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C Of G And Cornering - The World Isn't Flat, After All...


Woody
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Here's an interesting thought.

 

Whilst cornering, the primary reason for leaning off the bike is to enable you to keep the bike more upright (reduce your lean angle). The common perception is that what you are doing is lowering the centre of gravity (lower c of g equals less lean angle), but watching some of the new GP stars I started thinking that this perception is misguided. What you are really doing is moving your centre of gravity toward the inside of the corner, thus allowing the bike to stand up a little more.

 

Watching Dani Pedrosa and Casey Stoner exit corners really started me thinking about this. I pick these two, as their riding styles are far more pronounced than many of the other riders. They appear to almost ride the bikes side saddle they are hanging so far off, with the bikes virtually upright as they exit the corner.

 

The more I think about it, the more convinced I am that this is the case and the more daft I feel for even contemplating the false view that you are lowering the c of g. Common sense alone rules this out.

 

Apologies if anybody else has brought this up previously (I haven't done a search), but I was just sitting around not doing anything in particular when I had one of those "of course, that's what is happening" moments... as you do.

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The "COMBINED" CG height will be exactly the same height (given equilibrium) no matter where YOU are on the bike given the same speed and radius.

 

Hanging off certainly moves YOUR CG to the inside of the corner (but moves the bikes out a little...) and the COMBINED CG stays at the same height.

 

One would want to pick the bike up off the edge of the tire while coming out for a couple reasons... One, you want to save the edge to maximise mid-corner speed through the race. Two, you can put more power down when the tire isn't right on the edge. Three... (this ones a little tough to follow for some) the tire is smaller the closer you get to the edge... This means that when you roll over to the edge, if you keep the same speed, your RPM's will rise... You can use that extra HP WHILE picking the bike up to help add drive out of the turn... If you're in an endurance race you MAY be able to save a bit of fuel by hanging way off and using the larger portion of the tire. That is... if the extra wind resistance isn't offsetting the fuel savings...

 

Each tire will have a lean angle where it will generate the most grip. You want to use THAT lean angle mid-turn as far as I know. To do that AND go fast/er, you hang off which lowers the combined CG and will require more centrepital force (AKA Speed) to achieve equilibrium... You hang off just enough and use just enough speed at the "right" lean angle for your tire/setup/geometry/etc combination to maximise grip... Or at least that's how I see it, but I've never even done Code's L1 class... I'd LOVE to, but I have more suspension and motorcycle to buy before I can get on the track as well as in school. School will come before track, but I will be using the school AND track days to get a setup started so I may as well start with the suspension I'll be using on track...

 

In racing, EVERYTHING counts. It's all about energy management.

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Hey Woody! How ya goin, mate? Ya winnin?

 

The way it was explained to me as a squid was that the more you hang off, the less lean angle required for a given speed/radius. Hence, you could add more lean angle to facilitate more speed, or add more speed at a given turn radius by leaning over more and turning the throttle more....

result: more corner speed. Seems a simple enuf idea. Now WHY that happens...hmmm.

 

Is it moving toward the inside of the corner that does the trick? Like a sidecar monkey counter balancing the tendency of the bike to want to roll up and over on the pivot point of the wheel track like a hinge?

 

(And why do some bikes want to "stand up" in a corner when some seem to remain "neutral"?)

 

Is it giving gravity more of a (longer) lever?

 

Or is it moving the center of gravity lower that gives centrifugal effect less of a (shorter) lever?

 

Or is it something else? Like hanging off toward the inside of a turn moves more mass further away from the wheel track radius to a shorter radius track? Like moving toward the inside of a turntable creates less inertial forces? Think about placing something small on a stereo turntable, near the edge travels further and faster than near the center. Hmmm...

 

Sounds like the ice skater at the olympics inverse....far out...I mean...far in. hee hee hee. B)

 

I'll need to refer to previous posts on another thread to reaquaint myself with the idea of "COMBINED C/G HEIGHT". And "Hanging off moves the bike out a little"?

