(Counter) Steering

[ShovelStrokeEd]

John, pay real close attention and it'll lean right for just a little bit and then the force of you push will overcome the very subtle force at the bars (self correction pushing back at you) and then the bike will proceed to car steer quite happily. You can even do this at over a walking speed, watch the Gold Wing riders and HD Dresser folk in parking lots. They do want to lean for fear of scratching chrome so they car steer all over the place. Those great big tiller bars generate enough force to make it easy.

 

The term was gyroscopic precession, not procession. Refers to the tendency of a spinning wheel to want to maintain it's vertical axis normal to the earth's core. Easy to feel, set up your wheel on a Mark Parnes or anybody elses balancer and give 'er a good spin. Then try to tilt the balancer at 90 degrees to the spinning wheel. It'll put up a fight way out of proportion, actually it is in proportion, to the mass of the wheel when static.

[PT Steve]

I have been reading this thread. There are many interesting views.

The bottom line is:

There are many factors in the equation of keeping a motorcycle from falling over. Countersteering in but one of the elements.

As speed changes, the contribution from each of the factors will change in magnitude.

However, all of the elements of the equation are present regardless of speed.

At very low speeds, I will believe the contribution from CS may be so small as to go unnoticed in comparison to some of the other elements. However, it's still there.

 

If someone can show me at what speed the laws of physics change, I will reconsider.

 

I apologize if I seem abrupt. I haven't figured out how to type with facial expresions and hand waving .

[FlyingFinn]

Steve, in my opinion that is exactly the point.

All the forces are always there, just their magnitude changes.

Thanks for summing it up for me.

 

--

Mikko

[motorman587]

KISS, keep it simple stupid, wow. My head hurts after reading all that. Scared to teach or even go ride.

[Joe Frickin' Friday]

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

 

Instrumentation. I'm curious to see what the steering movements (magnitude and direction) actually are during various high- and low-speed maneuvers. One pot will provide a voltage corresponding to steering angle; the other will provide a DC offset so that my DVM can show zero volts when the bars are pointing straight ahead. (all of this assumes the whole mess can be made to cope with ignition noise...)

 

My suspicion is that a turn is always preceeded by a countersteer, that while it may be imperceptible to the eye or to kinesthetic sensibility, a pot that resolves 30 mV per degree of rotation will reveal the presense of those tiny countersteer actions. We shall see.

 

When I was younger, my brother and I had a disagreement about how rapidly a commercial jet accelerates during takeoff. The answer was had by bringing a protractor onto a flight, with a string taped to center, and a quarter taped to the free end of the string. Hangs at zero degrees when stationary, leans to rear during acceleration, difference reveals magnitude of acceleration. He won the bet - it was somewhere between 0.2 and 0.25 g's, IIRC - but I was happy just to have figured out how to definitively answer the question.

[Voodoo]

When I was younger, my brother and I had a disagreement about how rapidly a commercial jet accelerates during takeoff. The answer was had by bringing a protractor onto a flight, with a string taped to center, and a quarter taped to the free end of the string. Hangs at zero degrees when stationary, leans to rear during acceleration, difference reveals magnitude of acceleration. He won the bet - it was somewhere between 0.2 and 0.25 g's, IIRC - but I was happy just to have figured out how to definitively answer the question.

 

 

Something tells me that you and I had very different childhoods.

[ShovelStrokeEd]

And you wondered why he wound up as an engineer?

[Joe Frickin' Friday]

And you wondered why he wound up as an engineer?

 

I scored pretty high on The Nerdity Test.

[Pilgrim]

You've always been kinda weird, haven't you, Major? I'll bet you were a real trial to your parents, what with all the noises and smells and smoke and other surprises around the house.

Pilgrim

[FlyingFinn]

Since almost all (single turn)potentiometers can be quite unlinear and even non-monotonic, I would consider making it measurement bridge with 2 varying elements.

4 Potentiometers altogether and two of them tied to the steering with those two configured to move the opposite ways.

 

After you get that brigde balanced at 0deg steering angle it should provide pretty reliable readings even at very small steering angles.

 

If there's anything I could do to help, let me know.

 

--

Mikko

[Joe Frickin' Friday]

Since almost all (single turn)potentiometers can be quite unlinear and even non-monotonic, I would consider making it measurement bridge with 2 varying elements.

