(Counter) Steering

[BitScribbler]

It's well understood that at "parking lot" speed you turn the bars left to go left, and right to go right.

 

It's also well understood that over a "certain" speed you turn the bars left to go right, and right to go left (countersteering).

 

This implies that there must be one particular speed (varying by motorcycle, rider, conditions of course) where turning the bars will have no effect at all...? Or perhaps you'll go in both directions at once...?

[hngininthr]

I think countersteering works at all speeds down to the "barely wobbling almost unbalanced" speed. You are not "turning right to go left", you are applying some pressure to the left handlebar (which if the bike were stationary would turn the wheel to the right) which because of "precession" a gyroscopic phenomonon, actually makes the front wheel lean left and thus initiates a left turn. The wheel actually turns left.

 

If the wheel is spinning so slowly that there is negligible gyroscopic effect, then countersteering doesnt occur.

 

Someone else probably has a better explanation, or will perhaps say I am full of male bovine fecal matter.

[Miriam]

Actually that’s all wrong.

 

Counter steering means to push on the left handlebar to go left and push on the right handlebar to go right. In effect initiating a turn by steering the bike away from the direction you want it to lean in. This can be done either in the parking lot, to initiate a turn on a curvy road, and, obviously, to initiate doing a hairpin turn.

[BitScribbler]

Actually that’s all wrong.

 

Counter steering means to push on the left handlebar to go left and push on the right handlebar to go right

 

Actually that's right! A push on the left bar will turn the bars to the right, exactly as I have described...

[BobFV1]

Actually that’s all wrong.

 

Counter steering means to push on the left handlebar to go left and push on the right handlebar to go right. In effect initiating a turn by steering the bike away from the direction you want it to lean in. This can be done either in the parking lot, to initiate a turn on a curvy road, and, obviously, to initiate doing a hairpin turn.

 

Countersteering can only be done in a parking lot if you are going fast enough - depends if you are driving around the perimeter of the parking lot at 20 mph (countersteering) or turning the bike around within two parking spaces while feathering the clutch (counterweighting).

[BitScribbler]

Sorry, I didn't mean to start a discussion on counter-steering per se, that's been done to death many times I'm sure. i was just making a tongue-in-cheek observation about that strange speed at which steering stops and counter-steering starts.

[Shaun]

"Or perhaps you'll go in both directions at once...?"

 

Not quite ... you'll go one way and the bike will go another.

[Paul De]

I think counter steering is also working at parking lot speeds. The CS at these slow speeds is a slight nudge to slightly lean into the turn followed by what appears to be turning left to go left but is again actually CS to hold the machine up and keep from cork screwing into the pavement due to the pull of gravity. When you have completed your turn you apply more CS to lift the machine out of the lean and back onto balance over its tires. Just like at hi-way speeds.

 

Don't believe it? Try this. As you ride up to a stop and just before you come to a halt turn your bars right or left.....be careful as the bike will want to fall to the side away from the turning motion.

[hngininthr]

I've learned my lesson. Never get involved in a countersteering thread.

[Andrew]

Actually I think CS threads are fun. Its an interesting question. It is right to say that you do initiate the turn at slow speed with CS input, but you then have to turn the bars in the direction of the turn to stop the bike from falling over, hence the confusion. That is the weight of you and the machine is held up a at slow speed by the angle of the front wheel relative to the rest of the bike - think about it.

 

Funnily enough it reminds of the first edition of the Goldwing - gawd, 1975? The handling was "interesting" as the CS input got the bike in to the turn, but you then had to steer the bike round the corner once cranked over to stop it falling in too much (by that I mean you had to steer in the direction of the turn) - very wierd feeling indeed because it was so pronounced. I've had other bikes, notably a Jota which always wanted to stand up through the turn, in other words you had to CS the bastard all the way through the turn - no let's make that wrestle.

 

Therefore to answer the question, when does one turn in to the other? Answer, it doesn't. You need a bit of CS to varying degrees, then a bit or a lot or none of the other depending on speed and the characteristics of the bike - how we "know" beats me - let's call it balance.

[codinn]

Kind of reminds me of the "Intelligent Design" thread...

 

OK, sorry about the smug comment

 

Countersteering is not a mystery, myth or religion. It is a well understood principle. It has little or nothing to do with the gyroscopic forces of spinning wheels. For a concise explanation of how and why it works, snuggle up with a copy of David L. Hough's Proficient Motorcycling. A good read that will get you thinking about spring riding!

[Joe Frickin' Friday]

It is right to say that you do initiate the turn at slow speed with CS input, but you then have to turn the bars in the direction of the turn to stop the bike from falling over, hence the confusion.

 

This is true at all speeds. I think a lot of confusion may stem from the distinction between the force being applied to the bars, and the position of the bars.

 

It's a fact that a motorcycle will not travel on a curved path unless the bars (and front wheel) are shifted from a straight-ahead position. You can hang your body off to one side all you want, but if the bars aren't free to move, the bike won't turn; it'll just fall over.

 

Before you can begin the turn though, you have to get the bike leaned over, and that's where the countersteer is important: to steer the bike out from under itself. Consider a left turn. Regardless of speed:

 

-Push forward on the left bar

-front wheel points to right

-contact patches move to the right

-the bike leans to the left.