 

Um...not in my universe. Hanging off moves the bike IN a little in my universe. More lean angle moves the bike out a little. Less lean angle, less offset.

 

Hmmm...

 

I'll need to let this meat marinade for awhile. (And go find that physics website again.) Gotta go to work.

 

Cheers.

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Well, g'day there :)

 

If, whilst riding in a straight line you push yourself off to the side of the bike (not down, just to the side), what happens? The bike leans in the opposite direction. You need a little lean angle just to keep heading straight. To get the bike upright again you need to start turning.

 

Finally understanding this, somewhat fundamental idea has changed the whole way that I now tackle my cornering. I guess it also goes some way to explaining how relatively unimportant it is to get your knee down. Really, you should be trying to keep the ruddy things off the ground if you can at all help it.

 

I remember, when I was starting out, trying to get my knee down (as you do). I'd race up to a corner, push myself off the bike as far as I could, shove my knee out and tip the bike in at the very last second. I'd be taking corners faster than I ever had before, but the bloody thing would never touch. Of course in my stupid invincible adolescent way (as we all are when teenagers), I didn't know it at the time but what I was doing, quite by accident, was pretty much the best thing I could do NOT to get my knee down. By pushing myself away from the bike and turning as late as I could, I was drastically reducing the required lean angle to get around the corner.

 

If only I knew then what I know now, eh... :D

 

 

Ain't riding the best?

I love the way you're always striving for improvements and to make yourself that little bit better/ quicker/ safer. I love it that riding is so involving, how the rider can change the way the bike acts just by moving their body around or changing their position by the tiniest amount. Brilliant!

(Flipping cold though at the moment!)

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I believe I may have misunderstood what was meant by "move the bike out a little". I was thinking of moving the entire bike from wheels up outward in the corner. Perhaps, "move the bike out a little" meant the same thing as "less lean angle"?

 

Funny, after I left for work yesterday, I was thinking about hanging off prior to turning in or prior to even applyng the brake(s) as I approach a corner, and, the point being again, as usual...why? So, since you brought it up...haha...it would seem to me that hanging off while traveling in a straight line creates uneven weight distribution, "unbalancing" the bike as it were, so one must lean the opposite side a bit to maintain balance or a straight line...or does it?

 

I recall hanging off prior to braking at the end of a straightaway, but, I don't recall needing to apply any pressure to the bars, or weight to the pegs to keep the bike straight up and down. Perhaps the gyroscopic effect of the wheels was too high to be unbalanced by such a small issue as my butt offset by 10" or 12"? Yes, I think at slower speeds, with less gyro effect, around the parking lot or in the neighborhood or a bike with very light wire wheels (like a dirt bike) maybe yes, my butt would overcome the gyro effect and unbalance the bike enuf to need a steering input to maintain a straightline. Man that bike felt like a rock of stability at speed. Hmmm...

 

So, the dough is starting to rise. Be back soon.

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  • 3 weeks later...

Not to complicate things but you all are forgeting about torque. The bike has a CG and so do you. You combined with the bike also haa a combined CG. The combined CG moves relative to the Bike and you depending on how you move relative to the bike.

 

Now, we you do your flying V formation in a straight line the bike and you are displaced relative to the combined CG. But that is not all that is going on. Your respective torques have to be equal or the system will rotate (i.e. fall). Go around a corner and add in angular momentum which wants to send you and the bike on the tangent of the corner. When you corner your flying V can lean because there are some new forces trying to pull (and thus rotate) the system. You lean the system more to counteract those forces.

 

So when you lean off there is certainly a CG issue, but your movements have more to do with torque issues. Not only in your movements but in how you counteract the forces in the corner. Sir Code mentions them in his book. You need to account for the pressure you apply to the bike relative to the axis of rotation and how that effects the bike. You also need to account for the angular momentum and the torque effect on the bike and its suspension.

