Quote:
Originally Posted by eddiekay
Chris....Motofool made his point well "center of mass chasing the contact patch" OK...so we'll see tomorrow ?
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I believe that I should have clarified that we were looking to the bike from above.
When applying front brake hard, the Center of Mass tries swinging laterally (which is its easiest way to move forward of the contact patch that is resisting the forward movement), inducing a fishtail movement (sometimes a small side-to-side oscillation, sometimes a one-side-slip that reaches some appreciable angle).
Something similar happens to airplanes with two main wheels at front (tail-draggers).
Once the rear little wheel is up in the air, the airplane becomes harder to keep on a straight trajectory as it tends to fish-tail, harder when landing and applying brakes.
Another example is what happens when we are pushing a heavily loaded wheelbarrow and the tire encounters a big rock.
When you see a Moto GP racer braking with the rear tire in the air, he is using the handlebar to keep the balance, which only means to keep that Center of Mass perfecly aligned with the front contact patch.
With minute inputs onto that handlebar, he is slightly moving that contact patch side to side as the C of M tries to swing around.
Same happens when we try balancing an upturned broomstick on the palm of our hand: we slightly move the point of support horizontally around, following the natural tendency of the broom to fall.
If we delay the needed reaction, the deviation between C of M and pivot point becomes too big and almost impossible to correct.
That is known in Physics as an inverted pendulum, which is inherently unstable and must be actively balanced in order to remain upright.
Those riders master two important things: a fine sense of tri-dimensional balance (can feel minimum deviations) and quick but moderate reactions (input exactly the necessary feedback to keep total control).