4 Potentiometers altogether and two of them tied to the steering with those two configured to move the opposite ways.

 

Hm. this one was supposed to be linear. Even if it's not, I can still calibrate it by checking the output at various angles. Apart from that, it would take some figuring to get two pots to turn with the steering; it's easy to connect just one.

 

If there's anything I could do to help, let me know.

 

Sure, draw me a circuit diagram and figure out how to turn two puts with one triple-tree.

[Slartidbartfast]

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

You still counter-steer to INITIATE the turn. It's just that at slow speeds, making tight manouvers, you then have to turn the bars in the direction of the turn to actually get the darned thing round the corner. Gyroscopic forces are not a factor at parking lot speeds. Yes, there does seem to be a (fairly low) speed at which the dominant forces involved in completing a turn change but I believe the means of <b>initiating</b> the turn is always the same.

[PT Steve]

It seems to me the hardest part is going to be corrolating the steering input to bank (lean, I think in airplane terms) angle. At low speeds, it's going to happen very quickly.

Now, if you had an Inertial System on board, and some timed recorders, this would be a piece of cake.

[Wooster]

Mitch alias Dread Pirate Roberts, alias Ziggy StarDust, alias anything you please,

 

While I consider myself more street than dirt rider, it's worth noting counter steering isn't discussion topic among dirt riders; weight shift fore/aft, left/right, yes, but never any consideration of directing handlebars other than stability. Perhaps this concept (cs) is too subtle for rockaday world of dirt riding.

 

Jon who once pulled a mussel excersizing by the sea

 

And Ed, I appreciate your information yet remain skeptical of "unified" theory of motorcycle turning

[BitScribbler]

I can hardly wait for the results of the Major's experiments.

 

Reading this thread, for a minute there I thought I'd clicked onto Scientific American rather than a biker forum!

[ShovelStrokeEd]

Taking street riding techniques out into the dirt can produce some pretty amazing results. Especially at low speeds in soft sand.

 

There I was, about 80 miles north of here at some biker type hangout with a few friends. I'm on my KRS and didn't get a good shot at the back in for the first available parking space so I did an orbit of the parking lot. Way out there where no one was parked, I'm running around all smug like, feet on pegs at low speed and get ready to turn a 90 degree right. Nice little countersteer push on the right bar and the friggin' front wheel digs right into the sand instead of rolling along like I expected. Direct to full left lock and down I go over the starboard rail, screaming imprications at the laws of physics, my own stupid seff and whatever Gods govern which of the scantily clad maidens happen to be looking out over the bar rail at the moment. "Look, Candy, the strangly clad person has dropped his machine and is now doing a dance similar to that of my two year old." or words to that effect. I strongly considered just picking it back up and riding off into the middle distance but, being a K bike, I needed help. Not one of my finer moments.

[FlyingFinn]

Like you know, pots come in two flavors, linear and logarithmic. But even the "linear" ones have usually very bad differential linearity (DNL). In other words, 1deg rotation of the sweeper doesn't always produce same change in measured resistance.

In extreme cases (happens a lot if you measure a pot carefully enough) the rotation -> resistance transfer function isn't even monotonic!

 

That's why real transducers are much better for the job. Which you already knew.

 

I'll work on the schematic as soon as I get home from the salt mines.

 

To make the pots "turn opposite ways" is simple.

You just mount one of them upside down.

Or even more simple, connect one pot opposite from the other. Wires connect to the "left stop" and "sweeper" on one of the pots and "right stop" and sweeper on the other.

Now if the pots turn the same direction, the reading will increase on one and decrease on the other.

 

--

Mikko

[PT Steve]

Rotary pots are used frequently in older commercial airplanes (old Boeing airplanes 747,737.727) as sensors for the Flight Recorder Systems. They will give very repeatable results if used in conjuction with a reference voltage. Just use the pot as a shunt and compare the voltage across the pot to the reference. This even helps get rid of some noise.

[FlyingFinn]

True about the shunt arrangement.

 

It might also be that Boeing is not using $2 potentiometers from RadioShack in their products

 

--

Mikko

[eruff]

I am so confused by this thread that I can't believe I have ever managed to make a left turn. I best just not think about it.

 

-E

[ShovelStrokeEd]

Why use a rotary pot at all?

 

Linear pots are available, the steering damper mounts are already up under the A-frame. Use that. This way one pot, calibrate for zero position someplace in mid stroke and your done. A little portable data logger, they are availabe as self contained units, and you have your setup. Minus a couple of wires and some drilling and tapping of course.

