Article On Countersteering

[Crafty]

Can some of you clever people help out with this article I wrote. It is based on lots of research from books and all over the net, but I still don't have the confidence that it is 100% correct. It is based on the camber on the actual wheel. Using the cone/paper cup symbology to explain. Some reckon that with counter steering you form a camber between the front wheel and back? Can any one help me out with this?

The Original article can be found at http://www.my2wheels.co.za/index.php?optio...=1&Itemid=6

 

Thank you in advance!

[jrock7896]

I loved your article bro... I thought the video you threw in there as the best example of countersteering I have ever seen in slow and on a track. nice work

[oldfrt]

Good article. Couple of observations. Precession is the term (spelling). Also brake, not brake.

 

The important thing about countersteering is that when you push with your right hand gyroscopic precession causes the wheel to LEAN to the right. If the wheel had no spin the lean would not happen and the wheel would turn to the left. It's the LEAN that is causing the turn as well as that gyroscopic precession is actually resisting a turn to the left. It's almost as if you were riding straight ahead and someone had a rope tied to the top of your front fender and pulled from the right. That would obviously cause a right turn. Precession does almost the same thing.

 

Your cup analogy was very good and correct, I believe.

[Woody]

It's funny how the subject of how a motorcycle steers keeps going on. It's a neverending circle.

 

I have a theory that is much simpler.

The lean is a necessary byproduct of cornering, which is required to counteract the forces pulling the bike to the outside of the corner. Without leaning the bike, it would tip over. Turn left, the bike tips over right. To put it another way, if you continued to pull the bars to the left, the bike would eventually fall over without turning to the right.

Once leant, you need to release the pressure on the bars in order to allow the bike to turn.

The bike actually goes around the corner because the front wheel is pointing toward the inside of the corner.

 

I don't see it any other way.

 

So, to initiate the turn the bike must first be leant over. Turn the bars to the right and the bike starts to turn right, this tips the bike onto it's left hand side. Once the pressure is released on the bars the steering geometry pulls the front wheel back around so that it is pointing into the corner and the bike starts to turn left.

 

The amount of lean is directly related to the speed of the bike and how tight the corner is. Slow down and the bike will take a tighter line for a given angle of lean.

 

I have three practical examples.

 

1. Take a turn at a relatively steady speed and roll off the throttle. What happens? The bike takes a tighter line. You need to pick the bike more upright to retain the same arc. (The opposite is also true, speed up and the bike takes a wider arc. You need to lean the bike over further to retain the same rate of turn.)

 

2. Hold a bicycle by the seat and lean it over to the left. What happens? The front wheel turns to the left. The steering geometry forces this effect.

 

3. Do a 'U' Turn. This is a very low speed manouver, btu due to the tightness of the corner, you still need to lean the bike. What happens to the bike and steering? You need to lean the bike, albeit only slightly, but which way is the front wheel pointing? To the inside of the corner.

 

I have no doubt that gyroscopic forces have some effect, but I see this as very minor and if anything this acts to prevent the bike from cornering rather than assist.

 

 

Just some thoughts for the pot. Not sure whether I have explained myself very well...

 

Have a great, safe Christmas folks

 

Woody

[jrock7896]

 

So, to initiate the turn the bike must first be leant over. Turn the bars to the right and the bike starts to turn right, this tips the bike onto it's left hand side. Once the pressure is released on the bars the steering geometry pulls the front wheel back around so that it is pointing into the corner and the bike starts to turn left.

Woody

 

I dont belive the need to be released to start the turing, otherwise there is no way I could make it through some really tight chicanes at the speed I do... THe bike turns as you are countersteering, you dont have to let off the bars to allow for the turn. In fact I can think of one chicane where I am using countersteering the entire time through and never allowing the bars to rest.

HOw does your theroy explain this?

[oldfrt]

To understand precession you can get a bicycle wheel and an axle. Hold the axle horizontal while the wheel is spinning in a forward direction. Try to rotate the wheel to the right holding the axle horizontal. The wheel will LEAN to the left same as if you were pushing on the left handlebar.

