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JohnCBoukis last won the day on July 30

JohnCBoukis had the most liked content!

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About JohnCBoukis

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    Cornering Apprentice

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  • Location
    Cleveland, Ohio
  • Interests
    author, guitar, drums, photography, motorcycling

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  • Have you attended a California Superbike School school?

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  1. Is there a vacuum synchronization on this bike and has it been performed regularly? An imbalance in vacuum between the two cylinders will exaggerate the V-engine's poor off-idle response.
  2. JohnCBoukis

    Crash Analysis

    I did not think much about the fact that you were perfectly attached still, but should have. Here is a scenario: You are turning left but now countersteering up and come across the spring. It nails the outside of the front tire, perhaps lodging underneath, forcing the wheel to go hard left. That would countersteer you into the ground on the right. You would have perceived the sensation of a severe steering jerk methinks. Does this sound plausible? Is there any evidence of impact damage on that front tire or wheel?
  3. JohnCBoukis

    Crash Analysis

    I am no expert, just a rider. Since no one has responded as of this writing, I will happily chime in. If the rear slides out and continues sliding unabated, this will result in a relatively slow lowside, the same that you expected. If the rear begins to slide even for a moment, then regains traction, that can generate a rotational torque that flips the bike outward in a couple of milliseconds, resulting in a highside. That event is so fast and powerful that once it is initiated there is no recovery. You pointed out several traction hazards from that day. If too much throttle exceeds the available traction: Once the rear starts spinning, keeping steady on the throttle may keep the tire spinning, allowing one some chance of recovery as the bike sheds forward speed, while countersteering the bike upright. Alternatively once the slide has begun, certain actions like shutting the throttle quickly or using the rear brake can stop the rear tire spin, resulting in the regaining of traction and the bike flipping outward. I think that giant spring could have hit the bike in a couple different ways causing a momentary loss then nearly instantaneous recovery of traction. It could have hit the rear tire or acted like a kickstand hanging due to a band spring launching the bike upward briefly. Is the spring painted? If you could find such paint on the bike, that forensic evidence might be helpful. Here is a video of a highside. After the slide begins we can hear the rider chop the throttle, the tire chirp, the throttle rises then chops, the tire chirps a second time, then the highside. The sound and view of the erratic throttle and the tire gaining traction while moving sideways are the hints of why the bike then violently flips. https://youtu.be/JwlZiArfnYg
  4. JohnCBoukis

    Steer for the Rear - Ch13 of TOTWII

    The question is difficult because the problems are not obvious to me, some of the riders appear steady on the controls, and also some of these appear to be going uphill (although that could be the camera perspective) which would add helpful load to the rear wheel. This has me thinking about the bicycle coasting question. Are several of these riders coasting from too little throttle? You asked for force nomenclature, the rear would be unloaded, generating less friction than the centripetal force of the turn. The front wheel would have excess weight and thus adequate traction.
  5. JohnCBoukis

    Steer for the Rear - Ch13 of TOTWII

    1) "Would a unicycle corner better that a bicycle? Why?" A unicycle steers more sharply than a bicycle because of the bicycle's wheelbase. Of note is that the unicycle is countersteering and propelling from the same tire. 2) "Do you believe that a motorcycle doing a wheelie becomes a motorized unicycle? Please, explain." Not exactly. See #1. The wheelied motorcycle at speed, arguably because while it can "wobble" left or right, it cannot be accurately steered. The motorcycle must come back down to be countersteered from the front wheel. 4) "What forces are acting over the contact patches of a bicycle that is cornering and simultaneously coasting?" Jaybird mentioned centripetal force. Then there is the vertical component of the rider & bicycle weight. In this situation the friction on the bicycle tire contact patches is extremely small. I am most curious about this particular question and what we are supposed to understand from it. 5) "Regarding turning a motorcycle along a corner, should the lean angle be considered a consequence or a cause? Please, explain." I am thinking that "corner" in this case refers to a given, fixed path. If yes, for a given path on a given motorcycle at a given speed the lean angle is a consequence. I am not sure if I read this or came up with it in isolation: On a centrifuge I think of the arm that connects the motor and test tubes as the friction of the tires. The angle the tubes will take is a consequence of the motor speed, the arc, and the weight of the test tubes. Just the same I think of the motorcycle lean angle as a consequence of the speed, weight, and corner arc.
  6. JohnCBoukis