 

I'm not going to profess to understand why getting low is better, but it certainly reduces the "lever" and therefore reduces the torque you are applying to the bike. If you align your CG with the bikes relative to the outward force of the angular moentum, you can minimize or obviate the torque effect on the bike. Go to low and you cause more problems. Dance around to much getting to where you should be and you cause even more problems.

 

Now this is just a simplification because you'd need to account for the gyroscopic forces (wheels, engine and drivetrain), suspension/springs, friction, etc. and you have a lot going on in there. Best not to try to calculate your way to an accident. Physics is interesting but is almost always a simplification of what is really going on.

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Not to complicate things but you all are forgeting about torque...

 

Ah yes, but doesn't the torque act both ways? Which is why the bike is balanced whilst cornering (why it neither stands up nor falls over).

I would still say that the height (by height, I mean a vertical line through the bike in the same axis as the wheels) of the combined centre of gravity doesn't affect the lean angle of the bike (personally I would only ever consider the combined c of g, as bike and rider are acting as one unit, but that's me... :D ).

Wherever the c of g lies in this axis, the bike will require the same amount of lean to get around the corner. Sitting to the side however, is a different matter as the c of g is now off-line and needs bringing back to this balance point to follow the same line through the corner.

 

Momentum is a different issue, that only really applies during changes of direction. Still important, but I'm happy to feel this rather than trying to work it out. You're right, it's easy to try and overcalculate what is going on, instead of just enjoying the ride. :)

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if you are considering the bike as a lever while leaned over, being acted upon by balanced forces of gravity and centrifugal force, ie. the down force (gravity) equals the sideways force (lateral g), hence, the bike doesn't fall down...well....i have to disagree by definition. first, there is no such thing as centrifugal force. it is an effect felt by your body created by inertia. and where is that force directed? tangentially. that being said...

 

why does a bike balance at lean angle....i've been kicking this around for a few days without referring to the physics website...

 

and the train of thought goes something like this...

 

ok, let's start at the beginning. why does a bike balance while straight up and down? well, it's been hypothesized that the gyroscopic force of the wheels resists any change in their orientation. left, right,up, down, etc. it has also been suggested that trail keeps a bike balanced. well, i think that the trail effect certainly keeps the front wheel straight in line with the rear...which would seem to be important. and what creates this trail effect? the axle is behind an imaginary line drawn through the steering stem, and like the wheel on a shopping cart or a bed caster, it will stabilize naturally. WHEN IN MOTION. the bike must be rolling for any of this to work. hence, inertia and momentum come into play. well, i haven't heard any better theory than the gyro/trail thing.

 

so, what balances a bike when it is leaned over? (and why the heck does it roll in a bloody circle at all when leaned over??? hmmm...answer that one and i think we'll be on our way.)

 

oh, ive been meaning to say this for a while...some people have been using the words centrifical, centrifugal and centripedal (sic) interchangably to describe the same perception of the centrifugal effect. centripetal forces are something completely different, though do tend to go hand in hand with centrifugal effects. a centripetal force is a force acting upon a body in motion to unbalance inertia and create circular motion. gravity is a centripetal force acting upon the moon to cause it to orbit the earth.

 

ok, so what centripetal force is acting upon a motorcycle to overcome its forward momentum (inertia) to make it roll in a circle???

 

oh, wait, we haven't said what keeps a bike balanced when leaned over. hmmm...

 

what if it's the SAME thing?!?!?! HA! wouldn't that be sorta trippy? well, prepare to shift paradigms kiddies...

 

hold onto your hats. here's a thot. about six months ago, i was reading a post from a guy who had built a little indicator for his steering stem to indicate when the wheel was straight. or not. and funny thing, the front wheel is NOT straight when leaned over in a corner. HUH? yup. if memory serves, your front wheel points slightly toward the inside of the turn.