 

This is not just a theory, but a law of physics.

[jrock7896]

To understand precession you can get a bicycle wheel and an axle. Hold the axle horizontal while the wheel is spinning in a forward direction. Try to rotate the wheel to the right holding the axle horizontal. The wheel will LEAN to the left same as if you were pushing on the left handlebar.

 

This is not just a theory, but a law of physics.

 

I understand that... I wasnt questioning you I was questioning Woody.... Se the quote above my post, that is what I was questioning.

[Woody]

I dont belive the need to be released to start the turing, otherwise there is no way I could make it through some really tight chicanes at the speed I do... THe bike turns as you are countersteering, you dont have to let off the bars to allow for the turn. In fact I can think of one chicane where I am using countersteering the entire time through and never allowing the bars to rest.

HOw does your theroy explain this?

 

I would say that you are mistaken. Whatever force you are applying to the bars, the front wheel must be pointing into the corner for the bike to make it around the turn.

 

The same applies with the 'paper cup' theory. The front 'cup' needs to be pointing into the turn to make it around the corner.

If we fixed both wheels, so that you couldn't turn the handlebars and both wheels were held firmly in line, if you lean the bike, my belief is that it would continue in a straight line and just fall over.

 

Regarding the precession theory. How many times have we seen motorcycles exiting corners with the front wheel in the air all crossed up? If precession is the force making the bike lean, turning the wheel this far would surely try to throw the bike on its' side. My guess is that we need to remember that there are two wheels on a motorcycle and that the rear wheel, being held firm, will resist what we are doing with the front.

 

I have no doubt that gyroscopic precession and paper cups have an effect on steering, but I think this is merely complex 'fine tuning' of what is a fairly basic principle, that the direction in which the front wheel points is the direction in which the motorcycle goes.

[Cobie Fair]

While leaned over, if the front weren't pointed into the turn, what would happen? The bike would continue to lean. Continued presser=continued lean angle---guys can steer their bikes right into the ground (we've seen it, saw it at the last school at Sears!)

 

CF

[oldfrt]

To understand precession you can get a bicycle wheel and an axle. Hold the axle horizontal while the wheel is spinning in a forward direction. Try to rotate the wheel to the right holding the axle horizontal. The wheel will LEAN to the left same as if you were pushing on the left handlebar.

 

This is not just a theory, but a law of physics.

 

I understand that... I wasnt questioning you I was questioning Woody.... Se the quote above my post, that is what I was questioning.

I was'nt directing my comment at you, but Woody.

 

The school teaches that countersteering is what initiates the turn and that body steering is not an effective way to steer a motorcycle.

[ulrichw]

I loved your article bro... I thought the video you threw in there as the best example of countersteering I have ever seen in slow and on a track. nice work

 

The video was one of the best things about the explanation. Otherwise I found that it covered things at a high-level and not as accurately as many sites out there.

 

Unfortunately, the video was also "borrowed" without attribution. Find the original at this site: http://www.gotagteam.com/ - bottom of the page under "countersteering 101" (and for entertainment, I highly recommend the race reports there)

 

For the second half of this thread - I have to side with Woody. Gyroscopic forces appear to be a secondary factor in the steering of bikes. For good in-depth coverage of this, see here: http://www.losethetrainingwheels.org/defau...Lev=2&ID=34

 

At this site, they document experiments with bicycles which eliminated all gyroscopic force (by cancelling them out with reverse-rotating wheels of the same configuration as the regular wheels), and showed that they could still be easily ridden and even ridden with no hands.

 

Unfortunately, there's usually a lot of pseudo-science used in explaining motorcycle dynamics (e.g., when explaining the dynamics of peg weighting, hanging off, counter-weighting, lean angle etc.)

 

Here's another analogy to counter-steering:

- Human beings balance similar to bikes. You'll notice for example, that runners lean into a turn (they have to, for the same reason bikes do - they'd fall to the outside of the turn if they tried to stay upright).

