Re: for Eric and ...heavy crosswinds.

[Eric Sheley <eric@xxxxxxxxxx>]

At 12:21 AM 5/1/00 -0700, don draper wrote:
>  The amount of effort required to correct for a crosswind is DIRECTLY
>proportional to the height of the CG above the roll center of the
>bike.

Huh ? We weren't talking about the amount of effort required.

The original question was not why it was required to lean in, but rather 
why in addition to leaning into the force there was also a certain amount 
of force that was required, directly opposite to the lean angle (in this 
case in the direction of the wind).

Let me see if I can break it down a little simpler. I will forgo the vector 
mechanics discussions as I don't think that will make the scenario any 
clearer.

These are some broad generalizations:

1 - A bike travelling in a straight line will continue to do so unless some 
external force is applied (wind, input from the bars, throttle etc)

2 - A bike travelling at a lean angle will travel in the direction of that 
lean (again very basic - we are not concerned with cg here)

3 - If the lean angle is increased the radius of the turn will be decreased

Of course in addition to the angle, the radius can be changed by tire size, 
tire profile, wheelbase etc.... we are not concerned with these factors here.

So we now have our bike travelling in a straight line. We now add a force W 
(wind) from the right, perpendicular to the direction of travel (things get 
really fun when the angle is <> 90). So in order to compensate for a 
quickly shifting motorcycle the rider begins to "lean into" our force W.

Now - abruptly remove force W. What does the bike do ? It immediately 
begins to turn to the right. Now add the force W again. That same tendency 
to turn is still present - only now, force W is acting against it. However, 
if the combination of the lean angle and the profile of the tire at the 
contact point are such that a turn in the direction of travel is still 
being caused (even at a minute level), some force must be introduced into 
the equation to compensate (to cancel out this tendency to turn). In this 
case a constant pressure to the left would be required - which is why even 
though leaned to the right, Patti had to exert a constant pressure on her 
left bar to maintain straight travel.

There - clear as ...... mud ?

Respectively submitted

- - Eric


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