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Lnewqban

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Lnewqban last won the day on August 8

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About Lnewqban

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  1. Lnewqban

    Corner Exit Body Position/Street BP

    About your #2 question: Your priority for street riding should be safety, which has more to do with high alertness, with good judgement of entry speed, with understanding of traffic situations and with proficient visual skills. Your body position should be such that it serves as a good base for those things, it should be comfortable, it should keep you in total control of the machine. The extreme body positions that you see in track practices and races are not really necessary if you ride within or not much above legal speed limits. The lean angles and cornering forces on your tires should be moderate, so you will always have a safety margin or reserve to use in unexpected road hazards or traffic emergencies. You can experiment with leaning only your torso and head into the turn or even hang off your hips some, finding your most comfortable and safe body position. I would avoid dragging knees on public streets, but would know how to increase leaning angle and assertively swerve as emergency maneuvers.
  2. Lnewqban

    timing of steering input and chassis attitude

    I believe that the only reason for steering to be less accurate is a survival reaction of one hand fighting the other. That does not mean that we should reduce or eliminate the steering torque produced by one of the hands, but that we should observe that potential SR. Your bike my have a under-steering tendency, due to geometry or tires or tire's pressure. I would experiment with lowering the front end some and/or raising the rear end, in order to reduce the trail of the steering some. That would reduce the tendency of the steering to remain on a straight trajectory.
  3. Lnewqban

    timing of steering input and chassis attitude

    Basically, the same two processes happen simultaneously, only that in a shorter period of time than for a lazy turn. The front suspension and tire are loaded because deceleration, then that load caused by deceleration gradually yields as the load caused by the circular trajectory of quick-flick and tracing the curve rapidly increases (up to lower or similar value). You can find additional discussion about the quick-flick technique here: http://forums.superbikeschool.com/topic/4101-can-quick-turn-be-overdone/
  4. If your in-line four is carbureted and your V-tween is fuel injected, you should feel the difference. Besides the above recommendations, you could remove any current rotational slack between rear wheel and sprocket. If everything fails, I would experiment by carefully using a little bit of clutch or rear brake simultaneously at the begining of rolling the throttle on (not by the book or desirable, but better that upsetting the chassis).
  5. Lnewqban

    Consistent vs Accurate Lines

    Excellent post, Hotfoot. 😀 It very well explains the "throttle should be open as soon as possible" line in the book. Prior reaching maximum lean or slidding state, the bike is always following the trajectory that the rider commands it to follow via steering and throttle. Good visual skills help me with the spatial awareness regarding where the bike is located at any time in a succession of turns and helps me decide about the proper moments to brake, accelerate and turn in.
  6. Lnewqban

    Consistent vs Accurate Lines

    It could be that you are not following two fundamental rules of cornering: 1) Looking deep into the turn: You can only know that your trajectory is one foot off if you are looking close in front of your bike. 2) One steering for the whole turn: You may be adjusting your steering along the turn in order to achieve your goal trajectory. Think of the unintended consequences that you are creating if you are doing so, like diversion of attention, disorientation, over-stressing the front tire, etc. The way I visualize cornering trajectory: to me it is like shooting a ball into the basketball hood from a distance, you feel the cross-wind, you estimate the distance and the angle, you gut-calculate the whole flight of the ball and then you impart your best directed push hoping for the best. Sometimes you miss for little and sometimes you nail it. The hard mental, visual and calculation work in cornering happens prior the turn-in point, which is equivalent to the moment of actually pushing the ball. Let the bike "fly" describing that natural arc, free of unnecessary minute steering inputs and lean angle adjustments. Missing an apex for 12 inches may add a few feet to the corner's total trajectory, which is not a big difference for a bike that moves 88 feet per second (60 mph). Distracting your attention from proper throttle control and from reference points and from spatial location may slow your bike much more.
  7. Lnewqban

    Running off the road

    Welcome, Don! Very true, as soon as we are not 100% mentally riding ahead of the bike, the perception (false or true) of excessive speed and lack of time and available space overwhelms our fears of not surviving the situation. "A superior pilot uses his superior judgement to avoid situations which require the use of his superior skills" - Frank Borman
  8. Lnewqban

    Can Weight Shift Theory be debunked?

