Countersteering Confession

[Motig]

I've been plucking up the courage to say this for a while so here goes. Countersteering is all Bullshit, its a myth perpertrated by people who have nothing better to do in their spare time. There is no way Ive ever used it in my years of bike riding so there!!!!







So I went for a ride the other day.................and I do:gob:

[sAsLEX]

So you're obeying the laws of Physics as well!

It's amazing the numbers who aren't affected by those laws.

[PLUG]

... ride with just your throttle hand on the bars & start weaving (in & out of imaginary cones) as you ride down the road ... it should all be clear as mud then ...

[Grantasaurus]

You may not believe it, but its an established physical principle coming from the gyroscope effect.
I would go into it further, but it'll need someone smarter than me to explain exactly why it happens.
A diagram would help, but I'm at work at the mo so I ain't got no time.

[onearmedbandit]

Re-read his post, he does believe in it!

[Highlander]

Re-read his post, he does believe in it!

Yup just another admitting he has been doing all along just not realised.

[quickbuck]

#1. Countersteering is not a religion.

Go to your pushbike, take the front wheel off, spin it up and try and turn it.

See, the result is 90 degrees from the input.

Now, put the wheel back on your push bike, because you will need it when you bin your motorbike.

If countersteering doesn't work, then helicopters can't fly either.:gob:

http://www.superbikeschool.com/machinery/no-bs-machine.php

[BuFfY]

I am learning to ride and I find it so hard cause yeah it is very confusing and it is totally different from my car, but I have a great teacher (:love: ) and it is going pretty well :)

[sAsLEX]

You may not believe it, but its an established physical principle coming from the gyroscope effect.
I would go into it further, but it'll need someone smarter than me to explain exactly why it happens.
A diagram would help, but I'm at work at the mo so I ain't got no time.

Heres one
<img src=http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=4699&d=1099893902>

[Jantar]

If countersteering doesn't work, then helicopters can't fly either.[/URL]

They don't.. Helicopters are simply a machine thats trying to crash, and its only the faith of the pilot that keeps them in the air. :innocent:

[quickbuck]

They don't.. Helicopters are simply a machine thats trying to crash, and its only the faith of the pilot that keeps them in the air. :innocent:


Well, I heard it was the fact that they are so ugly that the earth repels them.

However they fly, it is a welcome sound when it is your last chance out of where ever you are.

[scumdog]

Well, I heard it was the fact that they are so ugly that the earth repels them.

However they fly, it is a welcome sound when it is your last chance out of where ever you are.
And Jim-Dandy-handy when it comes to getting a deceased out of a steep gully - like on Friday.....:yes:

Woulda been a long carry.

[terbang]

Its called Gyroscopic precession and in laymans terms it means that if you exert any sideways force on a spinning wheel, the result will be felt 90 degrees in or with the direction of rotation.
Imagine the front wheel of a bike and you are looking at it down the forks from above. Travelling along the road the top is spinning away from you. You push on the right handlebar (or pull on the left one) which is going to try to turn the wheel to the left. In effect you are exerting a force on the rear of the wheel from the left side (or the front of the wheel from the right, though its easier to visualise it on the rear). Following the above principle, any force exerted on the left rear of the spinning wheel will take effect or be felt (after 90 deg) at the left top of the wheel. This will have the tendency to roll the bike right. This is how we lean the bike using countersteer. Then it is all up to the shape or profile of our tyres to provide the turning force.

As a side issue, I often think about that poor tyre relative to the road. The axle (centre of the wheel) is travelling at the speed of the bike. The top of the tyre has to be advancing at twice the bikes speed and the bottom of the tyre (the bit touching the road) is doing 0 (Zero) speed (assuming no wheel spin). A few numbers to get the mind going on tyre forces. A sprot bike doing 300 kays requires its tyres to accelerate from "0" Kays to 600 Kays than back to "0" Kays in one revolution..!
I might be talking shit, but thats the way I see it and the physicists out there will no doubt shoot me down In flames.

[terbang]

The control force on a Helicopters spinning disk is exerted or activated 90 degrees before it is meant to take effect. This tilts the disk in the appropriate direction.

[sAsLEX]

And Jim-Dandy-handy when it comes to getting a deceased out of a steep gully - like on Friday.....:yes:

Woulda been a long carry.

You of little imagination......

A hot air balloon/or helium could of ascended the person out and then just hook that up to the F150 on a long rope and tow back to the morgue.


Or theres the more exciting way of attaching yourself via a cord to a balloon letting that go nice and high and having this fly by

<img src=http://8thattacksqdnassoc.tripod.com/Pics/mc130_49FultonSystem.jpg>

[McJim]

Well since my profession is often described as "Bean Counter" that means that at any speed - even a crawl in my driveway or in a car - park any turning I do must be a result of "Bean Counter Steering".

[Lil_Byte]

You may not believe it, but its an established physical principle coming from the gyroscope effect.
I would go into it further, but it'll need someone smarter than me to explain exactly why it happens.
A diagram would help, but I'm at work at the mo so I ain't got no time.

There is no such thing as physics - Take for example gravity - there is no such thing - it is just that the world sucks

and that is wjhat holds you down.

But anyway I was self taught at m/cycle riding - heard about that coutersteering thind and then went out and analysised what I did and it is in fact counter steering. Now that I am concious of it I have found it is easier to hold lines at reasonable speeds. :scooter:

[marty]

in relation to the axle, the speed of the tyre is the same at all points around the circumference. in relation to the road, you are correct, however the wheel doesn't care whether it's spinning in a burnout or moving along with no slippage - it's speed relative to the axle is what it cares about. i can see how you would compare that to the advancing/retreating blade on a helicopter, however that is relative to airflow, like a tyre is relative to the road therefore although relative to the centre (mast) of the helicopter the tip speed is the same, the tip speed relative to the airflow changes as forward (or rearward) speed changes. as you know, a rotor rpm of (say 300rpm) stays at that rpm in the hover, or for forward flight, so the physical speed of the tip is the same.

i need another beer

[Mr. Peanut]

E=mc^2 :sherlock:

[MattRSK]

E=mc^2 :sherlock:

Thats an ingredient in coca cola is it not?

[laRIKin]

I've been plucking up the courage to say this for a while so here goes. Countersteering is all Bullshit, its a myth perpertrated by people who have nothing better to do in their spare time. There is no way Ive ever used it in my years of bike riding so there!!!!







So I went for a ride the other day.................and I do:gob:

When I was younger I use to think that it was sort of a myth or a black art.

That was until when I was at a race meeting and I or someone else over tightened my steering dampener.

I flew in to a corner and I saw God and my miserable life go by while I pushed and pulled on the bars to try and get around that corner.
I thought that I was going to bend the bars before I got around the corner or crash.

And was made to be a believer in a nano second and never looked back after that.

Stopped backed off the dampener (old bike and could not reach it on the bike) changed undies let heart rate drop a bit big deep breaths and carried on racing.

[Skyryder]

I've been plucking up the courage to say this for a while so here goes. Countersteering is all Bullshit, its a myth perpertrated by people who have nothing better to do in their spare time. There is no way Ive ever used it in my years of bike riding so there!!!!







So I went for a ride the other day.................and I do:gob:

The mistake that many have with counter steering is that they think it is something the rider has a choice in doing.

There was a thread somewhere back where the poster wanted to know 'how' to counter steer. He/she was under the assumption that counter steering was some kind of technical method of cornering. It is not. For anyone who realy wants to put this to the test their is a quick and easy method.
Next time you are on the track go for a test ride and try and corner with your hands off the handle bars. Gyrscopic forces will prevent you from doing this to such a degree that your bike will only 'shift' to the left or the right depending on how you shift your body weight. You will not effect a safe turn.


Skyryder

[Skyryder]

Re-read his post, he does believe in it!