 

Once the bike has achieved an appropriate lean angle, you releax your push, and the natural self-correcting steering geometry of the bike (a consequence of steer head angle) will turn the bars slightly to the left of center. NOW the bike is actually following a left-hand turn. If you don't restore some forward push on the left bar, the bike's self-correcting steering geometry will cause it to steer even harder to the left to get back under itself; this is why, once you've entered that left turn, you need to start pushing on that left bar again - so that you'll continue to turn left. If you want to go straight again, you relax your push on the left bar, and let the bike upright itself - or help it along by pushing on the right bar instead.

 

At elevated speeds, there is a gyroscopic stabilizing influence from the wheels. When starting a turn, to achieve a certain lean angle in a given amount of time will require greater handlebar countersteer force (but less movement) than at lower speeds:

 

-At 10 MPH, the bike is positively wobbly; with virtually no gyroscopic stabilization from the wheels, the tiniest forward push on the left bar puts the bike into a left lean where it wants to fall over, and you have to quickly relax your countersteer input and crank the bars to the left. Doesn't take a huge amount of force, but the steering displacement (after the initial countersteer) are pretty large; that final left-crank on the bars is very visually apparent, a large angle away from straight-ahead.

 

-At 40 MPH, the bike happily enters a left lean with a modest left-push, but willingly rights itself, even without a right-push. fairly light forces on the bars, and hard-to-see steering movements. Watch on-bike videos of Deal's Gap in which you can spot handlebars or brake fluid reservoirs, and the steering movements are pretty subtle.

 

-At 120 MPH, the bike leans like it's sitting in a tub full of molasses: if you want to rapidly lean left, you have to push HARD on the left bar. It won't fall over if you then take your hands off the bar, but it certainly does take its time righting itself. While steering input forces are high, actual steering movements are very small; again, look for on-bike videos of high speed rides in which you can see handlebars (or brake fluid reservoirs).

 

Therefore to answer the question, when does one turn in to the other? Answer, it desn't. You need a bit of CS to varying degrees, then a bit or a lot or none of the other depending on speed and the characteristics of the bike - how we "know" beats me - let's call it balance.

 

That about sums it up.

[SkidMark]

So Basicly, CS is a controled crash?

[leikam]

In the trivial way that all riding is, yes.

[FlyingFinn]

So Basicly, CS is a controled crash?

 

I would call it more of a controlled fall. A good analogy beeing a stick balanced on your finger.

The stick is actually never at perfect vertical, you just move your figer to keep it "under" the stick.

 

--

Mikko

[ShovelStrokeEd]

Any of you doubters on the effect of countersteering have only to perform this simple test. Put your left hand in your pocket and go make a turn, regardless of speed. Let me know how you made out.

[FlyingFinn]

Any of you doubters...

I'm sure you are not calling me a doubter, because I BELIEVE

IN CS. Yes, one might could even say I have faith.

 

There was an excellent discussion on Science Friday on NPR not too long ago in which a university professor explained how/why it is possible to keep bicycle upright while riding.

Basically nothing to do with gyroscopical forces, it's all about this controlled fall thing.

 

--

Mikko

[tobyzusa]

Regardless of speed:

 

-Push forward on the left bar

-front wheel points to right

-contact patches move to the right

-the bike leans to the left.

 

==========================

 

Can't agree with that statement [-Push forward on the left bar; -front wheel points to right]. At anything over slow to moderate speed, the bars do not actually turn a significant amount. The turning force does not come from a "turn of the bars".

[SkidMark]

Hey, I agree with Toby. Its more like flying..a pilot will tell you to add slight pressure to the controls.

[Joe Frickin' Friday]

Regardless of speed:

 

-Push forward on the left bar

-front wheel points to right

-contact patches move to the right

-the bike leans to the left.

 

==========================

 

Can't agree with that statement [-Push forward on the left bar; -front wheel points to right]. At anything over slow to moderate speed, the bars do not actually turn a significant amount. The turning force does not come from a "turn of the bars".

 

I guess it depends on how we define "significant." The movement may be so small as to be difficult to see, but there definitely is a movement. Visually, it's not significant - but in terms of making the turn happen, it most definitely is significant.

[motorman587]

Everyone is correct. We are all taking about the same thing, as we always do, but in different language. I think the question was, even if was wrong about CS, what happens between CS and low speed turning. At what speeds does this happen? I can not answer that, but I can tell you this that at low speed parking lots, cone weave etc........ you got to turn the handle bars. At higher speeds, 10-12mph you must "push right to right or push left to go left" which is CS. Do not ask me why.

[ShovelStrokeEd]

John, you turn the handle bars to maintain stability of the bike once the turn is initiated. You still initiate the turn with countersteer. Don't believe me? Try my one hand thing and watch what happens.

[motorman587]

John, you turn the handle bars to maintain stability of the bike once the turn is initiated. You still initiate the turn with countersteer. Don't believe me? Try my one hand thing and watch what happens.

 

Ed the wise one. I have tried it may times, one handed, brother. Contersteer happens at higher speeds, more sharper the turn the more press and turning the handlebars at lower speed in the direction you wish to turn with counter balance for tighter turns. I think that is what you are talking about.

