All-Digital Process
Speeds Development of F1 Car

Prior to the start of the 1998 season, the FIA (Federation Internationale de l'Automobile) announced it would require several significant technical changes to Formula One cars. Aimed at putting a brake on the ever-increasing speeds of these cars and enhancing driver safety, the changes included reducing the maximum permissible width of a car from 2000mm to 1800mm, using grooved tires during dry-weather races, and setting new side-impact standards. With the exception of the new tire requirement, these regulations had a significant effect on chassis design. Engineering crews burned the midnight oil last winter to bring 1998 vehicles into compliance.

The Tyrrell Racing Organization, an "establishment" name in Grand Prix racing, had another significant technical issue to deal with as well. The team was changing from a Ford ED V8 engine, which had powered the 1997 025 car, to the newer Ford ZETEC-R V10. Its response was to design an all-new car for the 1998 season, the Tyrrell-Ford 026.

"The combination of the Ford V10 engine and the demands of the new regulations required a totally new car," explains Dr. Harvey Postlethwaite, managing director/technical director at Tyrrell. "That is a lot to accomplish in six to eight months, but with our 1997 car being modeled completely in the computer, the changeover was fairly seamless."

Since 1996, the Tyrrell team has used automated product-modeling software tools from Parametric Technology Corp., Waltham, MA, in the design and manufacture of its racecars. Its 1997 car was the first to be modeled entirely in Pro/ENGINEER. Because of the ease with which changes could be made to parametric models of that vehicle, the design of the 026 went quickly. "We're a little team," says Postlethwaite, "but we were one of the first teams to have the new, narrower version of the chassis completed."

Chassis Performance

A reduction in chassis width of 200mm may not sound like much, but it was -- from both a performance and a design standpoint. The reduction was designed to slow cornering speed, but this approach to slowing the cars did not meet with Postlethwaite's approval. "If you start by agreeing with the premise that the speeds of Formula One cars need to be reduced," he says, "the question which follows is, 'how do you accomplish that?' Personally, I feel it is highly regrettable that the way chosen in recent years has been to whittle away continually at chassis performance."

That did not exempt Tyrrell from complying, of course. In terms of performance, the width reduction actually resulted in a more efficient car in terms of lift-to-drag ratio. With the wheels and tires moved closer to the bodywork, the airflow around the car was altered in a way that boosted aerodynamic efficiency, which Tyrrell determined from wind tunnel tests. However, the width reduction posed other engineering problems, such as how to package everything that was already packed as tightly as possible in the previous year's wider vehicle into the narrower space.

"Every year it is more difficult to fit everything into the car, with the growth in the complexity of the engine, the attention to detail in the aerodynamics, and proliferation of electronic 'black boxes,'" explains Postlethwaite. "This year could have been even worse. But having the entire car, including the engine and the driver, modeled in Pro/ENGINEER helped greatly. We could move components around until we had the best package possible."

The new, more stringent side-impact regulation affected the design of the 026 as well, requiring a more energy-absorbent chassis and longer side-pods. Postlethwaite had no quarrel with this regulation. "Effectively, we were asked to move the crash structure forward," he comments, "which could lead to the cars looking a bit ''slab-sided.' But in general terms, any positive changes as far as driver safety is concerned are correct."

The new regulation required the dissipation of double the energy input to what was previously one of the weakest parts of the Formula One chassis. As with the packaging of the car, the ability to move virtual components around on-screen was important in meeting this regulation. Tyrrell engineers went through many design iterations to produce an aesthetically pleasing racecar that also complied with the regulation.

While the ability to make fast revisions to the car's geometry saved time compared to earlier manual practices, any "extra" time was used to fine-tune the 026's performance in software. By the time the first car was built, Postlethwaite and his crew had optimized crucial performance aspects such as the stiffness of the monocoque structure using PTC's functional simulation software, Pro/MECHANICA. "That is the true value of these software tools to us," Postlethwaite explains. "Any time they saved was used to go through more iterations to optimize the car as much as possible before we built it."

Simulation Optimizes Stiffness

A key factor in a Formula One car is wheel-to-wheel or torsional stiffness. High torsional stiffness means that when one wheel goes over a curb, the structure of the car doesn't twist. Rather, the whole structure lifts into the air. The reason for having high torsional stiffness is that the chassis needs to respond to adjustments. Adjustments can be far finer and more significant if the torsional stiffness of the whole structure is very high.

Like electrical resistance, total torsional stiffness is the sum of the reciprocal of the stiffness of the individual components, so every component needs to have a very high individual stiffness. "It is no good to design a torsionally stiff monocoque if the suspension is mounted poorly or the gearbox is weak," Postlethwaite explains.

During the design process for the 026, engineers simulated each component along the chain of the monocoque in Pro/MECHANICA, to ensure that its contribution to the torsional stiffness was as high as possible. After using the software to apply a known load to the component, engineers viewed the Pro/MECHANICA results that illustrated deflection. Any part that showed more than a certain amount of deflection was sent back for a redesign. More material was added, or a different material with a higher modulus of elasticity was used. As a result of this process, the team didn't have to worry about torsional stiffness in the first car they built; that issue had already been resolved in software. "You can't predict a lap time in Pro/MECHANICA," says Postlethwaite. "But if your analysis model is correct, what you see on the computer is what you get on the road, and our experiences bear that out."