 

If you must go rotary, a grey code position encoder will provide much better resolution. The cost is pretty high though. I may be able to help with that as well. It's been 6 years but I think I have one kicking around the apartment somewhere.

[Id's_OK]

Good mornin, Ed. Couldn't sleep either?

 

In the immortal words of Chris Farley, "Holy Schnike!"

 

Nerdity test had me rollin, though!

[Joe Frickin' Friday]

Why use a rotary pot at all?

 

Cuz they're cheap, and available locally. Not sure where to find a (cheap) linear pot.

 

A little portable data logger,

 

Where can I find one for $10?

[ShovelStrokeEd]

Mine is not quite that portable but I'll be happy to lend it to you. About a 4x6x3/4" box. Needs a Laptop with XP and USB ports. 8 channels of 12 bit A2D. I can box it up and have it to you with a couple of days notice.

[Paul De]

Geez, on a custom cruiser site they were attempting the very same experiment. They were held up for a while until they found a way to get the pot chromed without messing up the resistance of the pot's windings. But they ran into an even larger obstacle when the data logger kept on failing. Seems that it couldn't handle life on a bike with a solid mounted FL motor in a hard tail frame. So they gave up and went back to discussing what will be the fashion forward trend in doo-rags. I think that there was consensus that in 2006 orange will be the new pink for lady doo-rags, but the guys are sticking to black, but will wash their doo-rags more often cuz bug splatter on the head is so passé. Are those folks a bunch of nerds or what!!!

 

Actually this little experiment you’re discussing intrigues me to no end and could debunk a whole bunch of conventional wisdom comments (particularly mine). One of the threads a while back discussed what was going on during hard acceleration out of a high speed constant radius turn..... The question was something like; does a street machine step the rear tire out a smidge or track? Anyway, if this little experiment comes together it would be worth doing a number of test protocols to help bring insight to a long list of steering dynamics topics we discuss here.

[bigboy]

sheesh guys

 

This thread is really going places try this one to explore the basics of CS watch a racer , what you will all see at any speed is, CS into the bend ,CS out of the bend it happens because it has got to happen .

[jodyrevb]

OK, here I am safely back at home after nearly dumping the bike countless times trying to understand what happens when I turn the bike at low speeds. Lacking LVDTs and data loggers, I was using the mirrors (on the handlebars on my RS), which I had aimed to include a view of my saddlebags to give a sensitive indicator of handlebar position. The immediate effect was to cause a severe control problem resulting from the consequent violation of the "look where you want to go" principle while trying to watch the saddlebags in the mirror while executing turns at lower and lower speeds. (Some of the turns were planned, and some were required to keep from falling over.) What I observed bore out what many of the posters here have noted: countersteering is required to initiate a turn at even the lowest speeds. Additionally, it turned out that not all of the countersteering "events" were the result of a conscious decision to begin a turn. As Hough and others have pointed out, the front wheel of a bike traveling in a straight line is constantly making corrections right and left in order to keep the tires under the center of mass of the bike. Sometimes I found myself initiating a turn by not making a steering correction at a time that would result in the bike leaning in the desired direction that would allow me to turn the handlebars into the turn. It occurred to me that waiting for a bike to begin leaning the way I wanted to go was probably not the best control strategy. This probably shows that I need more practice in low speed handling exercises.

[Shaun]

A further 2¢ … under normal circumstances turning is a two part process. First, to turn left the front wheel must point left and to go right - point right relative to the direction of travel. Has to do with the consequence of scrub friction on the contact patch and the relative angle of the front axle. Second, centre of gravity (CG) must be inside the arc of the turn. With the CG above the plane of the contact forces there is a resultant rotation which must be offset with gravity (leaning the bike over). Applies at all speeds, weights, weather, moods …

 

Trail helps out by bridging the gap. Turning the bars will lean the bike into the intended direction, or vice a versa. This effect diminishs with velocity as the scrub friction attempts to straighten the wheel. Overall, less trail - better response, more trail - better tracking, within reasonable allowances.

 

Two methods of developing lean are weight shifting (WS) and countersteering (CS). Both work at all speeds but to differing degrees. At low speeds WS is most effective, before gyroscopic forces predominate. CS doubles the effort by involving an unbalanced opposite turn (away from intended direction) to promote lean then a corrected balanced turn as desired. At high speeds CS is most effective; taking advantage of gyroscopic rotation, general rotation and trail. In any case the resistance felt when CS’ing does not overrule the first part up top no matter what our senses tell us, power slides excluded.

