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Gary,
I had really bad shimmy when braking
during my initial taxi tests back in 2002. We assumed it was the nose
shimmying - it sure felt that way. It was so bad I removed the strut
and sent it back to Lancair to have it checked out. They pulled it apart,
found nothing wrong, serviced it and sent it back. Next taxi test has
the same results. So I did a medium speed taxi past my builder guru and
hit the brakes. He said it was not the nose, but my right main mount that
was shaking like a leaf.
Grove Aircraft is on the same field
where I built the plane and Robbie Grove offered to check my brake
rotors. He found an extremely small warp in the right one. He turned
that rotor for me, I put it back on and the problem disappeared
completely.
I have since periodically had the
common shimmy many builders have when braking through about 30 knots. When
it's gotten bad enough, I've put a new rotor on and the problem goes away.
I know my shimmy is not from the nose - it's from one or both of my mains
oscillating like a pitch fork when I brake if my rotors have even the slightest
bit of warp in them. A momentary release and reapplication of the
brakes is all it takes to stop it. Selective releasing of one brake at a time is how I determine which
one is causing the problem.
If you want a new rotor, you can order
one from Lancair. I now have two replacement rotors on my plane and plan
to take the originals to an auto shop to see if they can turn them so I'll have
replacements ready to install when I need them in the future.
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