    Dirt vs Asphalt riding styles and technique

    1) Why do dirt bikers push the bike beneath them? "Because they can." Why do they not hang off? For what purpose would they do this? Can one flip a road bike side to side merely by shifting their weight? No, but one can do this laying the dirt bike beneath them, so this is actually an advantage in turning for the dirt bike. If you began a 180° from a crawl or a stop as dirt bikers do, this actually necessitates putting the bike underneath you. So I would say slow speeds and extreme turns physically necessitate this. To your point, dirt riders could hang off with their weight still on the outside peg, versus standing vertically on the outside peg like they do. However, that would be more work than merely laying the bike underneath, and their bodies would then be hanging out in traffic, traffic which is close or already colliding with them; more physical effort, with less safety, and for what purpose? There are lessons on this forum on how hanging off gains ground clearance. This is not a core problem on a dirt bike that has suspension travel designed to handle 5-story landings. One simply does not care about keeping a dirt bike more straight up. 2) You exclude the rut from your question but ruts and general degradation that quickly build up after the race start, and steeply banked turns are going to dictate many of the best paths on a given motocross track before other choices come into play. Any single gouge in the track surface is subject to directing the rider to another path that has more traction. A lot of motocross is correct obstacle execution at the correct speed (which is not always the fastest speed.) For the remaining rider path options I am going to make an uneducated guess that on a short motocross track that is only 5-8 meters wide, at speeds that are slow compared to road racing, the obstacle and turn execution will be much more contributory to the race times than an inside-out movement would be. Lastly, many obstacles such as whoops or jumps are approached best at a right angle. If one had to approach the road straightaway at a 90° angle, that limitation would completely throw away the path that clips the apex. Someone here described dirt biking as "point and shoot" and I think that says it concisely. The dirt has stops and starts and right angles but the road dictates a smooth, turn-interconnecting racing line. Thus they each have specific techniques which serve them.
  7. JohnCBoukis

    What happen here?

    I waited for someone else to jump in, but I will answer it. The rider is steering back and forth in a vain attempt to warm up the tires. To answer Hotfoot's question about effectiveness, here is an older post which contains cool references to studies: Note the comments on the effectiveness of the sun. The sun heats primarily via infrared light. This electromagnetic spectrum can penetrate deep inside of objects which convection (heating air and circulating it) or conduction (direct contact) will not do. Unfamiliar with the current technology, my research shows that some tire warmers now take advantage of IR.
  8. JohnCBoukis

    Seems you do not need wide radials

    The leader is perpetually sliding and holding the bike up with a flat foot on the inside. He is in a different mode from the street bikes, say dirt bike mode. He is not beating the limitations that bound the road bikes but he is using a different technique.
  9. JohnCBoukis

    Body to Bike Ergonomics

    They do not. The ab contraction is changing the model. It turns out this is a statics problem. Making the torso rigid is transferring the energy elsewhere, from back support applying vertical weight on the seat, to rotational inertia. These two are chocolate and peanut butter. Note that using the back to support the torso transfers the torso weight to the seat. That is what is going to change with the ab contraction. On the bike, if the abdomen is held rigid and the legs are held rigid (they are pretty rigid as they do not bend like the back), then the body will want to rotate forward, pivoting on the seat. The feet resting on the pegs prevent this rotation. So the weight the back previously put on the seat is now resting comfortably via the feet on the pegs. Experiment: Sit in a chair or on the bike, flex the abs, and lean far forward. Relax the abs then flex the abs. If you are sensitive enough you may feel the increase and decrease in force on the bottom of your feet, and with each change the opposite feel of force on the seat. Here is what I can think of: Functionally isometrics allows us to hold objects. If I hold a plate or a pen in my hand and do not move, that is an isometric. Holding our torso up vertically is similar. Design wise, one can become infinitely strong without any equipment by doing isometrics. Of course the strength is over a limited motion area, due to being applied at a point or over a very limited range. Also when injury causes immobility one can begin recovery via isometrics. If motion is painful, one can still build the muscle up. If one was trapped under an object that is extremely heavy, they may not be able to lift it in one motion. They can slowly lift it, hold it there, then lift it more. This combination of isometrics and motion allows us to do work that taxes us to our limits.
  10. JohnCBoukis