[rdfrantz]

John, you turn the handle bars to maintain stability of the bike once the turn is initiated. You still initiate the turn with countersteer. Don't believe me? Try my one hand thing and watch what happens.

Ed, from your limitied statments in this thread I don't really get what you are trying to get the rider to experience, nor what you think they should do to get that.

 

I ride one handed - Right handed - much of the time. I turn the bike to the right by applying a slight forward pressure to the right grip and then releasing it so the the wheel and bars can turn to the right in response to the lean to the right of the chassis the initial push caused. The bike turns to the right.

 

To turn to the left, left hand "in my pocket", I simple pull on the right grip, a gentle pressure that is quickly released, the bike leans left, the front wheel and bars turn left, and the bike turns left.

 

 

If you are trying to have the rider experience the difficulty of turning the bike at gyrostabilized speed, without countersteering, then have them lock the throttle open, or set the cruise control, and remove both hands. I find that at speeds of 60 to 80 mph on my favorite deserted road, I can cause motion within my lane, and even take gentle bends, without touching the bars. However, it takes very high effort, it is not precise, and it can bring about neither quick nor sharp turning motions. Effectively, the level of lateral control the body of riders consider normal, cannot be accomplished without counter steering.

 

Virually all our lateral control is accomplished with counter-steering, then releasing the bars. I've spent hundreds of hours investigating and communicating this through the use of everything from modeling clay to very expensive pressure transducers. Mostly to help manufacturers and racing firms refine suspenstion and control geometries for racing bikes.

 

Counter-steering is in effect "The Secret" of riding a bicycle, and a motorcycle. It is something learned by "feel", and trained up beneath the conscious level of most folks.

 

The original poster's question, suggesting a "transition zone", points to why a new two-wheeled rider has a period of difficulty learing to control the vehicle: "How to Ride". The bike initially responds as expected to one set of inputs, first encountered because the rider begins the ride from a stop and first achieves speeds where that control set is effective. Then, the bikes is "suddenly" at the gyrostabilized speed zone where the reverse set of control inputs are the effective ones.

 

"The Transition Zone" does exists, and it can be felt by those willing to be both observant, and sensitive to very light force changes. All bikes actually "wobble" for a time as they are accelerated to the gyrostabilized range. That usually happens very quickly on a motorcycle so there isn't much time to percieve the instability. Then, heavy motorcycles achieve a moment(um) prior to the Transition Zone that allows it to pass through it, somewhat stabilized by that moment - thus what there is to percieve is made minute.

 

The span and magnitude of the transition zone is related to the geometry of the vehicle. It is possible to shorten the rake and trail of a sport bike, particularly through lowering the triple clams on the forks, in a relationship to its wheelbase, that produces incredible instability below 10 mph, effectively dragging the lower end of the Transition Zone to zero mph.

 

Conversely, some cruisers, and even the K1200RS/GT, because of their long wheelbase relative to steering geomethery, can be very unstable at certain narrow or wider speed ranges. One of the great problems that arose for the current Motorcycle LSR holder was simply getting the bike from zero mph to a speed where latteral control could be gained. The rider crashed four times before he ever got the pontoon thing up to 60 mph. That's a long way in which "either, neither, nor both" ways of controlling a two-wheel vehicle worked.

 

But, that very much is a "zone" that exists for all of them.

 

Best wishes.

[Green RT]

Someone correct me if I am wrong:

 

The gyroscopic effect may contribute something to counter steering-induced lean, especially at speed. But I suspect a bigger effect is trail. Because the front wheel is out in front of the axis that it pivots around, turning the front wheel moves the contact patch out from under the bike causing the bike to fall the other way. This will happen at any speed.

[motorman587]

Someone correct me if I am wrong:

 

The gyroscopic effect may contribute something to counter steering-induced lean, especially at speed. But I suspect a bigger effect is trail. Because the front wheel is out in front of the axis that it pivots around, turning the front wheel moves the contact patch out from under the bike causing the bike to fall the other way. This will happen at any speed.

 

Bigger effect at trail??? Do not know what that means. I do know that at low speed you must turn the handle bars. If I wish to turn left, turn the handle bars left. At hight speeds if I wish to go left I must now press the handle bars. If I wish to make this turn tighter, high speed, I must press hard or can put some body lean, dragging knee etc.......

[Green RT]

Bigger effect at trail??? Do not know what that means. I do know that at low speed you must turn the handle bars. If I wish to turn left, turn the handle bars left. At hight speeds if I wish to go left I must now press the handle bars. If I wish to make this turn tighter, high speed, I must press hard or can put some body lean, dragging knee etc.......

I just meant that the effect of trail in inducing lean is a bigger effect than the gyroscopic effect. I agree that at slow speeds you have to point the tire the way you want to go, independent of lean.

[FlyingFinn]

I do know that at low speed you must turn the handle bars. If I wish to turn left, turn the handle bars left.

Even at low speeds you must CS. To initiate the turn.

To follow through (and keep the bike from falling over) you turn the handle bars. For all practical purposes, the only way to INITIATE a turn is to CS.