I did but nearly missed it.

Skyryder

[Ixion]

It had not been invented when I learned to ride, so I have never bothered with it.

I had enough trouble coping with the new inventions of my own youth like gravity, I can't be having with such new fangled stuff at my time of life.

[erik]

Countersteering isn't only due to gyroscopic effect. Compare a bike to balancing a pole on your hand (eg a baseball bat or a broom). If you want to move the pole to the left, you have to move your hand quickly to the right to get it to lean to the left, then you move your hand to the left to move the pole. To prevent it from falling over, you have to move your hand quicker than the pole, so that it goes back to a bit past vertical (leaning right slightly), and you can then slow it down and balance it at vertical again.

Same sort of thing with a bike, except that it's the front wheel's contact patch that moves from side to side (the rear wheel follows) and the bike leans.


The control force on a Helicopters spinning disk is exerted or activated 90 degrees before it is meant to take effect. This tilts the disk in the appropriate direction.

I don't think so. AFAIK the swashplate (http://en.wikipedia.org/wiki/Swashplate_%28helicopter%29) adjusts the angle of attack of the blades in alignment with the helicopter, not 90° before.


...
Next time you are on the track go for a test ride and try and corner with your hands off the handle bars. Gyrscopic forces will prevent you from doing this to such a degree that your bike will only 'shift' to the left or the right depending on how you shift your body weight. You will not effect a safe turn.


Have you ever tried turning with your hands off the bars? The steering geometry on most (all?) bikes is set up so that if you shift your weight, the bike will turn. I remember someone posting here about someone on a scooter riding it down a hill (with them as pillion) without hands, just shifting their weight.
On my bike I occasionally mess around seeing how I can corner with my hands off the bars (only just off, ready to grab them...). Have to do it going downhill though because otherwise the bike slows down too much.

[marty]

sorry erik, but countersteering is entirely due to gyroscopic precession. a broomstick as you describe has a completely different behaviour than a rotating mass. this is proven at low speed on the bike, where pulling on the right bar will induce a turn to the right, however a pull on the right bar at speed will induce a lean to the left.

and yes, the input to a swashplate on a helicopter rotor is 90deg to the desired action. have a look at a simple one like a robbie - pushing the cyclic forward (to induce a forward tilting of the disc and subsequent forward flight) will tilt the swashplate across the longitudinal axis, not the lateral axis. the result of the swashplate tilting across the longitudinal axis will be that the disc tilts across the lateral axis (tilts forward) and lo and behold, forward flight!

now don't forget, that the tilting of the swashplate only changes the angle of the blades, and the blade angle change creates the tilt of the disc - don't get confused with the swashplate tilting the disc (it doesn't).

ahh rotary theory of flight.......great fun! try explaining it to pilots!

of course, once you have acheived the mythical forward flight, don't forget torque issues, so you need rudder, then once flying forward in balance, the advancing blade has a higher lift component than the retreating blade......watch a sea king flying along - it flies on a lean!

[thealmightytaco]

Countersteering isn't only due to gyroscopic effect...

Yeah I'm with erik here, it's as much if not more about knocking the tyres contact patches out from under the centre of gravity of the bike rather than the using the gyroscopic effect.

The gyroscopic effect is the magic that keeps the bike upright and stable while you're rolling, and makes it hard to get the bike to lean because by the gyro effect the spinning wheels prevent the change of direction. Adding a slight very easy steering angle however, knocks the wheels out from under the bike and makes it lean over rather easily, as the whole bikes weight then hauls the bike down to the ground. Rather than just your fairy ass trying to stand out the side. So the whole thing topples sideways up to that place you stop counter steering, the gyroscopic effect then holding in that place as the camber thrust of the wheels hauls you around the corner. Then you gas it and steer the wheels back under the bike and it stands up.

In my humble opinion, counter steering is about shifting weight to manipulate the gyroscopic effect. Whereas the gyroscopic effect is what makes cornering such a bastard if you don't counter steer, aka the steering damper story.

[marty]

transfer the input on your bars to the axle. pulling on the right bar pulls the right axle rearward. the wheel is rotating forward (clockwise looking from the right). pulling rearward on the right axle is the same as pushing the wheel at the 9 o'clock position. gyroscopic presession will then move that input 90degrees in the direction of rotation, to the 12 o'clock position and the top of the wheel will 'fall' to the left. as the bottom of the wheel is effectively fixed to the road all of the input goes to the top of the wheel, so the action is centred on the bottom of the wheel, not the centre of the rotating mass

[marty]

In my humble opinion, counter steering is about shifting weight to manipulate the gyroscopic effect. Whereas the gyroscopic effect is what makes cornering such a bastard if you don't counter steer, aka the steering damper story.

to test this theory, ride your bike on a straight (closed) road at say, 80k. pull on the right handlebar, or push on the left one (invokes the same effect to the front wheel). do NOTHING else. do not shift any weight at all.

report back what happens to the bike.

[thealmightytaco]

transfer the input on your bars to the axle. pulling on the right bar pulls the right axle rearward. the wheel is rotating forward (clockwise looking from the right). pulling rearward on the right axle is the same as pushing the wheel at the 9 o'clock position. gyroscopic presession will then move that input 90degrees in the direction of rotation, to the 12 o'clock position and the top of the wheel will 'fall' to the left. as the bottom of the wheel is effectively fixed to the road all of the input goes to the top of the wheel.

The wheel is never fixed, and as you pull on the right the wheel steers out to the right, while the bikes COG stays put, so the bike falls over. I'm still with erik.

Tomorrow I'm going to pull a wheel off the bmx and see what happens. The wheel needs to roll over sideways when you pull one end of the axle back toward yourself for gyroscopic effect to aid in turning the bike...

[thealmightytaco]

to test this theory, ride your bike on a straight (closed) road at say, 80k. pull on the right handlebar, or push on the left one (invokes the same effect to the front wheel). do NOTHING else. do not shift any weight at all.

report back what happens to the bike.

The wheels move out from under the bike to the side while the centre of gravity of the bike stays put, hence the bike topples and I turn. I tested that out last year when I first joined this site. But I'll report on the bmx wheel test tomorrow...

[Skyryder]

Countersteering isn't only due to gyroscopic effect. Compare a bike to balancing a pole on your hand (eg a baseball bat or a broom). If you want to move the pole to the left, you have to move your hand quickly to the right to get it to lean to the left, then you move your hand to the left to move the pole. To prevent it from falling over, you have to move your hand quicker than the pole, so that it goes back to a bit past vertical (leaning right slightly), and you can then slow it down and balance it at vertical again.

Same sort of thing with a bike, except that it's the front wheel's contact patch that moves from side to side (the rear wheel follows) and the bike leans.



Have you ever tried turning with your hands off the bars? The steering geometry on most (all?) bikes is set up so that if you shift your weight, the bike will turn. I remember someone posting here about someone on a scooter riding it down a hill (with them as pillion) without hands, just shifting their weight.
On my bike I occasionally mess around seeing how I can corner with my hands off the bars (only just off, ready to grab them...). Have to do it going downhill though because otherwise the bike slows down too much.

The balancing pole thing is a pretty good way of describing the principle of counter steering. The difference being the verticle (pole) and horozontal (bike) Yes you can change direction just by shifting weight, but this is not counter steering. The change in direction is caused by off centering weight from axis and the gyoscopic force is regaining equilibreum. If the weight is off set continously from the axis there will be a continouse turn and the bike will not run in a straight line until the weight is centered inline with the bikes axis.

Someone mentioned that counter steering can be directly controlled (my words). Who ever this was I stand corrected from my earlier position that countersteering is an automatic response in cornering. This comes down to a learned cornering technique in which weight shifting and agressive steering comes into play.

I just look at where I'm going and god willing that's where I go. That's my technical advice on counter steering.