 

well, what the heck is up with that??? now Willy said it does this because of the trail. funny that trail keeps the wheel straight when up and down, yet, makes the wheel deflect inward when leaned over. i'm gonna have to draw some diagrams for the geometric relationship there, i think, but, the weight of the bike being applied sort of forward of the axle or the forks being angled less than the steering stem, if you can imagine this, would tend to point the wheel toward the inside of the turn when leaned over as the steering head becomes a lever or hinge itself.

 

regardless...the bloody front wheel isn't in line with the rear!!! does noone else think that sounds just a little weird? the bike finds equilibrium at lean with the front wheel turned toward the inside of the turn?

 

HELLO! WOULDN'T THAT MAKE THE BIKE WANT TO STAND UP?? TO COUNTERSTEER UP??

 

and might that be the force counteracting the force of gravity? just enuf "countersteer" to keep the bike from falling down? if so...

 

that would mean that the balancing force at lean is EXACTLY MOMENTUM AND INERTIA.

 

sorry, woody.

 

and the bike tracks a circle because the bloody front wheel is steering into the turn! just like a car.

 

anyway, i'm sure the gyroscopi forces help to keep it all stabilized at that point as well.

 

and what about the momentum of the bike being flicked in? what about that torque? what happens to that energy? (conservation of energy here folks?) what "catches" the bike when rossi flicks it in hard?

 

what if you welded the front steering stem, that is to say, welded the front wheel straight? assuming you could get the bike to lean over at speed with your body weight, or something, would it still turn, roll in a circle? would it go straight? would it fall down? hmmm...

 

it all fits with my momentum theory of countersteering. but i have absolutely no proof. someone want to weld the wheel on a bicycle straight and try it out?

 

also, has someone tried the hang off at speed and does the bike lean the other way trick? why does hanging of in a corner require less lean angle? maybe woody is onto something there...hmmm.

 

well, enuf of this newtonian nonsense. i'm gonna go check out parallel universes, M theory, and hyper-black holes on the science channel. big tuesday evening with my remote.

 

:P

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I think you are putting to much faith in gyroscopic forces. There is certainly a role, but you can discount momentum. Compare a bike on a stationary roller vs. riding it down the street. Or just spin a bike wheel in your hands and see how gyros react. There is not enough force there to keep you from falling over.

 

The problem with Physics is you need to simplify things, which has its problem. For example, the rear tire is a gyro but does not counter-steer. It is locked in place - of sorts. Tilting a gyro as the effect of making the gyro want to pivot - like the front wheel - but it can't so it imparts the force into the rear suspension and twists the bike. Did you ever think of the rear tire twisting the bike into a corner? People love thinking about the front wheel as a gyro - it is comforting - but never think about the rear. If you think the front gyro is that powerful, imagine what the rear is doing?

 

The front wheel is never straight in a turn because there are forces on the bike. Gravity is trying to pull it down and monentum on the tangent. I would think there are very few times - if any that the front wheel is ever perfectly straight.

 

Add in all your mometums, frictions, etc. - and don't forget the coriolis effect - and maybe you can model things to some extent. BUt if you are wrong, be prepared to fall. Diversion - Coriolis effect is what makes toilets flush backwards south of the equator - simplification. There is a famous physics story re: the Falklan's war and how the British failed to account for the change in coriolis effect resulting in their various rockets missing their targets. My point - there are forces out there we often forget or ignore which can come back to bite us in the arse.

 

More ot the point -

 

I've been led to believe, that in a turn a bike pivots around the combined bike-rider CG. You can take a line from the rear wheel, through the CG to roughly 2/3rds up the front suspension and that is roughly what the bike pivots around. Hanging off moves the CG which helps increase the turn rate, but then this is offset by the torque issue which may be causing problems.

 

Now a CG that is higher is a bike as the effect of being moved father inboard when the bike is leaned over - hence the bike will turn quicker. Think dirt bike or Aprilia. Lower the CG and when you lean the bike ther eis only so far it can go. Think cruiser.

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hey jrfuisz,

 

how fast can you turn a motorcycle wheel with your hand?