    You are welcome, Jaybird What you have been analyzing and trying to understand is very complex dynamics, reason for which most riders don't even bother learning the "why" of these things. The books that explain the whole interconnection of steering, wheels, masses, forces, etc. in a motorcycle are very dense to read and difficult to comprehend. I believe that there is value in understanding the basics of the Physics behind riding a motorcycle in a proficient way. It is difficult to explain those principles to inexperienced riders without going too deep into the subject and causing confusion. Most mentoring/teaching is limited to "do this to achieve that and go practice it". The experienced rider has the advantage of having tested what works and what does not, of having felt those forces and the reactions of the machines during enough time to make sense of those principles. If serious about this, by persistent observation during thousand of miles, an educated rider becomes more aware and more sensitive about the dynamics of riding and develops a finer input of all the controls and sense of balance. The Physics then becomes less abstract and more in harmony with our senses and minds. In order to function as a motorcycle rather than as a bag of potatoes, all the forces and moments acting over a motorcycle in different directions must be in balance. If our control inputs or road conditions break that balance, a brief transition period follows, during which the machine does its magic to self-adjust to a new state of balance. If that state is not physically achievable, a fall will follow. Counter-steering is a clear example of that: the rider intentionally steers the bike out of balance (out of its rectilinear path), inducing many reactive forces, movements and moments for a very brief period of time, forcing the machine into a new state of balance (onto a curvilinear path). If the machine continues on in one of the two states of balance, the rider is doing nothing or too little to modify those, like it happens in the No BS bike demonstration. If the machine is upset by incorrect control inputs from the rider, like closing the throttle during a big rear tire slide, the machine can go from stable cornering balance to unstable transition to out of balance (highside fall) really quick. The speed of the motorcycle is very influential about the steering, gyroscopic reactive forces, rolling and balance, reason for which counter-steering is so powerful in a superbike at high speeds, but almost negligible for a trial bike at walking speeds. http://www.dynamotion.it/eng/dinamoto/8_on-line_papers/effetto giroscopico/Effettigiroscopici_eng.html
  9. Lnewqban

    Can Weight Shift Theory be debunked?

    Talking about chairs, it has occurred to me that we can discuss the actions of monkeys (passengers) in sidecars races. By moving around for each corner, they do what you describe about your folding chair: they relocate the total or combined center of gravity as far from the motorcycle or as close to the rear tire as possible. Rather than trying to make the motorcycle and sidecar roll, they compensate the natural rollover tendency during fast cornering as much as possible. That rollover tendency is induced by the combination of centrifugal effect and height of the center of gravity respect to the road. A regular sidecar could be comparable to the situation that you have pictured above: a motorcycle with a dramatic asymmetrical weight to its side. Would the bike yield to the induced roll? Let's say that thanks to the third wheel, that weight does not roll the bike over and instead keeps it vertical. If we weld the steering to the frame keeping the steering bar perpendicular to the bike and then make the bike and sidecar gain speed on a straight trajectory, the contraption will describe a straight line. As the bike happily cruises along, if we suddenly remove the sidecar wheel, even with the stability induced by the two remaining main gyroscopes of the contraption, that asymmetrical mass or weight will be able to roll the bike until the sidecar axis hits the ground (the lateral balance will be lost). The bike, even while leaned over, will try to keep going along the straight line (assuming no dragging forces from that dragging axis) because the steering has not changed. Riding with a Motorcycle Sidecar: http://www.steves-workshop.co.uk/vehicles/bmw/sidecar/riding/sidecarriding.html Yes, a substantial weight with some lateral leverage is able to roll a motorcycle in movement or tip the stationary chair of your example over. Nevertheless, without the complicity of the steering capability, the bike will not turn, even if leaned over. The following video shows that the steering capability of a motorcycle, with or without a sidecar, has a powerful influence regarding directing it onto either a straight or a circular trajectory in a precise and controlled manner ....... and what it seems more important: combined with speed and rider's skill, it is able to lift that asymmetrical weight and keep it balanced at will, even on a left turn, in which the centrifugal effect tries to take the chair down. The maneuver is known as "flying the chair". https://www.youtube.com/watch?v=k6ZSSPY32Jk
  10. Lnewqban

    Experiments with Shifting Gears and Turn Radius

    https://motomatters.com/interview/2012/04/12/casey_stoner_explains_how_to_slide_a_mot.html Casey Stoner Explains How To Slide a MotoGP Bike: "It's something that only works in certain corners in this type of racing, it doesn't work in all the corners. When it does work, sometimes it can be a bit scary; you can go into the corner, and if you make a small mistake when you are sliding, the finish of it can be a catastrophe. When your heart beats really hard is when you slide when you don't really want to,"....... "There's different techniques to different corners and when they should be used, depending on grip levels, and a lot of different things. Unfortunately, most of the time these days, sliding is not the fastest way, there's only some corners where it can still work." About teaching a 5-year child how to shift gears, I recommend you this reading: https://books.google.com/books/about/Casey_Stoner_Pushing_the_Limits.html?id=npA1AgAAQBAJ
  11. Lnewqban

    Can Weight Shift Theory be debunked?