Skyryder

[terbang]

I don't think so. AFAIK the swashplate (http://en.wikipedia.org/wiki/Swashplate_%28helicopter%29) adjusts the angle of attack of the blades in alignment with the helicopter, not 90° before.



Umm wrong there mate it does. Fixed wing are not the only things I can fly. It does it 90deg before the desired reaction

[marty]

The wheels move out from under the bike to the side while the centre of gravity of the bike stays put, hence the bike topples and I turn. I tested that out last year when I first joined this site. But I'll report on the bmx wheel test tomorrow...

when the bike leans, in the absence of any other inputs (eg hands off the bars), the front wheel turns initially due to the rake of the headset, and the movement of the centre of gravity off the centreline - the c of g is acting (straight down) to one side, and the mass will want to turn towards it. as the wheel turns, it is having an input to it via the forks and subsequently the axle, and precession will begin to take place. the greater the rake, the greater the rate of turn. (with extreme rake the rake input will be much stronger than presession input) if you continue to input the lean without touching the bars, the turn radius will become tighter and tighter. if you halt the lean (you will have to actually lean back to overcome/equal precession, the turn rate will stabilise.

[terbang]

Tomorrow I'm going to pull a wheel off the bmx and see what happens. The wheel needs to roll over sideways when you pull one end of the axle back toward yourself for gyroscopic effect to aid in turning the bike...


Didn't you do that one in your physics lessons at school. Believe me it will behave 90 deg to what you think it will.
I'm with Marty on this one. It is only Gyroscopic precession that rolls or leans the bike when countersteering.

[terbang]

Ok if the bike had flat profile wheels or rollers like a road roller (or a cage for that matter) rather than profiled motorcycle tyres then how would it turn..?

[marty]

The wheel is never fixed, and as you pull on the right the wheel steers out to the right, while the bikes COG stays put, so the bike falls over. I'm still with erik.

Tomorrow I'm going to pull a wheel off the bmx and see what happens. The wheel needs to roll over sideways when you pull one end of the axle back toward yourself for gyroscopic effect to aid in turning the bike...

the bottom of the wheel is essentially running in a fixed plane on the road - it doesn't slide sideways (unless you're in the shit).

hold the bmx wheel in 2 hands vertically (although a vertical gyroscope has the axis in the vertical, and actually spins in the horizontal plane) in front of you, and i guarantee the top of the wheel will move to the left, when you pull the axle rearwards, which is the same as inputting to the wheel (the rotating mass) with a push from the right (by your chest)

[M1CRO]

They don't.. Helicopters are simply a machine thats trying to crash, and its only the faith of the pilot that keeps them in the air. :innocent:

sounds like an advocate for quantum mechanics :rockon:

[M1CRO]

the bottom of the wheel is essentially running in a fixed plane on the road - it doesn't slide sideways (unless you're in the shit).

hold the bmx wheel in 2 hands vertically (although a vertical gyroscope has the axis in the vertical, and actually spins in the horizontal plane) in front of you, and i guarantee the top of the wheel will move to the left, when you pull the axle rearwards, which is the same as inputting to the wheel (the rotating mass) with a push from the right (by your chest)

When you try this, consider this concept
By the wheel turning, your changing the circumference of the turning front wheel. Grab a paper cup (one where the base has a different diameter than the end you drink from), and try rolling it on the ground.. Ask the question, why it doesnt go in a straight line? and you will start to get some better insight into it... Otherwise, come to the RRRS course!!

[laRIKin]

Counter steering does not so much turns the bike around the corner.
It makes the bike lean over in to the corner so you can go around it.
It is used more to start the turn and finish a turn.
You only use it to change the (lean) angle of the bike.

I think that you use the gyroscopic effect of the front wheel to push against (a bit like a wall or a lever) to push the bike down in to a corner or to get the bike back up to vertical.

Other wise when you have your knee down, it would be impossible to counterbalance the bike up right again as you are way passed the point of balance.
That is unless you can lean your body passed the vertical point to get the bike to stand up again. (I would like to see that)

When you just lean a bike in to a corner (with out hands off the bars) the wheel turns the the way you want to go, but you will not be leaning the bike over as much, but will still go around the corner, but not as fast.
Because if you go passed the point of no return you will not be-able to straighten up the bike again.

[Jantar]

When you try this, consider this concept
By the wheel turning, your changing the circumference of the turning front wheel. Grab a paper cup (one where the base has a different diameter than the end you drink from), and try rolling it on the ground.. Ask the question, why it doesnt go in a straight line? and you will start to get some better insight into it... Otherwise, come to the RRRS course!!

In order for the cup (or any decreasing radius surface) to remain in contact with the floor, there must be sufficient force to keep the surface in contact with the ground (ie to overcome the gyroscopic effect.)

Watch what happens at that strange sport called bowls. The bowler can get the bowl to turn in without counter sterring because of two seperate effects. First there is a weight bias which causes the bowl to want to lean in the direction of the turn, (like leaning a bike) then there is the shape of the bowl which causes the surface to have a different profile as it leans more (like your paper cup). Counter steering helps with the weight transfer, and tyre geometry helps with the right profile.

[laRIKin]

This is the short version.

http://www.vf750fd.com/blurbs/counter.html

Countersteering works by moving the wheels out from under the bike.

Try this experiment: Balance a broom upside down on your finger. With a few minutes' practice you can keep it upright pretty effectively. Once it's reasonably stable, try moving it to the left. You'll quickly find that for the broom to move to the left, it must be leaning to the left. You do this by moving your finger to the *right*, which moves the end of the broom handle out from under the center of mass of the broom. This is exactly the same mechanism as countersteering. Your bike has some inherent stability when it's moving, which will tend to keep it upright. When you want to turn, you must lean the bike.

Countersteering moves the wheels out from under the center of mass of the bike, causing it to lean in the opposite direction. Gyroscopic precession has little bearing on countersteering. It does have a significant effect on the feel of the bike, since it tends to keep the front wheel from being turned. However, consider this: If gyroscopic precession were the primary driving force in leaning the bike, one would expect that bikes with large front wheels would turn in very quickly. As it turns out, though, this is not the case, and in fact is just the opposite of what is seen in actual practice.

Once the bike is leaned over, the trail of the front end causes the front wheel to turn into the curve, and the round profile of the tires causes the bike to experience camber thrust steering (similar to rolling a cone, which travels in a curved path), which cause the bike to go around the curve. When it's time to straighten out, countersteering is again used, this time to move the wheels back underneath the center of mass of the bike and cause it to stand up.

[erik]

...and yes, the input to a swashplate on a helicopter rotor is 90deg to the desired action....

Umm wrong there mate it does. Fixed wing are not the only things I can fly. It does it 90deg before the desired reaction
Damn, you're right about the swashplate.
http://science.howstuffworks.com/helicopter6.htm
http://en.wikipedia.org/wiki/Precession

It'd be nice to be right for a change, but I'd rather learn where I'm wrong than continue to be wrong, so cheers.


I still think I'm right about countersteering though...


The balancing pole thing is a pretty good way of describing the principle of counter steering. The difference being the verticle (pole) and horozontal (bike)
The bike isn't horizontal, it's like a vertical pole except because it's got two wheels, it can only fall over sideways, not forwards and backwards as well (like a pole would).


the bottom of the wheel is essentially running in a fixed plane on the road - it doesn't slide sideways (unless you're in the shit).
It doesn't have to slide sideways, it tracks sideways when you turn the bars due to forward motion of the bike. The same way that a car's front wheels track right when they turn right.

I found this article:
http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics

which I haven't seen before and haven't fully read now, I'm a bit tired and feel like I've been staring at the screen too much. But it seems to support the idea that motorcycle (and bicycle) steering isn't exclusively due to gyroscopic precession.
Here's one quote from the article:
"If the steering of a bike is locked, it becomes virtually impossible to ride, but if the gyroscopic effect of rotating bike wheels is cancelled by adding counter-rotating wheels, it can still be easily ridden."


