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Lnewqban

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Everything posted by Lnewqban

  1. On the axis of pitch: All the three axis of rotation must go through the center of mass: that applies to a motorcycle, an airplane or any body with a mass that is forced to rotate. Of course, that is respect to the ground (an inertial point of reference); if you set a camera on the front wheel's axle, you will see the forks rotating some around it. On the need for smooth application of the brake: As you know, the maximum friction force that resists the tire from skidding is proportional to the force acting perpendicularly to both surfaces in contact, which is the weight being transferred on the contact patch (50 front/50 rear when coasting, 100 front/0 rear when wheelie). When you abruptly apply pressure to the front brake lever, the only traction that you have on the front contact patch at that very first moment is about 50% of what you have at the verge of a stoppie, which is 100%. Is that 50% traction enough to initiate the deceleration process? As explained above, that is circumstantial: you either lock the tire and lose steering or you force the non-instantaneous transfer of weight, which will allow you to use more traction for deceleration. Braking at 1G means that there is a force pulling the contact patch aft that is equal in magnitude to the combined weight of motorcycle and rider and that is decelerating the bike in 32 feet/second per each second (similar to gravity). At the very beginning of front brake application, when the weight distribution is still close to 50/50, you cannot brake above 0.5 G. The magnitude or intensity of a good efficient front braking goes from 0.5 G to 1 G in a short period of time, but never instantaneously. Copied form Chapter 24: "Snapping on the brake lever too quickly is not productive except for photos. Everyone has the feeling they can abuse the front brake whether they have ever locked it up or not. But there are only two real rules of front brake use and abuse: 1. Don't snap it on too quick. 2. If the front wheel locks up, loosen up on the lever."
  2. When a bike is decelerating, due to front brake (stress on the front tire's patch), throttle-off or rear brake (stress on the front tire's patch), a forward inertial force appears applied at the height of the CG. The height difference between the forces pointing aft and forward makes the bike initiate a rotation around its axis of pitch. http://www.motorcyclistonline.com/blogs/roll-pitch-and-yaw-drawing-line That rotation is resisted by the moment of inertia (angular mass or rotational inertia) of the bike, which slows down the max loading (vertical force) of the front tire's patch and the min loading of the rear's. https://en.wikipedia.org/wiki/Moment_of_inertia In other words, even when it is quick, it takes some time for the nose to dive and the tail to stand up. At the beginning of that process, the weight distribution is close to 50/50 on both tires, while at the end, it could be as close to 100 front/0 rear as the rate of deceleration is closer to 1G. It is only natural to roll-off first when the rear tire still has max traction for braking (50/50 condition), to follow with quick but gradual application of front brake (while bike starts nosing down/tailing up), to end with desired pressure on the front brake (once the nose-diving is complete and the front patch reaches max traction). If that sequence of control's input becomes a habit, no much attention about slowing down is consumed. For straight up bike / dry track conditions the sequence is quicker, for leaned bike / wet track the sequence is slower. Similar principle can be applied to acceleration or to quick deceleration-to-acceleration transition, but with the pitching effect in reverse.
  3. This is the way I understand throttle control rule number two in Chapter 6: Fine modulation of the throttle helps you read the forces that you feel more accurately. The advantage of that is that your entry speed will be more consistent and appropriate than if you grossly decelerate in a hurry (charging the curve), just to find out that your entry speed (at the end of that precipitate deceleration) is lower than it should be (because your senses were overwhelmed, you are erring on the safe side of entry speed). The error about the entry speed is more significant for any fast-entry turn, especially due to the aerodynamic drag explained by Hotfoot above.
  4. They know that lowering the CG is bad for lean angle, but they understand that less aerodynamic drag at high speeds compensates for that problem. Also, because the upper body must pivot around our shifted-over rear end, it is difficult to extreme-hang-off keeping your head as high as possible.
