This Sunday, May 29th, will be the 106th running of the Indy 500. So, we thought we would apply the Science of Driving to the Indy 500 and do a simple analysis of the track and the drivers. Hopefully, it will make watching the race more enjoyable.
Listen to the Podcast
Applying the Science of Driving to the Indy 500.
We will start off by taking a look at track dimensions.
The Indy track is 2.5 Miles or 4 Kilometers in length.
The track consists of:
- Two long straights that are each 3,300 Feet or 1005.8 Meters in length
- Two short straights that are 660 Feet or 20.2 Meters long
- Four corners that are 1320 Feet long or 402.3 Meters
Looking at those numbers, an Indy driver will spend 40% of their time in a turn.
Some Numbers
Over the last decade, during the race, the average straightaway speeds are approximately 225 MPH or 362 KPH. This year, during qualifying runs, some of the drivers reached 240 MPH or 386.2 KPH on the long straightaways, which is very impressive. When looking at the average speed for the entire race, is lower than the 225 MPH or 362 KPH due to pit stops.
For the podcast episode and for the sake of easy math, we will lower that max speed number to a boring 220 MPH or 354 KPH, which is 323.4 feet in a second or 98 Meters Per Second, more than the length of a US football field in a second. When you consider that blinking your eyes takes .2 seconds, the vehicle and the driver will travel 64.6 Feet or 19.6 Meters in a blink of an eye. At 220 MPH 354 KPH, it would take the vehicle 10.2 seconds to go the length of the long straight, 2.04 seconds to travel the short straight, and 4.1 seconds in each corner.
Pit Stops
Throughout the history of the Indy 500, the winner has often been decided by what happens off the track and during pit stops. So, how vital are pit stops? If the average speed is 220 MPH or 354 KPH for every second spent in the pit, the driver will give up 323.4 Feet or 98 Meters of track space. If the pit stop takes five seconds, they give up half a straightaway of distance. This means that if two drivers enter the pit simultaneously, and one leaves the pit a half-second quicker, that driver gains 162 feet or 49 Meters of distance on the other. Looking at those numbers, you can understand why the teams spend a great deal of time practicing pit stops.
When watching the race, you can also understand why the TV crew spends considerable time broadcasting and explaining what is happening during pit stops.
Corners
Depending on the vehicle’s path and speed, the cars will produce approximately 3.8 G’s pushing on their Center of Gravity. That means there is 3.8 times the vehicle’s weight pushing the vehicle away from the corner and towards the wall. Also, four times a lap, there is 3.8 times the weight of the driver pushing on the driver. If a driver weighs 175 Pounds, 79 Kilograms, there will be 665 pounds or 301 Kilograms pushing on their neck four times a lap.
An Explanation
Every time they drive through a corner, the path of the vehicle creates an arc with a given radius. The arc is created by the amount the driver moves the steering wheel. You will hear the announcer call the arc – “the line the driver is taking through the corner.” The driver’s speed, where, and how much they move the steering wheel will determine “their line,” which determines if they make it through the corner, spin the vehicle, hit the wall, or both. The driver will make the decision of where and when to move the steering wheel and at what speed 800 times (200 laps).
Even at Indy, it is all about the driver’s equation.
Old Scotti School and in the present VDI students are familiar with the phrase “The Drivers Equation.” Even at Indy, it’s all about the Drivers Equation. The less the driver moves the steering wheel, the bigger the radius – the bigger the radius, the faster the driver can move through the four Indy corners. The faster the driver moves through the corner, the higher the force pushing on the race car’s center of gravity. With too much force, the driver will lose control – too little, they are not maximizing the vehicle’s capability and will lose track position.
There are some differences between the student and the Indy car driver working the Drivers Equation. Depending on the exercise, the student is moving 40 to 60 MPH or 64 to 96 KPH and the Indy Driver is moving 225 MPH or 362 KPH. Also, if the students mess up the driver’s equation, they hit a cone. -If the Indy driver makes a mistake calculating the driver equation, they hit a wall at around 200 MPH. On the other side, if the Indy driver manages the driver’s equations better than the other drivers and combines that with great pit stops, they take home around two million dollars- if the student does a good job of using the equation, they get a Certificate.
Push and Loose
You will hear the race commentators talk about “Push” and “Loose,” which refers to Understeer and Oversteer.
Understeer (the “push”) is the condition where the front tires lose adhesion while the rear tires remain in contact with the pavement. The car tends to travel straight ahead, even though the driver is turning the wheel; too much understeer results in hitting the wall.
Oversteer (the “loose”) is the condition where the rear tires lose adhesion while the front tires remain in contact with the pavement. The car’s back end will slide out; actually, snap out is a better explanation.