Cheers for the above post, lemans, that explains it clearly :)

[marty]

how does rotating a wheel change its circumference? the only thing that changes is its static mass becomes dynamic. it is that dynamic rotating mass that involes the gyroscopic precession. GP does not apply to a wheel at rest.

the paper cup turns because it has circles of different diameter, and it will always turn towards the smaller diameter. it has nothing to do with gyroscopic precession.

what's an rsss course?

here's a question for you. get a roll of 2" masking tape. roll it quite quickly on a smooth concrete floor. 1 - it won't roll in a straight line for long. 2 - when it starts to turn, it rolls on the OUTSIDE edge - for instance, if it's turning left, it will be rolling on the right edge. why is that?

[M1CRO]

...what's an rsss course?...
Read about it here (http://www.kiwibiker.co.nz/forums/showthread.php?t=28643)...

[marty]

Watch what happens at that strange sport called bowls. The bowler can get the bowl to turn in without counter sterring because of two seperate effects. First there is a weight bias which causes the bowl to want to lean in the direction of the turn, (like leaning a bike) then there is the shape of the bowl which causes the surface to have a different profile as it leans more (like your paper cup). Counter steering helps with the weight transfer, and tyre geometry helps with the right profile.

exactly - the bowl turns toward the centre of gravity. the bowl wants to go straight ahead, and it will if the speed of the bowl is high enough, but the c of g forces at lower speed will tend to turn the bowl towards that force. the same if you lean your bike without touching the bars - the bike's c of g acts straight down, but now instead of acting through the wheels, it acts vertically down to a point inside the turn, and the bike turns towards it.

[marty]

Read about it here (http://www.kiwibiker.co.nz/forums/showthread.php?t=28643)...

thanks.......

[rwh]

The wheels move out from under the bike to the side while the centre of gravity of the bike stays put, hence the bike topples and I turn. I tested that out last year when I first joined this site. But I'll report on the bmx wheel test tomorrow...

Agreed. I tried out the bike wheel this afternoon (bike already conveniently in bits), and was quite surprised how strong the precession was - but I'm not convinced it could do the whole job. Especially since I'm sure countersteering would still work fine on one of those little pushalong scooters with 10cm wheels; those wheels won't have enough mass to tip me over.

I'm not saying the gyroscopic effect has nothing to do with it; I'm just not convinced it's the whole deal.

Essentially - I think I agree with erik. I was going to try to explain it, but he did so much better with his balancing broomstick.

Richard

[Jamezo]

Yeesh guys, I thought that this had been cleared up many times before.

The precession force acts in OPPOSITION to the change in angle of the bike.

The input to the bars changes the position of the contact surface of the wheel in relation to the movement of the bike, and sets up the rotational force.

The turning itself is a direct consequence of the angle of the bike.

[Mr. Peanut]

Wen ai tern tha handul baas tha boike gows otherwheres :yes:

EDIT :

E=mc^2

[marty]

Agreed. I tried out the bike wheel this afternoon (bike already conveniently in bits), and was quite surprised how strong the precession was - but I'm not convinced it could do the whole job. Especially since I'm sure countersteering would still work fine on one of those little pushalong scooters with 10cm wheels; those wheels won't have enough mass to tip me over.


Richard

the fastest you could get you bmx wheel up to by spinning would be 10kmh. times that by 10, then tell me the force wouldn't be enough

[marty]

and i respectfully suggest your broomstick comparison is irrelevant, as the experiment, if done on a stationary bike (eg pull on the right bar) will not invoke a precessed response. the gyro (the wheel) is what makes the difference. if it is not spinning, it is not a gyro.

do some reading on fixed gyros. the front wheel of a bike is a horizontal fixed gyro

[Motig]

Sorry, I should have put this topic in the 'Scientific Anylasis' Forum.

[terbang]

When we drive around a carpark at 10 kays or less we can drive the thing like a car. Same as when you are pushing it around yer garage. Turn bars right, bike turns right. We all know that don't we..? We also all know (with out really thinking about it) that as we get faster we can't steer it like a car anymore and have to lean the thing to make it turn. So whats the difference between the slow and the not so slow..? Its gyroscopic force along with its precession properties. Simple really.

[terbang]

Counter steering does not so much turns the bike around the corner.
It makes the bike lean over in to the corner so you can go around it.
It is used more to start the turn and finish a turn.
You only use it to change the (lean) angle of the bike.

I think that you use the gyroscopic effect of the front wheel to push against (a bit like a wall or a lever) to push the bike down in to a corner or to get the bike back up to vertical.

Other wise when you have your knee down, it would be impossible to counterbalance the bike up right again as you are way passed the point of balance.
That is unless you can lean your body passed the vertical point to get the bike to stand up again. (I would like to see that)

When you just lean a bike in to a corner (with out hands off the bars) the wheel turns the the way you want to go, but you will not be leaning the bike over as much, but will still go around the corner, but not as fast.
Because if you go passed the point of no return you will not be-able to straighten up the bike again.

Bingo.. Countersteer doesn't turn the bike it only controls the bike in a lateral sense. In simple words it is the roll control and we lean the bike and mnaintain a lean angle with it. The turning force (centre seeking force) is now provided by the tyre which is in effect a segment of a cone (someone mentioned a paper cup before).

[marty]

Sorry, I should have put this topic in the 'Scientific Anylasis' Forum.


at least the sun's shining where i am :)

[erik]

The broomstick example is supposed to demonstrate that when you try to accelerate the broom in one direction, it has to be leaned in that direction first otherwise it'll topple over.
When you ride a bike around a corner, it is accelerating towards the centre of the curve (centripetal acceleration). To avoid from toppling over (out of the corner), it has to be leaned into the curve.

The broomstick example also demonstrates that to get the broom to lean in one direction, you have to move the base briefly in the opposite direction.
Ignoring gyroscopic effects on a bike, turning the front wheel to the right would make the contact patch of the front tyre track to the right (if the bike is moving forwards) and the bike would start to lean towards the left, ready to turn in that direction.

This still holds true at low speed, if you turn hard to the right, the bike will tip to the left (depending on how much trail the bike has and how hard you turn...). You still have to balance the bike.

I know how a gyroscope works (I've got a toy one sitting on my desk). I'm not saying gyroscopic precession doesn't play a part in a bikes handling. At high speed for all I know it might be the main force that controls how the bike leans. It might come into effect before the front wheel has a chance to track to the side.
But it's confusing for me that you can't see that when you turn the bars to the right, the wheel will track to the right under the bike, and the bike will lean left.
I intend to do some reading over summer to get a better grasp of motorcycle dynamics.

Appologies for hijacking your thread, Motig ;)

[Motig]

Not a problem. Suns shining here too!

[terbang]

turning the front wheel to the right would make the contact patch of the front tyre track to the right (if the bike is moving forwards) and the bike would start to lean towards the left, ready to turn in that direction.

Turn the bars right and the tyre contact point, due to the trail, shifts to left of the bikes centreline.

[marty]

But it's confusing for me that you can't see that when you turn the bars to the right, the wheel will track to the right under the bike, and the bike will lean left.
;)

this is not what happens erik. when you pull on the right bar while the wheel is rotating at speed, the input that you have done, due to GP, effectively 'pushes' the top of the front wheel over to the left. the bottom of the tyre is 'fixed' to the road, so the point of rotation of the gyro (the wheel), instead of rotating about its axis, is about that 'fixed' point on the road. the wheel does not track to the right at all, otherwise the bike would initially turn/drift to the right.

i've got some really good books on gyro theory - essential reading for helo engineers, and general aircraft engineers (which is what i do)

[Skyryder]

The bike isn't horizontal, it's like a vertical pole except because it's got two wheels, it can only fall over sideways, not forwards and backwards as well (like a pole would).

