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 Questions RE: Tip 233: Slow-Speed Countersteering?
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BennyRayRiddle
Starting Member
7 Posts


Beverly Hills, CA
USA

(None)

Posted - 08/18/2012 :  4:48 PM                       Like       
quote:
If it were counter-steering, then you would make one steering input to accomplish the turn, not two.
This statement has me completely stumped. Why does the definition of counter-steering require the condition of a single steering input?

Mr. Davis states that the definition given by the narrator of the video for counter-steering is incorrect, but does not provide his own clear and concise definition. What is it? Also, what is his definition of direct-steering? I expected that direct-steering means that if the bars are rotated to the right, then the bike will turn right without falling over. In the video the bike clearly falls the opposite direction of the first "direct-steer". Turning right and the bike falling left is an example of counter-steering, not direct-steering ... right?
Mentors These Mentors provided these Answers to the Question

James R. Davis
Male Administrator
17284 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 08/19/2012 :  8:28 AM Follow poster on Twitter  Join poster on Facebook as Friend  
Perhaps I was confused with my understanding as I wrote the tip.

So let me see if I get your point properly ...

Suppose you are moving in a straight line at 10 MPH and decide that you must come to a stop. If you use the throttle to increase your speed to 20 MPH, then use your brakes to reduce your speed to zero, would you call that a counter-braking maneuver?

At slow speeds, you can cause your bike to lean before changing direction (steering). At higher speeds, you cannot cause your bike to lean in a direction other than you are steering. That is, a change of direction causes a lean while leaning can cause a change of direction. If leaning caused a slow speed turn in the direction of the lean, then obviously turning away from the lean is both superfluous and counter-productive in that it must immediately be followed by a change of direction toward the lean.

There is no doubt that you can direct-steer away from the direction you want to turn followed by direct-steering in the direction you actually want to go (a 'dip'), just as it is possible to simply turn in the direction you want to go in the first place - at slow speed.

Steering is accomplished by changing the direction the front wheel points. If, turning the handlebar to the right (clockwise, and maintaining that direction) CAUSES a change of direction to the right, that is a direct-steer maneuver. If it CAUSES a change of direction to the left, it is a counter-steer maneuver. In either case, it is a single steering input. Below about 10 MPH, that single steering input is direct-steering while at speeds above about 10 MPH, it is counter-steering.
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BennyRayRiddle
Starting Member
7 Posts


Beverly Hills, CA
USA

(None)

Posted - 08/21/2012 :  3:01 AM
Thank you for your reply. After thinking about it for a few hours and still being unable to figure out your explanation I typed out the text below in hopes that you can explain either where I am incorrect or how our definitions contradict each other.


Imagine a motorcycle traveling in a straight line at any speed (with a perfect, wobble-free rider.) The rider rotates the handlebars left. The left-pointed front wheel causes the contact patches to travel left and out from under the center of mass and the bike to begin leaning right. The rider holds the bars in the leftward position. The maneuver ends with the bike crashing onto its' right hand side.

Imagine a motorcycle traveling in a straight line at "low" speed (with a perfect, wobble-free rider.) The rider rotates the handlebars left. The left-pointed front wheel causes the contact patches to travel left and out from under the center of mass and the bike to begin leaning right. The rider then rotates the bars right, past their initial position (center), and points them into the turn. The maneuver ends with the bike in a constant radius turn at a constant lean angle with the front wheel pointing into the turn and the rider applying a maintenance torque to hold the bars at their current angle.

Imagine a motorcycle traveling in a straight line at "high" speed (with a perfect, wobble-free rider.) The rider rotates the handlebars left. The left-pointed front wheel causes the contact patches to travel left and out from under the center of mass and the bike to begin leaning right. At speed the steering geometry's self-righting tendencies create a right torque in the bars. The rider's second input is a left torque to control the bar's rotation. The bars rotate right, past their initial position (center), and point into the turn. The maneuver ends with the bike in a constant radius turn at a constant lean angle with the front wheel pointing into the turn and the rider applying a maintenance torque to hold the bars at their current angle.

In summary:
- Direct-steering causes the bike to crash on the side opposite the attempted turn at any speed.
- At low speed the rider guides the front wheel through a two-step motion away from and then towards the desired line that sets the appropriate lean angle and initiates the turn.
- At high speed the rider guides the front wheel through a two-step motion away from and then towards the desired line that sets the appropriate lean angle and initiates the turn.