 

At what speed does a preference for WS shift to CS? Depends on total mass, CG, front end geometry, turn radius and how the operator feels. As an advocate of experimentation I’m all in favour of those who want to go the distance. But please bear in mind that your results may be more indicative of rider style than bike dynamics. Do you like to turn first and move the CG second or the other way around?

[David]

With the CG above the plane of the contact forces there is a resultant rotation which must be offset with gravity (leaning the bike over). Applies at all speeds, weights, weather, moods …

 

Since I can never resist joining these threads, I'll clarify one thing here.

 

1) The front wheel must eventually turn toward the turn in order to execute it. In other words, after turning toward the outside so that the bike begins to lean, it will then have to turn toward the inside of the turn.

 

2) While the wheel needs to turn toward the inside, the bike itself does not need to lean toward the inside of the turn, ever. It's quite possible to have the bike leaning toward the outside while the front wheel is turning toward the inside, especially at low speeds and on a light bike where body weight has more impact.

[Wooster]

What I observed bore out what many of the posters here have noted: countersteering is required to initiate a turn at even the lowest speeds.

 

Gee Jody, I'm relieved to know you didn't crack any plastic in the interest of science. Also, I appreciate you're approach, i.e. experiential. Most of my "experimental" riding is dirt where tip overs are inconsequential. Now, in dirt laboratory, I often end aerobic riding (lots of panting here) with a few "donuts", figure eights and wheelies, either in my dirt drive or adjacent field. I mention this as I'm rather certain no countersteering occurs in the figure eights: front wheel turned in, body and butt outside and bike leaned (alot) inside turn with no throtle (idling 400 cc motor providing steady "oomph") or little throttle w/clutch slip. So, I take small exception to your "countersteering is required..." assertion. OTOH, I may be missing something (wouldn't be first time).

This question may resist qualitative analysis; after all, riding is mostly fun and rarely (excepting your scientific self) do riders apply analytical eye to each action. Quantitative data (Major Tom's pot-latch) may be necessary after all.

 

Wooster who enjoys turning, regardless of mechanism involved

 

Thirty minutes to CBS Second Anahiem SuperCross !!! Go Bubba !!!

[Couchrocket]

i was just making a tongue-in-cheek observation about that strange speed at which steering stops and counter-steering starts.

 

I didn't read the entire thread, so forgive if I stomp on toes or anything.... but I had to respond to your original tongue-in-cheek-ness, , which I found quite amusing -- and which reminded me of "similar" reasoning we use in the fire service to explore the absurd. Fire hose, you see, has a property known as "friction loss." That is, for every 100' of fire hose you lay out, friction causes a certain and quantifiable amount of pressure loss. The fellow running the pump in the fire engine has to determine how much hose is "out there" what its friction loss is per 100' (a function of diameter of the hose and the nozzle type being used) and what the desired pressure is for the nozzle at the end of it all. That way the firefighter on the end will have "just enough" pressure to attack the fire effectively and not so little as to look like a prostate problem, or so much as to knock said fireperson on their keister and render the whole exercise "nonfucntionable."

 

So, I bore you with all this to say only that a classic problem in calculating pressure in fire hose is: If 2 1/2" fire hose generates 10 lb.s of friction loss per 100' of hose laid out... and you're running the fire pump at 100 psig -- how much hose do you have to lay out to not have any water coming out the other end? It seems analogous to your "speed where neither counter-steering, nor direct steering" will work!

 

Okay, humble apology for going so far afield!

[Berts]

My MSF intructor said it best.

"Steering, is nothing more than a controlled near crash from which one recovered."

Truer words have never been spoken.

Then he went on to explain the physics.

[KeithC]

What speed does coutersteering begin to be effective?

 

Pull up to a curb, put both tires so they are just touching the curb.

 

Start to pull out.

 

You want to go left to get away from the curb.

 

Apply pressure to the bars toward the left. no joy.

 

Apply pressure to the bars toward the right. joy.

 

That is one mph.

 

Keith Code

[EffBee]

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

 

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

 

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

 

In case no one has answered the question thus far, it assumes that there is a definitive point at which one method ends and the other begins. Thus, at that point, the argument would be that turning the bars will have no effect.

 

Have you considered the possibility of instead of a low-speed "transition" point, there may actually be a period of overlap where, depending on the bike, the geometry, the speed and the rider's body position, that either direct steering (i.e. weight shift) or countersteering works?

