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Machine Design

Software helps extend X-prize winning concept car

Siemens PLM Software

Sportscar-builder Edison2 used 3D CAD software to help it design a concept car that won the $5 million mainstream class in Progressive Insurance’s 100-mpg Automotive X Prize competition.

With the X Prize competition over, the company is using the lessons it learned to create a fuel-efficient, next-generation car it hopes will eventually go into production.

The 830-lb concept car can carry four passengers and cargo. Edison2 designed components for simplicity, strength, and low weight. For example, brake calipers usually weigh several pounds. Those on the concept car are less than a pound. And the lug nuts weigh only 0.2 oz, as compared to 1 oz for conventional nuts.

The car has a superlow coefficient of drag. At GM’s Chelsea Proving Grounds, the car had the best results ever recorded for a coast-down test, which is a way of evaluating drag and includes rolling resistance. The car’s fuel-mileage ratings, as determined by the X Prize Foundation and confirmed by Argonne National Labs using standard EPA testing protocols, are 129.6 MPGe on the highway and 110.8 MPGe in combined city and highway driving. The vehicle also has the lowest greenhouse-gas emissions (82.6 gm CO2/mile) of all contest entries, including electric and hybrid vehicles.

Edison2 expects to equal these results in its follow-on design. Called the Very Light Car, it is more consumer friendly than the concept car. For example, it sports larger doors and wheels, and more-powerful brakes. According to designers, modifications have gone faster than expected because the company has since upgraded to Solid Edge with synchronous technology, provided by Siemens PLM Software, Plano, Tex., which combines constraint-driven techniques with direct modeling that synchronizes geometry and design rules to provide a history-free, feature-based 3D CAD package.

The original Solid Edge models the designers are now modifying were created using the history-based approach. But this poses no interoperability problems. “Synchronous technology lets Solid Edge work with history-based models, no matter what CAD software was used,” says Director of R&D at Edison2, Brad Jaeger. As an example of how the team used synchronous technology, Jaeger points to changes they made to the brakes. “We wanted to make the rotor bigger and thicker,” he says. “We created a few live sections, which let users edit 3D models using 2D cross sections, place critical dimensions, and modify the part. All of this took about 2 minutes. Because the rotor is part of an interlinked assembly, associated components updated automatically. Without synchronous technology, we might have had to redesign the entire brake system.”

Synchronous technology was also used to strengthen the frame. “To build a car that meets, passes, and exceeds FMVSS crash-test standards, we’re developing a frame that absorbs more energy,” says Jaeger. “This is an iterative process and synchronous technology lets us make changes quickly and easily. We can then simulate the updated design using nonlinear finite-element analysis and make additional design changes based on those results.”

© 2011 Penton Media, Inc.

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