CoffeeFirst
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Posts posted by CoffeeFirst
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On 4/10/2020 at 4:37 PM, Cobie Fair said:
Quartararo, you can see he often keeps both legs into the tank under braking.
I have to believe a solid lock-on with both knees into the tank when braking hard helps (1) keep your arms as relaxed as possible, (2) keep your butt from sliding into the tank, and (3) has you in good position to quickly execute a knee-to-knee / hip-flick motion. Not sure how one could quickly execute a hip-flick when the leg needed to push on the inside of the tank when coming into a corner is dangling off the side. But, Moto GP and WSB riders are on a whole different level of body and bike control, I know, so the pros have to out weight the cons for them.
To the point above about it keeping the back end from coming around, if does often look like a stabilizing action by these pro riders as the rear of their bikes dance about. It seems like the more you see bikes sliding around the more you see legs out. For mere mortals I wonder if it would be considered a SR? I guess that depends on how intentional the action is or isn't.
On 4/10/2020 at 4:37 PM, Cobie Fair said:I hope he de-thrones Marquez.
Only a matter of time.
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9 hours ago, Keith Code said:
Look again. He rolls it off to get it pointed up the hill to #4 right before and just after the second apex
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.
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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.
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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.
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I'm curious Cobie, what is your off-road / dirt motorcycle?
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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.
11 hours ago, Hotfoot said:I find that if enter that turn on the inside I either have to slow way down, or I end up wide on the exit and that messes up the entry to 5.
Ditto on this comment by Hotfoot.
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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.
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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.
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9 hours ago, yakaru said:
In a similar way, a larger contact patch allows the friction to be applied in more places should there be any disruption in another?
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
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13 hours ago, Dylan Code said:
Per the Dunlop engineers tires grip in 4 ways:
1) Adhesion--the temporary chemical bond between the tire and surface.
2) Keying--the tire deforming and filling in all the nooks and crannies of the asphalt or squishing into the depressions.
3) Abrasion--the tire tearing from itself or wearing away.
4) Hysteresis--the energy storage and return by the rubber and partial conversion to heat.
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
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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
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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
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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
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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.
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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
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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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+1 on Hotfoot's suggested approach.
The only thing I would add is to not let the fear of rain turn you off from a particular track. I did three L4 days at The Ridge earlier this year. It rained on and off on two of those days. The rainy periods were some of the best training sessions I've had with CSS. The beautiful thing about the rain is it slowed everything down by removing the element of speed and allowed me to really focus on the drill at hand. I was amazed at what the rain did to help me better understand and manage the dialogue taking place between my right wrist and the rear wheel. Needless to say it really improve my overall throttle control. I know many other students walked away feeling the same about the positive value of training in the rain.
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Probably best if Cobie or Hotfoot reply to this, but in the mean time I'll share my thoughts.
The simple answer is "yes". What I experienced in L1 through L3 training is students learn a core concept in each classroom session and then immediately practice it during the next track session through the appropriate drill. While the human brain can learn through several methods, it has been proven that the vast majority of people do well with kinesthetic or physical learning, which is very much a "learn-by-doing" model. These active or participatory learning methods are great because students experience the concept / improvement / benefits first hand and have these wonderful "aha" moments for themselves, which in turn helps ingrain it in their knowledge base for the long term. It is important to note each track session focuses on only ONE drill or skill at a time - there is a lot to be said for single-minded focus when learning something new!
It is true one track session is highly unlikely to make you a master of a new concept or skill, but at least your initial personal understanding and practice of it has been achieved. Worth noting that even though my brain may fully understand a new concept or skill, physically mastering it on track takes endless amounts of practice, and even then absolute perfection is always just out of reach, especially when I am constantly striving to also elevate my pace. I think chasing perfection, one skill or drill at a time, is why so many of us periodically go back for more one-on-one L4 training sessions.
Dave
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I believe getting to 40 front / 60 rear weight distribution for corners is always the goal regardless of wet or dry riding conditions. As to which I would rather have slide, it would be the rear. Rear traction can be managed with throttle control. The front is far harder to control / manage once traction starts to go.
Worth reminding myself that even in sketchy riding conditions throttle control rule #1 still applies - I don't want to be playing with the throttle (open/close/open) while I am in a corner. It will just cause weight distribution, and hence the degree of my traction, to be abruptly bouncing around.
Lastly, while cornering forces and braking are the two principle dynamics that have to share traction, clearly riding surface conditions dramatically impact the traction equation. So stating the obvious, in wet conditions my cornering speed needs to simply come down, which brings me back to the fundamental concept of making sure I have set my "entry speed" properly.
Always amazed at how when I nail my entry speed everything else (riding line, weight distribution, apex precision, exit drive, SR avoidance, etc.) seems to go well - and when I get it wrong everything suffers.
Dave
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14 hours ago, Cobie Fair said:
Been universally liked by most for the position, and the handling
+1. Have ridden the new 2020 for three CSS training days now. There are so many things to like about this bike that there is just no going back to prior models for me.
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I rode Q4s for L4 training during the last 2 day camp at VIR. They were outstanding. Have no idea what lean angle was achieved but they provided tons of grip & confidence when fully leaned over with knees on the pavement. They will be my go to track tire when not on slicks. If you are considering giving them a try you won't regret it.
Dave
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A very interesting angle added to this discussion by Roberts above with comparing old bike (almost unridable) versus new bike (very ridable) capabilities and technology.
In many respects I agree with the statement "I would say that the ultimate goal of a rider may well be to learn to ride the bike to the edge of computer intervention" because a rider who can do this on a bike that offers little to no "smart tech" intervention would generally by the faster rider versus someone who can't (all else being equal).
The statement also raises a new question for me. Yes, we know "smart" interventions are really there to saves us from ourselves. But should we considered them detrimental to a rider's development and something to avoid testing … or should a rider learn to master them and leverage to his/her advantage for lower lap times (so just like many other aspects of the motorcycle)?
To what I think is a byproduct of Roberts' point, if a rider is regularly triggering the nanny functions then maybe that rider is not very skilled and the rider who masters that fine edge truly is. On the other hand, I've read various bike reviews by skilled moto journalist who are ex-racers, and you often read how they explore the capabilities of new motorcycle by adjusting and leveraging these tech interventions to get the most out of a motorcycle and achieve faster laps.
I think I lean to the latter, but maybe as growing track riders we need to start by just learning to ride well inside the edge of these interventions. Then once we have done that we learn to adjust and leverage them (meaning we let the interventions do their thing).
Dave
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On 9/13/2019 at 1:54 PM, El Colibri said:
I'll shave 10lbs + by deleting the catalytic converter, going with an aftermarket exhaust
+1 for less weight and more horsepower!
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On 9/11/2019 at 8:22 PM, Cobie Fair said:
First off, like the avatar..."Coffeefirst" .
Thanks. It actually has a dual meaning. First, I do love a great cup of coffee and rarely start my day without one. Second, the phrase is a simple self reminder to slow down, ask good questions and listen when diving into problem-solving mode. It first started years ago with a very wise admin I worked with who use to say to me "remember, coffee first" when she knew I was headed into a meeting to deal with a complex problem. The phrase has been with me for several decades now and usually serves me well.
Dave
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Sex Pistols vs Aretha Franklin
in Racing
Posted
The first video with Hickman - incredible! He must have the same, very rare, amygdala / frontal cortex neurology as Alex Honnold (the El Capitan free-solo climber) to ride so fearless. What scares the bejeezus out of 99.99% of us doesn't even move the needle for these folks. Fascinating stuff.