Call me pedantic but this needs a correction. The balancing pole is to all intents and purposes stationary with one point of contact. It is vertical.

The bike has two ponts of contact. This changes the equation from vertical to horozontal. Both are affected by gravity and fall downward

A uni cycle would be in the same catogory as the pole with a single contact point.

I agree that Le Mans stated the definitive answer to this question that counter steering occurs at the first level of turning. It iniates the turn.

Skyryder

[Jamezo]

EDIT: This is in response to MartyB

Wrong wrong wrong wrong wrong.

I'm assuming you are quite well versed in gyroscopic theory, so this'll be easier.

Assume, for the moment, that the force that leans the bike and wheel over does not come from a precession force:

Now we have a forwards-rotating wheel, being made to turn - for different reasons - sideways.

You understand, correctly, that a force applied to a gyroscopic object produces a torque in a plane 90 degrees advanced in the plane of the axis of rotation.

So consider the force that is making the wheel tip sideways, say left. Rotated in the plane of the axis of rotation by 90 degrees, this looks like a counter-clockwise torque.

Note that this is in opposition to the clockwise counter-steering input that you would be applying to turn the bike left!

For the actual matter of what causes the sideways movement, you'll have to look back at the actual contact forces involved. Check out http://www.rider-ed.com/tips/motorcyclestability.htm or something.

Note that the opposition precession force is always less than the input required to affect a turn, or else you'd never be able to turn!

This is also why that guy with the counter-rotating rotors is onto the right idea; the precession force is NOT what steers the bike, it is a damping influence on the rate of rotation.

[vtec]

Here's an idea to simplify it for marty.

Try imagining riding a motorcycle with the latest high tech carbon fibre kevlar wheels. And just imagine for theory's sake that the wheels on the bike weigh absolutely nothing. Now this gets rid of ALL of the gyroscopic effects from the wheels. Now, when you are riding this bike at say 100k/hr, will you still countersteer to lean the bike and maintain the lean? Of course you will. Gyroscopic precession is a factor, but not the main one.

It's a combination of castor angle and the geometry of the tyres (and momentum in one direction) that makes the bike want to stand up (at high speeds).

Unless I'm missing something gyroscopic effects merely resist changing of angle. Once that angle has changed, this becomes the new angle at which the gyroscopic effect will resist movement from.

At low speeds, you still have to do the balancing act to turn the bike, if you want to go right, you have to move the wheels left underneath you so that the bike leans to the right. This happens at all speeds, but can be negated by putting your feet on the ground. However the dynamics of the bike at low speeds will mean that if you are leaning it, it will want to fall over, so you have to put in opposite force to normal countersteering to get it to maintain a lean angle at low speeds. So as Jamezo said, it initiates the turn, but at high speeds you need to keep countersteering to maintain the turn due to the bike wanting to straighten up and this is caused by the increased momentum of the motorcycle combined with the castor angle and the tyre geometry, and partially gyroscopic effect.

And erik's example of the broomstick is still useful if not perfect. Balancing a bike is actually more simple than a broomstick as you only have one axis of leaning to correct for by countersteering the wheels underneath you.

Another example is those remote control motorbikes. The wheels on those weigh next to nothing, and they want to straighten up once over about 5k/hr, this is due to the castor angle and tyre geometry, and next to nothing to do with gyroscopic precession, as the wheels weigh next to nothing, and have a tiny radius.

[Jantar]

Here's an idea ...
Try imagining riding a motorcycle with the latest high tech carbon fibre kevlar wheels. And just imagine for theory's sake that the wheels on the bike weigh absolutely nothing. Now this gets rid of ALL of the gyroscopic effects from the wheels. .
It also makes the bike impossible to ride. What do you think keeps the bike from tipping over? It surely isn't the rider's remarkable sense of balance.

[vtec]

It also makes the bike impossible to ride. What do you think keeps the bike from tipping over? It surely isn't the rider's remarkable sense of balance.

The castor angle and momentum of the bike, combined with tyre geometry.

http://en.wikipedia.org/wiki/Caster_angle

Have a good read in there, they even discuss motorcycles.

Edit: it seems that these articles have more info
http://en.wikipedia.org/wiki/Countersteer
http://en.wikipedia.org/wiki/Rake_and_trail

P.S. Rake and trail is similar to castor angle, but the Rake and trail article is way more relevant to this discussion. That is what explains why a bike wants to straighten up at speed.

[Jantar]

Sorry, but very early bikes had square profile tyres, and many had the castor angle buil out so that there was none. Castor angle and tyre profile are two of the components of bike steering stability, but have almost no effect on balance.

[Pieyed]

I guess everyone looked outside and saw the sun and went for a ride to test their theories:sunny: Tui.

Been for a ride today and only wet at the begiinning and the end.

[marty]

Here's an idea to simplify it for marty.

Try imagining riding a motorcycle with the latest high tech carbon fibre kevlar wheels. And just imagine for theory's sake that the wheels on the bike weigh absolutely nothing. Now this gets rid of ALL of the gyroscopic effects from the wheels. Now, when you are riding this bike at say 100k/hr, will you still countersteer to lean the bike and maintain the lean? Of course you will. Gyroscopic precession is a factor, but not the main one.

It's a combination of castor angle and the geometry of the tyres (and momentum in one direction) that makes the bike want to stand up (at high speeds).

Unless I'm missing something gyroscopic effects merely resist changing of angle. Once that angle has changed, this becomes the new angle at which the gyroscopic effect will resist movement from.

At low speeds, you still have to do the balancing act to turn the bike, if you want to go right, you have to move the wheels left underneath you so that the bike leans to the right. This happens at all speeds, but can be negated by putting your feet on the ground. However the dynamics of the bike at low speeds will mean that if you are leaning it, it will want to fall over, so you have to put in opposite force to normal countersteering to get it to maintain a lean angle at low speeds. So as Jamezo said, it initiates the turn, but at high speeds you need to keep countersteering to maintain the turn due to the bike wanting to straighten up and this is caused by the increased momentum of the motorcycle combined with the castor angle and the tyre geometry, and partially gyroscopic effect.

And erik's example of the broomstick is still useful if not perfect. Balancing a bike is actually more simple than a broomstick as you only have one axis of leaning to correct for by countersteering the wheels underneath you.

Another example is those remote control motorbikes. The wheels on those weigh next to nothing, and they want to straighten up once over about 5k/hr, this is due to the castor angle and tyre geometry, and next to nothing to do with gyroscopic precession, as the wheels weigh next to nothing, and have a tiny radius.

i never said GP had anything to do with keeping the bike upright. gyrosopic rigidity aids in keeping the bike upright, but it's mostly balance of the rider.
gyroscopic rigidity resists turning, but GP aids it.

and i'm imagaining, and i've imagined a ski doo on the snow. it's as close to your theoretical weigh nothing wheel. try pulling the right handlebar to go left. it won't.

[vtec]

Sorry, but very early bikes had square profile tyres, and many had the castor angle buil out so that there was none. Castor angle and tyre profile are two of the components of bike steering stability, but have almost no effect on balance.

Don't apologise. I'm guessing that square profile tyres are fine for the mud tracks that very early bikes had to deal with, but they wouldn't be suitable for concrete or tarseal at anything over 20k/hr.

And you can't tell me that a bike with no castor angle was a brilliant handling self balancing wonder, because it just would not be true. No castor angle, would mean that ALL of the balancing would be done from rider input. Doable, but not fun.

Think of it this way. When you lean a bike with a castor angle, it puts sideways force on the patch of the wheel that touches the ground in the upwards direction. This patch of tyre is behind the line of the front forks meaning that it will effectively push the bars in the direction opposite to countersteering which is why you need to countersteer to get the bike to lean back down. So castor angle does affect the balance of the bike.

