Formula One Engineers Use SL

It is estimated that 80 percent of an F1's performance can be directly traced to the car's aerodynamics. So, it really comes as no surprise when we see teams investing large sums of money for the latest technology in order to maximize their car's performance. No expense can be spared in creating the best possible combination of horsepower and handling to help bring the driver home to the winner's circle. But how do they do it?

The entire F1 design process is a very strenuous one involving upwards of 4,000 individual parts. The design work can take between 14 to 16 weeks to complete. There is very little in the way of carrying over parts from one year to the next because of the constant state of design change, so parts are rarely ever used more than once.

Teams conduct "a to z" safety and reliability tests so that the results can be engineered and built into the car the next time it runs. In the 1960s, one accident in eight in F1 events resulted in a fatality or serious injury. Since that time safety has become standard practice. F1 teams conduct on average about 125 tests on their cars and, since time compression is part of the job, engineers appreciate the interval between getting design faults recognized and quickly correcting them. That sometimes means designing something in a matter of days and sometimes even hours, as well as producing the parts.

F1 engineers are constantly improving their machine, making changes to its aerodynamics, its suspension and all of the design that is involved in those separate projects. They also may change jigs and fixtures for R&D development work to apply to future cars. Designers and engineers follow four main rules to F1 perfection:

1. Making changes to parts on the car, including the chassis and the engine.
2. Changing the geometry for improved car performance.
3. Saving weight by changing the car's distribution.
4. Improving the F1's performance through constant wind tunnel testing.

Many engineers find the majority of an F1's performance linked to its aerodynamics, which makes it critical to focus a lot of effort in that area.

Team engineers are constantly looking at subtle variance changes, which are tested until a better F1 assembly is found. When that has been done, it is passed over to full-size car model development. Engineers go through full-size exercises to make sure that the F1 is as structurally sound as possible.

Achieving Precision and Accuracy

The materials employed are very high-tech and several have their roots in the aeronautics field. The car's GBox case is constructed in magnesium; Tungsten is used to strengthen the chassis and give ballast as well as help move the car's center of gravity; a wide variety of carbon fiber-based composites can be found in the car's suspension and brakes and Kevlar is used in the driver's compartment. But nothing gets made without first having it defined in CAD.

"We have 40 CAD stations working around the clock on every one of the F1's features. Everything is built around our technical database. We have engineers working on finite element calculations for fluid mix as well as for structural definitions. From the first CAD file to when we finally run the car, it's about a three-month process," says Ditier Perrin, CAD design engineer for Prost.

With Prost's new F1, the APO3, one of the main problems overcome during the design phase was that of managing the APO3 CAD files on the computer. Prost had three different groups working in three different places on the same car. They had to exchange files in real-time, meaning that changes made in Paris had to be immediately available to engineers working in England. The car's configuration had to be compatible with what other members of the team were doing.

"We have to define everything together," says Perrin. "We can't follow a normal routine like R&D, or process, production or testing. We need quick response time and since Catia is used so extensively by our subcontractors here in Europe, this is possible."

In addition to CAD, F1 teams are increasingly employing a wide range of RP techniques as developmental tools - such as stereolithography (SL) - to decrease machining time and material wastage. Accurate SL components feature highly refined surface finishes and serve as design concept models - from prototypes for forms, fit and functional testing or as master patterns for molds, castings and other tooling applications. They can be finished with paintwork to racing standard, so that the finalized wind tunnel test model provides an accurate scaled representation of the real F1 car.

Tunnel to Success

While testing the machine, it became apparent to engineers that it also could be used for its F1 wind tunnel testing. The best way to exploit wind tunnel testing and create a top-notch competitive car is to reproduce the highest number of experiments. With 3D's SLA system, Benetton now produces a higher number of parts and is working with its $30 million wind tunnel more often - tripling the time spent on tests from eight to 24 hours a day. Benetton increased the tests because by not using the wind tunnel to its fullest meant lost time on both design and component parts tests.

"When the tunnel wasn't in use it cost Benetton precious time because it meant that no component parts were being tested, and components are key to an F1's success," says Luca Mazzucco, marketing manager for Benetton. "There are mechanical as well as aerodynamic aspects to a car, with 90 percent of our parts designed and built in-house. The smallest problems can ruin the best F1 in a matter of seconds and weakness can translate into failure, so you have to push every detail. Aerodynamics is much different in F1 than aerospace because since the car has four wheels, you can't really call it an aerodynamic object because you would never put these things on the sides of an aircraft."

The reason SL has caught on is that F1 engineers can run small pressure tappings with three-port geometry and literally follow the shape of the car chassis to look for defects. These pressure tappings are very hard to produce conventionally because the engineers have to run little metal tubes, which they have to bend, and then bed into the car's skin. Benetton engineers can now build those directly into the STL file and the SLA, which allows them to do far more pressure tappings than they ever could before. They also can put them in locations that were inaccessible just a few short years ago.

"We are doing a lot of work with F1 radiators right now," says John Murray, F1 specialist with 3D Systems. "We run the pressure tappings right through the top of the radiator, then down the spine so we can record static and dynamic pressure taps, which could not be done before."

The SL pressure tapping has enabled Benetton and other race teams to rearrange the F1's rear wing, which can have up to six different elements built into it and must be tested out to be rigid. What engineers do is machine on an aluminum core then stick little SL pieces that have little pressure tappings on them. Engineers put them on one skin, run a test, pull them off and put them on the next skin until they map the entire surface geometry work - without doing any machining or tooling.

A case in point, this system recently saved Benetton a lot of time and money when it succeeded in picking up a faulty steering rack assembly. The engineers realized in test drives that the hydraulic line interfered with the car's rack and pinion and quickly scrapped the design. This saved a lot of machining and complex tooling hours for the team. Form, fit and function are the watchwords F1 teams live by in their world because there are only two ways to go faster with an F1 - that's with more power and better aerodynamics.

"Our goal someday is to place SL parts directly into the car," says Mazzuco. "Benetton could only test two wings in its tunnel, but because of SL Benetton is now able to look at up 15 to 18 wing parts. Benetton can make changes more quickly and our engineers have a lot more latitude on how quickly they test their designs. But you have to remember that, like most things, the more one uses a device the more effective the payback."