How can direct-steering work at any speed if it always causes the motorcycle to crash?

The second two items are qualitatively identical. How can one be counter-steering and one not?
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James R. Davis
Male Administrator
17284 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 08/21/2012 :  7:39 AM Follow poster on Twitter  Join poster on Facebook as Friend  
You start with a false premise:
quote:
Imagine a motorcycle traveling in a straight line at "low" speed (with a perfect, wobble-free rider.) The rider rotates the handlebars left. The left-pointed front wheel causes the contact patches to travel left and out from under the center of mass and the bike to begin leaning right.


What causes this phenomenon at higher speeds is momentum (centripetal force). At low speeds, this does NOT happen. Momentum is a function of speed. Turning the handlebars left shifts the CM LEFT and without sufficient centripetal force offsetting gravity, the bike begins to lean to the LEFT.

You used the term 'center of mass'. Surely you recognize that the only mass that moved when you turned the handlebars to the left was the front-end (well, the front-end also got lower), and it moved left, not right. Thus, when you turn the bars to the left, you are causing the CM to effectively overhang the contact patches on the left side.

At a dead stop, bike vertical, unless you are straddling the bike and prevent it, if you turn the bars to the left, the bike will lean to the left. (That's how you park, right?)

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BennyRayRiddle
Starting Member
7 Posts


Beverly Hills, CA
USA

(None)

Posted - 08/21/2012 :  5:25 PM
I considered that, but presumed that it would be quickly overwhelmed at all but ultra-low speeds. Which makes no sense. When I'm doing a track-stand and start to tip left I rotate the bars left to compensate.

It was impossible for me to tell one way or the other when straddling my motorcycle. It became observable (barely) once I got the road bike out, though. Rotating the bars left caused the contact patch to shift left of the frame (and CM.) Which does make sense given the offset in the triple tree and the curve in the road bike forks. If the offset is 2" and the bars ninety degrees left with the frame vertical, then the contact patch has to be 2" left of the frame's center line.


quote:
What causes this phenomenon at higher speeds is momentum (centripetal force).
I think you mistyped this. In SI units momentum is kg*m/s and force is Newtons or kg*m/s^2.
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BennyRayRiddle
Starting Member
7 Posts


Beverly Hills, CA
USA

(None)

Posted - 09/08/2012 :  12:57 AM
This has been in the back of my mind and there are several things I still do not understand:
- First off, my original question: Why do you define counter-steering as requiring a 'single' input?
-- Why do you refer to a continuous application of torque over an extended period of time as a 'single' input?

- Why do you believe that the combined CG moves right of the contact patches when the handlebars are rotated right?
-- Why do you believe this phenomenon is significant at anything beyond trivial speeds and steering angles?
-- If the opposite premise was true (rotating the bars right causes the CG to be displaced left relative to the contact patches) would direct-steering be possible? If no what term would you use to describe the low-speed turning process?

- What do you believe happens exactly at the point between direct- and counter-steering?
-- Direct- and counter-steering are mutually exclusive and the bars can only be rotated two directions, therefore by deduction the bike cannot be steered at that point. Correct?
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The Meromorph
Male Moderator
834 Posts
[Mentor]


White House, TN
USA

BMW

R1100RT

Posted - 09/08/2012 :  1:42 PM
quote:
Originally posted by BennyRayRiddle

This has been in the back of my mind and there are several things I still do not understand:
- First off, my original question: Why do you define counter-steering as requiring a 'single' input?
-- Why do you refer to a continuous application of torque over an extended period of time as a 'single' input?

- Why do you believe that the combined CG moves right of the contact patches when the handlebars are rotated right?
-- Why do you believe this phenomenon is significant at anything beyond trivial speeds and steering angles?
-- If the opposite premise was true (rotating the bars right causes the CG to be displaced left relative to the contact patches) would direct-steering be possible? If no what term would you use to describe the low-speed turning process?

- What do you believe happens exactly at the point between direct- and counter-steering?
-- Direct- and counter-steering are mutually exclusive and the bars can only be rotated two directions, therefore by deduction the bike cannot be steered at that point. Correct?



There are more factors operating in motor cycle steering than can be handled by any computer/mathematical model I've seen. Definitely more than any 'mental model' can handle.:)

Fortunately, at speeds above 6 - 10 mph, a very few of these factors overwhelm all the others and meaningful models can be used.