 

a little less than parking lot speed (10mph) where countersteering DOES NOT WORK. nor does the bike lean over. it acts like a car and and turns in the direction you move the handlebars while remaining in an upright position. in my opinion, because the momentum trying to knock the bike over the other way is small enuf that you can overcome it by shifting your weight and counter it with small turning adjustments. balancing with an effort. (if you did let it countersteer over, it would fall. and THIS intutive knowledge, this FEELING that the bike will fall over is EXACTLY what makes learning to ride a two wheel vehicle in the first place such a weird and freaky thing. and, frankly why 'training wheels' are kinda stupid. except to let one overcome the jitters and get used to being on the bike.) why is balancing utterly effortless as you go faster?

 

anyway...

 

no 'faith' in gyros here. pure empirical data, mate. try something that spins a bit faster. like as fast as a motorcycle wheel at speed.

 

have you ever held a pair of gyroscopically stabilized navy glasses (binoculars)?

 

why do satellites spin? why are they and rockets stabilized by gyros? why does a spinning top stand up?

 

i think there's enuf bloody force to keep you and ten of your best friends balanced, in concert with the trail effect of the geometry and momentum, on a motorcycle at speed. ever see those old pictures of the guys building human pyramids on a motorcycle? i'm not saying it can't be overcome...

 

in any case, i do not contend that gyroscopic precession has anything to do with turning into a corner. that was Woody's post. (and speaking from experience, you can't trust the bloke's intentions. he might just be yanking your chain. i mean he can be a bit of a cheeky wanker :D ) anyway, i agree that precession may have some effect, but, i think that effect is secondary to the overwhelming force of MOMENTUM combined with the compound lever of the front handlebars and steering stem when flicking a bike into a corner. but, who knows, i could be wrong.

 

what i am saying is that gyroscopic forces STABILIZE the bike. and YES, most definitely, the gyroscopic stabilization of the rear wheel must be overcome to lean into a corner.

 

if you believe that there is some other reason for a bike to balance, please tell us what it is.

 

moving on...

 

why can i use just a little force with my fingers to reverse the spin of water draining in a toilet or sink? the water 'tends' to spin that way. it's easily overcome. if your hand was a hundred miles wide you could probably reverse the rotation of a hurricane. i believe the coriolis force is relatively weak compared to the forces we are talking about.

 

back to gyroscopic forces...and in all fairness, i may be using the term incorrectly, perhaps angular momentum is more accurate, as you can think of mass and inertia, but...

 

why do stock cars all turn left on ovals and superspeedways? do you think this is an arbitrary decision? like the good ol' boys were sitting around one night with a jug o' shine and flipped a coin?

 

what direction does the crankshaft spin in a stock car motor? a very massive hunk of metal turning at thousands of rpm. how many rpm in a bike wheel at 10mph? 50rpm? 60rpm? 70rpm? like, way less than a hundred?

 

anyway, i think i've made my point. please, tell me WHY it's wrong. Seriously, you said, "...you can discount momentum." ok, tell me why.

 

 

 

 

 

The front wheel is never straight in a turn because there are forces on the bike.

 

ok. i'll buy that. can you be more specific? which forces exactly are you referring to?

 

 

I would think there are very few times - if any that the front wheel is ever perfectly straight.

 

Really? um...ok. i hope it's pretty straight when i'm doing 150+ down the back straight...

 

 

and...

 

a bike on a stationary roller is just that. stationary. i thought about this last week because it seems logical. untie a bike on a dyno and watch it fall over. just one thing...even with driven rollers in the front, heck, even if you make a rolling road, it would have to move in all directions at phenomenal speed to imitate reality. otherwise the whole trail and momentum thing is gone. sort of illustrates my whole point. in any case, not a good experiment. it is very...simplified.

 

seriously, i try not to MODEL stuff. i try to keep it real. sometimes it helps to have an analogy or scalar/vector model for analysis, but, i haven't used any so far. and that's my whole point. i think it can be understood without the math. i mean, IF you actually WANT to understand it. for many people, the question, "How does this work?" is answered best by saying, "It works just fine".