[vtec]

i never said GP had anything to do with keeping the bike upright. gyrosopic rigidity aids in keeping the bike upright, but it's mostly balance of the rider.
gyroscopic rigidity resists turning, but GP aids it.

and i'm imagaining, and i've imagined a ski doo on the snow. it's as close to your theoretical weigh nothing wheel. try pulling the right handlebar to go left. it won't.

Using a ski doo is completely different from my example, cause they are wide enough that you don't need to balance them, this doesn't affect any of the arguments... That's almost like trying to use a car as an example... pointless with regards to countersteering a motorbike... go back to using my example of the weightless wheels, and try to imagine what would happen.

The fact that the bike wants to straighten up is the reason why you need input from the rider in the form of countersteering to get it to lean back down, so effectively in saying that the gyroscopic precession doesn't make the bike want to stand up, you are saying that it's not what makes the rider need to countersteer.

Edit: Also note you stated that the bike is kept upright by the balance of the rider? This is wrong, the bike is kept upright by the castor angle mostly, of the bike when it is at speed. You can affect it by either countersteering or moving your weight to either side, so that the castor angle effect is overcome to a certain degree.

[terbang]

Here's an idea to simplify it for marty.


Umm no you are complicating it for yourself. Marty is correct it is Gyroscopic precession that produces the rollng motion on the bike.
Other features such as trail and gyroscope rigidity help to make the bike stable (there is a difference between control and stability). But the rolling motion toward or away from any lean angle or adjustment of lean angle is primarily a result of Gyroscopic precession. Thats what countersteering does and we all use it whether we are aware of it or not.

[terbang]

Edit: the bike is kept upright by the castor angle mostly, of the bike when it is at speed. You can affect it by either countersteering or moving your weight to either side, so that the castor angle effect is overcome to a certain degree.

Not correct. Caster angle and trail are there for directional stability. It is gyroscopic rigidity that keeps the bike upright when moving and the side stand that does it when it is stationary.
However this discussion is not about stability it is about countersteering which is control..

[vtec]

Not correct. Caster angle and trail are there for directional stability. It is gyroscopic rigidity that keeps the bike upright when moving and the side stand that does it when it is stationary.
However this discussion is not about stability it is about countersteering which is control..

Not Correct. Gyroscopic rigidity merely maintains a rotating objects direction and angle. Which would mean that if you leaned it down, it would stay down, not straighten up. There is other forces at play that cause it to straighten up.

A good example is like comparing it to a suspension component. The Gyroscopic rigidity acts like the dampener, and the caster angle acts like the spring in a rear shock. Only difference is that the shock works only up and down, whereas caster and GR act from left to right on both sides of the bike.... Try going at low speeds and you will notice that it is very easy to flick the bike from side to side, and at a certain speed it will oscillate from side to side, that is the caster angle acting like a spring without any dampening from the GR, at high speed with GR, the steering will get harder and harder to turn, and nearly impossible to flick from side to side, this is because both the GR effect and the caster angle effect increase greatly at speed. It's like turning up the dampening and the springrate heaps in your rear shock.

This discussion is relevant, because it is discussing the reasons behind why you need to countersteer a bike.

[MacD]

This is the short version.

http://www.vf750fd.com/blurbs/counter.html

Countersteering works by moving the wheels out from under the bike.

<snip>

Once the bike is leaned over, the trail of the front end causes the front wheel to turn into the curve, and the round profile of the tires causes the bike to experience camber thrust steering (similar to rolling a cone, which travels in a curved path), which cause the bike to go around the curve. When it's time to straighten out, countersteering is again used, this time to move the wheels back underneath the center of mass of the bike and cause it to stand up.

I'm lining up with Lemans and Jamezo on this one. The gyroscopic effect of the spinning wheel has much less effect on riding than people claim. Bikes have been built with counter-rotating wheels-within-wheels to cancel the gyroscopic effect and they still behave much like an ordinary bike.

Countersteering does momentarily move the front wheel out of line, as would be expected by the process of rotating the bars in the opposite direction to your intended turn. It is a useful technique for avoiding small objects on the road as you can kick your front tyre out and around the object with a countersteer input. The bike starts to roll and the front wheel returns to the appropriate track for the turn. Turning results from what people have termed camber thrust (the rolling cone idea) and slip angle (how much your tyres effectively slip across the road during the turn).

Anyhow, engineers actually study and model this stuff (Imperial College London (http://www3.imperial.ac.uk/controlandpower/research/portfoliopartnership/projects/motorcycles/)) and write review papers on it (public download of manuscript (http://www3.imperial.ac.uk/portal/pls/portallive/docs/1/6963908.PDF)).

See around p14 for a discussion of gyroscopic forces and p17/18 for torque steering/countersteering.

Personally I believe the bike stays upright and the world leans, but that's just me! ;)

[Jamezo]

Further summary:

Precession forces only play a damping role when the bike is rolling. The way the 'gyroscopic inertia' manifests itself is through the counter-torque on the bars.

Physics wins yet again! Interesting stuff MacD.

[erik]

Turn the bars right and the tyre contact point, due to the trail, shifts to left of the bikes centreline.
That's true when the bike is stationary.


...the wheel does not track to the right at all, otherwise the bike would initially turn/drift to the right....
The stuff I've read and my understanding of it says the wheel does track to the right. A video of a bike riding along a straight line toward a camera would prove/disprove this.


Not correct. Caster angle and trail are there for directional stability. It is gyroscopic rigidity that keeps the bike upright when moving and the side stand that does it when it is stationary.
However this discussion is not about stability it is about countersteering which is control..

That's not true. Here is a quote (from http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics )

"...if the gyroscopic effect of rotating bike wheels is cancelled by adding counter-rotating wheels, it can still be easily ridden."

The links posted that I've looked at have supported the idea that the front wheel tracks sideways under the bike to get it to lean. If you're still disagreeing with that after what's been posted and after reading the links, I don't think I can say anything else that's going to sway your opinion.

I think I'll have to video a bike at some point to confirm that the wheels to track right before it turns left, I think that's the only thing that will settle this. But it'll have to wait till after my exams.

Cheers to all who contributed both sides of the argument, it's an interesting thread. :)

[terbang]

OK here are a couple of fairly good articles about turning a bike:

Extract from "A Twist of the Wrist Vol II"
There are two gyros, so which one of them does what? Which end actually steers the bike? The front, right? Yes and no.
According to a number of technical reasons, laws of physics* and
engineering principles, the following is true: As long as you apply force to
the bars, the bike continues to lean further over. However, once the bike
is fully leaned into a corner, the rear end "steers" the machine. The
front-end "turns" the bike or changes lean angle but the moment the
motorcycle is leaned over and stable, the main mass of the bike -from
steering head back- determines the lean angle it will hold.


Extract from an accident prevention program in the USA:
The physics of motorcycle dynamic response to rider control input is well established. Theoretical as well as empirical studies have clearly established that a motorcycle steers in response to the rider input of a countersteer torque which causes a directional change (opposite to the countersteer) of the motorcycle. The rider inputs a countersteer and through a combination of inertial, geometric and gyroscopic effects, the motorcycle responds and begins the cornering maneuver. A brief discussion is presented but it is not the intention of the present research to derive these well established relationships in detail.
The inertial and geometric effect can be understood by examining the rider steer input during the corner entry maneuver. When faced with a desired left turn, the rider applies a clockwise torque (left bar push – clockwise headset rotation) at the handlebar which causes the front tire to steer to the right. This generates a lateral force at the front tire contact patch which causes a yaw response of the motorcycle to the right (clockwise when viewed from above). This results in roll motion to the left due to the inertial forces acting at the center of mass. This roll to the left, combined with the rider’s ubsequent steering to the left, directs the motorcycle in the desired left turn direction. This effect is easily seen when negotiating large radius turns where the desired directional change can occur over a long distance. Because of inertial characteristics, this effect (causing a lean) has a time delay when compared to the more rapidly responding gyroscopic effects.
The gyroscopic effect occurs whenever the axis around which a body is rotating is itself rotating around another axis. In the context of motorcycle directional change, the rider inputs a steering torque which causes the rapidly spinning front wheel to undergo a precession. This precession causes the motorcycle front tire to lean in the opposite direction of the rider initial steering torque input. This applies a roll moment to the motorcycle through the steering head and causes the entire motorcycle to lean in the desired turn direction. For example, a rider steer input to the right would cause the wheel to lean over to the left which contributes to the motorcycle desired lean into a left hand corner. When entering high speed turns, the gyroscopic effect is readily seen. Additionally, the gyroscopic response is present immediately after the rider initial steer input resulting in a rapid lean in the desired turn direction.