The rider experience of what happens after the turn is initiated depends on the speed.

 

If I wish to make this turn tighter, high speed, I must press hard or can put some body lean, dragging knee etc.......

No matter how much you body lean, the turn still must be initiated by CS. By hanging off you can reduce the amount of lean angle you eventually need to use. But it is dang near impossible to initiate a turn only by means of body lean.

 

--

Mikko

[rdfrantz]

Even at low speeds you must CS. To initiate the turn.

I'm sorry, but that just is not true.

 

Only because it is lighter and easy to handle, use a bicycle. Hold the longitudingal frame rail and move the bike forward, walking beside it.

 

Lean the frame rail toward you while continuing to move forward. The wheel will turn toward you, and the bike will then turn toward you.

 

Never in this process have you engaged in counter-steering.

 

 

This occurs the same way, and for the same reasons, on a motocyle at speeds below which gyrostablization can be overcome by shifting body weight to cause the chassis to lean, and have the front wheel "follow".

 

At nearly stopped speeds, one can turn the bars only in the direction of desired travel, and have the bike turn in that direction. Depending upon the speed, and thus the force generated, the bike will need to be leaned into that turn to a degree matching the generated force or the bike will fall toward the outside of the turn.

 

Try it.

[ShovelStrokeEd]

Exactly!

 

It is trail that causes the phenomenon and it is trail that really makes the coutner steering work. The effect is very subtle at low speeds and may not be felt by the rider as the transition to turning the bars to keep on track almost masks it.

 

I am familiar with the effect Dick speaks of as well. My drag bike has a 74" wheelbase, 45 degrees of rake and God knows how much trail, probably in the neighborhood of 10" or so. The front wheel never "gyrostabilizes" because it doesn't touch the ground till about 140 or so. Back when I was first setting up the chassis, I had the wheelie bars too low and the front end was on the ground through most of the run, at least till the rear tire grew enough to allow the front wheel to unload. In that condition the bike was quite a handful to steer, it didn't much want to steer like a normal bike up to 100 or so and actually required turning the bars into the turn to get it to steer, along with a good deal of hanging off. Over 100 and things settled in. Now, none of this was helped very much by a square, 10" wide tire with 4 lbs of air in it transmitting a couple of hundred HP. The bike pretty much would go whereever the rear wheel was pointed. Back on point, the transition zone for this bike was near 100 mph.

 

Back in the day, when I toyed with building my own frames, we often talked about when the bike would change from "car steering" to motorcycle steering. It often didn't happen to well past half track. This was with laydown type motorcycles more like what you see on Top Fuel bikes these days. The wheelbases were very long, the bikes were heavy and the front wheel pretty much stayed on the ground. If you look at Pro Stock bikes these days, the front end geometry is getting back much more conservative figures for rake and trail. In part due to aerodynamics as the front wheel does much better tucked up inside the fairing, it's probably the least aerodynamic part of the bike. The other reason is the bikes have to make the turnoff at the end of the run. Watch the riders, they still countersteer to initiate the turn, there is not much lean to be had on these things as the fairing, which is wider than the engine's bottom end, is only 2" off the ground so the riders hang way off. You will notice that they don't use car steering though, the front wheel is on track with the length of the bike, and until nearly stopped they don't turn the bars much at all. They can't, there is only about a 1" wide strip of tire in contact with the ground at it would just push.

[FlyingFinn]

Lean the frame rail toward you while continuing to move forward. The wheel will turn toward you, and the bike will then turn toward you.

That is very interesting experiment, have done that many time pushing bicycles from behind with no reach to the handle bars.

But I do think there is a difference, and this is just my best understanding of two wheeled steering dynamics.

Doing what you just described you apply EXTERNAL force to the bicycle to make it lean. And thus there was no need to CS.

While riding that same bicycle (or a motorcycle) it is impossible to apply any external force and in that situation the best way to get the bike leaned over is to CS.

 

At very low speeds it takes just takes so little effort to do that little CS move that it is not even noticed by the rider.

 

--

Mikko

[motorman587]

Is this like "if a bathtub is full and about to flow over and a nat pee into it" Would it make a difference?

[BitScribbler]

Everyone is correct. We are all taking about the same thing, as we always do, but in different language. I think the question was, even if was wrong about CS, what happens between CS and low speed turning. At what speeds does this happen? I can not answer that, but I can tell you this that at low speed parking lots, cone weave etc........ you got to turn the handle bars. At higher speeds, 10-12mph you must "push right to right or push left to go left" which is CS. Do not ask me why.

 

Motorman has the correct slant of my original question. Just mention the word countersteer and a thread takes on an entirely new life. I truly didn't mean to open the whole can of worms!

[Joe Frickin' Friday]

That is very interesting experiment, have done that many time pushing bicycles from behind with no reach to the handle bars.

But I do think there is a difference, and this is just my best understanding of two wheeled steering dynamics.

Doing what you just described you apply EXTERNAL force to the bicycle to make it lean. And thus there was no need to CS.

 

This is correct. Shoving the frame of a bicycle around while walking beside it isn't a fair test. RDF is correct that the handlebars want to turn whichever direction the bike happens to be leaning, but that doesn't explain how the turn gets started, namely a countersteer.