 

anyway...

 

as for your last two paragraphs....

 

i don't get how the bike pivots around the c/g except, perhaps, during turn in. mid corner, the pivot point is about fifty or a hundred feet or so to the inside of the turn. depending on the radius of the turn.

 

why does hanging off increase the turn rate? and by turn rate, do you mean the speed at which the bike flicks in or how fast it will corner?

 

what torque "issues" are you referring to and what "problems" may they be causing?

 

 

and i agree that a higher c/m gives momentum a longer lever to work with during the countersteer process and that a low cruiser has a lower c/m hence a shorter lever. but we've covered a lot of this in some previous posts during my last vacation back in december/january. check out 'rule #1' and 'center of gravity high or low' on page 2 of the cornering forum.

 

in any case, if there's something in particular you don't get about my theories...please ask, and i'll try to explain them better.

 

if you want to do some informative reading/research, try going to google and typing "physics, education". heaps o' stuff there, mate. i found a couple cool sites for the laymen.

 

good riding to you

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RE: gyros -- I don't think there is any disagreement, just the realization that Gyro's are not the main - or perhaps better to say sole - force holding you up. A Gyro to be usefull in keeping something balanced has to have a pretty good weight compared to the object. Your wheels/brakes don't weight that much relative to the bike and you. Mometum plays a large part - actually the laws on conservation of momentum - in keeping you balanced. Think of non-gyro based applications where moving forward makes it easier to balance - ice skating? ski bikes? I'm sure there are better examples. I don't have the answer on the relative ratios of the forces, just that there is major force at play - momentum - that makes it possible for the relatively weaker force - that of the gyros - help balance the bike. Don't get me wrong, they both play a role. I merely pointed out the back wheel, because it is also a gyro yet it is fixed relative to the bike. People who think a cycle is a boig gyro tend to think only of the front wheel as making it possible to stay upright and forget about the rear which is fixed.

 

RE: turning pivot Although I have a degree in Physics - so I'll skip the internet reading - I'm not going to profess to understand all the issues involved in why the bike pivoting around the CG. That "knowledge" comes from an article in one of the UK magazines - Superbike, Bike or Two. Article is 4-6 months old - if I can find my copy I'll get you the cite. The bike pivots around the combined rider-bike CG. It is the rate at which the bike is twisting - someone noted that the direction of the front wheel did not really match what the bike was doing. That is because the lean angle vs. combined CG is twisting the bike - that is what is turning you. I can do a flying V formation and drive in a straight line. The mere fact that a bike is leaned over does not mean it turns. It is the relationship between the wheelbase-2/3rd line and the CG that is twisting the bike. In the flying V formation the combined CG is over the wheelbase line - it has to be or you'd fall over. When momentum allows you to displaces the combined CG to the inside of a turn the bike turns.

 

The front wheel gyro is what leans the bike over. Once the lean angle is set, the combined CG relative to the wheelbase-2/3rd line is what the bike is twisting (turning) around. The bike has no knowledge of the corner etc. It will twist at a given rate based on the information it has. The bike does not know where the inside of the corner is. You as the rider equate the radius of the road with the rate that the bike twists/turns. That is all you.

 

Take a lean angle and plot the CG - the longer the distance from the wheel-base - the line from the rear contact patch to 2/3rds up the front suspension, the quicker the bike turns (per a given speed and lean angle) - assuming my recollection is correct. Leaning off increases the CG's distance to the wheelbase, which is why is turns quicker for a given lean angle. If I find the article, I'll post the cite. It was alittl eshort on theory, but pretty good nonetheless.

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... if memory serves, your front wheel points slightly toward the inside of the turn.

Agree. Didn't we cover this in the steering input thread...?

 

HELLO! WOULDN'T THAT MAKE THE BIKE WANT TO STAND UP?? TO COUNTERSTEER UP??

No, it would make the bike turn. Why? Because the bike is leaning and in balance. To counter steer the other way, you need to unbalance the bike by turning the wheel a little further.

