Re: Counter steering dynamics [was: Humbled again]

 sean_q wrote:

You're hunting in the wrong direction. Steering geometry pertains to control
and stability. Those forces are small compared to lateral reactions at the
contact patch for a motorcycle at speed in a turn. Lateral (centripedal)
force is what turns the bike. Yaw rate is governed by front/rear lateral
force imbalance, not steering geometry or bar position. Steering the bar
changes this balance. Normally, yaw rate just matches the turn rate, such
that the bkie yaws through N degrees in the same time the velocity turns
through N degrees.

If we steepen the turn momentarily by pushing on the outside bar, the
increased slip angle on the front generates more lateral force and turns the
front more relative to the rear. The bike yaws toward the rider, and so
leans him toward upright. This is, of course, countersteering. Being more
upright now, the rear generates less camber thrust and the turn widens.

It's pretty amazing that we do all this routinely, effortlessly in the
milliseconds it takes to happen. The point here, though, is that handlebar
position in a steadystate turn is much less a function of steering geometry
than it is of over/understeer balance. Steering geometry comes into play in
keeping bar forces more or less neutral in the steadystate turn. Some bikes
feel "heavy" and need a continual push on one bar or the other to hold a
turn. Others are more neutral and need little or none.

 sean_q wrote:


Huge snip.

As you're bored at the moment, can I suggest some books to keep you
occupied. Firstly, go to www.tonyfoale.com and buy his most excellent book.
It answers all your questions and will clarify what is actually happening.
It also is a damn good book, easy to read with clear descriptions and
worthwhile illustrations. He backs up theory with experimentation and
documents each step.

Another to consider, if you don't already own a copy is 'The Sportsbike
Performance Handbook' by Kevin Cameron. His TDC 1+2 are a cracking read too.
The section in TDC 2 regarding tyres is the most informative work on tyres
I've ever read.

Someone else recommended 'Total Control' by Lee Parks. Another good read.

Something to watch rather than read?, try 'A Twist Of The Wrist 2' DVD.

Work your way through that little lot while your shoulder heals.

GWS, and then go put some of the above in to practice.