    Body to Bike Ergonomics

    Muscles can contract and generate movement or they can contract without generating movement. Ever do isometrics? The abdominal or core contraction you guys allude to would be an isometric. The muscles strengthen, and there is no movement.
  11. JohnCBoukis

    Maverick's riding style disected

    Too true! By my comment is in context of the discussion regarding Crutchlow's peak heart rate of 192 bpm and points such as Spaghetti's about avoiding excess fatigue. If this rate was measured since 2015 while on his Honda, CC may be desperately trying to get that rate down as he unwillingly fights his current bike.
  12. JohnCBoukis

    Maverick's riding style disected

    Crutchlow recently indicated that he is physically struggling with the RC213V, and provided the metric that his heart rate is 16 bpm higher than while riding a Yamaha: http://www.autosport.com/news/report.php/id/128431
  13. JohnCBoukis

    Intro To Css

    At Amazon they have Twist I in used but very good condition for $9.51, and Twist II for $11.98, both fulfilled by Amazon with free shipping if the order reaches $25. However, this rider needs to scrape up five more dollars than the given limit to make this purchase of both books. In speaking with my local librarian I learned that book borrowing in this area is far overshadowed by multimedia today. The person you are dealing with may be part of the generation that would tend to choose multimedia. So it may be an uphill battle pushing the book recommendation, but I personally would explain the advantages of the books that others mentioned, that they are more detailed than the videos and that they can be referred back to easily. Signed, Highly Biased Book Lover
  14. JohnCBoukis

    Street Skills And Road Engineering

    Maybe this could also use an additional sign warning of the curve and steep grade? Many times there is the additional factor of other vehicles tailgating the motorcycle and not paying attention. Since speed tends to not be a concern for the driver of a car or truck, for any such drivers not paying attention, there is the risk of them going right through the motorcyclist during the slowdown. Thus, your warning of the signage applies just as well to the follower as to the lead motorcyclist, yet another reason to seriously consider the sign change. Often here in the US the catalyst for additional signage is a certain number of accidents or deaths. Perhaps they mentioned this metric in the meeting? According to the local law, how many accidents or deaths would result in a change to this signage? A number of citizen complaints may not be meaningful to the council. I have seen such on the news many times, dangerous areas where people complained to the municipality and they did nothing. After two or three or four deaths, that same area looks like a Christmas tree, with warnings and even superior lighting. In fairness to the council, citizens probably request expensive things from them daily. In unfairness to their decision, it sounds like you are the expert witness in this case. After some of the conditions I have encountered, it certainly seems like traffic design is universally engineered for cars with motorcycles being an afterthought. Looking at this from afar it appears that the council's decision reflects this tenet too.
  15. JohnCBoukis

    Chicane Or Multiple Linked Turns

    One of the preeminent sport bike books that I read demonstrated chicanes extremely well, but I cannot recall which book it was. Committing what is an unspeakable act for me (I think I can type it though), I lost my notes from that book. It showed examples of individual turns and an optimal racing line for each one. It then connected those same turns and contrasted how an optimal path through the chicane differs from the paths of the isolated turns. I understand the concept but those diagrams demonstrate it well. If someone can help identify a reference with a good sampling of diagrams that illustrate this concept, that would be extremely helpful. Thank you.