  5. What transfers some weight onto the rear tire is acceleration, which only depends on mass (the weight of rider plus fluids plus bike) and force pushing forward (torque to the rear wheel). Acceleration = Force / Mass By rolling the throttle open, we are feeding the rear wheel with the torque that is needed to achieve the recommended rate of acceleration (0.1 to 0.2 G). The statement of the book is only an example; you can feed similar torque or force in second, third or any gear that conditions dictate. Being G = 32.2 m/s^2 (acceleration of gravity), the recommended 0.1 to 0.2 G means that the rate of cornering acceleration should be in the range of 0.1 x G = 3.22 m/s^2 to 0.2 x G = 6.44 m/s^2. The above is hard to "feel" while cornering; which is the reason for the more practical reference in the book. Three more hints that may help you "fill in the gap of time": 1) The proper acceleration feels like you are gaining around 3 mph per second, regardless of the speed you are traveling at. 2) During that acceleration, you should feel a force pulling your body backwards. That force is the inertia of your body resisting the acceleration of the bike. The magnitude of that horizontal force should be around 10% to 20% of your own weight. 3) This video:
  6. Just copy the URL or web address of a particular video and pat it on your post. The bike will stand up out of balance, unless you increase the balancing moment via increasing the lean angle some via slight counter-steering.
  7. Have you seen such a thing? Some related experiments here: http://tonyfoale.com/Articles/RakeEx/RakeEx.htm
  8. You might learn more here: http://www.tonyfoale.com/Articles/Balance/BALANCE.htm
  9. The hanging off would work against a quick rotation around the cone. The higher the lean angle of the chassis, the smallest the circle that can be traced around the cone, due to the geometry of the steering at full lock. This link explains several reasons, if you are interested: http://amgrass.com/forum/practice-practice-practice/help-how-to-increase-speed-and-lean-angle-in-practice/ In this competition, minimum traced distances and high degrees of acceleration (notice the big rear sprocket) are more important than speed.
  10. I do follow your path of logic, but where are you seeing the statement in Twist II that the radius of your arc should be constant? It talks about getting the bike to hold a "predictable line" and says that "line follows gas" but I do not see anything that says you must maintain a constant radius arc. I don't see such statement either. May be I am reading it wrong, but it seems to me that other statements in the book lead me to believe that keeping a constant radius is a desirable thing: The book refers many times to decreasing radius turns as a bad situation to foresee; hence, constant or increasing radius are better situations. It also advises about using standard 40/60 throttle control as "the only reliable way to hold a constant line through any turn." (Chapter 4 / Hold it). It teaches that when using standard throttle "the only things that will change the lean angle of the bike to any great degree are a slide/catch action or steering input." (Chapter 13). I understand the rule number one for steering (Chapter 14) as no reason for the bike to deviate from a circular trajectory after we counter-steer to achieve the proper lean angle: "one single steering action per turn", that is it. Again, I may be reading all these statements incorrectly. I understand that the conditions of the road, or track or a race may force a rider to trace a line that is far from perfectly circular. To me, quick-flick, out-apex-out, 40/60 throttle control and hanging-off, are all techniques to make that radius of turn as big as possible, the suspension as stable and efficient as possible and to keep the lateral loads/stress on the tires as small as possible. Accelerating or coasting during the turn, any steering input to decreasing the radius increases the lateral load/stress on the tires and the lean angle must get bigger. Not combining that with strong acceleration is the point of this thread, IMHO.
  11. I just did read those portions of the book again: - Ideally the bike should accelerate in a turn = The speed of the bike increases some after rolling-on of throttle begins (as soon as possible). - A good and constant line through any turn allows the application of the golden rule: Once the throttle is opened, it is rolled on constantly throughout the remainder of the turn = The goal is to obtain the ideal 40/60 weight distribution. - One steering action is ideal = The radius of the trajectory of the bike should be constant (up to the moment to pick up the bike to exit). It seems that my choice of words was not the best: it is not that we want to increase the lean angle, it is that the lean angle becomes a little steeper naturally while we apply these rules. Trying to explain to Jaybird180 that "Adding throttle and lean angle at the same time" sometimes occur, not causing a slide when the combination is moderate. The lean angle is not something that we can select at will, at least not directly. The lean angle is the balancing reaction of the bike to the lateral (sliding) forces of cornering, which are the consequence of speed and radius of turn. More cornering speed } = Higher sliding forces = Steeper lean angle Tighter cornering radius It seems to me that in track talking, "adding lean angle" refers to counter-steering in order to quickly reduce radius of turn, which induces higher lateral forces and naturally a greater lean angle.
