| Member |
 Discussion Topic  |
|
charlie3
 Standard Member
123 Posts
Port Austin, Michigan
USA
Kawasaki
KLX300R 2004
|
 Posted - 09/21/2008 : 11:05 AM
|
Mr. Davis,
I agree that if more of my upper body weight is leaning into the turn then the bike needs to lean less. It does not follow that there is no gain from leaning the bike differently from the upper body.
I find it easier to maneuver the bike in many situations when I counter balance. Perhaps after more hours of practice I'll find I can maneuver just as effectively even when my body weight is kept in a fixed position as though my bottomm was rivited to the seat and my spine was rigid. So far doing that is beyond my ability.
|
 |
|
|
James R. Davis
Administrator
14909 Posts
[Mentor]
Houston, TX
USA
Honda
GoldWing 1500
|
Posted - 09/21/2008 : 2:59 PM
|
Again, 'couter-balancing' causes the bike to lean MORE, not less, than it would without such body weight shifting.
If you believe that there is some kind of gain from doing that I would be very interested in hearing what that gain is and how it derives. |
|
|
|
charlie3
Standard Member
123 Posts
Port Austin, Michigan
USA
Kawasaki
KLX300R 2004
|
Posted - 09/21/2008 : 10:47 PM
|
I took Mr. Davis comments to heart and went to my parking lot and did some experiments.
Experiment #1. I made various random turns around the parking lot, large and small, and payed attention to how my upper body moved reletive to the bike. When I'm doing what comes natural my mid section and spine are constantly flexing one way or another such that my upper body always seems to lean a bit differently from the bike. When I tried to attach myself to the bike as though I was bolted on, knees, hips and back as rigid as I could hold them, maneuvering the bike was more difficult. Anyone can try this and see what I'm describing.
A broad definition of counter balancing could be moving the upper body different from the motion of the bike to improve control. If that definition is reasonable then everybody "counter balances" all the time their bikes are in motion.
Experiment #2. I did some 18' diameter figure 8s but leaned my upper body hard to the inside of the turn instead of "counter balancing" to the outside. I could still follow the circular paths but needed a slower speed. The bike needed to be more vertical and staying on the path required larger steering adjustments with the handle bar. My perception is there is a sweet spot in the lean angle of the bike where it's easiest to use the steering bar in a turn. In most of my turns it seems easier to maintain the turn when the bike is leaning farther than Mr. Davis says is required. The same might apply at high speed but with counter balancing on the opposite side of the bike to reduce the lean angle to a point closer to optimum steering sensitivity.
Experiment #3. I did a straight line maneuver where I leaned my upper body far to one side until the bike had to lean a couple of degrees to the opposite side for stability, then I maintained a straight path with the steering bar. Whenever I loosened my hold on the grips enough to see where the bike wanted to go it always turned in the direction IT was leaning, NOT in the direction I was leaning. (Try it on your own motorcycle.) I wonder how front fork geometry might influence this. This result seems to support the idea that pushing on a peg doesn't lean the bike, it shifts the rider's upper body weight to the outside of the turn--counter balancing.
Thanks for taking time to read this. I'm participating in this discussion to learn things that improve my bike handling skills, not win debating points. |
|
|
|
James R. Davis
Administrator
14909 Posts
[Mentor]
Houston, TX
USA
Honda
GoldWing 1500
|
Posted - 09/22/2008 : 7:18 AM
|
quote:
Experiment #1. I made various random turns around the parking lot, large and small, and payed attention to how my upper body moved relative to the bike. When I'm doing what comes natural my mid section and spine are constantly flexing one way or another such that my upper body always seems to lean a bit differently from the bike. When I tried to attach myself to the bike as though I was bolted on, knees, hips and back as rigid as I could hold them, maneuvering the bike was more difficult. Anyone can try this and see what I'm describing.
I'll say it again ... there is no need to counter-balance at slow speeds, but as you have found out, some people find it to be helpful for them. Your first experiment demonstrates that *you* 'constantly flex'. My experience is that staying in-line with my bike's frame (acting like a sack of potatoes) is natural for *me*.
quote:
A broad definition of counter balancing could be moving the upper body different from the motion of the bike to improve control. If that definition is reasonable then everybody "counter balances" all the time their bikes are in motion.