 

I wrote the following piece a year or two ago in response to an assertion that body-steering, without any handlebar inputs, results in countersteering. It's long-winded, but hopefully comprehensible.

 

=======================================

A little while ago I was getting ready to scream "That's bullsh!t!" to DCB's assertion that body-steer induces a turn via countersteering, in spite of no input at the handlebars. Then I started thinking about it some more, and I saw that he’s right, there really is a countersteer involved there, despite not touching the handlebars. I'm gonna drag some physics in here, but I will try to explain it all so non-geeks can understand.

 

Conservation of Linear Momentum

For an object in linear motion (or at rest), its linear momentum is defined as mass times velocity. In any interaction between two objects, i.e. a collision or a “pushing off from each other,” the total momentum is conserved. For example, suppose you are sitting at one end of a canoe, and the canoe is stationary in the water. The total combined momentum is zero. You get up and crawl to the other end of the canoe. You pushed against the canoe to get your body moving in one direction, and as a result the canoe moved in the opposite direction; you built up momentum in one direction, and the canoe built up equal and opposite momentum, so that the whole time you are in motion, the combined momentum (your body + canoe) is still zero. In other words, the combined center of mass is not moving at all. When you reach the far end of the canoe and sit down, you've moved one way, and the canoe has moved the other way, with the net result that the combined center of mass is in the same location as it was before you started. This is also a good example of Newton's ? law stating that "for every action there is an equal/opposite reaction."

 

Conservation of Angular Momentum

For an object in angular motion, i.e. moving in an arc around a pivot point, its angular momentum is defined as the mass times the velocity times the radius of the arc of motion. In any interaction between two objects in angular motion, the total momentum is conserved. For example, suppose you are sitting at the edge of a merry-go-round (MGR), and the MGR is stationary. Net angular momentum is zero. You get up and walk along the edge in one direction, and as you push off to get moving the MGR starts rotating in the opposite direction; you've developed angular momentum in one direction, and the MGR has developed angular momentum in the opposite direction, so the whole time your body is moving, the net angular momentum is still zero. When you finally stop and sit down again, the MGR stops too; net angular momentum is still zero.

 

Angular Momentum and Body/Bike Lean

How is angular momentum involved in this picture? Where leaning (of your body or the bike) is involved, you and the bike rotate about an axis that runs from the front contact patch to the rear contact patch. So picture this: you’re cruising along in a straight line, sitting centered on the bike. You and the bike have a combined angular momentum of zero about that contact-patch axis, i.e. you’re not falling over to the left or right. Now you move your body to the left. Just like the MGR moved in the opposite direction you moved, the bike behaves the same way: it leans to the right. The net angular momentum of you+bike is zero the whole time: the combined center of mass hasn’t shifted at all, and would be quite happy to continue bookin’ down the road in a straight line, if the handlebars weren’t allowed to move. How does this right-lean of the bike lead to a left turn? Keep reading.

 

Steering Geometry and stability

The steering axis is the axis around which the handlebars turn. Usually it's parallel to the fork tubes (maybe slightly off on the RT, thanks to Telelever), and set a bit to their rear. On the RT, the steering axis passes through that black plastic disc that your key fob sits on while you're riding.

 

The rake angle is the angle between the steering axis and a vertical line, e.g. for the RT it’s probably about thirty degrees. Because of this rake, the front tire’s contact patch is well to the rear of the steering axis. Stand to the side of your bike, and with your eye follow the line of the steering axis to where it intersects with the ground: you’ll see that that point is well forward of the contact patch. Suppose the steer tubes on the bike were straight up and down, i.e. rake angle = 0; then the steering axis does pass through the contact patch.

 

How do these two different geometries behave when you’re cruising down the road with no hands on the bars, and you+bike start falling to the right?

 

Let’s start with the zero-rake case. The road is pushing straight up on the front tire’s contact patch. Because the steering axis also passes through the contact patch, that road-force doesn’t produce a torque about the steering axis: the handlebars will not move, and you+bike will continue falling unimpeded to the right. Hope you’re wearing a Roadcrafter.

 

Now let’s try the non-zero rake case, e.g. the RT. This case is much more interesting. As in the previous case, the road is pushing straight up on the front tire’s contact patch. But because of the rake angle in this case, the steering axis doesn’t pass through that contact patch – it intersects the road forward of the contact patch – and the result is that that vertical road force in this case produces a torque about the steering axis that causes the handlebars to turn to the right, steering the contact patches back underneath the bike until the bike is vertical again. The mirror-image process happens if you+bike starts falling to the left: the bike will again steer the tires back under itself, without your having touched the handlebars. Because of that rake angle, it’s a self-correcting system: the bike wants to be vertical, and if it’s not it automatically tends to steer itself into a vertical position.

 

Larger rake angles increase the sensitivity of the bike to lean angle, i.e. a slight lean angle causes a very strong corrective tendency. The gyroscopic effect of the wheels slows this correction process down when travelling at significant speed. At low speeds, where the gyroscopic effect is negligible, bikes with large rake angles (the typical “chopper”) suffer from “wheel flop,” in which a slight lean to one side causes the handlebars to want to slam all the way to the lock in that direction; the result is a violent overcorrection that leans the bike in the other direction, which causes the bars to slam to the lock that way. The process repeats until something breaks or the rider bails; the whole thing ain’t pretty.

