Driving epiphanies

(Jamie Gonzalez) #42


Any possibility to get that a few corners or a corner like that broken down in more screen shots from entrance, mid corner , and exit track out. That actually really helpful to see it broken down like that as like dom I struggle to wrap my head around the driving style without over or under driving the corner entry stage.

(Dom Callan) #43

Thanks. Will give it a go.

(TJ Koyen) #44

For sure. Here’s a break down of some of Ocala’s corners. I chose Ocala because it has a good mix of fast and slow stuff. Picture heavy post incoming…

This is turn 3, the first corner you have to brake for. It’s a slow-medium speed left that you enter while slightly curving to the right, so setup is difficult for turn-in.

  • initiate turn-in and load kart

  • by apex, we have the wheel back to straight(ish), as we feel the inside rear wheel reach maximum unload, where the chassis has reached it’s max loading ability. Countersteering slightly here because it was Friday so grip levels weren’t quite up yet.

  • wheel is straight by exit

  • setting up for turn 4, which is a slow-speed left hairpin. I think it’s important to note how I haven’t even started braking yet and I’ve already spotted my apex point. Always be thinking/looking two steps ahead.

  • initiate turn-in, look how little wheel input you need to make a hairpin corner…

  • wheel is straight(ish) again at apex. I’m about a foot off the ideal line here, so I picked up a touch of oversteer. If I had gotten down to the curb more, the kart wouldn’t have needed that countersteer.

  • turn 4 is another right hand hairpin, but since we are entering from the other side and having to come back across the track to set up, the wheel input to turn-in is a little more than the previous corner.

  • by inducing more wheel input right off the bat, I can straighten the wheel sooner, as the kart is loaded more quickly. For this particular string of corners, this is necessary, however loading the kart quickly like this is going to set the inside rear wheel down sooner and limit how well I can rotate off the corner. In an ideal world, I would ease the kart into the corner more progressively, but our entry was compromised by having to come back across the track from the previous corner to set up for this one.

  • this corner is a bit longer than the previous hairpin, and the next corner is a fast left, so I have to keep a little wheel in from apex to exit because I need to keep the kart down on exit so I can set up for the next corner. I’m compromising my exit here to optimize the entry to the next corner.

  • the final corner at Ocala is a long, fast 180 left. You need very little steering input to get the kart to rotate here. This corner is similar to turn 3 in that they are both 180s, but since this corner is much longer and stretched out compared to turn 3, all inputs are slowed down. In fast corners like this, I try and coach to “drive with your shoulders”. You’re barely even turning the wheel with your arms, it’s more of you “leaning” the kart into the corner with your upper body.

  • on a big corner like this it can be a bit like driving a sprint car on dirt when grip is low. I’m constantly having to make adjustments through the long apex here, so you can see little instances of countersteering and corrections all through the corner. You’re asking the kart to hold an even line at a high rate of speed, so lots of Gs are going through the frame, making any little imperfection in the racing surface amplified, upsetting the kart with every tiny bump. With more rubber down later in the weekend, this became less slide-y.

  • I’ve got the kart settled back down and tracking with no sliding off the corner. Wheel is totally straight and I’m letting the load of the chassis carry me off the corner.

I hope that gives some more insight. It actually helped me break things down for my own knowledge a lot more as well. Watching the video in .25 speed and studying specific parts really helped me understand why I did some of the things I did.

(Nik Goodfellow) #45

In my opinion one of the failures of nostalgia is that we look back thinking that was the best way to do things. Sure Pantano looked great and he won stuff. But watch this video, you have some karting greats on their Trulli, Fisichella, Beggio (number 3), Manetti (early leader). I don’t think I saw Trulli back it into a corner once, I think I saw Fisi do it while overtaking and they dominate (no surprise they got to F1). The guys backing it into corners just drop further and further back. In fact for most of the race Trulli doesn’t even look like he’s trying, to me that is the sign of a great karter.

So while it was possible (and still is in some conditions) its almost never the fastest way. Its usually to warm up the tires (in the early laps), make up for a poor handing chassis, or to make an aggressive overtake.

(Dom Callan) #46

Taking us back down a different road…

Going back to the idea of 4 specific friction circles (one for each tire)…

You seem to start with a moment of trying to load the outside front tire.

First of all: Why? Assuming we are approaching a turn, we are braking in a straight line… it seems to me that the front tires inside and out will load up under braking equally.

There is a the bit that makes me think I am missing something here. There is the chapter in Terences book where he puts forth an idea I don’t understand about pre-turning. It was sort of like advocating coming down the straight a bit off the edge of the track and right before turn in, skootching the kart over to the edge of the track before turning in the opposite direction.

I suspect what he’s talking about and what you are talking about are similar if not the same.

But, I don’t get it. When I brake, the weight goes forwards. If I am turning while braking, then yes there will be more weight on the outside of the kart and therefore the front outside contact patch. But what if I am straight line braking?

If I am getting this correctly the front end is loaded up, kart rotates a bit from turn to apex, and then when you put in the throttle, the inside rear comes down stopping your rotation and off you go in as straight a line as possible.

I just can’t wrap my head around the outside front loading.