Such a definition would be non-rigorous and would deny the essence of what 'counter-balance' implies - that you counter-balance (i.e., lean away from the turn.) To add that doing so 'improves control' is gratuitous and not supported by any evidence that I know of. What it does do, for some, is increase a rider's comfort and reduces some concerns about falling that an unfamiliar lean attitude causes in some.
Experiment 2 included:
quote:
Experiment #2. I did some 18' diameter figure 8s but leaned my upper body hard to the inside of the turn instead of "counter balancing" to the outside. I could still follow the circular paths but needed a slower speed.
Isn't this directly contrary to established fact? If you maintained the 18' diameter as you rode, then the exact same speed as you had before your leaning-off (into the turn) would have resulted in the exact same lean angle of your combined body and motorcycle. You certainly didn't 'need' a slower speed just because your bike frame was more vertical. Indeed, it is precisely because your bike frame was more vertical with you leaning-off that you could have attained a higher speed (which would, of course, cause the lean angle to increase again) without dragging a peg in the processes. That is THE reason racers do so.
Experiment 3 included:
quote:
Experiment #3. I did a straight line maneuver where I leaned my upper body far to one side until the bike had to lean a couple of degrees to the opposite side for stability, then I maintained a straight path with the steering bar. Whenever I loosened my hold on the grips enough to see where the bike wanted to go it always turned in the direction IT was leaning, NOT in the direction I was leaning.
That, too, is perfectly rational and understandable. When the bike is leaning the front-end attempts to allow gravity to lower that front-end as it's contact patch moves forward and the steering stem rotates in the direction of the lean. Sitting at a dead stop and leaning the bike to one side or the other will find that the front wheel will point in the direction of the lean.
So it would appear that you equate gravity assist with control whereas control, in my book, means 'causing the bike to do what you intend it to do', and nothing more or less than that. Gravity can assist greatly in low-siding a bike but that is hardly controlling that bike unless you want it to lay on its side.
Again, I am not challenging your method of dealing with low or high speed turning as it works for you. My only challenge is with the idea that counter-balancing is in some way necessary in order to control your motorcycle. It is not.
I assume that you will agree that if you can drag a peg while doing a turn and at the same time 'counter-balancing' that you cannot make that turn at any higher speed. And that if you can drag a peg while making that same turn while at the same time NOT 'counter-balancing', you will be moving faster than when you were 'counter-balancing'. If so, is this really an argument? |
|
|
rioguy
Ex-Member
|
Posted - 09/22/2008 : 8:10 AM
|
I'm with James in that I don't consciously shift my weight at slow speeds. However, when I was new, I did lean to the outside of the turn.
Perhaps it is similar to standing at attention and trying to shift your center of gravity forward by leaning forward. You don't go too far before you fall. Yet, by bowing forward a people can touch their toes.
In the first case, the weight gets shifted forward on the feet. In the second case it shifts back towards the heels.
In both cases, the CG must stay over the feet or one would fall.
Maybe there is a similar reaction on a bike that makes leaning away from a turn more comfortable for newer riders.
I don't have a side in this discussion as I've noted there is a wide variety of techniques which all seem to work reasonably well for everyday riding. |
|
|
|
Andrew Dressel
Standard Member
153 Posts
Milwaukee, WI
USA
Moto Guzzi
California Special
|
Posted - 09/22/2008 : 9:36 AM
|
quote:
Originally posted by derangedhermit
quote:
Originally posted by Andrew Dressel
quote:
Originally posted by Cash Anthony
I find that it helps me quite a bit to slide forward on the tank (though still upright) when I'm doing slow speed PLP turns.
It definitely helps to move the combined center of mass forward when trying to maintain balance at low speed. Obviously, the front end responds to steering inputs more quickly than the rear.
I don't understand what that last sentence means. I suggest that by putting more weight on the front, you are decreasing the rake and trail, thus making the steering more responsive. Make sense?
You are probably correct that moving the center of mass forward changes the front end geometry, but I doubt you can detect the difference, especially at low speed.