[EffBee]

With the CG above the plane of the contact forces there is a resultant rotation which must be offset with gravity (leaning the bike over). Applies at all speeds, weights, weather, moods …

 

Since I can never resist joining these threads, I'll clarify one thing here.

 

1) The front wheel must eventually turn toward the turn in order to execute it. In other words, after turning toward the outside so that the bike begins to lean, it will then have to turn toward the inside of the turn.

 

2) While the wheel needs to turn toward the inside, the bike itself does not need to lean toward the inside of the turn, ever. It's quite possible to have the bike leaning toward the outside while the front wheel is turning toward the inside, especially at low speeds and on a light bike where body weight has more impact.

 

I think what David points out is true. Lean is a matter of physics. If you can supply sufficient counter weight to the inside of a turn to offset the intertia of the bike which wants to go to the outside of a turn, then technically it could probably be cornered while perfectly vertical or even leaning to the outside. Of course at speed on the street or track, this is virtually impossible.

 

But we see this all the time in trials riding where at slow speeds the bike has very little inertia and the weight of a human is more than sufficient to counter that inertia. Side-hilling and then turning uphill, for example. In such a situation, one would weight the inside peg and lean the bike to the outside. Of course, as speeds rise this becomes more difficult because the inertia of the bike increases (even as light as trials bikes are) to the point where the rider's weight cannot cancel it.

[bobbybob]

So far, everyone has missed it--shame cause it's so simple. Countersteering works because when you turn the wheel left, the bike starts to turn left & centrifugal force then tries to throw the bike right to the outside of the turn, therefore making it lean right. Here's an example: ride a bike with a side-car on the right side. Turn the bars left & the bike turns left--no problem (but YOU will sure feel the centrifugal force to the right!). Remove the side-car & turn the wheel left: bike leans right because no side-car to counter the centrifugal force. Simple as that--easy to see. A right turn is nothing more than a "controlled continuous free-fall" to the right. You're not REALLY turning right in the true sense of the word "turning". You're falling to the right at a precise rate which keeps you in the line that you have chosen for that particular turn, and that also counters the centrifugal force which would pull you back upright to the left. To STOP that free fall, you push on the left grip(turning the wheel right), creating cent. force to the left, stopping your "free-fall" and you lean back up to the left out of the free-fall. All the "high-tech" arguments about gyroscopic precession, etc are all BS. If you've ever ridden a side-car or a trike you will understand this very clearly. Low speeds: Why does the bike follow the handlebars at low speeds? Because the centrifugal force is not yet high enough to force a lean in the opposite direction. When does this happen? No set speed--but if you use physics to calculate the force vectors you could determine it for a specific bike/rider weight/etc/ set of conditions.

[ShovelStrokeEd]

Glad you cleared that up for us. KeithC and PMDave just don't know what they are talking about, I guess.

 

I do remember a whole bunch of engineers, back in the '50's pontificating that a sub 9 second quarter mile was impossible cause the tires could not transmit more than 1 g of force. Hmm, glad no one told my 7 second drag bike or Kenny Bernstein's mid 4 second top fuel car.

 

Not much point in all this study and discussion, you read it right here on the internet, folks.

[bobbybob]

Glad you cleared that up for us. KeithC and PMDave just don't know what they are talking about, I guess.

I do remember a whole bunch of engineers, back in the '50's pontificating that a sub 9 second quarter mile was impossible cause the tires could not transmit more than 1 g of force. Hmm, glad no one told my 7 second drag bike or Kenny Bernstein's mid 4 second top fuel car.

 

Not much point in all this study and discussion, you read it right here on the internet, folks.

Wasn't aware I contradicted Keith Code or Dave but let me clarify that my statements are re. *counter-steering* alone--not some of the other dynamics of riding, into which precession & other principles might come into play.

[ShovelStrokeEd]

You're not REALLY turning right in the true sense of the word "turning". You're falling to the right at a precise rate which keeps you in the line that you have chosen for that particular turn, and that also counters the centrifugal force which would pull you back upright to the left. To STOP that free fall, you push on the left grip(turning the wheel right), creating cent. force to the left, stopping your "free-fall" and you lean back up to the left out of the free-fall.

 

I have to disagree with thee last part of the above. I'll leave the rest alone for now.

 

Properly done, you do not have to push the opposite grip to "stop the free fall".