The reason a bike turns is because when you turn the bars you unsettle the bike (the front wheel heads off in one direction, whilst momentum tries to keep the bike going forward), the bike tips over and when you release pressure on the bars, the steering geometry forces the front wheel to point into the corner.

 

The gyroscopic forces are minimal. Steering geometry keeps the bike upright.

 

However, the bike is still being pulled toward the outside of the corner, and this force acts around the centre of mass of the bike and rider combined, which tries to stand the bike upright. This is balanced by just the right amount of lean angle for a given speed and desired rate of turn (line). Speed up and the force trying to stand the bike upright becomes greater and to keep the same line you need to counteract this by leaning more (or the bike will stand up and you will be forced to take a wider line).

This why a slow bike can turn tighter than a fast bike. A fast bike simply cannot lean far enough to counteract the force pulling it toward the outside of the corner, and this ultimately limits the speed with which the bike can take the corner (and is also why you can take a corner faster on a featherweight 250 than you can on your heavyweight R1).

 

If however, you move the centre of mass toward the inside of the corner (by sitting off the bike), you can take a tighter line for the same lean angle, or to put it another way, you can use less lean angle to keep the bike following the same line.

 

and the bike tracks a circle because the bloody front wheel is steering into the turn! just like a car.

Of this, we agree, wholeheartedly!

 

what if you welded the front steering stem, that is to say, welded the front wheel straight? assuming you could get the bike to lean over at speed with your body weight, or something, would it still turn, roll in a circle? would it go straight? would it fall down? hmmm...

It would fall over as soon as you set off. You'd never reach a high enough speed as the steering wouldn't be able to self-adjust to keep the bike upright. Even if you could somehow get the thing rolling along in a straight line, as soon as you unsettled it in any way, it would fall over. Gravity would see to that. No, it wouldn't turn.

... but if you try it, I'll pay to watch.

 

 

Racer, I like these discussions. You're a crazy guy, but you're alright.

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whaddya mean crazy? you mean like wild and crazy? lots of fun at parties and the pub?

 

or like maybe i oughta be locked up crazy....

 

um, don't answer that.

 

ok. i've just finished a bit of research on the gyroscope thing (finally). little bit of reading. little bit of experimentation. so...now i must pay the price of moving beyond the scope of my knowledge in my last post or two. i knew i should have held off. anyway...

 

pardon me while i eat a little crow. i'll just mumble around a mouthful here...

 

ok, after a little experimentation with a bicycle wheel which i can spin pretty darn fast, i am fairly astounded at how powerful the precession thing is. wow. like damn dude. i will need to to rethink this whole deal a bit. i am astounded at how hard the bloody thing leans over. at the moment i have no idea how to resolve the forward momentum of the bike with the conservation of angular momentum of the front wheel.

 

AND...

 

leaning the back wheel over also produces an equally powerful gyro turning force.

 

and worse yet, the "stability" thing was a bit elusive. sort of a 'yes, but'...thing. that's on the back burner. i am told that the defying gravity trick of tying a string to one end of the axle and hanging the spinning wheel vertical from one end of the axle requires university level physics to explain. i'm still reading the high school stuff. so...maybe jrfuisz, having a degree in physics, might have a go at explaining it in simple english for us little people.

 

the momentum/trail thing is looking better all the time. more crow i'll have to eat from last freaking year if jr doesn't save my butt...

 

and hows come a bicycle or chopper with seriously negative trail (leading axle) still balances, if a bit less stable? huh? yeah...answer me that one, mr science! <_<

 

in any case, after some more reading on the circular motion thing, yeah, i'm still with the front wheel steering into the corner being responsible for continuing the arc after turn in. and the friction at the contact patch being the centripetal force. and i must have missed the steering thread. but i prefer the epiphany anyway. the rush of discovery, as it were. the adventure of exploring the unknown, even if it's only unknown to me. feeling like, "yeah, i coulda been newton if i'd been alive four hundred years ago..." (like a fig newton). pay no attention to all those footy prints on the path...no, really, you're the first one. keep the kingdom, mate. i'll trade my horse for a frontier!