Instead, what I'm referring to is the different tracks the front and rear wheels take. Steer the front wheel 10° to the right and roll forward one foot and the front wheel has moved about 2 inches to the right while the rear wheel has moved to the right only a tiny fraction of that. If the center of mass is over the front wheel and starts to lean, you can pretty quickly and easily get the contact patch back under it. If the center of mass is over the rear wheel and starts to lean, you have to move the front wheel quite a bit farther to produce the equivalent motion in the rear wheel. In reality, of course, the center of mass is somewhere between these two extremes, but the further forward it is, the easier it is to get the line between the contact patches back under it. |
|
|
|
charlie3
Standard Member
123 Posts
Port Austin, Michigan
USA
Kawasaki
KLX300R 2004
|
Posted - 09/22/2008 : 10:13 AM
|
Thanks for commenting.
The handling skills I admire most are demonstrated by the Japanese gymkhana riders. Observe the use of counter balancing by this rider. http://www.youtube.com/watch?v=gTO2s7wyrFs
In some of the slower speed, tighter turns, counter balancing to the outside is clearly visible. In faster wider turns he moves his upper body more to the inside of the turn similar to what track racers do. In fast weaves he lets the bike roll from side to side while his upper body moves less--another example of counter balancing.
If this world class rider, at his level of skill, uses counter balancing I don't think it can be dismissed as a beginner crutch.
Thanks again |
|
|
|
James R. Davis
Administrator
14909 Posts
[Mentor]
Houston, TX
USA
Honda
GoldWing 1500
|
Posted - 09/22/2008 : 10:22 AM
|
For over a dozen years we, with some regularity, hear 'Yeah, but ...' from those who have made up their minds and who will not actually 'hear' any other side of a discussion.
quote:
I assume that you will agree that if you can drag a peg while doing a turn and at the same time 'counter-balancing' that you cannot make that turn at any higher speed. And that if you can drag a peg while making that same turn while at the same time NOT 'counter-balancing', you will be moving faster than when you were 'counter-balancing'.
Maybe I'm wrong and you don't agree with the above. Do you or not?
I'd rather not simply waste time 'commenting' when the agenda has nothing to do with facts. |
|
|
|
The Meromorph
Advanced Member
717 Posts
[Mentor]
White House, TN
USA
BMW
R1100R
|
Posted - 09/22/2008 : 3:08 PM
|
quote:
Originally posted by James R. Davis
Again, 'counterbalancing' causes the bike to lean MORE, not less, than it would without such body weight shifting.
If you believe that there is some kind of gain from doing that I would be very interested in hearing what that gain is and how it derives.
Well, James, since you asked... 
The advantage to be gained by 'counter balancing' at low speed (particularly for a U-turn) would be:
There is a 'self steering' effect of the tire profile when leaned over that increases with the angle of lean of the wheel. I am referring to the fact that you are actually rolling on a conic section that wants to turn in the direction you are leaning (imagine rolling a Styrofoam cup on its side). And that conic section is more exaggerated, the greater the angle of lean.
Given that the speed and the turn radius dictate the 'angle of lean' of the bike/rider unit, then if you want a greater 'angle of lean' for the wheels/tires, than is dictated by your turn radius and speed, than you must increase the 'angle of lean of the bike portion while counterbalancing the rider portion to generate the same original 'angle of lean' for the bike/rider as a whole.
What it buys you, in other words, is a significant increase in the contribution of the leaning tire's profile to the turn, which, in the normally very slow and constrained, environment of a U-turn is helpful. The effect is, of course, soon swamped by the other forces at any speed other than 'dead slow'. |
|
|
|
James R. Davis
Administrator
14909 Posts
[Mentor]
Houston, TX
USA
Honda
GoldWing 1500
|
Posted - 09/22/2008 : 4:16 PM
|
Is the argument you just put forth *really* designed to support the position that 'counter-balancing' is necessary in a slow-speed turn? Or that 'counter-balancing' allows you to ride a given turn faster than sitting in-line? Or that it enhances 'control'?