 

Stability and Body Steering

Body steering uses the bike’s “desire” to be vertical to manipulate it into turning.

 

Let’s say you’re riding the “No BS Bike” and want to negotiate a left turn without directly applying a steering input. You+bike are cruising in a straight line; there is zero net angular momentum about the contact-patch axis. You lean your body left, and as explained earlier, the bike leans right. As in the previous case, the road is pushing straight up on the front tire’s contact patch. But because of the stability induced by the rake angle, the bike itself (without regard to where you’re positioning your body) wants to get itself vertical again. Through the contact patch/gravity/rake interaction described earlier, the handlebars magically turn to the right. The result is the same (if a bit more sluggish) as if you yourself had gripped the bars and turned them to the right: the contact patches get steered back under the bike – to the right. This is the countersteer, induced without any direct input to the handlebars.

 

As soon as those contact patches start moving to the right, the combined center of mass of you+bike begins falling to the left. The bike, which was leaning to the right, begins to stand up straight, passes through vertical and begins leaning to the left. The vertical road force on the front tire now begins to torque the handlebars in the opposite direction, i.e. to the left; you are now negotiating a left turn, without ever having touched the handlebars. Cool.

 

The more the bike leans to the left, the more urgently it wants to get the tires back under itself. You can maintain a left turn in two ways:

 

1. Maintain your body-lean to the left. Gravity works in your favor, providing an influence that counters the bike’s “desire” to get back under itself.

2. Apply a steering input that prevents those bars from turning to the left: you push on the left grip, holding the bike in that left turn.

 

The masterful riders, it would seem, are the ones who use a combination of body-lean and direct steering input to get a left turn started, and then use body-lean to maintain that left turn with minimal (ideally zero) input at the handlebars.

 

By building the bike with less rake angle – as road-racing bikes typically are – you decrease the stability described earlier. The bike isn’t so anxious to get the wheels back under itself, which means body-lean is much more effective in instigating and maintaining a tight turn.

 

Body Lean and Bike Mass

So why does body steering work dangerously well on a bicycle, and more subtly on a fat pig of a motorcycle? It goes back to the conservation of angular momentum again. Suppose you shove yourself way to the left of the bicycle, relatively speaking. Well, your body doesn’t go that far to the left, but the 20-pound bicycle gets leaned way to the right, resulting in a very strong correction that will snap you nicely into a left turn. Now try it with the RT. Your speck of a body moves way to the left, and the fat pig of a motorcycle just barely leans to the right. In each case the net angular momentum doesn’t change, but the vastly different vehicle masses produce very different responses.

 

If I put a lead brick in the left saddlebag, but did not otherwise change my riding position, do you believe that the bike would PTTL?

 

If you started out cruising straight with the brick in your lap, and then moved it over to the left saddlebag, the effect is the same as if you hung your body out to the left: conservation of angular momentum, bike leans right, countersteers itself, and starts a left turn.

 

Suppose instead that some crazy drunk kids in a pickup truck pass you on the left, and one of them deftly sets a brick in your left saddlebag. You didn’t see it happen, so you keep sitting up straight in the saddle. The countersteer won’t happen this time: The bike itself is vertical so there’s no tendency for the handlebars to turn. However, thanks to the surreptitious addition of the brick, the combined center of mass of you+bike+brick is now to the left of the contact patches, and the whole conglomeration begins to fall to the left and starts a left turn.

==========================================

[rdfrantz]

That's a lot of words, Mitch.

 

Once again, I see an issue arising, and lots of people staring at computer screens... and therefrom, developing conclusions.

 

I see others who go outside, sit on a motorcycle, get it moving forward at a walking pace, and then they turn the bars to the right, or lock the throttle open, remove their hands from the bars, lean the bike to the right with body force, and the bars are forced to turn to the right... and the bike turns to the right. Just like it has for the last 100 years.

 

Once again, the conclusions of the first group didn't seem to prevent the physical facts from appearing.

 

Thank God.

[FlyingFinn]

Now this one is very much tongue-in-cheek, so please anyone don't take it the wrong way. I just couldn't help myself.

I see others who go outside....

...and observe the Sun circling around the Earth rising from the east, making its arch across the sky, and setting to the west.

 

Just like it has been doing for millions of years.

 

--

Mikko

[Joe Frickin' Friday]

Once again, I see an issue arising, and lots of people staring at computer screens... and therefrom, developing conclusions.

 

I see others who go outside, sit on a motorcycle, get it moving forward at a walking pace, and then they turn the bars to the right, or lock the throttle open, remove their hands from the bars, lean the bike to the right with body force, and the bars are forced to turn to the right... and the bike turns to the right. Just like it has for the last 100 years.

 

Once again, the conclusions of the first group didn't seem to prevent the physical facts from appearing.

 

Thank God.