As a long time believer that it was purely Gyroscopic precession that was the only method I will concede and accept that there is another. However, I do still believe that the primary is Gyro for control. tThis lies comfortably with the Twist of the Wrist statement that the front wheel steers the bike (control) and the rear wheel turns it.

[thealmightytaco]

I forgot all about this game! And I wont get to do it tonight either, but sometime.


Didn't you do that one in your physics lessons at school. Believe me it will behave 90 deg to what you think it will.
I'm with Marty on this one. It is only Gyroscopic precession that rolls or leans the bike when countersteering.

No kidding, but when you've got 3 axis, which 90 deg? I know if you roll it over you will spin on your chair, but if you pull on it will it do the same? It's a different vector change...

(15 mins later...)

Bastard.

Lets say x and z are your left-right and forward back axis, and y is your up-down:
If you spin a wheel, holding the axle along x, and try to turn it about z, (unless you act further upon it) it will roll about y.
In other words, when you counter steer, steering out the right, the wheel will roll the bike over to the left.

Marty and co. are right in the gyroscopic effect aiding the turn.

BUT I still think the falling broomstick effect plays a part. Might try find the radius of gyration and weight of your average wheel and crunch some numbers and see how much each effect plays in the turning of a corner. Just so I know.

I must concede though, most humbly, that the gyroscopic effect would lean the bike over all on it's own if given the chance.

[thealmightytaco]

And I just saw terbangs last one... I'm feelin' it now.

[Jamezo]

I don't think there's any chance of saving you lot, so I'll guess I'll just let you live out your delusions, meanwhile the man with the impossible (according to your interpretation) contra-rotating motorcycle is laughing his arse off, and a broomstick falls in the woods with nobody to hear it....

PS. That broomstick idea stuff was a load of shite.

[Ixion]

Struth. I'm glad I started riding before all this stuff was invented.

But - a question
As I understand what people is sayin :

If you have a rotating mass (ie wheel) , and you turn it to the left (via the bars) , it will make the wheel lean over at 90 degrees to the turn - ie , bank to the right. I remember enough high school physics to go along with that.

Initiate turn to right, wheel (and thus bike) banks over to left. Then the axle line and wheel form a truncated cone, so the bike rolls around that and turns the corner.

Well and good.
But : this works for cruisers too, right ? I'm sure it does. And given that a crusier has tyres as wide and big (and nearly as flat) as , say, a Morrie Minor, why doesn't the same thing happen when you turn the wheel of the Morrie to the left (via the steering wheel) . Morriis wheel is rotating too, is as big and heavy as a bike wheel. Why doesn't turning the Morrie wheel(s) to the left cause the car to bank over and head right ? Or does it?

[terbang]

I guess its because its got 4 wheels..!

But I reckon if you were to get an old morrie up to say, 160 kays (down a really really steep hill) and then wracked the steering over to the right. I suspect you may find some sort of roll to the left.

[MacD]

Struth. I'm glad I started riding before all this stuff was invented.

But - a question
As I understand what people is sayin :
<snip>

Well and good.
But : this works for cruisers too, right ? I'm sure it does. And given that a crusier has tyres as wide and big (and nearly as flat) as , say, a Morrie Minor, why doesn't the same thing happen when you turn the wheel of the Morrie to the left (via the steering wheel) . Morriis wheel is rotating too, is as big and heavy as a bike wheel. Why doesn't turning the Morrie wheel(s) to the left cause the car to bank over and head left ? Or does it?

I bet if you got the Morrie up on two wheels via a ramp it would behave exactly as a bike does, in other words you'd use countersteering to alter the roll attitude and therefore control how it turns.

[marty]

i think you will find that there is still GP at work on your morrie, however the axle is fixed in the horizontal plane, and the force of the steering arm overcomes the force of the GP. if you took the wheel off, and spun it like a bmx wheel, you would experience the black magic......

[Hillbilly]

Here's some more on the subject:


Leaning by applying a gyroscopic force
Gyroscopic effect also plays a role in banking a motorcycle. When a torque application tends to modify the plane of rotation, gyroscopic effect produces a rotation whose axis is perpendicular to the axis of the applied torque. By turning the handlebar to the left, gyroscopic effect of the front wheel causes the motorcycle to bank to the right with respect its roll axis. Likewise, a turn of the bar to the right will instigate a lean to the left. We have examined two methods of changing the direction of a motorcycle and in both cases the initial input at the handlebar must be in the direction opposite to that desired. Happily, the effects of these two methods work in concert. They could have worked in opposition such as in the hypothetical case in which the rear wheel pivots to provide steering.

Definition of countersteering
If countersteering of a motorcycle consists of orienting, for a brief moment, the front wheel in a direction opposed to that in which one desires to go, then countersteering is the source of all significant changes of direction.There exist certain types of controllable single-track vehicles which make no use of gyroscopic effect (with blades, with skis, automobiles cornering on two wheels, two wheels with counter-wheels).

Justification of the term countersteering
The term countersteering is perhaps poorly chosen. While in automobile driving it describes a procedure for recovering from a skid, in motorcycling it refers to a procedure of initiating or creating a change of direction. Perhaps a less ambiguous term is needed.It is possible to ride a motorcycle safely over a long period without even being aware of this characteristic. Several motorcyclists who have not been exposed to recent rider training courses completed this operation successfully without being aware of it, as are the majority of bicyclists.This procedure of countersteering is taught in rider training courses as a technique for avoiding a sudden obstacle. Often, the student discovers for the first time the necessity to turn the handlebar momentarily in the opposite direction to the one desired. Certain students continue to believe that countersteering is valuable only for obstacle avoidance. The test of the Société de l’Assurance Automobile du Québec (SAAQ) for a motorcycle operator’s licence contains a specific evaluation of this manoeuvre.


There are also some pics as well...

[Ixion]

Well, maybe. But has anyone ever experienced having a car go left when you turn the wheel to the right ?

[MacD]

OK, one last attempt at convincing the disbelievers that gyroscopic forces, while present, are not essential for, or the primary cause of turning in bikes when countersteering.

From: J Fajans, (2000). Steering in bicycles and motorcycles. Am. J. Physics 68(7): 654-659.


"Figure [3](d) shows the contributions of the trail torques and of the gyroscopic torque to changing the steering angle. While the gyroscopic torque is non-negligible, it is much smaller than the trail torques and somewhat smaller than the handlebar torque. Thus, in accord with Jones' observation that a bike equipped with a gyro nulling counter-spinning wheel behaves much like a normal bicycle, the "feel" of the bike is dominated by trail"

"Contrary to the assertion in reference 3, gyroscopic action plays no role in leaning the bike. However, as shown in Figure 3(d), and in agreement with reference 3, it does play a role in steering the front wheel back towards the desired direction"

"In any event, gyroscopic forces play little role in leaning the bike over, though they do help set the steering angle. The appealing notion that gyroscopic forces are central to bike behaviour, often repeated in papers and textbooks, is incorrect"



So, gyroscopic forces stabilise a bike in straight line travel, but are not necessary for turning. They do aid the recovery from a turn, but other forces produced by the trail setup and rotation are significantly larger when initiating a turn.