I quite well understand the dynamics of the front-end and how steering works. The question I think you answered is 'What is the advantage gained by counter-balancing and how is it derived?' What I believe you described is that when the front tire is leaned more into a turn of given radius it takes less pressure on the grips to maintain it. That, I suppose, would be an 'advantage' if your handlebar was three inches in length instead of three feet. I know of nobody who needs or can appreciate such assistance in turning their handlebar. Maybe I'm just not seeing it clearly, or that 'advantage' means something different to me than it does to you.
Nevertheless, thank you for adding your insight on the matter. Some people may not have understood that dynamic.
|
|
|
|
scottrnelson
Advanced Member
5247 Posts
[Mentor]
Pleasanton, CA
USA
KTM
990 Adv, ST2, XR650L
|
Posted - 09/22/2008 : 4:49 PM
|
quote:
Originally posted by The Meromorph
What it buys you, in other words, is a significant increase in the contribution of the leaning tire's profile to the turn, which, in the normally very slow and constrained, environment of a U-turn is helpful. The effect is, of course, soon swamped by the other forces at any speed other than 'dead slow'.
My own experience is that the conical shape of the tire while leaned over makes an insignificant contribution to turning under all circumstances.
Do you have anything more than theory to back up the "significant increase" argument? |
|
|
rioguy
Ex-Member
|
Posted - 09/22/2008 : 5:41 PM
|
Here is a video with 3 riders in a figure 8 together.
http://www.youtube.com/watch?v=gKhqxizVGHY
The rider in the yellow vest appears to stay erect. The rider in the gray shirt appears to lean into the turns and shift his butt a bit INTO the turn. The rider in the black shirt appears to lean to the outside of the turn.
In this next video, the rider appears to shift his butt a bit INTO the turn also. (He is the same rider as the one in the gray shirt in the first video.)
http://www.youtube.com/watch?v=ATfgPs7Glt8
For myself, I've found that leaning into a turn as I transition from one direction to the next seems to make the transition faster if I lean right when I'm vertical, but it was too hard to control, so I stopped doing it.
I think Charlie3 is searching for the next level of excellence. Unfortunately, there aren't many people who have reached his level in the parking lot. Even fewer talk about it. And of that group, even fewer can accurately describe what we do as we don't really know. It's in an area of the unconscious mind.
If one is talking about what I call "Survival PLP" which is doing everything good enough for a 20 foot U turn or circle, or merely to get safely around a gas station parking lot, the techniques are much less important than for a person who is trying to do difficult patterns with tight dimensions and "impossible" turns.
|
|
|
|
The Meromorph
Advanced Member
717 Posts
[Mentor]
White House, TN
USA
BMW
R1100R
|
Posted - 09/22/2008 : 9:02 PM
|
quote:
Originally posted by James R. Davis
Is the argument you just put forth *really* designed to support the position that 'counter-balancing' is necessary in a slow-speed turn? Or that 'counter-balancing' allows you to ride a given turn faster than sitting in-line? Or that it enhances 'control'?
I quite well understand the dynamics of the front-end and how steering works. The question I think you answered is 'What is the advantage gained by counter-balancing and how is it derived?' What I believe you described is that when the front tire is leaned more into a turn of given radius it takes less pressure on the grips to maintain it. That, I suppose, would be an 'advantage' if your handlebar was three inches in length instead of three feet. I know of nobody who needs or can appreciate such assistance in turning their handlebar. Maybe I'm just not seeing it clearly, or that 'advantage' means something different to me than it does to you.
Nevertheless, thank you for adding your insight on the matter. Some people may not have understood that dynamic.
No, I'm not 'arguing' any of those things. You actually did simply ask "If you believe that there is some kind of gain from doing that I would be very interested in hearing what that gain is and how it derives." And that is, indeed, as you said, what I was answering.
As to why one would do it - Well it gives one an 'alternative control input' into a very slow speed turn, and some people find it an easier technique to learn and use, for very slow speed turns, than the 'classic' technique. I'm one of those people. I was taught the technique on my advanced training in England back in the 60's, by one of the instructors because he thought I'd find it easier on the (comparatively) much larger bike I was riding than the other trainees (I was on a fully dressed Triumph 500 and they were on 125's and 250's).