  12. Counter-steering always work. It is the only effective and quick way that we have to get the bike out of a lean at the end of a turn. As we push one side of the handlebar, we force the front tire to deviate its trajectory, which consumes some available traction. That deviation (in degrees) is very small, sometimes imperceptible. What consumes more or less traction is the speed of our input. The quickflick technique uses a lot of traction, but that is not a problem when the bike is near vertical. The key for keeping traction at 40 degree lean is to be smooth on the contersteering input. Please, read this: http://forums.superbikeschool.com/index.php?showtopic=3723 50 mph or 100 mph? The cornering forces on the contact patches are not determined only by the speed of the bike, but by the combination of speed and radius of turn. Any combination of those that forces you to lean 45 degrees, loads the contact patches with a lateral (sliding) force equal to the weight of your bike and yours (ideally 40% of the total weight on the front and 60% on the rear contact patch). As discussed above, slowing the bike down will make you fall into the turn, naturally reducing the radius of turn. However, that technique is less effective than counter-steering for high speeds (lean angle increases vaguely or slowly) and much braking load may be put on the contact patches.
  13. When cornering per TTOAW2, we are adding throtle and lean angle simultaneously. Rolling the throttle on constantly increases the speed (not much, just 2 to 4 mph per each second). If the radius of the arc of your turn is constant, as it should be, you will see a light increment of the lean angle along the turn. If you want your leaving speed/lean angle combination to be at the limit of traction, you need to moderate your entry speed accordingly. Now, whenever you are close to the limit of traction, you will need to reduce lean angle (increasing the radius of turn) in order to safely increase torque load on the rear tire or to increase speed. Because the same reason, if you need to reduce the radius of turn, you will need to slowdown some first.
  14. The recommended acceleration achieves an optimal weight distribution (more or less 40% of total weight of bike and rider on smaller front contact patch and 60% on bigger contact patch) and an optimal position for the front and rear suspensions (about half of each stroke) and an optimal clearance of the chassis (higher position during moderate acceleration). The increment of rpm's may sound different for each size and type of engine. It feels like you are gaining around 3 mph per second, regardless of the speed you are traveling at. Considering the gain of speed during the turn, you enter the curve as slowly as you need it to enter in order to leave it as fast as you want or can. The 0.1 - 0.2g only means that the force accelerating the bike forward (in addition to the force needed to overcome aerodynamic drag) should be 10% - 20% of the total weight. If that force is bigger, like the 0.3g of your example, then it is 30% of the weight; hence, the front tire and suspension are a little less loaded and the rear tire is a little more loaded than ideal. Nothing catastrophic will happen..... if you are not riding at the very limit of traction. Actually, you can wheelie out of a turn at a moderate angle of lean, in which case, 100% of the weight would be on the rear tire. All the above (weight distribution, suspension position, etc.) is more critical for turns that require extreme lean angles and grip. In order to understand the reasons to be precise and smooth for high performance riding, please, read this: http://www.motorcyclistonline.com/leaning-bike-code-break
  15. The book recommends 0.1 ~ 0.2 g acceleration to balance the load on the contact patches. That means that you should add 3.22 ~ 6.44 ft/s (2.2 ~ 4.4 mph) of speed for each second spent on the turn. Please, see these: http://forums.superbikeschool.com/index.php?showtopic=3645 http://forums.superbikeschool.com/index.php?showtopic=3665
  16. During the process of training or learning, the time that is dedicated to thinking and practicing is the key, in my opinion. Besides being dangerous, fast riding is not a natural thing; it must be learned while fighting our natural survival reactions. Any riding school, book, track day, etc. presents a set of rules, theories, best practices, tips, etc. that needs time to be understood. Some learn faster than others, but all need time to understand that set of ideas. Then, the practical part follows, during which the student tries to make sense or to match that set of ideas with a set of non-natural feelings, sensations, forces, etc. while fighting the fear of falling or crashing or simply being inadequate. Increased speeds reduce the available space and time to react, which makes those fears greater. Some feel less fear than others, but all need time to test their own mental limits while practicing and thinking about what is practiced. Unfortunately and due to practical reasons, time is not abundant during riding schools, track days, courses, etc. The student must use much of his own time out of the school to practice and to understand his riding, deeper and deeper. Besides having a clear mind and a correct attitude at that moment, the pilot reacted correctly because he had had years of thinking