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CoffeeFirst

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CoffeeFirst last won the day on January 26

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About CoffeeFirst

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    Cornering Apprentice

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    Male
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    Atlanta
  • Interests
    Track, road and off-road riding. Photography and videography. Physical fitness. Travel. Skiing. Time with family.

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  • Have you attended a California Superbike School school?
    Yes. Consider me an L4 devotee.

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  1. Yes, I see it now. It is a very slight roll off for sure. It is so slight I had to watch the rpm needle to pick it up. Very impressive throttle control! Thanks Keith.
  2. Very nice! Completely agree about 2-strokes being a ton of fun - road an early 70's Hodaka Super Rat (remember those?) as a kid.
  3. Here is Will's lap from 2014 … https://www.youtube.com/watch?v=TFjm8cJ-z9g Here is what I think I see, but check me on this. Will has a nice roll-on out of T2. Then rolls completely off the throttle and trail brakes pretty hard before he gets to the T3 turn point. It looks like he carries his trail brake past the turn point but ends it well before the first apex. It also looks like he is back on the throttle before the first apex as well and holds it essentially steady (just a very slight increase in rpms) through the middle of the turn and second apex. He then rolls on as he exits.
  4. I'm curious Cobie, what is your off-road / dirt motorcycle?
  5. Took a quick look at video footage from L4 training and CODE Race last fall. I roll on, have a slight roll off, then roll on again. Ditto on this comment by Hotfoot.
  6. If Eddie had to back out, wouldn't he have rolled off the throttle tightening up his line in relation to the corner versus running wide? On the other hand, I guess if he had to get on the front brake as part of backing off that could have caused him to come up and wide.
  7. Suggest watching it on YouTube here ... https://www.youtube.com/watch?v=omk5sHY2xwI&feature=emb_err_watch_on_yt To see the accident jump to 17:00 time marker. 17:45 shows it in slow motion. To pull apart what happened I think there are three things we could try to understand: (1) What was each rider's racing line coming into the corner and trajectory at point of impact? (2) Given their individual racing lines where was each rider's actual apex point for turn 1? (3) What was the relative speed and motorcycle attitude (i.e, accelerating vs decelerating / braking, going into more or less lean angle, etc.) for each? From what I see Kevin Schwantz is further to the left side of the track coming into the Turn 1 (right hander) and on a wider, faster, more open racing line than Eddie Lawson, who was carrying more initial speed to grab the inside line at the corner's entrance. Given the camera angle it is hard to see exactly where each rider's actual apex point was - they may very well have been charging for the same apex - but it looks to me like Eddie's apex point was a little earlier in the corner then Kevin's. Schwantz does carry more speed through the corner and is leaned over longer than Eddie, coming across Lawson's front tire with an apparent trajectory to cut off the inside line in the middle & late sections of the corner. After he hits his apex Lawson seems to stand his bike up as Schwantz comes across his front, but I don't think I would characterize it as a pre-accident panic pick up. In fact, when you try to go frame by frame it looks like Lawson's pick up may really be because they had touched (Kevin's rear wheel to Eddie's front), which would cause a reaction like Eddie's from all of us. I think my conclusion is Kevin came across too tight and clipped Lawson's front end in his effort to close off the inside line. However Lawson's intended trajectory may have been to move further to the left on exit given he was in the process of bringing the bike up, so not exactly helping matters. Not sure how this was ultimately evaluated by MotoGP officials but would guess it was just chalked up as a racing incident.
  8. yakaru, I'm not sure it is as much a question of friction being applied in more places (unless more 'keying' is happening) as it is the extent to which the contact patch 'coefficient of friction', at that particular moment in time (so factoring in the portion of the contact patch that has been disrupted) has not reached the point of 'slip'. In some of the articles I've read the point of slip is expressed algebraically and can be calculated (theoretically) if all the other variables in the equation are known. Dave
  9. Thanks, Dylan. I've read about these dynamics in various articles but have never seen them summarized in such a succinct manner. Very helpful indeed. I would add I think 'keying' may also be a dynamic property (in addition to static) given the extent to which keying is constantly changing as tire energy dissipation, surface and interior heat, abrasion / shearing stress, and load change. For those who may be interested in the engineering details, one of the websites I found helpful is multiscaleconsulting.com. In their publications section are various papers on rubber friction and contact mechanics. A warning - their papers are filled with lengthy algebraic formulas supporting their analysis. I try to just focus on their key points and not get lost in all the math. I think the next evolution of this for me will be to learn how to read a tire so I understand what is happening to it and my traction/friction equation. Dave