The duration of your push on the inside bar establishes your lean angle and, for every turn, there is a combination of lean angle and centrifugal force that will reach equilibrium for the speed at which you are running. With well honed technique, you can feel the bike approaching this equilibriam point and just stop pushing. The bike will continue to follow that arc and maintain that lean angle so long as the speed remains the same. Right around in a circle to take things to extremes. No pressure on either bar. Change any factor and the equilibrium condition goes back to being dynamic. Sometimes folks feel this as using the throttle to pull the bike upright when completing the turn. In fact, what is happening is the faster speed is increasing the centrifugal force and that is what is pulling the bike upright. Again, no pressure needed on the bars, you could do this with a foot throttle.

 

The dynamics of a motorcycle/rider combination and interaction are really complex to model. I think all of us are trying to express the same things but using differing terminolgy which can lead to confusion.

[bobbybob]

You're not REALLY turning right in the true sense of the word "turning". You're falling to the right at a precise rate which keeps you in the line that you have chosen for that particular turn, and that also counters the centrifugal force which would pull you back upright to the left. To STOP that free fall, you push on the left grip(turning the wheel right), creating cent. force to the left, stopping your "free-fall" and you lean back up to the left out of the free-fall.

 

I have to disagree with thee last part of the above. I'll leave the rest alone for now.

 

Properly done, you do not have to push the opposite grip to "stop the free fall".

The duration of your push on the inside bar establishes your lean angle and, for every turn, there is a combination of lean angle and centrifugal force that will reach equilibrium for the speed at which you are running. With well honed technique, you can feel the bike approaching this equilibriam point and just stop pushing. The bike will continue to follow that arc and maintain that lean angle so long as the speed remains the same. Right around in a circle to take things to extremes. No pressure on either bar. Change any factor and the equilibrium condition goes back to being dynamic. Sometimes folks feel this as using the throttle to pull the bike upright when completing the turn. In fact, what is happening is the faster speed is increasing the centrifugal force and that is what is pulling the bike upright. Again, no pressure needed on the bars, you could do this with a foot throttle.

 

The dynamics of a motorcycle/rider combination and interaction are really complex to model. I think all of us are trying to express the same things but using differing terminolgy which can lead to confusion.

 

Ed--I agree with all you just said--we are saying the same thing. I did not mean that you had to "arrest" the act of leaning right by counter-steering left. Once you're at "that" perfect angle of equilibrium, everything kind of takes care of itself like you said...until you're ready to stop the turning process, at which time you would then turn bars slightly to the right to get back up out of the turn. We're on the same page. I still believe in the "continuous free fall" theory though, and I'm probably not very good in explaining it. To me, making a "turn" means turning your front wheel in one direction and going in an arc around a point. When I'm leaned over making a turn on a moto, my bars are pretty much centered, maybe even slightly opposite the turn--so if you're in a helicopter overhead looking down at the biker making a constant turn, he certainly appears to be going around that curve, yet he's really falling in the direction of the turn at a rate that keeps him in the path he desires thru the turn. The net effect is--he *turns*. So I am just analyzing the components that make up a "turn" done on a motorcycle as opposed to a 3 or 4 wheel conveyance.

[DiggerJim]

Glad you cleared that up for us. KeithC and PMDave just don't know what they are talking about, I guess.

LOL!

 

Actually, if I recall my physics correctly, it's centripetal force (because we tend to move in tighter & tighter circles toward the center) rather than centrifugal force (which pushes us away from the center). Most people don't make a distinction. On the other hand, I spent a lot of time dozing off in those classes...I was tired from trying to wrap my head around quantum jumps where an electron is either here or there but is never in between...

 

It's all just magic!

 

Jim

[AlanBrown]

Sorry, but you have (free)-fallen into another myth. There is no such thing as centrifugal force. It is a term used to describe the result of an object being forced to change direction. It's a reaction, not a real force.

 

Newton's First Law of Motion states that an object will travel in a straight line at a constant speed (forever, if allowed), unless acted on by another force. For 99.9% of all instances, that other force is usually friction. Road friction, air friction, etc. Out in deep space, air friction does not exist, nor does the restraining force of gravity. An object, once placed in motion out there, will travel in a straight line, forever.

 

Now, back to earth. Try an experiment: take a paper plate and cut a quarter-slice off (like a slice of pizza). Now roll a small ball round the inside of the plate. What happens when the ball exits the gap? Does it continue in the same circle? No, it obeys Newton's First Law and travels in a straight line, because it is no longer being constrained by the physical curvature of the plate.

