The Engineering of IndyCar Racing
- Sunday, 01 July 2012
Cowdin: It depends on the configuration of the track. On road courses, the driver can change the brake bias, which is front-to-rear brake distribution, and often the actual roll bars front and rear, which change the mechanical lateral load distribution of the car. On the ovals, we’ll add what’s called a weight jacker, which is basically a hydraulic slave cylinder located in the right rear spring that will either raise or lower the car as it pertains to that spring. It changes the weight distribution across the two front tires, which will affect the handling of the car as it enters the corner.
NTB: The steering wheel on a modern IndyCar is actually a mini data center. What types of information does it give the driver, and how do you make it available to the driver in real time?
Cowdin: Some of the information we give the driver is quite basic — the number of laps completed in a race, engine RPMs, speed — but the dash is limited by the number of LED displays. We have four different pages for four different layouts so the driver can configure it to his or her own liking. For races, we provide fuel count, fuel used, and basic information on anything that’s on the car that the driver would need information about, such as tire pressures or temperatures.
NTB: This year saw the introduction of a completely new type of IndyCar and new rules that allow the teams to use different body work and aerodynamics packages. This had to involve a lot of wind tunnel testing and computer simulation. How close did the computer data come to what you actually learned in the wind tunnel?
Cowdin: Well, a lot of the accuracy of our simulations revolves around tire modeling, and getting a very good tire model is a difficult thing to apply into a simulation program. Firestone’s a great partner for us, and they supply us with a very good tire model that we use for our simulations. But part of what we had to adjust for in simulation is track conditions for the grip coefficients for each individual circuit. Those are always a floating target throughout the race weekend. It depends on temperature and the number of laps done on the circuit.
From a wind tunnel standpoint, we had quite a steep learning curve with this new car, and we’ve been using every resource available. Our team is closely associated with Chevy racing, so we get a lot of support from them and their engineering firms. We’ve done everything from computational fluid dynamics (CFD) and 50% model scale testing, to full-scale rolling road testing of the car, so when we go to the race track, we’re pretty confident in the package we’ve put together.
NTB: Is there much, if any, redundancy built into the electronic circuits on a modern IndyCar?
Cowdin: Due to weight restrictions for performance, the only redundancy on the car is the safety equipment. We have an accident data recorder that has builtin backup power, which allows us to keep recording if the car loses power. The voice radio and fire suppression system have their own independent power sources — just batteries. And there is also a master switch that can be manually triggered by safety workers so that after an accident, it turns all the power off and triggers the fire suppression system.
NTB: With all the sensor systems and computer data available to a team today, how critical is the driver’s input?
Cowdin: I think I touched on that when we reviewed our simulation work pre-event. If that were 100% transferable to the track, then we would just show up and race with the drivers driving the optimum car. But each driver has their own preference on how they drive the car and the areas of the circuit where they’re going to maximize their performance based on that style. So we give them the best combination of a mechanical and aero package through all of the work we can do before we arrive, but there’s nothing that replaces a driver’s feedback and helping the driver get the best out of a mechanical package on the track.
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