 

on the fact that the front wheel is out of line creating an upward force, sort of like just enuf counter-steer force to balance against gravity or something...might not be the right way to say it from a pure physics pov, but...i mean, yes, the system is obviously in equilibrium, but...ok, why doesn't the bike fall down? the inertia of the forward momentum? which we have been sort of blaming for the countersteer initiation. (perhaps not so correctly) but, i'll try to rephrase that feeling better somehow tomorrow.

 

in the meantime, the conservation of momentum thing is starting to decimate my whole theory of counter steer. i mean, i suppose with all that precession happening, it doesn't take a whole lot of energy away from the forward momentum of the bike anyway. just a wee bit, perhaps....

 

but i started all of this as an alternative to gravity having a longer lever being responsible for how fast a bike turns in....oh, man. please, don't let me have to eat that, too.

 

hey, so maybe i have a future in sales....how does that work? well....how do you want it to work? eh?

 

i'm not sure i agree or even understand what you're on about with the c/g stuff and 250 vs r1 thing, woody. but, i can't really think about it now.

 

 

and i can't get quite get a grip on the twisting bike thing jr...unless you mean like twisitng around that c/g-wheelbase-contact patch line thing you're on about as it leans in? i need way more on that.

 

 

anyway, it's late. i'm tired. i need to sleep. my brain feels like it's going to explode because it turns out the bloody world IS flat after all...

 

i know i just need to get beyond the attachment thing and i will transcend the whole deal tomorrow morning...but for now, i need to go home and rethink my life.

 

:blink::blink::blink::blink::blink:

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geezer? GEEZER? who you callin geezer, MATE? pukekohe raceway outside auckland city next december...we'll just SEE who the geezer is! ;)

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The simple explanation of what is going on is what Code does in his class. It is pretty amazing how he boils down some complex concepts into plain english and then has drills to help you learn what and why something happens.

 

I will clarify one point - although they all could use it - the line from the rear contact patch to the 2/3rd mark moves. The front point is not fixed - 2/3rds is a guide. The movement is based on a number of factors - according to the article I remember reading. Which gets back to the school's "stability" focus. If the bike's suspension etc. is stable the line that dictates rotation does not change - as much - and thus our little brains can begin to connect the dots - matching the lean angle, speed, rorad, etc. Code has managed to isolate the various key inputs and then figured out lessons to help program the brain.

 

His first lesson on steering is really a two-fer in that he shows counter-steering but also the need to lean with the bike. I think the second point is where people get confused and have come up with the "myth" that lean steers the bike. It does and it doesn't. Lean will never initiate the turn, which is the no-BS bike lesson. Lean will, however, make the bike turned (i.e. the movement of the CG will) which gets into the lean lessons - Level 3 - which I hope to take at some point.

 

On the twisting concept - your (or someone's) flying-V formation is a great example. You may just not have realized how profound your observation was. "lean" does not alone make anything turn. Lean vs. CG is what is important. How one pivots around another is conceptually difficult, but you already made the observation with the Flying-V.

 

If I can think of someway to feel the twisting concept, I'll post it.

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hey, thanks, jr. let us know if you find that article.

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... or we could just dip our hands in our tight little pockets and pay the man to tell us.

 

Later in the year (when the arctic Melbourne weather finally warms up) I'm planning on taking levels 2 & 3 over a weekend at PI. I'm sure Monsieur Brouggy can sort out my little demons :D

 

Some interesting trains of thought though guys.

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Yeah, mate. That's what I thought I heard, too. The late bell. Best of intentions and all that. It's been fun, but...apparently...well...

 

Time to go back to school. (I don't FEEL tardy.) :P

 

I'd love to check out PI. I've never been hit by a seagull at speed before. :o

 

Stay in touch...young man. Summer's just around the next bend. B)

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