 

Rest assured, I will be doing the same - in a couple of months. You'll have to excuse me if I don't go fire up my RT right now; the weather is less than inviting. While experimentation would indeed be the superior solution, until such time as I can engage in said experimentation I've only got the laws of physics and some logic to work with.

 

...lock the throttle open, remove their hands from the bars, lean the bike to the right with body force, and the bars are forced to turn to the right...

 

How do you lean the bike to the right with body force? Lean your body right, bike leans left, countersteers all by itself, and then, yes, the bars turn to the right, commencing the right turn. but there was that little countersteer in there, even without your hands on the bar. It may not be visible to your eye while you're riding, but if you hook one of these to your handlebar, you'll see the bars turn slightly left before you start turning to the right. It would be interesting to see the "parking lot speed" question answered via the same means.

 

If I can find a cheaper transducer to measure steering displacement - rotary would be best, but I can make a linear displacement transducer work too - I'll definitely look into this. Anyone have a spare TPS lying around they'd be willing to part with?

 

 

(You're laughing, but this summer a friend and I will be instrumenting a potato cannon to see what the combustion chamber pressure looks like.)

[ShovelStrokeEd]

Potato cannon! POTATO CANNON! Screw the steering business, I have managed the last million or so miles with no problems. Now we found something serious to talk about.

 

A lot depends on your choice of propellent. Propane, hair spray, natural gas, hydrogen, acetalyn/O2 mix, I have tried them all with mixed results from burst barrels to just a phoot. Fit of tuber in bore is also critical. 2" sched 40 PVC is pretty available. Lemmee know if I can help. I have access to pressure transducers of 500 PSIA up to 60K PSIG. 24 volt input, 5.0 vdc output full scale. Swageloc connectors.

[rdfrantz]

Mitch, it's been ages since I saw you at Torrey, and I hate that. I also hate that you have to lay your bike up for the Winter. May time pass quickly. For both of us.

 

The Facts you post are always true. I find them incredibly valuable, and they lead to my actually riding better, and to enjoying that riding more. But, as in many discussions you and I have and share, they don't describe all the affecting phenomena. I love to prove the documented things like you so helfully share with us. And like our Finnish friend, love to get out in the light of day (He gets 4 months of nearly all daylight, the lucky devil) and see how it ALL really comes together.

 

To clarify about riding Hands Off, to apply only body force to turn a bike, remove left foot from the peg, and lean all the body weight over the right peg. That's less effective than "swinging" the torso to the right, while applying pressure to the tank side with the left knee so as to prevent falling off the bike to the right... and creating the "right roll Force Point" at tank and knee/thigh juncture. With the latter manner, the bike rolls right quite vigorously when traveling at low speeds, and less so with the former manner.

 

In support of your statement about Hands Off countersteering, as kids we rode our bikes Hands Off much of the time. We could do what we called "Flop the bike", get a very vigorous rolling and then turning motion, by vigorously slightly twisting on the seat to the left, RIGHT leg applying force to the seat "Nose", and then promptly reversing the twist back to the right, again appling the force now with the LEFT leg to the seat nose. That was very much an act of "counter-steering".

 

However, that only produced a more vigorous turning moment - and a DELAYED one - compared to simply, less vigorously, applying pressure with the LEFT leg to the seat nose, and leaning the torso to the right.

 

 

But, lets move away from this "body-steering" phenomanon and get back to the original poster's "bar-steering" world.

 

So far in this thread, there has been a "not wholly and exactly true" deptiction about a sequence of 1)Low-speed-range, pro-turn-steering Zone; 2)A Transition Zone; 3)High-speed-range, counter-turn-(first)-steering Zone. As you either actually state or allude to, counter-steering-(first) does work at #1 as well as #3. It EFFECTIVENESS ranges from zero at zero speed and increases with increases in speed. Yes, it "(almost)always" works.

 

That does not mean something else does not work in Zone #1.

 

Remember Zone is about LOW speed. Low forces are generated.

 

In that speed zone of "just before coming to a stop at a stop light", where we (Evil and Wanton, Hellions) Play The Balance Game until the light changes, we forcefully (even Viscously) turn the bars to the right, and off to the right goes the front wheel of the bike.

 

Yes Mitch, there is a TENDENCY, a generated Newtonian Force, for the bike to roll to the left, the Adverse Roll Force.

 

But, guess what? IN THE REAL WORLD IT DON'T AMOUNT TO SH##!!! The bike has started moving off to the right - as it MUST. We got what we want.

 

Yes, we also get some "what we don't want". We counter the Adverse Roll Force with... MINUTE shifting of body weight.

 

In fact, the most Evil, Wanton, and Insouciant among us, shift the weight just before we "viscously and with zero tollerance of other Demand", FORCE the bars to turn right. And all works out just fine. Several time a second in fact, as we move the bike in directions we want, and counter its unwanted diverstions arising from incomplete "balance" (of forces). Man does not live by Bars alone. He, he, he.

 

Yes, your're Right, Mitch. On paper.

 

We use more than that set of papers out in the real world.

 

When it's not too cold and icy to do so.

[FlyingFinn]

Not at all icy or cold here in Phoenix right now.

62F and sunny.

 

Just had to step outside and snap a photo of myself in the perfect sunny weather.