about and of actual flying. Same happens with practitioners of martial arts, they can react without thinking, because they have used much time to understand the theories behind a move and to make the proper reaction automatic, non-conscious. Both, the pilot and the martial artist have over-passed the point at which they were afraid of the unknown; they both had couches that showed that what it seemed to be dangerous or impossible, could not only be understood, but mastered. Copied from this article written by Keith: http://www.motorcyclistonline.com/blogs/embracing-mysterious-limits-riding-flinch-code-break "One of the primary purposes of training is to help a rider ramp up acceptance of the unknown. Any breakthrough in riding has some physical sensation attached to it. It’s the delicious price we pay to approach the unknown. .......... When you see a rider falter, you are witnessing in him the fear of the unknown. You see him flinch. Anticipation of some imagined bad result keeps us from moving forward into that uncharted territory of new sensations. When we flinch, we waver from our purpose to execute the control inputs necessary to achieve the intended result. .......... More often than not, the flinch can be overcome once it is identified. No one likes to waver, to give up or feel confused about something. Making leaps of faith into the unknown by hoping the bike will do your biding often finds riders biting off more than they can chew. Training lets you elevate your acceptance of that next level of rider confidence, speed and skill, cut down on the stress and increase your ability to get what you want out of riding. By finding limits and embracing the sensations that go along with them, you can exceed your current ideas of what you can do."
  17. Number 3 is not normal. The front contact patch grows when some (or all) weight is transferred forward (increasing tire-asphalt friction), but the trail is reduced, which makes steering lighter (it requires less effort). Trail is the distance that the front wheel ground contact point trails behind the steering axis ground contact point. https://en.wikipedia.org/wiki/Bicycle_and_motorcycle_geometry#Trail https://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics#/media/File:Bicycle_dimensions.svg
  18. Willing to comment, but....... sorry, Cobie; it is not clear to me what exactly you want to discuss here. My perception from your previous posts: 1) The physical and mental principles behind riding a motorcycle properly, as well as the technologies in the machine, are important to be studied and understood by the rider. You called it "the first step" in your OP. 2) Some of those principles are more important that other because they are fundamental for the understanding and application of the rest. You have called what "one really want to understand well, and know like the back of one's hand". 3) Few riders, couches, students, schools or free-advisers know or want to expend time and effort to learn and understand the "technology to riding". The same persons believe that they know enough to teach others, who then believe that any advice is solid and good. On this, you have stated that "There has to be an evaluation of the technology, how good is it, how effective is it". 4) Experienced/fast riders that attend your school show a high degree of resistance to learn or reasoning why things, bad and good, happen when piloting a superbike at high speeds. They seem to be more doers than thinkers, and are not willing to switch that approach to riding/racing simply because they are firmly convinced that they have been doing it well for 30 years. Hence your comment: "Thinking/reasoning, working stuff out--this vital. I'm looking at some of the potential building blocks, before we get to the doing part." I fully agree with rchase; any invitation to changing that approach could hurt the sense of self importance of a rider who knows that he/she is incapable of understanding that information or who believes that his/her riding is already proficient without all that reasoning. A person who wants to learn will always do all the research that he feels he needs to understand the principles and technology of riding: that is what Keith Code did when nobody bothered to think much about the science behind racing. "Nah,.... there's gotta be something more here"
  19. Just like the banking angle of any airplane, the lean angle of a motorcycle is the result of the combination of only two things: 1) Speed. 2) Radius of the turning trajectory. Even when your actual trajectory goes outside-apex-outside of a curve, it is still circular and has a more or less constant radius. Being limited by the geometry of the turn, the only variable with which you can play is entry speed: slower entry speed results in less lean angle, faster results in more lean angle, excessively fast results in your bike dragging parts and possible crashing. If you turn every corner into a max lean endeavor, that only means that, for the entry speed that you have selected, the bike will be describing a circular trajectory with the smallest radius possible. For turns that require less speed/lean angle combination or that are less tight, you will overturn the curve or proper line. Then, in the best case, you may be hitting an excessively early apex and subsequently running wide in your way out the turn.