- Now, think about a running back in football who wants to cut to the left. He will initiate his cut by planting his right foot to the right of his path of travel.

- This "plant" is homologous to the counter steer. By putting his foot out there, he initiates a lean to the left (the lean angle is the angle between the ground and the line between the base of his foot and his center of mass).

- This lean let's him apply the centripetal force that initiates the turn

 

Note that Woody correctly explained this in his first post - he's not disputing countersteering, he's just disputing gyroscopic precession as the primary phenomenon that makes countersteering work (correctly, in my opinion).

 

Here's another way to visualize countersteering: Instead of thinking of the direct action on the handlebars, think of it as riding the bike out from under you. When initiating a left turn, effectively, you're putting the bike on a momentary path to the right to get it out from under you. Since you stay closer to your original path than the path the contact patches follow, the bike ends up leaning to the left. Now, you'll end up turning your handlebars slightly to the left to "catch" your fall to the left (i.e., the lean), and assuming you dial in just the right amount of steering will enter a steady-state turn to the left.

 

-- Ulrich

[oldfrt]

 

Here's another way to visualize countersteering: Instead of thinking of the direct action on the handlebars, think of it as riding the bike out from under you. When initiating a left turn, effectively, you're putting the bike on a momentary path to the right to get it out from under you. Since you stay closer to your original path than the path the contact patches follow, the bike ends up leaning to the left. Now, you'll end up turning your handlebars slightly to the left to "catch" your fall to the left (i.e., the lean), and assuming you dial in just the right amount of steering will enter a steady-state turn to the left.

 

-- Ulrich

You're saying that to turn left, you first apply handlebar torsion to the right to destabilize the bike so that it leans left, then you apply handlebar torsion to the left to steer into the left turn?

 

I believe that to be totally wrong. The entire action is right hand torsion by pushing on the left handlebar and the turn is achieved almost entirely by gyroscopic precession. The more you push on the left hand grip the more you turn. I think the posts on the thread "quick turn clarification" support this. You can prove this for yourself by coasting into a turn with "hands off" and only applying countersteering pressure in the direction of the turn by pushing with the heel of the hand in the turn direction with no pressure from the opposite hand. No opposite countersteering will be needed. I say coasting, because if applying power your throttle grip could be interfering with the experiment.

 

I doubt if you will accept my argument, and hope someone with more credentials will jump in and "set us straight".

[ulrichw]

You're saying that to turn left, you first apply handlebar torsion to the right to destabilize the bike so that it leans left, then you apply handlebar torsion to the left to steer into the left turn?

 

I believe that to be totally wrong. The entire action is right hand torsion by pushing on the left handlebar and the turn is achieved almost entirely by gyroscopic precession.

 

I believe you're correct on the first half of your last sentence (no opposite torsion is needed), but incorrect on the second half (the turn is achieved by gyroscopic precession). Please follow the link I posted - the experiments were carried out by a professor of mechanical engineering - a person I would say has better credentials than even practitioners of motorcycle racing - his experiments debunk gyroscopic forces as the primary forces in controlling a two wheeled vehicle. Note that that doesn't mean that gyroscopic forces have no effect - just that they're not the real explanation for how a bicycle or a motorcycle handles.

 

Here's the explanation of where the "opposite" force comes from to turn:

- The contact patch of the front tire is slightly behind the steering axis (this is the "trail" of the front suspension as Woody mentioned)

- When you're going straight, the force on the front wheel is in plane with the steering axis, because the gravity vector is in line with the motorcycle.

- When you lean to the left, the force on the front wheel is no longer in plane. The "equal reaction" force of the ground on the contact patch is still vertical (i.e. perpendicular to the ground), but because the bike is leaned, this ends up pushing the contact patch to the right of the plane of the motorcycle.

- Since the contact patch is behind the steering axis, pushing the contact patch to the right pushes the steering to the left.

- This applies the force that actually turns the wheel into the turn, changing the path of the motorcycle.