The Laws of Physics
To get a clear understanding of understeer and oversteer, a basic discussion of the laws of physics is required. When the driver turns the steering wheel, there is energy pushing on the race car’s Center of Gravity (CG). The amount of energy (it can be measured in G’s or pounds or kilograms) is determined by how much the driver moves the steering wheel and how fast they are traveling. The more speed and the more steering, the more energy is pushing on the vehicle. Remember from high school, “for every action; there is an opposite and equal reaction.” So if there is a force pushing on the CG of the race car, there has to be an equal and opposite force pushing back – that force pushing back is created by the friction the tires make with the track.
Forces on the Indy Race Car
The average Indy car weighs 1600 Pounds or 725 Kilograms. If the Indy car is driven around a corner that creates 1600 Pounds or 725 Kilograms pushing on the CG of the vehicle, that would be 1G pushing on the CG of the vehicle. The tires would be pushing back 800 pounds or 363 Kilograms front and rear. In the perfect world, this would be called neutral steering.
As I mentioned the Indy Car can produce up to 3.8 G’s. At 3.8G’s there would be 6080 Lbs. or 2759 Kilograms pushing on the car’s center of gravity.
Which would mean that both the front tires and rear tires would have to push back with 3040Lbs or 1379 Kilograms to keep the car balanced.
Oversteer and Understeer Through the Corners
You will also hear the announcers talk about the vehicle changing from understeer to oversteer, or vice versa, as the car is moving through the corner. The driver will be in the 1320-Foot turn or 399 Meters for about 4 seconds and at the rate of 220 MPH or 354 KPH, which is 323.4 Feet or 98 Meters in a Second, all while the rear tires are breaking loose (oversteer) or the front tires are losing adhesion (understeer). If the vehicle oversteers, the rear of the vehicle will more than likely hit the wall. If the vehicle understeers, it is likely the front of the car hits the wall.
With oversteer, a small movement of the steering creates a big movement in the rear of the race car. With understeer, the driver moves the steering wheel, and the vehicle is not turning and at 220 MPH or 354 KPH heads toward the wall.
A phrase often heard in the old Scotti School, and present VDI training programs is that small changes in speed produce big and dramatic changes in the vehicle’s behavior.
As the driver moves through the corner a small change in throttle position or steering wheel angle can produce devasting results. A change of 10% in speed produces close to a 20% change in the force pushing on the vehicle’s center of gravity. All this happening at 220 MPH or 354 KPH – that’s why drivers need to be the best of the best.
With the advent of cameras in the vehicle, you can look at the driver’s hands; there should be one steering wheel movement when entering the turn. If their hands are moving while in the corner, they are trying to balance the car, and nothing good will happen.
Chasing the Balance
You may hear the announcer say the driver is chasing the balance – what that means – is with their hands – (the steering wheel) and their foot (the gas pedal) – they are controlling the amount of force pushing on the race car’s center of gravity and the force pushing back. With too much force, they can lose control; too little, and they are giving up speed and track position.
From a driving standpoint, what is hard to do and considered by many to be a dangerous characteristic, is a vehicle that goes quickly from understeer to oversteer, or vice versa. You hear it often when watching an Indy event; they will say that the car was a push (understeer) entering the corner and loose (oversteer) coming out. This condition is one of the very few that will cause an Indy driver to slow down.
Driving an Indy Car through a Slalom Course
For those who have attended a Scotti School in the past or a VDI program in the present, a good reference point would be the slalom course. Those former students are all familiar with the 80% requirement. The 80% requirement that others claim as there’s or as an international standard is not accurate. Interested in where the origin of the 80% standard was actually derived? So what would the numbers be if you were to drive an Indy car through the slalom? What numbers would you need to reach the 80% requirement?
Using 100% of the 3.8 G’s of the Indy car’s capability would produce a speed of 83 MPH or 134 KPH. To achieve the 80% goals, you need to drive through Scotti School/VDI slalom at 74 MPH or 119 KPH. Also, consider that at 74 MPH or 119KPH, you would be moving 109 Feet Per Second or 34 Meters Per Second. You would have about .6 seconds from cone to cone.
The difference between using 100% and 80% is 23MPH/ 34Feet Per Second or 37 KPH/10Meters Per Second.
Those who have achieved 80% in the slalom know the skill level required to accomplish that.
We hope understanding some of the science behind the Indy 500 makes watching the race more enjoyable.
Just a Reminder
Have a great weekend. Just a reminder, it is memorial day on Monday in the United States. It is not a day of celebration, but one of remembrance to honor those US servicemen and women who have died serving our country – protecting our nation and freedoms.
Join the Association
If you have an interest in going much deeper into the Science of Driving, I invite you to check out the International Security Driver Association’s website and consider joining the only organization dedicated to supporting the advancement of professional Security Drivers and other protection practitioners with data-driven research and other professional development tools.
For more information on all of the member benefits, head over to https://isdacenter.org.