Below that speed, not only are most of the factors significant, but various combinations of control inputs are available to cause different various factors to become the determining ones.

Thus there are actually quite a few 'techniques' that are useful in low speed steering of a motorcycle. Some of them depend strongly on characteristics of steering geometry, or even of a particular model of motorcycle.

New riders have a geat deal of new skills to learn (remember the purpose of this site is primarily to give reliable and useful info to new riders), and James has settled on a technique of low speed steering that is:
a) Relatively easy to learn, particularly for new riders.
b) Universally applicable to all motorcycles and riders.
c) Safe and simple.
d) Supported by (necessarily) simplified models that are relatively easy to understand, accurate and reliable (provided the specified technique is used), and easy to teach/coach.

There are other techniques, experienced riders may develop them themselves, or advanced classes may teach them when appropriate.

I, myself, was taught a different (additional) technique by police instructors on an advanced course in England in the '60s. I still use it today, in some circumstances. I still use the technique James advises in most slow speed riding.

The real answer to most of the questions in your last post is to remind you that 'we are using a simplified model of low speed steering that assumes a specific technique', it works well enough, but it's still a simplified model based on an assumption.
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BennyRayRiddle
Starting Member
7 Posts


Beverly Hills, CA
USA

(None)

Posted - 09/08/2012 :  7:56 PM
The second sentence of my first post was "Why does the definition of counter-steering require the condition of a single steering input?" The second sentence of my fourth post was "...Why do you define counter-steering as requiring a 'single' input?" My primary intent in starting this thread was to understand the reasoning behind Mr. Davis' definition and I still do not understand because no explanation has been provided. Instead this thread has been sidetracked into a discussion of low-speed handling. I do not mind continuing that discussion in this thread, but I suspect it will be hampered by inconsistencies in our definitions more than physics disagreements.



I, of course, also have a simplified mental model of cycle behavior. That model generates a single steering technique, let's call it "adslkfjn", that is:
1) Simple to explain
2) Simple to execute
3) Safe
4) Universally applicable to all single-track vehicles
5) Consistent with my bicycling experience (road, mountain, and rollers) and motorcycling experience (street)
6) Applicable at any finite non-negative speed
7) Contrary to Mr. Davis' declaration that only "direct-steering" works at low speeds
8) Lacking an impossible cross-over point; it just has a smooth transition between low and high speeds

kdlfjbgd is a two-step process which, due to variable steering feedback, can be (poorly) described as requiring two rider inputs at low speed and a single input above low speed. I consider sdfldfgh equal to "counter-steering works at all speeds," but that is contradictory to Mr. Davis' definition. If I was a paranoid sort, I would declare that Mr. Davis added the single input requirement not because it was a necessary component of the definition, but to prevent me from referring to dklfjh as counter-steering since I would therefore be wrong by definition. (I am not a paranoid sort, which is why I cannot figure out Mr. Davis' reasoning.)

As I noted above Mr. Davis' mental model contradicts mine at low speeds. In fact my model indicates that direct-steering at all speeds will always crash the cycle PDQ unless the rider subconsciously executes slckdfjvb instead. Thus, a belief in direct-steering is unsafe, retards skill development, and makes teaching/coaching more difficult.


It currently appears to me that the fundamental difference between Mr. Davis' model and my own is how the CG of the steering assembly behaves relative to the contact patches when the handlebars are rotated. Fitting my model to Mr. Davis' contention requires a freakish distribution of mass in the steering assembly. If I instead distort my model to assume that the contact patches remain inline with the frame and the frame remains vertical when the bars are rotated the effect is rapidly overwhelmed by the sideways motion of the front wheel at non-trivial speeds. Of course the frame won't remain vertical, conservation of momentum requires that if the steering CG is displaced left then the frame CG is displaced right resulting in zero motorcycle lean angle and a frame lean angle opposing the rotation of the bars.

Even if nobody ends up agreeing I would like to understand Mr. Davis' model and the way it explains how the combined CG ends up left of the contact patches when the bars are rotated left.



quote:
we are using a simplified model of low speed steering that assumes a specific technique
Was that a mis-statement? That method strikes me as an excellent way to generate an inaccurate and unnecessarily complicated model; you should generate the model and then derive your steering technique(s) instead.
quote:
Below that speed, not only are most of the factors significant, but various combinations of control inputs are available to cause different various factors to become the determining ones.
Thus there are actually quite a few 'techniques' that are useful in low speed steering of a motorcycle. Some of them depend strongly on characteristics of steering geometry, or even of a particular model of motorcycle.
...
I, myself, was taught a different (additional) technique by police instructors on an advanced course in England in the '60s.
I'm all ears.
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James R. Davis
Male Administrator
17284 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 09/08/2012 :  8:54 PM Follow poster on Twitter  Join poster on Facebook as Friend  
We are all used to shorthand descriptions of reality that simplify understanding.