Believe it or not! ;)

[marty]

i have still yet to see whether the opposing gyro (at speed) negates the pulling on the left bar to instigate a right turn. i have only seen that it makes the push bike handle in a straight line in a similar fashion. someone please link me....

and the graphs do not appear to nominate the trail - we all know that a steeper headset tends to mean a quicker turn-in, likewise a chopper-style headset means the wheel literally falls in - we're not disputing that. what if the headset was vertical?

[terbang]

I'm sure you see this in the Pitts Marty. Used to tow gliders in cubs (1978). ZK-BOV appears in my logbook along with ZK-BPE at that time. They were PA18A models, lyc 320 powered and swinging a decent sized prop (compared to the old PA18). They were american engines spinning clockwise viewed from behind. After a good days towing where the gliders mainly kept me straight on takeoff, I would fly the aeroplane home without a glider. Guaranteed to get a nice shock as I, with lazy feet by now, raised the tail and she would rapidly swing left thanks to the Gyroscopic precession on the prop.
Gyroscopic precession is alive and kicking and though not visible it is easily felt and has had many a young taildragger pilot dancing on rudder pedals.
Oh sigh those were the days, now I fly a Boeing and the only real action my feet get, is walking to the carpark..

[jtzzr]

If I fall off I`m blaming all of you people,(go south while praying to mecca) dear Lord I`m going to die!:whocares:

[Edbear]

Now that I am concious of it I have found it is easier to hold lines at reasonable speeds. :scooter:




Sorry, I have to bite! How do you hold the line at unreasonable speeds...?:confused:

[Pixie]

The wheels move out from under the bike to the side while the centre of gravity of the bike stays put, hence the bike topples and I turn. I tested that out last year when I first joined this site. But I'll report on the bmx wheel test tomorrow...

OK genius
Coast down a straight incline,on your bike,with your hands off the bars.
Lean your body as far to the left or right as possible,this will move the C of G of the bike/rider system out from the center line of the bike (outside of the tyres contact patch)
Now see if the bike steers from a straight path

[Kflasher]

Who would have guessed there is a science to having fun

[McJim]

OK genius
Coast down a straight incline,on your bike,with your hands off the bars.
Lean your body as far to the left or right as possible,this will move the C of G of the bike/rider system out from the center line of the bike (outside of the tyres contact patch)
Now see if the bike steers from a straight path

This works on a push bike but I've never had the guts to do it on a motorbike. Is it supposed to work on a motorbike too?

[sAsLEX]

......watch a sea king flying along - it flies on a lean!
Only got Sprites so will have a look at them next time I see them




Don't apologise. I'm guessing that square profile tyres are fine for the mud tracks that very early bikes had to deal with, but they wouldn't be suitable for concrete or tarseal at anything over 20k/hr.


WRONG again. There are a few who use car tires on the rear of their cruisers and find good results from them. Search if you dont believe me.


Well, maybe. But has anyone ever experienced having a car go left when you turn the wheel to the right ?

Yes, its called drifting......

[judecatmad]

Well, maybe. But has anyone ever experienced having a car go left when you turn the wheel to the right ?

Depends how fast you're going around the corner! Go too fast and you won't go in the planned direction!

But that's centripetal force versus friction as opposed to gyroscopic force. Cars definitely do experience forces pushing to the left when going into a right turn (hence why your inside wheels will lift if you're going too fast!).

I guess with a car, the fact that you have a fixed axis between 2 rotating wheels means that cars are not subject to the same gyroscopic forces - cars don't lean in the same way that bikes do.

My head hurts............

[Animal]

I was an aircraft engineer when I was young, so I can tell you from experience: Helicopters defy all aerodynamic conventions and fly by converting vibration into lift. An amazing phenomenon. :)

[Motu]

I don't know much theory,but I now how to drive on gravel.With the VW's I used to thrash around we could say polar inertia - throttle off and a flick of the wheel to the right....then start dialing in left lock as you come into the corner with the back end coming out to the left,some is to do with the camber of the road too.But I've definatly entered corners turning the wheel the opposite way to the corner....and looking through the passengers window going straight ahead! You can do it on a bike too...if you are brave enough.

And what is the rear wheel doing while all this countersteering stuff is going on? Back to our spinning bicycle wheel - you turned it right,and it tilted left....now tilt it left - it will turn left....and stand up too.

[McJim]

O-kay. Now I feel sea sick. I'm gonna forget about corners and move to Arizona after reading this thread.

[judecatmad]

I was an aircraft engineer when I was young, so I can tell you from experience: Helicopters defy all aerodynamic conventions and fly by converting vibration into lift. An amazing phenomenon. :)

Bumblebees also defy the laws of aerodynamics/physics too...apparently....

(useless item of trivia #652)

[petesmeats]

In my understanding there is a major interaction between many different components when turning a bike but put simply...

1. The Gyroscopic stuff helps us get the bike on a lean

2. The Lean makes the bike/rider COG move to the left/right of the contact patches on the road

3. The weight of the rider acts through the COG but is transferred down through the bike at the lean angle.

4. The force at the contact patch has a horizontal and a vertical component.

5. The vertical component supports the rider/bike weight and the horizontal component (acting toward the centre of the turn) Acts as the centripetal force which turns the bike through the corner.

6. The further the bike leans the greater the horizontal reaction force will be meaning that the bike can turn through a tighter angle.

7. Once the Horizontal reaction force reaches the max friction force (Tyre constant x Vert reaction force) of the tyre on the road the bike will fall and the rider will leave copious amounts of leather/skin/plastic/glass etc all over the ground.

That is my understanding of cornering...

EDIT: The Rear wheel contributes alot to this cornering

I experimented with it in the weekend going out to Akaroa and found that in fact there is another aspect to it...

If on a right hand corner I lean too far i will scrape my exhaust on the ground causing me to lose my concentration and only narrowly escape being inserted into a wall...

I reckon that if you want to learn the art of cornering the theory only really comes into it once you are competent... It is mainly just practice and trial and error (hopefully not catastrophic error) That will get you to the point where to go faster the theory must be known...

I'm also not completely convinced about the whole broomstick thing...

Feel free to correct me if i'm wrong about stuff cos i'm a youngun' with much to learn...:shutup:

[Masterchop]

Arhh, Now I see why all you guys are so slow!

You think about it all to much.
Relax it just happens.

[marty]

the c of g always acts vertically down.

[thealmightytaco]

OK genius
Coast down a straight incline,on your bike,with your hands off the bars.
Lean your body as far to the left or right as possible,this will move the C of G of the bike/rider system out from the center line of the bike (outside of the tyres contact patch)
Now see if the bike steers from a straight path

I'm not sure which argument you're fighting for but...

OK genius
Of course the bike steers offline, the offset cog will cause the lean and then the bike to turn as camber thrust kicks in. But on a motorbike that bollocks might take a bit long, thanks to the gyroscopic ladida, and a persons balls being too small to accept such a lack of control.

But if you read back to where I tested the bmx wheel you'll find I've already surrendered to accepting the gyroscopic effect tips the bike over, if only to kickstart the whole operation at the least.

[Animal]

Bumblebees also defy the laws of aerodynamics/physics too...apparently....

(useless item of trivia #652)
This is true! I remember reading somwhere during my training that NASA had apparently studied their design (at some ridiculous cost) and declared them to be in defiance of all conventions. Yet the little bastards do fly! I know this because I personally collected one across my neck while doing a-hundred-and-plenty. The bruise was impressive, but got me no sympathy!

Anyway, cats rule!