I emphasise again that the technique only works at very slow speeds, and only works significantly if your tire tread cross section is close to a half-circle , rather than a shorter arc of a circle. I had in fact chosen my recently replaced tires of the half-circle profile(Dunlop's), over the prior 1/4 circle tread profile tires(Avon's), because I liked the handling much better that way.
So the technique is of limited use, only works well for some tires, and some people, and I'm not suggesting it's the best way. I'm only saying that it may be a useful technique for some people, and is, in fact, based on the physics, but in a very limited set of circumstances.
It's the sort of thing IMHO an instructor might choose to teach a particular learner having a specific difficulty, not a generally recommended technique.
Edit:
I should perhaps add that I do it both ways, these days, and from the comments of the bystanders (it's usually when parking as I get to work, and the 'smoker's group' don't cut anyone any slack), then doing the 'right way' looks smooth and professional, doing it the 'other way' - not so much.  |
Edited by - The Meromorph on 09/22/2008 9:11 PM |
|
|
|
Robsalvv
Junior Member
42 Posts
Melbourne, Vic
Australia
Kawasaki
ZX9R
|
Posted - 09/24/2008 : 9:15 PM
|
Just harking back to the OP regarding hands off steering. Tony Foale addresses hands off steering in http://www.tonyfoale.com/Articles/B.../BALANCE.htm and in chapter four of his chassis design book. Basically it relates to introducing a lean on the frame by pushing against the machine with the inertia of your body.
Have a crack at this heavily physicced report on countersteering and no-hands steering if you can stomach equations.
http://socrates.berkeley.edu/~fajan...rBikeAJP.PDF
I often give my back a break by sitting up no hands, coasting forward, and steering around gentle curves by application of weight and body movements/hip flicks. Used to do it on my treadly rolling downhill without any problems either.
Cheers
Rob |
|
|
|
Andrew Dressel
Standard Member
153 Posts
Milwaukee, WI
USA
Moto Guzzi
California Special
|
Posted - 09/30/2008 : 8:37 PM
|
quote:
Originally posted by derangedhermit
quote:
Originally posted by derangedhermit
One sequence of thoughts I have is taken from Tip 173, where, in a turn, a line drawn through the front axle always points to the center of the turn.
I think the question can be summarized as: Is it the bike's lean angle (that arrow through the axle) that is related to speed and turn radius or is it the combined lean angle of bike and rider?
Anyone have a view on this? If tip 173's "front axle" description is correct on the face of it (the front axle is on the perimeter of a cone with the tip of the cone pointed to by the front axle), then a rider who lays the bike into the turn turns in a shorter radius than a rider who doesn't.
I would say that this cannot be strictly true. If it were, the guy keeping his bike almost upright and moving forward slowly could only have a very large turning radius, no matter how much he turned the front wheel.
Cossalter says the center of the turn, from which radius would be measured, is about where the axis of the front axle and the axis of the rear axle intersect, although the exact location is modified by the roll (lean) angle. This also assumes no side-slip in either tire.
He eventually gives an approximate formula (corrected since original post) of R = (b/a)*cos(c)/cos(d) where a = steer angle, b = wheelbase, c = roll angle, and d = caster angle (measured from the vertical). |
Edited by - Andrew Dressel on 10/01/2008 6:47 AM |
|
|
|
James R. Davis
Administrator
14909 Posts
[Mentor]
Houston, TX
USA
Honda
GoldWing 1500
|
Posted - 09/30/2008 : 9:16 PM
|
LOL
While that formula no doubt is more accurate than my rather simplistic description, it says the same thing about the effect of lean.
quote:
Anyone have a view on this? If tip 173's "front axle" description is correct on the face of it (the front axle is on the perimeter of a cone with the tip of the cone pointed to by the front axle), then a rider who lays the bike into the turn turns in a shorter radius than a rider who doesn't.
That observation is simply not accurate. A leaning bike CAN carve a shorter radius than one that is not leaning, but whether the bike is leaning or not the radius described by the turn is the one painted on the ground by the tires as the bike traverses the turn.