I suggest that you have actually used the word 'cold' before. In fact, there is only absolutely zero and some measurement of heat, but there is no measurement of cold. Yet you have used the word 'cold' before, no?

At speeds greater than about 10 MPH, you can press forward on a grip and the bike will (every time) change its direction of travel towards that grip. (Nobody disputes that for a brief interval the bike will actually move in the opposite direction.) That's counter-steering and is a single steering input.

At five MPH, however, you can press forward on that same grip and the bike's direction of travel will be toward the other grip. That's a single steering input and it's called direct-steering.

Now, if you want to argue that if you press forward on one of the grips, then follow it with pressing forward on the other grip in order to move toward that other grip, that is a single steering input and, thus, proof that counter-steering is effective at 5 MPH, feel free to do so. Usually, however, when we talk about more than one event we add an 's' as a suffix to that event.

If the front wheel was mounted with a rake angle of zero, then 100% of your steering input is translated into a direction change (where the front wheel points), but if the rake angle is greater than zero, then some portion of that steering input is translated into a lean of the wheel while the rest of it is translated into a direction change.

Not only that, but the wheelbase lengthens as the contact patches get farther apart from each other and the front-end of the motorcycle lowers. A combination of these three effects and the fact that the front wheel's contact patch is the pivot point for the front tire's new lean angle (not the axle) results in an overhang of the CG.

Again, if the rake angle was zero degrees, then there would be as much mass shifted to the left as there would be to the right when you applied a steering input, but when you lean a wheel (have a rake angle greater than zero when you apply a steering input), more mass shifts in the direction of lean and less mass is left in the other direction. I assume your bike has a rake angle greater than zero degrees?

KISS
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The Meromorph
Male Moderator
834 Posts
[Mentor]


White House, TN
USA

BMW

R1100RT

Posted - 09/08/2012 :  10:39 PM
quote:
Originally posted by BennyRayRiddle
quote:
Below that speed, not only are most of the factors significant, but various combinations of control inputs are available to cause different various factors to become the determining ones.
Thus there are actually quite a few 'techniques' that are useful in low speed steering of a motorcycle. Some of them depend strongly on characteristics of steering geometry, or even of a particular model of motorcycle.
...
I, myself, was taught a different (additional) technique by police instructors on an advanced course in England in the '60s.
I'm all ears.


I propose that you or I start a new thread to discuss this and we all can enjoy the discussion that ensues. I'll need some little time to organize my thoughts before starting the thread so anyone should feel free to start it.
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The Meromorph
Male Moderator
834 Posts
[Mentor]


White House, TN
USA

BMW

R1100RT

Posted - 09/08/2012 :  10:40 PM
quote:
Originally posted by BennyRayRiddle



quote:
we are using a simplified model of low speed steering that assumes a specific technique
Was that a mis-statement? That method strikes me as an excellent way to generate an inaccurate and unnecessarily complicated model; you should generate the model and then derive your steering technique(s) instead.


As the old saying goes:
'In theory, theory and practice are the same.
In practice, they are not. '
In low speed steering there really are many more forces and conditions that have a significant effect on steering, e.g. steering angle, tire profile, rake, trail, tire profile (camber thrust), lean angle of bike, of rider, of COG, shape of contact patches, size of contact patches, caster effect, etc. It's even true that they interact with each other. Complexly.
We no more model these forces to steer than we solve differential equations to catch a ball. The object of training is to 'internalize' the learned skill of steering. We require a simplified model to get there.
The best way to get an effective simplified model is to eliminate, through the techniques we teach/train, as many of the variables as we can. The 'direct steering at low speeds' technique does this. The transition to 'counter-steering' is handled 'internally' by our learned skills and seems to be acquired seamlessly without specific training.
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BennyRayRiddle
Starting Member
7 Posts


Beverly Hills, CA
USA

(None)