- In order to continue increasing the lean angle, you need to keep applying right pressure - but instead of actually turning the wheel to the right, you're simply counteracting the force applied to the left from the effects of the trail and the lean.

 

-- Ulrich

[oldfrt]

Thanks. I finally did read the article. I didn't see anywhere that it discussed countersteering, but only proved that precession is not necessary, although is helpful, for stability. Actually it said that precession is necessary for stability of the naive bike if ridden hands off.

 

I looked but did not find that it mentioned what force applied to the handlebars is used to initiate a turn, i.e. left or right torque to turn the bike left or right. Do you still countersteer?

 

Also I'm not sure that all the gyroscopic forces are cancelled in the models because the counter-rotating mass while in the same plane is much further away from the rotation of the yoke.

[Cobie Fair]

I'm going to see if I can get Keith or Will in here (both are out of the office right now and travelling).

 

From a practical standpoint, the steering action doesn't have to be stopped, once the steerig is done. In other words, push left, go left. Stop pushing, the bike will stay at that angle. That won't last forever, it takes a little throttle to keep it there, and can be done in an experiment. Keith did this in the Twist Video---he has a CBR1000 leaned over in the skid pad, holding the throttle with 2 fingers--not even the palm, just 2 fingers.

 

CF

[ulrichw]

Thanks. I finally did read the article. I didn't see anywhere that it discussed countersteering, but only proved that precession is not necessary, although is helpful, for stability. Actually it said that precession is necessary for stability of the naive bike if ridden hands off.

 

I looked but did not find that it mentioned what force applied to the handlebars is used to initiate a turn, i.e. left or right torque to turn the bike left or right. Do you still countersteer?

 

Also I'm not sure that all the gyroscopic forces are cancelled in the models because the counter-rotating mass while in the same plane is much further away from the rotation of the yoke.

 

Unfortunately countersteering is not explicitly discussed in the context of the gyroscopic argument. I would argue, however, that the same forces that keep you balanced when you're upright would also be used to unbalance you into a lean.

 

The website discusses countersteering under the heading "counter-intuitive", but unfortunately does not include mention of the zero-gyroscopic argument.

 

Nonetheless, I believe that if there had been a significant difference in how the zero-gyro bikes steered, that would have been mentioned in the article and would have resulted in causing a lot of difficulty for the people who tried to ride the bike.

 

For another corroborating website, see here: http://www.reverserotatingrotors.com/mythbuster.html

 

This person has designed brake rotors which partially counteract the gyroscopic action of the wheel by reverse-rotating the brake rotors through an ingenious set of planetary gears. The page I linked has a brief reference to countersteering and gyroscopic precession, although it's not as explicit as I'd like on the subject of precession.

 

I've read a roadtest of this bike that concluded that the setup improved rideability (but I haven't been able to locate it online as of yet - I'll look again and try to link it). Again, this is a strong argument against gyroscopic precession as the primary mode of steering (this inventor in fact argues that precession gets in the way of good handling, and is a primary cause of tank-slappers).

 

I do realize that much of this argument is academic - it doesn't change the inputs required by the rider, which you and Woody both accurately described, I believe.

 

It will be interesting to see what Keith and/or Will will have to say on this topic.

 

-- Ulrich

[racer]

hmmm.

 

 

A unicycle turns in a circle.

[Woody]

hmmm.

 

 

A unicycle turns in a circle.

G'day Racer, how's it hanging?

 

As does a single bicycle wheel, rolled at an angle. This would appear to support the paper cup theory (and is probably what inspired it).

However, a motorcycle has two wheels, not one.

 

Roll two bicycle wheels, one behind the other, both at the same angle and the same speed and each will follow the same arc, but each will be at a different position in the arc. Because of this, they will not be in line (one directly behind the other). The leading wheel will, relative to the second, be pointing more into the turn than the following wheel.

It's a similar story with a motorcycle (although yes, there are differences as both motorcycle wheels are connected by the frame).

 

 

Need... mince... pies...

