow from getting down the gear leg fairing.

 

Another issue is the rake angle of the nose strut.  There seems to be quite a wide variance between builder in the angle.  The spec is 0, but the range seems to be between 0 and 5 degrees (wheel ahead of the upper mounting point).  That may or may not affect the shimmy.

 

That's about all I know, probably more that you wanted to hear about!  :-)

 

Mike