Peer Review: Blocked

Posted - 09/19/2012 :  2:33 AM
quote:
The second sentence of my first post was "Why does the definition of counter-steering require the condition of a single steering input?" The second sentence of my fourth post was "...Why do you define counter-steering as requiring a 'single' input?" My primary intent in starting this thread was to understand the reasoning behind Mr. Davis' definition and I still do not understand because no explanation has been provided.
- What is it you do not understand about my inquiry?
- Is this a secret reserved for level 6 initiates?
- Are you refusing to answer?
- Do you somehow believe you already addressed this?




quote:
We are all used to shorthand descriptions of reality that simplify understanding.
What does this refer to?
quote:
I suggest that you have actually used the word 'cold' before. In fact, there is only absolutely zero and some measurement of heat, but there is no measurement of cold. Yet you have used the word 'cold' before, no?
If you want to be pedantic, you can say there's no such thing as cold, but I have no idea what your point is.
quote:
Now, if you want to argue that if you press forward on one of the grips, then follow it with pressing forward on the other grip in order to move toward that other grip, that is a single steering input and, thus, proof that counter-steering is effective at 5 MPH, feel free to do so. Usually, however, when we talk about more than one event we add an 's' as a suffix to that event.
I blatantly and explicitly stated that lkzxcvj "can be (poorly) described as requiring TWO (2) rider inputs at low speed" (emphasis added.)
quote:
At speeds greater than about 10 MPH, you can press forward on a grip and the bike will (every time) change its direction of travel towards that grip. (Nobody disputes that for a brief interval the bike will actually move in the opposite direction.) That's counter-steering and is a single steering input.
If there is a brief movement in the opposite direction wouldn't that be a direct-steer left immediately followed by a direct-steer right (or vice-versa)? Or are you admitting that counter-steering is a pair of bar movements? If so, why do you care whether the pair of bar movements are caused by 'one' or 'two' or 'twelve' inputs?
quote:
If the front wheel was mounted with a rake angle of zero...
All but one effect I was already predicting correctly and the one effect I had partially wrong I had to discover my own error before being able to figure out the likely intent of your attempted explanation.

When the steering assembly is rotated clockwise everything "in front" of the steering axis moves right and everything "behind" the steering axis moves left. There are other factors at play, but the contact patch is behind the steering axis so its' initial movement is left.

So, I was correct, but only at extreme bar angles and in geometries with negative trail. If you hold the frame vertical and rotate the bars the front contact patch will, relative to the mid-line of the frame, curve "away" from the bar rotation and forward, reach a maximum sideways deflection, then curve back towards the frame, cross the mid-line, and at 90 degrees ends at a distance equal to the offset in the triple tree on the "same" side as the bar rotation. The answer to the question "What happens at the cross-over speed between direct- and counter-steering?" is that there is no such cross-over speed because the mechanics cannot be explained in such a simplistic manner. The cycle's reactions depend on the geometry, the initial and final bar positions, how fast the bar is rotated, the forward speed, and other factors.

Armed with a new theory I paid extra attention to my low speed maneuvering while riding. On my bike I found that I didn't regularly notice possible direct-steering until I got down into the 1.x mph range and I could not be certain of my initial lean angle and other factors. When attempting to track stand I realized that my speed was too variable to make any honest determinations. I also use a lot of bar angle and that is potentially interesting in regards to how the CG shifts at larger bar angles. On the motorbike I found that below first gear idle my speed and balance were also too unsteady to make any honest determinations. While idling in first gear I found I could either direct- or counter-steer (I am using those two terms without any artificial 'single input' restriction.) Direct-steering I often perceived as a small initial input, followed by a delay to let the lean develop, and then a larger input to catch the lean at the desired angle or as a smooth input followed by a little extra at the end to arrest the lean angle change and hold the line. I could counter-steer by using a larger and quicker bar rotation so that the CG shift was rapidly overwhelmed by the tracking of the front wheel, inducing an opposing lean, followed by rotating the bars into the turn and catching the lean, just like counter-steering at "counter-steering speeds", but with minimal steering feedback. As I quoted earlier, you stated that "for a brief interval the bike will actually move in the opposite direction" when describing counter-steering so there are no reasonable grounds to deny that I was counter-steering. I couldn't direct-steer out of a turn, I had to counter-steer--rotate the bars farther into the turn and then straighten them. As I accelerated from idle I found that direct-steering rapidly became less effective, only allowing lazier and lazier turns, and by 10mph direct-steering effects are unnoticeable.
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