CAD helps build an Ego

Many folks inclined to build their own cars go out into the garage and start bolting stuff together. Swiss automotive service firm Rinspeed had something a little more sophisticated in mind when it approached TLC Carrossiers Inc., a five-person shop in West Palm Beach, FL, with a heck of a job: design and produce a one-off roadster for the 1997 Geneva Auto Show.

Nice work if you can get it. The catch? The car had to be ready to drive in just six months. "This kind of job would typically take about a year," says TLC Carrossiers President George Balaschak. "I knew we needed engineering software on par with what the Big Three use in order to succeed on this project." TLC selected Pro/ENGINEER from Parametric Technology Corp. (PTC), Waltham, MA, at the outset of the project.

The resulting vehicle, christened the "Mono Ego," demonstrates that the creation of world-class, low-volume cars is no longer the domain of the Big Three. In just six months the Mono Ego went from a concept to a high-performance, street-legal concept-car capable of a top speed of 154 mph. And it moves with style: the 15-ft-long roadster displays graceful curves in the flavor of the Monoposto Grand Prix race cars of 50 years ago. The tricolor and angels paint scheme is by French fashion designer Jean-Charles de Castelbajac. The clear plastic driver's seat is decorated with colorful feathers.

Mechanically, the roadster's unique aluminum carapace and framework contains a vehicle that is very modern inside. Off-the-shelf components include the powerplant, drive-train, and brake system and helped make the development cost-effective. A supercharged Ford Cobra 4.6-liter, 4-valve V-8 engine provides 400 horsepower. The manual transmission is a Ford T-45. Ford also supplies the rear axle, which is from a Thunderbird/Lincoln Mark VIII. Balaschak avoided cutting down the drive shaft by moving the linkages further inboard. The custom tires are from Dunlop, feature hand-carved treads, and cost $60,000 a pair. The rear tires are different than the front, by the way, and constitute a second unique and expensive pair.

"What we have demonstrated is the ability to operate at a world-class level in the design and manufacture of concept and show cars," Balaschak says. "And we are now moving into new areas because of the capabilities that mechanical design automation tools can provide us."

In other words, CAD/CAM and advanced engineering tools are clearing the way for small shops like TLC to not only be creative, but also be efficient producers of finished designs.

Gearing up. Balaschak spent 22 years as a mechanical engineer at Pratt & Whitney, and more than a decade restoring cars and building boats, generally using the aforementioned bolting-stuff-together method. New cars, particularly unique ones, require a more methodical approach. Wanting to take that next step, Balaschak started TLC Carrossiers in 1990 with the purpose of developing and manufacturing a low-unit production car that recalled the outre coupes of the 1930s. The result was the Talbo. The aerodynamic body, chassis, coachwork, and the stainless-steel and mahogany trim were all produced in-house. TLC produces two or three Talbos per year.

The Talbo project pushed the company to seek out methodologies to support the creation of one-off and low-production cars. Balaschak used AutoCAD from Autodesk, Inc. (Sausalito, CA) to design the chassis, suspension, interior and exterior trim and other components of the Talbo. He also used it to direct the laser-cutting of certain pieces of stainless-steel trim. According to Balaschak, "doing it by the numbers" has enabled his company to enjoy the benefits of the repeatability and precision that any car company needs to survive in a tough industry.

"Maybe the Italians can get away with beating body panels into shape over tree stumps," Balaschak quips, referring to the time-honored, "hand-crafted" approach reportedly still employed by some Italian sports car companies. "But I can't."

In addition to enabling TLC to meet Rinspeed's strict time constraints, Balaschak estimates that the implementation of Pro/ENGINEER saved his client $150,000. "If the job had been proposed using traditional 2-D methods it could not have met the cost and time targets, and probably would not have been started," he says.

Tame that clay! Like many cars, the Mono Ego began life as a small clay model used to show the customer the basic styling concept. Despite all the advances in CAD and electronic styling, lots of designers still like to work out concepts in clay. "Clay has no discipline," Balaschak says. "I used to like that about it."

While this undisciplined medium gives stylists license to freely explore shapes with their hands, it has no memory. Often times, the designers decides that he or she liked a previous incarnation that, due to malleable fate, no longer exists. For this reason, Balaschak decided to go through the process of finalizing the design for engineering purposes electronically.

