On Thu, 30 Jul 2015 11:36:15 -0400, Ed Huntress
wrote:


Ok, since we've now run into two people with the temerity to talk
about the factors involved in front-wheel oscillation, where does
precession come into it? Or doesn't it?

I don't see how. On bikes the culprits tend to be loose steering
heads, unbalanced fork springing or damping, dogtracking, bad tires,
etc. On the model of plane I know had the issue, it was probably
rooted in zero rake, negligible trail, rigid lamb tire, and tiny
contact patch. And set off by poor elevator leverage at slow speed
allowing the nose to smack down. A friction damper cured it so long as
its tune was maintained, which was unreliable in the usually oily
environment. A secondary hydraulic damper was added, but there were a
number of incidents of wheel oscillating violently from stop to stop
followed about 1 second later by the nose wheel making a run for it. I
experienced a minor case of it myself and from then on became
religious about checking both dampers.