 

The phenomenon called centrifugal force does not "push" an object away from the curve it is trying to adopt. The "force" is not a force at all, but a reaction to the object being asked to change direction from it's preferred course,a straight line.

 

When you drive a car and turn the wheel to the right, you are forcing the car to turn right but YOU (another object) are still obeying Newton's first law, and are trying to stay in a stright line. That's why it "feels" like you are being pushed to the left. Nothing is pushing you. You are just sensing a reaction to being asked to violate the First Law.

[bobbybob]

Sorry, but you have (free)-fallen into another myth. There is no such thing as centrifugal force. It is a term used to describe the result of an object being forced to change direction. It's a reaction, not a real force.quote]

 

Alan, Ok it's a reaction--call it whatever you want--look it up in Wikipedia--they even have a "real" and a "pseudo" centrifugal force so they dispute you. But whatever it is called, it happens because you can feel it's effect. If it wasn't real, it wouldn't affect anything would it?

I think this thread is morphing into nothingness...it's...no...longer...real......is......it.......? z z z z z z z z zzzzzzz............

[ShovelStrokeEd]

In support of Alan's statement, quoted from Wikepedia.

 

Centrifugal force (from Latin centrum "center" and fugere "to flee") is a term which may refer to two different forces which are related to rotation. Both of them are oriented away from the axis of rotation, but the object on which they are exerted differs.

 

* A real or "reactive" centrifugal force occurs in reaction to a centripetal acceleration acting on a mass. This centrifugal force is equal in magnitude to the centripetal force, directed away from the center of rotation, and is exerted by the rotating object upon the object which imposes the centripetal acceleration. Although this sense was used by Isaac Newton,[1] it is only occasionally used in modern discussions.[2][3][4][5]

 

* A pseudo or "fictitious" centrifugal force appears when a rotating reference frame is used for analysis. The (true) frame acceleration is substituted by a (fictitious) centrifugal force that is exerted on all objects, and directed away from the axis of rotation.

 

Both of the above can be easily observed in action for a passenger riding in a car. If a car swerves around a corner, a passenger's body seems to move towards the outer edge of the car and then pushes against the door.

 

In the reference frame that is rotating together with the car (a model which those inside the car will often find natural), it looks as if a force is pushing the passenger away from the center of the bend. This is a fictitious force--not an actual force exerted by any other object. The illusion occurs when the reference frame is the car, because that ignores the car's acceleration. A number of physicists treat it much as if it were a real force, as they find that it makes calculations simpler and gives correct results.

 

However, the force with which the passenger pushes against the door is very real. That force is called a reaction force because it results from passive interaction with the car which actively pushes against the body. As it is directed outward, it is a centrifugal force. Note that this real centrifugal force does not appear until the person touches the body of the car. The car also exerts an equal but opposite force on the person, called "centripetal force". In this case the centrifugal force is canceled by the centripetal force, and the net force is zero, thus the person does not accelerate with respect to the car.

[bobbybob]

OK--this is absolutelty the last post I'll make to this thread. Alan & Ed: WIKIPEDIA is not even a real encyclopedia. ANYONE can add any manner of brainless drivel to it. Thas it, buh-bye.

[Green RT]

OK--this is absolutelty the last post I'll make to this thread. Alan & Ed: WIKIPEDIA is not even a real encyclopedia. ANYONE can add any manner of brainless drivel to it. Thas it, buh-bye.

Someone once told me you should believe half of what you read and a quarter of what you hear. Wikipedia is a valuable source of information. But you should maintain a healthy skepticism about what you read there just as you should when reading the Encyclopedia Britannica or anything else.

[ShovelStrokeEd]

Oh fer chrissake!

 

Would you care to believe NASA or maybe the physics departments of various universities instead of Wikipedia? Knocking the source of something you don't agree with is kinda poor form. Especially when the source is often right.

[mefly2]

Yeeeeouch .... can't we just be friends ...

[philbytx]

As long as you are happy with your own theory...that's entirely fine with me .

But I AM pleased that you aren't continuing to flog a dead horse!

[russell_bynum]

. I can't fathom how people don't believe in counter steering, at ANY speed.

 

Not any speed. Try this: Stop. Turn bars all the way to the right. Start. What direction does the bike turn?

 

 

You don't turn the bike by counter-steering, you LEAN the bike by counter-steering.