If a rider carves the same radius turn over several iterations and the lean angle is different for each such iteration, all that means is that the rider drove at different speeds.
|
|
|
|
Andrew Dressel
Standard Member
153 Posts
Milwaukee, WI
USA
Moto Guzzi
California Special
|
Posted - 10/01/2008 : 6:56 AM
|
First, my abject apologies for mistyping the formula last night. Cossalter presents it inverted to give curvature, and I wanted to show radius. I neglected to invert the steer angle.
quote:
Originally posted by James R. Davis
LOL
While that formula no doubt is more accurate than my rather simplistic description, it says the same thing about the effect of lean.
That observation is simply not accurate. A leaning bike CAN carve a shorter radius than one that is not leaning, but whether the bike is leaning or not the radius described by the turn is the one painted on the ground by the tires as the bike traverses the turn.
If a rider carves the same radius turn over several iterations and the lean angle is different for each such iteration, all that means is that the rider drove at different speeds.
I agree that it says that radius decreases as lean angle increases, but I disagree with the cone analogy. Radius is inversely proportional to steer angle, but only proportional to the cosine of the lean angle. A leaned bike steered straight won't turn at all, but a completely upright bike steered at 45 degrees will turn a lot. Where the axis of the front wheel axle touches the ground isn't a good predictor of turn radius. |
|
|
|
James R. Davis
Administrator
14909 Posts
[Mentor]
Houston, TX
USA
Honda
GoldWing 1500
|
Posted - 10/01/2008 : 9:04 AM
|
LOL
My guess is that the original post suggested as simple a fundamental concept as did my safety article - that a leaned over bike CAN carve a smaller radius circle than one that remains vertical. I don't believe that poster meant to suggest that it was not accurate to the tenth decimal place.
quote:
... then a rider who lays the bike into the turn turns in a shorter radius than a rider who doesn't.
Despite my original response to that message, there is certainly truth to that observation. That is, even if a leaned over bike and a vertical one track the EXACT SAME path on the ground while they ride in a circle, the leaned over bike actually does carve a smaller radius turn because it is the Center of Gravity that determines that radius, not the contact patch and the leaned over bike's CG *IS* closer to the center of the circle.
The referenced safety article properly demonstrates a concept that is true - that a leaned over bike carves a circular path with a center that can well be subterranean, and that the radius of that curve is smaller (at ground level) than it would be if the bike were vertically oriented. It was a concept presentation not a rigorously correct mathematical proof. |
|
|
|
Andrew Dressel
Standard Member
153 Posts
Milwaukee, WI
USA
Moto Guzzi
California Special
|
Posted - 10/01/2008 : 2:39 PM
|
quote:
Originally posted by derangedhermit
Since you seem on top of the formula now, maybe you will want to run some numbers. If you do, please share the results.
I'm trying, but it is turning out trickier than I thought.
First, I am having a hard time reproducing the graph Cossalter shows. I suspect he used a slightly different fomula to produce it than the one he provides. I can get pretty close, though.
Second, I also don't understand the method described in tip 173. The original radius of the turn appears to be selected arbitrarily to be 30 feet. Then some geometry is applied to modify that initial radius. I don't see where the 'cone' comes into it or how the initial radius is chosen.
Then, the diagram in tip 173 merely shows the relationship between lean angle, forward speed, and turn radius based on the need to balance. That can't be all this is about right?
Cossalter's equations show how for a given steer angle, you can modify the turn radius by changing the lean angle (independent of forward speed). Of course, you then have to modify the forward speed to maintain balance with the new lean angle and turn radius.
I thought tip 173 showed something similar, how to calculate the turn radius based just on the lean angle, but I don't think that is the case.
In case I give the impression that I don't realize the strict kinetic relationship between lean angle, forward speed, and turn radius, that is not the case. Instead, I'm looking for the purely kinematic relationship between steer angle, lean angle, caster angle, wheelbase, and wheel radius. |
|
|
|
scottrnelson
Advanced Member
5247 Posts
[Mentor]
Pleasanton, CA
USA
KTM
990 Adv, ST2, XR650L
|
|
|
Discussion Topic |
|
|
|
|
Most Recent Posts
|
Activity History
|
Safety Tips
weighting the pegs