 

I'll pay special attention to the steps of "turn initiation" today when doing my daily U-turn practices after the work.

I was quite satisfied after being able to make a u-turn with the RT inside two parking slots. Now I need to go back and do the same while having the "mental action recoder" turned ON.

 

--

Mikko

[rdfrantz]

Great, guy.

 

What you discover will be valuable, to you and to us all. I'm sure you'll be able to explain stuff in more and better ways.

 

I'm so glad you've got some good weather to play in too.

 

Best wishes.

[FlyingFinn]

Here's the report. All subjective observations, no rotary transducers involved so we need to leave some room for error here.

 

I did my normal slow-speed maneuver exercises and other turning experiments at the parking lot using speeds from 0 to 30mph.

Down to about 10mph I can see the counter steer happening at the very beginning of every turn. And I tried NOT to CS, none or the "push left to go left" stuff. Just simply turned left and WATCHED the movement of the handlebars.

And sure enough, the bars do make a slight nudge to the "wrong direction" at the very beginning of the turn.

 

At below 10mph the tiny CS movement becomes too small to see but I do think it's still there.

 

I want to underline the point that during all this experimenting I was trying not to CS. I tried to make a simple (but relatively sharp) turns the way I would if I hadn't ever even heard about counter steering!

 

I think at low speeds (<30mph) the force required for the CS move becomes so low that we simply can't detect it as push to the bars anymore. But it can be seen as a small movement.

At higher speeds the gyroscopical force of the front wheel increases and forces us to use detectable about of push force. To the point that we need to practice that push to make the bikes turn quickly at high speeds.

 

--

Mikko

[ShovelStrokeEd]

This is why I suggested the one hand thing. With both hands on the bars and even the lightest of touches the effect gets masked. With only one hand you can only move in one direction. Right hand on the grip, left hovering, now try to do a left turn by pushing on that right bar (car steering). You will immediatly feel the bike want to heel over to the right. The opposite of your intent. Even down at walking speed.

[BFish]

try not to think about "cs" and just as important, look where you're going. turn your whole head. don't even sneak a peek down. lean a tad, "cs" with inside arm a bit and this slow turning deal will be a long-forgotten issue before you know it.

 

i had to learn "cs" racing bicycles in criteriums. much worse (from a stress standpoint) than turning a moto as you're surrounded by bikes, going fast, everyone screaming, still pedaling (sometimes) and you can't scrub off any speed. plus it really hurts to crash!

[FlyingFinn]

That is the way to do it.

 

But that was not really the point of this thread. The questions was, "Is CS required, or does CS happen, even at VERY low speed turns?". We all know the situation at speed, but at crawl thinks get muddy.

 

--

Mikko

[BFish]

That is the way to do it.

 

But that was not really the point of this thread. The questions was, "Is CS required, or does CS happen, even at VERY low speed turns?". We all know the situation at speed, but at crawl thinks get muddy.

 

--

Mikko

 

i believe it does and can't emphasize the importance "looking" ahead or where you're going in the whole process. i will admit that pushing the bike "down" into the turn and "counter-leaning" the opp way in a real, slow tight turn works. however, if that manuever is analyzed "cs" is happening in the push down towards the turn.

[Wooster]

We all know the situation at speed, but at crawl thinks get muddy.

 

FlyingFinn,

 

Crawling is different animal. Push beemer across garage and how do you steer ? Directly, I suspect. Aiming wheel right turns bike right, doh !

Now, at what speed does direct/counter transition occur, I don't know, maybe 10 kph ?

 

Wooster

[ShovelStrokeEd]

Yeah aiming bars right turns wheel right but which way does the bike lean? To the left. It even works at the very minimal speed when taking the bike off the center stand. Stand on left side of bike, lean over and grab the bars and then push forward. You had better have the bars turned a bit to the right so the bike will lean into you (standing on the left side) or you'll be replacing a mirror.

 

This ain't gyroscopic precession or anything else other than the effect of trail transmitting steering forces to the chassis.

[Joe Frickin' Friday]

Yeah aiming bars right turns wheel right but which way does the bike lean? To the left. It even works at the very minimal speed when taking the bike off the center stand. Stand on left side of bike, lean over and grab the bars and then push forward. You had better have the bars turned a bit to the right so the bike will lean into you (standing on the left side) or you'll be replacing a mirror.

 

This ain't gyroscopic precession or anything else other than the effect of trail transmitting steering forces to the chassis.

 

That's not trail either, though. Trail does help make the steering self-correcting at speed, but deliberate countersteering would work to maneuver the bike even with a purely vertical steering axis.

 

I bought a couple of $2 rotary potentiometers at Radio Shack last night. I'm gonna see what I can cobble up before the weather gets nice again...

[Wooster]

Stand on left side of bike, lean over and grab the bars and then push forward.

 

Ed,

 

Generally, that's what I do. Sometimes, turn bar slightly to right, bike leans left to me. Regardless, what's up with gyroscopic procession ?

 

Counter steering's funny, pushing right bar bike turns right. At crawl (1st gear clutch slip), it's the opposite, pushing right bar goes left. I don't know.

 

Jon

 

And Ground Control to Major Tom, What's up w/those pots ?