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Old 08-31-2013, 05:30 AM   #934
PFFOG
Richard Alps-aholic
 
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Joined: Aug 2005
Location: Western NY, further from NYC than 6 entire states
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OK here is something for both sides to argue about.

Thais is an excerpt from Motorcycle Handling and Chassis Design the art and science, by Tony Foale Considered the Bible of motorcycle dynamics by many.

First is explains in detail what initiates the turn. For those that feel they must know exactly how it works in order to do it. (have fun trying to consciously apply this while riding). And for those that claim you counter steer all the way through a corner it shows why normally you do not, but at a point turn in the direction you want to go.

And the point I have tried to make , at the end, the brain with visual and information from our cochlea, and semicircular canal (inner ear) process and adjust rapidly. Yes people run off corners, not because they don't know how to counter steer, but because they get scared and look for an out, and as soon as they turn their head to look away from their target, 1/2 of the brains input changes channel, and your brain steers you there. IMHO LOOKING WHERE YOU WANT TO GO is a better lesson than learning the dynamics of counter steering.

So here is Tony Foale's in depth analysis.

Initiating a turn
The basics
How do we actually initiate the turn, we have already seen that a moving motorcycle has an automatic tendency to stay upright? Do we lean first or steer first? If we were to turn the handlebar in the direction we want to go, both centripetal tyre force and gyroscopic precession of the front wheel would cause the bike to topple outward. Therefore, if we momentarily turn the bar in the opposite direction, then the centripetal tyre force and, to a much lesser extent, the gyroscopic reactions will cause the machine to
bank to the correct side. There are four main effects to be observed.
• A steering action to the right, will cause the machine to start turning right, and just as in a car,
centripetal tyre force will cause a lean to the left. This is the major banking influence.
• This steering action as we have seen, will also produce a small precessional tendency to lean the
machine to the left. This is a small effect when the wheels are on the ground, as shown later.
• Gravity will then initially augment the banking effect, but this will become less important as the tyre
cornering force builds up and balances the gravitational moment completely, when the bike reaches
the steady state lean angle.
Balance and steering 4-7
• The velocity of banking or roll rate will give rise to gyroscopic torques which oppose the rider’s
counter-steering input helping to steer the front wheel into the curve. This gyroscopic torque is in
opposition to the rider applied steering torque, and in fact balances most of his input and hence
works against rapid steering. However, without this “negative feedback” the bike would be rather
unstable and very hard to control, as we shall see.
These forces will also act on the rear wheel which, because it is rigidly attached to the bulk of the
machine, will tend to make the machine yaw into the curve. However, this reinforcing effect is secondary
to that of the front wheel. Steering rake and front-wheel trail, also help steer the machine into the curve
as the lean angle builds up. When we have established our correct lean angle, the processes for
maintaining balance, as described above, will come into effect and help keep the bike on our chosen
path.
We have seen, then, that a turn can be initiated by steering momentarily in the “wrong” direction.
Termed “counter-steering”, for most riders this action is accomplished subconsciously. In racing, riders
often make use of deliberate counter-steering to achieve the high roll rates necessary under those
extreme conditions. Briefly, it is the combination of gyroscopic moments and centripetal force that
requires this counter-steering action, we don’t have a choice in the matter. There are those that would
have us believe that counter-steering wasn’t known about until the 1970s. or ‘80s.. This is nonsense, it
is well documented that around the start of the 20th century the Wright Bros. were well aware that this
was the mechanism for turning a bicycle. In the early 1950s., whilst chief engineer at the Royal Enfield
motorcycle factory, Wilson-Jones did a series of tests with real motorcycles to investigate this further.
The results of these and some of his other experiments into steering geometry were published in
engineering journals.
However, counter-steering doesn’t explain how we can corner “hands-off”. Although, whilst it is possible
to do this, it is accomplished only with a lot more difficulty. So let us consider what happens if we try to
lean without being able to steer. As there is nothing solid for us to push against, the only way we can
apply bank is to push against the machine with the inertia of our own body. To lean the bike to the left,
we must therefore initially move our body weight to the right. The left leaning bike will now generate
camber forces from the tyres tending to lean both rider and machine over to the right, the roll rate will
again cause a gyroscopic steering torque which helps ensure correct balance. The initial bike lean to the
left might well be considered as a ‘counter-lean’, analogous to the ‘counter-steer’ of hands-on turning.
Anyone that has tried changing direction ‘no-hands’ will know that we have far less control over the
machine with just body movement available. The mechanisms involved with counter-steering produce
much greater response and more finesse of control.
So, we now have two possible methods of initiating a turn and it is interesting to note that in both of them
(banking and counter-steering) our physical effort is in the opposite sense to that which might be thought
natural. When learning we adapt quickly and the required action becomes automatic. It is these reverse
actions that require us to learn to ride in the first place. The required responses are clearly counter
intuitive. When learning most of us initially wobble about out of control until our sub-conscious latches
on to the fact that counter-steering and counter-leaning is the way to do it. Once the brain has switched
into reverse gear, it becomes instinctive and is usually with us for life, and we can return to riding after a
long layoff with no need to re-learn the art of balancing or steering.
In practice, we sub-consciously combine both methods, with some steering and some body motion. The
relative proportions by which we combine the two methods depend partly on riding style but also on
speed and machine characteristics. For example, a heavy machine with light wheels at low speeds
demands a different technique from that appropriate to a light machine with heavy wheels at high speeds
4-8 Balance and steering
and hence a different feel. However, humans adapt quickly and the correct technique soon becomes
second nature.

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Richard
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