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Old April 11th, 2012, 06:06 PM   #1
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The Physics of Countersteering

http://www.youtube.com/watch?v=PgUOOwnZcDU
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Old April 11th, 2012, 08:18 PM   #2
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Old April 11th, 2012, 08:20 PM   #3
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[geek]

Brilliant video!!

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Old April 11th, 2012, 09:53 PM   #4
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Wow...very cool video. I love hearing breakdowns of the physics of a 2-wheeled vehicle. All the forces and counter forces....<3


Oh, and in before the over-thought questions of when to counter-steer and how much.
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Old April 12th, 2012, 02:46 PM   #5
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I love that bike... even as a toy. Great visual representation.
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Old April 12th, 2012, 04:47 PM   #6
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Suggestion taken and link posted there; thanks, Trixter
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Old April 18th, 2012, 05:04 PM   #7
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Link to original page on YouTube.

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Old April 27th, 2012, 08:20 AM   #8
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Thanks for posting the video, currently reading twist of the wrist 2, and having difficult time understanding counter steering, this is for only higher speed turns right?
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Old September 3rd, 2013, 05:58 AM   #9
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Cool

While we roll over a straight line, the weight vector starts at the CG (combined rider+bike) and points vertically down and aligned with our support points: the contact patches.
We are in vertical balance.

As soon as we deviate from a straight line trajectory, the vector weight tilts from the CG toward the outside of the turn or curvilinear trajectory.
The faster we roll and the smaller is the radius of the circular trajectory, the bigger is the angle of deviation from vertical of that vector.
We people like complicating things, so we decompose that vector into weight and centrifugal force, but in reality that tilted vector is the actual force that the bike feels.

We are approaching a right hand turn and we know that as soon as we direct the front tire to follow the trace of the right turn (a circular movement), the weight vector is going to tilt toward the left (due to gyroscopic precession and centrifugal force), putting us out of balance.
We need to roll over the bike to the right (as we start turning and as the weight vector tilts left) in order to keep that comfortable balance.
..............but how can we?

Then, we use the only thing that we can control with some authority: a turn of the handlebar.
As explained above, if we turn that bar right, we are going to be immediately out of balance, falling on our left side.
If we don't turn the handlebar, we are going to continue going straight and out of the road: no good either.
If we turn the handlebar to the left (pushing the right hand-grip) as the turn begins, we are starting a left turn and making the weight vector tilt toward the right: we are now out of balance and falling, rolling over or leaning the bike to the right (which is exactly what we needed!!!).

Right after the bike is falling to the right and acquiring the right lean angle that we needed to turn right, we can use that rolling inertia that keeps the bike falling to the right in our benefit, not needing that weight vector to be tilted toward the left anymore.

Is only now (some fractions of a second after we steered left) that we can steer to the right, just like we do in a car, making the front tire follow the trace of the curve for as long as it lasts.
By doing that, we are making the weight vector tilt toward the left and getting aligned with both contact patches.
We are in balance again !!! ............not vertically but leaned.
During the turn, we are feeling a little heavier than normal: that is due to the fact that the vector weight gets bigger as it tilts, the more it tilts, the more it grows.
If that curve and speed call for 45 degree lean, the bike and the rider weight 40% more.

We need to revert the direction of the steps in order to abandon the circular movement and lean angle at the end of the curve, resuming linear trajectory.



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File Type: jpg Countersteering-vector.jpg (149.1 KB, 5 views)
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Old September 3rd, 2013, 06:35 AM   #10
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This vid has an interesting camera pov :

Look at ~ 1:30, to see :

1) How stable the bike is (riding no hands !)

2) How just a "one finger" push is enough to start turning the bike !

And at 4:00 for some "stability testing"

Link to original page on YouTube.

Another interesting vid showing how counter-steering becomes "active" at ~20 mph. ( @ ~ 3:40)

Link to original page on YouTube.

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Old September 3rd, 2013, 07:45 AM   #11
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Thx Hernan
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Old September 7th, 2013, 11:39 AM   #12
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Well I found another video that debunks the "10 mph threshold " :

Link to original page on YouTube.

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Old September 7th, 2013, 12:27 PM   #13
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Quote:
Originally Posted by mst View Post
Well I found another video that debunks the "10 mph threshold "
Great vids, Mike; thanks !!!

There is no "10 mph threshold" per se: each bike reacts differently at low speeds, due to weight and steering geometry.

If your bike falls to the same side onto which you steer, from stopped at perfectly vertical position, then counter-steering has a hard time to work as normal for very slow speeds.
The reason is that it has to fight the effect of your weight shifted over the same side of steering.
Some bikes behave in the opposite way, in which case, counter-steering has no opponent above 0 mph.

At speeds low enough as to not generate any important centrifugal force, CG and steering geometry are the leaders of the small roll needed to achieve the small lean angle needed.
Not only the combined CG does move sideways by upper body, it also moves due to steering geometry, ...........and it follows the bike trajectory.

As speed increases, the power of counter-steering grows in a quadratic ratio (centripetal acceleration and force depend on the square of speed).

For example, in the following video we cannot know if the rider was counter-steering, but we do know that counter-steering at that low speed doesn't do much to make the bike fall into the turn.

Link to original page on YouTube.

For that speed (around 2 mph) and radius of turn (around 15 feet), the rider may be able to apply around 15 pounds of lateral centrifugal force at a CG about 3 feet high (torque of 540 in-lb).

If the bike + rider weight 400 pounds, he can achieve the same effect by moving that CG less than 1.5 inches away from the line that connects the contact patches, by upper-body lean and/or steering.

Either way, he only needs to lean the bike 2 degrees to re-establish balance during those slow turns.

As in this particular case we are talking about peanuts regarding centrifugal force and lean angle, the input of the rider is not evident enough as for anyone to certify the need for "pure counter-steering".

If you are interested in the subject, you could find very good descriptions at Tony Foale's page:

http://www.tonyfoale.com/Articles/Balance/BALANCE.htm



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Old September 8th, 2013, 09:12 PM   #14
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To over simplify, stand with one foot on front of the other about 2' apart, (like motorcycle wheels) now if someone sweep kicks your front foot to your right, you will fall to the left, and vise versa. Counter steering is basically turning/sweeping the tire out of line (right or left) making the motorcycle fall to the opposite side.
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