  20. The total amount of momentum in a closed system (bike + rider) is constant. You push the bike away from you and the bike pushes you away from itself. Besides the inertia of the mass of the bike, we have to overcome the inertia or resistance to lean that the gyroscopic effect of both wheels have. In order to precisely and quickly push the bike to lean (rotate around its CG) and subsequently turn, you need a fixed point out of that closed system. That fixed point (fulcrum) is the surface of the track, on which we support our muscular effort via handlebar (lever), front end and contact patch of the front tire.
  21. Can anyone explain the proper timing for quick flick? While releasing the brake with some trail braking? While opening the throttle? Sometime in between? Trying to understand this article written by Keith Code: http://www.motorcyclistonline.com/braking-styles-motorcycles-code-break "Straight-up braking inspires less physical drama, but still demands intense attention from the rider. In some cases, completing the braking act before you turn is more difficult than trail braking to the apex. In this case, the bike's turning arc must be established before the turn is initiated. The ability to predict line, apex and exit is vital. This requires, among other things, superlative visual skills. In addition, quick and accurate steering is a must. The rider must have enormous confidence in front and rear tire grip before flicking the bike into the turn. Coordinating brake release and turn-in steering actions must be spot-on, or the suspension will rebound as the bike is entering the turn. This all requires deft coordination and impeccable timing."
  22. With negative camber, a little portion of the weight of the bike adds up to the sliding out (centrifugal) force of cornering. At the same time, the normal force that creates grip between rubber and asphalt becomes a little smaller. https://en.wikipedia.org/wiki/Friction#Normal_force The opposite happens for curves with positive camber. There are other steering effects induced by changes of camber: http://www.soundrider.com/archive/safety-skills/coming_unglued.aspx As for braking uphill and downhill, again, a portion of the weight of the bike adds up to the braking force (uphill) or reduces the effect of brakes (downhill): http://www.soundrider.com/archive/safety-skills/RS-braking3.aspx
  23. Respect to a vertical line, the lean angle is measured from the line formed between the combined center of mass or CG and the horizontal line connecting both contact patches. That combined center of mass is located at a point over the line that connects the CG of the bike (about the valve train of the engine) and the CG of the rider (about the belly button). That point is closer to the CG of the bike because the bike is much heavier than the rider. http://forums.superbikeschool.com/index.php?showtopic=3303&page=2#entry26514 That lean angle depends on only two things: speed of the bike and radius of the trajectory on the curve (radius of turn). The higher the speed of the bike, the greater the lean angle. The smaller the radius of turn, the greater the lean angle. If, as you stated, the speeds of the bikes were comparable, then the [bike+rider] carrying more lean angle must have been describing a tighter turn (inside the curve rather that outside). Therefore, both bikes could not have been at the same spatial point, like the overlapped picture may suggest to some readers. I have aligned the background (grass + electric cable) of each individual picture, just to show the actual trajectory of each bike. Based on all above, the [GSXR 600+rider] in the picture was at a lesser lean angle than the [sV650+rider].
  24. Some bikes are under-steering, some are neutral-steering (ideal) and some, like yours, are over-steering. The reason for that to happens has to do with the balance (or lack of) of the lateral deformation of both contact patches under cornering forces (camber thrust and slip angle). Things can get better or worse by modifying the pressure of each tire first; then, by replacing the brand/profile of the tires. In severe cases, changes in the geometry of the steering (higher or lower front/rear suspension-chassis) must complete the above mentioned. Riding faster only increases the angle at which the bike must lean and the deformation of the patches. Same for strong acceleration, with the undesired bonus of standing the bike some and tending to run wide, unless you keep pressing forward on the inside grip.
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