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Here is a similar illustration that might be helpful. The lines aren't quite as pretty in this one because these are the actual outputs from a math program to create Euler spirals. The lighter colored line shows an apex speed that matches the exit speed. This would represent a car that didn't gain any speed during corner exit even at full power. Some lower powered cars actually come quite close to this in high speed corners as the engine power just barely overcomes the drag forces.
The darker line shows a steadily increasing radius from apex to exit. The dark circle shows how the apex radius is a good bit smaller in order to use that acceleration potential during the exit. You can also see how the apex angle is later with the darker line.
To find out where your car might be you just have to compare its maximum lateral force vs acceleration. The lighter colored line is a car with no acceleration during exit and the darker one is a car where the acceleration ability matched the lateral ability. Even though the illustration shows it, even a formula one car does not accelerate as well as it corners however. Only something like a four wheel drive car with enough power to achieve wheelspin for the entire exit would use an apex as late as the dark line. If you have a data logger you can pull up your max lat/long g readings in different corners comparing apex to exit to see where you might fall in between the two lines.
Something else interesting we can take from the illustration is how close the entry lines are between the cars. Both lines are spiral shaped because both cars can brake as well as they turn. Taking the same concept then as in the exit, you can figure out why something like a rear brake only kart that doesn't brake nearly as well as it turns needs a more circular shaped corner entry. For the same reason a low powered car has a more circular shaped corner exit.
It's shocking the variation in execution points, amplitude and rate of control inputs, brake points, brake release and throttle application, not to mention the number one measure, SPEED at a GIVEN point there is between laps/sessions/days of the SAME (even accomplished) driver's performance...
LOL, I admit that I'm an example of this.
When people ride with me, I usually tell them "you may have noticed that I'm not very consistent; it's because I'm always trying things, to see what works best."
When people ride with me, I usually tell them "you may have noticed that I'm not very consistent; it's because I'm always trying things, to see what works best."
Hahaha! You're not the only one.
__________________ -Peter Krause www.peterkrause.net www.gofasternow.com
"Combining the Art and Science of Driving Fast!"
Specializing in Professional, Private Driver Performance Evaluation and Optimization
Consultation Available Remotely and at VIRginia International Raceway
When people ride with me, I usually tell them "you may have noticed that I'm not very consistent; it's because I'm always trying things, to see what works best."
Yeah, like you (read: I) missed that apex by 6 feet on purpose
Kinda like the old adage in music performance: if you screw up, do it again; then people will think that's how it's supposed to be
Seriously, with me it's often braking, or more specifically how little of it I can get away with....at Mosport the other day I was consistently hanging onto the brake for T2 entry a touch too long and it was costing me 1-2 mph at the bottom, which is very difficult to get back with 120hp. Yelling at myself to "relax and look ahead, s**thead" didn't really help matters much....granted, apart from technique, T2 at that track does require a certain amount of, um, bravery to get through it quickly; looking ahead shows you the first apex, then the road disappears so it's literally a leap of faith on the way down over the crest. At least it was consistent, if consistently incorrect, but it made the times I did hit it right all the better
The darker line shows a steadily increasing radius from apex to exit. The dark circle shows how the apex radius is a good bit smaller in order to use that acceleration potential during the exit. You can also see how the apex angle is later with the darker line.
I think this is an especially important and practical point. The need to have the higher-power car angled farther 'downtrack' at the apex provides a useful rule of thumb, and tends to lead to a later apex (even if the driver doesn't notice that the apex is a little later). I generally find myself paying more attention to apex angle than apex location, especially in tighter/slower corners.
I have found (with Manifold's help) places where I don't track out specifically to cut down on distance because the balance of distance traveled and speed results in a lower lap time. Summit Point turns 1-2 for example.
It may be that I can go faster through this segment though and my ability to take the short way would reduce with increasing pace.
im not sure...1-2 you track out over the white line with full throttle onto the extra pavement there (at least in lower hp cars). But can't imagine not doing that with high hp cars eigher as more steering angle would result in more power over steer.
the best illustration of scrubing speed at track out was at scca racing school in spec miata. we go through turn 9 (the right hander) and the guy had def better speed closing on me so he went on inside for the pass as we were tracking out to only scrub the speed and fall back.
I just finished Adam Brouillard's first book The Perfect Corner. His book not only agrees that different cars have different lines (mostly based on hp) but he also describes the physics regarding why. At least that was my take.
I just finished Adam Brouillard's first book The Perfect Corner. His book not only agrees that different cars have different lines (mostly based on hp) but he also describes the physics regarding why. At least that was my take.
I suggest reading all three books, multiple times. There's much to absorb there, and I wasn't able to do it in one pass. Not all of the principles are rigorously 'proven' in books (that would require some serious math), which is why I compared with what top pros are doing, and I found that Adam nailed it. I haven't found these insights in any other books - best resources I've found, and the cost is essentially zero compared to coaching, expensive schools, etc.
im not sure...1-2 you track out over the white line with full throttle onto the extra pavement there (at least in lower hp cars). But can't imagine not doing that with high hp cars eigher as more steering angle would result in more power over steer.
the best illustration of scrubing speed at track out was at scca racing school in spec miata. we go through turn 9 (the right hander) and the guy had def better speed closing on me so he went on inside for the pass as we were tracking out to only scrub the speed and fall back.
I think this is an especially important and practical point.
I generally find myself paying more attention to apex angle than apex location, especially in tighter/slower corners.
This is why I find side-by-side video comparison, compared at the SAME GPS-justified position, to be so valuable. It's an easy way to compare what it looks like out the windshield, but also includes heading and coordinates to plot the path. Pretty powerful tool.
It's all angles and geometry... I think the yaw component (rotation) is most important to establish this "downstream" attitude, but that yaw angle isn't just a turn-in aid, it can (and should) be sustained through much of the trajectory...
yep good stuff. He might not be over the white line, but first lap in the vid is where he tracks out the most...could be just a coincidence as we are splitting hairs.
08-26-2017, 02:44 PM