Incidentally, one of the side issues of narrower suspension was that the monocoque deflected less than in previous years because the wheels were closer to the main part of the structure. The Tyrrell team anticipated this, but was able to model it quickly in Pro/MECHANICA and quickly understood what role it would play in overall torsional stiffness.

Pro/MECHANICA was also used to simulate the performance on many other parts of the car. It was used on camber plates, for example, to find a balance between weight and strength for these critical parts. Camber plates are used to change the camber--the angle of the front wheels--to optimize the car for a particular course. They bear a great deal of load, including shock loads when a wheel hits a bump, as well as the entire steering load. Tyrrell had a camber plate crack in the past. Using Pro/MECHANICA, engineers saw an area of high stress on the earlier camber plate model right where it had cracked on the actual car. They used that analysis model to evaluate new camber plate designs until they had one with suitable stresses in the critical area.

Going one step further, the team evaluated ways to maintain suitable stress levels while testing methods to reduce the weight of the camber plate. Pockets are often milled into the aluminum plates to reduce weight, so engineers simulated loads on camber plates with milled out areas. They went through dozens of revisions until they found a design that had the least amount of weight possible yet still tolerated the required loads.

No Drawings

Like most Formula One teams, Tyrrell manufactures the car almost entirely in-house. While the team does not have a foundry or gear-cutting machines, it makes just about everything else. There is an extensive facility for making carbon-fiber composites and a pattern-making shop with a five-axis CNC machine.

This year's chassis was manufactured directly from Pro/ENGINEER geometry. Except for machining purposes, not a single drawing was produced. The CAD data was e-mailed to the shop staff, who then used it to create the toolpaths for the CNC machine. The ability to do this saved several weeks, according to Sean Briscall, a Tyrrell design engineer who worked on the chassis.

"Producing drawings of chassis components wouldn't have taken very long," Briscall explains. "But this approach really cut machining time. In the past, we hand-made the chassis pattern in-house, and the process took several weeks. This year, we sent the data on a Friday, and the pattern was done the next week."

Just-In-Time Results

One aspect of using computers for design and manufacturing just about sends Postlethwaite into coronary arrest. Just one week before the 026 was to be introduced to the public, there was literally nothing in the assembly bay. "It's not like the old days where the car sits on the workshop floor being built for three or four months. It all comes together at the last minute." But while the just-in-time process is nerve-wracking, it works. All the parts came together perfectly, the result of being pre-assembled in software and accurately machined from the CAD data.

The 1998 season was the 31^st for the Tyrrell Racing Organization. The team's proud heritage has included three World Drivers' Championships, two World Constructors' titles, and the 1987 Drivers' and Constructors' Championships for cars with naturally aspirated (non-turbocharged) engines. Its most famous driver, Jackie Stewart, won three Formula One Drivers' Championships. The team's score card currently stands at 33 Grand Prix wins. 1998 was the Tyrrell Racing Organization's final year in Formula One, since the team will be absorbed into the newly formed British American Racing team in 1999. The team will have a new name, but its design and manufacturing process won't change. It's a proven winner.

For more information, contact:

Parametric Technology Corp., PO Box 2995, Woburn, MA 01888-1795. 617-398-5234. Circle 405.

Tyrrell, Long Reach, Ockham, Woking, Surrey, England GU23 6PE. 01483 284955
Circle 406.

Michelin Chooses CATIA
Version 5 to Design, Simulate and Manufacture Tires

Michelin has chosen CATIA Solutions Version 5 as a strategic solution to design, simulate and manufacture its tires. Michelin will soon be using this CAD/CAM/CAE platform to develop and integrate specific applications. CATIA Version 5 will be used worldwide on all Michelin products for cars, vans, agricultural vehicles, trucks, construction equipment, aircraft and two-wheel vehicles.

Michelin is one of the earliest companies announcing the use of CATIA Version 5, which was officially previewed by IBM and Dassault Systemes in March, 1998. The software offers users a choice of native Windows NT or UNIX environments, and is fully interoperable with and complements the existing product portfolio of CATIA Version 4. The new product suite will be the first major CAD/CAM/CAE system to fully use next generation technologies and industry standards such as C++, Object Oriented Programming, STEP, OpenGL, Java, OLE and CORBA. It will run on UNIX hardware platforms supported by IBM, Hewlett Packard, Silicon Graphics and Sun and on Windows NT platforms (Intel and Digital Equipment/Alpha based).

Michelin, IBM and Dassault Systems are developing CAx solutions based on CATIA Version 5, following the re-engineering of design and manufacturing processes used for tires and molds. Project teams are working to specify requirements and ensure optimal transition of current applications and existing data to the CATIA environment.

For more information, contact:

Michelin, 46 avenue de Breteuil, 75324 Paris cedex. 33-4-7332-1497. Circle 407.

IBM Corporation, North America, 1507 LBJ Freeway, Dallas, TX 75234. 1-800-395-3339. Circle 408.

Originally published in the January 1999 issue of Medical Equipment Designer.
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