    Unless you have a fixed fulcrum to exert leverage against, you move the bike away from you (roll it a little) as you move your body off in the opposite direction. The total center of gravity (yours plus bike's) remains along the vertical line that crosses the imaginary horizontal line that connects both contact patches. If the steering is kept perfectly fixed and aligned with the contact patches, the bike does not have a reason to turn. If instead the steering is free to adjust by itself, the geometry of the front tire and angle of suspension, combined with the total weight and gyroscopic reaction (please, refer to your video and see that a left roll of the bike induces a left steering) , will slowly turn the steering towards the side upon which the bike has rolled (only if steering angles, tire's profile and pressure are neutrally set, so there are no over or under-steering tendencies). That slight counter-steering will induce a balancing slow roll towards the side upon which the rider is hanging off and the bike will commence a turn. That is the same self-balancing principle that allows a rider-less bike keep going for a while while speed is relatively high. That is a very different situation than exerting "a force (weight) at a lever point away from the center of rotation". We are starting from an out-of-balance situation. In that case, the bike will be forced to roll due to the moment created by the total center of gravity being initially far away from the line that connects both contact patches. Either or not the self-balancing capability of the steering will be strong and fast enough to compensate for that initial lack of balance depends on several factors, such as magnitude of off-set weight, weight's lever, mass of front tire and linear speed of the bike.
  12. Lnewqban

    Experiments with Shifting Gears and Turn Radius

    Absolutely! That is the whole reason for the need of selective gears: to keep the engine rotating within the range of rpm's that produces usable torque (and work) for a wider range of rpm's of the rear wheel (which translates into forward speed of the motorcycle). Except during the brief periods of coasting and engine breaking, the work of the engine pulls the motorcycle forward against the resisting forces of inertia (during acceleration) aerodynamic drag (at relatively high speeds) and (when climbing a hill) gravity. The only thing that dramatically changes the torque (and work) that the engine can deliver is the "twist of the throttle": more entering fuel and air means more powerful internal combustion, which means more internal heat and delivered torque (and work). That is true for certain range of engine's rpm and until we reach the point of full open throttle (maximum intensity of combustion and delivered torque), which is what dyno charts show. The work developed by the rear tire is always the product of its rotational speed (rpm's) times the torque it is able to deliver, which is exactly the same value as the product of its linear speed (forward speed of the bike) times the rearward force exerted over the pavement. The value of the work developed by the engine is always a little higher than the previous one, as some energy (in the form of transferred forces down the gears and chain and sprockets) is lost in the links between the crankshaft and rear tire. When the bike is moving at sustained 60 mph on a horizontal road, the position of the throttle is fixed, allowing intake of the exact amount of fuel and air that keeps two forces in balance: pushing forward force and resisting rearward force. If the bike starts climbing a hill and the throttle remains fixed (work delivered by the engine remains the same), the force resisting the rotation of the rear wheel increases due to the addition of the gravity effect. As no additional work from the engine is available, the other factor of the formula (torque X rpm) must decrease, resulting in a new state of balance at lower rpm's. The natural reaction to that is the slowing down of the rotational speed of the rear tire and forward speed of the motorcycle and reduction in rpm's of the engine. We can only allow certain amout of that reduction of the rpm's of the engine before the engine becomes real weak. If we wish keeping the same on-flat-road during the climb, we need to open the thottle up (more work delivered by the engine translates into resuming speed). If the steepness of the hill is excessive to achieve a new state of balance, even at full open throttle (no additional available work), we need to sacrifice bike speed in order to increase force on the rear contact patch via dowshifting. Returning to your original question: When the bike is moving at sustained speed on a horizontal road, the two forces are in balance: pushing forward force and resisting rearward force. If you open the throttle up some (more delivered work), the bike will accelerate due to additional torque reaching the rear tire, until reaching a new rpm X torque balance. If you open the throttle up a lot, the bike will do a wheelie due to excessive acceleration and abundant traction. If traction is not that abundant, then the additional available work must go to break the grip between the contact patch and the surface, spinning the rear wheel.
  13. Lnewqban

    Can Weight Shift Theory be debunked?

    In order to communicate with the same terms, are you refering to the rolling motion of the motorcycle? Is your question limited to the reactions of the bike and steering and trajectory following a lateral weight shift of the rider? Sorry, I couldn't clearly understand your question.
  14. Lnewqban

    Experiments with Shifting Gears and Turn Radius

    Because all the gears and sprockets that link the crankshaft with the rear wheel act like a lever: the rotational speed of the rear wheel gets reduced while its applicable torque increases. For the same degree of openning of the throtle, resisting load and rpm's, the engine generates certain amount of torque or rotational force. We have to work around that more or less constant amount of torque, playing with the gears, just like it happens with a bicycle. For a greater resistive load (going uphill, for example), we have to sacrifice rotational speed of the rear wheel in order to have greater torque there; hence, we switch to lower gears. One trick for riding in the rain is to corner using a taller than normal gear, which "weakens" the available torque of the rear wheel, which creates an extra safety margin regarding any mistake with excessive throttle that could overwhelm the marginal available traction. https://www.youtube.com/watch?v=3Tc3VIDQvh0
  15. Lnewqban

    Experiments with Shifting Gears and Turn Radius

    There is more force applied onto the rear contact patch when the transmission is working in lower gears. On surfaces of poor traction (grass, dirt, etc.), the rear tire has more authority (breaks loose and pushes the bike around easier) when first or second gears are engaged.
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