  10. I've been trying to develop a better understanding of traction over the last couple of months as well. As such I've read a number of articles and technical papers about friction, and specifically, friction as it applies to the interaction between rubber and hard/asphalt surfaces. As I understand it, there are four types of friction: static, sliding, rolling and liquid. I may be wrong but I think the Amontons-Coulombs three laws of friction do apply to tires/rubber as it relates to "static" friction - tires may not be rigid but they are solids. However as soon as you move to sliding and rolling friction (which are the only applications we really care about) the three laws need to be modified for rubber specific properties and what happens between rubber tires and asphalt friction as heat and tire deformation change. Attached below are a couple of articles that help explain rubber-hard surface dynamics that cause rubber related friction to act differently. After reading these articles (and several others) I am now thinking about the "coefficient of friction" between tire rubber and asphalt, at any given moment in time, as being determined by the following ... For road surface … its material, texture, condition (including extent of surface oils/moisture present), temperature, gradient/camber. For tires … their material, construction, condition (also including extent of oils present), energy dissipation and resulting temperature (a hugely significant factor), stiffness, extent of flex/deformation and how well the rubber fills asphalt surface gaps and creates microasperity contact points (so yes, contact patch size matters), and finally tire pressure (which has direct impact on extent and rate of tire temperature changes and flex/deformation). Pressure or load between the tires and road surface … from both vehicle weight and riding forces (ergo cornering forces) The list may be missing a few things, but I think it hits the major elements. And since cornering force has such high impact, I think about the extent of "cornering force" being driven by a number of factors as well, including ... Weight Vehicle balance (shifting of weight, pitch and angle) Kinetic energy (speed) Corner radius and extent / rate of radius change (e.g. closing versus opening radius corner) Centrifugal force (directional inertia) Centripetal force (force acting on a moving body at an angle to the direction of motion, tending to make the body follow a curved path) Rolling resistance (from braking and accelerating forces) I'm still learning on all this (traction / friction) so feel free to correct me where I am off base. Dave Guidance-Rubber-Friction.pdf Rubber_Friction_and_Tire_Dynamics_A_Comparison_of_Theory_with_Experimental_Data.pdf
  11. Hi Roberts, Thanks for the insights. Very helpful feedback on center of gravity, velocity/comprehension dynamics, tire wear challenges, and the ability to lock in body position and focus with fewer physical action distractions. As CSS has taught us all, the less of our $10 of attention we spend on distractions the more we can focus on what matters (wide vision, throttle control, RPs, POT, hitting the apex, elevating our speed, etc., etc.). And the notion of a "constant sweet spot" is a pretty compelling idea. Thanks again. Dave
  12. Good for you! You'll greatly enjoy it. The CSS team and their training are outstanding. And as someone who started track riding in his late fifties, it is "never too late to teach an old dog new tricks" as they say. Dave
  13. Agree electric bikes are here and will only get better as technology continues to advance, especially for track riding. Troy Siahaan wrote a couple of excellent articles recently in Motorcycle.com on the Energica Ergo Corsa and Lightfire LFR19. Worth a read. Roberts, very interested in your thoughts on the Zero SR/F's weight (498 sounds) and center of gravity when you are riding at a quick pace and flicking the bike from side to side.
  14. Hey Cobie, Just read through this entire thread. Think I have followed this. Lots of great points being made by various folks, but I want to make sure I understand your core points and line of thinking. To recap: 1) Everything starts with the realization there is something to be learned. 2) In order to learn you need to delineate the effectiveness of various ”technologies” connected to what you are trying to learn. Can I infer the term "technologies" to be broadly defined as actual technology, dynamics, solutions, approaches, methods, techniques, etc.? I think about this concept being important so as to ensure you are learning the best solutions, or from the best advice, available at the time. 3) There is a hierarchy of information on the topic you are learning. Not all information on the topic or issue at hand is created equal. You need to focus on the most important information or elements. 4) It is critical you truly understand the information. To your point about "solid understanding of key fundamentals" by the pros. 5) There is a time and place for stepping back and applying critical thinking skills (e.g. back in the pits between sessions evaluating what was/was not working on track and why, and determining what you need to adjust). 6) Practice matters …so things become instinct and matter of course. As very well said by sfdownhill … "train until you get it right, practice until you can't get it wrong". Anything I am missing in your train of thought? To me this all seems logical. In many respects you could have called this thread "The Learning Journey". To that end, the only thing I would add for those who are looking to race or really focused on reducing lap times, is the concept of leveraging data and analytics to find areas of improvements. For lack of a better term call it "the need for highly effective feedback loops". Now doubt, doing everything above is critical to learning, getting better and can carry you a long way. But I think putting measurement methods in place and analytics to work to help identify improvement opportunities can be powerful (and I think even necessary at the upper echelons of the sport). I think about the 2D sensors and software tools I've seen and how insightful all that can be about where one is leaving time on the table if you will. Dave
  15. If the 2020 track rotation and timing generally mirrors the 2019 schedule then The Ridge could be a great July option for you. This year the Ridge had several single days and the 2-day camp offered over the course of six days. It is a wonderful track, but I'm also a big fan of VIR and Barber however Hotfoot is right ... heat and humidity can get pretty high during the summer months.
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