(TJ Koyen) #47

I almost always trail-brake, so I drag a little brake into the turn-in part. So this is more for me personally. However, if you’re straight-line braking, you are able to get to the throttle sooner. So you will still be loading the outside front because as soon as you finish braking, you should basically be starting to apply throttle. Turn-in + throttle application = both outside tires loaded.

One thing I would like to stress is that we are doing a ton of talking and thinking here, and it’s good to understand and learn what’s actually happening when we are driving fast, but there is almost no way any human could possibly run through this entire process in their head when approaching a corner. What I try and do when coaching is to always keep the driver…
A. On the correct line
B. Using all the grip available to them

Doing both those things comprises like 90% of going fast. Using and transitioning all the traction you have from braking to turning to accelerating as fast as possible without upsetting the kart.

(Warren Chamberlain) #48

Dom, a tire will not produce grip without load, and it will not produce optimum grip unless it is given optimum load. When braking, cornering and accelerating, loads build and dissipate over time, and it is the driver’s job to manage this process to extract optimum performance. The energy cycle is one way to think about this energy/load/traction/force relationship or process.

Another key element to managing the energy cycle is how you manage your sensitivity to the energy, loads, traction, and forces you are creating and experiencing. The easiest way to increase the depth or resolution of you sensitivity is to reduce the scope. So, yes the performance of each tire can be described as a friction circle (or a 3D friction circle), but why bother trying to manage that much information?

If you’re at the turn in point for a right-hand turn, your left-front tire is going to determine whether or not you stay on the track. So, for me, I don’t give a damn about the other tires; I invest my attention on the tire that’s carrying (or that very soon will be carrying) the critical load and producing the critical traction. This scope reduction allows me to manage the ‘critical’ tire’s performance with maximum precision and clarity.

In the same light, while you are correct that when braking in a straight line both front tires receive weight (or load), there is no need to pay attention to both of them; especially since most karts don’t have front brakes. The more important task is determining (with as high a resolution as you can) if your braking has transferred the correct amount of load to allow that tire to:

  1. Initiate the turn
  2. Build loads to produce optimum traction
  3. Create forces will cause the kart to rotate at a pre-determined point in the turn
  4. Dissipate the energy back into the chassis in an orderly way so it can be distributed to the outside rear tire

When you’re done with the above, then your attention should shift to the outside rear tire. Yes, both tires will be on the track driving you out of the turn, but the outside rear is the only tire that requires critically precise management to maintain optimum load/traction.

Of course, the above is a generalization. For tuning or troubleshooting it may be important to invest some intention on ‘non-critical’ contact patches, but when I drive 95-99% of the time, I am managing one tire at a time.

I’m not trying to speak for Terence, but If you think of speed as a liquid, then looking down on the kart, if you made that small juke towards the left edge of the track, you initiate a small wave of energy rotating to the left, the ‘wave’ would not have much energy, and the steering input would not last long, so the ‘wave’ would quickly stop and begins flowing (rotating) back to the right (in search of equilibrium). However, just as the wave is about to reach equilibrium, you would steer right, into the turn. The energy from the initial energy ‘wave’ gets added to the new right-hand rotation wave caused by the turn in. Because of that, the elevated rotational energy rotates the kart very quickly into the turn. The first few seconds of the “My passion for karting…” YouTube link above shows this very clearly.

(Dom Callan) #49

Thanks both. I will try to absorb this not too ambitiously, but enough that it starts me down the path of trying to be more aware of what’s going on and how it feels.

(Warren Chamberlain) #50

Lee, thanks for posting the article!

So, I read the whole article, and it was interesting, and scientific, and had cool pictures, but I can’t help thinking I didn’t really learn anything that I hadn’t learned in Alan Johnson’s 1972 book _Driving in Competition.

I was also surprised that rotation (yaw) was only mentioned once, and that was just a passing mention. I’m not a scientist, but in my opinion, if a car/kart is being driven at the limit of the tires, then ‘K’ numbers are only part of the story… they should also be measuring ‘Ya’ and 'Yr" (yaw angle and yaw rate of change) around the tightest radius of the ‘line’ in each corner to really get a full understanding of the ‘line’… but then again, who the hell am I. :grinning:

Anyway, if you buy the idea that the rotation point is when you can start accelerating out of the turn, then Fig 5 is a perfect example of the difference between a driver who lets the car decide when it will rotate (driver B) and Stewart who is a driver that dictates when (and how) the car will rotate in order to meet a specific driving objective (maximum speed down the next straight in that case).

Since they mentioned Nigel Mansell in the article, I found it interesting that he does something completely wrong according to the ‘champions’ they have tested. Paraphrased from his autobiography…

I tend to take a different line around corners than other drivers. The classic approach is slow into the corner and fast out of it. My style is to brake hard and late and turn in very early to the apex of the corner, carrying a lot of speed with me. I then slow the car down again in the corner and drive out of it.

(Dom Callan) #51

This is super helpful btw in context of Kartkraft. I noticed this last night actually. Given how tightly wound the steering is, I had to take hands out of the equation. I was literally driving with my shoulder muscles as dominant, to the point that it hurt. Specifically upper back shoulders.