[jrock7896]

Thanks for sharing the links Ulrich.... The writings of the reverse rotating rotor inventor have summed up just about everything I ever needed to know about counter steering and the effects of precession have on the front wheel on the bike. Wonderful information.

Thanks again

[ulrichw]

Thanks for sharing the links Ulrich.... The writings of the reverse rotating rotor inventor have summed up just about everything I ever needed to know about counter steering and the effects of precession have on the front wheel on the bike. Wonderful information.

Thanks again

You're quite welcome. Here's a motorcycle-usa article on the bike with the reverse-rotating rotor, btw: http://www.motorcycle-usa.com/Article_Page...3207&Page=1

 

-- Ulrich

[oldfrt]

It would be interesting to carry the counter rotating brake rotor to a sufficient extreme and reverse the gyroscopic precession effect. Could be done by increasing rotor speed or rotor weight.

[Balistic]

WOW! I notice one thing that is common when gyroscopic forces come into play in the steering argument; all geometry goes out the window.

 

the bike leans because the tire has been turned out from under it and it is falling to the ground. When the input into the bars is released Trail steers the front wheel to balance lateral acceleration against gravity.

 

The gyro's in the bike resist any change in plane. the front wheel doesn't want be counter steered and it once turned it doesn't want to turn into the corner either.

 

There certainly are physics at play in the dynamic of the motorcycle but the only contribution to steering is to resist it.

 

Will

[racer]

hmmm.

 

 

A unicycle turns in a circle.

G'day Racer, how's it hanging?

 

As does a single bicycle wheel, rolled at an angle. This would appear to support the paper cup theory (and is probably what inspired it).

However, a motorcycle has two wheels, not one.

 

Roll two bicycle wheels, one behind the other, both at the same angle and the same speed and each will follow the same arc, but each will be at a different position in the arc. Because of this, they will not be in line (one directly behind the other). The leading wheel will, relative to the second, be pointing more into the turn than the following wheel.

It's a similar story with a motorcycle (although yes, there are differences as both motorcycle wheels are connected by the frame).

 

 

Need... mince... pies...

 

 

G'day to you Woodrow! It hangs, mate! It hangs! And what more can a man ask for in life? A rip snortin thunder machine?

 

 

As for bikes...

 

My thots exactly.

 

Will a longer frame/wheelbase create more front wheel offset at a given lean angle? Or a wider turn arc for a given lean angle? Will the size of the (rear or front) wheel dictate radius of turn at a given angle? Or dictate the front offset for a given front wheel size? Will the rake/trail affect the angle of that offset?

 

Hmmm...

 

Oh...who cares?

 

 

Mince pies. Mm-mm! Fond memories of lunch on the go between jobs in Auckland! So, are ya back to Tasi this year?

[racer]

OK my brain has been consumed with magnetics, particle physics and answering the question of whether the universe is an open or closed system with regards to energy and mass conservation and how that might relate to the possibilities of energy and the relativity of magnetics and gravity frame dragging. Is there such a thing as relativistic magnetic energy frame dragging?

 

So, it's gonna take a while to shift back into relativistic knee dragging. But...notice in the tagteam video how the bike continues to lean after the wheel has ceased turning and even straightened back out again?

 

Gotta go. Be back tomorrow.

[mike kromjong]

Hi everyone,

 

Here is my input about the subject.

 

For me the whole subject of countersteering seems to be the easiest to understand when you explain it like this:

 

The center of mass of a bike is always situated somewhere under the imaginary line wich can be drawn through both wheels.

 

Because of the geometry of a bike, you will remove the center of mass to the right of this line as soon as you turn the wheel to the left and vice versa.

 

This removing of the center of mass is the only reason why the bike will start to lean over to either side.

 

This effect is partially countered by the gyroscopic forces of rotating mass. Hence the bigger steeringeffort needed at higher speed.

 

The papercup thing did'nt do it for me by the way. I think you're forgetting to take in account the deformation of the tyres wich in effect produces a flat piece of rubber sticking to the tarmac, and therefor can't be compared to the papercup with the two different radius.

 

Did this help?

 

Greetings

Mike