This will be the 103rd running of the Indy 500, so we thought we would do a simple analysis of the track and the drivers; hopefully, it will make watching the race more enjoyable. My guess is that Vehicle Dynamics Institute graduates and International Security Driver Association (ISDA) certified drivers will be familiar with the numbers.
The Indy track is 2.5 miles in length.
The track consists of:
two long straights that are each 3,300 feet in length
two short straights that are 660 feet long
four corners are 1320 feet long
Looking at those numbers, an Indy driver will spend 40% of their time in a turn.
Over the last decade, the straightaway speeds are approximately 225 MPH, due to pit stops the average speed of the 500 is much less. For the sake of easy math, we will lower that max speed number to a boring 220 MPH, which is 323.4 feet in a second, more than the length of a football field in a second. Blinking your eyes takes .2 seconds, the vehicle will travel 64.6 feet in a blink of an eye. At 220 MPH it would take the vehicle 10.2 seconds to go the length of the long straight, and 2.04 seconds to travel the short straight, and 4.1 seconds in each corner.
How vital are pit stops? For every second spent in the pits, the driver will give up 323.4 feet of track space. In five seconds, they give up half a straight way.
Depending on the vehicle’s path and speed the cars will produce 3.5 G’s pushing on their Center of Gravity. That means there is 3.5 times the weight of the vehicle pushing the vehicle away from the corner and towards the wall. Also, four times a lap, there is 3.5 times the weight of the driver pushing on the driver. If a driver weighs 175 pounds, there will be 612.5 pounds pushing on their neck four times a lap.
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, or hit the wall or both. During the race, a driver will make these decisions 800 times (200 laps).
Under and Oversteer-Understanding the Basics
Throughout the race, you will hear the announcers mention the car is pushing, or it is loose. That is “announcer speak” for under or oversteer.
Under and Over Steer are used to explain vehicle characteristics.
Understeer (the Announcer guys call this “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 at Indy understeer results in hitting the wall.
Oversteer (Announcer guys call this “loose”) — is the condition where the rear tires lose adhesion, while the front tires remain in contact with the pavement. The back end of the car will slide out, actually snap out, is a better explanation.
You will also hear the announcers talk about the vehicle changing from under to oversteer, or vice versa, as the car is moving through the corner. As mentioned above the driver will be in the 1320-foot turn for about 4 seconds, and moving about 160 feet in a half of a second, and could be dealing with a car changing from understeer to understeer, and that can create some exciting driving.
Enjoy the race!
This post is authored by International Security Driver Association Member
The International Security Driver Association (ISDA) serves the Protective Services community. ISDA’s mission is to support an international forum of protective service providers who share knowledge for the purpose of enhancing the profession.
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