The initial clay representation provided a starting point for the electronic design process. Balaschak used a FaroArm digitizing arm from Faro Technologies Inc. (Orlando, FL) to input the geometry of the clay surfaces into Pro/ENGINEER. The FaroArm is a portable measuring device with a three-dimensional articulated arm that measures and captures surface features. To take a measurement the user simply touches the object to be measured with the probe at the end of the arm, and presses a button. Data can be captured as individual points or streams of points. These data are analyzed by the system's digital signal processing software and communicated by a RS-232 serial line to a wide variety of engineering software packages, including Pro/ENGINEER.

The FaroArm cares little about size limitations and TLC engineers used the same procedure to digitize critical off-the-shelf components, including the Ford engine and manual transmission, Eibach suspension, and the Hyundai headlights and taillights. Appropriately scaled, these digitized models enabled the design team to ensure all components would fit inside the underlying ribs-and-stringer assembly.

The front and rear lights posed an interesting challenge. These are important for the Mono Ego to attain street-legal status. However, the track racers the car is based on did not need lights. Balaschak did not want to spoil the look of the Mono Ego with incongruous lights, but TLC did not have the resources to develop brand new assemblies. Fortunately, Hyundai had developed head- and taillights for an as-of-yet-unnamed car that possess the appropriate "racy yet classic" lines. TLC bought a set, digitized them with the FaroArm, and designed the car to fit the lights.

Several Talbo components, including some features of the chassis, made their way into the Mono Ego. Balaschak retrieved the appropriate model files from AutoCAD and translated them into Pro/ENGINEER files where they could be turned into solids and checked for fit and interference on the new car.

Structurally, the Mono Ego has two main features: the tube-like body and the contoured fin-shapes on either side of it. "It was important to nail down the proper relationship between these aspects," Balaschak says. The parametric modeling capabilities of Pro/ENGINEER enabled the TLC team to explore thirty design iterations in just a few days. Furthermore, each iteration was available on file so designers could recall previous features that looked better on second thought.

Electronic surfaces, solid components. The placement of all components was done in parallel with the design of the body surfaces, making it possible to design for aesthetic and packaging considerations simultaneously. Using the system's surface design capabilities, TLC was able to complete iterations of the body surface in minutes, rather than the days it would have required to alter clay models. By using various lighting effects and changing the position of the car on screen, they were able to evaluate subtle changes to the surface design.

"With an electronic model of an automobile you need to see highlights and shadows and consistency of curves and clearances," Balaschak says. "The magic is in being able to move the light simulation over the product model so you can really observe, really look at your design critically. I could roll the car around on screen and say 'this looks like a kink, so I should make a change.' It worked. There were no surprises. The car looked just as we expected."

At the same time the body surface was being created, the system's interference checking capabilities and parametric nature allowed TLC to test the geometry of various components against the ribs-and-stringer assembly and body surface to find the optimal fit. "I moved the fuel tank about ten times before I found the right combination of geometry and space under the body surface," says Balaschak. "Whenever I changed one dimension the system automatically updated the geometry for related components. It saved a lot of time."

The software's product modeling and interference checking capabilities also made changes in the placement of the radiator easier. The Mono Ego inherited its radiator from the Talbo and the original AutoCAD radiator geometry was transferred into Pro/ENGINEER so it could be checked for interference with other surrounding components. "I knew what radiator I wanted to use and I already had the surface skins and the chassis in the product model," says Balaschak. "So, I floated the radiator until I found the right placement. Then, with the radiator in place, I was able to model the brackets that would complete the part interface."

With the individual components of the ribs-and-stringer assembly in an electronic format, TLC was able to rapidly cut the parts and get the Mono Ego on the road. Balaschak wrote the finalized design files to disk on a Friday afternoon. He took the disks down the street to Westgate Sheet Metal, where laser-cutting of the ribs and stingers began almost immediately. The components were cut and polished by Saturday. Assembly was completed by the following Tuesday. And Balaschak was driving the Mono Ego for promotional videos that Friday.

Ready for their next project, TLC is already involved in plans to build another show car that will bring the Alfa Romeo 8C 2900 into the 21st century. All he needs is a customer with enough money to buy one. Beyond that, Balaschak visualizes the TLC of the future as a producer of personalized low-volume cars that are competitively priced for the consumer market. "I see it as an interesting engineering and business challenge," he says. "It is going to require advanced engineering modeling to get it done and excellent presentation models to sell the idea."